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The new coordination modes of bis(1,2,4-diazaphospholyl)methane
Polyhedron 119 (2016) 325–334
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The new coordination modes of bis(1,2,4-diazaphospholyl)methane Martin Mlatecˇek, Libor Dostál, Zdenˇka Ru˚zˇicˇková, Milan Erben ⇑ Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 53210 Pardubice, Czech Republic
a r t i c l e
i n f o
Article history: Received 1 August 2016 Accepted 4 September 2016 Available online 22 September 2016 Keywords: Diazaphosphole Transition metal complex NMR spectroscopy XRD analysis Phosphorus donor
a b s t r a c t The coordination behavior of the polydentate ligand bis(1,2,4-diazaphospholyl)methane (Bdapm) toward group 6 and group 10 metals has been studied. From the reaction with [W(CO)5(NMe3)], three species with different coordination patterns were isolated and characterized. Thus we proved that the polydentate Bdapm ligand could serve as a terminal j-P, bridging l2-P,P and chelating j2-N,N ligand in the complexes [W(CO)5(j-P-Bdapm)], {[W(CO)5]2(l2-P,P-Bdapm)} and {W(CO)4(j2-N,N-Bdapm)}, respectively. The j2-N,N chelate bonding mode has been also detected in the molybdenum(II) and nickel(II) derivatives [Mo(g3-C3H5)(j2-N,N-Bdapm)(CO)2Cl] and [Ni(acac)2(j2-N,N-Bdapm)]. The reaction of Bdapm with [M(C,N-Ar)Cl] fragment sources [Ar = 2-(N,N-dimethylaminomethyl)phenyl or 2-(N,N-dimethylaminomethyl)ferrocenyl, M = Pd or Pt] gives unstable j-P bonded species, which are readily converted to the multimetallic complexes {[M(C,N-Ar)Cl]2-l2-P,P-Bdapm}. The different coordination modes of the Bdamp ligand in such compounds were easily distinguished by multinuclear NMR spectroscopy. The crystal structures of five transition metal complexes demonstrating the coordination variability of Bdapm are reported. On inspection of the acquired data it is evident that the stability of the studied species increases in the order of the binding modes j-P < l2-P,P < j2-N,N. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction The first routes to substituted 1,2,4-diazaphospholes (dap), reported in 1984, were based on the [3+2] cycloaddition of phosphaalkynes or their precursors to diazoalkanes [1,2]. At the same time Schmidpeter and Willhalm presented the reaction of the Vilsmeier reagent, P(SiMe3)3, and hydrazine which yielded the unsubstituted 1H-1,2,4-diazaphosphole [3]. After more than 30 years, dap chemistry has undergone a renaissance due to large-scale availability of P(SiMe3)3 [4,5], a versatile source of phosphorus in heterocycle syntheses, and due to the development of a general route to various 1H-1,2,4-diazaphospholes [6]. As dap contains both hard (N) and soft (P) donor atoms, it is a unique representative of hybrid ligands. The first report dealing with dap coordination behavior described its reaction with group 6 carbonyl derivatives [7]. In the resulting adducts the dap ligand serves as a terminal j-P or bridging l2-N,P ligand, see Scheme 1A. The 1H-1,2,4-diazaphosphole molecule could be easily deprotonated to give stable heteroaromatic systems resembling the cyclopentadienyl ligand. The diazaphospholide anion shows multiple binding modes and various complexes with j-N, l2-N,N, g2-N,N and g5-bonded dap anions have been described (1B) [7–9]. ⇑ Corresponding author. Fax: +420 466037068. E-mail address: [email protected] (M. Erben). http://dx.doi.org/10.1016/j.poly.2016.09.026 0277-5387/Ó 2016 Elsevier Ltd. All rights reserved.
In particular cases the dap anion is able to enforce a very short metal–metal bond by l2-N,N coordination in paddlewheel shaped dibismuthanes [10]. Diazaphospholide complexes, where a fivemembered heterocycle connects two metals in the l2-g2,g5 or l2-g2,g4 mode, have been reported very recently [9,11,12]. The dap ligand and its derivatives undergo a two-electron reduction giving a stable radical dianion which, after coordination toward two potassium cations, yields an unusual ‘‘inverse sandwich” structure (1C) [13]. Recent studies demonstrated that the dap anion is a useful synthon for building larger molecules behaving as polydentate ligands. Those comprise dap-substituted pyridines or pyrazines, [14] bis(diazaphospholyl)methanes (Bdapm) [15] and tris(diazaphospholyl)borates (PhTdap) [16]. These ligands are able to coordinate transition and non-transition metals, but exclusively as nitrogen donors (1D). It should be noted that from more than fifty structures deposited in the Cambridge Structural Database only in a single molecule, {[Cr(CO)5]2(l2-N,P-C2H3N2P)}, has a dative phosphorus–metal bond been detected [7]. Our previous work demonstrated that the phosphorus atom of the aromatic diazaphospholide ring in the PhTdap ligand is inert and does not tend to coordinate transition metals. However in the case of the complex [Pd(C,N-dmba)(j2-N,N-PhTdap)] [dmba = 2-(N,Ndimethylaminomethyl)phenyl], bearing a pendant dap ring with significant diene character, interaction with nickel(0) species was detected by 31P CP/MAS NMR [16]. On inspection of these data, it
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Scheme 1. Coordination modes known for dap based ligands: (A) neutral 1H-1,2,4-diazaphosphole, (B) diazaphospholide anion, (C) diazaphospholide radical dianion, (D) molecules bearing more than one dap ring (X = N or CH).
is evident that anionic diazaphospholides prefer bonding via the nitrogen atoms or through the heteroaromatic p-system, whereas the corresponding neutral heterocyclic diene could also serve as a phosphorus donor toward certain transition metals. Therefore, we set to study the coordination properties of the neutral Bdapm ligand, with the view to prepare metal complexes in which the dap ring is bonded via the phosphorus atom. Herein we report the synthesis, spectroscopic and structural characterization of group 6 and group 10 metal species coordinated with the Bdapm ligand.
(CO)5W P
N
N
N
N
+
P
(CO)5W P
N
N
N
N
P W(CO)5
2
1 a
P
N
N
N
N
Bdapm
b
P c
2. Results and discussion Pure Bdapm was prepared in high yield from 1H-1,2,4-k3diazaphosphole and dichloromethane following the procedure known for the synthesis of bis(pyrazolyl)methane [17]. The melting point and NMR spectra are identical to those reported previously [15]. Its characteristic IR and Raman bands are due to aromatic (strong band at 3064 cm1) and aliphatic (medium band at 2971 cm1) CH stretching modes. The most intense Raman absorption at 901 cm1 (IR: 896 cm1) was assigned to an out-of-plane CH deformation, a band typical for the presence of an isolated CH moiety in various heterocycles and polysubstituted benzenes [18]. The electronic spectrum in the UV–Vis region showed two bands at 258 and 228 nm, attributable to p–p⁄ transitions of the dap rings. The reaction of Bdapm with [W(CO)5(NMe3)] gives a mixture of products separable by column chromatography, see Scheme 2. The major product (70%) has been identified as the complex {[W(CO)5]2(l2-P,P-Bdapm)} (2) with the bridging ligand coordinated toward two W(CO)5 fragments via phosphorus atoms. The second compound (10%) obtained from this reaction was
P
N
N
N
N
OC
P
W CO
P
Cl
N
N
N
N Mo
3
CO CO
CO
OC
P
4
Scheme 2. The preparation of group 6 compounds. (a) [W(CO)5(NMe3)], (b) [W(CO)4(1,5-cod)], (c) [Mo(g3-C3H5)(MeCN)2(CO)2Cl].
[W(CO)5(j-P-Bdapm)] (1), containing one P-bound W(CO)5 group. We have also isolated small amounts (<2%) of a third complex, {W(CO)4(j2-N,N-Bdapm)} (3), where Bdapm acts as an N,N-chelator. The yield of each complex could be modified by the reaction conditions. Using hexane at ambient temperature and a 1:1 ligand-to-metal stoichiometry affords 1 in yields up to 60%, whereas the reaction in boiling MeCN almost exclusively gives complex 3. Chelate 3 is also accessible by the reaction of Bdapm with [W(CO)4(1,5-cod)]. Both 1 and 2 are solids dissolvable in
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CH2Cl2, THF, toluene and hot hexane, whereas 3 is only sparingly soluble in polar solvents such as acetone or MeCN. Tungsten compounds 1–3 are stable toward air in the solid state, but their solutions slowly decompose to give dark suspensions. An entirely insoluble, paramagnetic blue solid (probably mixed tungsten oxides) and a solution of Bdapm have been separated from these suspensions by filtration. Prolonged heating of 1 in the solution gives the free ligand and bimetallic complex 2. In hot MeCN, fast conversion of both 1 and 2 into the N,N-chelated species 3 takes place. The 1H and 13C NMR spectra of 1 show two resonance sets attributable to two inequivalent diazaphospholyl rings. According to the asymmetric structure of 1, two singlets were found in the 31P NMR spectrum at 100.4 and 80.7 ppm, the latter being flanked with 183W satellites (1JWP = 254.1 Hz). The axial carbonyl group of W(CO)5 shows a significantly larger coupling with the phosphorus donor atom (2JPC = 36.1 Hz) than the equatorial ones (2JPC = 8.7 Hz) due to the trans-effect. The coordinated dap ring in the molecule of 1 could be easily distinguished by lower the 1JPC coupling constants (26.5 and 5.4 Hz) from the uncoordinated one (65.4 and 56.4 Hz); cf. free Bdapm: 64.0 and 56.8 Hz. The large difference in 1JPC suggests a significant change of P–C bond orders after dap coordination toward the metal. The 31P NMR spectrum of 2 shows a single resonance at 95.2 ppm flanked with satellites due to coupling with the 183W nuclei (1JWP = 256.2 Hz). Two doublets of W (CO)5 carbonyl groups (2JPC = 32.9 and 8.9 Hz for axial and equatorial CO, respectively) were found in the 13C NMR spectrum. Only one set of signals was observed in the 1H and 13C NMR spectra for both dap rings in the 2, affirming their equivalency. Similarly as in 1, the interaction of the tungsten fragment with the phosphorus atom causes a significant decrease in the 1JPC coupling constants to 27.9 and 5.7 Hz, respectively. The N,N-chelate complex 3 gives one set of 1H and 13C NMR resonances accompanied with a 31P NMR singlet at 92.7 ppm. The observed 1JPC coupling constants of 61.9 and 65.3 Hz prove that both P–C bond orders are very close and similar to those in the free Bdapm ligand. Inequivalent protons of the methylene bridge having an AX spin pattern (2JHH = 13.0 Hz) validate the rigid bonding of the Bdapm chelator toward the tungsten fragment. Four mCO bands in both IR and Raman spectra in the region 1795–2011 cm1 are characteristic for the cis-chelated W(CO)4 moiety [19]. The carbonyl stretching frequencies in 3 are slightly higher than those reported for the corresponding bis(pyrazolyl)methane (Bpm) complex {W(CO)4(j2-N, N-Bpm)} [20]. The crystal structures of 1 and 2 are fully in agreement with the spectroscopic data, see Figs. 1 and 2, respectively. Both molecules contain a pseudooctahedral W(CO)5 fragment bonded to the phosphorus atom of the dap ring. The heterocyclic rings in both 1 and 2 are rotated in opposite directions around the methylene bridge, similarly to the free ligand. The observed W–P bond distances, 2.455(1)–2.460(2) Å, are close to the data reported for phosphinine or phosphole adducts with the W(CO)5 moiety [21]. The interaction of Bdapm with tungsten does not significantly affect the endocyclic bond distances of dap, but opens the C–P–C vertex angle to value 88.4(4)° in both 1 and 2 [cf. Bdapm: 85.0(2)°] [15]. The reaction of Bdapm with [Mo(g3-C3H5)(MeCN)2(CO)2Cl] gives the molybdenum(II) complex [Mo(g3-C3H5)(j2-N,NBdapm)(CO)2Cl] (4) as an orange solid which is nearly insoluble in chloroform and hydrocarbons, but fairly soluble in polar solvents. The 1H and 13C NMR spectra of 4, measured in CD3CN, show one set of resonances together with a single 31P NMR signal at d 95.6 ppm due to equivalent dap rings. The methylene bridge protons give a single 1H NMR peak at d 6.76 ppm; the allylic resonances are broadened. An acetone solution of 4 gives a complex NMR spectra indicating the presence of several species (31P NMR resonances at d 97.5, 95.2 and 92.9 ppm). The 1H NMR spectrum shows two AX spin systems (2JHH = 13.1 and 12.7 Hz, respectively)
327
of two molecules with an asymmetric CH2 bridge, together with a major singlet at d 6.59 ppm, corresponding to a species bearing a symmetric methylene group. Regarding the expected structure with a chiral molybdenum atom, four isomers of 4 are possible, see Scheme 3. Species A, B and C, possessing a methylene bridge with inequivalent protons, should give an AX spin pattern in the 1 H NMR spectrum, whereas structure D, with a mirror plane bisecting the CH2 bridge, should yield a single methylene resonance. However, IR and Raman spectra of 4 measured in various solvents invariably give two strong mCO bands, diagnostic of a cis-Mo(CO)2 unit and the presence of the trans-carbonyl isomer D as a major species is excluded. Previous studies showed that the fac-[Mo (g3-C3H5)(CO)2] moiety (isomers B and C) represents the most energetically favorable configuration, whereas the mer- arrangement (structure A) has not been detected in any species of this type [22,23]. We thus assume that 4 dissociates on dissolution to give the fluxional cationic moiety [Mo(g3-C3H5)(j2-N,N-Bdapm) (CO)2]+ possessing a symmetric CH2 bridge. In acetonitrile, the stability of this cation is significantly enhanced and hence it is the single species detected. Therefore, the complex NMR spectra of 4 obtained in acetone could be due to the presence of an equilibrium between a fluxional cation and isomeric species B and C, see Scheme 4. This hypothesis is further supported by the fact that addition of AgOTf to an acetone solution of 4 leads to both AX spin signals vanishing, along with an increase of the single methylene resonance at d 6.59 ppm and only one peak at d 94.5 ppm remains in the 31P NMR spectrum (see Experimental section). The solvated cationic moiety present in acetonitrile solution did not change its 1 H, 13C and 31P NMR parameters, even after the addition of AgOTf. The stereochemical non-rigidity of the corresponding molybdenum(II) complexes [Mo(g3-C3H5)(CO)2(LL)X], where X is a halide and (LL) is phen, bipy or dppe, has been described in detail by Azevedo et al. [24]. The vibrational spectrum of 4 in the solid state shows carbonyl stretching bands at 1840 and 1948 cm1 (Ra: 1841 and 1951 cm1), which are higher than in the analogous complex [Mo(g3-C3H5)(j2-N,N-Bpm)(CO)2Cl] (IR: 1817/1921 cm1) [25]. Thus, the N,N-bonded Bdapm chelator renders lower electron density to the central metal atom than the Bpm ligand. X-ray diffraction analysis revealed that 4 crystallizes as isomer B, see Fig. 3. Assuming that the allyl group occupies one site, the Mo atom is pseudo-octahedrally coordinated. The allyl fragment adopts an exo conformation with respect to the Mo(CO)2 moiety, with carbonyl carbon atoms C9 and C10 eclipsing the terminal allyl carbons C8 and C6, respectively. The Mo1–N1 bond distance is longer than that of Mo1–N3 due to the trans-effect of the carbonyl ligand. Intramolecular bond distances and angles are equal within experimental errors to data reported for related complexes with the Bpm ligand [25]. The j2-N,N-coordination of the Bdapm ligand toward the molybdenum(II) center causes a slight elongation (ca 0.02 Å) of the endocyclic bonds, whereas the C–P–C vertex angle [85.7(3)°] remains almost unchanged. This observation could be attributed to larger delocalization of the heteroaromatic p-electrons in the j-N coordinated dap ring as compared to the free or j-P bonded one. We have reported similar effects in the scorpionate complex [Pd(C,N-dmba)(j2-N,N-PhTdap)] [16]. In the next part of the study, we have examined the coordinating behavior of the Bdapm ligand toward nickel(II), palladium(II) and platinum(II) species, see Scheme 5. On the addition of Bdapm to a benzene solution of Ni(acac)2, a precipitate appears which, after crystallization from acetone, gives large blue crystals characterized as [Ni(acac)2(j2-N,N-Bdapm)] (5). Complex 5 is paramagnetic at ambient temperature with a leff value of 3.20 B.M., which is typical for octahedral nickel(II) species having an electronic spin S = 1. A very broad 31P NMR resonance was found at d 232 ppm; neither 1H nor 13C NMR spectra were acquired due to significant line broadening. The IR spectrum contains strong bands
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N4 O3
C4
N3 C1
P2
C3
C8 O2
C5
N1
C7
P1 W1 N2
C2 C6
O1
C9 O4
C10
O5 Fig. 1. The ORTEP plot of 1 at 50% probability, showing the atom numbering scheme. Representative bond distances (Å) and angles (°): W1–P1 2.460(2), P1–C2 1.742(8), P1–C3 1.704(7), C2–N2 1.313(9), N2–N1 1.359(8), N1–C3 1.347(9), P2–C4 1.741(9), P2–C5 1.716(7), C4–N4 1.310(10), C5–N3 1.335(9), N3–N4 1.344(8), C2–P1–C3 88.5(3), C4–P2–C5 85.9(4), N1–C1–N3 111.7(6).
O4
O3
N2
C2
C9
C8 P1
N1
C6
C1
C3 C10
N3 C7
C5 N4
O8
O1
W1
O5
O2 P2
C13
C4 W2
O7
C12 C14 C11 O6
O9
C15 O10
Fig. 2. The ORTEP plot of 2 at 50% probability, showing the atom numbering scheme. The dichloromethane solvate molecule is omitted for clarity. Selected bond distances (Å) and angles (°): W1–P1 2.458(1), W2–P2 2.455(1), P1–C2 1.729(5), P1–C3 1.703(5), N1–C3 1.341(6), N1–N2 1.349(5), N2–C2 1.321(6), C2–P1–C3 88.4(2), C4–P2–C5 88.2(2), N1–C1–N2 111.5(3).
characteristic for the diketonate cycle at 1587 and 1514 cm1 (mC@O and mC@C combinations) [26]. A medium absorption found at 1709 cm1 is attributable to co-crystallized acetone. The electronic spectrum in the NIR-VIS region shows bands due to d–d transitions with wavelengths 1036, 765 and 606 nm, and extinc-
tion coefficients in the range 3.5 – 13.2 M1 cm1, close to the data reported for the corresponding [Ni(acac)2(2,20 -bipy)] complex [27]. In the solid state, molecule 5 shows a cis arrangement of both chelating diketonate and Bdapm ligands, yielding a distorted octahedral environment, see Fig. 4. The nickel cation is coordinated by
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Scheme 3. Possible isomers and diastereomers (denoted as A’and B’) of the complex 4, where R is an g3-bonded allyl group.
Scheme 4. Dynamic behavior of 4 in solution (R = g3-allyl, S = solvent molecule, X = chloride or triflate counterion).
four oxygen atoms of two acac moieties and two nitrogen atoms of the Bdapm ligand. The six-membered acetylacetonate rings are almost planar, whereas the N,N-chelate is deflected due to sp3 hybridization at the methylene bridge. Similarly as in 4, j2-N,Nbonding enlarges the internal bonds of the dap heterocycles; the observed C–P–C vertex angle is 86.2(1)°. A subsequent series of experiments were performed on platinum(II) complexes with a view to take advantage of the dipolar 195 Pt nucleus. Thus, we have followed the reaction between Bdapm and [Pt(C,N-dmba)Cl(dmso)] by 31P NMR spectroscopy. We found that the unstable complex [Pt(C,N-dmba)Cl(j-PBdapm)] (6a) is formed [signals in 31P NMR spectrum at d 99.1 and 91.4 ppm (1JPtP = 5029 Hz)] in the first instance, but it is subsequently converted into the bimetallic complex {[Pt(C,N-dmba) Cl]2(l2-P,P-Bdapm)} (6) [one resonance in the 31P NMR spectrum at d 90.1 ppm with 1JPtP of 5012 Hz] and the free ligand, regardless of the stoichiometry used. In the case of platinum(II) precursor sufficiency, the formation of 6 is a very fast and quantitative process. Once solid 6 precipitates from the reaction mixture, it is entirely insoluble in common NMR solvents and its characterization is incomplete. Nevertheless, the structures of 6a and 6 could be suggested from the 1H and 31P NMR spectra of the reaction mixtures. The presence of a single resonance in the 31P CP/MAS NMR spectrum of 6 flanked with 195Pt satellites (1JPtP = 4890 Hz) proved that both dap rings are coordinated toward the platinum center via the phosphorus atom. Using more soluble precursor [Pt(C,N-dmaf)Cl (dmso)], where dmaf is 2-(N,N-dimethylaminomethyl)ferrocenyl,
allowed us to isolate and fully characterize the tetrametallic complex {[Pt(C,N-dmaf)Cl]2(l2-P,P-Bdapm)} (7). Similarly as in the case of 6a, the intermediate [Pt(C,N-dmaf)Cl(j-P-Bdapm)] (7a) [signals in the 31P NMR spectrum at d 99.0 and 87.5 ppm (1JPtP = 5139 Hz)] was detected temporarily in the reaction mixture. The l2-P,P coordination mode in 7 has been unambiguously proved by only one set of 1H and 13C NMR signals, with low 1JPC coupling constants, and particularly by a single 31P NMR resonance at d 89.9 ppm coupled with the 195Pt isotope (1JPtP = 5143 Hz). The IR band at 1697 cm1 is due to the presence of co-crystallized acetone, while the [Fe(g5-C5H5)] moiety gives characteristic Raman lines at 3092 and 1106 cm1 (symmetric CH stretch and ring breathing, respectively) [28]. Two weak absorptions observed in the region 380–500 nm are typical for d–d electronic transitions of the ferrocenyl fragment [29]. The corresponding palladium(II) complex {[Pd(C,N-dmba) Cl]2(l2-P,P-Bdapm)} (8) has been isolated from the reaction of {[Pd(C,N-dmaf)Cl]2} with Bdapm. The unstable intermediate [Pd (C,N-dmaf)Cl(jj-P-Bdapm)] (8a) (31P NMR spectrum, d 99.1 and 91.4 ppm), was detected by 31P NMR spectroscopy, but the observed signals could not be reliably assigned to each dap ring as palladium does not possess isotopes providing notable coupling to the 31P nucleus. Pure 8 gives 1H and 13C NMR spectra very similar to the platinum(II) congener 7. The l2-P,P coordination of Bdapm is evidenced by one set of dap resonances and by low 1JPC coupling constants (32.8 and 7.0 Hz, respectively). A single 31P NMR signal has been found at d 110.4 ppm, which is the highest
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bond distances are close to those in the free ligand; the C–P–C vertex angle is opened to a value of 88.0(5)°. We have also examined the reactions between 1 and {[Pd(C,N-dmaf)Cl]2} or [Pt(C,N-dmaf)Cl(dmso)], with a view to prepare asymmetric complexes bearing the Bdapm ligand coordinated by different metals. Unfortunately, only compounds 7 and 8 were detected as the main products in all runs. Similar experiments with the N,N-coordinated derivatives 3, 4 and 5 revealed that the phosphorus atoms of Bdapm in these complexes are inert and no interactions toward Pt(II) or Pd(II) ions were observed. 3. Concluding remarks In this paper we presented the coordination ability of the Bdapm ligand toward selected complexes of group 6 and 10 metals. The acquired data shown that this neutral ligand is able to serve as a j2-N,N ligand, giving very stable chelate complexes. In particular cases, the Bdapm ligand interacts with transition metals as a bidentate l2-P,P bridge or as a monodentate j-P donor. Complexes with j-P bonded metals easily undergo substitution or redistribution reactions, changing into more stable l2-P,P or j2-N,N species. Coordination of metals toward the Bdapm ligand through the phosphorus atom outstretches the endocyclic vertex C–P–C angle by ca 3°, which is accompanied by a significant change in the 1JPC coupling constants. In the case of the j2-N,N binding mode, the structural and spectroscopic changes are much lower. Thus the P-bounded ligand behaves as a phosphaalkene donor, whereas the Bdapm ligand in N-bounded chelate complexes more likely resembles heteroaromatic diazaphospholide species.
Fig. 3. The ORTEP plot of 4 at 50% probability, showing the numbering scheme. The chloroform solvate molecule is omitted for clarity. Selected bond distances (Å) and angles (°): Mo1–N1 2.281(3), Mo1–N3 2.239(3), Mo1–Cl1 2.548(1), Mo1–Cg1 2.040 (2), Mo1–C9 1.964(4), Mo1–C10 1.926(4), P1–C2 1.752(5), P1–C3 1.723(4), C2–N1 1.325(5), N1–N2 1.359(5), N2–C3 1.332(5), C2–P1–C3 85.8(2), C4–P2–C5 85.6(2), N1–C1–N3 110.2(3), N1-Mo1–N3 78.33(11).
4. Experimental value among of all the compounds included in this study. The electronic spectrum in the visible region shows ferrocenyl d–d bands at 418 and 489 nm. Crystallization from acetone yielded crystals suitable for X-ray diffraction analysis, see Fig. 5. In the solid state, complex 8 is a symmetric species with a mirror plane bisecting the molecule at the methylene carbon atom C14. In contrast to tungsten compounds 1 and 2, the diazaphosphole rings in 8 are in an eclipsed arrangement with an intramolecular N3. . .N3a distance of 3.392(12) Å. The palladium center possesses a square planar coordination environment with the sum of the valence angles around the palladium atom close to 360°. The phosphorus atom of the Bdapm ligand is coordinated in a trans-position with respect to the nitrogen donor atom of the dmaf ligand. The endocyclic dap
4.1. Materials All preparative reactions and manipulations were routinely carried out under an inert atmosphere of argon using Schlenk techniques. Solvents were dried and deoxygenated in a PureSolv MD 7 solvent purification system. Metal carbonyls and [Ni(acac)2]3 were obtained from Sigma–Aldrich and used after vacuum sublimation. The starting complexes [W(CO)5(NMe3)] [30], [Mo(g3-C3H5)(MeCN)2(CO)2Cl] [31], [Pt(C,N-dmba)Cl(dmso)], [Pt(C,N-dmaf)Cl(dmso)] [32], [Pd(C,N-dmaf)Cl]2 [33] and 1H-1,2,4diazaphosphole [3,16] were prepared by procedures reported elsewhere.
c
P
b
N
N
N
N Ni
O O
P
d
M Cl
M Fe
Fe
P
Cl
7a (M = Pt) 8a (M = Pd)
a
P
N N
N N
(CH3)2N
N(CH3)2
(CH3)2N Bdapm
N N
N N
P
M Cl
Fe
7 (M = Pt) 8 (M = Pd)
P O
P
N
N
N
N
Me2N P
Pt Cl
O 6a
d
NMe2 Pt Cl
P
N
N
N
N
Me2N P
Pt Cl
6
5 Scheme 5. Syntheses of group 10 complexes. (a) [Ni(acac)2]3, (b) [Pt(C,N-dmba)Cl(dmso)], (c) [Pt(C,N-dmaf)Cl(dmso)] or [Pd(C,N-dmaf)Cl]2, (d) ligand redistribution or excess of organometallic precursor.
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4.2. Spectroscopic measurements
Fig. 4. The ORTEP plot of 5 drawn at the 50% probability level and showing the atom numbering scheme. Hydrogen atoms and a molecule of acetone are omitted for clarity. Selected bond distances (Å) and angles (°): Ni1–N2 2.125(1), Ni1–N2 2.126(2), P1–C2 1.753(2), P1–C3 1.719(3), C2–N2 1.316(3), N1–N2 1.355(2), N1–C3 1.334(3), C2–P1–C3 86.2(2), C4–P2–C5 86.2(1), N1–C1–N3 110.7(2), N2–Ni1–N4 86.41(7).
The 1H, 13C{1H} and 31P{1H} NMR spectra were measured at 300 K on a Bruker Avance III 500 MHz instrument equipped with a Prodigy CryoProbe; the chemical shifts were referenced to external neat (CH3)4Si or H3PO4, respectively. The 31P CP/MAS NMR spectra were recorded at room temperature on a Bruker Ascend 500 spectrometer at a magnetic field of 11.746 T (31P resonance frequency of 202 MHz) with a 3.2 mm DVT CP/MAS probe (external reference NH4H2PO4). IR spectra were recorded on a Nicolet 6700 FTIR spectrometer using a single-bounce silicon ATR crystal. Raman spectra were recorded in the range 4000–100 cm1 with a Nicolet iS50 equipped with iS50 Raman module (excitation laser 1064 nm) or on a HoribaJobin Yvon (785 nm, samples 5 and 8). Electronic absorption spectra (200–1080 nm) were run on a BlackComet C-SR-100 concave grating spectrometer. The near infrared spectrum of 5 was obtained on a UV-3600 Shimadzu in the region 500–3500 nm. Elemental CHN analyses were obtained with a Fisions EA 1108 microanalyzer. Solid samples for elemental analyses were finely powdered and dried in a vacuum (102–103 Pa) at 50 °C for 12 h to remove residual or co-crystallized solvents. Melting points were determined in argon-sealed capillaries using a Stuart SMP-3 melting point apparatus and are uncorrected. The magnetic susceptibility of 5 was measured in the solid state at room temperature on an Evans susceptibility balance MSB-AUTO. Corrections due to diamagnetic contributions of the ligands were applied. 4.3. Crystal structure determination The X-ray data for crystals of 1, 2, 4, 5 and 8 were obtained at 150 K using an Oxford Cryostream low-temperature device on a
Fig. 5. The ORTEP plot of 8 at the 30% probability level and showing the atom numbering scheme. Hydrogen atoms and a molecule of acetone solvate are omitted for clarity; carbon atoms C7A–C13A represent one component of the disorder. The positions of carbon atoms generated by symmetry operations are not labeled. Selected bond distances (Å) and angles (°): Pd1–N1 2.134(9), Pd1–C1 1.983(10), Pd1–Cl1 2.385(4), Pd1–P1 2.192(3), P1–C15 1.723(11), P1–C16 1.706(9), C16–N2 1.333(12), N2–N3 1.358(11), N3–C15 1.296(14), C15–P1–C16 88.0(5), N2–C14–N2a 111.9(9).
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2
JPH = 42.5 Hz, 2H, CH). 13C NMR d, ppm: 70.0 (CH2), 158.1 (d, JPC = 56.8 Hz, CH), 164.9 (d, 1JPC = 64.0 Hz, CH). 31P{1H} NMR d, ppm: 100.7 (s). IR: identical to that in Ref. [15]. Raman (cm1): 3065vs, 3021w, 2971m (mCH), 901vs (cCH). UV–Vis [MeCN, kmax, nm, e, log(M1 cm1)]: 258 (3.93), 228 (3.90). Anal. Calc. for C5H6N4P2: C, 32.62; H, 3.29; N, 30.44. Found: C, 32.71; H, 3.26; N, 30.37%.
Nonius KappaCCD diffractometer with Mo Ka radiation (k = 0.71073 Å), a graphite monochromator and the / and v scan modes; relevant crystallographic data are listed in Table 1. Data reductions were performed with DENZO-SMN [34]. The absorption was corrected by integration methods [35]. The structures were solved by direct methods (Sir92) [36] and refined by full matrix least-squares based on F2 (SHELXL97) [37]. Hydrogen atoms were mostly localized in a difference Fourier map, however to ensure uniformity of the treatment of the crystals, all hydrogen atoms were recalculated into idealized positions (riding model) and assigned temperature factors, Hiso(H) = 1.2 Ueq (pivot atom) or of 1.5 Ueq (methyl). H atoms in methyl, methylene, methine and hydrogen atoms in aromatic rings were placed with C–H distances of 0.96, 0.97, 0.98 and 0.93 Å, respectively. Thermal ellipsoids of the chlorine atoms of the chloroform solvent in 4 were improved with the standard ISOR instruction implemented in the SHELXL97 software [37]. In the structure of 8, one cyclopentadienyl ring as well as the methyl groups of the dimethylaminomethyl moiety were disordered; the disorders were treated with the SAME instruction, allowing the whole group to be split into two positions with approximate occupancies of 7/3 and 6/4 respectively.
1
4.5. [W(j-P-Bdapm)(CO)5] (1) A mixture of Bdapm (313 mg, 1.7 mmol) and [W(CO)5(NMe3)] (575 mg, 1.5 mmol) was stirred in 100 ml of hexane at room temperature for 5 days. After filtration and solvent evaporation, the yellow residue was chromatographed on silica gel (3 30 cm, CH2Cl2 eluent). The first band, containing a small amount of 2, was discarded and the second band yielded, after evaporation and crystallization from hot hexane, 255 mg (33%) of colorless 1. Single-crystals suitable for XRD analysis were obtained on slow cooling of a saturated hexane solution. Mp.: 166 °C (dec). 1H NMR (CDCl3) d, ppm: 6.69 (s, 2H, CH2), 8.49 (d, 2JPH = 50.1 Hz, 1H, CH, coordinated ring), 8.61 (d, 2JPH = 36.7 Hz, 1H, CH, coordinated ring), 8.65 (d, 2JPH = 47.3 Hz, 1H, CH), 8.71 (d, 2JPH = 38.5 Hz, 1H, CH). 13C NMR d, ppm: 70.8 (CH2), 151.9 (d, 1JPC = 26.5 Hz, CH, coordinated ring), 158.4 (d, 1JPC = 56.4 Hz, CH), 159.5 (d, 1JPC = 5.4 Hz, CH, coordinated ring), 165.5 (d, 1JPC = 65.4 Hz, CH) 193.7 (d, 1JWC = 124.6 Hz, 2 JPC = 8.7 Hz, equatorial CO), 198.0 (d, 2JPC = 36.1 Hz, axial CO). 31P 1 { H} NMR d, ppm: 80.7 (s, 1P, 1JWP = 254.1 Hz), 100.4 (s, 1P). IR (cm1): 3111m, 3079m, 3056s, 2978w, 2965m (mCH), 2079s, 2002m, 1969w, 1907vs-br (mC„O), 924m (cCH), 901m (cCH). Raman (cm1): 3111m, 3081m, 3057s, 3038w, 2980s (mCH), 2084s, 1997vs, 1961m, 1919vs (mC„O), 926vs (cCH), 902m (cCH). UV–Vis [CH2Cl2, kmax, nm, e, log(M1 cm1)]: 358sh (3.36), 338 (3.48), 294 (3.75), 258sh (4.11), 234 (4.41). Anal. Calc. for C10H6N4O5P2W: C, 23.64; H, 1.19; N, 11.03. Found: C, 23.75; H, 1.24; N, 10.89%.
4.4. Bis(1,2,4-diazaphosphol-1-yl)methane (Bdapm) 4.50 g (52.3 mmol) of 1,2,4-diazaphosphole was dissolved in CH2Cl2 (150 ml) and to this solution fine powders of 5.00 g (89.1 mmol) KOH, 12.00 g (86.8 mmol), K2CO3 and 1.50 g (8.4 mmol) (CH3)4NHSO4 were added. After stirring for 48 h under reflux, the solution was filtered, the remaining solid washed with 3 50 ml of boiling CH2Cl2 and the combined extracts were evaporated in a vacuum. Large colorless crystals of Bdapm have been obtained by crystallization from boiling hexane on cooling to 20 °C (yield: 4.02 g, 82%). Mp.: 114 °C. 1H NMR (CDCl3) d, ppm: 6.71 (s, 2H, CH2), 8.69 (d, 2JPH = 51.0 Hz, 2H, CH), 8.80 (d,
Table 1 Crystallographic data and refinement details for 1, 2, 4, 5 and 8. Compound
1
2
4
5
8
Empirical formula MW Crystal system Space group
C10H6N4O5P2W 507.98 triclinic
C15H6N4O10P2W2CH2Cl2 916.80 triclinic
P1 6.678 (3) 9.4320 (13) 12.544 (6) 97.91 (3) 103.28 (5) 90.330 (15) 2 761.1 (5) 2.217 0.59 0.40 0.13 colorless, plate 7.83 476 8, 8; 12, 12; 16, 16 1.7–27.5 13 646 3464 (0.119) 3327 199 3.68/5.83
P1 10.7970 (14) 11.0730 (12) 11.686 (2) 87.069 (14) 68.674 (18) 87.148 (9) 2 1299.0 (4) 2.344 0.51 0.46 0.31 light yellow, block 9.23 848 14, 14; 14, 14; 15, 15 1.8–27.5 31 391 5952 (0.075) 5370 325 1.89/2.55
C10H11ClMoN4O2P2CHCl3 531.93 monoclinic P21/c
C15H20N4NiO4P2C3H6O 499.08 monoclinic P21/c
C31H38Cl2Fe2N6P2Pd2C3H6O 1010.09 orthorhombic Pnma
13.3290 (5) 16.2331 (17) 8.9380 (9) 90 75.763 (6) 90 4 1924.2 (3) 1.836 0.32 0.11 0.09 yellow, block 1.42 1048 17, 17; 18, 21; 11, 10 1.5–27.5 21 554 4342 (0.066) 3628 217 1.73/1.51
9.4320 (7) 11.8609 (8) 21.4591 (19) 90 97.390 (7) 90 4 2380.7 (3) 1.392 0.56 0.42 0.30 blue, block 0.98 1040 11, 12; 15, 14; 27, 24 1.9–27.4 19 463 5288 (0.043) 4485 271 0.30/0.49
13.4220 (7) 29.1920 (14) 9.812 (4) 90 90 90 4 3844.5 (16) 1.745 0.58 0.32 0.13 orange, block 1.919 2024 17, 17; 36, 37; 12, 12
0.050/0.139/1.07
0.025/0.068/1.18
0.040/0.106/1.08
0.032/0.085/1.13
0.099/0.241/1.25
a (Å) b (Å) c (Å) a (°) b (°) c (°) Z V (Å3) Dx (g cm3) Crystal size (mm) Color, crystal shape l (mm1) F(0 0 0) h; k; l range h range (°) Reflections measured Independent (Rint) a Observed [I > 2r(I)] Parameters refined Maximum/minimum Dq (e Å3) Rb/wRb/GOFc a b c
P P Rint = |F2o Fo,2mean|/ F2o. P P P P R(F) = ||Fo| |Fc||/ |Fo|for observed data; wR(F2) = [ (w(F2o F2c )2)/( w(F2o)2)]½ for all data. P GOF = [ (w(F2o F2c )2)/(Ndiffrs – Nparams)]½ for all data.
1.4–27.5 22 733 4456 (0.113) 3755 249 3.31/1.90
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4.6. {[W(CO)5]2(l2-P,P-Bdapm)} (2) Bdapm (202 mg, 1.1 mmol) and [W(CO)5(NMe3)] (841 mg, 2.2 mmol) were refluxed in 50 ml of THF for 24 h. The solvent was removed in vacuum and the residue was dissolved in CH2Cl2 (40 ml) and filtered. The filtrate was evaporated to dryness and chromatographed on silica gel (3 30 cm, CH2Cl2 eluent). The first band gave, after evaporation and crystallization from a CH2Cl2hexane mixture, 511 mg (56%) of light yellow 2. Single-crystals suitable for XRD analysis were obtained on cooling of a saturated CH2Cl2 solution to 20 °C. Mp.: 149 °C (dec.). 1H NMR (CDCl3) d, ppm: 6.66 (s, 2H, CH2), 8.64 (d, 2JPH = 50.1 Hz, 2H, CH), 8.73 (d, 2JPH = 36.5 Hz, 2H, CH). 13C NMR d, ppm: 71.3 (CH2), 152.1 (d, 1 JPC = 27.9 Hz, CH), 159.9 (d, 1JPC = 5.7 Hz, CH), 193.6 (d, 1JWC = 124.8 Hz, 2JPC = 9.0 Hz, equatorial CO), 197.8 (d, 1 JWC = 155.8 Hz, 2JPC = 32.3 Hz, axial CO). 31P{1H} NMR d, ppm: 82.9 (s, 1JWP = 256.6 Hz). IR (cm1): 3119m, 3104w, 3083m, 2987w (mCH), 2080m, 1990w, 1940m, 1898vs-br (mC„O), 934m (cCH). Raman (cm1): 3118m, 3083m, 2982m (mCH), 2080s, 1990vs, 1936s, 1915s (mC„O), 930s (cCH). UV–Vis [CH2Cl2, kmax, nm, e, log(M1 cm1)]: 360sh (4.23), 340 (4.34), 296 (4.51), 260sh (4.78), 236 (4.16). Anal. Calc. for C15H6N4O10P2W2: C, 21.66; H, 0.73; N, 6.74. Found: C, 21.92; H, 0.80; N, 6.67%. 4.7. [W(jj2-N,N-Bdapm)(CO)4] (3) Method A: A mixture of W(CO)6 (500 mg, 1.4 mmol) and Bdapm (262 mg, 1.4 mmol) in 50 of MeCN was refluxed for 48 h. The solvent was removed in vacuum and the residue was washed with hot hexane (2 20 ml), dissolved in acetone and filtered through an alumina bed. The yellow filtrate was concentrated in a vacuum and cooled to 20 °C, giving bright yellow microcrystalline 3 (415 mg, 61% yield). Method B: 364 mg (0.9 mmol) of [W(CO)4(1,5-cod)] and Bdapm (166 mg, 0.9 mmol) were refluxed in 50 ml of THF for 12 h. After the workup described above, a yellow powder of 3 was obtained (384 mg, 72%) Mp.: 178 °C (dec.). 1H NMR (acetone-d6) d, ppm: 7.02 (d, 2JHH = 13.0 Hz, 1H, CH2), 7.62 (d, 2JHH = 13.0 Hz, 1H, CH2), 9.34 (d, 2JPH = 43.6 Hz, 2H, CH), 9.50 (d, 2JPH = 37.3 Hz, 2H, CH). 13 C NMR d, ppm: 71.3 (CH2), 163.4 (d, 1JPC = 61.9 Hz, CH), 173.7 (d, 1JPC = 65.3 Hz, CH), CO carbons were not observed due to poor solubility. 31P{1H} NMR d, ppm: 92.7 (s). IR (cm1): 3101m, 3035m, 2957w (mCH), 2011s, 1897sh-m, 1860s, 1795vs (mC„O), 904m (cCH). Raman (cm1): 3102s, 3036m, 2959m, 2924m (mCH), 2012vs, 1906m, 1838vs, 1802s (mC„O), 906s (cCH). UV–Vis [CH2Cl2, kmax, nm, e, log(M1 cm1)]: 389sh (3.07), 341 (3.17), 295 (3.66), 251 (3.99), 234sh (3.92). Anal. Calc. for C9H6N4O4P2W: C, 22.52; H, 1.26; N, 11.67. Found: C, 22.65; H, 1.22; N, 11.49%. 4.8. [Mo(g3-C3H5)(j2-N,N-Bdapm)(CO)2Cl] (4) 373 mg (1.2 mmol) of [Mo(g3-C3H5)(MeCN)2(CO)2Cl] was dissolved in 50 ml of THF and 221 mg (1.2 mmol) of Bdapm was added. After refluxing the mixture for 24 h, the solvent was removed in a vacuum. The brown residue obtained was washed with hot hexane (3 20 ml), dissolved in hot CHCl3 (100 ml) and charcoal was added. After reducing the volume of the filtrate to one-third and cooling to 20 °C, yellow crystals of 4 were obtained (337 mg, 68%). XRD quality single-crystals were grown from a saturated CHCl3 solution on slow cooling to 4 °C. Mp.: 198 °C (dec.). 1 H NMR (CD3CN, cationic species [Mo(g3-C3H5)(j2-N,N-Bdapm) (CO)2]+) d, ppm: 1.10 (s-br, 2H, allyl, anti-CH2), 3.22 (s-br, 2H, allyl, syn-CH2), 3.69 (s-br, 1H, allyl, CH), 6.76 (s, 2H, CH2), 8.71 (d, 2 JPH = 47.8 Hz, 2H, CH), 9.02 (d, 2JPH = 39.6 Hz, 2H, CH). 13C NMR d, ppm: 55.9 (s-br, CH2, allyl), 70.8 (CH2, methylene bridge), 71.8 (s-br, CH, allyl), 160.1 (d, 1JPC = 55.6 Hz), 165.6 (d, 1JPC = 64.3 Hz),
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224.5 (s-br, CO). 31P{1H} NMR d, ppm: 95.6 (s). 1H NMR (4 after the addition of AgOTf in acetone-d6) d, ppm: 1.28 (s-br, 2H, allyl), 2.97 (s-br, 2H, allyl), 3.82 (s-br, 1H, allyl), 6.83 (s, 2H, CH2), 8.64 (d, 2JPH = 46.4 Hz, 2H, CH), 9.01 (d, 2JPH = 39.9 Hz, 2H, CH). 31P{1H} NMR d, ppm: 95.9 (s). IR (cm1): 3098m, 3090m, 3071s, 2996s, 2950w (mCH), 1947s, 1840vs (mC„O), 902m (cCH). Raman (cm1): 3099m, 3090s, 3074m, 3060m, 3049m, 2996vs, 2953m (mCH), 1957s, 1841vs (mC„O), 902vs (cCH). UV–Vis [MeCN, kmax, nm, e, log(M1.cm1)]: 414sh (2.71), 347 (3.14), 253 (4.36), 233 (4.40). Anal. Calc. for C10H11Cl1MoN4O2P2: C, 29.11; H, 2.69; N, 13.58. Found: C, 29.35; H, 2.59; N, 13.49%. 4.9. [Ni(acac)2(Bdapm)] (5) Anhydrous [Ni(acac)2]3 (620 mg, 0.8 mmol) was dissolved in benzene (50 ml) and Bdamp (441 mg, 2.4 mmol) was added with stirring. After heating to 80 °C for 12 h, the blue precipitate that formed was filtered, washed with hot hexane (3 10 ml) and dried in a vacuum. The solid was then dissolved in boiling acetone (40 ml), filtered and the light blue filtrate was concentrated to 15 ml and cooled to 20 °C for 2 days. Heating of the isolated large blue crystals to 50 °C in a high vacuum for 48 h yielded a blue powder of pure 5 (891 mg, 84%). Mp.: 182 °C. 31P{1H} NMR (acetone-d6) d, ppm: 232 br. leff = 3.20 ± 0.02 (B. M. at 293 K). IR (cm1): 3073s, 3024s, 2997m, 2983m, 2916m (mCH), 1709s (mC@O, acetone), 1587vs, 1514vs (mC@O + mC@C, acac), 899m (cCH). Raman (cm1): 3075s, 2916s-br (mCH), 1586w, 1514w (mC@O + mC@C, acac), 900vs (cCH). UV–Vis [MeCN, kmax, nm, e, log(M1 cm1)]: 1036 (1.12), 765 (0.55), 606 (1.11), 311sh (3.99), 297 (4.13), 258 (4.03), 228 (4.13). Anal. Calc. for C15H20N4NiO4P2: C, 40.85; H, 4.57; N, 12.70. Found: C, 41.13; H, 4.66; N, 12.59%. 4.10. {[Pt(C,N-dmba)Cl]2-l2-P,P-Bdapm} (6) A mixture of [Pt(C,N-dmba)Cl(dmso)] (84.2 mg, 190 l mol) and Bdapm (17.4 mg, 95 l mol) was stirred in 7 ml of CH2Cl2 for 30 min. A white precipitate was separated by centrifugation, washed with 2 1 ml CH2Cl2, then 2 1 ml of Et2O and dried in a vacuum. Yield 85.1 mg of 6 (97%). Mp.: 220 °C (dec.) 1H NMR (CD2Cl2) d, ppm: 2.98 (s, 3JPtH = 36.6 Hz, 6H, N(CH3)2), 4.09 (s, 3 JPtH = 41.7 Hz, 2H, CH2NMe2), 6.72 (s, 2H, CH2), 6.89–7.47 (m, 4H, Ph), 8.67–8.99 (m-br, 4H, dap). 31P{1H} NMR (CD2Cl2) d, ppm: 90.1 (s, 1JPtP = 5012 Hz). 31P-CP/MAS d, ppm: 86.9 (s, 1JPtP = 4890 Hz). Intermediate 6a, 31P NMR (CD2Cl2) d, ppm: 99.1 (s, 1P), 91.4 (s, 1P, 1JPtP = 5029 Hz). IR (cm1): 3070vs, 3001m, 2923m-br (mCH), 939m (cCH). Raman (cm1): 3071s, 3062m, 3051m, 3004m, 2990m, 2977m, 2926s-br (mCH), 938vvs (cCH). UV–Vis [CH2Cl2, kmax, nm, e, log(M1 cm1)]: 287 (4.50), 249 (4.50), 234 (4.52). Anal. Calc. for C23H30Cl2N6P2Pt2: C, 30.24; H, 1.01; N, 9.20. Found: C, 30.36; H, 1.10; N, 9.15%. 4.11. {[Pt(C,N-dmaf)Cl]2-l2-P,P-Bdapm} (7) 60.7 mg (110 l mol) of [Pt(C,N-dmaf)Cl(dmso)] and 10.1 mg (55 l mol) of Bdapm were dissolved in 5 ml of CH2Cl2 and stirred for 12 h. An orange precipitate was separated by centrifugation, washed with cold Et2O (3 1 ml) and dried in a vacuum. Crystallization from an acetone/Et2O mixture gave red tiny needles of pure 7 (yield 55.8 mg, 90%). Mp.: 265 °C (dec.). 1H NMR (CDCl3) d, ppm: 2.92 (s, 3JPtH = 25.4 Hz, 6H, N(CH3)2), 3.25 (s, 3JPtH = 29.5 Hz, 6H, N(CH3)2), 3.47 (d, 2JHH = 13.8 Hz, 2H, CH2NMe2), 3.87 (d, 2 JHH = 13.7 Hz, 2H, CH2NMe2), 4.02 (s, 2H, Cp’), 4.12 (s, 10H, Cp), 4.21 (s, 2H, Cp’), 4.27 (s, 2H, Cp’), 6.71 (s, 2H, CH2), 8.81 (d, 2 JHP = 46.9, 2H, CH), 9.03 (d, 2JHP = 31.8, 2H, CH). 13C NMR d, ppm: 52.5 (N(CH3)2), 52.7 (N(CH3)2), 62.7 (Cp’), 68.0 (Cp’), 69.0 (CH2NMe2), 70.0 (Cp), 71.2 (Cp’), 72.5 (CH2), 95.6 (Cp’-ipso),
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141.5 (d, 1JCP = 54.3 Hz, CH), 148.0 (d, 1JCP = 16.7 Hz, CH). 31P{1H} NMR (CD2Cl2) d, ppm: 89.9 (s, 1JPtP = 5143 Hz). Intermediate 7a, 31 P NMR (CD2Cl2) d, ppm: 99.0 (s, 1P), 87.5 (s, 1P, 1JPtP = 5139 Hz). IR (cm1): 3090s, 3002w, 2963m-br (mCH), 1697s (mC@O, acetone), 1103m (mC@C, Fc ring-breathing), 929m (cCH). Raman (cm1): 3092vs-br, 2985m, 2955m (mCH), 1105vvs (mC@C, Fc ring-breathing), 930s (cCH). UV–Vis [CH2Cl2, kmax, nm, e, log(M1 cm1)]: 498 (2.96), 373sh (3.41), 284 (4.43), 234 (4.54). Anal. Calc. for C31H38Cl2Fe2N6 P2Pt2: C, 32.97; H, 3.39; N, 7.44. Found: C, 33.22; H, 3.49; N, 7.35%. 4.12. {[Pd(C,N-dmaf)Cl]2-l2-P,P-Bdapm} (8) [Pd(C,N-dmaf)Cl]2 (154 mg, 0.2 mmol), Bdapm (36.8 mg, 0.2 mmol) and dichloromethane (20 ml) were refluxed for 12 h. The solvent was evaporated and the red solid obtained was washed with hot hexane (3 5 ml) and crystallized from acetone at 20 °C to give fine orange crystals of 8 (169 mg, 89% yield). Mp.: 201 °C (dec.). 1H NMR (CHCl3) d, ppm: 2.28 (s, 6H, acetone solvate), 2.84 (s, 6H, N(CH3)2), 3.12 (s, 6H, N(CH3)2), 3.36 (d, 2H, 2JHH = 14.0 Hz, CH2NMe2), 4.00 (d, 2H, 2JHH = 14.0 Hz, CH2NMe2), 4.04 (s, 2H, Cp’), 4.11 (s, 2H, Cp’), 4.15 (s, 10H, Cp), 4.19 (s, 2H, Cp’), 6.76 (s, 2H, CH2), 8.90 (d, 2H, 2JHP = 47.9, CH), 9.22 (d, 2H, 2JHP = 32.7, CH). 13 C NMR d, ppm: 51.8 (d, 3JCP = 2.9 Hz, N(CH3)2), 52.3 (d, 3JCP = 2.5 Hz, N(CH3)2), 62.7 (Cp’), 66.7 (Cp’), 67.0 (d, 3JCP = 4.7 Hz, CH2NMe2), 70.4 (Cp), 71.2 (CH2), 72.5 (Cp’), 96.0 (Cp’-ipso), 98.7 (d, 2JCP = 7.5 Hz, Cp’-ipso), 148.5 (d, 1JCP = 32.8 Hz, CH), 153.6 (d, 1 JCP = 7.0 Hz, CH). 31P{1H} NMR d, ppm: 110.4 (s). Intermediate 8a, 31P NMR (CH2Cl2/CDCl3) d, ppm: 101.2 (s, 1P), 107.8 (s, 1P). IR (cm1): 3089vs, 3040m, 2995m, 2891m-br (mCH), 1696s (mC@O, acetone), 1104m (mC@C, Fc ring-breathing), 924m (cCH). Raman (cm1): 3089m, 2983m, 2919m (mCH), 1696w (mC=O, acetone), 1104vvs (mC@C, Fc ring-breathing), 923s (cCH). UV–Vis [CH2Cl2, kmax, nm, e, log(M1 cm1)]: 489sh (3.22), 418 (3.46), 319sh (3.71), 269sh (4.33), 234 (4.57). Anal. Calc. for C31H38Cl2Fe2N6P2Pd2: C, 39.11; H, 4.02; N, 8.83. Found: C, 39.32; H, 4.12; N, 8.75%. Appendix A. Supplementary data CCDC 1496781–1496785 contains the supplementary crystallographic data for 4, 2, 5, 8 and 1, respectively. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected]. References [1] G. Maerkl, I. Troetsch, Angew. Chem. 96 (1984) 899.
[2] W. Roesch, M. Regitz, Angew. Chem. 96 (1984) 898. [3] A. Schmidpeter, A. Willhalm, Angew. Chem. 96 (1984) 901. [4] M. Rigo, J.A.W. Sklorz, N. Hatje, F. Noack, M. Weber, J. Wiecko, C. Muller, Dalton Trans. 45 (2016) 2218. [5] A.A. Prishchenko, M.V. Livantsov, O.P. Novikova, L.I. Livantsova, V.S. Petrosyan, Heteroat. Chem. 21 (2010) 441. [6] Q. Liu, J. Wu, J. Li, J. Wang, W. Zheng, H.W. Roesky, Phosphorus Sulfur 189 (2014) 1455. [7] L. Szarvas, Z. Bajko, S. Fusz, S. Burck, J. Daniels, M. Nieger, D. Gudat, Z. Anorg, Allg. Chem. 628 (2002) 2303. [8] W. Zheng, G. Zhang, K. Fan, Organometallics 25 (2006) 1548. [9] C. Pi, L. Wan, Y. Gu, W. Zheng, L. Weng, Z. Chen, L. Wu, Inorg. Chem. 47 (2008) 9739. [10] M. Zhao, L. Wang, P. Li, X. Zhang, Y. Yang, W. Zheng, Chem. Commun. 51 (2015) 16184. [11] Y. Wang, W. Guo, D. Liu, Y. Yang, W. Zheng, Dalton Trans. 45 (2016) 899. [12] D. Liu, Y. Wang, C. Pi, W. Zheng, Organometallics 33 (2014) 6013. [13] C. Pi, Y. Wang, W. Zheng, L. Wan, H. Wu, L. Weng, L. Wu, Q. Li, P.V.R. Schleyer, Angew. Chem. Int. Ed. 49 (2010) 1842. [14] M. Zhao, P. Li, X. Xie, J. Su, W. Zheng, Polyhedron 85 (2015) 302. [15] M. Zhao, W. Ma, X. Liu, W. Zheng, Inorg. Chim. Acta 437 (2015) 110. [16] M. Mlatecˇek, L. Dostál, Z. Ru˚zˇicˇková, J. Honzícˇek, J. Holubová, M. Erben, Dalton Trans. 44 (2015) 20242. [17] M.R. Churchill, D.G. Churchill, M.H.V. Huynh, K.J. Takeuchi, R.K. Castellano, D.L. Jameson, J. Chem. Crystallogr. 26 (1996) 93. [18] G. Socrates, Infrared and Raman Characteristic Group Frequencies: Tables and Charts, Wiley, 2004. [19] G. Gioia Lobbia, F. Bonati, J. Organomet. Chem. 366 (1989) 121. [20] S. Kom-Bei, L. Kuen-Song, W. Yu, C. Ming-Chu, L. Gene-Hsiang, J. Organomet. Chem. 453 (1993) 201. [21] C.R. Groom, I.J. Bruno, M.P. Lightfoot, S.C. Ward, Acta Crystallogr. B 72 (2016) 171. [22] M.D. Curtis, O. Eisenstein, Organometallics 3 (1984) 887. [23] P. Espinet, R. Hernando, G. Iturbe, F. Villafañe, A.G. Orpen, I. Pascual, Eur. J. Inorg. Chem. 2000 (2000) 1031. [24] J.R. Ascenso, C.G. de Azevedo, M.J. Calhorda, M.A.A.F. de, C.T. Carrondo, P. Costa, A.R. Dias, M.G.B. Drew, V. Félix, A.M. Galvão, C.C. Romão, J. Organomet. Chem. 632 (2001) 197. [25] I. Honzícˇková, J. Honzícˇek, J. Vinklárek, Z. Padeˇlková, Polyhedron 81 (2014) 364. [26] K. Nakamoto, Applications in Inorganic Chemistry, Infrared and Raman Spectra of Inorganic and Coordination Compounds, John Wiley & Sons Inc, 2008, p. 149. [27] J.T. Hashagen, J.P. Fackler, J. Am. Chem. Soc. 87 (1965) 2821. ˇ ernošek, M. Erben, J. Vinklárek, I. Pavlík, Appl. [28] M. Pavlišta, R. Bína, Z. C Organomet. Chem. 19 (2005) 90. [29] P.R.R. Ranatunge-Bandarage, B.H. Robinson, J. Simpson, Organometallics 13 (1994) 500. [30] S.L. Matthews, D.M. Heinekey, J. Am. Chem. Soc. 128 (2006) 2615. [31] J.W. Faller, C.-C. Chen, M.J. Mattina, A. Jakubowski, J. Organomet. Chem. 52 (1973) 361. [32] M.D. Meijer, A.W. Kleij, B.S. Williams, D. Ellis, M. Lutz, A.L. Spek, G.P.M. van Klink, G. van Koten, Organometallics 21 (2002) 264. [33] C. Lopez, R. Bosque, X. Solans, M. Font-Bardia, D. Tramuns, G. Fern, J. Silver, J. Chem. Soc., Dalton Trans. (1994) 3039. [34] Z. Otwinowski, W. Minor, Method. Enzymol. (1997) 307. [35] P. Coppens, in: F.R. Ahmed, C.P. Hall, C.P. Huber (Eds.), Crystallographic Computing, Munksgaard, Copenhagen, 1970, p. 255. [36] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, J. Appl. Crystallogr. 27 (1994) 1045. [37] G.M. Sheldrick, SHELXL-97 Program for the Refinement of Crystal Structures, University of Goettingen, Germany, 2008.
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The new coordination modes of bis(1,2,4-diazaphospholyl)methane Martin Mlatecˇek, Libor Dostál, Zdenˇka Ru˚zˇicˇková, Milan Erben ⇑ Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 53210 Pardubice, Czech Republic
a r t i c l e
i n f o
Article history: Received 1 August 2016 Accepted 4 September 2016 Available online 22 September 2016 Keywords: Diazaphosphole Transition metal complex NMR spectroscopy XRD analysis Phosphorus donor
a b s t r a c t The coordination behavior of the polydentate ligand bis(1,2,4-diazaphospholyl)methane (Bdapm) toward group 6 and group 10 metals has been studied. From the reaction with [W(CO)5(NMe3)], three species with different coordination patterns were isolated and characterized. Thus we proved that the polydentate Bdapm ligand could serve as a terminal j-P, bridging l2-P,P and chelating j2-N,N ligand in the complexes [W(CO)5(j-P-Bdapm)], {[W(CO)5]2(l2-P,P-Bdapm)} and {W(CO)4(j2-N,N-Bdapm)}, respectively. The j2-N,N chelate bonding mode has been also detected in the molybdenum(II) and nickel(II) derivatives [Mo(g3-C3H5)(j2-N,N-Bdapm)(CO)2Cl] and [Ni(acac)2(j2-N,N-Bdapm)]. The reaction of Bdapm with [M(C,N-Ar)Cl] fragment sources [Ar = 2-(N,N-dimethylaminomethyl)phenyl or 2-(N,N-dimethylaminomethyl)ferrocenyl, M = Pd or Pt] gives unstable j-P bonded species, which are readily converted to the multimetallic complexes {[M(C,N-Ar)Cl]2-l2-P,P-Bdapm}. The different coordination modes of the Bdamp ligand in such compounds were easily distinguished by multinuclear NMR spectroscopy. The crystal structures of five transition metal complexes demonstrating the coordination variability of Bdapm are reported. On inspection of the acquired data it is evident that the stability of the studied species increases in the order of the binding modes j-P < l2-P,P < j2-N,N. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction The first routes to substituted 1,2,4-diazaphospholes (dap), reported in 1984, were based on the [3+2] cycloaddition of phosphaalkynes or their precursors to diazoalkanes [1,2]. At the same time Schmidpeter and Willhalm presented the reaction of the Vilsmeier reagent, P(SiMe3)3, and hydrazine which yielded the unsubstituted 1H-1,2,4-diazaphosphole [3]. After more than 30 years, dap chemistry has undergone a renaissance due to large-scale availability of P(SiMe3)3 [4,5], a versatile source of phosphorus in heterocycle syntheses, and due to the development of a general route to various 1H-1,2,4-diazaphospholes [6]. As dap contains both hard (N) and soft (P) donor atoms, it is a unique representative of hybrid ligands. The first report dealing with dap coordination behavior described its reaction with group 6 carbonyl derivatives [7]. In the resulting adducts the dap ligand serves as a terminal j-P or bridging l2-N,P ligand, see Scheme 1A. The 1H-1,2,4-diazaphosphole molecule could be easily deprotonated to give stable heteroaromatic systems resembling the cyclopentadienyl ligand. The diazaphospholide anion shows multiple binding modes and various complexes with j-N, l2-N,N, g2-N,N and g5-bonded dap anions have been described (1B) [7–9]. ⇑ Corresponding author. Fax: +420 466037068. E-mail address: [email protected] (M. Erben). http://dx.doi.org/10.1016/j.poly.2016.09.026 0277-5387/Ó 2016 Elsevier Ltd. All rights reserved.
In particular cases the dap anion is able to enforce a very short metal–metal bond by l2-N,N coordination in paddlewheel shaped dibismuthanes [10]. Diazaphospholide complexes, where a fivemembered heterocycle connects two metals in the l2-g2,g5 or l2-g2,g4 mode, have been reported very recently [9,11,12]. The dap ligand and its derivatives undergo a two-electron reduction giving a stable radical dianion which, after coordination toward two potassium cations, yields an unusual ‘‘inverse sandwich” structure (1C) [13]. Recent studies demonstrated that the dap anion is a useful synthon for building larger molecules behaving as polydentate ligands. Those comprise dap-substituted pyridines or pyrazines, [14] bis(diazaphospholyl)methanes (Bdapm) [15] and tris(diazaphospholyl)borates (PhTdap) [16]. These ligands are able to coordinate transition and non-transition metals, but exclusively as nitrogen donors (1D). It should be noted that from more than fifty structures deposited in the Cambridge Structural Database only in a single molecule, {[Cr(CO)5]2(l2-N,P-C2H3N2P)}, has a dative phosphorus–metal bond been detected [7]. Our previous work demonstrated that the phosphorus atom of the aromatic diazaphospholide ring in the PhTdap ligand is inert and does not tend to coordinate transition metals. However in the case of the complex [Pd(C,N-dmba)(j2-N,N-PhTdap)] [dmba = 2-(N,Ndimethylaminomethyl)phenyl], bearing a pendant dap ring with significant diene character, interaction with nickel(0) species was detected by 31P CP/MAS NMR [16]. On inspection of these data, it
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Scheme 1. Coordination modes known for dap based ligands: (A) neutral 1H-1,2,4-diazaphosphole, (B) diazaphospholide anion, (C) diazaphospholide radical dianion, (D) molecules bearing more than one dap ring (X = N or CH).
is evident that anionic diazaphospholides prefer bonding via the nitrogen atoms or through the heteroaromatic p-system, whereas the corresponding neutral heterocyclic diene could also serve as a phosphorus donor toward certain transition metals. Therefore, we set to study the coordination properties of the neutral Bdapm ligand, with the view to prepare metal complexes in which the dap ring is bonded via the phosphorus atom. Herein we report the synthesis, spectroscopic and structural characterization of group 6 and group 10 metal species coordinated with the Bdapm ligand.
(CO)5W P
N
N
N
N
+
P
(CO)5W P
N
N
N
N
P W(CO)5
2
1 a
P
N
N
N
N
Bdapm
b
P c
2. Results and discussion Pure Bdapm was prepared in high yield from 1H-1,2,4-k3diazaphosphole and dichloromethane following the procedure known for the synthesis of bis(pyrazolyl)methane [17]. The melting point and NMR spectra are identical to those reported previously [15]. Its characteristic IR and Raman bands are due to aromatic (strong band at 3064 cm1) and aliphatic (medium band at 2971 cm1) CH stretching modes. The most intense Raman absorption at 901 cm1 (IR: 896 cm1) was assigned to an out-of-plane CH deformation, a band typical for the presence of an isolated CH moiety in various heterocycles and polysubstituted benzenes [18]. The electronic spectrum in the UV–Vis region showed two bands at 258 and 228 nm, attributable to p–p⁄ transitions of the dap rings. The reaction of Bdapm with [W(CO)5(NMe3)] gives a mixture of products separable by column chromatography, see Scheme 2. The major product (70%) has been identified as the complex {[W(CO)5]2(l2-P,P-Bdapm)} (2) with the bridging ligand coordinated toward two W(CO)5 fragments via phosphorus atoms. The second compound (10%) obtained from this reaction was
P
N
N
N
N
OC
P
W CO
P
Cl
N
N
N
N Mo
3
CO CO
CO
OC
P
4
Scheme 2. The preparation of group 6 compounds. (a) [W(CO)5(NMe3)], (b) [W(CO)4(1,5-cod)], (c) [Mo(g3-C3H5)(MeCN)2(CO)2Cl].
[W(CO)5(j-P-Bdapm)] (1), containing one P-bound W(CO)5 group. We have also isolated small amounts (<2%) of a third complex, {W(CO)4(j2-N,N-Bdapm)} (3), where Bdapm acts as an N,N-chelator. The yield of each complex could be modified by the reaction conditions. Using hexane at ambient temperature and a 1:1 ligand-to-metal stoichiometry affords 1 in yields up to 60%, whereas the reaction in boiling MeCN almost exclusively gives complex 3. Chelate 3 is also accessible by the reaction of Bdapm with [W(CO)4(1,5-cod)]. Both 1 and 2 are solids dissolvable in
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CH2Cl2, THF, toluene and hot hexane, whereas 3 is only sparingly soluble in polar solvents such as acetone or MeCN. Tungsten compounds 1–3 are stable toward air in the solid state, but their solutions slowly decompose to give dark suspensions. An entirely insoluble, paramagnetic blue solid (probably mixed tungsten oxides) and a solution of Bdapm have been separated from these suspensions by filtration. Prolonged heating of 1 in the solution gives the free ligand and bimetallic complex 2. In hot MeCN, fast conversion of both 1 and 2 into the N,N-chelated species 3 takes place. The 1H and 13C NMR spectra of 1 show two resonance sets attributable to two inequivalent diazaphospholyl rings. According to the asymmetric structure of 1, two singlets were found in the 31P NMR spectrum at 100.4 and 80.7 ppm, the latter being flanked with 183W satellites (1JWP = 254.1 Hz). The axial carbonyl group of W(CO)5 shows a significantly larger coupling with the phosphorus donor atom (2JPC = 36.1 Hz) than the equatorial ones (2JPC = 8.7 Hz) due to the trans-effect. The coordinated dap ring in the molecule of 1 could be easily distinguished by lower the 1JPC coupling constants (26.5 and 5.4 Hz) from the uncoordinated one (65.4 and 56.4 Hz); cf. free Bdapm: 64.0 and 56.8 Hz. The large difference in 1JPC suggests a significant change of P–C bond orders after dap coordination toward the metal. The 31P NMR spectrum of 2 shows a single resonance at 95.2 ppm flanked with satellites due to coupling with the 183W nuclei (1JWP = 256.2 Hz). Two doublets of W (CO)5 carbonyl groups (2JPC = 32.9 and 8.9 Hz for axial and equatorial CO, respectively) were found in the 13C NMR spectrum. Only one set of signals was observed in the 1H and 13C NMR spectra for both dap rings in the 2, affirming their equivalency. Similarly as in 1, the interaction of the tungsten fragment with the phosphorus atom causes a significant decrease in the 1JPC coupling constants to 27.9 and 5.7 Hz, respectively. The N,N-chelate complex 3 gives one set of 1H and 13C NMR resonances accompanied with a 31P NMR singlet at 92.7 ppm. The observed 1JPC coupling constants of 61.9 and 65.3 Hz prove that both P–C bond orders are very close and similar to those in the free Bdapm ligand. Inequivalent protons of the methylene bridge having an AX spin pattern (2JHH = 13.0 Hz) validate the rigid bonding of the Bdapm chelator toward the tungsten fragment. Four mCO bands in both IR and Raman spectra in the region 1795–2011 cm1 are characteristic for the cis-chelated W(CO)4 moiety [19]. The carbonyl stretching frequencies in 3 are slightly higher than those reported for the corresponding bis(pyrazolyl)methane (Bpm) complex {W(CO)4(j2-N, N-Bpm)} [20]. The crystal structures of 1 and 2 are fully in agreement with the spectroscopic data, see Figs. 1 and 2, respectively. Both molecules contain a pseudooctahedral W(CO)5 fragment bonded to the phosphorus atom of the dap ring. The heterocyclic rings in both 1 and 2 are rotated in opposite directions around the methylene bridge, similarly to the free ligand. The observed W–P bond distances, 2.455(1)–2.460(2) Å, are close to the data reported for phosphinine or phosphole adducts with the W(CO)5 moiety [21]. The interaction of Bdapm with tungsten does not significantly affect the endocyclic bond distances of dap, but opens the C–P–C vertex angle to value 88.4(4)° in both 1 and 2 [cf. Bdapm: 85.0(2)°] [15]. The reaction of Bdapm with [Mo(g3-C3H5)(MeCN)2(CO)2Cl] gives the molybdenum(II) complex [Mo(g3-C3H5)(j2-N,NBdapm)(CO)2Cl] (4) as an orange solid which is nearly insoluble in chloroform and hydrocarbons, but fairly soluble in polar solvents. The 1H and 13C NMR spectra of 4, measured in CD3CN, show one set of resonances together with a single 31P NMR signal at d 95.6 ppm due to equivalent dap rings. The methylene bridge protons give a single 1H NMR peak at d 6.76 ppm; the allylic resonances are broadened. An acetone solution of 4 gives a complex NMR spectra indicating the presence of several species (31P NMR resonances at d 97.5, 95.2 and 92.9 ppm). The 1H NMR spectrum shows two AX spin systems (2JHH = 13.1 and 12.7 Hz, respectively)
327
of two molecules with an asymmetric CH2 bridge, together with a major singlet at d 6.59 ppm, corresponding to a species bearing a symmetric methylene group. Regarding the expected structure with a chiral molybdenum atom, four isomers of 4 are possible, see Scheme 3. Species A, B and C, possessing a methylene bridge with inequivalent protons, should give an AX spin pattern in the 1 H NMR spectrum, whereas structure D, with a mirror plane bisecting the CH2 bridge, should yield a single methylene resonance. However, IR and Raman spectra of 4 measured in various solvents invariably give two strong mCO bands, diagnostic of a cis-Mo(CO)2 unit and the presence of the trans-carbonyl isomer D as a major species is excluded. Previous studies showed that the fac-[Mo (g3-C3H5)(CO)2] moiety (isomers B and C) represents the most energetically favorable configuration, whereas the mer- arrangement (structure A) has not been detected in any species of this type [22,23]. We thus assume that 4 dissociates on dissolution to give the fluxional cationic moiety [Mo(g3-C3H5)(j2-N,N-Bdapm) (CO)2]+ possessing a symmetric CH2 bridge. In acetonitrile, the stability of this cation is significantly enhanced and hence it is the single species detected. Therefore, the complex NMR spectra of 4 obtained in acetone could be due to the presence of an equilibrium between a fluxional cation and isomeric species B and C, see Scheme 4. This hypothesis is further supported by the fact that addition of AgOTf to an acetone solution of 4 leads to both AX spin signals vanishing, along with an increase of the single methylene resonance at d 6.59 ppm and only one peak at d 94.5 ppm remains in the 31P NMR spectrum (see Experimental section). The solvated cationic moiety present in acetonitrile solution did not change its 1 H, 13C and 31P NMR parameters, even after the addition of AgOTf. The stereochemical non-rigidity of the corresponding molybdenum(II) complexes [Mo(g3-C3H5)(CO)2(LL)X], where X is a halide and (LL) is phen, bipy or dppe, has been described in detail by Azevedo et al. [24]. The vibrational spectrum of 4 in the solid state shows carbonyl stretching bands at 1840 and 1948 cm1 (Ra: 1841 and 1951 cm1), which are higher than in the analogous complex [Mo(g3-C3H5)(j2-N,N-Bpm)(CO)2Cl] (IR: 1817/1921 cm1) [25]. Thus, the N,N-bonded Bdapm chelator renders lower electron density to the central metal atom than the Bpm ligand. X-ray diffraction analysis revealed that 4 crystallizes as isomer B, see Fig. 3. Assuming that the allyl group occupies one site, the Mo atom is pseudo-octahedrally coordinated. The allyl fragment adopts an exo conformation with respect to the Mo(CO)2 moiety, with carbonyl carbon atoms C9 and C10 eclipsing the terminal allyl carbons C8 and C6, respectively. The Mo1–N1 bond distance is longer than that of Mo1–N3 due to the trans-effect of the carbonyl ligand. Intramolecular bond distances and angles are equal within experimental errors to data reported for related complexes with the Bpm ligand [25]. The j2-N,N-coordination of the Bdapm ligand toward the molybdenum(II) center causes a slight elongation (ca 0.02 Å) of the endocyclic bonds, whereas the C–P–C vertex angle [85.7(3)°] remains almost unchanged. This observation could be attributed to larger delocalization of the heteroaromatic p-electrons in the j-N coordinated dap ring as compared to the free or j-P bonded one. We have reported similar effects in the scorpionate complex [Pd(C,N-dmba)(j2-N,N-PhTdap)] [16]. In the next part of the study, we have examined the coordinating behavior of the Bdapm ligand toward nickel(II), palladium(II) and platinum(II) species, see Scheme 5. On the addition of Bdapm to a benzene solution of Ni(acac)2, a precipitate appears which, after crystallization from acetone, gives large blue crystals characterized as [Ni(acac)2(j2-N,N-Bdapm)] (5). Complex 5 is paramagnetic at ambient temperature with a leff value of 3.20 B.M., which is typical for octahedral nickel(II) species having an electronic spin S = 1. A very broad 31P NMR resonance was found at d 232 ppm; neither 1H nor 13C NMR spectra were acquired due to significant line broadening. The IR spectrum contains strong bands
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328
N4 O3
C4
N3 C1
P2
C3
C8 O2
C5
N1
C7
P1 W1 N2
C2 C6
O1
C9 O4
C10
O5 Fig. 1. The ORTEP plot of 1 at 50% probability, showing the atom numbering scheme. Representative bond distances (Å) and angles (°): W1–P1 2.460(2), P1–C2 1.742(8), P1–C3 1.704(7), C2–N2 1.313(9), N2–N1 1.359(8), N1–C3 1.347(9), P2–C4 1.741(9), P2–C5 1.716(7), C4–N4 1.310(10), C5–N3 1.335(9), N3–N4 1.344(8), C2–P1–C3 88.5(3), C4–P2–C5 85.9(4), N1–C1–N3 111.7(6).
O4
O3
N2
C2
C9
C8 P1
N1
C6
C1
C3 C10
N3 C7
C5 N4
O8
O1
W1
O5
O2 P2
C13
C4 W2
O7
C12 C14 C11 O6
O9
C15 O10
Fig. 2. The ORTEP plot of 2 at 50% probability, showing the atom numbering scheme. The dichloromethane solvate molecule is omitted for clarity. Selected bond distances (Å) and angles (°): W1–P1 2.458(1), W2–P2 2.455(1), P1–C2 1.729(5), P1–C3 1.703(5), N1–C3 1.341(6), N1–N2 1.349(5), N2–C2 1.321(6), C2–P1–C3 88.4(2), C4–P2–C5 88.2(2), N1–C1–N2 111.5(3).
characteristic for the diketonate cycle at 1587 and 1514 cm1 (mC@O and mC@C combinations) [26]. A medium absorption found at 1709 cm1 is attributable to co-crystallized acetone. The electronic spectrum in the NIR-VIS region shows bands due to d–d transitions with wavelengths 1036, 765 and 606 nm, and extinc-
tion coefficients in the range 3.5 – 13.2 M1 cm1, close to the data reported for the corresponding [Ni(acac)2(2,20 -bipy)] complex [27]. In the solid state, molecule 5 shows a cis arrangement of both chelating diketonate and Bdapm ligands, yielding a distorted octahedral environment, see Fig. 4. The nickel cation is coordinated by
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Scheme 3. Possible isomers and diastereomers (denoted as A’and B’) of the complex 4, where R is an g3-bonded allyl group.
Scheme 4. Dynamic behavior of 4 in solution (R = g3-allyl, S = solvent molecule, X = chloride or triflate counterion).
four oxygen atoms of two acac moieties and two nitrogen atoms of the Bdapm ligand. The six-membered acetylacetonate rings are almost planar, whereas the N,N-chelate is deflected due to sp3 hybridization at the methylene bridge. Similarly as in 4, j2-N,Nbonding enlarges the internal bonds of the dap heterocycles; the observed C–P–C vertex angle is 86.2(1)°. A subsequent series of experiments were performed on platinum(II) complexes with a view to take advantage of the dipolar 195 Pt nucleus. Thus, we have followed the reaction between Bdapm and [Pt(C,N-dmba)Cl(dmso)] by 31P NMR spectroscopy. We found that the unstable complex [Pt(C,N-dmba)Cl(j-PBdapm)] (6a) is formed [signals in 31P NMR spectrum at d 99.1 and 91.4 ppm (1JPtP = 5029 Hz)] in the first instance, but it is subsequently converted into the bimetallic complex {[Pt(C,N-dmba) Cl]2(l2-P,P-Bdapm)} (6) [one resonance in the 31P NMR spectrum at d 90.1 ppm with 1JPtP of 5012 Hz] and the free ligand, regardless of the stoichiometry used. In the case of platinum(II) precursor sufficiency, the formation of 6 is a very fast and quantitative process. Once solid 6 precipitates from the reaction mixture, it is entirely insoluble in common NMR solvents and its characterization is incomplete. Nevertheless, the structures of 6a and 6 could be suggested from the 1H and 31P NMR spectra of the reaction mixtures. The presence of a single resonance in the 31P CP/MAS NMR spectrum of 6 flanked with 195Pt satellites (1JPtP = 4890 Hz) proved that both dap rings are coordinated toward the platinum center via the phosphorus atom. Using more soluble precursor [Pt(C,N-dmaf)Cl (dmso)], where dmaf is 2-(N,N-dimethylaminomethyl)ferrocenyl,
allowed us to isolate and fully characterize the tetrametallic complex {[Pt(C,N-dmaf)Cl]2(l2-P,P-Bdapm)} (7). Similarly as in the case of 6a, the intermediate [Pt(C,N-dmaf)Cl(j-P-Bdapm)] (7a) [signals in the 31P NMR spectrum at d 99.0 and 87.5 ppm (1JPtP = 5139 Hz)] was detected temporarily in the reaction mixture. The l2-P,P coordination mode in 7 has been unambiguously proved by only one set of 1H and 13C NMR signals, with low 1JPC coupling constants, and particularly by a single 31P NMR resonance at d 89.9 ppm coupled with the 195Pt isotope (1JPtP = 5143 Hz). The IR band at 1697 cm1 is due to the presence of co-crystallized acetone, while the [Fe(g5-C5H5)] moiety gives characteristic Raman lines at 3092 and 1106 cm1 (symmetric CH stretch and ring breathing, respectively) [28]. Two weak absorptions observed in the region 380–500 nm are typical for d–d electronic transitions of the ferrocenyl fragment [29]. The corresponding palladium(II) complex {[Pd(C,N-dmba) Cl]2(l2-P,P-Bdapm)} (8) has been isolated from the reaction of {[Pd(C,N-dmaf)Cl]2} with Bdapm. The unstable intermediate [Pd (C,N-dmaf)Cl(jj-P-Bdapm)] (8a) (31P NMR spectrum, d 99.1 and 91.4 ppm), was detected by 31P NMR spectroscopy, but the observed signals could not be reliably assigned to each dap ring as palladium does not possess isotopes providing notable coupling to the 31P nucleus. Pure 8 gives 1H and 13C NMR spectra very similar to the platinum(II) congener 7. The l2-P,P coordination of Bdapm is evidenced by one set of dap resonances and by low 1JPC coupling constants (32.8 and 7.0 Hz, respectively). A single 31P NMR signal has been found at d 110.4 ppm, which is the highest
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bond distances are close to those in the free ligand; the C–P–C vertex angle is opened to a value of 88.0(5)°. We have also examined the reactions between 1 and {[Pd(C,N-dmaf)Cl]2} or [Pt(C,N-dmaf)Cl(dmso)], with a view to prepare asymmetric complexes bearing the Bdapm ligand coordinated by different metals. Unfortunately, only compounds 7 and 8 were detected as the main products in all runs. Similar experiments with the N,N-coordinated derivatives 3, 4 and 5 revealed that the phosphorus atoms of Bdapm in these complexes are inert and no interactions toward Pt(II) or Pd(II) ions were observed. 3. Concluding remarks In this paper we presented the coordination ability of the Bdapm ligand toward selected complexes of group 6 and 10 metals. The acquired data shown that this neutral ligand is able to serve as a j2-N,N ligand, giving very stable chelate complexes. In particular cases, the Bdapm ligand interacts with transition metals as a bidentate l2-P,P bridge or as a monodentate j-P donor. Complexes with j-P bonded metals easily undergo substitution or redistribution reactions, changing into more stable l2-P,P or j2-N,N species. Coordination of metals toward the Bdapm ligand through the phosphorus atom outstretches the endocyclic vertex C–P–C angle by ca 3°, which is accompanied by a significant change in the 1JPC coupling constants. In the case of the j2-N,N binding mode, the structural and spectroscopic changes are much lower. Thus the P-bounded ligand behaves as a phosphaalkene donor, whereas the Bdapm ligand in N-bounded chelate complexes more likely resembles heteroaromatic diazaphospholide species.
Fig. 3. The ORTEP plot of 4 at 50% probability, showing the numbering scheme. The chloroform solvate molecule is omitted for clarity. Selected bond distances (Å) and angles (°): Mo1–N1 2.281(3), Mo1–N3 2.239(3), Mo1–Cl1 2.548(1), Mo1–Cg1 2.040 (2), Mo1–C9 1.964(4), Mo1–C10 1.926(4), P1–C2 1.752(5), P1–C3 1.723(4), C2–N1 1.325(5), N1–N2 1.359(5), N2–C3 1.332(5), C2–P1–C3 85.8(2), C4–P2–C5 85.6(2), N1–C1–N3 110.2(3), N1-Mo1–N3 78.33(11).
4. Experimental value among of all the compounds included in this study. The electronic spectrum in the visible region shows ferrocenyl d–d bands at 418 and 489 nm. Crystallization from acetone yielded crystals suitable for X-ray diffraction analysis, see Fig. 5. In the solid state, complex 8 is a symmetric species with a mirror plane bisecting the molecule at the methylene carbon atom C14. In contrast to tungsten compounds 1 and 2, the diazaphosphole rings in 8 are in an eclipsed arrangement with an intramolecular N3. . .N3a distance of 3.392(12) Å. The palladium center possesses a square planar coordination environment with the sum of the valence angles around the palladium atom close to 360°. The phosphorus atom of the Bdapm ligand is coordinated in a trans-position with respect to the nitrogen donor atom of the dmaf ligand. The endocyclic dap
4.1. Materials All preparative reactions and manipulations were routinely carried out under an inert atmosphere of argon using Schlenk techniques. Solvents were dried and deoxygenated in a PureSolv MD 7 solvent purification system. Metal carbonyls and [Ni(acac)2]3 were obtained from Sigma–Aldrich and used after vacuum sublimation. The starting complexes [W(CO)5(NMe3)] [30], [Mo(g3-C3H5)(MeCN)2(CO)2Cl] [31], [Pt(C,N-dmba)Cl(dmso)], [Pt(C,N-dmaf)Cl(dmso)] [32], [Pd(C,N-dmaf)Cl]2 [33] and 1H-1,2,4diazaphosphole [3,16] were prepared by procedures reported elsewhere.
c
P
b
N
N
N
N Ni
O O
P
d
M Cl
M Fe
Fe
P
Cl
7a (M = Pt) 8a (M = Pd)
a
P
N N
N N
(CH3)2N
N(CH3)2
(CH3)2N Bdapm
N N
N N
P
M Cl
Fe
7 (M = Pt) 8 (M = Pd)
P O
P
N
N
N
N
Me2N P
Pt Cl
O 6a
d
NMe2 Pt Cl
P
N
N
N
N
Me2N P
Pt Cl
6
5 Scheme 5. Syntheses of group 10 complexes. (a) [Ni(acac)2]3, (b) [Pt(C,N-dmba)Cl(dmso)], (c) [Pt(C,N-dmaf)Cl(dmso)] or [Pd(C,N-dmaf)Cl]2, (d) ligand redistribution or excess of organometallic precursor.
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4.2. Spectroscopic measurements
Fig. 4. The ORTEP plot of 5 drawn at the 50% probability level and showing the atom numbering scheme. Hydrogen atoms and a molecule of acetone are omitted for clarity. Selected bond distances (Å) and angles (°): Ni1–N2 2.125(1), Ni1–N2 2.126(2), P1–C2 1.753(2), P1–C3 1.719(3), C2–N2 1.316(3), N1–N2 1.355(2), N1–C3 1.334(3), C2–P1–C3 86.2(2), C4–P2–C5 86.2(1), N1–C1–N3 110.7(2), N2–Ni1–N4 86.41(7).
The 1H, 13C{1H} and 31P{1H} NMR spectra were measured at 300 K on a Bruker Avance III 500 MHz instrument equipped with a Prodigy CryoProbe; the chemical shifts were referenced to external neat (CH3)4Si or H3PO4, respectively. The 31P CP/MAS NMR spectra were recorded at room temperature on a Bruker Ascend 500 spectrometer at a magnetic field of 11.746 T (31P resonance frequency of 202 MHz) with a 3.2 mm DVT CP/MAS probe (external reference NH4H2PO4). IR spectra were recorded on a Nicolet 6700 FTIR spectrometer using a single-bounce silicon ATR crystal. Raman spectra were recorded in the range 4000–100 cm1 with a Nicolet iS50 equipped with iS50 Raman module (excitation laser 1064 nm) or on a HoribaJobin Yvon (785 nm, samples 5 and 8). Electronic absorption spectra (200–1080 nm) were run on a BlackComet C-SR-100 concave grating spectrometer. The near infrared spectrum of 5 was obtained on a UV-3600 Shimadzu in the region 500–3500 nm. Elemental CHN analyses were obtained with a Fisions EA 1108 microanalyzer. Solid samples for elemental analyses were finely powdered and dried in a vacuum (102–103 Pa) at 50 °C for 12 h to remove residual or co-crystallized solvents. Melting points were determined in argon-sealed capillaries using a Stuart SMP-3 melting point apparatus and are uncorrected. The magnetic susceptibility of 5 was measured in the solid state at room temperature on an Evans susceptibility balance MSB-AUTO. Corrections due to diamagnetic contributions of the ligands were applied. 4.3. Crystal structure determination The X-ray data for crystals of 1, 2, 4, 5 and 8 were obtained at 150 K using an Oxford Cryostream low-temperature device on a
Fig. 5. The ORTEP plot of 8 at the 30% probability level and showing the atom numbering scheme. Hydrogen atoms and a molecule of acetone solvate are omitted for clarity; carbon atoms C7A–C13A represent one component of the disorder. The positions of carbon atoms generated by symmetry operations are not labeled. Selected bond distances (Å) and angles (°): Pd1–N1 2.134(9), Pd1–C1 1.983(10), Pd1–Cl1 2.385(4), Pd1–P1 2.192(3), P1–C15 1.723(11), P1–C16 1.706(9), C16–N2 1.333(12), N2–N3 1.358(11), N3–C15 1.296(14), C15–P1–C16 88.0(5), N2–C14–N2a 111.9(9).
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2
JPH = 42.5 Hz, 2H, CH). 13C NMR d, ppm: 70.0 (CH2), 158.1 (d, JPC = 56.8 Hz, CH), 164.9 (d, 1JPC = 64.0 Hz, CH). 31P{1H} NMR d, ppm: 100.7 (s). IR: identical to that in Ref. [15]. Raman (cm1): 3065vs, 3021w, 2971m (mCH), 901vs (cCH). UV–Vis [MeCN, kmax, nm, e, log(M1 cm1)]: 258 (3.93), 228 (3.90). Anal. Calc. for C5H6N4P2: C, 32.62; H, 3.29; N, 30.44. Found: C, 32.71; H, 3.26; N, 30.37%.
Nonius KappaCCD diffractometer with Mo Ka radiation (k = 0.71073 Å), a graphite monochromator and the / and v scan modes; relevant crystallographic data are listed in Table 1. Data reductions were performed with DENZO-SMN [34]. The absorption was corrected by integration methods [35]. The structures were solved by direct methods (Sir92) [36] and refined by full matrix least-squares based on F2 (SHELXL97) [37]. Hydrogen atoms were mostly localized in a difference Fourier map, however to ensure uniformity of the treatment of the crystals, all hydrogen atoms were recalculated into idealized positions (riding model) and assigned temperature factors, Hiso(H) = 1.2 Ueq (pivot atom) or of 1.5 Ueq (methyl). H atoms in methyl, methylene, methine and hydrogen atoms in aromatic rings were placed with C–H distances of 0.96, 0.97, 0.98 and 0.93 Å, respectively. Thermal ellipsoids of the chlorine atoms of the chloroform solvent in 4 were improved with the standard ISOR instruction implemented in the SHELXL97 software [37]. In the structure of 8, one cyclopentadienyl ring as well as the methyl groups of the dimethylaminomethyl moiety were disordered; the disorders were treated with the SAME instruction, allowing the whole group to be split into two positions with approximate occupancies of 7/3 and 6/4 respectively.
1
4.5. [W(j-P-Bdapm)(CO)5] (1) A mixture of Bdapm (313 mg, 1.7 mmol) and [W(CO)5(NMe3)] (575 mg, 1.5 mmol) was stirred in 100 ml of hexane at room temperature for 5 days. After filtration and solvent evaporation, the yellow residue was chromatographed on silica gel (3 30 cm, CH2Cl2 eluent). The first band, containing a small amount of 2, was discarded and the second band yielded, after evaporation and crystallization from hot hexane, 255 mg (33%) of colorless 1. Single-crystals suitable for XRD analysis were obtained on slow cooling of a saturated hexane solution. Mp.: 166 °C (dec). 1H NMR (CDCl3) d, ppm: 6.69 (s, 2H, CH2), 8.49 (d, 2JPH = 50.1 Hz, 1H, CH, coordinated ring), 8.61 (d, 2JPH = 36.7 Hz, 1H, CH, coordinated ring), 8.65 (d, 2JPH = 47.3 Hz, 1H, CH), 8.71 (d, 2JPH = 38.5 Hz, 1H, CH). 13C NMR d, ppm: 70.8 (CH2), 151.9 (d, 1JPC = 26.5 Hz, CH, coordinated ring), 158.4 (d, 1JPC = 56.4 Hz, CH), 159.5 (d, 1JPC = 5.4 Hz, CH, coordinated ring), 165.5 (d, 1JPC = 65.4 Hz, CH) 193.7 (d, 1JWC = 124.6 Hz, 2 JPC = 8.7 Hz, equatorial CO), 198.0 (d, 2JPC = 36.1 Hz, axial CO). 31P 1 { H} NMR d, ppm: 80.7 (s, 1P, 1JWP = 254.1 Hz), 100.4 (s, 1P). IR (cm1): 3111m, 3079m, 3056s, 2978w, 2965m (mCH), 2079s, 2002m, 1969w, 1907vs-br (mC„O), 924m (cCH), 901m (cCH). Raman (cm1): 3111m, 3081m, 3057s, 3038w, 2980s (mCH), 2084s, 1997vs, 1961m, 1919vs (mC„O), 926vs (cCH), 902m (cCH). UV–Vis [CH2Cl2, kmax, nm, e, log(M1 cm1)]: 358sh (3.36), 338 (3.48), 294 (3.75), 258sh (4.11), 234 (4.41). Anal. Calc. for C10H6N4O5P2W: C, 23.64; H, 1.19; N, 11.03. Found: C, 23.75; H, 1.24; N, 10.89%.
4.4. Bis(1,2,4-diazaphosphol-1-yl)methane (Bdapm) 4.50 g (52.3 mmol) of 1,2,4-diazaphosphole was dissolved in CH2Cl2 (150 ml) and to this solution fine powders of 5.00 g (89.1 mmol) KOH, 12.00 g (86.8 mmol), K2CO3 and 1.50 g (8.4 mmol) (CH3)4NHSO4 were added. After stirring for 48 h under reflux, the solution was filtered, the remaining solid washed with 3 50 ml of boiling CH2Cl2 and the combined extracts were evaporated in a vacuum. Large colorless crystals of Bdapm have been obtained by crystallization from boiling hexane on cooling to 20 °C (yield: 4.02 g, 82%). Mp.: 114 °C. 1H NMR (CDCl3) d, ppm: 6.71 (s, 2H, CH2), 8.69 (d, 2JPH = 51.0 Hz, 2H, CH), 8.80 (d,
Table 1 Crystallographic data and refinement details for 1, 2, 4, 5 and 8. Compound
1
2
4
5
8
Empirical formula MW Crystal system Space group
C10H6N4O5P2W 507.98 triclinic
C15H6N4O10P2W2CH2Cl2 916.80 triclinic
P1 6.678 (3) 9.4320 (13) 12.544 (6) 97.91 (3) 103.28 (5) 90.330 (15) 2 761.1 (5) 2.217 0.59 0.40 0.13 colorless, plate 7.83 476 8, 8; 12, 12; 16, 16 1.7–27.5 13 646 3464 (0.119) 3327 199 3.68/5.83
P1 10.7970 (14) 11.0730 (12) 11.686 (2) 87.069 (14) 68.674 (18) 87.148 (9) 2 1299.0 (4) 2.344 0.51 0.46 0.31 light yellow, block 9.23 848 14, 14; 14, 14; 15, 15 1.8–27.5 31 391 5952 (0.075) 5370 325 1.89/2.55
C10H11ClMoN4O2P2CHCl3 531.93 monoclinic P21/c
C15H20N4NiO4P2C3H6O 499.08 monoclinic P21/c
C31H38Cl2Fe2N6P2Pd2C3H6O 1010.09 orthorhombic Pnma
13.3290 (5) 16.2331 (17) 8.9380 (9) 90 75.763 (6) 90 4 1924.2 (3) 1.836 0.32 0.11 0.09 yellow, block 1.42 1048 17, 17; 18, 21; 11, 10 1.5–27.5 21 554 4342 (0.066) 3628 217 1.73/1.51
9.4320 (7) 11.8609 (8) 21.4591 (19) 90 97.390 (7) 90 4 2380.7 (3) 1.392 0.56 0.42 0.30 blue, block 0.98 1040 11, 12; 15, 14; 27, 24 1.9–27.4 19 463 5288 (0.043) 4485 271 0.30/0.49
13.4220 (7) 29.1920 (14) 9.812 (4) 90 90 90 4 3844.5 (16) 1.745 0.58 0.32 0.13 orange, block 1.919 2024 17, 17; 36, 37; 12, 12
0.050/0.139/1.07
0.025/0.068/1.18
0.040/0.106/1.08
0.032/0.085/1.13
0.099/0.241/1.25
a (Å) b (Å) c (Å) a (°) b (°) c (°) Z V (Å3) Dx (g cm3) Crystal size (mm) Color, crystal shape l (mm1) F(0 0 0) h; k; l range h range (°) Reflections measured Independent (Rint) a Observed [I > 2r(I)] Parameters refined Maximum/minimum Dq (e Å3) Rb/wRb/GOFc a b c
P P Rint = |F2o Fo,2mean|/ F2o. P P P P R(F) = ||Fo| |Fc||/ |Fo|for observed data; wR(F2) = [ (w(F2o F2c )2)/( w(F2o)2)]½ for all data. P GOF = [ (w(F2o F2c )2)/(Ndiffrs – Nparams)]½ for all data.
1.4–27.5 22 733 4456 (0.113) 3755 249 3.31/1.90
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4.6. {[W(CO)5]2(l2-P,P-Bdapm)} (2) Bdapm (202 mg, 1.1 mmol) and [W(CO)5(NMe3)] (841 mg, 2.2 mmol) were refluxed in 50 ml of THF for 24 h. The solvent was removed in vacuum and the residue was dissolved in CH2Cl2 (40 ml) and filtered. The filtrate was evaporated to dryness and chromatographed on silica gel (3 30 cm, CH2Cl2 eluent). The first band gave, after evaporation and crystallization from a CH2Cl2hexane mixture, 511 mg (56%) of light yellow 2. Single-crystals suitable for XRD analysis were obtained on cooling of a saturated CH2Cl2 solution to 20 °C. Mp.: 149 °C (dec.). 1H NMR (CDCl3) d, ppm: 6.66 (s, 2H, CH2), 8.64 (d, 2JPH = 50.1 Hz, 2H, CH), 8.73 (d, 2JPH = 36.5 Hz, 2H, CH). 13C NMR d, ppm: 71.3 (CH2), 152.1 (d, 1 JPC = 27.9 Hz, CH), 159.9 (d, 1JPC = 5.7 Hz, CH), 193.6 (d, 1JWC = 124.8 Hz, 2JPC = 9.0 Hz, equatorial CO), 197.8 (d, 1 JWC = 155.8 Hz, 2JPC = 32.3 Hz, axial CO). 31P{1H} NMR d, ppm: 82.9 (s, 1JWP = 256.6 Hz). IR (cm1): 3119m, 3104w, 3083m, 2987w (mCH), 2080m, 1990w, 1940m, 1898vs-br (mC„O), 934m (cCH). Raman (cm1): 3118m, 3083m, 2982m (mCH), 2080s, 1990vs, 1936s, 1915s (mC„O), 930s (cCH). UV–Vis [CH2Cl2, kmax, nm, e, log(M1 cm1)]: 360sh (4.23), 340 (4.34), 296 (4.51), 260sh (4.78), 236 (4.16). Anal. Calc. for C15H6N4O10P2W2: C, 21.66; H, 0.73; N, 6.74. Found: C, 21.92; H, 0.80; N, 6.67%. 4.7. [W(jj2-N,N-Bdapm)(CO)4] (3) Method A: A mixture of W(CO)6 (500 mg, 1.4 mmol) and Bdapm (262 mg, 1.4 mmol) in 50 of MeCN was refluxed for 48 h. The solvent was removed in vacuum and the residue was washed with hot hexane (2 20 ml), dissolved in acetone and filtered through an alumina bed. The yellow filtrate was concentrated in a vacuum and cooled to 20 °C, giving bright yellow microcrystalline 3 (415 mg, 61% yield). Method B: 364 mg (0.9 mmol) of [W(CO)4(1,5-cod)] and Bdapm (166 mg, 0.9 mmol) were refluxed in 50 ml of THF for 12 h. After the workup described above, a yellow powder of 3 was obtained (384 mg, 72%) Mp.: 178 °C (dec.). 1H NMR (acetone-d6) d, ppm: 7.02 (d, 2JHH = 13.0 Hz, 1H, CH2), 7.62 (d, 2JHH = 13.0 Hz, 1H, CH2), 9.34 (d, 2JPH = 43.6 Hz, 2H, CH), 9.50 (d, 2JPH = 37.3 Hz, 2H, CH). 13 C NMR d, ppm: 71.3 (CH2), 163.4 (d, 1JPC = 61.9 Hz, CH), 173.7 (d, 1JPC = 65.3 Hz, CH), CO carbons were not observed due to poor solubility. 31P{1H} NMR d, ppm: 92.7 (s). IR (cm1): 3101m, 3035m, 2957w (mCH), 2011s, 1897sh-m, 1860s, 1795vs (mC„O), 904m (cCH). Raman (cm1): 3102s, 3036m, 2959m, 2924m (mCH), 2012vs, 1906m, 1838vs, 1802s (mC„O), 906s (cCH). UV–Vis [CH2Cl2, kmax, nm, e, log(M1 cm1)]: 389sh (3.07), 341 (3.17), 295 (3.66), 251 (3.99), 234sh (3.92). Anal. Calc. for C9H6N4O4P2W: C, 22.52; H, 1.26; N, 11.67. Found: C, 22.65; H, 1.22; N, 11.49%. 4.8. [Mo(g3-C3H5)(j2-N,N-Bdapm)(CO)2Cl] (4) 373 mg (1.2 mmol) of [Mo(g3-C3H5)(MeCN)2(CO)2Cl] was dissolved in 50 ml of THF and 221 mg (1.2 mmol) of Bdapm was added. After refluxing the mixture for 24 h, the solvent was removed in a vacuum. The brown residue obtained was washed with hot hexane (3 20 ml), dissolved in hot CHCl3 (100 ml) and charcoal was added. After reducing the volume of the filtrate to one-third and cooling to 20 °C, yellow crystals of 4 were obtained (337 mg, 68%). XRD quality single-crystals were grown from a saturated CHCl3 solution on slow cooling to 4 °C. Mp.: 198 °C (dec.). 1 H NMR (CD3CN, cationic species [Mo(g3-C3H5)(j2-N,N-Bdapm) (CO)2]+) d, ppm: 1.10 (s-br, 2H, allyl, anti-CH2), 3.22 (s-br, 2H, allyl, syn-CH2), 3.69 (s-br, 1H, allyl, CH), 6.76 (s, 2H, CH2), 8.71 (d, 2 JPH = 47.8 Hz, 2H, CH), 9.02 (d, 2JPH = 39.6 Hz, 2H, CH). 13C NMR d, ppm: 55.9 (s-br, CH2, allyl), 70.8 (CH2, methylene bridge), 71.8 (s-br, CH, allyl), 160.1 (d, 1JPC = 55.6 Hz), 165.6 (d, 1JPC = 64.3 Hz),
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224.5 (s-br, CO). 31P{1H} NMR d, ppm: 95.6 (s). 1H NMR (4 after the addition of AgOTf in acetone-d6) d, ppm: 1.28 (s-br, 2H, allyl), 2.97 (s-br, 2H, allyl), 3.82 (s-br, 1H, allyl), 6.83 (s, 2H, CH2), 8.64 (d, 2JPH = 46.4 Hz, 2H, CH), 9.01 (d, 2JPH = 39.9 Hz, 2H, CH). 31P{1H} NMR d, ppm: 95.9 (s). IR (cm1): 3098m, 3090m, 3071s, 2996s, 2950w (mCH), 1947s, 1840vs (mC„O), 902m (cCH). Raman (cm1): 3099m, 3090s, 3074m, 3060m, 3049m, 2996vs, 2953m (mCH), 1957s, 1841vs (mC„O), 902vs (cCH). UV–Vis [MeCN, kmax, nm, e, log(M1.cm1)]: 414sh (2.71), 347 (3.14), 253 (4.36), 233 (4.40). Anal. Calc. for C10H11Cl1MoN4O2P2: C, 29.11; H, 2.69; N, 13.58. Found: C, 29.35; H, 2.59; N, 13.49%. 4.9. [Ni(acac)2(Bdapm)] (5) Anhydrous [Ni(acac)2]3 (620 mg, 0.8 mmol) was dissolved in benzene (50 ml) and Bdamp (441 mg, 2.4 mmol) was added with stirring. After heating to 80 °C for 12 h, the blue precipitate that formed was filtered, washed with hot hexane (3 10 ml) and dried in a vacuum. The solid was then dissolved in boiling acetone (40 ml), filtered and the light blue filtrate was concentrated to 15 ml and cooled to 20 °C for 2 days. Heating of the isolated large blue crystals to 50 °C in a high vacuum for 48 h yielded a blue powder of pure 5 (891 mg, 84%). Mp.: 182 °C. 31P{1H} NMR (acetone-d6) d, ppm: 232 br. leff = 3.20 ± 0.02 (B. M. at 293 K). IR (cm1): 3073s, 3024s, 2997m, 2983m, 2916m (mCH), 1709s (mC@O, acetone), 1587vs, 1514vs (mC@O + mC@C, acac), 899m (cCH). Raman (cm1): 3075s, 2916s-br (mCH), 1586w, 1514w (mC@O + mC@C, acac), 900vs (cCH). UV–Vis [MeCN, kmax, nm, e, log(M1 cm1)]: 1036 (1.12), 765 (0.55), 606 (1.11), 311sh (3.99), 297 (4.13), 258 (4.03), 228 (4.13). Anal. Calc. for C15H20N4NiO4P2: C, 40.85; H, 4.57; N, 12.70. Found: C, 41.13; H, 4.66; N, 12.59%. 4.10. {[Pt(C,N-dmba)Cl]2-l2-P,P-Bdapm} (6) A mixture of [Pt(C,N-dmba)Cl(dmso)] (84.2 mg, 190 l mol) and Bdapm (17.4 mg, 95 l mol) was stirred in 7 ml of CH2Cl2 for 30 min. A white precipitate was separated by centrifugation, washed with 2 1 ml CH2Cl2, then 2 1 ml of Et2O and dried in a vacuum. Yield 85.1 mg of 6 (97%). Mp.: 220 °C (dec.) 1H NMR (CD2Cl2) d, ppm: 2.98 (s, 3JPtH = 36.6 Hz, 6H, N(CH3)2), 4.09 (s, 3 JPtH = 41.7 Hz, 2H, CH2NMe2), 6.72 (s, 2H, CH2), 6.89–7.47 (m, 4H, Ph), 8.67–8.99 (m-br, 4H, dap). 31P{1H} NMR (CD2Cl2) d, ppm: 90.1 (s, 1JPtP = 5012 Hz). 31P-CP/MAS d, ppm: 86.9 (s, 1JPtP = 4890 Hz). Intermediate 6a, 31P NMR (CD2Cl2) d, ppm: 99.1 (s, 1P), 91.4 (s, 1P, 1JPtP = 5029 Hz). IR (cm1): 3070vs, 3001m, 2923m-br (mCH), 939m (cCH). Raman (cm1): 3071s, 3062m, 3051m, 3004m, 2990m, 2977m, 2926s-br (mCH), 938vvs (cCH). UV–Vis [CH2Cl2, kmax, nm, e, log(M1 cm1)]: 287 (4.50), 249 (4.50), 234 (4.52). Anal. Calc. for C23H30Cl2N6P2Pt2: C, 30.24; H, 1.01; N, 9.20. Found: C, 30.36; H, 1.10; N, 9.15%. 4.11. {[Pt(C,N-dmaf)Cl]2-l2-P,P-Bdapm} (7) 60.7 mg (110 l mol) of [Pt(C,N-dmaf)Cl(dmso)] and 10.1 mg (55 l mol) of Bdapm were dissolved in 5 ml of CH2Cl2 and stirred for 12 h. An orange precipitate was separated by centrifugation, washed with cold Et2O (3 1 ml) and dried in a vacuum. Crystallization from an acetone/Et2O mixture gave red tiny needles of pure 7 (yield 55.8 mg, 90%). Mp.: 265 °C (dec.). 1H NMR (CDCl3) d, ppm: 2.92 (s, 3JPtH = 25.4 Hz, 6H, N(CH3)2), 3.25 (s, 3JPtH = 29.5 Hz, 6H, N(CH3)2), 3.47 (d, 2JHH = 13.8 Hz, 2H, CH2NMe2), 3.87 (d, 2 JHH = 13.7 Hz, 2H, CH2NMe2), 4.02 (s, 2H, Cp’), 4.12 (s, 10H, Cp), 4.21 (s, 2H, Cp’), 4.27 (s, 2H, Cp’), 6.71 (s, 2H, CH2), 8.81 (d, 2 JHP = 46.9, 2H, CH), 9.03 (d, 2JHP = 31.8, 2H, CH). 13C NMR d, ppm: 52.5 (N(CH3)2), 52.7 (N(CH3)2), 62.7 (Cp’), 68.0 (Cp’), 69.0 (CH2NMe2), 70.0 (Cp), 71.2 (Cp’), 72.5 (CH2), 95.6 (Cp’-ipso),
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141.5 (d, 1JCP = 54.3 Hz, CH), 148.0 (d, 1JCP = 16.7 Hz, CH). 31P{1H} NMR (CD2Cl2) d, ppm: 89.9 (s, 1JPtP = 5143 Hz). Intermediate 7a, 31 P NMR (CD2Cl2) d, ppm: 99.0 (s, 1P), 87.5 (s, 1P, 1JPtP = 5139 Hz). IR (cm1): 3090s, 3002w, 2963m-br (mCH), 1697s (mC@O, acetone), 1103m (mC@C, Fc ring-breathing), 929m (cCH). Raman (cm1): 3092vs-br, 2985m, 2955m (mCH), 1105vvs (mC@C, Fc ring-breathing), 930s (cCH). UV–Vis [CH2Cl2, kmax, nm, e, log(M1 cm1)]: 498 (2.96), 373sh (3.41), 284 (4.43), 234 (4.54). Anal. Calc. for C31H38Cl2Fe2N6 P2Pt2: C, 32.97; H, 3.39; N, 7.44. Found: C, 33.22; H, 3.49; N, 7.35%. 4.12. {[Pd(C,N-dmaf)Cl]2-l2-P,P-Bdapm} (8) [Pd(C,N-dmaf)Cl]2 (154 mg, 0.2 mmol), Bdapm (36.8 mg, 0.2 mmol) and dichloromethane (20 ml) were refluxed for 12 h. The solvent was evaporated and the red solid obtained was washed with hot hexane (3 5 ml) and crystallized from acetone at 20 °C to give fine orange crystals of 8 (169 mg, 89% yield). Mp.: 201 °C (dec.). 1H NMR (CHCl3) d, ppm: 2.28 (s, 6H, acetone solvate), 2.84 (s, 6H, N(CH3)2), 3.12 (s, 6H, N(CH3)2), 3.36 (d, 2H, 2JHH = 14.0 Hz, CH2NMe2), 4.00 (d, 2H, 2JHH = 14.0 Hz, CH2NMe2), 4.04 (s, 2H, Cp’), 4.11 (s, 2H, Cp’), 4.15 (s, 10H, Cp), 4.19 (s, 2H, Cp’), 6.76 (s, 2H, CH2), 8.90 (d, 2H, 2JHP = 47.9, CH), 9.22 (d, 2H, 2JHP = 32.7, CH). 13 C NMR d, ppm: 51.8 (d, 3JCP = 2.9 Hz, N(CH3)2), 52.3 (d, 3JCP = 2.5 Hz, N(CH3)2), 62.7 (Cp’), 66.7 (Cp’), 67.0 (d, 3JCP = 4.7 Hz, CH2NMe2), 70.4 (Cp), 71.2 (CH2), 72.5 (Cp’), 96.0 (Cp’-ipso), 98.7 (d, 2JCP = 7.5 Hz, Cp’-ipso), 148.5 (d, 1JCP = 32.8 Hz, CH), 153.6 (d, 1 JCP = 7.0 Hz, CH). 31P{1H} NMR d, ppm: 110.4 (s). Intermediate 8a, 31P NMR (CH2Cl2/CDCl3) d, ppm: 101.2 (s, 1P), 107.8 (s, 1P). IR (cm1): 3089vs, 3040m, 2995m, 2891m-br (mCH), 1696s (mC@O, acetone), 1104m (mC@C, Fc ring-breathing), 924m (cCH). Raman (cm1): 3089m, 2983m, 2919m (mCH), 1696w (mC=O, acetone), 1104vvs (mC@C, Fc ring-breathing), 923s (cCH). UV–Vis [CH2Cl2, kmax, nm, e, log(M1 cm1)]: 489sh (3.22), 418 (3.46), 319sh (3.71), 269sh (4.33), 234 (4.57). Anal. Calc. for C31H38Cl2Fe2N6P2Pd2: C, 39.11; H, 4.02; N, 8.83. Found: C, 39.32; H, 4.12; N, 8.75%. Appendix A. Supplementary data CCDC 1496781–1496785 contains the supplementary crystallographic data for 4, 2, 5, 8 and 1, respectively. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected]. References [1] G. Maerkl, I. Troetsch, Angew. Chem. 96 (1984) 899.
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