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Cyclopentadienyl and indenyl molybdenum(II) complexes bearing planar N,N,N-chelating ligands
Journal of Organometallic Chemistry 772-773 (2014) 299e306
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Cyclopentadienyl and indenyl molybdenum(II) complexes bearing planar N,N,N-chelating ligands b, Jaromír Vinkla rek b, Zden ka R b Jan Honzí cek a, *, Iva Honzí ckova u zi ckova a 573, Pardubice, Institute of Chemistry and Technology of Macromolecular Materials, Faculty of Chemical Technology, University of Pardubice, Studentska Czech Republic b 573, Pardubice, Czech Republic Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentska
a r t i c l e i n f o
a b s t r a c t
Article history: Received 30 July 2014 Received in revised form 9 September 2014 Accepted 23 September 2014 Available online 2 October 2014
The reactivity of cyclopentadienyl and indenyl molybdenum(II) complexes [(h5-Cp0 )Mo(CO)2(NCMe)2] [BF4] (Cp0 ¼ Cp, Ind, 1,3-Ph2C9H5) with a series of planar N,N,N-chelating ligands was scrutinized. The planar N,N,N-chelating ligands give k2-complexes [(h5-Cp0 )Mo(CO)2(k2-N,N,NL)][BF4] those undergo in particular cases a spontaneous release of carbon monoxide to give [(h5-Cp0 )Mo(CO)(k3-N,N,NL)][BF4] depending on several factors including the basicity of the tridentate ligand as well as the nature of the starting molybdenum(II) compound. This behaviour strongly contrasts with tripodal ligands those do not affect cis-Mo(CO)2 moiety even upon tridentate coordination. All structure types, discussed in this work, were elucidated by the spectroscopic measurements as well as by the X-ray crystallography. © 2014 Elsevier B.V. All rights reserved.
Keywords: Molybdenum compounds Indenyl effect Pincer ligands Infrared spectroscopy CO-releasing molecule
Introduction Tridentate ligands have found a wide application in the inorganic chemistry. They cover number of shapes and constrained geometries that strongly affect their coordination ability. Tripodal (so-called “scorpionate”) ligands [1] and planar (so-called “pincer”) ligands [2] represent two most pronounced groups of the tridentate ligands. Their bonding properties are very different. The tripodal ligands were designed for the assembly of fac-complexes [3] while the rigid planar ligands usually give transition metal complexes in a mer-configuration [4]. The restrictions in the coordination sphere of the central metal, possessed by a tridentate ligand, are often used for a tuning of the physical and chemical properties of transition metal compounds that found a number of applications in the catalysis [5] and may serve as a model system for the active site of metalloenzymes [6]. This work will demonstrate that coordination of planar tridentate ligands could stimulate a controlled release of carbon monoxide from molybdenum complexes [(h5-Cp0 ) 0 0 Mo(CO)2(NCMe)2][BF4] (1: Cp ¼ Cp ¼ C5H5, 2: Cp ¼ Ind ¼ C9H7, 3:
* Corresponding author. Fax: þ420 46603 7068. E-mail address: [email protected] (J. Honzí cek). http://dx.doi.org/10.1016/j.jorganchem.2014.09.028 0022-328X/© 2014 Elsevier B.V. All rights reserved.
Cp0 ¼ 1,3-Ph2C9H5), shown in Scheme 1. This behaviour is currently widely scrutinized due to recently recognized therapeutic properties of CO and following comprehensive search for new species enable to deliver CO into diseased cells [7]. Although the starting compounds have similar molecular structure, a different reactivity is expected since the replacement of the cyclopentadienyl ligand with the indenyl accelerates reaction rates due to a lower energetic barrier of the haptotropic shift of the p-ligand [8]. This, so-called “indenyl effect”, was comprehensively scrutinized on various molybdenum compounds [9] and was utilized for an activation of the coordinated ligands [10]. This study is focused mainly on three neutral planar N,N,Nchelating ligands (terpy: 2,20 ;60 ,200 -terpyridine, bzimpy: 2,6bis(benzimidazol-20 -yl)pyridine, bzoxpy: 2,6-bis(benzoxazol-20 yl)pyridine). The structures of the observed reaction products will be confronted with related complexes of neutral tripodal N,N,Nchelating ligand (tpm: tris(pyrazol-1-yl)methane, developed by ~o [11]. It will be demonstrated that the release of carbon Roma monoxide, induced upon the coordination, can be effectively controlled by several factors including shape of the tridentate ligand, basicity of the nitrogen donor atoms and the nature of the starting molybdenum(II) compound. All structure types, discussed in this work, will be supported by X-ray crystallographic data.
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Table 1 Summary of the infrared data for the complexes bearing the planar tridentate ligandsa.
n(CO)
Scheme 1. The starting molybdenum(II) complexes 1e3.
Results and discussion Complexes of 2,20 ;60 ,200 -terpyridine At first, the reactivity of the cyclopentadienyl complex 1 with terpy was studied by 1H NMR spectroscopy. The in situ experiments in the NMR tube revealed an initial formation of the complex with one uncoordinated side arm [(h5-Cp)Mo(CO)2(k2-terpy)][BF4] (4). Such k2-compound is unstable undergoing a spontaneous release of carbon monoxide to give the k3-complex [(h5-Cp)Mo(CO)(k3terpy)][BF4] (5), see Scheme 2. The bonding mode of the terpy ligand was easily recognized by 1 H NMR spectroscopy since the k2-intermediate (4) is C1-symmetric while the k3-product (5) belongs to the point group Cs. For this purpose, resonances of the protons from the central pyridine ring could be taken as diagnostic. Hence, 1H NMR spectrum of the k30 0 complex (5) show one doublet at 8.63 ppm (H3 ,5 ) and one triplet at 40 8.16 ppm (H ) that is proving the equivalency of the protons in 3and 5-position in the central pyridine ring. In a lower symmetric k2complex (4), these positions are not equivalent that results in the 0 0 appearance of three resonances. Signals of the protons H3 and H4 3 were observed at a similar field as in case of the k -complex (5) 0 while the proton beside the uncoordinated arm (H5 ) appears at a 3 much higher field (7.53 ppm). The k -complex 5 was isolated and the loss of one carbonyl ligand was confirmed through the appearance of only one CO stretching band in the infrared spectrum [n(CO) ¼ 1809 cm1]. Unfortunately, the isolation of the pure intermediate 4 was not successful owing to its spontaneous decomposition giving 5 upon handling. In the next stage, a reaction of the indenyl molybdenum complexes 2 and 3 with terpy was studied. It gives, after similar work up as before, the products of decarbonylation [(h5-Ind)Mo(CO)(k3terpy)][BF4] (6) and [(h5-1,3-Ph2C9H5)Mo(CO)(k3-terpy)][BF4] (7), respectively (Scheme 2). The k3-coordination mode in these species was elucidated from the 1H NMR spectra similarly as in case of the cyclopentadienyl analogue (5). The proposed structures are further supported by the appearance of only one CO stretching band in region of the terminal carbonyl groups, see Table 1. The successive
Scheme 2. The reaction of molybdenum complexes 1e3 with terpy. Reagents and conditions: (a) terpy/CH2Cl2/16 h (b) MeCN/7 days.
5 6 7 12 13 14 15 16 17 18 19 a
1809 1835 1847 1965, 1841, 1844 1847 1975, 1968, 1874 1889
1885 1818
1894 1894
The frequencies are given in cm1.
growth of the CO stretching energy from the cyclopentadienyl complex (5) over the indenyl (6) to the 1,3-diphenylindenyl analogues (7) is due to a decreasing back-bonding from the molybdenum atom to the carbonyl ligands. It reflects the decrease of the electron density on the molybdenum atom since the phenyl substituents as well as the annulated benzene ring have electronwithdrawing properties. Further 1H NMR experiments reveal that the formation of the indenyl complexes 6 and 7 proceeds much faster than in case of the cyclopentadienyl analogue 5. The reactions giving compounds 6 and 7 are complete immediately after dissolution of the starting material in CD2Cl2. At this stage, the cyclopentadienyl analogue (1) stays fully unreacted. An apparent formation of the intermediate 4 was observed in terms of hours. The crystal structures of the compounds 5e7 were determined by X-ray diffraction analysis. The cationic complexes have a squarepyramidal structure with the h5-bonded cyclopentadienyl or indenyl ligand in the apical position. The basal plane is occupied with one carbonyl ligand and three nitrogen donor atom of the terpy, see Figs. 1e3. The bond distances between molybdenum and centroid of the C5-ring (MoeCg) were found to be in a narrow range 1.995(2)e2.024(1) Å. The MoeC(CO) bond lengths vary between 1.927(3) and 1.934(2) Å. The MeN bonds to the central pyridine ring of the terpy ligand are significantly shorter [MoeN: 2.092(2)e
Fig. 1. ORTEP drawing of cationic complex [(h5-Cp)Mo(CO)(k3-terpy)]þ present in the crystal structure of 5. The labelling scheme for all non-hydrogen atoms is shown. The thermal ellipsoids are drawn at the 30% probability level. Only one of two crystallographically independent cations is shown for clarity.
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Table 2 Selected bond lengths of the complexes bearing terpya.
MoeC(CO) MoeCg(Cp0 )d MoeN
Ue D(MeC)f
5b
5c
6
7∙CH2Cl2
1.929(3) 1.996(2) 2.107(2) 2.168(2) 2.182(2) e e
1.927(3) 1.995(2) 2.107(2) 2.178(2) 2.182(2) e e
1.933(2) 2.006(1) 2.096(2) 2.167(2) 2.176(2) 4.4(2) 0.129(2)
1.934(2) 2.024(1) 2.092(2) 2.156(2) 2.175(2) 2.0(2) 0.103(2)
a
The distances are given in Å. Molecule A in unit cell. c Molecule B in unit cell. d The centroid of five carbon atoms of h5-Cp0 . e U is the envelop fold angle defined for the indenyl ligand as the angle between planes defined by C1, C2 and C3 and that of C1, C3, C8 and C9 [13]. f D(MeC) represents the differences in the metal-carbon bonds. It is defined for the indenyl compounds as the difference between the averages of the metal-carbon distances MeCl, MeC2, and MeC3 and those of MeC8 and MeC9 [13]. b
Fig. 2. ORTEP drawing of the cationic complex [(h5-Ind)Mo(CO)(k3-terpy)]þ present in the crystal structure of 6. The labelling scheme for all non-hydrogen atoms is shown. The thermal ellipsoids are drawn at the 30% probability level.
2.107(2) Å] than those to the side pyridine rings [MoeN: 2.156(2)e 2.182(2) Å], see Table 2. This observation well correlates with the previous studies on the homoleptic terpyridine complexes [M(terpy)3] (M ¼ Ti, V, Cr, Mo, W] [12]. The low values of U and D(MeC) observed for the indenyl ligands in the complexes 6 and 7 (see Table 2) are in line with the expected h5-coodination mode. No significant close contacts between complex cations and tetrafluoroborate anion were observed. Although observed k3-coordination mode of terpy, in the compounds 5e7, seems to be obvious, here observed CO loss is rather anomalous. Hence, 2,20 -bipyridine complexes [(h5-Cp0 ) 0 Mo(CO)2(bpy)][BF4] (8: Cp ¼ Cp; 9: Ind), those could be taken as satisfactory model systems for the k2-terpy intermediates, show relatively low frequencies of CO stretching [8: na(CO) ¼ 1973 cm1,
Fig. 3. ORTEP drawing of the cationic complex [(h5-1,3-Ph2C9H5)Mo(CO)(k3-terpy)]þ present in the crystal structure of 7∙CH2Cl2. The labelling scheme for all non-hydrogen atoms is shown. The thermal ellipsoids are drawn at the 30% probability level.
ns(CO) ¼ 1901 cm1, 9: na(CO) ¼ 1974 cm1, ns(CO) ¼ 1878 cm1] [14] that is usually not compatible with CO release under mild conditions without photochemical activation [15]. Strong bonding of carbonyl ligands was also observed in case of cyclopentadienyl and indenyl complexes bearing tripodal N,N,N-chelating ligands: [(h5-Cp)Mo(CO)2(k2-tpm)][BF4] (10), [(h3-Ind)Mo(CO)2(k3-tpm)] [BF4] (11) those were synthesized similarly by ligand exchange reaction from 1 and 2, respectively [11]. Our experiments with these species have confirmed their stability under ambient conditions and were utilized for preparation of single crystals suitable for elucidation of their structures by X-ray crystallography. X-ray structures of tris(pyrazol-1-yl)methane complexes The cyclopentadienyl compound [(h5-Cp)Mo(CO)2(k2-tpm)] [BF4] (10) has a square-pyramidal structure with the h5-coordinated Cp ligand in the apical position. Two carbonyl ligands and two nitrogen donor atoms of tpm form the basal plane (Fig. 4). The geometric parameters describing the coordination sphere of the molybdenum atom are summarized in Table 3. The coordinated pyrazolyl rings in the cation of 4 are not coplanar [PlN1eN2PlN3eN4 ¼ 33.66(14) ] due to sp3-hybridization on the
Fig. 4. ORTEP drawing of the cationic complex [(h5-Cp)Mo(CO)2(k2-tpm)]þ present in the crystal structure of 10∙MeCN. The labelling scheme for all non-hydrogen atoms is shown. The thermal ellipsoids are drawn at the 30% probability level.
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Table 3 Selected bond lengths of the complexes bearing tpma.
MoeC(CO) MoeCg(Cp0 )b MoeN
Uc D(MeC)c a b c d
10∙MeCN
11
1.963(2) 1.971(3) 1.986(1) 2.221(2) 2.223(2) 4.120(2)d e e
1.961(2) 1.964(2) 2.116(2) 2.183(2) 2.256(2) 2.274(2) 21.9(2) 0.815(2)
The distances are given in Å. The centroid of five carbon atoms of h5-Cp or three carbon atoms of h3-Ind. For definition see footnote of Table 2. Non-bonding distance Mo/N. Scheme 3. The reaction of the molybdenum complexes 1e3 with bzimpy. Reagents and conditions: (a) bzimpy/CH2Cl2/16 h (b) MeOH/7 days.
bridging carbon. The MoeN bond lengths are longer [2.221(2); 2.223(2) Å] than usual for isostructural complexes with fivemembered chelate rings [2.173(3)e2.194(4) Å] [14,16]. The remaining pyrazolyl ring stays outside the coordination sphere of the molybdenum below Mo(CO)2 moiety; almost coplanar with it. The nonbonding distance Mo1/N6 was found to be 4.120(2) Å. The indenyl compound [(h3-Ind)Mo(CO)2(k3-tpm)][BF4] (11) has a distorted octahedral structure with the h3-coordinated indenyl and one nitrogen donor atom of tpm in the axial positions. The equatorial positions are occupied with two remaining nitrogen donor atoms and two carbonyl groups, see Fig. 5. The coordination sphere of molybdenum resembles the isoelectronic tris(pyrazol-1-yl)borate analogue [(h3-Ind)Mo(CO)2 (k3-Tp)] reported earlier [17]. The h3-coordination mode of the indenyl ligand is confirmed by high values of the envelop fold angle [U ¼ 21.9(2) ] and D(MeC) [0.815(2) Å]. The MoeN bond to the axial nitrogen atom was found to be considerably shorter [2.183(2) Å] than to the equatorial nitrogen atoms [2.256(2) and 2.274(2) Å]. This distortion is caused by a trans-effect of the carbonyl ligands [18] as was previously demonstrated on several pseudooctahedral molybdenum(II) complexes [17,19]. No significant close contacts between complex cations (10 and 11) and tetrafluoroborate anion were observed.
Fig. 5. ORTEP drawing of the cationic complex [(h3-Ind)Mo(CO)(k3-tpm)]þ present in the crystal structure of 11. The labelling scheme for all non-hydrogen atoms is shown. The thermal ellipsoids are drawn at the 30% probability level.
Complexes of 2,6-bis(benzimidazol-20 -yl)pyridine and 2,6bis(benzoxazol-20 -yl)pyridine Finally, the high stability of tpm complexes 10 and 11 suggests that similar species may appear upon reaction with planar tridentate ligands as intermediates. The attempts to stabilize supposed intermediates led us to another N,N,N-chelating ligands. Bzimpy and bzoxpy were selected mainly due to a different basicity of the heterocycles in the side arms. The nitrogen donor atom of benzimidazole shows similar basicity as pyridine while benzoxazole is much less basic [20]. Furthermore, the use of symmetrical ligands facilitates the NMR spectra assignment since the expected k2-complexes are C1-symmetric while the k3-complexes Cs-symmetric. The protons of the pyridine ring could be taken as a diagnostic tool, similarly as was described in detail for the terpy complexes. Bzimpy reacts with the cyclopentadienyl precursor 1 to give the k2-complex [(h5-Cp)Mo(CO)2(k2-bzimpy)][BF4] (12). This compound seems to be stable but the dissolution in highly polar solvents such as methanol induces the gradual release of carbon monoxide to give the k3-complex [(h5-Cp)Mo(CO)(k3-bzimpy)][BF4] (13), see Scheme 3. The indenyl compounds 2 and 3 give the
Scheme 4. The reaction of the molybdenum complexes 1e3 with bzoxpy. Reagents and conditions: (a) bzoxpy/CH2Cl2. (b) stirring for 16 h.
J. Honzícek et al. / Journal of Organometallic Chemistry 772-773 (2014) 299e306
expected k3-complexes [(h5-Ind)Mo(CO)(k3-bzimpy)][BF4] (14) and [(h5-1,3-Ph2C9H5)Mo(CO)(k3-bzimpy)][BF4] (15), respectively. Unfortunately, the very low solubility of bzimpy and its complexes disables using standard solution NMR techniques for a detailed investigation of the reaction mechanism. The reaction of bzoxpy with the cyclopentadienyl complex 1 gives stable k2-complex [(h5-Cp)Mo(CO)2(k2-bzoxpy)][BF4] (16) that correlates with a lower basicity of nitrogen in the side arms of this tridentate ligand. The indenyl precursors 2 and 3 produce, after the standard work up, the k3-complexes [(h5-Ind)Mo(CO)(k3bzoxpy)][BF4] (18) and [(h5-1,3-Ph2C9H5)Mo(CO)(k3-bzoxpy)][BF4] (19), respectively (see Scheme 4). Nevertheless, following the reaction of 2 with bzoxpy has revealed the appearance of C1-symmetric complex species that was assigned to above postulated k2intermediate [(h5-Ind)Mo(CO)2(k2-bzoxpy)][BF4] (17). This species is formed quantitatively immediately after the dissolution of the starting compounds in CD2Cl2. A pure sample of the compound 17 was isolated using a modified synthetic procedure. The proposed structure of 17 was further supported by the infrared spectroscopy since two CO stretching bands were observed at 1968 cm1 and 1894 cm1. These frequencies near the values for the aforementioned 2,20 -bipyridine analogue [(h5-Ind)Mo(CO)2(bpy)][BF4] (9) that implies similar strength of the bonds MoeCO. Thus, the much lower stability of 17 toward CO release is apparently not caused by weaker bonding of the carbonyl ligand but the result of the very strong enforcing properties of the tridentate ligand side arm. In contrast to fac-enforcing tpm, the reaction of bzoxpy with indenyl compounds 2 and 3 does not give any stable intermediates with slipped indenyl ring as confirmed by our 1H NMR experiments. This is very surprising mainly in the light of fact that a related isostructural h3-allyl compound mer-[(h3-2-MeC3H4) Mo(CO)2(k3-terpy)][OTf] is a stable compound and reported frequencies of CO stretching bands (1965, 1874 cm1) do not suggest the activation of the MoeCO bond [21]. The crystal structures of two compounds bearing bzoxpy ligand, 16∙CH2Cl2 and 18∙CH2Cl2, were determined by X-ray diffraction analysis. These cationic compounds have a square-pyramidal structure with the h5-coordinated ligand in the apical position while the planar square is occupied with the carbonyl ligands and the nitrogen donor atoms of the tridentate ligand. The geometric parameters describing the coordination sphere of the molybdenum atom are given in Table 4. No significant close contacts between complex cation and tetrafluoroborate anion were observed. The compound 16∙CH2Cl2 bears two carbonyl ligands and k2coordinated bzoxpy, see Fig. 6. The MoeN bond lengths to coordinated pyridine and benzoxazole are 2.278(2) and 2.166(3) Å, respectively. The non-bonding distance Mo/N to the uncoordinated benzoxazole arm is 3.767(4) Å.
303
Fig. 6. ORTEP drawing of cationic complex [(h5-Cp)Mo(CO)2(k2-bzoxpy)]þ present in the crystal structure of 16∙CH2Cl2. The labelling scheme for all non-hydrogen atoms is shown. The thermal ellipsoids are drawn at the 20% probability level.
The compound 18∙CH2Cl2 bears one carbonyl ligand and k3coordinated bzoxpy, see Fig. 7. The coordination of the second benzoxazole side arm causes significant shortening of the MoeN bond to coordinated pyridine [2.104(5); 2.118(5) Å]. Similarly as observed for the isostructural terpyridine complexes (5, 6 and 7∙CH2Cl2), these bonds are considerably shorter than in case of the side heterocyclic arms [2.133(5)e2.168(5) Å]. Conclusions Here presented study clearly demonstrates that the reactions of cyclopentadienyl and indenyl molybdenum compounds (1e3) with planar N,N,N-chelating ligands could be used for the assembly of metastable k2-complexes those are able to release carbon monoxide. Stability of these compounds is controlled by several factors including basicity of the nitrogen donor atoms and a barrier of haptotropic rearrangement of the coordinated p-ligand. The shape of the tridentate ligand seems to be crucial for the activation of MoeCO bond since complexes bearing tripodal ligands are stable as reported in literature [11] and further confirmed by our experiments. The newly synthesized complexes with k3-coordinated tridentate ligand, appearing upon CO release, are unprecedented. The donor strength of the coordinated tridentate ligands well correlates with the energy of CO stretching mode. Hence, a coordination of weakly-donating bzoxpy (in 18 and 19) is reflected in higher frequencies of n(CO) than observed for their terpy (6, 7) and bzimpy counterparts (14, 15), see Table 1.
Table 4 Selected bond lengths of the complexes bearing bzoxpya.
MoeC(CO) MoeCg(Cp0 )d MoeN
Ue D(MeC)e a b c d e f
16∙CH2Cl2
18∙CH2Cl2b
18∙CH2Cl2c
1.968(3) 1.977(4) 1.989(2) 2.166(3) 2.278(2) 3.767(4)f e e
1.950(7)
1.962(7)
1.990(3) 2.118(5) 2.157(5) 2.168(5) 3.5(7) 0.096(7)
1.988(2) 2.104(5) 2.133(5) 2.163(5) 4.6(5) 0.134(5)
The distances are given in Å. Molecule A in unit cell. Molecule B in unit cell. The centroid of five carbon atoms of h5-Cp0 . For definition see footnote of Table 2. Non-bonding distance Mo/N.
Fig. 7. ORTEP drawing of cationic complex [(h5-Ind)Mo(CO)(k3-bzoxpy)]þ present in the crystal structure of 18∙CH2Cl2. The labelling scheme for all non-hydrogen atoms is shown. The thermal ellipsoids are drawn at the 20% probability level. Only one of two crystallographically independent cations is shown for clarity.
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The effect of the coordinated p-ligand is following. The low energetic barrier of the h5eh3 indenyl ligand rearrangement strongly accelerates the rate of the chelating ligand coordination as well as the CO release. It results in much lower stability of the indenyl complexes bearing k2-coordinated planar N,N,N-chelating ligand. Nevertheless, the complexes with weakly-donating tridentate ligands (e.g. 17 bearing bzoxpy) are enough stable for ongoing experimental studies. The substitution in the indenyl ligand with the phenyl groups has much smaller effect on the reactivity than expected. At the same reaction conditions, the compounds 2 and 3 give analogous products. A different outcome is expected for more sterically hindered tridentate ligands but these were not scrutinized here. Experimental section General considerations All operations were performed under a nitrogen atmosphere using conventional Schlenk-line techniques. The solvents were purified and dried by standard methods [22]. The starting materials were available commercially or prepared according to the procedures published elsewhere: tpm [23], bzimpy [24], bzoxpy [25], [(h5-Cp)Mo(CO)2(NCMe)2][BF4] (1) [16], [(h5-Ind)Mo(CO)2(NCMe)2] [BF4] (2) [26], [(h5-1,3-Ph2C9H5)Mo(CO)2(NCMe)2][BF4] (3) [27], [(h5-Cp)Mo(CO)2(k2-tpm)][BF4] (10) [11], [(h3-Ind)Mo(CO)2(k3tpm)][BF4] (11) [11]. The infrared spectra were recorded in the 4000e400 cm1 region (resolution 2 cm1) on a Nicolet Magna 6700 FTIR spectrometer using a Diamond Smart Orbit ATR. 1H and 13 1 C{ H} NMR spectra were measured in CDCl3, CD2Cl2, acetone-d6, MeCN-d3, methanol-d4 or DMSO-d6 solutions on a Bruker Avance 400 spectrometer at room temperature. The chemical shifts are given in ppm relative to TMS. Characterization of 2,6-bis(benzimidazol-20 -yl)pyridine (bzimpy) 1 H NMR (acetone-d6, 400 MHz, d ppm): 8.48 (d, 3J(1H, H) ¼ 7.8 Hz, 2H, H3,5), 8.21 (t, 3J(1H, 1H) ¼ 7.8 Hz, 1H, H4), 7.78 (s-br, 0 0 0 0 0 0 2H, H4 e7 ), 7.66 (s-br, 2H, H4 e7 ), 7.30 (s-br, 4H, H4 e7 ). 1H NMR 6 3 1 1 (DMSO-d , 400 MHz, d ppm): 8.34 (d, J( H, H) ¼ 7.8 Hz, 2H, H3,5), 0 0 8.15 (t, 3J(1H, 1H) ¼ 7.8 Hz, 1H, H4), 7.76 (m, 4H, H4 e7 ), 7.30 (m, 4H, 40 e70 H ). 1
Characterization of 2,6-bis(benzoxazol-20 -yl)pyridine (bzoxpy) 1
H NMR (CDCl3, 400 MHz, d ppm): 8.53 (d, 3J(1H, 1H) ¼ 7.9 Hz, 0 0 2H, H3,5), 8.11 (t, 3J(1H, 1H) ¼ 7.9 Hz, 1H, H4), 7.86 (m, 2H, H4 e7 ), 7.73 40 e70 40 e70 1 6 (m, 2H, H ), 7.43 (m, 4H, H ). H NMR (acetone-d , 400 MHz, d ppm): 8.61 (d, 3J(1H, 1H) ¼ 7.9 Hz, 2H, H3,5), 8.34 (t, 3J(1H, 0 0 0 0 1 H) ¼ 7.9 Hz, 1H, H4), 7.89 (m, 4H, H4 e7 ), 7.53 (m, 4H, H4 e7 ). Reaction of [(h5-Cp)Mo(CO)2(NCMe)2][BF4] (1) with 2,20 ;60 ,200 terpyridine (terpy) [(h5-Cp)Mo(CO)2(NCMe)2][BF4] (1; 19.3 mg, 50 mmol) was dissolved in CH2Cl2 (15 mL) and treated with terpy (11.7 mg, 50 mmol). The reaction mixture was stirred at room temperature overnight. Volatiles were vacuum evaporated. A recrystallization from CH2Cl2/ Et2O gives 1:2 mixture of [(h5-Cp)Mo(CO)2(k2-terpy)][BF4] (4) and [(h5-Cp)Mo(CO)(k3-terpy)][BF4] (5). Prolonged stirring of the mixture in MeCN followed with a recrystallization from MeCN/Et2O gives the analytically pure sample of the compound 5. 4: 1H NMR (MeCN-d3, 400 MHz, d ppm, from the mixtures with 5): 8.98 (ddd, 3 1 J( H, 1H) ¼ 5.8 Hz, 4J(1H, 1H) ¼ 1.5 Hz, 5J(1H, 1H) ¼ 0.8 Hz, 1H, terpy, H6), 8.82 (ddd, 3J(1H, 1H) ¼ 4.9 Hz, 4J(1H, 1H) ¼ 1.8 Hz, 5J(1H,
1
00
H) ¼ 1.0 Hz, 1H, terpy, H6 ), 8.65 (dd, 3J(1H, 1H) ¼ 8.3 Hz, 4J(1H, 0 00 H) ¼ 1.4 Hz, 1H, terpy, H3 ), 8.61 (m, 1H, terpy H3,5,5 ), 8.26 (dd, 3 1 1 3 1 1 40 J( H, H) ¼ 7.6 Hz, J( H, H) ¼ 8.3 Hz, 1H, terpy, H ), 8.21 (ddd, 3 1 J( H, 1H) ¼ 8.3 Hz, 3J(1H, 1H) ¼ 7.5 Hz, 4J(1H, 1H) ¼ 1.5 Hz, 1H, terpy, 00 H4), 8.02 (td, 3J(1H, 1H) ¼ 7.8 Hz, 4J(1H, 1H) ¼ 1.8 Hz, 1H, terpy, H4 ), 3 1 1 4 1 1 5 1 1 7.66 (dt, J( H, H) ¼ 7.8 Hz, J( H, H) ¼ 1.0 Hz, J( H, H) ¼ 1.0 Hz, 00 00 1H, terpy, H3 ), 7.59e7.55 (m, 2H, terpy H3,5,5 ), 7.53 (dd, 3J(1H, 1 4 1 1 50 H) ¼ 8.3 Hz, J( H, H) ¼ 1.4 Hz, 1H, terpy, H ), 5.50 (s, 5H, Cp). 5: Yield: 15.5 mg (30 mmol, 61%). Violet powder. Mp: 150e165 C (dec.). Anal. Calc. for C21H16BF4MoN3O: C: 49.54; H: 3.17; N: 8.25. Found: C: 49.37; H: 3.26; N: 8.18. FTIR (ATR-C, cm1): 1809 vs [n(CO)]. 1H NMR (MeCN-d3, 400 MHz, d ppm): 9.03 (ddd, 3J(1H, 00 1 H) ¼ 5.8 Hz, 4J(1H, 1H) ¼ 1.4 Hz, 5J(1H, 1H) ¼ 0.9 Hz, 2H, terpy, H6,6 ), 3 1 1 4 1 1 5 1 1 8.67 (ddd, J( H, H) ¼ 8.3 Hz, J( H, H) ¼ 1.4 Hz, J( H, H) ¼ 0.9 Hz, 00 0 0 2H, terpy, H3,3 ), 8.63 (d, 3J(1H, 1H) ¼ 8.0 Hz, 2H, terpy, H3 ,5 ), 8.16 (t, 3 1 1 40 3 1 1 J( H, H) ¼ 8.0 Hz, 1H, terpy, H ), 8.06 (ddd, J( H, H) ¼ 8.3 Hz, 00 3 1 J( H, 1H) ¼ 7.4 Hz, 4J(1H, 1H) ¼ 1.4 Hz, 2H, terpy, H4,4 ), 7.39 (ddd, 3 1 1 3 1 1 4 1 1 J( H, H) ¼ 7.4 Hz, J( H, H) ¼ 5.8 Hz, J( H, H) ¼ 1.4 Hz, 2H, terpy, 00 H5,5 ), 5.07 (s, 5H, Cp). 13C NMR (MeCN-d3, 101 MHz, d ppm): 240.5 (1C, CO), 157.2 (2C, tpy), 155.9 (2Cipso, tpy), 148.9 (2Cipso, tpy), 137.5 (2C, tpy), 134.6 (2Cipso, tpy), 125.1 (2C, tpy), 123.9 (2C, tpy), 122.6 (2C, tpy), 98.6 (5C, Cp). Single crystals of 5 suitable for the X-ray analysis were prepared by careful overlayering of a MeCN solution with Et2O. 1
Synthesis of [(h5-Ind)Mo(CO)(k3-terpy)][BF4] (6) [(h5-Ind)Mo(CO)2(NCMe)2][BF4] (2; 21.8 mg, 50 mmol) was dissolved in CH2Cl2 (15 mL) and treated with terpy (11.7 mg, 50 mmol). The reaction mixture was stirred at room temperature overnight. Volatiles were vacuum evaporated. The crude product was washed with Et2O, recrystallized from MeCN/Et2O, CH2Cl2/Et2O and vacuum dried. Yield: 27.4 mg (49 mmol, 98%). Violet powder. Mp: 155e165 C (dec.). Anal. Calc. for C25H18BF4MoN3O: C: 53.70; H: 3.24; N: 7.51. Found: C: 53.65; H: 3.22; N: 7.59. FTIR (ATR-C, cm1): 1835 vs [n(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 9.26 (ddd, 3J(1H, 00 1 H) ¼ 5.9 Hz, 4J(1H, 1H) ¼ 1.4 Hz, 5J(1H, 1H) ¼ 0.8 Hz, 2H, terpy, H6,6 ), 8.54 (ddd, 3J(1H, 1H) ¼ 8.2 Hz, 4J(1H, 1H) ¼ 1.4 Hz, 5J(1H, 1H) ¼ 0.8 Hz, 00 0 0 2H, terpy, H3,3 ), 8.48 (d, 3J(1H, 1H) ¼ 8.0 Hz, 2H, terpy, H3 ,5 ), 8.08 (t, 3 1 1 40 3 1 1 J( H, H) ¼ 8.0 Hz, 1H, terpy, H ), 8.03 (ddd, J( H, H) ¼ 8.2 Hz, 00 3 1 J( H, 1H) ¼ 7.4 Hz, 4J(1H, 1H) ¼ 1.4 Hz, 2H, terpy, H4,4 ), 7.40 (ddd, 3 1 1 3 1 1 4 1 1 J( H, H) ¼ 7.4 Hz, J( H, H) ¼ 5.8 Hz, J( H, H) ¼ 1.4 Hz, 2H, terpy, 00 H5,5 ), 6.50 (dd, 3J(1H, 1H) ¼ 6.5 Hz, 4J(1H, 1H) ¼ 3.0 Hz, 2H, Ind, 4e7 H ), 6.39 (t, 3J(1H, 1H) ¼ 3.0 Hz, 1H, Ind, H2), 6.13 (dd, 3J(1H, 1 H) ¼ 6.5 Hz, 4J(1H, 1H) ¼ 3.0 Hz, 2H, Ind, H4e7), 5.34 (d, 3J(1H, 1 H) ¼ 3.0 Hz, 2H, Ind, H1,3). Single crystals of 6 suitable for the X-ray analysis were prepared by careful overlayering of a CH2Cl2 solution with hexane. Synthesis of [(h5-1,3-Ph2C9H5)Mo(CO)(k3-terpy)][BF4] (7) The reaction was carried out as described for the compound 6 but with [(h5-1,3-Ph2C9H5)Mo(CO)2(NCMe)2][BF4] (3; 29.4 mg, 50 mmol) and terpy (11.7 mg, 50 mmol). The crude product was washed with Et2O, recrystallized twice from CH2Cl2/Et2O and vacuum dried. Yield: 32.7 mg (46 mmol, 92%). Violet powder. Mp: 155e165 C (dec.). Anal. Calc. for C37H26BF4MoN3O: C: 62.47; H: 3.68; N: 5.91. Found: C: 62.28; H: 3.56; N: 5.83. FTIR (ATR-C, cm1): 1847 vs [n(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 8.57 (d, 3J(1H, 00 1 H) ¼ 5.8 Hz, 2H, terpy, H6,6 ), 8.52 (d, 3J(1H, 1H) ¼ 8.0 Hz, 2H, terpy, 00 30 ,50 3 1 1 H ), 8.46 (d, J( H, H) ¼ 8.2 Hz, 2H, terpy, H3,3 ), 8.18 (t, 3J(1H, 1 40 3 1 1 H) ¼ 8.0 Hz, 1H, terpy, H ), 7.82 (ddd, J( H, H) ¼ 8.2 Hz, 3J(1H, 00 1 H) ¼ 7.4 Hz, 4J(1H, 1H) ¼ 1.4 Hz, 2H, terpy, H4,4 ), 7.37 (s-br, 10H, Ph), 6.85 (ddd, 3J(1H, 1H) ¼ 7.4 Hz, 3J(1H, 1H) ¼ 5.8 Hz, 4J(1H, 00 1 H) ¼ 1.4 Hz, 2H, terpy, H5,5 ), 6.79 (s, 1H, Ind, H2), 6.65 (m, 4H, Ind,
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H4e7). Single crystals of 7∙CH2Cl2 suitable for the X-ray analysis were prepared by careful overlayering of a CH2Cl2 solution of 7 with hexane. Single crystals of [(h5-Cp)Mo(CO)2(k2-tpm)][BF4]∙MeCN (10∙MeCN) Single crystals of 10∙MeCN suitable for the X-ray analysis were prepared by careful overlayering of a MeCN solution of 10 with Et2O. Single crystals of [(h3-Ind)Mo(CO)2(k3-tpm)][BF4] (11) Single crystals of 11 suitable for the X-ray analysis were prepared by careful overlayering of a MeCN solution of the starting compound 2 with a thin layer of Et2O. This system was immediately overlayered with a solution of tpm in Et2O. Synthesis of [(h5-Cp)Mo(CO)2(k2-bzimpy)][BF4] (12) [(h5-Cp)Mo(CO)2(NCMe)2][BF4] (1; 38.6 mg, 100 mmol) was dissolved in CH2Cl2 (30 mL) and treated with bzimpy (31.1 mg, 100 mmol). The reaction mixture was stirred at room temperature overnight, filtered over a short pad of a glass wool and volatiles were vacuum evaporated. The crude product was washed with Et2O, recrystallized twice from CH2Cl2/Et2O and vacuum dried. Yield: 53.1 mg (86 mmol, 86%). Ruby red powder. Mp: 150e160 C (dec.). Anal. Calc. for C26H18BF4MoN5O2: C: 50.76; H: 2.95; N: 11.38. C: 50.90; H: 2.85; N: 11.32. FTIR (ATR-C, cm1): 3290 m-br [n(NeH)], 1965 vs [na(CO)], 1885 vs [ns(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 12.66 (s, 1H, bzimpy, NH), 12.15 (s, 1H, bzimpy, NH), 8.71 (d, 3J(1H, 1H) ¼ 7.8 Hz, 1H, bzimpy, H3), 8.12 (t, 3J(1H, 1 H) ¼ 7.9 Hz, 1H, bzimpy, H4), 7.89 (d, 3J(1H, 1H) ¼ 8.0 Hz, 1H, 0 0 bzimpy, H5), 7.85e7.42 (m, 8H, bzimpy, H4 e7 ), 5.65 (s, 5H, Cp). Synthesis of [(h5-Cp)Mo(CO)(k3-bzimpy)][BF4] (13) [(h5-Cp)Mo(CO)2(k2-bzimpy)][BF4] (12; 30.8 mg, 50 mmol) was dissolved in methanol (15 mL) and stirred for 7 days. Volatiles were vacuum evaporated and the crude product was washed with Et2O, CH2Cl2 and vacuum dried. Yield: 25.7 mg (44 mmol, 88%). Indigo blue powder. Mp: 150e160 C (dec.). Anal. Calc. for C25H18BF4MoN5O: C: 51.14; H: 3.09; N: 11.93. C: 50.95; H: 3.27; N: 12.13. FTIR (ATR-C, cm1): 1841 vs [n(CO)], 1818 vs [n(CO)]. 1H NMR (methanol-d4, 400 MHz, d ppm): 8.41 (d, 3J(1H, 1H) ¼ 7.9 Hz, 2H, bzimpy, H3,5), 8.03 (t, 3J(1H, 1H) ¼ 7.9 Hz, 1H, bzimpy, H4), 7.92 (d, 0 0 3 1 J( H, 1H) ¼ 7.7 Hz, 2H, bzimpy, H4 ,7 ), 7.76 (d, 3J(1H, 1H) ¼ 8.0 Hz, 0 0 40 ,70 2H, bzimpy, H ), 7.55 (m, 4H, bzimpy, H5 ,6 ), 5.09 (s, 5H, Cp). Synthesis of [(h5-Ind)Mo(CO)(k3-bzimpy)][BF4] (14) The reaction was carried out as described for the compound 6 but with [(h5-Ind)Mo(CO)2(NCMe)2][BF4] (2; 21.8 mg, 50 mmol) and bzimpy (15.6 mg, 50 mmol). The crude product was washed with Et2O, recrystallized twice from CH2Cl2/Et2O and vacuum dried. Yield: 22.9 mg (36 mmol, 72%). Indigo blue powder. Mp: 160e170 C (dec.). Anal. Calc. for C29H20BF4MoN5O: C: 54.66; H: 3.16; N: 10.99. Found: C: 54.83; H: 3.19; N: 11.04. FTIR (ATR-C, cm1): 3260 m-br [n(NeH)], 1844 vs [n(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 11.70 (s, 2H, bzimpy, NH), 8.09 (d, 3J(1H, 1H) ¼ 7.8 Hz, 2H, bzimpy, H3,5), 7.79 (d, 0 0 3 1 J( H, 1H) ¼ 8.0 Hz, 2H, bzimpy, H4 ,7 ), 7.59 (d, 3J(1H, 1H) ¼ 8.0 Hz, 2H, 0 0 40 ,70 bzimpy, H ), 7.40 (m, 5H, bzimpy, H4,4 ,5 ), 6.38 (t, 3J(1H, 1 2 3 1 1 H) ¼ 2.9 Hz, 1H, Ind, H ), 6.26 (dd, J( H, H) ¼ 6.5 Hz, 4J(1H, 1 H) ¼ 3.0 Hz, 2H, Ind, H4e7), 5.70 (dd, 3J(1H, 1H) ¼ 6.5 Hz, 4J(1H, 1 H) ¼ 3.0 Hz, 2H, Ind, H4e7), 5.12 (d, 3J(1H, 1H) ¼ 2.9 Hz, 2H, Ind, H1,3).
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Synthesis of [(h5-1,3-Ph2C9H5)Mo(CO)(k3-bzimpy)][BF4] (15) The reaction was carried out as described for the compound 6 but with [(h5-1,3-Ph2C9H5)Mo(CO)2(NCMe)2][BF4] (3; 29.4 mg, 50 mmol) and bzimpy (15.6 mg, 50 mmol). The crude product was washed with Et2O, recrystallized twice from CH2Cl2/Et2O and vacuum dried. Yield: 31.3 mg (40 mmol, 79%). Indigo blue powder. Mp: 160e170 C (dec.). Anal. Calc. for C41H28BF4MoN5O: C: 62.38; H: 3.58; N: 8.87. Found: C: 62.26; H: 3.35; N: 8.97. FTIR (ATR-C, cm1): 3265 m-br [n(NeH)], 1847 vs [n(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 11.50 (s, 2H, bzimpy, NH), 8.25 (d, 3J(1H, 1H) ¼ 8.0 Hz, 2H, bzimpy, H3,5), 7.58 (t, 3 1 J( H, 1H) ¼ 8.0 Hz, 1H, bzoxpy, H4), 7.85 (d, 3J(1H, 1H) ¼ 8.2 Hz, 2H, 0 0 H4 ,7 ), 7.25e7.15 (m, 6H of bzimpy, 10H of Ph), 7.09 (m, 2H, Ind, H4e7), 6.55 (s, 1H, Ind, H2), 6.47 (m, 2H, Ind, H4e7). Synthesis of [(h5-Cp)Mo(CO)2(k2-bzoxpy)][BF4] (16) The reaction was carried out as described for the compound 6 but with [(h5-Cp)Mo(CO)2(NCMe)2][BF4] (1; 19.3 mg, 50 mmol) and bzoxpy (15.7 mg, 50 mmol). The crude product was washed with Et2O, recrystallized twice from CH2Cl2/Et2O and vacuum dried. Yield: 30.2 mg (49 mmol, 98%). Ruby red powder. Mp: 145e150 C (dec.). Anal. Calc. for C26H16BF4MoN3O4: C: 50.60; H: 2.61; N: 6.81. C: 50.72; H: 2.60; N: 6.74. FTIR (ATR-C, cm1): 1975 vs [na(CO)], 1894 vs [ns(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 8.82 (dd, 3J(1H, 1 H) ¼ 8.0 Hz, 4J(1H, 1H) ¼ 1.5 Hz, 1H, bzoxpy, H3), 8.43 (t, 3J(1H, 1 H) ¼ 7.9 Hz, 1H, bzoxpy, H4), 8.08 (dd, 3J(1H, 1H) ¼ 7.8 Hz, 4J(1H, 0 0 1 H) ¼ 1.5 Hz, 1H, bzoxpy, H5), 8.00 (m, 2H, bzoxpy, H4 e7 ), 7.81 (m, 40 e70 40 e70 3H, bzoxpy, H ), 7.73 (m, 1H, bzoxpy, H ), 7.61 (m, 2H, bzoxpy, 0 0 H4 e7 ), 5.85 (s, 5H, Cp). Single crystals of 16∙CH2Cl2 suitable for the X-ray analysis were prepared by careful overlayering of a CH2Cl2 solution of 16 with hexane. Synthesis of [(h5-Ind)Mo(CO)2(k2-bzoxpy)][BF4] (17) [(h5-Ind)Mo(CO)2(NCMe)2][BF4] (2; 21.8 mg, 50 mmol) was dissolved in CH2Cl2 (2 mL) and treated with bzoxpy (15.7 mg, 50 mmol). The reaction mixture was stirred at room temperature for 2 min and then treated with Et2O (15 mL). The precipitate was decanted, washed twice with Et2O, gently vacuum dried and stored at 20 C. Yield: 25.0 mg (37 mmol, 75%). Ruby red powder. Mp: 145e160 C (dec.). Anal. Calc. for C30H18BF4MoN3O4: C: 54.00; H: 2.72; N: 6.30. Found: 54.18; H: 2.65; N: 6.22. FTIR (ATR-C, cm1): 1968 vs [na(CO)], 1894 vs [ns(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 8.64 (dd, 3J(1H, 1H) ¼ 8.0 Hz, 4J(1H, 1H) ¼ 1.5 Hz, 1H, bzoxpy, H3), 8.42 (t, 3J(1H, 1H) ¼ 7.9 Hz, 1H, bzoxpy, H4), 8.21 (m, 1H, bzoxpy, 0 0 0 0 H4 e7 ), 8.14 (m, 1H, bzoxpy, H4 e7 ), 8.09 (dd, 3J(1H, 1H) ¼ 7.8 Hz, 0 0 4 1 1 5 J( H, H) ¼ 1.5 Hz, 1H, bzoxpy, H ), 7.96 (m, 1H, bzoxpy, H4 e7 ), 7.86 40 e70 (m, 2H of bzoxpy, 1H of Ind), 7.77 (m, 1H, bzoxpy, H ), 7.67 (m, 0 0 2H, bzoxpy, H4 e7 ), 6.89 (m, 2H, Ind, H4e7), 6.62 (m, 1H, Ind, H4e7), 6.46 (s-br, 1H, Ind, H1,3), 6.39 (s-br, 1H, Ind, H1,3), 5.23 (t, 3J(1H, 1 H) ¼ 2.8 Hz, 1H, Ind, H2). Synthesis of [(h5-Ind)Mo(CO)(k3-bzoxpy)][BF4] (18) The reaction was carried out as described for the compound 6 but with [(h5-Ind)Mo(CO)2(NCMe)2][BF4] (2; 21.8 mg, 50 mmol) and bzoxpy (15.7 mg, 50 mmol). The crude product was washed with Et2O, recrystallized twice from CH2Cl2/Et2O and vacuum dried. Yield: 30.1 mg (47 mmol, 94%). Indigo blue powder. Mp: 155e160 C (dec.). Anal. Calc. for C29H18BF4MoN3O3: C: 54.49; H: 2.84; N: 6.57. Found: C: 54.32; H: 2.85; N: 6.54. FTIR (ATR-C, cm1): 1874 vs [n(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 8.56 (d, 3J(1H, 1H) ¼ 7.9 Hz, 2H, 0 0 bzoxpy, H3,5), 8.07 (m, 3H, bzoxpy, H4,4 e7 ), 7.94 (m, 2H, bzoxpy, 40 e70 40 e70 H ), 7.79 (m, 4H, bzoxpy, H ), 6.66 (dd, 3J(1H, 1H) ¼ 6.5 Hz,
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4 1 J( H, 1H) ¼ 3.1 Hz, 2H, Ind, H4e7), 6.64 (t, 3J(1H, 1H) ¼ 3.0 Hz, 1H, Ind, H2), 6.14 (dd, 3J(1H, 1H) ¼ 6.5 Hz, 4J(1H, 1H) ¼ 3.1 Hz, 2H, Ind, H4e7), 5.64 (d, 3J(1H, 1H) ¼ 3.0 Hz, 2H, Ind, H1,3). Single crystals of 18∙CH2Cl2 suitable for the X-ray analysis were prepared by careful overlayering of a CH2Cl2 solution of 18 with hexane.
Synthesis of [(h5-1,3-Ph2C9H5)Mo(CO)(k3-bzoxpy)][BF4] (19) The reaction was carried out as described for the compound 6 but with [(h5-1,3-Ph2C9H5)Mo(CO)2(NCMe)2][BF4] (3; 29.4 mg, 50 mmol) and bzoxpy (15.7 mg, 50 mmol). The crude product was washed with Et2O, recrystallized twice from CH2Cl2/Et2O and vacuum dried. Yield: 36.4 mg (46 mmol, 92%). Indigo blue powder. Mp: 165e170 C (dec.). Anal. Calc. for C41H26BF4MoN3O3: C: 62.22; H: 3.31; N: 5.31. Found: C: 62.46; H: 3.24; N: 5.22. FTIR (ATR-C, cm1): 1889 vs [n(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 8.65 (d, 3J(1H, 1 H) ¼ 7.8 Hz, 2H, bzoxpy, H3,5), 8.26 (t, 3J(1H, 1H) ¼ 7.8 Hz, 1H, bzoxpy, H4), 7.65 (ddd, 3J(1H, 1H) ¼ 8.3 Hz, 4J(1H, 1H) ¼ 0.9 Hz, 5J(1H, 0 0 1 H) ¼ 0.6 Hz, 2H, bzoxpy, H4 ,7 ), 7.58 (ddd, 3J(1H, 1H) ¼ 8.3 Hz, 3J(1H, 0 0 1 4 1 1 H) ¼ 7.2 Hz, J( H, H) ¼ 1.4 Hz, 2H, bzoxpy, H5 ,6 ), 7.5e7.3 (m, 4H 2 of bzoxpy, 10H of Ph), 6.81 (s, 1H, Ind, H ), 6.80 (dd, 3J(1H, 1 H) ¼ 6.8 Hz, 4J(1H, 1H) ¼ 3.2 Hz, 2H, Ind, H4e7), 6.72 (dd, 3J(1H, 1 H) ¼ 6.8 Hz, 4J(1H, 1H) ¼ 3.2 Hz, 2H, Ind, H4e7). X-ray crystallography The X-ray data for the crystals of the compounds 5, 6, 7∙CH2Cl2, 10∙MeCN, 11, 16∙CH2Cl2 and 18∙CH2Cl2 were obtained at 150 K using an Oxford Cryostream low-temperature device on a Nonius KappaCCD diffractometer with Mo Ka radiation (l ¼ 0.71073 Å) and a graphite monochromator. Data reductions were performed with DENZO-SMN [28]. The absorption was corrected by integration methods [29]. Structures were solved by direct methods (Sir92) [30] and refined by full-matrix least squares based on F2 (SHELXL97) [31]. Hydrogen atoms were mostly localized on a difference Fourier map. However, to ensure uniformity of the treatment of the crystal, all hydrogen atoms were recalculated into idealized positions (riding model) and assigned temperature factors Uiso(H) ¼ 1.2[Ueq(pivot atom)] or 1.5Ueq for the methyl moiety with CeH ¼ 0.96, 0.97, and 0.93 Å for methyl, methylene, and hydrogen atoms in aromatic rings or the allyl moiety, respectively. The disordered BF 4 groups in 10∙MeCN and 18∙CH2Cl2 were treated by the standard ISOR restraint available in SHELXL97 program package [31], which caused on the one hand slightly better shape of thermal ellipsoids but on the other hand the increase of the residual electron density in 18∙CH2Cl2. In the structure of 16∙CH2Cl2, the solvent molecule (CH2Cl2) is disordered along the special position and remains untreated. Acknowledgements This work was supported by Ministry of Education of the Czech Republic (Project No. SG320001). Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jorganchem.2014.09.028. References [1] a) S. Trofimenko, Scorpionates: Polypyrazolylborate Ligands and Their Coordination Chemistry, Imperial College Press, London, 1999; b) C. Pettinari, Scorpionates II: Chelating Borate Ligands, Imperial College Press, London, 2008.
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Contents lists available at ScienceDirect
Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem
Cyclopentadienyl and indenyl molybdenum(II) complexes bearing planar N,N,N-chelating ligands b, Jaromír Vinkla rek b, Zden ka R b Jan Honzí cek a, *, Iva Honzí ckova u zi ckova a 573, Pardubice, Institute of Chemistry and Technology of Macromolecular Materials, Faculty of Chemical Technology, University of Pardubice, Studentska Czech Republic b 573, Pardubice, Czech Republic Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentska
a r t i c l e i n f o
a b s t r a c t
Article history: Received 30 July 2014 Received in revised form 9 September 2014 Accepted 23 September 2014 Available online 2 October 2014
The reactivity of cyclopentadienyl and indenyl molybdenum(II) complexes [(h5-Cp0 )Mo(CO)2(NCMe)2] [BF4] (Cp0 ¼ Cp, Ind, 1,3-Ph2C9H5) with a series of planar N,N,N-chelating ligands was scrutinized. The planar N,N,N-chelating ligands give k2-complexes [(h5-Cp0 )Mo(CO)2(k2-N,N,NL)][BF4] those undergo in particular cases a spontaneous release of carbon monoxide to give [(h5-Cp0 )Mo(CO)(k3-N,N,NL)][BF4] depending on several factors including the basicity of the tridentate ligand as well as the nature of the starting molybdenum(II) compound. This behaviour strongly contrasts with tripodal ligands those do not affect cis-Mo(CO)2 moiety even upon tridentate coordination. All structure types, discussed in this work, were elucidated by the spectroscopic measurements as well as by the X-ray crystallography. © 2014 Elsevier B.V. All rights reserved.
Keywords: Molybdenum compounds Indenyl effect Pincer ligands Infrared spectroscopy CO-releasing molecule
Introduction Tridentate ligands have found a wide application in the inorganic chemistry. They cover number of shapes and constrained geometries that strongly affect their coordination ability. Tripodal (so-called “scorpionate”) ligands [1] and planar (so-called “pincer”) ligands [2] represent two most pronounced groups of the tridentate ligands. Their bonding properties are very different. The tripodal ligands were designed for the assembly of fac-complexes [3] while the rigid planar ligands usually give transition metal complexes in a mer-configuration [4]. The restrictions in the coordination sphere of the central metal, possessed by a tridentate ligand, are often used for a tuning of the physical and chemical properties of transition metal compounds that found a number of applications in the catalysis [5] and may serve as a model system for the active site of metalloenzymes [6]. This work will demonstrate that coordination of planar tridentate ligands could stimulate a controlled release of carbon monoxide from molybdenum complexes [(h5-Cp0 ) 0 0 Mo(CO)2(NCMe)2][BF4] (1: Cp ¼ Cp ¼ C5H5, 2: Cp ¼ Ind ¼ C9H7, 3:
* Corresponding author. Fax: þ420 46603 7068. E-mail address: [email protected] (J. Honzí cek). http://dx.doi.org/10.1016/j.jorganchem.2014.09.028 0022-328X/© 2014 Elsevier B.V. All rights reserved.
Cp0 ¼ 1,3-Ph2C9H5), shown in Scheme 1. This behaviour is currently widely scrutinized due to recently recognized therapeutic properties of CO and following comprehensive search for new species enable to deliver CO into diseased cells [7]. Although the starting compounds have similar molecular structure, a different reactivity is expected since the replacement of the cyclopentadienyl ligand with the indenyl accelerates reaction rates due to a lower energetic barrier of the haptotropic shift of the p-ligand [8]. This, so-called “indenyl effect”, was comprehensively scrutinized on various molybdenum compounds [9] and was utilized for an activation of the coordinated ligands [10]. This study is focused mainly on three neutral planar N,N,Nchelating ligands (terpy: 2,20 ;60 ,200 -terpyridine, bzimpy: 2,6bis(benzimidazol-20 -yl)pyridine, bzoxpy: 2,6-bis(benzoxazol-20 yl)pyridine). The structures of the observed reaction products will be confronted with related complexes of neutral tripodal N,N,Nchelating ligand (tpm: tris(pyrazol-1-yl)methane, developed by ~o [11]. It will be demonstrated that the release of carbon Roma monoxide, induced upon the coordination, can be effectively controlled by several factors including shape of the tridentate ligand, basicity of the nitrogen donor atoms and the nature of the starting molybdenum(II) compound. All structure types, discussed in this work, will be supported by X-ray crystallographic data.
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Table 1 Summary of the infrared data for the complexes bearing the planar tridentate ligandsa.
n(CO)
Scheme 1. The starting molybdenum(II) complexes 1e3.
Results and discussion Complexes of 2,20 ;60 ,200 -terpyridine At first, the reactivity of the cyclopentadienyl complex 1 with terpy was studied by 1H NMR spectroscopy. The in situ experiments in the NMR tube revealed an initial formation of the complex with one uncoordinated side arm [(h5-Cp)Mo(CO)2(k2-terpy)][BF4] (4). Such k2-compound is unstable undergoing a spontaneous release of carbon monoxide to give the k3-complex [(h5-Cp)Mo(CO)(k3terpy)][BF4] (5), see Scheme 2. The bonding mode of the terpy ligand was easily recognized by 1 H NMR spectroscopy since the k2-intermediate (4) is C1-symmetric while the k3-product (5) belongs to the point group Cs. For this purpose, resonances of the protons from the central pyridine ring could be taken as diagnostic. Hence, 1H NMR spectrum of the k30 0 complex (5) show one doublet at 8.63 ppm (H3 ,5 ) and one triplet at 40 8.16 ppm (H ) that is proving the equivalency of the protons in 3and 5-position in the central pyridine ring. In a lower symmetric k2complex (4), these positions are not equivalent that results in the 0 0 appearance of three resonances. Signals of the protons H3 and H4 3 were observed at a similar field as in case of the k -complex (5) 0 while the proton beside the uncoordinated arm (H5 ) appears at a 3 much higher field (7.53 ppm). The k -complex 5 was isolated and the loss of one carbonyl ligand was confirmed through the appearance of only one CO stretching band in the infrared spectrum [n(CO) ¼ 1809 cm1]. Unfortunately, the isolation of the pure intermediate 4 was not successful owing to its spontaneous decomposition giving 5 upon handling. In the next stage, a reaction of the indenyl molybdenum complexes 2 and 3 with terpy was studied. It gives, after similar work up as before, the products of decarbonylation [(h5-Ind)Mo(CO)(k3terpy)][BF4] (6) and [(h5-1,3-Ph2C9H5)Mo(CO)(k3-terpy)][BF4] (7), respectively (Scheme 2). The k3-coordination mode in these species was elucidated from the 1H NMR spectra similarly as in case of the cyclopentadienyl analogue (5). The proposed structures are further supported by the appearance of only one CO stretching band in region of the terminal carbonyl groups, see Table 1. The successive
Scheme 2. The reaction of molybdenum complexes 1e3 with terpy. Reagents and conditions: (a) terpy/CH2Cl2/16 h (b) MeCN/7 days.
5 6 7 12 13 14 15 16 17 18 19 a
1809 1835 1847 1965, 1841, 1844 1847 1975, 1968, 1874 1889
1885 1818
1894 1894
The frequencies are given in cm1.
growth of the CO stretching energy from the cyclopentadienyl complex (5) over the indenyl (6) to the 1,3-diphenylindenyl analogues (7) is due to a decreasing back-bonding from the molybdenum atom to the carbonyl ligands. It reflects the decrease of the electron density on the molybdenum atom since the phenyl substituents as well as the annulated benzene ring have electronwithdrawing properties. Further 1H NMR experiments reveal that the formation of the indenyl complexes 6 and 7 proceeds much faster than in case of the cyclopentadienyl analogue 5. The reactions giving compounds 6 and 7 are complete immediately after dissolution of the starting material in CD2Cl2. At this stage, the cyclopentadienyl analogue (1) stays fully unreacted. An apparent formation of the intermediate 4 was observed in terms of hours. The crystal structures of the compounds 5e7 were determined by X-ray diffraction analysis. The cationic complexes have a squarepyramidal structure with the h5-bonded cyclopentadienyl or indenyl ligand in the apical position. The basal plane is occupied with one carbonyl ligand and three nitrogen donor atom of the terpy, see Figs. 1e3. The bond distances between molybdenum and centroid of the C5-ring (MoeCg) were found to be in a narrow range 1.995(2)e2.024(1) Å. The MoeC(CO) bond lengths vary between 1.927(3) and 1.934(2) Å. The MeN bonds to the central pyridine ring of the terpy ligand are significantly shorter [MoeN: 2.092(2)e
Fig. 1. ORTEP drawing of cationic complex [(h5-Cp)Mo(CO)(k3-terpy)]þ present in the crystal structure of 5. The labelling scheme for all non-hydrogen atoms is shown. The thermal ellipsoids are drawn at the 30% probability level. Only one of two crystallographically independent cations is shown for clarity.
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Table 2 Selected bond lengths of the complexes bearing terpya.
MoeC(CO) MoeCg(Cp0 )d MoeN
Ue D(MeC)f
5b
5c
6
7∙CH2Cl2
1.929(3) 1.996(2) 2.107(2) 2.168(2) 2.182(2) e e
1.927(3) 1.995(2) 2.107(2) 2.178(2) 2.182(2) e e
1.933(2) 2.006(1) 2.096(2) 2.167(2) 2.176(2) 4.4(2) 0.129(2)
1.934(2) 2.024(1) 2.092(2) 2.156(2) 2.175(2) 2.0(2) 0.103(2)
a
The distances are given in Å. Molecule A in unit cell. c Molecule B in unit cell. d The centroid of five carbon atoms of h5-Cp0 . e U is the envelop fold angle defined for the indenyl ligand as the angle between planes defined by C1, C2 and C3 and that of C1, C3, C8 and C9 [13]. f D(MeC) represents the differences in the metal-carbon bonds. It is defined for the indenyl compounds as the difference between the averages of the metal-carbon distances MeCl, MeC2, and MeC3 and those of MeC8 and MeC9 [13]. b
Fig. 2. ORTEP drawing of the cationic complex [(h5-Ind)Mo(CO)(k3-terpy)]þ present in the crystal structure of 6. The labelling scheme for all non-hydrogen atoms is shown. The thermal ellipsoids are drawn at the 30% probability level.
2.107(2) Å] than those to the side pyridine rings [MoeN: 2.156(2)e 2.182(2) Å], see Table 2. This observation well correlates with the previous studies on the homoleptic terpyridine complexes [M(terpy)3] (M ¼ Ti, V, Cr, Mo, W] [12]. The low values of U and D(MeC) observed for the indenyl ligands in the complexes 6 and 7 (see Table 2) are in line with the expected h5-coodination mode. No significant close contacts between complex cations and tetrafluoroborate anion were observed. Although observed k3-coordination mode of terpy, in the compounds 5e7, seems to be obvious, here observed CO loss is rather anomalous. Hence, 2,20 -bipyridine complexes [(h5-Cp0 ) 0 Mo(CO)2(bpy)][BF4] (8: Cp ¼ Cp; 9: Ind), those could be taken as satisfactory model systems for the k2-terpy intermediates, show relatively low frequencies of CO stretching [8: na(CO) ¼ 1973 cm1,
Fig. 3. ORTEP drawing of the cationic complex [(h5-1,3-Ph2C9H5)Mo(CO)(k3-terpy)]þ present in the crystal structure of 7∙CH2Cl2. The labelling scheme for all non-hydrogen atoms is shown. The thermal ellipsoids are drawn at the 30% probability level.
ns(CO) ¼ 1901 cm1, 9: na(CO) ¼ 1974 cm1, ns(CO) ¼ 1878 cm1] [14] that is usually not compatible with CO release under mild conditions without photochemical activation [15]. Strong bonding of carbonyl ligands was also observed in case of cyclopentadienyl and indenyl complexes bearing tripodal N,N,N-chelating ligands: [(h5-Cp)Mo(CO)2(k2-tpm)][BF4] (10), [(h3-Ind)Mo(CO)2(k3-tpm)] [BF4] (11) those were synthesized similarly by ligand exchange reaction from 1 and 2, respectively [11]. Our experiments with these species have confirmed their stability under ambient conditions and were utilized for preparation of single crystals suitable for elucidation of their structures by X-ray crystallography. X-ray structures of tris(pyrazol-1-yl)methane complexes The cyclopentadienyl compound [(h5-Cp)Mo(CO)2(k2-tpm)] [BF4] (10) has a square-pyramidal structure with the h5-coordinated Cp ligand in the apical position. Two carbonyl ligands and two nitrogen donor atoms of tpm form the basal plane (Fig. 4). The geometric parameters describing the coordination sphere of the molybdenum atom are summarized in Table 3. The coordinated pyrazolyl rings in the cation of 4 are not coplanar [PlN1eN2PlN3eN4 ¼ 33.66(14) ] due to sp3-hybridization on the
Fig. 4. ORTEP drawing of the cationic complex [(h5-Cp)Mo(CO)2(k2-tpm)]þ present in the crystal structure of 10∙MeCN. The labelling scheme for all non-hydrogen atoms is shown. The thermal ellipsoids are drawn at the 30% probability level.
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302
Table 3 Selected bond lengths of the complexes bearing tpma.
MoeC(CO) MoeCg(Cp0 )b MoeN
Uc D(MeC)c a b c d
10∙MeCN
11
1.963(2) 1.971(3) 1.986(1) 2.221(2) 2.223(2) 4.120(2)d e e
1.961(2) 1.964(2) 2.116(2) 2.183(2) 2.256(2) 2.274(2) 21.9(2) 0.815(2)
The distances are given in Å. The centroid of five carbon atoms of h5-Cp or three carbon atoms of h3-Ind. For definition see footnote of Table 2. Non-bonding distance Mo/N. Scheme 3. The reaction of the molybdenum complexes 1e3 with bzimpy. Reagents and conditions: (a) bzimpy/CH2Cl2/16 h (b) MeOH/7 days.
bridging carbon. The MoeN bond lengths are longer [2.221(2); 2.223(2) Å] than usual for isostructural complexes with fivemembered chelate rings [2.173(3)e2.194(4) Å] [14,16]. The remaining pyrazolyl ring stays outside the coordination sphere of the molybdenum below Mo(CO)2 moiety; almost coplanar with it. The nonbonding distance Mo1/N6 was found to be 4.120(2) Å. The indenyl compound [(h3-Ind)Mo(CO)2(k3-tpm)][BF4] (11) has a distorted octahedral structure with the h3-coordinated indenyl and one nitrogen donor atom of tpm in the axial positions. The equatorial positions are occupied with two remaining nitrogen donor atoms and two carbonyl groups, see Fig. 5. The coordination sphere of molybdenum resembles the isoelectronic tris(pyrazol-1-yl)borate analogue [(h3-Ind)Mo(CO)2 (k3-Tp)] reported earlier [17]. The h3-coordination mode of the indenyl ligand is confirmed by high values of the envelop fold angle [U ¼ 21.9(2) ] and D(MeC) [0.815(2) Å]. The MoeN bond to the axial nitrogen atom was found to be considerably shorter [2.183(2) Å] than to the equatorial nitrogen atoms [2.256(2) and 2.274(2) Å]. This distortion is caused by a trans-effect of the carbonyl ligands [18] as was previously demonstrated on several pseudooctahedral molybdenum(II) complexes [17,19]. No significant close contacts between complex cations (10 and 11) and tetrafluoroborate anion were observed.
Fig. 5. ORTEP drawing of the cationic complex [(h3-Ind)Mo(CO)(k3-tpm)]þ present in the crystal structure of 11. The labelling scheme for all non-hydrogen atoms is shown. The thermal ellipsoids are drawn at the 30% probability level.
Complexes of 2,6-bis(benzimidazol-20 -yl)pyridine and 2,6bis(benzoxazol-20 -yl)pyridine Finally, the high stability of tpm complexes 10 and 11 suggests that similar species may appear upon reaction with planar tridentate ligands as intermediates. The attempts to stabilize supposed intermediates led us to another N,N,N-chelating ligands. Bzimpy and bzoxpy were selected mainly due to a different basicity of the heterocycles in the side arms. The nitrogen donor atom of benzimidazole shows similar basicity as pyridine while benzoxazole is much less basic [20]. Furthermore, the use of symmetrical ligands facilitates the NMR spectra assignment since the expected k2-complexes are C1-symmetric while the k3-complexes Cs-symmetric. The protons of the pyridine ring could be taken as a diagnostic tool, similarly as was described in detail for the terpy complexes. Bzimpy reacts with the cyclopentadienyl precursor 1 to give the k2-complex [(h5-Cp)Mo(CO)2(k2-bzimpy)][BF4] (12). This compound seems to be stable but the dissolution in highly polar solvents such as methanol induces the gradual release of carbon monoxide to give the k3-complex [(h5-Cp)Mo(CO)(k3-bzimpy)][BF4] (13), see Scheme 3. The indenyl compounds 2 and 3 give the
Scheme 4. The reaction of the molybdenum complexes 1e3 with bzoxpy. Reagents and conditions: (a) bzoxpy/CH2Cl2. (b) stirring for 16 h.
J. Honzícek et al. / Journal of Organometallic Chemistry 772-773 (2014) 299e306
expected k3-complexes [(h5-Ind)Mo(CO)(k3-bzimpy)][BF4] (14) and [(h5-1,3-Ph2C9H5)Mo(CO)(k3-bzimpy)][BF4] (15), respectively. Unfortunately, the very low solubility of bzimpy and its complexes disables using standard solution NMR techniques for a detailed investigation of the reaction mechanism. The reaction of bzoxpy with the cyclopentadienyl complex 1 gives stable k2-complex [(h5-Cp)Mo(CO)2(k2-bzoxpy)][BF4] (16) that correlates with a lower basicity of nitrogen in the side arms of this tridentate ligand. The indenyl precursors 2 and 3 produce, after the standard work up, the k3-complexes [(h5-Ind)Mo(CO)(k3bzoxpy)][BF4] (18) and [(h5-1,3-Ph2C9H5)Mo(CO)(k3-bzoxpy)][BF4] (19), respectively (see Scheme 4). Nevertheless, following the reaction of 2 with bzoxpy has revealed the appearance of C1-symmetric complex species that was assigned to above postulated k2intermediate [(h5-Ind)Mo(CO)2(k2-bzoxpy)][BF4] (17). This species is formed quantitatively immediately after the dissolution of the starting compounds in CD2Cl2. A pure sample of the compound 17 was isolated using a modified synthetic procedure. The proposed structure of 17 was further supported by the infrared spectroscopy since two CO stretching bands were observed at 1968 cm1 and 1894 cm1. These frequencies near the values for the aforementioned 2,20 -bipyridine analogue [(h5-Ind)Mo(CO)2(bpy)][BF4] (9) that implies similar strength of the bonds MoeCO. Thus, the much lower stability of 17 toward CO release is apparently not caused by weaker bonding of the carbonyl ligand but the result of the very strong enforcing properties of the tridentate ligand side arm. In contrast to fac-enforcing tpm, the reaction of bzoxpy with indenyl compounds 2 and 3 does not give any stable intermediates with slipped indenyl ring as confirmed by our 1H NMR experiments. This is very surprising mainly in the light of fact that a related isostructural h3-allyl compound mer-[(h3-2-MeC3H4) Mo(CO)2(k3-terpy)][OTf] is a stable compound and reported frequencies of CO stretching bands (1965, 1874 cm1) do not suggest the activation of the MoeCO bond [21]. The crystal structures of two compounds bearing bzoxpy ligand, 16∙CH2Cl2 and 18∙CH2Cl2, were determined by X-ray diffraction analysis. These cationic compounds have a square-pyramidal structure with the h5-coordinated ligand in the apical position while the planar square is occupied with the carbonyl ligands and the nitrogen donor atoms of the tridentate ligand. The geometric parameters describing the coordination sphere of the molybdenum atom are given in Table 4. No significant close contacts between complex cation and tetrafluoroborate anion were observed. The compound 16∙CH2Cl2 bears two carbonyl ligands and k2coordinated bzoxpy, see Fig. 6. The MoeN bond lengths to coordinated pyridine and benzoxazole are 2.278(2) and 2.166(3) Å, respectively. The non-bonding distance Mo/N to the uncoordinated benzoxazole arm is 3.767(4) Å.
303
Fig. 6. ORTEP drawing of cationic complex [(h5-Cp)Mo(CO)2(k2-bzoxpy)]þ present in the crystal structure of 16∙CH2Cl2. The labelling scheme for all non-hydrogen atoms is shown. The thermal ellipsoids are drawn at the 20% probability level.
The compound 18∙CH2Cl2 bears one carbonyl ligand and k3coordinated bzoxpy, see Fig. 7. The coordination of the second benzoxazole side arm causes significant shortening of the MoeN bond to coordinated pyridine [2.104(5); 2.118(5) Å]. Similarly as observed for the isostructural terpyridine complexes (5, 6 and 7∙CH2Cl2), these bonds are considerably shorter than in case of the side heterocyclic arms [2.133(5)e2.168(5) Å]. Conclusions Here presented study clearly demonstrates that the reactions of cyclopentadienyl and indenyl molybdenum compounds (1e3) with planar N,N,N-chelating ligands could be used for the assembly of metastable k2-complexes those are able to release carbon monoxide. Stability of these compounds is controlled by several factors including basicity of the nitrogen donor atoms and a barrier of haptotropic rearrangement of the coordinated p-ligand. The shape of the tridentate ligand seems to be crucial for the activation of MoeCO bond since complexes bearing tripodal ligands are stable as reported in literature [11] and further confirmed by our experiments. The newly synthesized complexes with k3-coordinated tridentate ligand, appearing upon CO release, are unprecedented. The donor strength of the coordinated tridentate ligands well correlates with the energy of CO stretching mode. Hence, a coordination of weakly-donating bzoxpy (in 18 and 19) is reflected in higher frequencies of n(CO) than observed for their terpy (6, 7) and bzimpy counterparts (14, 15), see Table 1.
Table 4 Selected bond lengths of the complexes bearing bzoxpya.
MoeC(CO) MoeCg(Cp0 )d MoeN
Ue D(MeC)e a b c d e f
16∙CH2Cl2
18∙CH2Cl2b
18∙CH2Cl2c
1.968(3) 1.977(4) 1.989(2) 2.166(3) 2.278(2) 3.767(4)f e e
1.950(7)
1.962(7)
1.990(3) 2.118(5) 2.157(5) 2.168(5) 3.5(7) 0.096(7)
1.988(2) 2.104(5) 2.133(5) 2.163(5) 4.6(5) 0.134(5)
The distances are given in Å. Molecule A in unit cell. Molecule B in unit cell. The centroid of five carbon atoms of h5-Cp0 . For definition see footnote of Table 2. Non-bonding distance Mo/N.
Fig. 7. ORTEP drawing of cationic complex [(h5-Ind)Mo(CO)(k3-bzoxpy)]þ present in the crystal structure of 18∙CH2Cl2. The labelling scheme for all non-hydrogen atoms is shown. The thermal ellipsoids are drawn at the 20% probability level. Only one of two crystallographically independent cations is shown for clarity.
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The effect of the coordinated p-ligand is following. The low energetic barrier of the h5eh3 indenyl ligand rearrangement strongly accelerates the rate of the chelating ligand coordination as well as the CO release. It results in much lower stability of the indenyl complexes bearing k2-coordinated planar N,N,N-chelating ligand. Nevertheless, the complexes with weakly-donating tridentate ligands (e.g. 17 bearing bzoxpy) are enough stable for ongoing experimental studies. The substitution in the indenyl ligand with the phenyl groups has much smaller effect on the reactivity than expected. At the same reaction conditions, the compounds 2 and 3 give analogous products. A different outcome is expected for more sterically hindered tridentate ligands but these were not scrutinized here. Experimental section General considerations All operations were performed under a nitrogen atmosphere using conventional Schlenk-line techniques. The solvents were purified and dried by standard methods [22]. The starting materials were available commercially or prepared according to the procedures published elsewhere: tpm [23], bzimpy [24], bzoxpy [25], [(h5-Cp)Mo(CO)2(NCMe)2][BF4] (1) [16], [(h5-Ind)Mo(CO)2(NCMe)2] [BF4] (2) [26], [(h5-1,3-Ph2C9H5)Mo(CO)2(NCMe)2][BF4] (3) [27], [(h5-Cp)Mo(CO)2(k2-tpm)][BF4] (10) [11], [(h3-Ind)Mo(CO)2(k3tpm)][BF4] (11) [11]. The infrared spectra were recorded in the 4000e400 cm1 region (resolution 2 cm1) on a Nicolet Magna 6700 FTIR spectrometer using a Diamond Smart Orbit ATR. 1H and 13 1 C{ H} NMR spectra were measured in CDCl3, CD2Cl2, acetone-d6, MeCN-d3, methanol-d4 or DMSO-d6 solutions on a Bruker Avance 400 spectrometer at room temperature. The chemical shifts are given in ppm relative to TMS. Characterization of 2,6-bis(benzimidazol-20 -yl)pyridine (bzimpy) 1 H NMR (acetone-d6, 400 MHz, d ppm): 8.48 (d, 3J(1H, H) ¼ 7.8 Hz, 2H, H3,5), 8.21 (t, 3J(1H, 1H) ¼ 7.8 Hz, 1H, H4), 7.78 (s-br, 0 0 0 0 0 0 2H, H4 e7 ), 7.66 (s-br, 2H, H4 e7 ), 7.30 (s-br, 4H, H4 e7 ). 1H NMR 6 3 1 1 (DMSO-d , 400 MHz, d ppm): 8.34 (d, J( H, H) ¼ 7.8 Hz, 2H, H3,5), 0 0 8.15 (t, 3J(1H, 1H) ¼ 7.8 Hz, 1H, H4), 7.76 (m, 4H, H4 e7 ), 7.30 (m, 4H, 40 e70 H ). 1
Characterization of 2,6-bis(benzoxazol-20 -yl)pyridine (bzoxpy) 1
H NMR (CDCl3, 400 MHz, d ppm): 8.53 (d, 3J(1H, 1H) ¼ 7.9 Hz, 0 0 2H, H3,5), 8.11 (t, 3J(1H, 1H) ¼ 7.9 Hz, 1H, H4), 7.86 (m, 2H, H4 e7 ), 7.73 40 e70 40 e70 1 6 (m, 2H, H ), 7.43 (m, 4H, H ). H NMR (acetone-d , 400 MHz, d ppm): 8.61 (d, 3J(1H, 1H) ¼ 7.9 Hz, 2H, H3,5), 8.34 (t, 3J(1H, 0 0 0 0 1 H) ¼ 7.9 Hz, 1H, H4), 7.89 (m, 4H, H4 e7 ), 7.53 (m, 4H, H4 e7 ). Reaction of [(h5-Cp)Mo(CO)2(NCMe)2][BF4] (1) with 2,20 ;60 ,200 terpyridine (terpy) [(h5-Cp)Mo(CO)2(NCMe)2][BF4] (1; 19.3 mg, 50 mmol) was dissolved in CH2Cl2 (15 mL) and treated with terpy (11.7 mg, 50 mmol). The reaction mixture was stirred at room temperature overnight. Volatiles were vacuum evaporated. A recrystallization from CH2Cl2/ Et2O gives 1:2 mixture of [(h5-Cp)Mo(CO)2(k2-terpy)][BF4] (4) and [(h5-Cp)Mo(CO)(k3-terpy)][BF4] (5). Prolonged stirring of the mixture in MeCN followed with a recrystallization from MeCN/Et2O gives the analytically pure sample of the compound 5. 4: 1H NMR (MeCN-d3, 400 MHz, d ppm, from the mixtures with 5): 8.98 (ddd, 3 1 J( H, 1H) ¼ 5.8 Hz, 4J(1H, 1H) ¼ 1.5 Hz, 5J(1H, 1H) ¼ 0.8 Hz, 1H, terpy, H6), 8.82 (ddd, 3J(1H, 1H) ¼ 4.9 Hz, 4J(1H, 1H) ¼ 1.8 Hz, 5J(1H,
1
00
H) ¼ 1.0 Hz, 1H, terpy, H6 ), 8.65 (dd, 3J(1H, 1H) ¼ 8.3 Hz, 4J(1H, 0 00 H) ¼ 1.4 Hz, 1H, terpy, H3 ), 8.61 (m, 1H, terpy H3,5,5 ), 8.26 (dd, 3 1 1 3 1 1 40 J( H, H) ¼ 7.6 Hz, J( H, H) ¼ 8.3 Hz, 1H, terpy, H ), 8.21 (ddd, 3 1 J( H, 1H) ¼ 8.3 Hz, 3J(1H, 1H) ¼ 7.5 Hz, 4J(1H, 1H) ¼ 1.5 Hz, 1H, terpy, 00 H4), 8.02 (td, 3J(1H, 1H) ¼ 7.8 Hz, 4J(1H, 1H) ¼ 1.8 Hz, 1H, terpy, H4 ), 3 1 1 4 1 1 5 1 1 7.66 (dt, J( H, H) ¼ 7.8 Hz, J( H, H) ¼ 1.0 Hz, J( H, H) ¼ 1.0 Hz, 00 00 1H, terpy, H3 ), 7.59e7.55 (m, 2H, terpy H3,5,5 ), 7.53 (dd, 3J(1H, 1 4 1 1 50 H) ¼ 8.3 Hz, J( H, H) ¼ 1.4 Hz, 1H, terpy, H ), 5.50 (s, 5H, Cp). 5: Yield: 15.5 mg (30 mmol, 61%). Violet powder. Mp: 150e165 C (dec.). Anal. Calc. for C21H16BF4MoN3O: C: 49.54; H: 3.17; N: 8.25. Found: C: 49.37; H: 3.26; N: 8.18. FTIR (ATR-C, cm1): 1809 vs [n(CO)]. 1H NMR (MeCN-d3, 400 MHz, d ppm): 9.03 (ddd, 3J(1H, 00 1 H) ¼ 5.8 Hz, 4J(1H, 1H) ¼ 1.4 Hz, 5J(1H, 1H) ¼ 0.9 Hz, 2H, terpy, H6,6 ), 3 1 1 4 1 1 5 1 1 8.67 (ddd, J( H, H) ¼ 8.3 Hz, J( H, H) ¼ 1.4 Hz, J( H, H) ¼ 0.9 Hz, 00 0 0 2H, terpy, H3,3 ), 8.63 (d, 3J(1H, 1H) ¼ 8.0 Hz, 2H, terpy, H3 ,5 ), 8.16 (t, 3 1 1 40 3 1 1 J( H, H) ¼ 8.0 Hz, 1H, terpy, H ), 8.06 (ddd, J( H, H) ¼ 8.3 Hz, 00 3 1 J( H, 1H) ¼ 7.4 Hz, 4J(1H, 1H) ¼ 1.4 Hz, 2H, terpy, H4,4 ), 7.39 (ddd, 3 1 1 3 1 1 4 1 1 J( H, H) ¼ 7.4 Hz, J( H, H) ¼ 5.8 Hz, J( H, H) ¼ 1.4 Hz, 2H, terpy, 00 H5,5 ), 5.07 (s, 5H, Cp). 13C NMR (MeCN-d3, 101 MHz, d ppm): 240.5 (1C, CO), 157.2 (2C, tpy), 155.9 (2Cipso, tpy), 148.9 (2Cipso, tpy), 137.5 (2C, tpy), 134.6 (2Cipso, tpy), 125.1 (2C, tpy), 123.9 (2C, tpy), 122.6 (2C, tpy), 98.6 (5C, Cp). Single crystals of 5 suitable for the X-ray analysis were prepared by careful overlayering of a MeCN solution with Et2O. 1
Synthesis of [(h5-Ind)Mo(CO)(k3-terpy)][BF4] (6) [(h5-Ind)Mo(CO)2(NCMe)2][BF4] (2; 21.8 mg, 50 mmol) was dissolved in CH2Cl2 (15 mL) and treated with terpy (11.7 mg, 50 mmol). The reaction mixture was stirred at room temperature overnight. Volatiles were vacuum evaporated. The crude product was washed with Et2O, recrystallized from MeCN/Et2O, CH2Cl2/Et2O and vacuum dried. Yield: 27.4 mg (49 mmol, 98%). Violet powder. Mp: 155e165 C (dec.). Anal. Calc. for C25H18BF4MoN3O: C: 53.70; H: 3.24; N: 7.51. Found: C: 53.65; H: 3.22; N: 7.59. FTIR (ATR-C, cm1): 1835 vs [n(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 9.26 (ddd, 3J(1H, 00 1 H) ¼ 5.9 Hz, 4J(1H, 1H) ¼ 1.4 Hz, 5J(1H, 1H) ¼ 0.8 Hz, 2H, terpy, H6,6 ), 8.54 (ddd, 3J(1H, 1H) ¼ 8.2 Hz, 4J(1H, 1H) ¼ 1.4 Hz, 5J(1H, 1H) ¼ 0.8 Hz, 00 0 0 2H, terpy, H3,3 ), 8.48 (d, 3J(1H, 1H) ¼ 8.0 Hz, 2H, terpy, H3 ,5 ), 8.08 (t, 3 1 1 40 3 1 1 J( H, H) ¼ 8.0 Hz, 1H, terpy, H ), 8.03 (ddd, J( H, H) ¼ 8.2 Hz, 00 3 1 J( H, 1H) ¼ 7.4 Hz, 4J(1H, 1H) ¼ 1.4 Hz, 2H, terpy, H4,4 ), 7.40 (ddd, 3 1 1 3 1 1 4 1 1 J( H, H) ¼ 7.4 Hz, J( H, H) ¼ 5.8 Hz, J( H, H) ¼ 1.4 Hz, 2H, terpy, 00 H5,5 ), 6.50 (dd, 3J(1H, 1H) ¼ 6.5 Hz, 4J(1H, 1H) ¼ 3.0 Hz, 2H, Ind, 4e7 H ), 6.39 (t, 3J(1H, 1H) ¼ 3.0 Hz, 1H, Ind, H2), 6.13 (dd, 3J(1H, 1 H) ¼ 6.5 Hz, 4J(1H, 1H) ¼ 3.0 Hz, 2H, Ind, H4e7), 5.34 (d, 3J(1H, 1 H) ¼ 3.0 Hz, 2H, Ind, H1,3). Single crystals of 6 suitable for the X-ray analysis were prepared by careful overlayering of a CH2Cl2 solution with hexane. Synthesis of [(h5-1,3-Ph2C9H5)Mo(CO)(k3-terpy)][BF4] (7) The reaction was carried out as described for the compound 6 but with [(h5-1,3-Ph2C9H5)Mo(CO)2(NCMe)2][BF4] (3; 29.4 mg, 50 mmol) and terpy (11.7 mg, 50 mmol). The crude product was washed with Et2O, recrystallized twice from CH2Cl2/Et2O and vacuum dried. Yield: 32.7 mg (46 mmol, 92%). Violet powder. Mp: 155e165 C (dec.). Anal. Calc. for C37H26BF4MoN3O: C: 62.47; H: 3.68; N: 5.91. Found: C: 62.28; H: 3.56; N: 5.83. FTIR (ATR-C, cm1): 1847 vs [n(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 8.57 (d, 3J(1H, 00 1 H) ¼ 5.8 Hz, 2H, terpy, H6,6 ), 8.52 (d, 3J(1H, 1H) ¼ 8.0 Hz, 2H, terpy, 00 30 ,50 3 1 1 H ), 8.46 (d, J( H, H) ¼ 8.2 Hz, 2H, terpy, H3,3 ), 8.18 (t, 3J(1H, 1 40 3 1 1 H) ¼ 8.0 Hz, 1H, terpy, H ), 7.82 (ddd, J( H, H) ¼ 8.2 Hz, 3J(1H, 00 1 H) ¼ 7.4 Hz, 4J(1H, 1H) ¼ 1.4 Hz, 2H, terpy, H4,4 ), 7.37 (s-br, 10H, Ph), 6.85 (ddd, 3J(1H, 1H) ¼ 7.4 Hz, 3J(1H, 1H) ¼ 5.8 Hz, 4J(1H, 00 1 H) ¼ 1.4 Hz, 2H, terpy, H5,5 ), 6.79 (s, 1H, Ind, H2), 6.65 (m, 4H, Ind,
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H4e7). Single crystals of 7∙CH2Cl2 suitable for the X-ray analysis were prepared by careful overlayering of a CH2Cl2 solution of 7 with hexane. Single crystals of [(h5-Cp)Mo(CO)2(k2-tpm)][BF4]∙MeCN (10∙MeCN) Single crystals of 10∙MeCN suitable for the X-ray analysis were prepared by careful overlayering of a MeCN solution of 10 with Et2O. Single crystals of [(h3-Ind)Mo(CO)2(k3-tpm)][BF4] (11) Single crystals of 11 suitable for the X-ray analysis were prepared by careful overlayering of a MeCN solution of the starting compound 2 with a thin layer of Et2O. This system was immediately overlayered with a solution of tpm in Et2O. Synthesis of [(h5-Cp)Mo(CO)2(k2-bzimpy)][BF4] (12) [(h5-Cp)Mo(CO)2(NCMe)2][BF4] (1; 38.6 mg, 100 mmol) was dissolved in CH2Cl2 (30 mL) and treated with bzimpy (31.1 mg, 100 mmol). The reaction mixture was stirred at room temperature overnight, filtered over a short pad of a glass wool and volatiles were vacuum evaporated. The crude product was washed with Et2O, recrystallized twice from CH2Cl2/Et2O and vacuum dried. Yield: 53.1 mg (86 mmol, 86%). Ruby red powder. Mp: 150e160 C (dec.). Anal. Calc. for C26H18BF4MoN5O2: C: 50.76; H: 2.95; N: 11.38. C: 50.90; H: 2.85; N: 11.32. FTIR (ATR-C, cm1): 3290 m-br [n(NeH)], 1965 vs [na(CO)], 1885 vs [ns(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 12.66 (s, 1H, bzimpy, NH), 12.15 (s, 1H, bzimpy, NH), 8.71 (d, 3J(1H, 1H) ¼ 7.8 Hz, 1H, bzimpy, H3), 8.12 (t, 3J(1H, 1 H) ¼ 7.9 Hz, 1H, bzimpy, H4), 7.89 (d, 3J(1H, 1H) ¼ 8.0 Hz, 1H, 0 0 bzimpy, H5), 7.85e7.42 (m, 8H, bzimpy, H4 e7 ), 5.65 (s, 5H, Cp). Synthesis of [(h5-Cp)Mo(CO)(k3-bzimpy)][BF4] (13) [(h5-Cp)Mo(CO)2(k2-bzimpy)][BF4] (12; 30.8 mg, 50 mmol) was dissolved in methanol (15 mL) and stirred for 7 days. Volatiles were vacuum evaporated and the crude product was washed with Et2O, CH2Cl2 and vacuum dried. Yield: 25.7 mg (44 mmol, 88%). Indigo blue powder. Mp: 150e160 C (dec.). Anal. Calc. for C25H18BF4MoN5O: C: 51.14; H: 3.09; N: 11.93. C: 50.95; H: 3.27; N: 12.13. FTIR (ATR-C, cm1): 1841 vs [n(CO)], 1818 vs [n(CO)]. 1H NMR (methanol-d4, 400 MHz, d ppm): 8.41 (d, 3J(1H, 1H) ¼ 7.9 Hz, 2H, bzimpy, H3,5), 8.03 (t, 3J(1H, 1H) ¼ 7.9 Hz, 1H, bzimpy, H4), 7.92 (d, 0 0 3 1 J( H, 1H) ¼ 7.7 Hz, 2H, bzimpy, H4 ,7 ), 7.76 (d, 3J(1H, 1H) ¼ 8.0 Hz, 0 0 40 ,70 2H, bzimpy, H ), 7.55 (m, 4H, bzimpy, H5 ,6 ), 5.09 (s, 5H, Cp). Synthesis of [(h5-Ind)Mo(CO)(k3-bzimpy)][BF4] (14) The reaction was carried out as described for the compound 6 but with [(h5-Ind)Mo(CO)2(NCMe)2][BF4] (2; 21.8 mg, 50 mmol) and bzimpy (15.6 mg, 50 mmol). The crude product was washed with Et2O, recrystallized twice from CH2Cl2/Et2O and vacuum dried. Yield: 22.9 mg (36 mmol, 72%). Indigo blue powder. Mp: 160e170 C (dec.). Anal. Calc. for C29H20BF4MoN5O: C: 54.66; H: 3.16; N: 10.99. Found: C: 54.83; H: 3.19; N: 11.04. FTIR (ATR-C, cm1): 3260 m-br [n(NeH)], 1844 vs [n(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 11.70 (s, 2H, bzimpy, NH), 8.09 (d, 3J(1H, 1H) ¼ 7.8 Hz, 2H, bzimpy, H3,5), 7.79 (d, 0 0 3 1 J( H, 1H) ¼ 8.0 Hz, 2H, bzimpy, H4 ,7 ), 7.59 (d, 3J(1H, 1H) ¼ 8.0 Hz, 2H, 0 0 40 ,70 bzimpy, H ), 7.40 (m, 5H, bzimpy, H4,4 ,5 ), 6.38 (t, 3J(1H, 1 2 3 1 1 H) ¼ 2.9 Hz, 1H, Ind, H ), 6.26 (dd, J( H, H) ¼ 6.5 Hz, 4J(1H, 1 H) ¼ 3.0 Hz, 2H, Ind, H4e7), 5.70 (dd, 3J(1H, 1H) ¼ 6.5 Hz, 4J(1H, 1 H) ¼ 3.0 Hz, 2H, Ind, H4e7), 5.12 (d, 3J(1H, 1H) ¼ 2.9 Hz, 2H, Ind, H1,3).
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Synthesis of [(h5-1,3-Ph2C9H5)Mo(CO)(k3-bzimpy)][BF4] (15) The reaction was carried out as described for the compound 6 but with [(h5-1,3-Ph2C9H5)Mo(CO)2(NCMe)2][BF4] (3; 29.4 mg, 50 mmol) and bzimpy (15.6 mg, 50 mmol). The crude product was washed with Et2O, recrystallized twice from CH2Cl2/Et2O and vacuum dried. Yield: 31.3 mg (40 mmol, 79%). Indigo blue powder. Mp: 160e170 C (dec.). Anal. Calc. for C41H28BF4MoN5O: C: 62.38; H: 3.58; N: 8.87. Found: C: 62.26; H: 3.35; N: 8.97. FTIR (ATR-C, cm1): 3265 m-br [n(NeH)], 1847 vs [n(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 11.50 (s, 2H, bzimpy, NH), 8.25 (d, 3J(1H, 1H) ¼ 8.0 Hz, 2H, bzimpy, H3,5), 7.58 (t, 3 1 J( H, 1H) ¼ 8.0 Hz, 1H, bzoxpy, H4), 7.85 (d, 3J(1H, 1H) ¼ 8.2 Hz, 2H, 0 0 H4 ,7 ), 7.25e7.15 (m, 6H of bzimpy, 10H of Ph), 7.09 (m, 2H, Ind, H4e7), 6.55 (s, 1H, Ind, H2), 6.47 (m, 2H, Ind, H4e7). Synthesis of [(h5-Cp)Mo(CO)2(k2-bzoxpy)][BF4] (16) The reaction was carried out as described for the compound 6 but with [(h5-Cp)Mo(CO)2(NCMe)2][BF4] (1; 19.3 mg, 50 mmol) and bzoxpy (15.7 mg, 50 mmol). The crude product was washed with Et2O, recrystallized twice from CH2Cl2/Et2O and vacuum dried. Yield: 30.2 mg (49 mmol, 98%). Ruby red powder. Mp: 145e150 C (dec.). Anal. Calc. for C26H16BF4MoN3O4: C: 50.60; H: 2.61; N: 6.81. C: 50.72; H: 2.60; N: 6.74. FTIR (ATR-C, cm1): 1975 vs [na(CO)], 1894 vs [ns(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 8.82 (dd, 3J(1H, 1 H) ¼ 8.0 Hz, 4J(1H, 1H) ¼ 1.5 Hz, 1H, bzoxpy, H3), 8.43 (t, 3J(1H, 1 H) ¼ 7.9 Hz, 1H, bzoxpy, H4), 8.08 (dd, 3J(1H, 1H) ¼ 7.8 Hz, 4J(1H, 0 0 1 H) ¼ 1.5 Hz, 1H, bzoxpy, H5), 8.00 (m, 2H, bzoxpy, H4 e7 ), 7.81 (m, 40 e70 40 e70 3H, bzoxpy, H ), 7.73 (m, 1H, bzoxpy, H ), 7.61 (m, 2H, bzoxpy, 0 0 H4 e7 ), 5.85 (s, 5H, Cp). Single crystals of 16∙CH2Cl2 suitable for the X-ray analysis were prepared by careful overlayering of a CH2Cl2 solution of 16 with hexane. Synthesis of [(h5-Ind)Mo(CO)2(k2-bzoxpy)][BF4] (17) [(h5-Ind)Mo(CO)2(NCMe)2][BF4] (2; 21.8 mg, 50 mmol) was dissolved in CH2Cl2 (2 mL) and treated with bzoxpy (15.7 mg, 50 mmol). The reaction mixture was stirred at room temperature for 2 min and then treated with Et2O (15 mL). The precipitate was decanted, washed twice with Et2O, gently vacuum dried and stored at 20 C. Yield: 25.0 mg (37 mmol, 75%). Ruby red powder. Mp: 145e160 C (dec.). Anal. Calc. for C30H18BF4MoN3O4: C: 54.00; H: 2.72; N: 6.30. Found: 54.18; H: 2.65; N: 6.22. FTIR (ATR-C, cm1): 1968 vs [na(CO)], 1894 vs [ns(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 8.64 (dd, 3J(1H, 1H) ¼ 8.0 Hz, 4J(1H, 1H) ¼ 1.5 Hz, 1H, bzoxpy, H3), 8.42 (t, 3J(1H, 1H) ¼ 7.9 Hz, 1H, bzoxpy, H4), 8.21 (m, 1H, bzoxpy, 0 0 0 0 H4 e7 ), 8.14 (m, 1H, bzoxpy, H4 e7 ), 8.09 (dd, 3J(1H, 1H) ¼ 7.8 Hz, 0 0 4 1 1 5 J( H, H) ¼ 1.5 Hz, 1H, bzoxpy, H ), 7.96 (m, 1H, bzoxpy, H4 e7 ), 7.86 40 e70 (m, 2H of bzoxpy, 1H of Ind), 7.77 (m, 1H, bzoxpy, H ), 7.67 (m, 0 0 2H, bzoxpy, H4 e7 ), 6.89 (m, 2H, Ind, H4e7), 6.62 (m, 1H, Ind, H4e7), 6.46 (s-br, 1H, Ind, H1,3), 6.39 (s-br, 1H, Ind, H1,3), 5.23 (t, 3J(1H, 1 H) ¼ 2.8 Hz, 1H, Ind, H2). Synthesis of [(h5-Ind)Mo(CO)(k3-bzoxpy)][BF4] (18) The reaction was carried out as described for the compound 6 but with [(h5-Ind)Mo(CO)2(NCMe)2][BF4] (2; 21.8 mg, 50 mmol) and bzoxpy (15.7 mg, 50 mmol). The crude product was washed with Et2O, recrystallized twice from CH2Cl2/Et2O and vacuum dried. Yield: 30.1 mg (47 mmol, 94%). Indigo blue powder. Mp: 155e160 C (dec.). Anal. Calc. for C29H18BF4MoN3O3: C: 54.49; H: 2.84; N: 6.57. Found: C: 54.32; H: 2.85; N: 6.54. FTIR (ATR-C, cm1): 1874 vs [n(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 8.56 (d, 3J(1H, 1H) ¼ 7.9 Hz, 2H, 0 0 bzoxpy, H3,5), 8.07 (m, 3H, bzoxpy, H4,4 e7 ), 7.94 (m, 2H, bzoxpy, 40 e70 40 e70 H ), 7.79 (m, 4H, bzoxpy, H ), 6.66 (dd, 3J(1H, 1H) ¼ 6.5 Hz,
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J. Honzícek et al. / Journal of Organometallic Chemistry 772-773 (2014) 299e306
4 1 J( H, 1H) ¼ 3.1 Hz, 2H, Ind, H4e7), 6.64 (t, 3J(1H, 1H) ¼ 3.0 Hz, 1H, Ind, H2), 6.14 (dd, 3J(1H, 1H) ¼ 6.5 Hz, 4J(1H, 1H) ¼ 3.1 Hz, 2H, Ind, H4e7), 5.64 (d, 3J(1H, 1H) ¼ 3.0 Hz, 2H, Ind, H1,3). Single crystals of 18∙CH2Cl2 suitable for the X-ray analysis were prepared by careful overlayering of a CH2Cl2 solution of 18 with hexane.
Synthesis of [(h5-1,3-Ph2C9H5)Mo(CO)(k3-bzoxpy)][BF4] (19) The reaction was carried out as described for the compound 6 but with [(h5-1,3-Ph2C9H5)Mo(CO)2(NCMe)2][BF4] (3; 29.4 mg, 50 mmol) and bzoxpy (15.7 mg, 50 mmol). The crude product was washed with Et2O, recrystallized twice from CH2Cl2/Et2O and vacuum dried. Yield: 36.4 mg (46 mmol, 92%). Indigo blue powder. Mp: 165e170 C (dec.). Anal. Calc. for C41H26BF4MoN3O3: C: 62.22; H: 3.31; N: 5.31. Found: C: 62.46; H: 3.24; N: 5.22. FTIR (ATR-C, cm1): 1889 vs [n(CO)]. 1H NMR (CD2Cl2, 400 MHz, d ppm): 8.65 (d, 3J(1H, 1 H) ¼ 7.8 Hz, 2H, bzoxpy, H3,5), 8.26 (t, 3J(1H, 1H) ¼ 7.8 Hz, 1H, bzoxpy, H4), 7.65 (ddd, 3J(1H, 1H) ¼ 8.3 Hz, 4J(1H, 1H) ¼ 0.9 Hz, 5J(1H, 0 0 1 H) ¼ 0.6 Hz, 2H, bzoxpy, H4 ,7 ), 7.58 (ddd, 3J(1H, 1H) ¼ 8.3 Hz, 3J(1H, 0 0 1 4 1 1 H) ¼ 7.2 Hz, J( H, H) ¼ 1.4 Hz, 2H, bzoxpy, H5 ,6 ), 7.5e7.3 (m, 4H 2 of bzoxpy, 10H of Ph), 6.81 (s, 1H, Ind, H ), 6.80 (dd, 3J(1H, 1 H) ¼ 6.8 Hz, 4J(1H, 1H) ¼ 3.2 Hz, 2H, Ind, H4e7), 6.72 (dd, 3J(1H, 1 H) ¼ 6.8 Hz, 4J(1H, 1H) ¼ 3.2 Hz, 2H, Ind, H4e7). X-ray crystallography The X-ray data for the crystals of the compounds 5, 6, 7∙CH2Cl2, 10∙MeCN, 11, 16∙CH2Cl2 and 18∙CH2Cl2 were obtained at 150 K using an Oxford Cryostream low-temperature device on a Nonius KappaCCD diffractometer with Mo Ka radiation (l ¼ 0.71073 Å) and a graphite monochromator. Data reductions were performed with DENZO-SMN [28]. The absorption was corrected by integration methods [29]. Structures were solved by direct methods (Sir92) [30] and refined by full-matrix least squares based on F2 (SHELXL97) [31]. Hydrogen atoms were mostly localized on a difference Fourier map. However, to ensure uniformity of the treatment of the crystal, all hydrogen atoms were recalculated into idealized positions (riding model) and assigned temperature factors Uiso(H) ¼ 1.2[Ueq(pivot atom)] or 1.5Ueq for the methyl moiety with CeH ¼ 0.96, 0.97, and 0.93 Å for methyl, methylene, and hydrogen atoms in aromatic rings or the allyl moiety, respectively. The disordered BF 4 groups in 10∙MeCN and 18∙CH2Cl2 were treated by the standard ISOR restraint available in SHELXL97 program package [31], which caused on the one hand slightly better shape of thermal ellipsoids but on the other hand the increase of the residual electron density in 18∙CH2Cl2. In the structure of 16∙CH2Cl2, the solvent molecule (CH2Cl2) is disordered along the special position and remains untreated. Acknowledgements This work was supported by Ministry of Education of the Czech Republic (Project No. SG320001). Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jorganchem.2014.09.028. References [1] a) S. Trofimenko, Scorpionates: Polypyrazolylborate Ligands and Their Coordination Chemistry, Imperial College Press, London, 1999; b) C. Pettinari, Scorpionates II: Chelating Borate Ligands, Imperial College Press, London, 2008.
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