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Sterically demanding ferrocene-based tris(1-pyrazolyl)borate ligands
Polyhedron Vol. 17, No. 7, pp. 1149 1157, 1998
~
Pergamon
PlI: S0277-5387(97)00502-0
!) 1998 Elsevier Science Ltd All rights reserved. Printed in Great Britain 0277 5387/98 $19.00+0,00
Sterically demanding ferrocene-based tris(1-pyrazolyl)borate ligandst Eberhardt Herdtweck, Frank Peters, Wolfgang Scherer and Matthias Wagner* Anorganisch-chemisches Institut der Technischen Universit~it Miinchen, Lichtenbergstr. D-85747 Garching, Germany.
4.
(Received 6 October 1997 ; accepted 10 November 1997) Abstraet--Ferrocene-based mono- and bifunctional tris(1-pyrazolyl)borates bearing either methyl or phenyl substituents at the 3-positions of their pyrazolyl rings have been obtained from FcB(NMe2) 2 and l , l ' fc[B(NMe2)2] 2 (Fc: ferrocenyl; fc: ferrocenylene) and the corresponding pyrazole derivatives via a transamination reaction. All novel ligands have been characterized as their thallium(l) complexes, and the molecular structure of FcB(pzPh)3Tl (pz Ph : 3-phenylpyrazolyl) has been determined by X-ray crystallography. The compound features monomeric units with tridentate [FcB(pzPh)~] ligands in the crystal lattice, which is in striking contrast to the sterically less congested complex FcB(pz)3T1, that forms polymeric rods in the solid state. For the purpose of comparison, the single crystal X-ray structure of the ferrocene-free parent compound HB(pz)3TI (pz : pyrazolyl) has also been investigated, which again revealed the conventional structural motif ofmonomeric complexes. ~: 1998 Elsevier Science Ltd. All rights reserved
Keywords: ferrocene; tris(1-pyrazolyl)borates" thallium complexes.
Tris(1-pyrazolyl)borate (scorpionate) ligands [1,2] have found extensive use in numerous different areas of coordination chemistry. Although a large variety of scorpionates [R'B(pzR)3] ( R ' = H, alkyl, aryl; pz k -- pyrazolyl, substituted pyrazolyl) has been prepared until today, examples of redox-active derivatives [3] as well as of ligands bearing more than one [R'B(pz~)~] unit are still surprisingly scarce [4]. For this reason, we became interested in the design and synthesis of novel ferrocene-based mono-([1H]- ; Fig. 1) and bifunctional ([2HI 2 : Fig. 1) tris(l-pyrazolyl)borates [5,6]. The investigation of their corresponding metal complexes revealed structural motifs that are unprecedented in the coordination chemistry of this class of ligands. The molybdenum complex FcB(pz)3Mo(CO)201 ~CHzC(CH3)CH2), IH-Mo, (Fig. 2) preferentially adopts a chiral conformation with the ferrocenyl unit and the allyl substituent occupying two different segments of the scorpionate moiety, as has been shown both in the solid state (crystal structure deter-
mination) and in solution (low-temperature N M R spectroscopy) [6]. The thallium(I) derivative FcB(pz)3T1 1H-TI, (Fig. 2) provided the first example of a tris(l-pyrazolyl)borate complex featuring a polymeric structure in the crystal lattice. Each thallium atom binds to two pyrazolyl rings of one scorpionate ligand and to one pyrazolyl ring of another ligand, thereby deviating from the usually observed tridentate coordination mode [5]. These cited observations already suggest the steric demands of the ferrocenyl substituent to have an influence on the pending scorpionate fragment. It is the purpose of this paper
-
[1H]" t Dedicated to Prof. Dr. W. A. Herrmann on the occasion of his 50th birthday. * Author to whom correspondence should be addressed.
N~NN
~
2-
[2HI2-
Fig. I. Ferrocene-based mono- and bifunctional tris(I-pyrazolyl)borate ligands.
1149
1150
E. Herdtweck et al.
i
(i)
~ R
I
~"
Fe
C
--111
R: H
o
1 H-Mo
1BN
R: B(NMe2)2
R: H
1 H-TI
chiral 3 non-equivalentpz rings(a,b,b*)
Fig. 2. The chiral molybdenum complex IH-Mo and polymeric IH-TI.
to gather more definite evidence on this point. Special emphasis will be put on identifying those factors, that are responsible for the polymerisation of IH-TI. Apart from IH-Ti there are 11 structurally characterized thallium(I) scorpionate complexes currently available from the Cambridge Crystal Structure File (Release 5.10) [7]. All of them are monomeric and share two common features : (i) Sterically demanding substituents occupy the 3-positions of the pyrazolyl rings. (ii) In addition to the three pz R moieties, the boron centre bears a small hydrogen atom. In contrast, 1H-TI offers a largely unrestricted access space to the metal on one hand and possesses a bulky and pronounced non-symmetric ferrocenyl group at boron on the other. Either of these two peculiarities may lead to the unique polymeric solid state structure of 1H-TI and thus requires more detailed examination. To be able to study both effects independently, we have prepared the sterically demanding ferrocenebased scorpionate complexes 1Me-TI to 2Ph-TI (Scheme 1) and the uncongested ferrocene-free compound HB(pz)3T1, 3H-TI (Fig. 3). 1Ph-TI and 3H-TI have been investigated by X-ray crystallography. Apart from the structural problems discussed so far, sterically demanding scorpionates L are generally required to support monomeric ML(X) species of the first-row transition metals (X = e.g. alkyl, hydride, hydroxide, halide) [8,9] and to stabilize highly reactive metal complexes kinetically [2]. Henceforth, the abbreviation Fc will be used for the monosubstituted ferrocenyl unit (ChHh)Fe(ChH4), while fc stands for the 1,1'-disubstituted moiety (ChHa)Fe(ChH4). The 3-substituent at the pyrazolyl (pz) rings is denoted by a superscript; thus HPz Me is 3-methylpyrazole and Hpz ph is 3-phenylpyrazole.
' ~
'--B(pzE)3
R: H
R: B(pzE)3Li
E: Me 1Me-LI E: Ph 1Ph-Li
2BN
2Me-Li 2Ph-Li
TI
R: B(pzE)3TI
E: Me 1Me-TI
2Me-TI
E: Ph 1Ph-TI
2Ph-TI
Scheme 1. Preparation of sterically demanding ferrocenebased tris(1-pyrazolyl)borate ligands and their thallium complexes. (i) R = H: +1 LipzE, +2 HpzE, toluene/THF, 12 h reflux; R = B(NMe2)2 : +2 LipzE, +4 HpzE, toluene/THF, 12 h reflux. (ii) R = H : +1 T1NO3, THF/H20; R = B(pzE)3Li: +2 T1NO3, THF/H20.
E = Me, lPh-Li : E = Ph ; Scheme 1). Without further purification the crude products are converted to the respective TI(I) complexes 1Me-TI and 1Ph-TI by metathesis with T1NO3 in THF/H20. The same method was applied to transform the commercially available sodium salt HB(pz)~Na, 3H-Na, into 3H-TI. The bifunctional lithium scorpionates 2Me-Li and 2Ph-Li are accessible from 1,1'-fc[B(NMe2)2]2 [5,6], 2BN, 2 equiv, of Lipz z and 4 equiv, of Hpz E (2Me-Li : E = Me, 2Ph-Li: E = Ph; Scheme 1). The synthesis of 2Me-Li suffered from only moderate yield, and the compound was contaminated with small amounts of Hpz ~ even after several purification steps. However,
H--B-...,M--~, ......TI
RESULTS AND DISCUSSION
Syntheses The lithium salts 1Me-Li and IPh-Li of the monofunctional scorpionates are synthesized from FcB(NMe2)2 [5,6], 1BN, with 1 equiv, of Lipz z and 2 equiv, of Hpz z in refluxing toluene/THF (1Me-Li:
3H-TI
: R = H
3ToI-TI
° R =
p-tolyl
Fig. 3. Ferrocene-free tris(l-pyrazolyl)borato thallium(1) reference complexes.
Sterically demanding ferrocene-based tris(1-pyrazolyl)borate ligands analytically pure thallium complexes 2Me-TI and 2PhTi are readily obtained upon reaction of 2Me-Li and 2Ph-Li with T1NO3. All compounds 1Me-Li to 2Ph-TI are stable towards air and moisture even for extended periods of time.
Spectroscopic properties The HB N M R signals of 1Me-Li to 2Ph-TI appear in the range between - 1 and + 2 ppm, thereby testifying to the presence of tetracoordinated boron nuclei. The Fc substituents of lMe-Li to 1Ph-TI give rise to three resonances, while two resonances are found for the disubstituted fc backbones of 2Me-Li to 2PhTI both in the ~H- and the ~3C N M R spectra. In all cases only one set of signals is observed for the pyrazolyl units of the scorpionate ligands. On the basis of these N M R patterns it is obvious, that the methyl (phenyl) substituents of each derivative lMe-Li to 2Ph-TI are attached either only at the 3- or only at the 5-positions of the scorpionate fragments, and the formation of isomeric products can consequently be ruled out. Since bulky substituents are well-known to have a strong tendency to occupy the 3-positions of tris(l-pyrazolyl)borate ligands [2,7], it can be safely assumed, that this holds for 1Me-Li to 2Ph-TI, too. This view is also supported by the X-ray crystal structure determination of 1Ph-TI (see below). The ~H and ~3C N M R shift values of 1Me-Li to 2Ph-TI all appear in the expected regions and thus do not merit further discussion. The N M R spectra of the lithium salts are rather similar to those of the thallium complexes, with the exception of the proton resonances of the methyl substituents, which are shifted to lower field by 0.85 ppm upon going from lMe-Li to 1Me-TI.
1151
The B(pzPh)3Tl fragment deviates significantly from an ideal C3-symmetry, since its individual T1--N bond lengths differ by as much as 0.083 /~ (TI--N(2): 2.519(5)/k, T1--N(4) :2.563(5) •, T1--N(6) :2.602(5) A, ; Table 2). The mean value T1--N = 2.561 A, in ferrocenebased IPh-TI is almost identical to that found in the related ferrocene-free 3ToI-TI (Fig. 3 ; T1--N = 2.576 A) [10], but is considerably shorter than that of polymeric 1H-TI (TI--N = 2.698 /k) [5]. The difference A(TI--N) between the mean T I - - N values of IH-TI and 1Ph-TI amounts to A(T1--N) = 0.137 A. In 1PhTl, the bond angles at T1 ( N ( 2 ) - - T I - - N ( 4 ) = 74.9(2), N(2)--T1--N(6)=70.6(2)", N ( 4 ) - - T 1 - N(6) = 75.2(2) ~) fall in the usually observed range for thallium(1) scorpionate complexes [9], and surprisingly similar values are found even in the polymeric congener 1H-TI (N(2)--T1--N(4) = 70.9(2):, N ( 2 ) - - T I - - N ( 6 A ) = 83.2(1) °, N ( 4 ) - - T I - - N ( 6 A ) = 92.4(1); T1--N(6A) is the intermolecular bond). The ferrocene-free 3H-TI crystallizes with two crystallographically independent molecules (3H-Tia, 3HTIb) in the asymmetric unit (Fig. 5). While 3H-TIa possesses three T I - - N bonds of similar length (2.603(7)/k, 2.605(7)/k, 2.621(7) A), one shorter and two significantly longer T I - - N bonds are found in 3H-TIb (2.549(7) ~ , 2.667(7) A, 2.668(7) /k). The mean values T1--N in 3H-TIa (2.610 ~ ) and 3H-TIb (2.628 /k) are, however, very close, but still larger than in the sterically congested congener 3ToI-TI (TI--N = 2.576 A). Consequently, even though sterically demanding substituents at the 3-positions of the pyrazolyl rings are known to efficiently protect scorpionate complexes from intermolecular attack, there appears to be no major intramolecular repulsion between the three phenyl groups both in 3ToI-TI and in 1Ph-TI.
CONCLUSION
X-ray crystallography Orange crystals of 1Ph-Ti were obtained by layering its CH2C12 solution with benzene. The compound crystallizes together with 0.5 equiv, of benzene (triclinic ; space group PT ; Table 1). Large colourless crystals of 3H-TI (monoclinic; space group P2~; Table 1) were grown from toluene by slow evaporation of the solvent. In contrast to polymeric IH-T! [5], the more crowded derivative 1Ph-TI, as well as the ferrocene-free parent compound 3H-TI, feature the common structural motif of monomeric units in the solid state (Figs 4, 5). Thallium coordination occurs in a tridentate fashion in both molecules. Similar to 1H-Mo (Fig. 2), the ferrocenyl substituent in 1Ph-TI is located in the uncongested cleft between two pyrazolyl rings, thereby placing the third pz ph substituent (N(1) to C(3)) in a unique position almost perpendicular to the cyclopentadienyl ring.
T I - - N bonds in thallium scorpionate complexes are not very strong, and the corresponding potential energy minima appear to be rather shallow. The actual coordination geometry of the T1 centres is therefore likely to be influenced by crystal packing forces which, however, are difficult to estimate quantitatively. Nevertheless, on the basis of the structural data available, we suggest the following qualitative interpretation of factors leading to polymeric or non-polymeric thallium tris(1-pyrazolyl)borate complexes in the solid state. From the molecular structure of 3H-TI it is evident, that the absence of bulky substituents at the 3-positions of the pyrazolyl rings does not by itself lead to the generation of a polymeric thallium(I) scorpionate. A comparison of 3H-TI with IH-TI indicates the Fc group to be required to induce polymerization, and the critical factor appears to be the degree of steric crowding at boron. In the hypothetical tridentate
1152
E. H e r d t w e c k et al. Table I. Summary of crystallographic data of complexes IPh-TI and 3H-TI
Compound Formula
1 Ph-TI C37H3oBFeN6TI • 0.5 C6H6 868.76 0.41 × 0.28 x 0.13 Triclinic PT (No. 2) 163 (2) 10.5622(6) 13.3208(9) 14.0361(9) 62.057(6) 80.559(6) 72.687(6) 1664.8(2) 1.733 2 Mo K~, 0.71073 A 10,403 5835 5197 421 53.1 0.0490 [all data] 0.1155 [all data] 1.027 Jail data]
.lit Crystal dimension (mm) Crystal system Space group Temperature (K) a (/~) h (A) c (A) c~ ( ) /$ ( ) ~, ( ) V (A') p~,~c (g cm ~) z Radiation No. of total reflections No. of unique reflections No. of observed reflections ( > 2a) No. of parameters #(cm ~) Final R~" Final wR2h GOOF'
3H-TI CgH,,BN~T1 417.41 0.20 x 0.20 x 0.10 Monoclinic P2~ (No. 4) 173(2) 7.7812(3) 9.3364(4) 16.9680(6) 90 91.761 (4) 90 1232.1(1) 2.250 4 Mo-K~, 0.71073 A 15,671 5762 5556 306 130.9 0.0353 [all data] 0.0870 [all data] 1.043 [all data]
" R, = ~ ( I I & I - I F c l I ) ! ~ I F . I .
~,,,&~- p:w(r?,--F~)21Zw(F~)2] '2. 'GOOF = [Ew(F~-F~)2/(NONV)]L-~.
C22 C 2 1 ~ _ ~ _ C23 C2E
C2~-~
~
],C24
C3 N2
c12
NIT
C13 ~
C25
C31 ..r--,C30
Tt
I
N4~---~4g:~
F
C26 /
I~
N3
Cl"~i CIO (~Fe
L
I ~ J kk'~' ~ C 4
C9 ~
~N8 I
-C5 g32
C19
C15
~'I"~C28 C27 C37 C36
C8 C33
C34
C3S
Fig, 4. PLATON-plot of 1Ph-TI : thermal ellipsoids are drawn at the 50% probability level.
Sterically demanding ferrocene-based
tris(1-pyrazolyl)borate
1153
ligands
Table 2. Selected bond distances (A) and angles ( ) of compounds 1Ph-TI and 3H-TI
1Ph-TI
N]
B(I)--C(10)
1.601(9)
B(1)--N(1)
1.563(8)
B(1)--N(3)
1.556(9)
B(1)--N(5)
1.569(9)
N(I)--N(2)
1.360(7)
ILl
Fig. 5. PLATON-plot of 3H-Tla; thermal ellipsoids are drawn at the 50% probability level.
coordination mode, both the C(6)--H(6) and the C(9)--H(9) vector would point towards the Fc backbone (cf. 1Ph-TI). This sterically congested arrangement can be improved by rotating one of the two pyrazolyl rings by ca 9 0 ~ about the B - - N axis. The scorpionate fragment now still acts as a chelating ligand, and on the other hand establishes only one unfavourable short distance to the ferrocene backbone (Fig. 6 ; marked with an asterisk). The dangling pyrazolyl donor, which can only act as a bridging ligand, consequently induces the formation of polymeric rods. In 1H-TI, short intermolecular distances of about 4 A are found between adjacent ligands (Fig. 6 ; short distances are marked with a "#"). It is obvious that, for example, a phenyl ring occupying the 3-positions of the scorpionate ligands will not fit into this limited space, and consequently 1Ph-TI is forced to adopt a different (monomeric) solid state structure. The conclusion which asserts itself in view of the facts just summarized is that steric congestion due to an Fc substituent at boron, facilitates the formation of thallium(l) tris(1-pyrazolyl)borate coordination polymers (IH-TI). However, this effect may be outweighed by (i) the steric demands of bulky substituents in the 3-positions of the pyrazolyl rings (1PhTI) and (ii) the use of metal complex fragments with a high affinity to strongly coordinating chelate ligands (IH-Mo). In both cases, a tridentate coordination mode leading to monomeric units is strongly favoured. EXPERIMENTAL
All reactions and manipulations of air-sensitive compounds were carried r u t in dry, oxygen-free argon using standard Schlenk ware or in an argon-filled
N(1)--B(I)--N(3)
109.7(5)
N(I)--B(I)--N(5)
108.2(5)
N(3)--B(1)--N(5)
106.5(4)
N(3)---N(4)
1.366(7)
N(5)--N(6)
1.370(7)
TI--N (2)
2.519(5)
T1--N (4)
2.563(5)
T1--N(6)
2.602(5)
N(2)--TI--N(4)
74.9(2)
N(2)--TI--N(6)
70.6(2)
N(4)--T1--N(6)
75.2(2)
3H-Tla 3H-TIb
1.533(10) 1.544(10) 1.538(10) 1.547(10) 1.550(11) 1.544(10) 1.377(9) 1.361(10) 110.1(6) 111.0(6) 111.1(6) 108.6(6) 110.6(6) 111.1(5) 1.364(9) 1,358(9) 1.360(9) 1.359(9) 2.6(13(7) 2,667(7) 2.621 (7) 2.549(7) 2.605(7) 2,668(7) 72.712) 72.512) 73,8(2) 72.8(2) 72.4(2) 74,0(2)
drybox. Solvents were freshly distilled under N 2 from N a / K alloy-benzophenone (toluene, hexane, T H F ) or from Call2 (CH2C12) prior to use. N M R : Jeol J M N - G X 400 and Bruker DPX 400 (abbreviations: s = singlet, d = doublet, tr = triplet, vtr = virtual triplet, q = quartet, n.r. = multiplet expected but not resolved, br = broad, n.o. = not observed, Fc = (CsH~)Fe(CsH4), fc = 1,1'-(CsH4)Fe(CsH4), Ph = C6H5, i = i p s o , o = o r t h o , m = m e t a , p = p a r a , pz = pyrazolyl fragment in pz Me and in pzPh). N M R spectra were recorded at ambient temperature. ~hB N M R shifts are given relative to external BF3" Et20. MS (CI, FAB mode) : Finnigan M A T 90. Elemental analyses: Microanalytical laboratory of the Technische Universit~,t Manchen. The compounds FcB(NMe2)2 (1BN) [5,6], l , l ' fc[B(NMe:)2]2 (2BN) [5,6], and Hpz Ph [8] were synthesized according to literature procedures. The lith-
1154
E. Herdtweck et al. with a solution of TINO3 (0.45 g, 1.69 mmol) in deionized and degassed water (10 ml), whereupon a yellow precipitate formed. The slurry was stirred for 1 h, and filtered through a frit (G3). The insoluble material was triturated with water (10 ml) and hexane (20 ml) and dried in vacuo. Yield : 0.93 g (94%). lib N M R (128.3 MHz, CDC13) : 6 0.4 (hl/z = 120 Hz). IH N M R (400 MHz, CDCI3): 6 2.35 (s, 9H, CH3), 4.21 (s, 5H, C5H5), 4.26, 4.46 (2 × vtr, 2 × 2H, J(HH) = 1.8 Hz, C5H4), 5.92 (d, 3H, J(HH) = 2.0 Hz, pz-H4), 7.97 (n.r., 3H, pz-H5). ~3C N M R (100.5 MHz, CDCI3) : 6 13.4 (br, CH3), 69.0 (C5H5), 69.9, 75.4 (C5H4), n.o. (C5H4-0, 104.0 (pz-C4), 136.1 (pzC5), 148.4 (pz-C3). CI-MS: m/z 644 [M+; 100%]; 358 [M + --TlpzMe; 60%]. Found: C, 41.63; H, 3.85; N, 13.16. Calc. for C22Hz4BFeN6T1 [643.51] :C, 41.06; H, 3.76; N, 13.06%.
Synthesis ofFcB(pzPh)3Li (1Ph-Li) Fig. 6. Section of a polymeric rod of 1H-TI ; short inter- (#) and intramolecular (*) contacts are marked.
ium pyrazolides Lipz Meand Lipz Phwere obtained from the respective pyrazoles (Hpz Me, Hpz Ph) and n-butyl lithium in toluene.
Synthesis of FcB(pzMe)3Li (1Me-Li) 1BN (2.91 g, 10.25 mmol) in toluene (100 ml) was treated dropwise with stirring at ambient temperature with a solution of Lipz Me(0.99 g, 11.25 mmol) in T H F (30 ml). Hpz Me (1.85 g, 22.53 mmol) in toluene (20 ml) was added and the red-orange solution refluxed for 12 h. The clear solution was allowed to cool to ambient temperature and concentrated in vacuo to a volume of 50 ml, whereupon an orange precipitate formed, which was collected on a frit (G3), triturated with toluene (10 ml) and hexane (30 ml) and dried in vacuo. Yield: 3.88 g (85%). liB N M R (128.3 MHz, CDC13) : 6 0.2 (hi/2 = 320 Hz). ~H N M R (400 MHz, CDC13) : 6 1.50 (very br, 9H, CH3), 4.05 (br, 2H, C5H4), 4.35 (s, 5H, C5H5), 4.44 (br, 2H, C5H4), 5.85 (br, 3H, pz-H4), 8.3 (very br, 3H, pz-H5). ~3C N M R (100.5 MHz, CDCI3): 6 12.2 (br, CH3), 69.2 (CsH~), 69.7, 75.3 (C5H4), n.o. (C5H4-i), 103.8 (pz-C4), 137.4 (pz-C5), 150.0 (br, pzC3). Found: C, 59.63; H, 5.75; N, 18.73. Calc. for C22H24BFeLiN6 [446.07]: C, 59.24; H, 5.42; N, 18.84%.
Synthesis ofFcB(pzM°)3Tl (IMe-TI) 1Me-Li (0.69 g, 1.55 mmol) in T H F (20 ml) was treated dropwise with stirring at ambient temperature
IPh-Li was synthesized similar to 1Me-Li from 1BN (1.46 g, 5.14 mmol), Lipz Ph (0.85 g, 5.66 mmol) and Hpz Ph (1.63 g, 11.31 mmol). Yield: 2.93 g (81%). liB N M R (128.3 MHz, CDCI3) : 6 0.3 (hi/2 = 260 Hz). tH N M R (400 MHz, CDC13): 6 4.34 (s, 5H, CsH~), 4.45, 4.56 (2 × vtr, 2 × 2H, J(HH) = 1.5 Hz, C5H4), 6.32 (d, 3H, J(HH) = 2.0 Hz, pz-H4), 7.21 (tr, 3H, J(HH) = 7.5 Hz, Ph-p), 7.29 (vtr, 6H, J(HH) = 7.5 Hz, Ph-m), 7.61 (d, 6H, J ( H H ) = 7.5 Hz, Ph-o), 8.18 (br, 3H, pz-H5), t3C N M R (100.5 MHz, CDCI3) : ~ 69.1 (C5H5), 70.1, 75.6 (C5H4), n.o. (CsH4-i), 101.9 (pz-C4), 126.9 (Ph-o), 127.1 (Ph-p), 128.2 (Ph-m), 135.0 (Ph-i), 136.1 (pz-C5), 152.6 (br, pz-C3). Found: C, 69.64; H, 5.21 ; N, 12.33. Calc. for C37H30BFeLiN6 [632.29] × 1.0 T H F [72.11]:C, 69.91 ; H, 5.44 ; N, 11.93%.
Synthesis of FcB(pzPh)3T1 (1Ph-Tl) IPh-TI was synthesized similar to IMe-TI from 1Ph-Li × 1 T H F (0.59 g, 0.84 mmol) and T1NO3 (0.25 g, 0.94 mmol). X-ray quality crystals were obtained from benzene/CH2C12. Yield : 0.64 g (88%). ItB N M R (128.3 MHz, CDCI3) : 6 1.2 (hi~2 = 250 Hz). IH N M R (400 MHz, CDCI3): 6 4.21 (s, 5H, C5H5), 4.31, 4.48 (2×vtr, 2 × 2 H , J(HH) = 1.8 Hz, C~Ha), 6.54 (d, 3H, J(HH) = 2.5 Hz, pz-H4), 7.29 (tr, 3H, J(HH) = 7.5 Hz, Ph-p), 7.36 (vtr, 6H, J(HH) = 7.5 Hz, Ph-m), 7.60 (d, 6H, J(HH) = 7.5 Hz, Ph-o), 8.11 (d, 3H, J(HH) = 2.5 Hz, pz-H5). ~3C NMR (100.5 MHz, CDC13) : ~ 68.9 (C5H5), 70.0, 74.9 (C5H4), n.o. (CsH4-i), 103.2 (pz-C4), 126.6 (Ph-o), 127.6 (Ph-p), 128.8 (Ph-m), 133.7 (Ph-0, 137.1 (pzC5), 152.6 (br, pz-C3). CI-MS : m/z 830 [M + ; 100%] ; 482 [M + --Tlpzah ; 70%]. Found: C, 54.08; H, 4.07; N, 9.67. Calc. for C37H3oBFeN6TI [829.72] × 0.5 T H F [72.11] : C, 54.10; H, 3.96; N, 9.70%.
Sterically demanding ferrocene-based tris(l-pyrazolyl)borate ligands Synthesis of 1, l'-fc[B(pzr"~)3T1]2 (2Me-TI)
2BN (2.96 g, 7.73 mmol) in toluene (80 ml) was treated dropwise with stirring at ambient temperature with a solution of Lipz Me(1.36 g, 15.45 mmol) in T H F (30 ml). Hpz Me (2.55 g, 31.06 retool) in toluene (20 ml) was added and the orange solution refluxed for 12 h, whereupon an orange precipitate gradually formed. The slurry was allowed to cool to ambient temperature, all insolubles were separated by filtration and extracted with toluene (2 × 10 ml). The combined filtrates were concentrated in vacuo to a volume of 10 ml, and stored at - 3 0 ° C for 12 h. A yellow microcrystalline solid of 1,1'-fc[B(pzMe)3Li]2 was obtained, which was collected on a frit (G3), triturated with hexane (10 ml) and dried in vacuo. The crude product still contained small amounts of Hpz Me, but could be purified by conversion into the thallium(I) complex. 2Me-Li (0.65 g, 0.92 mmol) in T H F (40 ml) was treated dropwise with stirring at ambient temperature with a solution of T1NO3 (0.54 g, 2.03 mmol) in deionized and degassed water (10 ml), whereupon a yellow precipitate immediately formed. The slurry was stirred for 1 h and filtered through a frit (G3). The insoluble material was triturated with water (2 × 10 ml) and hexane (5 ml) and dried in vacuo. Yield : 0.53 g (52%). ~B N M R (128.3 MHz, CDCI3) : 6 0.4 (h,/2 = 270 Hz). 'H N M R (400 MHz, CDCI3): 6 2,~37 (s, 18H, CH3), 4.38, 4.39 (n.r., 2 x 4 H , C5H4), 5.95 (d, 6H, J(HH) = 1.8 Hz, pz-H4), 8.03 (n.r., 6H, pz-H5). ~3C N M R (100.5 MHz, CDC13) : 6 13.5 (br, C H 0, 72.0, 76.0 (C5H4) , n . o . (C5H4-/), 104.2 (pz-C4), 136.1 (pzC5), 148.5 (pz-C3). FAB-MS: m/z 1102 [M+; 5%], 530 [M + - 2 TlpzM~; 85%], 449 [M+-2 TlpzMe--pzM~; 100%]. Found: C, 37.09; H, 3.59; N 151.13. Calc. for C34H38B2FeNI2TI2 [1100.97] :C, 37.09; H, 3.48; N, 15.27% .
Synthesis ~?["1,1 'fc[B(pzPh) 3Li]2 (2Ph-Li)
2BN (1.97 g, 5.14 mmol) in toluene (100 ml) was treated dropwise with stirring at ambient temperature with a solution of Lipz Ph (1.56 g, 10.39 mmol) in T H F (25 ml). Neat solid Hpz Ph (3.00 g, 20.81 mmol) was added through a powder funnel and the orange mixture refluxed for 12 h, whereupon a yellow precipitate gradually formed. The slurry was allowed to cool to ambient temperature. All insolubles were collected on a frit (G3), triturated with toluene (2 × 10 ml) and hexane (10 ml) and dried in vacuo. The combined filtrates were slowly concentrated in vacuo to yield a second crop of 2Ph-Li. Yield : 5.00 g (90%). ItB N M R (128.3 MHz, C D C I 3 ) : 6 --0.1 (hi/2 = 300 Hz). IH N M R (400 MHz, CDC13): ~ 4.67, 4.69 (2 × n.r., 2 x 4H, C5H4), 6.36 (d, 6H, J(HH) = 1.5 Hz, pz-H4), 7.26 (tr, 6H, J ( H H ) = 7.5 Hz, Ph-p), 7.34 (vtr, 12H, J ( H H ) = 7.5 Hz, Ph-m), 7.64 (d, 12H, J(HH) = 7.5 Hz, Ph-o), 8.3 (very br, 6H, pz-H5). J3C N M R (100.5 MHz, CDC13) : 6 72.2, 76.3 (C5H4), n.o.
1155
(C5H4-i), 102.1 (pz-C4), 126.9 (Ph-o), 127.1 (Ph-p), 128.2 (Ph-m), 134.9 (Ph-i), 136.3 (pz-C5), 152.8 (br, pz-C3). Found: C, 70.70 ; H, 4.29 ; N, 15.91. Calc. for C64HsoB2FeLi2NI2 [1078.54]: C, 71.27; H, 4.64; N, 15.58%. Synthesis of 1,1'-fc[B(pzPh)3T1]2 (2Ph-TI)
2Ph-Li (1.06 g, 0.98 mmol) in T H F (60 ml) was treated dropwise with stirring at ambient temperature with a solution of T1NO3 (0.58 g, 2.18 mmol) in deionized and degassed water (15 ml), whereupon a yellow precipitate formed. The slurry was stirred for 1 h, and filtered through a frit (G3). The insoluble material was triturated with water (5 ml) and hexane (10 ml) and dried in vacuo. Yield : 1.24 g (82%). liB N M R (128.3 MHz, CDCI3) : 6 0.7 (hi,,,. = 300 Hz). ~H N M R (400 MHz, CDC13): 6 4.40, 4.43 (2 x n.r., 2 x 4H, C5H4), 6.56 (d, 6H, J(HH) = 2.0 Hz, pz-H4), 7.29 (tr, 6H, J ( H H ) = 7.5 Hz, Ph-p), 7.36 (vtr, 12H, J ( H H ) = 7.5 Hz, Ph-m), 7.60 (d, 12H. J(HH) = 7.5 Hz, Ph-o), 8.16 (n.r., 6H, pz-H5). ~3C N M R (100.5 MHz, CDC13) : 6 72.0, 75.3 (C5H4), n.o. (C5H4-i), 103.3 (pz-C4), 126.6 (br, Ph-o), 127.7 (Php), 128.9 (Ph-m), 133.7 (Ph-i), 137.2 (pz-C5), 152.7 (br, pz-C3). FAB-MS: m/z 1474 [M+; 5%], 778 [ M + - 2 Tlpzph; 100%], 635 [M+--2 TlpzPh--pzPh; 90%]. Found: C, 52.99; H, 4.10; N 10.91. Calc. for C64HsoB2FeN~2TI2 [1473.40] x 1.0 T H F [72.11]: C, 52.85 ; H, 3.78 ; N, 10.88%. Synthesis ofHB(pz)3T1 (3H-TI)
3H-Na (0.53 g, 2.25 mmol) in T H F (30 ml) was treated dropwise with stirring at ambient temperature with a solution of T1NO3 (0.66 g, 2.48 mmol) in deionized and degassed water (15 ml) and stirred for 2 h. The clear colourless solution was slowly concentrated under reduced pressure, whereupon a colourless precipitate formed, which was collected on a frit (G3), triturated with H20 (2 x 10 ml) and dried in vacuo. Yield : 0.86 g (92%). X-ray quality crystals of 3H-Ti were grown by slow evaporation of its toluene solution at ambient temperature. ItB N M R (128.3 MHz, CDC13) : 6 - 2 . 1 (h~/2 = 220 Hz). ~H N M R (400 MHz, CDC13) : 6 4.65 (q, 1H, J(HH) = 105 Hz, BH), 6.19 (vtr, 3H, J(HH) = 1.6 Hz, pz-H4), 7.53, 7.72 (2 x d, 2 x 3H, J(HH) = 1.6 Hz, pz-H3,5). 13C N M R (100.5 MHz, CDC13) : 6 104.1 (pz-C4), 135.6, 139.2 (pz-C3,5). Found: C, 25.90; H, 2.59; N, 20.20. Calc. for C9HIoBN6TI [417.40]: C, 25.90; H, 2.41 ; N, 20.13%. Crystal structure determination of 1Ph-TI
Suitable crystals were grown by layering a CH2C12 solution of 1Ph-TI with benzene at ambient temperature. The compound crystallizes together with 0.5
1156
E. Herdtweck eta/.
equiv, of benzene, C37H30BFeN6Tl'0.5 C6H6, fw = 868.76 ; crystal size 0.41 × 0.28 × 0.13 mm, triclinic space group PT (I.T. No. 2), a = 10.5622(6) A, b = 13.3208(9) A,, e = 14.0361(9) A, ~ = 62.057(6), f l = 8 0 . 5 5 9 ( 6 ) , , , = 7 2 . 6 8 7 ( 6 ) , V = 1664,8(2) /~3, Z = 2 ; p~,,~= 1.733 g cm 3; F 0 0 0 = 8 5 4 ; tz=53-1 cm ~. Crystal data, together with details of the data collection and structure refinement, are listed in Table 1. Preliminary examination and data collection were carried out on an imaging plate diffraction system (IPDS; STOE&CIE)equipped with a rotating anode ( E N R A F N O N I U S FR591 ; 50 kV; 80 m A ; 4.0 kW) and graphite monochromated Mc~K~ radiation (2 = 0,71073). The data collection was performed at 163(2) K within the ()-range of 2.0 < 0 < 25.6' with an exposure time of 2.5 rain per image (rotating scan modus from ~ 0 = 0 ' to 164 with Aq?= 1 ). A total number of 10,403 reflections were collected, from which a sum of 5835 independent reflections remained and were used for all calculations. Data were corrected for Lorentz and polarization effects [11]. Corrections for intensity decay and absorption effects are based on the program D E C A Y (SF = 4) [11]. The unit cell parameters were obtained by least squares refinements of 4557 reflections with the program CELL [I 1,12]. The structure was solved by direct methods and refined by full-matrix least squares calculations with anisotropic thermal parameters for all non-hydrogen atoms of 3Ph-TI and isotropic thermal parameters for benzene. All hydrogen atoms were calculated in ideal positions. Full matrix least squares refinements were carried out by minimizing E w ( F o - F ~ ) -~ with SHELXL weighting scheme (w = l/[a2(Fo)+ (O.090. P) ~-+O.OOOO. P] where P = (F~ + 2" F~)/3) and stopped at shift/err < 0.001, wR2 = 0.1155, and Rt = 0.0490 for all data; G O O F = 1.027, 421 parameters, residual electron density + 3.20 e A ~, - 3.64 e A 3 (T1 residual). Neutral atom scattering factors for all atoms and anomalous dispersion corrections for the non-hydrogen atoms were taken from the International Tables.lbr X-Ray Co,stallography [13]. All calculations were performed on a DEC 3000 AXP workstation with the STRUX-V system [14], including the programs PLATON-92 [15], PLUTON-92 [15], SIR-92 [16], and SHELXL-93 [17]. Atomic coordinates have been deposited with the Cambridge Crystallographic Data Centre.
cm '. Crystal data together with details of the data collection and structure refinement are listed in Table I. Preliminary examination and data collection were carried out on an imaging plate diffraction system (IPDS; STOE&Cm) equipped with a rotating anode ( E N R A F N O N I U S FR591 ; 50 kV: 80 m A ; 4.0 kW) and graphite monochromated Mo-K~ radiation (2 = 0.71073). The data collection was performed at 173(2) K within the 0-range of 2.5' < 0 < 27.8' with an exposure time of 3 min per image (rotating scan modus from ~p = 0 . 0 to 270.0: with A(p = 1'). A total number of 15,671 reflections were collected, from which a sum of 5762 independent reflections remained and were used for all calculations (12 systematically absent reflections rejected). Data were corrected for Lorentz and polarization effects [11]. Corrections for intensity decay and absorption effects are based on the program D E C A Y (SF = 3) [11]. The unit cell parameters were obtained by least squares refinements of 5000 reflections with the program CELL [11,12]. The structure was solved by the Patterson method and refined by full-matrix least squares calculations with anisotropic thermal parameters for all non-hydrogen atoms. All hydrogen atoms were calculated in ideal positions. Full matrix least squares refnements were carried out by minimizing Ew(F,]-F~,-')~" with SHELXL weighting scheme ( w = I/[a2(F~)+ (0.0510" P)2+0.0000. P] where P = (F~, + 2 " F~)/3) and stopped at shift/err < 0.001, wR2 = 0.0870, and R, = 0.0353 for all data; G O O F = 1.043, 306 parameters, residual electron density + 4.35 e A - ) , - 1.64 e A ~ (TI residual), Flack parameter = - 0 . 0 0 3 2 (0.0108). (Structure refinement of the enantiomorphic model gave values wR2 = 0.134, and R~ = 0.0498 for all d a t a G O O F = 1.052, Flack parameter = 1.0529 (0.0196).) Neutral atom scattering factors for all atoms and anomalous dispersion corrections for the non-hydrogen atoms were taken from the International Tables Jbr X-Ray Crvstalloaraphy [13]. All calculations were performed on a DEC 3000 AXP workstation with the STRUX-V system [14], including the programs PLATON-92 [15], PLUTON-92 [15], SIR-92 [16] and SHELXL-93 [17]. Atomic coordinates have been deposited with the Cambridge Crystallographic Data Centre.
Acknowledgement--Financial funding by the "Deutsche Forschungsgemeinschaft" and the "Fonds der Chemischen lndustrie" is gratefully acknowledged.
Crystal structure determination of 3H-TI Suitable crystals of 3H-TI were grown by slow evaporation of its toluene solution at ambient temperature. There are two crystallographically independent molecules in the asymmetric unit (3H-Tia, 3H-TIb), CgHmBN6TI, . t h ' = 4 1 7 . 4 1 ; crystal size 0.20 × 0.20 × 0.10 mm, monoclinic space group P21 (I.T. No. 4); a = 7.7812(3) ,~, b = 9.3364(4) A, c = 16.9680(6) A, fl = 91.761(4) °, V = 1232.1(1) fit3, Z = 4; Pc~c = 2.250 g cm-3; F000 = 768; /x = 130.9
REFERENCES 1. Trofimenko, S., J. Am. Chem. Soe., 1967, 89, 3170. 2. Trofimenko, S., Chem. Ret,., 1993, 93, 943. 3. Niedenzu, K., Serwatowski, J. and Trofimenko, S., lnorg. Chem., 1991, 30, 524. 4. Brock, C. P., Das, M. K., Minton, R. P. and Niedenzu, K., J. Am. Chem. Soc., 1988, 110, 817.
Sterically demanding ferrocene-based tris(1-pyrazolyl)borate ligands 5. J~ikle, F., Polborn, K. and Wagner, M., Chem. Ber., 1996, 129, 603. 6. de Biani, F. F., J~ikle, F., Spiegler, M., Wagner, M. and Zanello, P., Inor9. Chem., 1997, 36, 2103. Note : Figure 1 of this paper contains a structural formula with wrong connectivity (compound B). For the right connectivity see Ref. [3]. 7. Allen, F. H., Kennard, O. and Taylor, R., Ace. Chem. Res., 1983, 16, 146. 8. Trofimenko, S., Calabrese, J. C. and Thompson, J. S., Inory. Chem., 1987, 26, 1507. 9. Parkin, G., Ado. Inor9. Chem., 1995, 42, 291. 10. Ferguson, G., Jennings, M. C., Lalor, F. J. and Shanahan, C., Acta Co,stallogr., 1991, C47, 2079. 11. IPDS Operatin9 System, Version 2.6. STOE &CtE. GmbH: Darmstadt, Germany, 1995.
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12. Scht~tt, W., Herdtweck, E., Hahn, F. and KreiBk F. R., J. Organomet. Chem., 1993, 443, C33, and references cited therein. 13. International Tables for X-ray Crystalloyraphy, ed. A. J. C. Wilson. Kluwer Academic Publishers : Dordrecht, 1992, Vol. C, Tables 4.2.4.2 (pp. 193-199), 4.2.6.8 (pp. 219 222) and 6.1.1.4 (pp. 500502). 14. Artus, G., Scherer, W., Priermeier, T. and Herdtweck, E., "'STRUX-V", A Proyram System to Handle X-ray Data. TU Mtinchen: Germany, 1994. 15. Spek, A. k., Acta Co,stallogr., 1990, A46, C34. 16. Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. and Camalli, M., S1R-92 ; University of Bari, Italy. 17. Sheldrick, G. M., J. Appl. Co,st., 1993, in press.
~
Pergamon
PlI: S0277-5387(97)00502-0
!) 1998 Elsevier Science Ltd All rights reserved. Printed in Great Britain 0277 5387/98 $19.00+0,00
Sterically demanding ferrocene-based tris(1-pyrazolyl)borate ligandst Eberhardt Herdtweck, Frank Peters, Wolfgang Scherer and Matthias Wagner* Anorganisch-chemisches Institut der Technischen Universit~it Miinchen, Lichtenbergstr. D-85747 Garching, Germany.
4.
(Received 6 October 1997 ; accepted 10 November 1997) Abstraet--Ferrocene-based mono- and bifunctional tris(1-pyrazolyl)borates bearing either methyl or phenyl substituents at the 3-positions of their pyrazolyl rings have been obtained from FcB(NMe2) 2 and l , l ' fc[B(NMe2)2] 2 (Fc: ferrocenyl; fc: ferrocenylene) and the corresponding pyrazole derivatives via a transamination reaction. All novel ligands have been characterized as their thallium(l) complexes, and the molecular structure of FcB(pzPh)3Tl (pz Ph : 3-phenylpyrazolyl) has been determined by X-ray crystallography. The compound features monomeric units with tridentate [FcB(pzPh)~] ligands in the crystal lattice, which is in striking contrast to the sterically less congested complex FcB(pz)3T1, that forms polymeric rods in the solid state. For the purpose of comparison, the single crystal X-ray structure of the ferrocene-free parent compound HB(pz)3TI (pz : pyrazolyl) has also been investigated, which again revealed the conventional structural motif ofmonomeric complexes. ~: 1998 Elsevier Science Ltd. All rights reserved
Keywords: ferrocene; tris(1-pyrazolyl)borates" thallium complexes.
Tris(1-pyrazolyl)borate (scorpionate) ligands [1,2] have found extensive use in numerous different areas of coordination chemistry. Although a large variety of scorpionates [R'B(pzR)3] ( R ' = H, alkyl, aryl; pz k -- pyrazolyl, substituted pyrazolyl) has been prepared until today, examples of redox-active derivatives [3] as well as of ligands bearing more than one [R'B(pz~)~] unit are still surprisingly scarce [4]. For this reason, we became interested in the design and synthesis of novel ferrocene-based mono-([1H]- ; Fig. 1) and bifunctional ([2HI 2 : Fig. 1) tris(l-pyrazolyl)borates [5,6]. The investigation of their corresponding metal complexes revealed structural motifs that are unprecedented in the coordination chemistry of this class of ligands. The molybdenum complex FcB(pz)3Mo(CO)201 ~CHzC(CH3)CH2), IH-Mo, (Fig. 2) preferentially adopts a chiral conformation with the ferrocenyl unit and the allyl substituent occupying two different segments of the scorpionate moiety, as has been shown both in the solid state (crystal structure deter-
mination) and in solution (low-temperature N M R spectroscopy) [6]. The thallium(I) derivative FcB(pz)3T1 1H-TI, (Fig. 2) provided the first example of a tris(l-pyrazolyl)borate complex featuring a polymeric structure in the crystal lattice. Each thallium atom binds to two pyrazolyl rings of one scorpionate ligand and to one pyrazolyl ring of another ligand, thereby deviating from the usually observed tridentate coordination mode [5]. These cited observations already suggest the steric demands of the ferrocenyl substituent to have an influence on the pending scorpionate fragment. It is the purpose of this paper
-
[1H]" t Dedicated to Prof. Dr. W. A. Herrmann on the occasion of his 50th birthday. * Author to whom correspondence should be addressed.
N~NN
~
2-
[2HI2-
Fig. I. Ferrocene-based mono- and bifunctional tris(I-pyrazolyl)borate ligands.
1149
1150
E. Herdtweck et al.
i
(i)
~ R
I
~"
Fe
C
--111
R: H
o
1 H-Mo
1BN
R: B(NMe2)2
R: H
1 H-TI
chiral 3 non-equivalentpz rings(a,b,b*)
Fig. 2. The chiral molybdenum complex IH-Mo and polymeric IH-TI.
to gather more definite evidence on this point. Special emphasis will be put on identifying those factors, that are responsible for the polymerisation of IH-TI. Apart from IH-Ti there are 11 structurally characterized thallium(I) scorpionate complexes currently available from the Cambridge Crystal Structure File (Release 5.10) [7]. All of them are monomeric and share two common features : (i) Sterically demanding substituents occupy the 3-positions of the pyrazolyl rings. (ii) In addition to the three pz R moieties, the boron centre bears a small hydrogen atom. In contrast, 1H-TI offers a largely unrestricted access space to the metal on one hand and possesses a bulky and pronounced non-symmetric ferrocenyl group at boron on the other. Either of these two peculiarities may lead to the unique polymeric solid state structure of 1H-TI and thus requires more detailed examination. To be able to study both effects independently, we have prepared the sterically demanding ferrocenebased scorpionate complexes 1Me-TI to 2Ph-TI (Scheme 1) and the uncongested ferrocene-free compound HB(pz)3T1, 3H-TI (Fig. 3). 1Ph-TI and 3H-TI have been investigated by X-ray crystallography. Apart from the structural problems discussed so far, sterically demanding scorpionates L are generally required to support monomeric ML(X) species of the first-row transition metals (X = e.g. alkyl, hydride, hydroxide, halide) [8,9] and to stabilize highly reactive metal complexes kinetically [2]. Henceforth, the abbreviation Fc will be used for the monosubstituted ferrocenyl unit (ChHh)Fe(ChH4), while fc stands for the 1,1'-disubstituted moiety (ChHa)Fe(ChH4). The 3-substituent at the pyrazolyl (pz) rings is denoted by a superscript; thus HPz Me is 3-methylpyrazole and Hpz ph is 3-phenylpyrazole.
' ~
'--B(pzE)3
R: H
R: B(pzE)3Li
E: Me 1Me-LI E: Ph 1Ph-Li
2BN
2Me-Li 2Ph-Li
TI
R: B(pzE)3TI
E: Me 1Me-TI
2Me-TI
E: Ph 1Ph-TI
2Ph-TI
Scheme 1. Preparation of sterically demanding ferrocenebased tris(1-pyrazolyl)borate ligands and their thallium complexes. (i) R = H: +1 LipzE, +2 HpzE, toluene/THF, 12 h reflux; R = B(NMe2)2 : +2 LipzE, +4 HpzE, toluene/THF, 12 h reflux. (ii) R = H : +1 T1NO3, THF/H20; R = B(pzE)3Li: +2 T1NO3, THF/H20.
E = Me, lPh-Li : E = Ph ; Scheme 1). Without further purification the crude products are converted to the respective TI(I) complexes 1Me-TI and 1Ph-TI by metathesis with T1NO3 in THF/H20. The same method was applied to transform the commercially available sodium salt HB(pz)~Na, 3H-Na, into 3H-TI. The bifunctional lithium scorpionates 2Me-Li and 2Ph-Li are accessible from 1,1'-fc[B(NMe2)2]2 [5,6], 2BN, 2 equiv, of Lipz z and 4 equiv, of Hpz E (2Me-Li : E = Me, 2Ph-Li: E = Ph; Scheme 1). The synthesis of 2Me-Li suffered from only moderate yield, and the compound was contaminated with small amounts of Hpz ~ even after several purification steps. However,
H--B-...,M--~, ......TI
RESULTS AND DISCUSSION
Syntheses The lithium salts 1Me-Li and IPh-Li of the monofunctional scorpionates are synthesized from FcB(NMe2)2 [5,6], 1BN, with 1 equiv, of Lipz z and 2 equiv, of Hpz z in refluxing toluene/THF (1Me-Li:
3H-TI
: R = H
3ToI-TI
° R =
p-tolyl
Fig. 3. Ferrocene-free tris(l-pyrazolyl)borato thallium(1) reference complexes.
Sterically demanding ferrocene-based tris(1-pyrazolyl)borate ligands analytically pure thallium complexes 2Me-TI and 2PhTi are readily obtained upon reaction of 2Me-Li and 2Ph-Li with T1NO3. All compounds 1Me-Li to 2Ph-TI are stable towards air and moisture even for extended periods of time.
Spectroscopic properties The HB N M R signals of 1Me-Li to 2Ph-TI appear in the range between - 1 and + 2 ppm, thereby testifying to the presence of tetracoordinated boron nuclei. The Fc substituents of lMe-Li to 1Ph-TI give rise to three resonances, while two resonances are found for the disubstituted fc backbones of 2Me-Li to 2PhTI both in the ~H- and the ~3C N M R spectra. In all cases only one set of signals is observed for the pyrazolyl units of the scorpionate ligands. On the basis of these N M R patterns it is obvious, that the methyl (phenyl) substituents of each derivative lMe-Li to 2Ph-TI are attached either only at the 3- or only at the 5-positions of the scorpionate fragments, and the formation of isomeric products can consequently be ruled out. Since bulky substituents are well-known to have a strong tendency to occupy the 3-positions of tris(l-pyrazolyl)borate ligands [2,7], it can be safely assumed, that this holds for 1Me-Li to 2Ph-TI, too. This view is also supported by the X-ray crystal structure determination of 1Ph-TI (see below). The ~H and ~3C N M R shift values of 1Me-Li to 2Ph-TI all appear in the expected regions and thus do not merit further discussion. The N M R spectra of the lithium salts are rather similar to those of the thallium complexes, with the exception of the proton resonances of the methyl substituents, which are shifted to lower field by 0.85 ppm upon going from lMe-Li to 1Me-TI.
1151
The B(pzPh)3Tl fragment deviates significantly from an ideal C3-symmetry, since its individual T1--N bond lengths differ by as much as 0.083 /~ (TI--N(2): 2.519(5)/k, T1--N(4) :2.563(5) •, T1--N(6) :2.602(5) A, ; Table 2). The mean value T1--N = 2.561 A, in ferrocenebased IPh-TI is almost identical to that found in the related ferrocene-free 3ToI-TI (Fig. 3 ; T1--N = 2.576 A) [10], but is considerably shorter than that of polymeric 1H-TI (TI--N = 2.698 /k) [5]. The difference A(TI--N) between the mean T I - - N values of IH-TI and 1Ph-TI amounts to A(T1--N) = 0.137 A. In 1PhTl, the bond angles at T1 ( N ( 2 ) - - T I - - N ( 4 ) = 74.9(2), N(2)--T1--N(6)=70.6(2)", N ( 4 ) - - T 1 - N(6) = 75.2(2) ~) fall in the usually observed range for thallium(1) scorpionate complexes [9], and surprisingly similar values are found even in the polymeric congener 1H-TI (N(2)--T1--N(4) = 70.9(2):, N ( 2 ) - - T I - - N ( 6 A ) = 83.2(1) °, N ( 4 ) - - T I - - N ( 6 A ) = 92.4(1); T1--N(6A) is the intermolecular bond). The ferrocene-free 3H-TI crystallizes with two crystallographically independent molecules (3H-Tia, 3HTIb) in the asymmetric unit (Fig. 5). While 3H-TIa possesses three T I - - N bonds of similar length (2.603(7)/k, 2.605(7)/k, 2.621(7) A), one shorter and two significantly longer T I - - N bonds are found in 3H-TIb (2.549(7) ~ , 2.667(7) A, 2.668(7) /k). The mean values T1--N in 3H-TIa (2.610 ~ ) and 3H-TIb (2.628 /k) are, however, very close, but still larger than in the sterically congested congener 3ToI-TI (TI--N = 2.576 A). Consequently, even though sterically demanding substituents at the 3-positions of the pyrazolyl rings are known to efficiently protect scorpionate complexes from intermolecular attack, there appears to be no major intramolecular repulsion between the three phenyl groups both in 3ToI-TI and in 1Ph-TI.
CONCLUSION
X-ray crystallography Orange crystals of 1Ph-Ti were obtained by layering its CH2C12 solution with benzene. The compound crystallizes together with 0.5 equiv, of benzene (triclinic ; space group PT ; Table 1). Large colourless crystals of 3H-TI (monoclinic; space group P2~; Table 1) were grown from toluene by slow evaporation of the solvent. In contrast to polymeric IH-T! [5], the more crowded derivative 1Ph-TI, as well as the ferrocene-free parent compound 3H-TI, feature the common structural motif of monomeric units in the solid state (Figs 4, 5). Thallium coordination occurs in a tridentate fashion in both molecules. Similar to 1H-Mo (Fig. 2), the ferrocenyl substituent in 1Ph-TI is located in the uncongested cleft between two pyrazolyl rings, thereby placing the third pz ph substituent (N(1) to C(3)) in a unique position almost perpendicular to the cyclopentadienyl ring.
T I - - N bonds in thallium scorpionate complexes are not very strong, and the corresponding potential energy minima appear to be rather shallow. The actual coordination geometry of the T1 centres is therefore likely to be influenced by crystal packing forces which, however, are difficult to estimate quantitatively. Nevertheless, on the basis of the structural data available, we suggest the following qualitative interpretation of factors leading to polymeric or non-polymeric thallium tris(1-pyrazolyl)borate complexes in the solid state. From the molecular structure of 3H-TI it is evident, that the absence of bulky substituents at the 3-positions of the pyrazolyl rings does not by itself lead to the generation of a polymeric thallium(I) scorpionate. A comparison of 3H-TI with IH-TI indicates the Fc group to be required to induce polymerization, and the critical factor appears to be the degree of steric crowding at boron. In the hypothetical tridentate
1152
E. H e r d t w e c k et al. Table I. Summary of crystallographic data of complexes IPh-TI and 3H-TI
Compound Formula
1 Ph-TI C37H3oBFeN6TI • 0.5 C6H6 868.76 0.41 × 0.28 x 0.13 Triclinic PT (No. 2) 163 (2) 10.5622(6) 13.3208(9) 14.0361(9) 62.057(6) 80.559(6) 72.687(6) 1664.8(2) 1.733 2 Mo K~, 0.71073 A 10,403 5835 5197 421 53.1 0.0490 [all data] 0.1155 [all data] 1.027 Jail data]
.lit Crystal dimension (mm) Crystal system Space group Temperature (K) a (/~) h (A) c (A) c~ ( ) /$ ( ) ~, ( ) V (A') p~,~c (g cm ~) z Radiation No. of total reflections No. of unique reflections No. of observed reflections ( > 2a) No. of parameters #(cm ~) Final R~" Final wR2h GOOF'
3H-TI CgH,,BN~T1 417.41 0.20 x 0.20 x 0.10 Monoclinic P2~ (No. 4) 173(2) 7.7812(3) 9.3364(4) 16.9680(6) 90 91.761 (4) 90 1232.1(1) 2.250 4 Mo-K~, 0.71073 A 15,671 5762 5556 306 130.9 0.0353 [all data] 0.0870 [all data] 1.043 [all data]
" R, = ~ ( I I & I - I F c l I ) ! ~ I F . I .
~,,,&~- p:w(r?,--F~)21Zw(F~)2] '2. 'GOOF = [Ew(F~-F~)2/(NONV)]L-~.
C22 C 2 1 ~ _ ~ _ C23 C2E
C2~-~
~
],C24
C3 N2
c12
NIT
C13 ~
C25
C31 ..r--,C30
Tt
I
N4~---~4g:~
F
C26 /
I~
N3
Cl"~i CIO (~Fe
L
I ~ J kk'~' ~ C 4
C9 ~
~N8 I
-C5 g32
C19
C15
~'I"~C28 C27 C37 C36
C8 C33
C34
C3S
Fig, 4. PLATON-plot of 1Ph-TI : thermal ellipsoids are drawn at the 50% probability level.
Sterically demanding ferrocene-based
tris(1-pyrazolyl)borate
1153
ligands
Table 2. Selected bond distances (A) and angles ( ) of compounds 1Ph-TI and 3H-TI
1Ph-TI
N]
B(I)--C(10)
1.601(9)
B(1)--N(1)
1.563(8)
B(1)--N(3)
1.556(9)
B(1)--N(5)
1.569(9)
N(I)--N(2)
1.360(7)
ILl
Fig. 5. PLATON-plot of 3H-Tla; thermal ellipsoids are drawn at the 50% probability level.
coordination mode, both the C(6)--H(6) and the C(9)--H(9) vector would point towards the Fc backbone (cf. 1Ph-TI). This sterically congested arrangement can be improved by rotating one of the two pyrazolyl rings by ca 9 0 ~ about the B - - N axis. The scorpionate fragment now still acts as a chelating ligand, and on the other hand establishes only one unfavourable short distance to the ferrocene backbone (Fig. 6 ; marked with an asterisk). The dangling pyrazolyl donor, which can only act as a bridging ligand, consequently induces the formation of polymeric rods. In 1H-TI, short intermolecular distances of about 4 A are found between adjacent ligands (Fig. 6 ; short distances are marked with a "#"). It is obvious that, for example, a phenyl ring occupying the 3-positions of the scorpionate ligands will not fit into this limited space, and consequently 1Ph-TI is forced to adopt a different (monomeric) solid state structure. The conclusion which asserts itself in view of the facts just summarized is that steric congestion due to an Fc substituent at boron, facilitates the formation of thallium(l) tris(1-pyrazolyl)borate coordination polymers (IH-TI). However, this effect may be outweighed by (i) the steric demands of bulky substituents in the 3-positions of the pyrazolyl rings (1PhTI) and (ii) the use of metal complex fragments with a high affinity to strongly coordinating chelate ligands (IH-Mo). In both cases, a tridentate coordination mode leading to monomeric units is strongly favoured. EXPERIMENTAL
All reactions and manipulations of air-sensitive compounds were carried r u t in dry, oxygen-free argon using standard Schlenk ware or in an argon-filled
N(1)--B(I)--N(3)
109.7(5)
N(I)--B(I)--N(5)
108.2(5)
N(3)--B(1)--N(5)
106.5(4)
N(3)---N(4)
1.366(7)
N(5)--N(6)
1.370(7)
TI--N (2)
2.519(5)
T1--N (4)
2.563(5)
T1--N(6)
2.602(5)
N(2)--TI--N(4)
74.9(2)
N(2)--TI--N(6)
70.6(2)
N(4)--T1--N(6)
75.2(2)
3H-Tla 3H-TIb
1.533(10) 1.544(10) 1.538(10) 1.547(10) 1.550(11) 1.544(10) 1.377(9) 1.361(10) 110.1(6) 111.0(6) 111.1(6) 108.6(6) 110.6(6) 111.1(5) 1.364(9) 1,358(9) 1.360(9) 1.359(9) 2.6(13(7) 2,667(7) 2.621 (7) 2.549(7) 2.605(7) 2,668(7) 72.712) 72.512) 73,8(2) 72.8(2) 72.4(2) 74,0(2)
drybox. Solvents were freshly distilled under N 2 from N a / K alloy-benzophenone (toluene, hexane, T H F ) or from Call2 (CH2C12) prior to use. N M R : Jeol J M N - G X 400 and Bruker DPX 400 (abbreviations: s = singlet, d = doublet, tr = triplet, vtr = virtual triplet, q = quartet, n.r. = multiplet expected but not resolved, br = broad, n.o. = not observed, Fc = (CsH~)Fe(CsH4), fc = 1,1'-(CsH4)Fe(CsH4), Ph = C6H5, i = i p s o , o = o r t h o , m = m e t a , p = p a r a , pz = pyrazolyl fragment in pz Me and in pzPh). N M R spectra were recorded at ambient temperature. ~hB N M R shifts are given relative to external BF3" Et20. MS (CI, FAB mode) : Finnigan M A T 90. Elemental analyses: Microanalytical laboratory of the Technische Universit~,t Manchen. The compounds FcB(NMe2)2 (1BN) [5,6], l , l ' fc[B(NMe:)2]2 (2BN) [5,6], and Hpz Ph [8] were synthesized according to literature procedures. The lith-
1154
E. Herdtweck et al. with a solution of TINO3 (0.45 g, 1.69 mmol) in deionized and degassed water (10 ml), whereupon a yellow precipitate formed. The slurry was stirred for 1 h, and filtered through a frit (G3). The insoluble material was triturated with water (10 ml) and hexane (20 ml) and dried in vacuo. Yield : 0.93 g (94%). lib N M R (128.3 MHz, CDC13) : 6 0.4 (hl/z = 120 Hz). IH N M R (400 MHz, CDCI3): 6 2.35 (s, 9H, CH3), 4.21 (s, 5H, C5H5), 4.26, 4.46 (2 × vtr, 2 × 2H, J(HH) = 1.8 Hz, C5H4), 5.92 (d, 3H, J(HH) = 2.0 Hz, pz-H4), 7.97 (n.r., 3H, pz-H5). ~3C N M R (100.5 MHz, CDCI3) : 6 13.4 (br, CH3), 69.0 (C5H5), 69.9, 75.4 (C5H4), n.o. (C5H4-0, 104.0 (pz-C4), 136.1 (pzC5), 148.4 (pz-C3). CI-MS: m/z 644 [M+; 100%]; 358 [M + --TlpzMe; 60%]. Found: C, 41.63; H, 3.85; N, 13.16. Calc. for C22Hz4BFeN6T1 [643.51] :C, 41.06; H, 3.76; N, 13.06%.
Synthesis ofFcB(pzPh)3Li (1Ph-Li) Fig. 6. Section of a polymeric rod of 1H-TI ; short inter- (#) and intramolecular (*) contacts are marked.
ium pyrazolides Lipz Meand Lipz Phwere obtained from the respective pyrazoles (Hpz Me, Hpz Ph) and n-butyl lithium in toluene.
Synthesis of FcB(pzMe)3Li (1Me-Li) 1BN (2.91 g, 10.25 mmol) in toluene (100 ml) was treated dropwise with stirring at ambient temperature with a solution of Lipz Me(0.99 g, 11.25 mmol) in T H F (30 ml). Hpz Me (1.85 g, 22.53 mmol) in toluene (20 ml) was added and the red-orange solution refluxed for 12 h. The clear solution was allowed to cool to ambient temperature and concentrated in vacuo to a volume of 50 ml, whereupon an orange precipitate formed, which was collected on a frit (G3), triturated with toluene (10 ml) and hexane (30 ml) and dried in vacuo. Yield: 3.88 g (85%). liB N M R (128.3 MHz, CDC13) : 6 0.2 (hi/2 = 320 Hz). ~H N M R (400 MHz, CDC13) : 6 1.50 (very br, 9H, CH3), 4.05 (br, 2H, C5H4), 4.35 (s, 5H, C5H5), 4.44 (br, 2H, C5H4), 5.85 (br, 3H, pz-H4), 8.3 (very br, 3H, pz-H5). ~3C N M R (100.5 MHz, CDCI3): 6 12.2 (br, CH3), 69.2 (CsH~), 69.7, 75.3 (C5H4), n.o. (C5H4-i), 103.8 (pz-C4), 137.4 (pz-C5), 150.0 (br, pzC3). Found: C, 59.63; H, 5.75; N, 18.73. Calc. for C22H24BFeLiN6 [446.07]: C, 59.24; H, 5.42; N, 18.84%.
Synthesis ofFcB(pzM°)3Tl (IMe-TI) 1Me-Li (0.69 g, 1.55 mmol) in T H F (20 ml) was treated dropwise with stirring at ambient temperature
IPh-Li was synthesized similar to 1Me-Li from 1BN (1.46 g, 5.14 mmol), Lipz Ph (0.85 g, 5.66 mmol) and Hpz Ph (1.63 g, 11.31 mmol). Yield: 2.93 g (81%). liB N M R (128.3 MHz, CDCI3) : 6 0.3 (hi/2 = 260 Hz). tH N M R (400 MHz, CDC13): 6 4.34 (s, 5H, CsH~), 4.45, 4.56 (2 × vtr, 2 × 2H, J(HH) = 1.5 Hz, C5H4), 6.32 (d, 3H, J(HH) = 2.0 Hz, pz-H4), 7.21 (tr, 3H, J(HH) = 7.5 Hz, Ph-p), 7.29 (vtr, 6H, J(HH) = 7.5 Hz, Ph-m), 7.61 (d, 6H, J ( H H ) = 7.5 Hz, Ph-o), 8.18 (br, 3H, pz-H5), t3C N M R (100.5 MHz, CDCI3) : ~ 69.1 (C5H5), 70.1, 75.6 (C5H4), n.o. (CsH4-i), 101.9 (pz-C4), 126.9 (Ph-o), 127.1 (Ph-p), 128.2 (Ph-m), 135.0 (Ph-i), 136.1 (pz-C5), 152.6 (br, pz-C3). Found: C, 69.64; H, 5.21 ; N, 12.33. Calc. for C37H30BFeLiN6 [632.29] × 1.0 T H F [72.11]:C, 69.91 ; H, 5.44 ; N, 11.93%.
Synthesis of FcB(pzPh)3T1 (1Ph-Tl) IPh-TI was synthesized similar to IMe-TI from 1Ph-Li × 1 T H F (0.59 g, 0.84 mmol) and T1NO3 (0.25 g, 0.94 mmol). X-ray quality crystals were obtained from benzene/CH2C12. Yield : 0.64 g (88%). ItB N M R (128.3 MHz, CDCI3) : 6 1.2 (hi~2 = 250 Hz). IH N M R (400 MHz, CDCI3): 6 4.21 (s, 5H, C5H5), 4.31, 4.48 (2×vtr, 2 × 2 H , J(HH) = 1.8 Hz, C~Ha), 6.54 (d, 3H, J(HH) = 2.5 Hz, pz-H4), 7.29 (tr, 3H, J(HH) = 7.5 Hz, Ph-p), 7.36 (vtr, 6H, J(HH) = 7.5 Hz, Ph-m), 7.60 (d, 6H, J(HH) = 7.5 Hz, Ph-o), 8.11 (d, 3H, J(HH) = 2.5 Hz, pz-H5). ~3C NMR (100.5 MHz, CDC13) : ~ 68.9 (C5H5), 70.0, 74.9 (C5H4), n.o. (CsH4-i), 103.2 (pz-C4), 126.6 (Ph-o), 127.6 (Ph-p), 128.8 (Ph-m), 133.7 (Ph-0, 137.1 (pzC5), 152.6 (br, pz-C3). CI-MS : m/z 830 [M + ; 100%] ; 482 [M + --Tlpzah ; 70%]. Found: C, 54.08; H, 4.07; N, 9.67. Calc. for C37H3oBFeN6TI [829.72] × 0.5 T H F [72.11] : C, 54.10; H, 3.96; N, 9.70%.
Sterically demanding ferrocene-based tris(l-pyrazolyl)borate ligands Synthesis of 1, l'-fc[B(pzr"~)3T1]2 (2Me-TI)
2BN (2.96 g, 7.73 mmol) in toluene (80 ml) was treated dropwise with stirring at ambient temperature with a solution of Lipz Me(1.36 g, 15.45 mmol) in T H F (30 ml). Hpz Me (2.55 g, 31.06 retool) in toluene (20 ml) was added and the orange solution refluxed for 12 h, whereupon an orange precipitate gradually formed. The slurry was allowed to cool to ambient temperature, all insolubles were separated by filtration and extracted with toluene (2 × 10 ml). The combined filtrates were concentrated in vacuo to a volume of 10 ml, and stored at - 3 0 ° C for 12 h. A yellow microcrystalline solid of 1,1'-fc[B(pzMe)3Li]2 was obtained, which was collected on a frit (G3), triturated with hexane (10 ml) and dried in vacuo. The crude product still contained small amounts of Hpz Me, but could be purified by conversion into the thallium(I) complex. 2Me-Li (0.65 g, 0.92 mmol) in T H F (40 ml) was treated dropwise with stirring at ambient temperature with a solution of T1NO3 (0.54 g, 2.03 mmol) in deionized and degassed water (10 ml), whereupon a yellow precipitate immediately formed. The slurry was stirred for 1 h and filtered through a frit (G3). The insoluble material was triturated with water (2 × 10 ml) and hexane (5 ml) and dried in vacuo. Yield : 0.53 g (52%). ~B N M R (128.3 MHz, CDCI3) : 6 0.4 (h,/2 = 270 Hz). 'H N M R (400 MHz, CDCI3): 6 2,~37 (s, 18H, CH3), 4.38, 4.39 (n.r., 2 x 4 H , C5H4), 5.95 (d, 6H, J(HH) = 1.8 Hz, pz-H4), 8.03 (n.r., 6H, pz-H5). ~3C N M R (100.5 MHz, CDC13) : 6 13.5 (br, C H 0, 72.0, 76.0 (C5H4) , n . o . (C5H4-/), 104.2 (pz-C4), 136.1 (pzC5), 148.5 (pz-C3). FAB-MS: m/z 1102 [M+; 5%], 530 [M + - 2 TlpzM~; 85%], 449 [M+-2 TlpzMe--pzM~; 100%]. Found: C, 37.09; H, 3.59; N 151.13. Calc. for C34H38B2FeNI2TI2 [1100.97] :C, 37.09; H, 3.48; N, 15.27% .
Synthesis ~?["1,1 'fc[B(pzPh) 3Li]2 (2Ph-Li)
2BN (1.97 g, 5.14 mmol) in toluene (100 ml) was treated dropwise with stirring at ambient temperature with a solution of Lipz Ph (1.56 g, 10.39 mmol) in T H F (25 ml). Neat solid Hpz Ph (3.00 g, 20.81 mmol) was added through a powder funnel and the orange mixture refluxed for 12 h, whereupon a yellow precipitate gradually formed. The slurry was allowed to cool to ambient temperature. All insolubles were collected on a frit (G3), triturated with toluene (2 × 10 ml) and hexane (10 ml) and dried in vacuo. The combined filtrates were slowly concentrated in vacuo to yield a second crop of 2Ph-Li. Yield : 5.00 g (90%). ItB N M R (128.3 MHz, C D C I 3 ) : 6 --0.1 (hi/2 = 300 Hz). IH N M R (400 MHz, CDC13): ~ 4.67, 4.69 (2 × n.r., 2 x 4H, C5H4), 6.36 (d, 6H, J(HH) = 1.5 Hz, pz-H4), 7.26 (tr, 6H, J ( H H ) = 7.5 Hz, Ph-p), 7.34 (vtr, 12H, J ( H H ) = 7.5 Hz, Ph-m), 7.64 (d, 12H, J(HH) = 7.5 Hz, Ph-o), 8.3 (very br, 6H, pz-H5). J3C N M R (100.5 MHz, CDC13) : 6 72.2, 76.3 (C5H4), n.o.
1155
(C5H4-i), 102.1 (pz-C4), 126.9 (Ph-o), 127.1 (Ph-p), 128.2 (Ph-m), 134.9 (Ph-i), 136.3 (pz-C5), 152.8 (br, pz-C3). Found: C, 70.70 ; H, 4.29 ; N, 15.91. Calc. for C64HsoB2FeLi2NI2 [1078.54]: C, 71.27; H, 4.64; N, 15.58%. Synthesis of 1,1'-fc[B(pzPh)3T1]2 (2Ph-TI)
2Ph-Li (1.06 g, 0.98 mmol) in T H F (60 ml) was treated dropwise with stirring at ambient temperature with a solution of T1NO3 (0.58 g, 2.18 mmol) in deionized and degassed water (15 ml), whereupon a yellow precipitate formed. The slurry was stirred for 1 h, and filtered through a frit (G3). The insoluble material was triturated with water (5 ml) and hexane (10 ml) and dried in vacuo. Yield : 1.24 g (82%). liB N M R (128.3 MHz, CDCI3) : 6 0.7 (hi,,,. = 300 Hz). ~H N M R (400 MHz, CDC13): 6 4.40, 4.43 (2 x n.r., 2 x 4H, C5H4), 6.56 (d, 6H, J(HH) = 2.0 Hz, pz-H4), 7.29 (tr, 6H, J ( H H ) = 7.5 Hz, Ph-p), 7.36 (vtr, 12H, J ( H H ) = 7.5 Hz, Ph-m), 7.60 (d, 12H. J(HH) = 7.5 Hz, Ph-o), 8.16 (n.r., 6H, pz-H5). ~3C N M R (100.5 MHz, CDC13) : 6 72.0, 75.3 (C5H4), n.o. (C5H4-i), 103.3 (pz-C4), 126.6 (br, Ph-o), 127.7 (Php), 128.9 (Ph-m), 133.7 (Ph-i), 137.2 (pz-C5), 152.7 (br, pz-C3). FAB-MS: m/z 1474 [M+; 5%], 778 [ M + - 2 Tlpzph; 100%], 635 [M+--2 TlpzPh--pzPh; 90%]. Found: C, 52.99; H, 4.10; N 10.91. Calc. for C64HsoB2FeN~2TI2 [1473.40] x 1.0 T H F [72.11]: C, 52.85 ; H, 3.78 ; N, 10.88%. Synthesis ofHB(pz)3T1 (3H-TI)
3H-Na (0.53 g, 2.25 mmol) in T H F (30 ml) was treated dropwise with stirring at ambient temperature with a solution of T1NO3 (0.66 g, 2.48 mmol) in deionized and degassed water (15 ml) and stirred for 2 h. The clear colourless solution was slowly concentrated under reduced pressure, whereupon a colourless precipitate formed, which was collected on a frit (G3), triturated with H20 (2 x 10 ml) and dried in vacuo. Yield : 0.86 g (92%). X-ray quality crystals of 3H-Ti were grown by slow evaporation of its toluene solution at ambient temperature. ItB N M R (128.3 MHz, CDC13) : 6 - 2 . 1 (h~/2 = 220 Hz). ~H N M R (400 MHz, CDC13) : 6 4.65 (q, 1H, J(HH) = 105 Hz, BH), 6.19 (vtr, 3H, J(HH) = 1.6 Hz, pz-H4), 7.53, 7.72 (2 x d, 2 x 3H, J(HH) = 1.6 Hz, pz-H3,5). 13C N M R (100.5 MHz, CDC13) : 6 104.1 (pz-C4), 135.6, 139.2 (pz-C3,5). Found: C, 25.90; H, 2.59; N, 20.20. Calc. for C9HIoBN6TI [417.40]: C, 25.90; H, 2.41 ; N, 20.13%. Crystal structure determination of 1Ph-TI
Suitable crystals were grown by layering a CH2C12 solution of 1Ph-TI with benzene at ambient temperature. The compound crystallizes together with 0.5
1156
E. Herdtweck eta/.
equiv, of benzene, C37H30BFeN6Tl'0.5 C6H6, fw = 868.76 ; crystal size 0.41 × 0.28 × 0.13 mm, triclinic space group PT (I.T. No. 2), a = 10.5622(6) A, b = 13.3208(9) A,, e = 14.0361(9) A, ~ = 62.057(6), f l = 8 0 . 5 5 9 ( 6 ) , , , = 7 2 . 6 8 7 ( 6 ) , V = 1664,8(2) /~3, Z = 2 ; p~,,~= 1.733 g cm 3; F 0 0 0 = 8 5 4 ; tz=53-1 cm ~. Crystal data, together with details of the data collection and structure refinement, are listed in Table 1. Preliminary examination and data collection were carried out on an imaging plate diffraction system (IPDS; STOE&CIE)equipped with a rotating anode ( E N R A F N O N I U S FR591 ; 50 kV; 80 m A ; 4.0 kW) and graphite monochromated Mc~K~ radiation (2 = 0,71073). The data collection was performed at 163(2) K within the ()-range of 2.0 < 0 < 25.6' with an exposure time of 2.5 rain per image (rotating scan modus from ~ 0 = 0 ' to 164 with Aq?= 1 ). A total number of 10,403 reflections were collected, from which a sum of 5835 independent reflections remained and were used for all calculations. Data were corrected for Lorentz and polarization effects [11]. Corrections for intensity decay and absorption effects are based on the program D E C A Y (SF = 4) [11]. The unit cell parameters were obtained by least squares refinements of 4557 reflections with the program CELL [I 1,12]. The structure was solved by direct methods and refined by full-matrix least squares calculations with anisotropic thermal parameters for all non-hydrogen atoms of 3Ph-TI and isotropic thermal parameters for benzene. All hydrogen atoms were calculated in ideal positions. Full matrix least squares refinements were carried out by minimizing E w ( F o - F ~ ) -~ with SHELXL weighting scheme (w = l/[a2(Fo)+ (O.090. P) ~-+O.OOOO. P] where P = (F~ + 2" F~)/3) and stopped at shift/err < 0.001, wR2 = 0.1155, and Rt = 0.0490 for all data; G O O F = 1.027, 421 parameters, residual electron density + 3.20 e A ~, - 3.64 e A 3 (T1 residual). Neutral atom scattering factors for all atoms and anomalous dispersion corrections for the non-hydrogen atoms were taken from the International Tables.lbr X-Ray Co,stallography [13]. All calculations were performed on a DEC 3000 AXP workstation with the STRUX-V system [14], including the programs PLATON-92 [15], PLUTON-92 [15], SIR-92 [16], and SHELXL-93 [17]. Atomic coordinates have been deposited with the Cambridge Crystallographic Data Centre.
cm '. Crystal data together with details of the data collection and structure refinement are listed in Table I. Preliminary examination and data collection were carried out on an imaging plate diffraction system (IPDS; STOE&Cm) equipped with a rotating anode ( E N R A F N O N I U S FR591 ; 50 kV: 80 m A ; 4.0 kW) and graphite monochromated Mo-K~ radiation (2 = 0.71073). The data collection was performed at 173(2) K within the 0-range of 2.5' < 0 < 27.8' with an exposure time of 3 min per image (rotating scan modus from ~p = 0 . 0 to 270.0: with A(p = 1'). A total number of 15,671 reflections were collected, from which a sum of 5762 independent reflections remained and were used for all calculations (12 systematically absent reflections rejected). Data were corrected for Lorentz and polarization effects [11]. Corrections for intensity decay and absorption effects are based on the program D E C A Y (SF = 3) [11]. The unit cell parameters were obtained by least squares refinements of 5000 reflections with the program CELL [11,12]. The structure was solved by the Patterson method and refined by full-matrix least squares calculations with anisotropic thermal parameters for all non-hydrogen atoms. All hydrogen atoms were calculated in ideal positions. Full matrix least squares refnements were carried out by minimizing Ew(F,]-F~,-')~" with SHELXL weighting scheme ( w = I/[a2(F~)+ (0.0510" P)2+0.0000. P] where P = (F~, + 2 " F~)/3) and stopped at shift/err < 0.001, wR2 = 0.0870, and R, = 0.0353 for all data; G O O F = 1.043, 306 parameters, residual electron density + 4.35 e A - ) , - 1.64 e A ~ (TI residual), Flack parameter = - 0 . 0 0 3 2 (0.0108). (Structure refinement of the enantiomorphic model gave values wR2 = 0.134, and R~ = 0.0498 for all d a t a G O O F = 1.052, Flack parameter = 1.0529 (0.0196).) Neutral atom scattering factors for all atoms and anomalous dispersion corrections for the non-hydrogen atoms were taken from the International Tables Jbr X-Ray Crvstalloaraphy [13]. All calculations were performed on a DEC 3000 AXP workstation with the STRUX-V system [14], including the programs PLATON-92 [15], PLUTON-92 [15], SIR-92 [16] and SHELXL-93 [17]. Atomic coordinates have been deposited with the Cambridge Crystallographic Data Centre.
Acknowledgement--Financial funding by the "Deutsche Forschungsgemeinschaft" and the "Fonds der Chemischen lndustrie" is gratefully acknowledged.
Crystal structure determination of 3H-TI Suitable crystals of 3H-TI were grown by slow evaporation of its toluene solution at ambient temperature. There are two crystallographically independent molecules in the asymmetric unit (3H-Tia, 3H-TIb), CgHmBN6TI, . t h ' = 4 1 7 . 4 1 ; crystal size 0.20 × 0.20 × 0.10 mm, monoclinic space group P21 (I.T. No. 4); a = 7.7812(3) ,~, b = 9.3364(4) A, c = 16.9680(6) A, fl = 91.761(4) °, V = 1232.1(1) fit3, Z = 4; Pc~c = 2.250 g cm-3; F000 = 768; /x = 130.9
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Sterically demanding ferrocene-based tris(1-pyrazolyl)borate ligands 5. J~ikle, F., Polborn, K. and Wagner, M., Chem. Ber., 1996, 129, 603. 6. de Biani, F. F., J~ikle, F., Spiegler, M., Wagner, M. and Zanello, P., Inor9. Chem., 1997, 36, 2103. Note : Figure 1 of this paper contains a structural formula with wrong connectivity (compound B). For the right connectivity see Ref. [3]. 7. Allen, F. H., Kennard, O. and Taylor, R., Ace. Chem. Res., 1983, 16, 146. 8. Trofimenko, S., Calabrese, J. C. and Thompson, J. S., Inory. Chem., 1987, 26, 1507. 9. Parkin, G., Ado. Inor9. Chem., 1995, 42, 291. 10. Ferguson, G., Jennings, M. C., Lalor, F. J. and Shanahan, C., Acta Co,stallogr., 1991, C47, 2079. 11. IPDS Operatin9 System, Version 2.6. STOE &CtE. GmbH: Darmstadt, Germany, 1995.
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12. Scht~tt, W., Herdtweck, E., Hahn, F. and KreiBk F. R., J. Organomet. Chem., 1993, 443, C33, and references cited therein. 13. International Tables for X-ray Crystalloyraphy, ed. A. J. C. Wilson. Kluwer Academic Publishers : Dordrecht, 1992, Vol. C, Tables 4.2.4.2 (pp. 193-199), 4.2.6.8 (pp. 219 222) and 6.1.1.4 (pp. 500502). 14. Artus, G., Scherer, W., Priermeier, T. and Herdtweck, E., "'STRUX-V", A Proyram System to Handle X-ray Data. TU Mtinchen: Germany, 1994. 15. Spek, A. k., Acta Co,stallogr., 1990, A46, C34. 16. Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. and Camalli, M., S1R-92 ; University of Bari, Italy. 17. Sheldrick, G. M., J. Appl. Co,st., 1993, in press.