Heterodinuclear Bridging Carbido and Phosphoniocarbyne

Communication pubs.acs.org/Organometallics

Heterodinuclear Bridging Carbido and Phosphoniocarbyne Complexes† Anthony F. Hill,* Manab Sharma, and Anthony C. Willis Research School of Chemistry, Institute of Advanced Studies, The Australian National University, Canberra, Australian Capital Territory 0200, Australia S Supporting Information *

ABSTRACT: The sequential treatment of [W(CBr)(CO)2{HB(pzMe2)3}] (pz = pyrazol-1-yl) with nBuLi and [NiCl2(PEt3)2] initially affords the bridging carbido complex [WNi(μ-C)(CO)2(PEt3)2Cl{HB(pzMe2)3}], which is however unstable and isomerizes cleanly to the bridging phosphoniocarbyne complex [WNi(μ-CPEt 3 )(CO) 2 (PEt 3 )Cl{HB(pzMe2)3}].

T

Chart 2. Classification of Binuclear Carbido Ligands: (a) Cumulenic Class A; (b) Metallacarbyne Class B; (c) Polar Covalent Class C

he ample demonstration by Stone that metal−carbon multiple bonds may coordinate to one or more additional metal centers provided a paradigm shift in how bridging carbynes in polymetallic assemblies might be viewed.1 In particular, the use of carbyne complexes (Chart 1)2 for the Chart 1. Selected Nickel Carbyne Complexes Derived from Stone’s Bridge-Assisted Metal−Metal Bond Formation Strategy (R = C6H4Me-4):1,3−5 (a) [W2Ni(μ-CR)2(CO)4(ηC5H5)]; (b) [W2Re2Ni(μ-CR)2(CO)18]; (c) [WNi2(μCR)(CO)2(η-C5H5)3]; (d) [W4Ni2Pt2(μ-CR)4(CO)8(ηC5H5)4]

For metalated carbynes (class B), the localization of metal− carbon single and triple bonds generally reflects the valence electron requirements of the necessarily disparate metals.7 A third more recently encountered situation involves a polar covalent (i.e., dative) and labile interaction between a mononuclear terminal carbido complex and a second metal center,8 for which some analogy with CO and isonitrile coordination might be entertained. The distinction between classes A and B is unambiguous. The distinction between classes B and C is perhaps less clear and may be premature, since a zwitterionic canonical description for C relates it to B. As further examples of class C emerge, this distinction might not stand the test of time but, rather, be replaced by a continuum. Grubbs has drawn an analogy between these class C carbides and Lewis acid adducts of oxo and nitrido ligands,8 while class B reflects a conventional alkynyl type C−M′ bond. While it is possible to categorize the distinct bonding scenarios, comparatively little is known about the actual reactivity of μ2carbido ligands beyond the reactions of Templeton’s class B complex [MoFe(μ-C)(CO)4(η-C5H5){HB(pzMe2)3}] (pz = pyrazol-1-yl) with acids (C-protonation) and CS2 (insertion into the Fe−C bond).7b Class B carbides are, however, implicated in rhodium(I)-7f and palladium(0)-mediated9,10

strategic construction of heteropolymetallic clusters afforded a plethora of architectures that reinforced the emergence of the isolobal analogy as a conceptual tool for rationalizing cluster frameworks.3 Bimetallic complexes bridged by carbido ligands are rare; however, sufficient examples exist to allow the delineation of three distinct classes (Chart 2). Cumulenic class A carbides are typically5 but not exclusively6 homobimetallic and symmetrical in nature, the majority being analogues of Mansuy’s iron tetraphenylporphyrin (TPP) archetype [Fe2(μ-C)(TPP)2].5a © 2012 American Chemical Society

Special Issue: F. Gordon A. Stone Commemorative Issue Received: November 1, 2011 Published: January 11, 2012 2538

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and C−C and C−P bond-forming processes employing halocarbyne precursors. We have therefore begun to explore the synthesis of model compounds in which group 6 and 10 metals are spanned by a class B carbide linkage, which might provide insights into the progress of these coupling reactions. The reaction of Lalor’s molybdenum bromocarbyne complex [Mo(CBr)(CO)2{HB(pzMe2)3}] (1a)11 with nBuLi in THF results in lithium/halogen exchange to afford the synthetically versatile lithiocarbyne derivative [Mo{CLi(THF) n }(CO)2{HB(pzMe2)3}] (2a).7e,f,12 In a similar manner, the reaction of [W(CBr)(CO)2{HB(pzMe2)3}] (1b) with nBuLi affords [W{CLi(THF)n}(CO)2{HB(pzMe2)3}] (2b), which has been previously obtained by Templeton, albeit via a more circuitous route.13 Treating a THF solution of 2b, generated in situ at low temperature (dry ice/acetone) with 1 equiv of [NiCl2(PEt3)2] (3),14 results in the formation of a red solution of a new compound 4, which is stable upon warming to −10 °C and may be isolated (78% yield) at this temperature. Above this temperature, however, a second product 5 begins to form (vide infra). The 31P{1H} NMR spectrum of the initial product 4 indicates two phosphorus environments (C6D6: δP 15.74, 8.73 ppm) with the observed coupling (2JPP = 290.4 Hz) being suggestive of a trans-PA−Ni−PB arrangement. The 1H and 13 C{1H} NMR spectra are indicative of local Cs symmetry for the molecule, the most notable data from the latter being a strongly deshielded apparent triplet resonance at δC 484.0 ppm (dd, 2JPAC ≈ 2JPBC = 3.73 Hz). These data are, in addition to high-resolution mass spectrometric (positive ion ESI)15 are consistent with the formulation of 4 as the class B carbido complex [WNi(μ-C)(CO) 2 (PEt 3 ) 2 Cl{HB(pzMe2 ) 3 }] (4; Scheme 1), with the proviso that rotation about the Ni−C bond is arrested on the 31P{1H} NMR time scale.

Figure 1. Molecular structure of 4 in the crystal state (hydrogen atoms omitted). Selected bond lengths (Å) and angles (deg): W1−C1 = 1.867(4), W1−N1 = 2.224(3), W1−N3 = 2.239(3), W1−N5 = 2.318(3), Ni2−Cl1 = 2.2576(11), Ni2−P1 = 2.2134(12), Ni2−P2 = 2.2380(11), Ni2−C1 = 1.808(4); W1−C1−Ni2 = 174.8(2), N1− W1−C1 = 98.52(12), N3−W1−C1 = 99.32(13), Cl1−Ni2−P1 = 87.38(5), Cl1−Ni2−P2 = 86.26(4), P1−Ni2−P2 = 172.99(5), Cl1− Ni2−C1 = 177.46(12), P1−Ni2−C1 = 93.24(11), P2−Ni2−C1 = 93.25(11).

unremarkable and generally conform to the growing library of structural data for complexes of the form [M(CR)(CO)2L] (L = HB(pz)3, HB(pzMe2)3).2a The geometries at tungsten and nickel approximate to octahedral and square planar, respectively, such that all cis interligand angles fall within the range 77.73(10)−99.32(13)° with a marginal displacement of the phosphines on nickel toward the chloride ligand (P1−Ni2−P2 = 172.99(5)°). The geometry about the carbido ligand is essentially linear (174.8(2)°), while the W1−C1 and Ni2−C1 bond lengths (1.867(4) and 1.808(4) Å, respectively) indicate triple and single bonds, consistent with a class B description.16 The experimentally established geometry of 4 could be closely reproduced computationally at the M06/6-31g* level of theory, and the frontier orbitals of interest are depicted in Figure 2. Specifically, the HOMO-1 topology suggests a degree of electronic communication along the W−C−Ni spine (π bonding for W−C, π-antibonding for C−Ni), comprising significant contributions from both tungsten and nickel atomic orbitals. The LUMO is also associated with the W−C−Ni spine but includes substantial contributions from orbitals on the chloride and both phosphorus atoms, being σ-antibonding in character between nickel and each of its ligand donors. The HOMO corresponds primarily to the W−CO bonding interaction (see the Supporting Information). As noted above, compound 4 is thermally labile in solution and under ambient conditions isomerizes cleanly to a second compound, 5 (t0.5 = ca. 28 h at 25 °C in C6D6, spectroscopically quantitative, 72% isolated yield), with the same elemental composition (high-resolution positive ion ESI-MS). The NMR data for 5 indicate that it has no molecular element of symmetry but include two conspicuous features. First, the 31 1 P{ H} NMR spectrum comprises two resonances which are, however, not discernibly coupled to each other. The resonance at δP 35.80 is straddled by 183W satellites (JWP = 54.5 Hz); however, these are not observed for the second resonance at 19.26 ppm. Second, the 13C{1H} NMR spectrum displays two CO-associated resonances (δC 234.1, 253.7 (semibridging)) in addition to a broad unresolved multiplet resonance at 280.9

Scheme 1. Synthesis of μ-Carbido (4) and μPhosphoniocarbyne (5) Complexes (Tp* = HB(pzMe2)3)

The characterization of 4 included a crystallographic study,15 the results of which are summarized in Figure 1. Consistent with the spectroscopic data obtained from solution, in the solid state 4 has approximate but noncrystallographic Cs symmetry. The origin of chemical inequivalence of the phosphine environments evident in solution is immediately apparent, being due to the steric bulk of the HB(pzMe2)3 and phosphine ligands, which precludes rotation about the Ni−C bond with one ethyl group nestled between two pyrazolyl rings, apparently locked in place by two PC−H···π(pz) interactions. The geometric features of the “Mo(CO)2{HB(pzMe2)3}” unit are 2539

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noticeable variation involves the significantly longer (ca. 25 esd) W−C bond length observed for 5, which presumably reflects the greater steric bulk of the HB(pzMe2)3 unit. In both 5 and 6, one carbonyl ligand assumes semibridging character (Ni2−C60 = 2.305(3) Å; W1−C60−O61 = 166.4(2)°). Mononuclear phosphoniocarbyne complexes have attracted increasing attention in recent times;19 however, the only examples where these ligands bridge two metals are the complexes [Ti2{μ-CP(NMe2)3}2Cl2X2] (X = Cl,20a NMe220b) and [Zr2(μ-CPMe3)2{(CH2)2PMe2}4],20c for which direct metal−metal bonding is not invoked; i.e., these are viewed as dimetalated ylides. In the present context, the phosphoniocarbyne complexes [W(CPR3)(CO)2{HB(pzMe2)3}]+ (PR3 = PCy3, PEt3, PMe3, PMe2Ph, PPh3; Scheme 2) described by Templeton are especially relevant.19c,d Scheme 2. Templeton’s Phosphoniocarbyne Synthesis (PR3 = PCy3, PEt3, PMe3, PMe2Ph, PPh3)19c,d

Figure 2. Selected molecular orbitals for 4: (a) LUMO; (b) HOMO-1 (for full details see the Supporting Information).

There are many ways to view the bonding within the dimetallacyclopropene unit.21 The conversion of 4 to 5 might be viewed as a simple P−C bond-forming reductive elimination, depending on the extent to which the various zwitterionic canonical forms (Chart 3) contribute. Accordingly, the bonding

ppm. These data are consistent with the formulation of 5 as the bridging phosphoniocarbyne complex [WNi(μ-CPEt 3 )(CO)2(PEt3)Cl{HB(pzMe2)3}] (5) and this was crystallographically confirmed (Figure 3).17

Chart 3. Canonical Descriptions for a Bridging Phosphoniocarbyne

within 5 was interrogated computationally, with the experimentally established geometry being adequately reproduced at the M06/6-31g* level of theory (see the Supporting Information). The HOMO is one of a manifold of orbitals associated with the dimetallacyclpropene (Figure 4), and the LUMO is also found to be primarily associated with the WCNi core. The atomic charges on P (+0.76), C (−0.47), W (+0.75), and Ni (−0.71) would seem to suggest that the zwitterionic valence bond form (Ni0) does indeed have some descriptive merit. In conclusion, although little is so far known about the reactivity of μ2-carbido ligands, their implication as intermediates in the palladium-catalyzed synthesis of phosphonitocarbynes10 invokes a C−P reductive elimination step which is now substantiated for the 4 → 5 conversion. Given the increasing variety of mononuclear phosphoniocarbyne complexes now available,19 it remains to be seen if these may serve as precursors for bridge-assisted metal−metal bond formation or alternatively under what conditions these might serve as masked μ-carbido synthetic equivalents.

Figure 3. Molecular structure of 5 in the crystal state (hydrogen atoms omitted). Selected bond lengths (Å) and angles (deg): W1−Ni2 = 2.5770(4), W1−N1 = 2.247(2), W1−N3 = 2.237(2), W1−N5 = 2.268(2), W1−C1 = 1.946(2), Ni2−Cl1 = 2.2858(8), Ni2−P1 = 2.2730(9), Ni2−C1 = 1.877(3), Ni2−C60 = 2.305(3), Ni2−C70 = 2.700(3), P2−C1 = 1.747(2); P2−C1−W1 = 147.56(16), P2−C1− Ni2 = 127.68(14), W1−C1−Ni2 = 84.74(10), Ni2−W1−C1 = 46.50(8), W1−Ni2−Cl1 = 149.53(3), W1−Ni2−P1 = 123.43(3), W1−Ni2−C1 = 48.76(7), Cl1−Ni2−C1 = 101.36(8).

The molecular geometry of 5 immediately calls to mind the dimetallacyclopropenes that result from Stone’s bridge-assisted metal−metal bond-forming protocols. In the case of nickel, such a motif is proposed in the complexes [W2Ni(μCR′)2(CO)4{HB(pz)3}2] (R = Me,4f C5H4Mn(CO)318) and [W2Re2Ni(μ-CC6H4Me-4)2(CO)18]4c and was crystallographically confirmed for the complex [W 2 Ni(μ-CC 6 H 4 Me4)2(CO)4(η-C5H5)2] (6).4a The W1−Ni2, W1−C1, and Ni2−C1 bond lengths in 5 (2.5770(4), 1.946(2), and 1.877(3) Å, respectively) compare well with the average values observed for 6 (2.584(1), 1.893(9), and 1.894(8) Å). The most 2540

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Lewis, G. E.; Parrott, M. J.; Stone, F. G. A. J. Chem. Soc., Dalton Trans. 1986, 1717. (d) Elliott, G. P.; Howard, J. A. K.; Mise, T.; Moore, I.; Nunn, C. M.; Stone, F. G. A. J. Chem. Soc., Dalton Trans. 1986, 2091. (e) Delgado, E.; Hein, J.; Jeffery, J. C.; Ratermann, A. L.; Stone, F. G. A.; Farrugia, L. J. J. Chem. Soc., Dalton Trans. 1987, 1191. (f) Becke, S. H. F.; Bermudez, M. D.; Hoa, T. H. N.; Howard, J. A. K.; Johnson, O.; Stone, F. G. A. J. Chem. Soc., Dalton Trans. 1987, 1229. (g) Bermudez, M. D.; Brown, F. P. E; Stone, F. G. A. J. Chem. Soc., Dalton Trans. 1988, 1139. (h) Fernandez, J. R.; Stone, F. G. A. J. Chem. Soc., Dalton Trans. 1988, 3035. (i) Elliott, G. P.; Howard, J. A. K.; Mise, T.; Nunn, C. M.; Stone, F. G. A. Angew. Chem., Int. Ed. Engl. 1986, 25, 190. (5) (a) Mansuy, D. Pure Appl. Chem. 1980, 52, 681. (b) Mansuy, D.; Lecomte, J.-P.; Chottard, J.-C.; Bartoli, J.-F. Inorg. Chem. 1981, 20, 3119. (c) Goedkin, V. L.; Deakin, M. R.; Bottomley, L. A. J. Chem. Soc., Chem. Commun. 1982, 607. (d) Mansuy, D.; Lecomte, J.-P.; Chottard, J.-C.; Bartoli, J.-F. Inorg. Chem. 1981, 20, 3119. (e) Gardini, M.; Goedken, V. L.; Pennesi, G.; Rossi, G.; Russo, U.; Zanonato, P. Inorg. Chem. 1989, 28, 3097. (f) Bakshi, E. N.; Delfs, C. D.; Murray, K. S.; Peters, B.; Homborg, H. Inorg. Chem. 1988, 27, 4318. (g) Kienast, A.; Bruhn, C.; Homborg, H. Z. Anorg. Allg. Chem. 1997, 623, 967. (h) Kienast, A.; Homborg, H. Z. Anorg. Allg. Chem. 1998, 624, 107. (i) Galich, L.; Kienast, A.; Huckstadt, H.; Homborg, H. Z. Anorg. Allg. Chem. 1998, 624, 1235. (j) Miller, R. L.; Wolczanski, P. T.; Rheingold, A. L. J. Am. Chem. Soc. 1993, 115, 10422. (6) (a) Beck, W.; Knauer, W.; Robl, C. Angew. Chem., Int. Ed. 1990, 29, 318. (b) Solari, E.; Antonijevic, S.; Gauthier, S.; Scopelliti, R.; Severin, K. Eur. J. Inorg. Chem. 2007, 367. (7) (a) Latesky, S. L.; Selegue, J. P. J. Am. Chem. Soc. 1987, 109, 4731. (b) Etienne, M.; White, P. S.; Templeton, J. L. J. Am. Chem. Soc. 1991, 113, 2324. (c) Knauer, W.; Beck, W. Z. Anorg. Allg. Chem. 2008, 634, 2241. (d) Hong, S. H.; Day, M. W.; Grubbs, R. H. J. Am. Chem. Soc. 2004, 126, 7414. (e) Cade, I. A.; Hill, A. F.; McQueen, C. M. A. Organometallics 2009, 28, 6639. (f) Colebatch, A. L.; Cordiner, R. L.; Hill, A. F.; Nguyen, K. T. H. D.; Shang, R.; Willis, A. C. Organometallics 2009, 28, 4394. (8) Hejl, A.; Trnka, T. M.; Day, M. W.; Grubbs, R. H. Chem. Commun. 2002, 2524. (9) (a) Bruce, M. I.; Cole, M. L.; Gaudio, M.; Skelton, B. W.; White, A. H. J. Organomet. Chem. 2006, 691, 4601. (b) Armitt, D. J.; Bruce, M. I.; Gaudio, M.; Zaitseva, N. N.; Skelton, B. W.; White, A. H.; Le Guennic, B.; Halet, J.-F.; Fox, M. A.; Roberts, R. L.; Hartl, F.; Low, P. J. Dalton Trans. 2008, 6763. (10) Cordiner, R. L.; Gugger, P. A.; Hill, A. F.; Willis, A. C. Organometallics 2009, 28, 6632. (11) (a) Lalor, F. J.; Desmond, T. J.; Cotter, G. M.; Shanahan, C. A.; Ferguson, G.; Parvez, M.; Ruhl, B. J. Chem. Soc., Dalton Trans. 1995, 1709. (b) Desmond, T.; Lalor, F. J. J. Chem. Soc., Chem. Commun. 1983, 457. (12) (a) Hill, A. F.; Shang, R.; Willis, A. C. Organometallics 2011, 30, 3237. (b) Cordiner, R. L.; Hill, A. F.; Shang, R.; Willis, A. C. Organometallics 2011, 30, 139. (c) Hill, A. F.; Colebatch, A. L.; Cordiner, R. L.; Dewhurst, R. D.; McQueen, C. M. A.; Nguyen, K. T. H. D.; Shang, R.; Willis, A. C. Comments Inorg. Chem 2010, 31, 121. (d) Colebatch, A. L.; Hill, A. F.; Shang, R.; Willis, A. C. Organometallics 2010, 29, 6482. (e) Cordiner, R. L.; Hill, A. F.; Wagler, J. Organometallics 2008, 27, 5177. (13) Enriquez, A. J.; White, P. S.; Templeton, J. L. J. Am. Chem. Soc. 2001, 123, 4992. (14) Mann, P . G.; Purdie, C. D. J . Chem. Soc. 1935, 1560. (15) Data for 4: IR (νCO, cm−1; CD2Cl2): 1936, 1843; 1H NMR (C6D6, 25 °C; 299.9 MHz) δH 5.61 (s, 2 H, pzH), 5.27 (s, 1 H, pzH), 3.20 (s, 6 H, pzCH3), 2.40 (s, 3 H, pzCH3), 2.17 (s, 6 H, pzCH3), 2.05 (virtual t, 4 H, PCH2, 1,3JHH = 9.0 Hz), 2.02 (s, 3 H, pzCH3), 1.53− 1.45 (m, 4 H, PCH2), 1.34−1.29 (m, 8 H, PCH2 and CH2CH3), 1.23− 1.13 (m, 6 H, CH2CH3), 0.96−0.86 (m, 8 H, PCH2 and CH2CH3); 13 C{1H} NMR (C6D6, 25 °C; 75.42 MHz) δC 484.0 (dd, WCNi, 2JPC = 3.73 Hz), 237.4, 232.8 (CO), 153.1, 152.3, 143.9, 143.4 (C3,5(pz)), 107.2, 106.4 (C4(pz)), 18.30 (CH2CH3), 17.91, 15.10, 14.67, 13.98 (pzCH3), 14.35 (CH2CH3), 13.31 (PCH2), 12.16 (CH2CH3), 8.60

Figure 4. Selected molecular orbitals for 5: (a) LUMO; (b) HOMO (see the Supporting Information).

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ASSOCIATED CONTENT

S Supporting Information *

CIF files giving crystallographic data for 4 (CCDC 843503) and 5 (CCDC 843504) and text, tables, and figures giving synthetic and computational details for 4 and 5. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected].

ACKNOWLEDGMENTS This work was supported by the Australian Research Council (No. DP1093516) and the National Computing Facility, Australia (No. y49).

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DEDICATION Dedicated to the inspirational memory of Gordon Stone.

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REFERENCES

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(PCH2CH3), 7.91 (PCH2CH3), 5.46 (PCH2CH3); 31P{1H} NMR (C6D6, 25 °C; 121 MHz) δP 15.74, 8.73, 2JPP = 290.4 Hz; 11B{1H} NMR (C6D6, 25 °C; 96.23 MHz) δB −10.23; acc mass found m/z 843.2571, calcd for [M − Cl]− C30H5211BN658NiO2P2184W 843.905 396; low-res ESI-MS (positive ion) m/z 843.6 [M − Cl]+, 701.7 [M − Ni − PEt3]+, 666.7 [M − NiCl(PEt3)]+. Crystals of 4 suitable for diffractometry were obtained from a cooled concentrated solution of 4 in THF/hexane. Crystal data: C30H52BClN6NiO2P2W; Mr = 879.558; orthorhombic; P212121; a = 10.6496(1) Å; b = 17.6512(2) Å; c = 20.4901(2) Å; V = 3851.69(7) Å3; Z = 4; red needle, 0.07 × 0.15 × 0.24 mm; Dc = 1.517 Mg m−3; μ(Mo Kα) = 3.659 mm−1; T = 200(2) K. A total of 58 569 absorption-corrected reflections (2θ ≤ 60°) provided 11 229 independent reflections, 11 208 of which were observed (|I| > 2σ(|I|)). F2 refinement on all independent reflections using 398 parameters gave R1 = 0.0289 and wR2 = 0.0566 with residual electron densities between −1.36 and +1.21 e Å−3. CCDC 843503. (16) While nickel carbido complexes are unprecedented, there exist copious structural data for nickel alkynyls for the purpose of benchmarking Ni−C(sp) bond lengths. (a) [Ni(CCPh) Cl(PMe3)2] (1.821 Å): Klein, H.-F.; Zweiner, M.; Petermann, A.; Jung, T.; Cordier, G.; Hammerschmitt, B.; Florke, U.; Haupt, H.-J.; Dartiguenave, Y. Chem. Ber. 1994, 127, 1569. (b) [Ni(C CPh)2(PEt3)2] (1.873 Å): Davies, G. R.; Mais, R. H. B.; Owston, P. G. J. Chem. Soc. A 1967, 1750. (17) Data for 5: IR (νCO, cm−1; CD2Cl2) 1881, 1767; H NMR (C6D6, 25 °C; 299.9 MHz) δH 5.47 (s, 2 H, pzH), 5.36 (s, 1 H, pzH), 2.78 (s, 3 H, pzCH3), 2.53 (s, 6 H, pzCH3), 2.21 (s, 6 H, pzCH3), 2.19 (bs, 2 H, PCH2), 2.04 (s, 3 H, pzCH3), 1.79 (t, 3 H, CH2CH3), 1.49 (dd, 10 H, CH2CH3), 1.16 (t, 9 H, CH2CH3, 1JHH = 6 Hz), 0.51 (m, 6 H, PCH2CH3); 13C{1H} NMR (C6D6, 25 °C; 150.90 MHz) δC 280.9 (m, WCPNi), 253.7 (μ-CO), 234.1 (CO, 1JWC = 161.5 Hz), 149.5, 148.7, 140.3, 140.0 (C3,5(pz)), 103.6, 102.7 (C4(pz)), 14.26, 11.44, 9.68, 8.51, 4.28, 1.89 (PCH2 and PCH2CH3); 31P{1H} NMR (C6D6, 25 °C; 121 MHz) δP 35.80 (s, 2JWC = 54.5 Hz), 19.24 (bs); 11B{1H} NMR (C6D6, 25 °C; 96.23 MHz) δB 9.86; acc mass found m/z 843.2571, calcd for [M − Cl]− C30H5211BN658NiO2P2184W 843.905 396; low-res ESI-MS (positive ion) m/z 843.6 [M − Cl]+, 701.7 [M − Ni − PEt3]+, 666.7 [M − NiCl(PEt3)]+. Crystals of 5 suitable for diffractometry were obtained by slow evaporation of a concentrated solution of 5 in benzene. Crystal data: C30H52BClN6NiO2P2W; Mr = 879.558; monoclinic; C2/c; a = 33.8516(4) Å; b = 13.9440(2) Å; c = 16.3341(2) Å; β = 104.0118(7)°; V = 7480.72(17) Å3; Z = 8; brown plate, 0.08 × 0.10 × 0.14 mm; Dc = 1.562 Mg m−3; μ(Mo Kα) = 3.768 mm−1; T = 200(2) K. A total of 103 490 absorption-corrected reflections (2θ ≤ 60°) provided 10 929 independent reflections, 8987 of which were observed (|I| > 2σ(|I|)). F2 refinement on all independent reflections using 397 parameters gave R1 = 0.0293 and wR2 = 0.0636 with residual electron densities between −1.29 and +1.57 e Å−3. CCDC 843504. (18) Anderson, S.; Hill, A. F. J. Chem. Soc., Dalton Trans. 1993, 587. (19) (a) Holmes, S. J.; Schrock, R. R.; Churchill, M. R.; Wasserman, H. J. Organometallics 1984, 3, 476. (b) List, A. K.; Hillhouse, G. L.; Rheingold, A. L. Organometallics 1989, 8, 2010. (c) Jamison, G. M.; White, P. S.; Templeton, J. L. Organometallics 1991, 10, 1954. (d) Jamison, G. M.; White, P. S.; Templeton, J. L. Organometallics 1991, 10, 1954. (e) Li, X.; Stephan, J.; Harms, K.; Sundermeyer, J. Organometallics 2004, 23, 3359. (f) Li, X.; Sun, H.; Harms, K.; Sundermeyer, J. Organometallics 2005, 24, 4699. (g) Li, X.; Schopf, M.; Stephan, J.; Harms, K.; Sundermeyer, J. Organometallics 2002, 21, 2356. (h) Li, X.; Wang, A.; Wang, L.; Sun, H.; Harms, K.; Sundermeyer, J. Organometallics 2007, 26, 1411. (i) Hulley, E. B.; Bonanno, J. B.; Wolczanski, P. T.; Cundari, T. R.; Lobkovsky, E. B. Inorg. Chem. 2010, 49, 8524. (20) (a) Schmidbaur, H.; Pichl, R.; Muller, G. Angew. Chem., Int. Ed. Engl. 1986, 25, 574. (b) Hughes, K. A.; Dopico, P. G.; Sabat, M.; Finn, M. G. Angew. Chem., Int. Ed. Engl. 1993, 32, 554. (c) Rice, G. W.; Ansell, G. B.; Modrick, M. A.; Zentz, S. Organometallics 1983, 2, 154.

(21) (a) Dossett, S. J.; Hill, A. F.; Howard, J. A. K.; Nasir, B. A.; Spaniol, T. P.; Sherwood, P.; Stone, F. G. A. J. Chem. Soc., Dalton Trans. 1989, 1871. (b) Dossett, S. J.; Hill, A. F.; Jeffery, J. C.; Marken, F.; Sherwood, P.; Stone, F. G. A. J. Chem. Soc., Dalton Trans. 1988, 2453.

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dx.doi.org/10.1021/om201057c | Organometallics 2012, 31, 2538−2542