CRYSTAL-STRUCTURE AND MOLECULAR-GEOMETRY OF W(=CCME3)(=CHCME3)(CH2CME3)(DMPE), A MONONUCLEAR TUNGSTEN(VI) COMPLEX WITH METAL-ALKYLIDYNE, METAL-ALKYLIDENE, AND METAL-ALKYL LINKAGES

[l, 2-Bis(dimethylphosphino)ethane](neopentylidyne)(neopentylidene)(neopentyl)tungsten(VI), W(=CCMe3)-(=CHCMe3)(CH2CMe3)(dmpe)( previously prepared by Clark and Schrock, has been investigated via a three-dimensional single-crystal X-ray diffraction study. The complex crystallizes in the centrosymmetric monoclinic space group P2Jn with a = 9.784 (3) Å, b = 29.200 (8) Å, c = 9.859 (2) Å, β = 109.54 (2)°, V= 2654 (1) A3, mol wt 544.4, Z = 4, and p(calcd)= 1.36 g cm-3. Diffraction data were collected with a Syntex P2: automated four-circle diffractometer using Mo Ka radiation and an w-scan mode of collection. The structure was solved by conventional Patterson, difference Fourier, and full-matrix least-squares refinement techniques, the resulting discrepancy indices being RF = 3.9% and R=F = 3.1% for all 2475 symmetry-independent reflections with 4.5° < 26 < 40° (RF = 3.2% and RwF = 3.1% for those 2199 reflections with I> 3<(I)). The tungsten atom is in a distorted square-pyramidal coordination environment, with the neopentylidyne ligand in the apical site and with the neopentylidene and neopentyl ligands in adjacent basal sites. The tungsten-neopentyl bond length is W-C(ll) = 2.258 (9) A (ZW-C(11)-C(12) = 124.5 (7)°), the tungsten-neopentylidene bond length is W-C(6)= 1.942 (9) Å (/W-C(6)-C(7) = 150.4 (8)°), and the tungsten-neopentylidyne bond length is W-C(l) = 1.785 (8) Å(ZW-C(1)-C(2) = 175.3 (7)°). © 1979, American Chemical Society. All rights reserved.