METHYLENE-BRIDGED GROUP-13-15 COMPOUNDS, R2MCH2PPH2 (R = CH2CME3, CH2SIME3, M = GA, IN) - CRYSTAL-STRUCTURE OF [(ME3CCH2)2INCH2PPH2]2.C6D6, A MOLECULE CONTAINING AN IN-C-P-IN-C-P RING IN A CHAIR CONFORMATION

A series of compounds of the type R2MCH2PPh2 (R = CH2CMe3, CH2SiMe3; M = Ga, In) has been prepared by metathetical reactions between the appropriate diorganometal halide and LiCH2PPh2 in pentane or Et2O at -78-degrees-C. All compounds were characterized by physical properties, partial elemental analyses (C, H), and cryoscopic molecular weight measurements in benzene solution as well as IR, H-1 NMR, and P-31 NMR spectroscopic data. All appropriate data support the existence of dimeric molecules. The monomeric species dimerize by apparent Lewis acid-base interactions. These interactions are sufficiently strong that the compounds do not form stable adducts with oxygen- or nitrogen-containing Lewis bases. [(Me3CCH2)2InCH2PPh2]2.C6D6 crystallizes in the centrosymmetric triclinic space group P1BAR (No. 2) with a = 13.142 (5) angstrom, b = 15.109 (3) angstrom, c = 15.746 (4) angstrom, alpha = 85.27 (2)-degrees, beta = 67.99 (2)-degrees, gamma = 66.00 (1)-degrees, V = 2639 (1) angstrom 3, and Z = 2. Diffraction data (Mo K-alpha, 2-theta = 4.5-45.0-degrees) were collected on a Syntex P2(1) diffractometer; the structure was solved and refined to R(F) = 6.0% and R(wF) = 6.4% for all 6932 independent reflections (R(F) = 4.5% and R(wF) = 6.2% for those 5495 data with \F(o)\ > 6-sigma(\F(o)\)). The crystal is composed of two crystallographically independent [(Me3CCH2)InCH2PPh2]2 molecules (each having precise C(i) symmetry) and a C6D6 molecule of solvation. The two independent [(Me3CCH2)InCH2PPh2]2 molecules have similar configurations. Each is based upon a six-membered In-CH2-P-In-CH2-P ring with a chair conformation. Bond lengths of interest include In-P = 2.694 (2)-2.703 (2) angstrom, In-CH2 = 2.255 (7)-2.261 (8) angstrom, and In-neopentyl = 2.216 (7)-2.234 (7) angstrom.