DIPHENYLPHOSPHIDE DERIVATIVES OF DINEOPENTYLGALLIUM AND DINEOPENTYLINDIUM - CRYSTAL AND MOLECULAR-STRUCTURES OF [(ME3CCH2)2GAPPH2]2 AND [(ME3CCH2)2INPPH2]3

The two compounds (Me3CCH2)2MPPh2 (M = Ga, In) have been prepared by metathetical reactions between (Me3CCH2)2MCl and KPPh2 and fully characterized. The characterization data include elemental analyses (C, H), melting points, IR and H-1 and P-31 NMR spectral studies, cryoscopic molecular weight studies in benzene solution, and single-crystal X-ray structural studies. The gallium compound exists as a dimer in benzene solution and in the solid state. The corresponding indium derivative exists as a monomer-dimer equilibrium mixture in benzene solution and as a trimer in the solid state. Thus, (Me3CCH2)2InPPh2 represents an unusual example of an amphoteric compound that exhibits three different degrees of association. [(Me3CCH2)2GaPPh2]2 crystallizes in the monoclinic space group P2(1)/n (No. 14) with a = 11.076 (3) angstrom, b = 18.996 (3) angstrom, c = 21.753 (5) angstrom, beta = 100.128 (9)degrees, V = 4505 (2) angstrom 3, and Z = 4 (dimeric molecules). The molecule contains a buckled Ga2P2 core (dihedral angles of 142.2-degrees across P(1)...P(2) and 145.6-degrees across Ga(1)...Ga(2)); Ga-P distances are in the range 2.479 (3)-2.512 (3) angstrom, and Ga-C(neopentyl) bond lengths are in the range 1.996 (12)-2.016 (12) angstrom. [(Me3CCH2)2InPPh2]3 crystallizes in the rhombohedral space group R3BAR (No. 148); unit cell parameters (hexagonal setting) are a = 20.873 (5) angstrom, c = 29.037 (4) angstrom, V = 10956 (4) angstrom 3, and Z = 6 (trimeric molecules). The molecules lie on sites of C3 symmetry, their In3P3 cores having a chair conformation. The independent In-P distances are 2.677 (1) and 2.699 (2) angstrom; In-C(neopentyl) bond lengths are 2.182 (6) and 2.210 (7) angstrom.