SYNTHESIS AND CHARACTERIZATION OF THE MONOMERIC PHOSPHINOGALLANES BU(T)(2)GAPR'R'' (R', R'' = BULKY ARYL OR SILYL GROUPS) AND RELATED-COMPOUNDS

The use of bulky substituent groups has allowed the isolation and spec troscopic and structural characterization of several monomeric phosphi nogallanes wherein gallium and phosphorus are three-coordinate. These new compounds have the formula But2GaP(R)(SiPh3) (R = C6H2But3-2,4,6 1 , C6H2Pri3-2,4,6 2, C6H2Me3-2,4,6 3 or SiMe3 4). Variable-temperature H-1 NMR studies indicate that there is a rotational barrier of ca. 12. 7 kcal mol-1 around the Ga-P bond in 1 which has been attributed to we ak Ga-P pi bonding. The synthesis and structures of the related alumin ium-phosphorus species But2Al(Et2O)-P(C6H2Pri3-2,4,6)(SiPh3) 5 and the gallium-arsenic species But2GaAs[CH(SiMe3)2](SiPh3) 6 are also report ed. In addition, variable-temperature H-1 NMR studies of the precursor asymmetric phosphines (Ph3Si)P(R)H (R = C6H2But3-2,4,6 7, C6H2Pri3-2, 4,6 8 or C6H2Me3-2,4,6 9) as well as the X-ray structures of (Ph3Si)P( C6H2But3-2,4,6)H 7 and (Ph3Si)P(SiMe3)2 10 are discussed. Crystal data with Mo-Kalpha radiation (lambda = 0.710 69 angstrom) at 130 K: 2, mo noclinic, space group P2(1)/c, a = 18.499(5), b = 10.028(4), c = 20.74 6(6) angstrom, beta = 90.45(1)degrees, Z = 4, R = 0.043; 5, triclinic, space group P1BAR, a = 9.488(3), b = 11.416(5), c = 20.383(6) angstro m, alpha = 92.07(3), beta = 96.80(2), gamma = 103.17(3)degrees, Z = 2, R = 0.079; 6, triclinic, space group P1BAR, a = 12.219(3), b = 14.174 (3), c = 21.831(5) angstrom, alpha = 92.95(2), beta = 99.73(2), gamma = 99.47(2)degrees, Z = 4, R = 0.053; 7, monoclinic, space group P2(1)/ c, a = 17.710(6), b = 16.635(5), c = 10.838(4) angstrom, beta = 97.43( 3)degrees, Z = 4, R = 0.044; 10, orthorhombic, space group Pbca, a = 1 6.092(5), b = 16.841(5), c = 18.778(5) angstrom, Z = 8 and R = 0.050.