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 spectroscopic and structural characterization of several monomeric phosphinogallanes wherein gallium and phosphorus are three-co-ordinate. 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 SiMe34). Variable-temperature 1H 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 weak Ga–P π bonding. The synthesis and structures of the related aluminium–phosphorus species But2Al(Et2O)-P(C6H2Pri3-2,4,6)(SiPh3)5 and the gallium–arsenic species But2GaAs[CH(SiMe3)2](SiPh3)6 are also reported. In addition, variable-temperature 1H 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)210 are discussed. Crystal data with Mo-Kα radiation (λ= 0.710 69 Å) at 130 K: 2, monoclinic, space group P21/c, a= 18.499(5), b= 10.028(4), c= 20.746(6)Å, β= 90.45(1)°, Z= 4, R= 0.043; 5, triclinic, space group P, a= 9.488(3), b= 11.416(5), c= 20.383(6)Å, α= 92.07(3), β= 96.80(2), γ= 103.17(3)°, Z= 2, R= 0.079; 6, triclinic, space group P, a= 12.219(3), b= 14.174(3), c= 21.831(5)Å, α= 92.95(2), β= 99.73(2), γ= 99.47(2)°, Z= 4, R= 0.053; 7, monoclinic, space group P21/c, a= 17.710(6), b= 16.635(5), c= 10.838(4)Å, β= 97.43(3)°, Z= 4, R= 0.044; 10, orthorhombic, space group Pbca, a= 16.092(5), b= 16.841(5), c= 18.778(5)Å, Z= 8 and R= 0.050.