Synthesis and characterization of the monomeric phosphinogallanes But2GaPR′R″(R′, R″= bulky aryl or silyl groups) and related compounds

Abstract

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 Bu^t₂GaP(R)(SiPh₃)(R = C₆H₂Bu^t₃-2,4,6 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 Bu^t₂Al(Et₂O)-P(C₆H₂Prⁱ₃-2,4,6)(SiPh₃)5 and the gallium–arsenic species Bu^t₂GaAs[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 = C₆H₂Bu^t₃-2,4,6 7, C₆H₂Prⁱ₃-2,4,6 8 or C₆H₂Me₃-2,4,6 9) as well as the X-ray structures of (Ph₃Si)P(C₆H₂Bu^t₃-2,4,6)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.