Synthesis and chemistry of bis(borylphosphino)silanes and -germanes

The reactions of Me2SiCl2, Ph2SiCl2, and Ph2GeCl2 with LiP(H)B((NPr2)-Pr-i)(2) in a 1:2 ratio and the reaction of Ph2SiCl2 with LiP(H)B((NPr2)-Pr-i)[N(SiMe3)(2)] in a 1:2 ratio give good yields of the respective diphosphinosilanes, Me2Si[P(H)B((NPr2)-Pr-i)(2)](2) Ph2Si[P(H)B((NPr2)-Pr-i)(2)](2), Ph2Ge[P(H)B((NPr2)-Pr-i)(2)](2), and Ph2Si[P(H)B((NPr2)-Pr-i)[N(SiMe3)(2)]](2). These species, when combined with BuLi in a 1:2 ratio, give lithium diphosphinosilanes and -germanes of the general type (DME . Li)(2){[PB(NR2)(2)](2)ER'2) All Of the species have been characterized by spectroscopic methods. The molecular structures of three of the lithio compounds, (DME . Li)(2){[PB((NPr2)-Pr-i)(2)](2)SiPh2} (11), (DME . Li)(2){[PB((NPr2)-Pr-i)N(SiMe3)(2)](2)SiPh2) (15), and (DME . Li)(2){[PB((NPr2)-Pr-i)(2)](2)GePh2} (13), have been determined by X-ray diffraction techniques. 11 crystallized in the triclinic space group P (1) over bar with a = 11.071(2) Angstrom, b = 14.937(3) Angstrom, c = 18.080(4) Angstrom alpha = 91.31(3)degrees, beta = 101.23(3)4 gamma = 109.95(3)degrees, and Z = 2, and 13 crystallized in the triclinic space group P (1) over bar with a 11.083(1) Angstrom, b = 14.978(2) Angstrom, c = 18.134(2) Angstrom, alpha = 91.17(1)degrees, beta = 101.43(1)degrees, gamma = 110.05(1)degrees and Z = 2. 15 crystallized in the monoclinic space group P2(1)/n with a = 11.939(2) Angstrom, b = 24.516(3) Angstrom, c = 21.572(3) Angstrom, beta = 101.52(1)degrees and Z = 4. The reactions of the lithio compounds were surveyed with R2ECl2 reagents. The metathesis reactions are sluggish, but the 1:1 reaction of (DME Li)(2)( [PB((NPr2)-Pr-i)(2)](2)GePh2) with (Bu2SnCl2)-Bu-t gave the four-membered-ring compound Ph2GePB((NPr2)-Pr-i)(2)Sn(Bu-t)(2)PB (NiPr2)2. The 1:2 reaction of Me-2(Cl)SiSi(Cl)Me-2 with LiP(H)B((NPr2)-Pr-i)(2) yielded the (borylphosphino)silane [Me2SiP(H)B((NPr2)-Pr-i)(2)](2).