Reactions of gallium(III) chloride with Li[E(SiMe3)3](E = Si or Ge): crystal structure of (R3Ge)ClGa(µ-OEt)2GaCl(GeR3)(R = SiMe3)

Abstract

Reactions of Li(ER₃)(thf)_x(E = Si or Ge, R = SiMe₃, thf = tetrahydrofuran) with gallium(III) chloride were carried out in diethyl ether with 1 : 1 and 2 : 1 stoichiometries. The 1 : 1 reactions gave products that decomposed upon recrystallization from pentane or drying in vacuo. The NMR spectra were consistent with a mixture of Li[R₃SiGaCl₃](thf)₄(major) and GaCl₂(SiR₃)·thf (minor) in the case of E = Si and GaCl₂(GeR₃)·thf for E = Ge. The 2 : 1 E = Ge reactions gave a mixture of two products exhibiting needle and plate crystal morphologies. The NMR spectra and a partial structure determination identified the former as Li[R₃GeGaCl₃](thf)₄. A full structure determination of the latter showed it to be the diethoxy-bridged dimer, (R₃Ge)ClGa(µ-OEt)₂GaCl(GeR₃). The latter product is thought to result from cleavage of the ether solvent by either Ga₂Cl₆ or the intermediate gallium complex. Possible pathways are discussed.