Syntheses and crystal structures of some lithium di- and tri-(thiolato)[tris(trimethylsilyl)methyl]aluminates

Abstract

The first organodi- and organotri-(thiolato)aluminates have been prepared and structurally characterised. They have been obtained by the reactions of [Li(thf)2{AlH3[C(SiMe3)3]}]21 (thf = tetrahydrofuran) with disulfides R2S2 (R = Me, Et or Ph) or thiols RSH (R = Pri, But or Ph). The structure of the methyl compound [Li(thf)2{Al[C(SiMe3)3](SMe)3}] 2 has been determined by X-ray crystallography and shown to comprise lithium organotri(thiolato)aluminates each containing a folded four-membered LiS2Al ring. NMR spectroscopy indicates that the Et, Pri and Ph derivatives have similar structures in solution. Treatment of compound 1 with a three-fold excess of ButSH led to the replacement of only two of the available Al–H bonds and formation of [Li(thf){AlH[C(SiMe3)3](SBut)2}] 6, which contains an almost planar four-membered LiS2Al ring. The derivatives [Li(tmen)2][Al{C(SiMe3)3}(SR)3] (R = But or Ph) have been made by treatment of [Li(tmen)2][AlH3{C(SiMe3)3}] 9 (tmen = N,N,N′,N′-tetramethylethane-1,2-diamine) with RSH, and the But derivative has been shown to crystallise in a lattice containing separated [Li(tmen)2] cations and [Al{C(SiMe3)3}(SBut)3] anions.