Alkylpolygermanes

Abstract

Germanium di-iodide and trimethylaluminium react at 20° in hexane to form non-cyclic branched-chain methylpolygermanes, Me_{2n+ 2}Ge_n(n= 4–10), and compounds resulting from the growth of alkyl chains (e.g., Me₉Ge₄Et and Me₉Ge₄Pr). Triethylaluminium reacts similarly but also forms Et₆Ge₂ and Et₈Ge₃ whilst Buⁱ₃Al yields the isobutyliodogermanes BuⁱGel₃, Buⁱ₅Ge₂I, and Buⁱ₇Ge₃I. Trimethylgermyl-lithium and GeCl₄ yield (Me₃Ge)₄Ge and (Me₃Ge)₃Ge·Ge(GeMe₃)₃. Preliminary work suggests that chain growth proceeds via Ge–Al intermediates of high reactivity. Methylpolygermanes are also produced in the reaction between bistrimethylgermylmercury and aluminium turnings. The Wurtz reaction between trimethylbromogermane and potassium gives the digermane Me₆Ge₂ in 58% yield together with Me₃Ge·CH₂·Ge₂Me₅ and (Me₃Ge)₄Ge. Hexamethyldigermane is readily chlorinated by GeCl₄ forming Me₅Ge₂Cl which undergoes the Wurtz reaction to form mainly the tetragermane Me₁₀Ge₄. Mass spectra of these alkylpolygermanes are discussed in relation to their structures and observations are reported on their u.v. and i.r. spectra.