Synthesis and structural characterisation of various organosilane-organogermane and organosilane-organostannane statistical copolymers by the Wurtz reductive coupling polymerisation: ~(119)Sn NMR and EXAFS characterisation of the stannane copolymers

摘要

A number of polysilane-based copolymers with organogermanes and organostannanes have been prepared by the Wurtz-type reductive coupling of the corresponding dichlorodiorgano group 14 precursors. The copolymers synthesised were poly(di-n-butylgermane-co-methylphenylsilane), poly(di-n-butylgermane-co-n-hexylmethylsilane), poly(di-n-butylstannane-co-methylphenylsilane) and poly(methylphenylsilane-co-diphenylgermane). Poly(di-n-butylsilane) and poly(di-n-butylgermane) were also synthesised by the room temperature polymerisation of the dichloro-precursors in THF at room temperature and obtained in the highest reported yields to date from a Wurtz-type polymerisation. The polymers and copolymers were characterised by ~1H, ~(13)C, ~(29)Si and ~(119)Sn NMR spectroscopy and UV-vis spectros-copy. The ~(29)Si and ~(119)Sn NMR spectroscopic data provided unambiguous evidence for the incorporation of germane and stannane units into the predominantly polysilane backbones. The ~(119)Sn analysis is the first reported for such copolymers. UV-vis spectroscopy demonstrated that increasing the molar ratios of stannane:silane in the final copolymer led to a red-shift in the observed broad absorption peak. One of the organosilane-organostannane copolymers (PMPS-co-BuSn 2) was analysed by extended X-ray absorption fine-structure spectroscopy (EXAFS) and X-ray absorption near-edge spectroscopy (XANES). Bond lengths were obtained for Sn-Sn (2.82 A), Sn-Si (2.58 A) and Sn-C (2.15 A) and they correspond to those expected for Sn based compounds.