Organotin compounds bearing mesogenic sidechains: synthesis, X-ray structures and polymerisation chemistry

Organotin compounds R3Sn(CH2)n+2OC6H4C6H4Y (R3=Ph3, Ph2Bu; Y=H, CN; n=1–3) and RX2Sn(CH2)n+2OC6H4C6H4Y (R=Ph, Bu; Y=H, CN; X=Br, I; n=1–3) have been synthesised and characterised by 1H-, 13C-, 119Sn-NMR and Mössbauer spectroscopies. X-ray crystallography reveals tetrahedral geometries for Ph3Sn(CH2)4OC6H4C6H5 and Ph3Sn(CH2)3OC6H4C6H4CN, a six-coordinated, bromine-bridged dimeric structure for PhBr2Sn(CH2)3OC6H4C6H5 containing a mer-Br3C2OSn coordination sphere about tin and a five-coordinated monomeric structure for PhBr2Sn(CH2)3OC6H4C6H4CN. In all cases there is strong alignment of mesogenic groups in the solid-state but only PhBr2Sn(CH2)3OC6H4C6H4CN shows any indication of liquid-crystal behaviour. Wurtz polymerisation of RBr2Sn(CH2)5OC6H4C6H5 (R=Ph, Bu), both of which contain non-chelating ether functions, generated polystannanes (RR′Sn)n with Mn 2.3×105; Mw 3.0×105; Mw/Mn 1.30 and Mn 1.3×105; Mw 2.5×105; Mw/Mn 1.96, respectively, while no polymer was obtained from chelated PhBr2Sn(CH2)3OC6H4C6H5