Spirocyclic tin salicyl alcoholates – a combined experimental and theoretical study on their structures, 119Sn NMR chemical shifts and reactivity in thermally induced twin polymerization†
Abstract
The spirocyclic tin salicyl alcoholate, 4H,4′H-2,2′-spirobi[benzo[d][1,3,2]dioxastannine] (1), and its 6,6′-dimethoxy (2) and 8,8′-di-tert-butyl-6,6′-dimethyl derivative (3) were synthesized and thermally induced twin polymerization of precursor 2 was performed to give a SnO2-containing hybrid material. Studies on the molecular structures of 1–3 were carried out using 119Sn{1H} CP MAS NMR spectroscopy and DFT calculations. Crystallization of compound 3 from dimethyl sulfoxide solution provided the Lewis acid–base adduct 3(dmso)2 exhibiting a hexacoordinated tin atom in the solid state, in agreement with the results of the spectroscopic and DFT calculation data. 119Sn NMR spectroscopy of the compounds 1–3 and 3(dmso)2 revealed equilibria among the diverse oligomers in solution phase pointing at hexacoordinated tin atoms.