Polycarbodiimidogermylene: synthesis, characterization, properties and theoretical studies

Polycarbodiimidogermylene: was prepared by transmetallation between dichlor ogermylene, dioxane (I) and dilithium cyanamide, by transamination between bis(triethylgermyl)carbodiimide and (I), or by dehydrochloration between (I ) and carbodiimide in the presence of triethylamine. The germylene structur e was confirmed by its reactivity with 3,5-di-t-butylorthocatechol, which p reserves the germylene structure, and with 3,5-di-t-butylorthoquinone, whic h leads to the expected spirogermane. The carbodiimide form was evident by its infrared spectrum, in agreement with DFT/B3LYP calculations. Geometry o ptimizations of isomers of the carbodiimide and cyanamide forms for ClGe(NC NGe)(n)Cl (n = 1-3) confirm that the carbodiimide form is thermodynamically more stable by at least 10 kcal mol(-1). By the reaction of polycarbodiimi dogermylene with dimethyldisulfide the number of terminal chlorine atoms in the polymer chains was found to be between 12 and 14 NCN groups per 2 chor ines, as was further confirmed by elemental analyses. Polycarbodiimidogermy lene is a semiconductor, having a volume conductivity of about 10(-2) S cm( -1). Its UV spectrum shows absorptions between 650 and 2000 nm correspondin g to transitions between 0.6 and 1.9 eV, confirming transitions in the forb idden gap. (C) 2000 Elsevier Science B.V. All rights reserved.