Chemistry of gold(III) with pyridine-carboxamide ligands

摘要

The pyridine-carboxamide ligand PhNHC(=O)-2-C_5H_4N reacts with Na+[AuCl_4]- either by cation exchange, to give [PhNHC(=O)-2-C_5H_4NH][AuCl_4], or by ligand substitution to give [AuCl_2 (k~2-N,N'-PhNC(=O)-2-C_5H_4N)]. Similar reactions with bis(pyridine-carboxamide) ligands gave complexes [AuCl_2(k~2-N,N'-RNC(=O)-2-C_5H_4N)], with R = (CH2)3NHC(=O)-2-C_5H_4N or 2-C_6H_4NHC (=O)-2-C_5H_4N, in which the ligands are bidentate, but no complexes with tetradentate ligands could be isolated. The complex [AuCl_2(k~2-N,N'-PhNC(=O)-2-C_5H_4N)] in methanol solution is an efficient catalyst for oxidative cyanation of PhNMe_2 to give PhMeNCH_2CN, and it is proposed that the catalysis involves gold(I), gold(II) and gold(III) intermediates.