Gold(III) Macrocyclic Complexes in Aqueous Solution

Synthesis of 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,6,11,13-tetraenatogold(III) perchlorate is described. The behavior of complex cations of gold(III) with macrocyclic ligands—N,N"-bis(2-aminoethyl)-2,4-pentanediiminatogold(III) (A²⁺) and 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,6,11,13-tetraenatogold(III) (B⁺)—is studied in aqueous solutions. The formation of A²⁺and B⁺complexes and the protonation of a B⁺complex are investigated, and the solubility products are determined for perchlorate salts of A²⁺and B⁺cations. The six-membered -diiminate rings of the complex cation B⁺are suggested to be nonequivalent in aqueous solutions: one of them either undergoes intramolecular rearrangement or becomes entirely open.