Tricationic Metal Complexes ([ML][NO₃]₃, M = Ga, In) of N,N‘,N‘‘-Tris(2-pyridylmethyl)- cis-1,3,5-triaminocyclohexane:  Preparation and Structure

The novel hexadentate chelator tachpy, composed of the cis-1,3,5-triaminocyclohexane framework with N-pendant 2-pyridylmethyl arms, forms Ga3+ and In3+ complexes. The solid-state structures of the M(tachpy)3+ units show distortion of the coordination sphere toward trigonal prismatic from octahedral as the metal radius increases. There is also a slight expansion of the triaminocyclohexane nitrogens as the metal radius increases, with concomitant flattening of the cyclohexyl ring. Proton NMR over greater than 4 weeks indicates that Ga(tachpy)3+ is inert to aqueous hydrolysis over the pH range 2−8, while In(tachpy)3+ hydrolyzes immediately under these conditions.