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.