The Coordination Chemistry of 3,3′-Diamino-2,2′-bipyridine and Its Dication: Exploring the Role of the Amino Groups by X-ray Crystallography

Abstract

The cover picture shows the pH-dependent coordination chemistry of the potentially ambidentate ligand 2,2′-bipyridine-3,3′-diamine. A dimeric 2:2 complex is formed with copper(II) chloride in which each copper ion is bound to two pyridine nitrogen atoms and two chloride ions in a distorted square-planar arrangement, with a long axial contact from a neighbouring amino group completing a distorted square-pyramidal geometry. Under acidic conditions, both pyridine nitrogen atoms are protonated preventing coordination to the copper(II) ion and as a consequence, the two amino groups together with four chloride ions are bound to the metal ion completing an octahedral coordination sphere. Details are discussed in the article by J. D. Wallis, M. Pilkington et al. on p. 1985 ff.