Dicadmium complexes bearing tetradentate formamidinate ligands with triple helical structures

Reactions of Cd(NO3)(2)(.)4H(2)O with bis(2-pyridyl)formamidine (HDpyF) and bis(6-methyl-2-pyridyl)formamidine (HDMepyF) in CH3OH afforded the dinuclear products, [Cd-2(DpyF)(3)][Cd(NO3)(4)](0.5) (1), and [Cd-2(DMepyF)(3)](NO3) (2). respectively. Their structures were determined by X-ray crystallography. Complex I crystallized in two different space groups with different packing solvents. Both the DpyF(-) and DMepyF(-) ligands are coordinated to the Cd atoms in new tetradentate fashions, forming two chelating and four bridging bonding modes. Each cadmium metal center of the cations is tris-chelated and strongly distorted from octahedral coordination due to the small bite of the DpyF(-) and DMepyF(-) ligands. The molecules of the cations are chiral due to the ligand constraints. They are the first dicadmium complexes bearing formamidinate ligands with triple helical structures. 2002 Elsevier Science B.V. All rights reserved.