Ligand steric effect on the coordination mode of nitrite ion:: Syntheses and X-ray single crystal structures of trans-[NiL2(ONO)2] and cis-[NiL′2(O2N)]NO2)•H2O [L=2-(aminomethyl)pyridine and L′=(2-aminoethyl)pyridine]

The steric effects of the co-ligands originated from the pi-cloud of the pyridine moiety and from increased aliphatic chain length have been utilized to synthesize two different binding modes of nitrite ion. A red-violet nitrito isomer trans-[NiL2(ONO)21 (1) and a blue-violet nitrito (O,O) isomer cis-[NiL'(2)(O2N)](NO2)-H2O(2) are obtained by adding L and L' to the methatiolic suspension of K-4[Ni(NO2)(6)]H2O [L = 2-(aminomethyl)pyridine and L' = 2-(aminoethyl)pyridine]. No other isomer of complex 1 or 2 is yielded in solution irrespective of the nature of the solvent used or in the solid state. They have been characterized by routine physicochernical studies as well as by X-ray single crystal structure analysis. (C) 2006 Elsevier B.V. All rights reserved.