Coordination chemistry of a new imine-ether ligand, N,N '-bis(2-pyridylmethylene)-2,2 '-(ethylenedioxy)bis(ethylamine): mono-helical and single-helical-strand coordination modes identified by X-ray crystallography

摘要

A new Schiff base ligand, N,N'-bis(2-pyridylmethylene)-2,2'-(ethylenedioxy)bis(ethylamine), L, and the complexes, [AgL](BF4) (1), [Zn2LCl4] (2), [Hg2LCl4] (3), [Cd2LI4] (4), [Ni2L3](BF4)(4) (5), and [M2L3](ClO4)(4) with M = Co(II) (6) Fe(II) (7) and Zn(II) (8), have been synthesised and characterised crystallographically and spectroscopically. The silver(1) complex 1 consists of a mono-helical structure where one ligand molecule, coordinating in a tetradentate manner, wraps itself around the Ag(1) ion, giving rise to a distorted tetrahedral arrangement. Single-helical-strand binuclear complexes were obtained with zinc(II), mercury(II) and cadmium(II), 2, 3 and 4, respectively. Complexes 2 and 3 are isomorphous and both contain one ligand molecule coordinating to two metal atoms via the two pyridylimine N-atoms. The two remaining coordination sites on the metals are occupied by chlorine atoms. In the fivefold coordinate cadmium(II) complex, 4, the ligand coordinates in a bis-tridentate manner via the two pyridylimine units and the two oxygen atoms. The two remaining coordination sites on the metals are occupied by iodine atoms. It was possible to combine both coordination modes of the ligand, mono-helical and single-helical-strand, in the isomorphous binuclear octahedrally coordinated nickel(II), cobalt(II), iron(II) and zinc(II) complexes, 5-8, respectively. One ligand molecule is wrapped around each metal ion, which in turn are linked by a third ligand molecule, so forming mono-bridged species. (C) 2002 Elsevier Science Ltd. All rights reserved. [References: 37]