The crystal and molecular structure of chloro-(NN′-bis-salicylidene-ethylenediamine)iron(III) as a hexaco-ordinate dimer

Abstract

The crystal structure of (Fe salen Cl)₂, the product of the reaction of FeCl₃ and NN′-bis-salicylidene-ethylene-diamine, has been determined by three-dimensional single crystal X-ray methods: R= 0·13. The complex crystallises as dark red-brown monoclinic needles in the space group P2₁/c with the unit cell dimensions a= 11·37, b= 6·91, c= 19·16 Å, β= 90·5°. The molecules are dimeric involving the sharing of two ligand oxygen atoms by both iron atoms to give an asymmetric bridging arrangement, similar to that observed in Cu(salen). The octahedral co-ordination of each metal atom is completed by a single covalent iron–chlorine bond; Fe–Cl = 2·29; Fe–O = 1·90, 1·98, and 2·18; Fe–N = 2·10 and 2·10 Å.

Distortions of the non-planar Schiff-base ligands are described and discussed in terms of several concerted mechanisms.