Synthesis, characterisation and crystal structures of three trinuclear cadmium(II) complexes with multidentate Schiff base ligands

Three novel Schiff base Cd(II) trimeric complexes, [Cd-3(L-1)(2)(SCN)(2)(CF3COO)(2)] (1), [Cd-3(L-1)(2)(SCN)(2)(HCONMe2)] (2) and [Cd-3(L-2)(2){N(CN)(2)}(2)] (3) have been prepared from two different symmetrical Schiff bases H2L1 and H2L2 (where H2L1 = N-1, N-3-bis(salicylideneimino)diethylenetriamine, a potentially pentadentate Schiff base with a N3O2 donor set, and H2L2 = N-1,N-3-bis(3-methoxysalicylideneimino)diethylenetriamine, a potentially heptadentate Schiff base with a N3O4 donor set). All the complexes have been synthesised under similar synthetic procedures and their crystal structures have been established by single crystal X-ray diffraction methods. The ligands and their metal complexes have been characterised by analytical and spectroscopic techniques. Among the three complexes, 1 and 3 are linear whereas 2 is a cyclic trimer. In 1 and 3, all the doubly phenoxo bridged Cd(II) metal centres are in a distorted octahedral environment. In complex 2, two of the three Cd(II) centres reside in a distorted octahedral environment and the remaining one enjoys a monocapped octahedral geometry. Altogether the variety in the bridging mode of two new salen-type ligands has been established through these complexes. (C) 2007 Elsevier Ltd. All rights reserved.