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

Three novel Schiff base Cd(II) trimeric complexes, [Cd3(L1)2(SCN)2(CF3COO)2] (1), [Cd3(L1)2(SCN)2(HCONMe2)] (2) and [Cd3(L2)2{N(CN)2}2] (3) have been prepared from two different symmetrical Schiff bases H2L1 and H2L2 (where H2L1 = N1,N3-bis(salicylideneimino)diethylenetriamine, a potentially pentadentate Schiff base with a N3O2 donor set, and H2L2 = N1,N3-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.

Graphical abstractThree novel trimeric Cd(II) complexes have been prepared from two different symmetrical Schiff bases. Crystal structures of all the complexes 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 have a distorted octahedral environment. In the complex 2, two out of the three Cd(II) centres reside in a distorted octahedral environment and the remaining one enjoys a monocapped octahedral geometry. Altogether a variety in the bridging mode of two new salen-type ligands has been established.Figure optionsDownload full-size imageDownload as PowerPoint slide