Five-Coordinate Geometry of Cadmium(II) with Octahedral Bidentate-S,S Complex-Ligand cis(S)-[Co(aet)2(en)]+ (aet = 2-aminoethanethiolate): Synthesis, Crystal Structures and Interconversion of S-Bridged CoIIICdII Polynuclear Complexes

Abstract

Abstract An S-bridged CoIIICdII dinuclear complex molecule, [CdCl3{Co(aet)2(en)}]0 ([1]) (aet = 2–aminoethanethiolate, en = ethylenediamine), was prepared by the reaction of an S-bridged CoIIINiIICoIII trinuclear complex salt, [Ni{Co(aet)2(en)}2]Cl4, with excess CdCl2 in water. Treatment of [1] with NaNO3 in water gave an S-bridged CoIIICdIICoIII dinuclear complex salt, [CdCl{Co(aet)2(en)}2](NO3)3 ([2](NO3)3), which was further converted to a (CoIIICdIICoIII)2 hexanuclear complex salt, [Cd2Cl{Co(aet)2(en)}4](NO3)7 ([3](NO3)7), by treatment with NaNO3 in water. The crystal structures of [1], [2](NO3)3 and [3](NO3)7 were determined by X-ray crystallography. In [1] CdII ion is coordinated by three Cl- ions besides two S atoms from one octahedral C2-cis(S)-[Co(aet)2(en)]+ unit, while each CdII ion in [2]3+ and [3]7+ is coordinated by one Cl- ion besides four S atoms from two C2-cis(S)-[Co(aet)2(en)]+ units. The coordination geometry of each CdII center in [1], [2]3+ and [3]7+ is described as a distorted trigonal-bipyramid, considering an angular structural parameter, χ, which is proposed as a modified index of trigonality. The reverse conversions of [3]7+ to [2]3+ and [2]3+ to [1] were also achieved by treatment with NaCl in water.