Synthesis, structure and spectroscopic behaviors of a five- and six-coordinated tri-cobalt(II) cluster: [(CoL) 2(OAc) 2Co]·2C 2H 5OH

Abstract

A tri-nuclear cobalt(II) cluster, [(CoL) 2(OAc) 2Co]·2C 2H 5OH, has been synthesized by the reaction of cobalt(II) acetate tetrahydrate with a novel Salen-type bisoxime chelating ligand, 3,3′-dimethoxy-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol (H 2L), and characterized by elemental analyses, IR spectra, TG-DTA and molar conductances. UV–vis spectroscopic titration in methanol solution clearly indicated the exclusive formation of the 3:2 [Co 3L 2] 2+ cluster. The single-crystal X-ray diffraction determination of the Co(II) cluster shows that there are two acetate ions coordinate to three cobalt(II) ions through Co–O–C–O–Co bridges, and quadruple μ-phenoxo oxygen atoms from two [CoL] chelates also coordinate to cobalt(II) ions. Interestingly, different conformational central ions: five- and six-coordinated geometries were found in the cluster.