Cobaloximes with pyrazine and their dimetallic complexes

Abstract

Mono- and dinuclear cobaloximes with inorganic anions and pyrazine (Pz) as a base/bridging ligand were synthesized and characterized by 1H, 13C, UV/Vis and IR spectroscopy and X-ray structure analysis. Mononuclear complexes XCo-(dioxime)2Pz were used as precursors for building homo- and heterodimetallic complexes. The X-ray crystal structures of ClCo(dmgH)2Pz, ClCo(dpgH)2Pz, [Co(dpgH) 2(NO2)2]Na, and [Co(dmgH)2(NO 2)2]2[Ag]2·H2O are reported. [Co(dmgH)2(NO2)2] 2[Ag]2·H2O shows two AgI ions in different environments: one is in tetrahedral, whereas the other is in capped trigonal coordination and the metal-organic framework in this molecule shows helical structure. A cyclic voltammetry study in [XCo(dioxime) 2]2-μ-Pz and XCo(dioxime)2Pz [dioxime = dmgH (dimethylglyoximato), dpgH (diphenylglyoximato)] is reported. The reduction, CoIII to CoII and CoII to CoI, is found to be more difficult in [XCo(dpgH)2]2-μ-Pz than in XCo(dpgH)2Pz. The CV data have been interpreted in terms of cobalt anisotropy. © Wiley-VCH Verlag GmbH & Co. KGaA, 2006.