Synthesis and Characterization of Binuclear and Trinuclear Cobalt(III) Complexes With Imidazolate Bridges

Abstract

Two cobalt(III) ammine complexes are described which have an imidazolate ( Im ) ligand bridging cobalt(III) centres . Their electronic absorption spectra, ¹H, ¹³C and ⁵⁹Co n.m.r . spectra, and electrochemical data are presented. One complex is a bis [ pentaamminecobalt (III)] complex, [(H₃N)₅Co( Im )Co(NH₃)₅]⁵⁺, and the other has two pentaammineimidazolatocobalt (III) units coordinated in the cis arrangement to tetraamminecobalt (III). The crystal structure of cis - [(NH₃)₄Co{( Im )Co(NH₃)₅}₂]Cl₂(S₂O₆)₂(OH).3.5H₂O is reported. The crystals in the form of orange needles are monoclinic: Cc, a 20.18(1), b 17.089(9), c 15.395(7) Ǻ, β 123.76(4)°, Z 4. The structure was refined to R 0.079.