Redox conversion of cobalt(II)‐diselenide to cobalt(III)‐selenolate compounds: comparison with their sulfur analogs

Abstract

The synthesis of the selenium-based ligand (LSeSeL1)-Se-1 (2,2'-diselanediylbis(N,N-bis(pyridin-2-ylmethyl)ethan-1-amine) is described along with its reactivity with cobalt(II) salts. The cobalt(II)-diselenide complex [Co-2((LSeSeL1)-Se-1)Cl-4] was obtained in good yield, and its spectroscopic properties closely resemble that of its sulfur analog. Reaction of (LSeSeL1)-Se-1 with Co(II) thiocyanate results in the formation of the cobalt(III) compound [Co((LSe)-Se-1)(NCS)(2)], similar to reaction of (LSSL1)-S-1. The redox-conversion reactions from the Co(II)-diselenide compound [Co((LSeSeL1)-Se-1)Cl-4] using external triggers such as removal of the halide ions or the addition of the strong-field ligand 8-quinolinolate resulted in good yields of the Co(III)-selenolate complexes [Co((LSe)-Se-1)(MeCN)(2)](SbF6)(2) and [Co((LSe)-Se-1)(quin)]Cl. Our computational studies show that the ligand-field splitting energy of the selenium compounds is smaller than their sulfur analogs, indicating that redox-conversion of cobalt(II)-diselenide to cobalt(III)-selenolate complexes may be more arduous than that for the related sulfur compounds.