Redox Conversion of Cobalt(II)‐Diselenide to Cobalt(III)‐Selenolate Compounds: Comparison with Their Sulfur Analogs

The synthesis of the selenium‐based ligand L 1 SeSeL 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 (L 1 SeSeL 1 )Cl 4 ] was obtained in good yield, and its spectroscopic properties closely resemble that of its sulfur analog. Reaction of L 1 SeSeL 1 with Co(II) thiocyanate results in the formation of the cobalt(III) compound [Co(L 1 Se)(NCS) 2 ], similar to reaction of L 1 SSL 1 . The redox‐conversion reactions from the Co(II)‐diselenide compound [Co(L 1 SeSeL 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(L 1 Se)(MeCN) 2 ](SbF 6 ) 2 and [Co(L 1 Se)(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.