Synthesis and crystal structures of cobalt(III) complexes containing pyridine-2-selenolato and its oxidation products

A series of mixed cobalt(III) complexes [Co(pySe)(3-n)(N-N)(n)](n+) [pySe = pyridine-2-selenolato (1 -); N-N = 1,2-ethanediamine ten) and 2,2'-bipyridine (bpy); n = 0, 1 and 2] was prepared. The geometrical preference and trans influence of pySe are fairly different from those of pyridine-2-thiolate. These selenolato complexes were oxidized by peracetic acid to give the corresponding pyridine-2-seleninato (pySeO(2)) and pyridine-2-selenonato (pySeO(3)) complexes. The crystal structures of the pySeO(2) and pySeO(3) complexes revealed that the coordination mode change from an original N,Se-four-membered to the N,O-five-membered chelate ring occurred during oxidation and intramolecular hydrogen bonds between the non-coordinated oxygen of pySeO(2) or pySeO(3) and the amine protons of en stabilize the N,O-coordination mode. (C) 2001 Elsevier Science B.V. All rights reserved.