NCN-Pincer Cobalt Complexes Containing Bis(oxazolinyl)phenyl Ligands

We describe the preparation and characterization of new NCN-pincer Co(III) complexes containing bis(oxazolinyl)phenyl (phebox) ligands as auxiliary ligands. The reaction of Co-2(CO)(8) with the 2-bromo-substituted ligand precursor (phebox-R)Br (1a, R = Me-2; 1b, R = iPr) resulted in the formation of the tricarbonyl Co(I) complex (phebox-R)Co(CO)(3) (2a, R = Me-2; 2b, R = iPr), in which NC-bidentate coordination of the phebox ligand was observed. Complexes 2 underwent oxidative addition of I-2 to give the Co(III) aqua complex (phebox-R)CoI2(H2O) (4a, R = Me-2; 4b, R = iPr) by a change in the coordination geometry to the NCN-tridentate mode. Ligand exchange reactions of H2O or I ligand with CNtBu or AgOAc smoothly proceeded to give the isocyanide complex (phebox-dm)CoI2(CNtBu) (5) or the acetate complex (phebox-dm)Co(kappa(1)-OAc)(kappa(2)-OAc) (6), respectively.