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 Co2(CO)8 with the 2-bromo-substituted ligand precursor (phebox-R)Br (1a, R = Me2; 1b, R = iPr) resulted in the formation of the tricarbonyl Co­(I)
complex (phebox-R)­Co­(CO)3 (2a, R = Me2; 2b, R = iPr), in which NC-bidentate
coordination of the phebox ligand was observed. Complexes 2 underwent oxidative addition of I2 to give the Co­(III)
aqua complex (phebox-R)­CoI2(H2O) (4a, R = Me2; 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(κ1-OAc)­(κ2-OAc) (6), respectively.