Inorganic and organometallic cobaloximes with dioxime containing Se side chain: Synthesis, characterization and comparison with related B12 model compounds

New series of cobaloximes, RCo(dSePhgH)2Py (R = Cl, Me, Et, n-Pr, n-Bu, Bn, 4–ClC6H4CH2) have been synthesized and characterized by NMR and elemental analysis. Molecular oxygen insertion in the benzyl complexes under photochemical conditions has been carried out and a comparison of its reaction rate with other similar cobaloximes gives the order dmestgH > dSePhgH > dpgH > dSPhgH ≥ dmgH > gH. The molecular structures of ClCo(dSePhgH)2Py, MeCo(dSePhgH)2Py, BnCo(dSePhgH)2Py, 4–ClC6H4CH2Co(dSePhgH)2Py and a dioxy complex Bn(O2)Co(dSePhgH)2Py have been determined by X-ray crystallography. The SePh groups in these complexes adopt either up-down, up-down or down-down, down-down conformations in the solid state depending upon the steric bulk and steric interactions with the axial ligand and also their orientation affects the NMR chemical shifts.