OXYGEN COMPLEXES OF NICKEL AND PALLADIUM . FORMATION, STRUCTURE, AND REACTIVITIES

Novel oxygen complexes of formula M(O2)(RNC)2 (R = t-butyl and cyclohexyl for M = Ni; R = t-butyl for M = Pd) were prepared by oxygenation of the corresponding zerovalent isocyanide complexes, M(RNC)4 or M(RNC)2. These diamagnetic, thermally relatively unstable oxygen complexes are intermediates in the catalytic oxygenation of alkyl isocyanides. They are insoluble in nonpolar solvents and not monomeric in the solid state. The ir, nmr, and electronic spectra and magnetic data were collected to deduce essentially square-planar structures with an intermolecular axial interaction through the O2 ligand. The chemical behaviors toward reagents of varying donor-acceptor properties were studied to show that reagents of strong electron affinities release oxygen while electron donor reagents, e.g., PR3 and RNC, cause oxygen-atom transfer. The reaction of Ni(O2)(t-BuNC)2 with CH3NC involves incipient formation of Ni(O2)(t-BuNC)2(CH3NC)2 and Ni(O2)(t-BuNC)(CH3NC)2 prior to the oxygen-atom transfer. Ligation of RNCO to Ni(O) was confirmed by isolation of Ni(RNCO)(RNC)2, a product of oxygen-atom transfer. The isocyanate ligand was shown to be quite susceptible to substitution with RNC as required for the catalytic oxygenation of RNC. © 1969, American Chemical Society. All rights reserved.