OLEFIN HYDROGENATIONS WITH HYDRIDO(PHOSPHONITE)COBALT(I) UNDER PHOTOIRRADIATION AND EHMO CALCULATIONS FOR THE PHOSPHONITE PHOTODISSOCIATIONPROCESS

Pyrex-filtered photoirradiation of hydrido(phosphonite)cobalt(I) [CoH{ PPh(OEt)(2)}(4)] (CoHL4) brought about catalytic olefin hydrogenations under a dihydrogen pressure of 6 kg/cm(2), and a photogenerated coord inatively unsaturated transient species CoHL3 was presumed to be the k ey-role-playing intermediate in the catalytic reaction cycles. EHMO ca lculations for the Cs-symmetric model complex [CoH{PH(OH)(2)}(4)] dete rmined that photodissociation of a phosphonite ligand (L) proceeded in the equatorial direction, leading to the olefin incorporation on the equatorial site in the course of[CoH(olefin)L-3] intermediate formatio n.