title: Mechanism of phosphorus-carbon bond cleavage by lithium in tertiary phosphines. An optimized synthesis of 1,2-Bis(phenylphosphino)ethane
abstract: Conditions influencing the extent of P-C(aryl) vs P-C(alkyl) bond cleavage in the reaction of Ph(2)P(CH(2))(2)PPh(2) with lithium in THF have been investigated. The results complement and elucidate earlier work; they indicate that the mechanism of P-C bond cleavage in tertiary phosphines of this type involves a thermodynamic equilibrium between P-C(aryl) and P-C(alkyl) cleaved radicals and anions, followed by reaction and stabilization of these as lithium salts. The addition of water to the reaction mixture causes a reestablishment of the cleavage equilibrium prior to the formation of the secondary phosphines. A mechanism involving competitive release of leaving groups as the thermodynamically most stable anion or radical has been proposed. The preparation of (R, R)-(+/-)/(R, S)-PhP(H)(CH(2))(2)P(H)Ph by this route has been optimized.
authors.affiliation: Department of Chemistry, University of Wollongong, Wollongong, NSW 2522, Australia, and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia.
authors.initials: J
authors.lastname: Dogan
authors.initials: JB
authors.lastname: Schulte
authors.initials: GF
authors.lastname: Swiegers
authors.initials: SB
authors.lastname: Wild