THE REACTION OF DIBENZYLMERCURY WITH SECONDARY PHOSPHINES: FORMATION VERSUS BENZYL SUBSTITUTION

Abstract In an attempt to find a simple, high yield synthetic method to create a phosphorus-phosphorus bond from phosphorus-hydrogen bonds, we have investigated the reaction of dibenzylmercury DBM with secondary phosphines. The overall reaction is: DBM + R2PH→r toluene + Hg + R2P - PR2. Thus reaction of diphenylphosphine with DBM produces the desired coupled product tetraphenyldiphosphine in 85–90% yield. In contrast, the reaction of DBM with 1.3-bis(phenyIphosphino)propane Ph(H)P-(CH2)3-P(H)Ph produces the benzyl-substituted product Ph(Bz)P-(CH2)3-P(Bz)Ph rather than the expected cyclic compound 1,2-diphenyl-1,2-diphospholane PhP-(CH2)3-PPh. The dioxide or disulfide of Ph(H)P-(CH,),-P(H)Ph undergoes no reaction with DBM. The bulky 2.4,6-tris(tertbutyl) phenylphosphine ArPH, with DBM yields diastereomers of the coupled disecondary diphosphine Ar(H)P-P(H)Ar. The reaction of DBM with diphenylchlorophosphine results in a high yield of tetraphenyldiphosphine, but with phenyldichlorophosphine produces the benz...