Protonation of manganese phosphonioallenyl complexes

Abstract

The addition of phosphines to the manganese allenylidene complexes Cp(CO) 2Mn C C C(Ph)R (R = H, Ph) proceeds selectively at the C α atom to result in the α-phosphonioallenyl complexes Cp(CO) 2Mn −–C( +PR 3 1) C C(Ph)R. The protonation of the latter affords the η 2-(1,2)-phosphonioallenes Cp(CO) 2Mn{η 2-(1,2)-H C ( +PR 3 1) C C(Ph)R}, rather than the phosphoniovinylcarbenes Cp(CO) 2Mn C( +PR 3 1)–HC C(Ph)R. All complexes obtained are stereochemically rigid and do not isomerize into the η 2-(2,3)-phosphonioallene isomers.