First Examples of Rhenium-Assisted Activation of Propargyl Alcohols: Allenylidene, Carbene, and Vinylidene Rhenium(I) Complexes

Abstract

The complex [(triphos)(CO)2Re(OTf)] (1) reacts with disubstituted propargyl alcohols HC⋮CCR(R‘)OH in CH2Cl2 at room temperature (R = R‘ = Ph, Me; R = Ph, R‘ = Me), to give either allenylidene derivatives [(triphos)(CO)2Re{CCC(R)Ph}]OTf (R = Ph, 2; R = Me, 3) or the dinuclear vinylidene−carbene complex [{(triphos)(CO)2Re}2{μ-(C10H12)}](OTf)2 (5) (R = R‘ = Me) (triphos = MeC(CH2PPh2)3; OTf = CF3SO3-). The secondary propargyl alcohol HC⋮CCH(Me)OH reacts with 1 in the presence of methanol to give the methoxyalkenyl Fischer-type carbene [(triphos)(CO)2Re{C(OMe)-CHCHMe}]OTf (11). Compound 11 has been authenticated by an X-ray diffraction analysis. The structure of this complex shows the metal center to be surrounded by a fac triphos ligand, by two mutually cis carbonyl groups, and by the organyl ligand in a slightly distorted octahedral geometry. The reaction with HC⋮CCH2OH results in the double addition of methanol to give the carbene complex [(triphos)(CO)2Re{C(OMe)(CH2CH2OMe)}]OTf (9). When the reaction between 1 and propargyl alcohol is carried out in the dichloromethane dinuclear vinylidene−carbene complex, [{(triphos)(CO)2Re}2{μ-(C6H6O)}](OTf)2 (10) is obtained.