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

The complex [(triphos)(CO) 2 Re(OTf)] ( 1 ) reacts with disubstituted propargyl alcohols HC⋮CCR(R‘)OH in CH 2 Cl 2 at room temperature (R = R‘ = Ph, Me; R = Ph, R‘ = Me), to give either allenylidene derivatives [(triphos)(CO) 2 Re{C C C(R)Ph}]OTf (R = Ph, 2; R = Me, 3 ) or the dinuclear vinylidene−carbene complex [{(triphos)(CO) 2 Re} 2 {μ-(C 10 H 12 )}](OTf) 2 ( 5 ) (R = R‘ = Me) (triphos = MeC(CH 2 PPh 2 ) 3; OTf = CF 3 SO 3 - ). 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) 2 Re{C(OMe)-CH CHMe}]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⋮CCH 2 OH results in the double addition of methanol to give the carbene complex [(triphos)(CO) 2 Re{C(OMe)(CH 2 CH 2 OMe)}]OTf (9 ). When the reaction between 1 and propargyl alcohol is carried out in the dichloromethane dinuclear vinylidene−carbene complex, [{(triphos)(CO) 2 Re} 2 {μ-(C 6 H 6 O)}](OTf) 2 ( 10 ) is obtained.