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 CH2Cl2 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){mu-(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)(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=CCH2OH results in the double addition of methanol to give the carbene complex [(triphos)(Co)(2)Re{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)(2)Re}(2){mu-(C6H6O)}](OTf)(2) (10) is obtained.