Hydride-Alkenylcarbyne to Alkenylcarbene Transformation in Bisphosphine-Osmium Complexes
Autores: Tamara Bolaño, Ricardo Castarlenas, Miguel A. Esteruelas, F. Javier Modrego y Enrique Oñate
Ref. revista: Journal of the American Chemiscal Society, 127, 11184-11195, (2005)
The elongated dihydrogen complex [Os{C6H4C(O)CH3}(è2-H2)(H2O)(PiPr3)2]BF4 (1) reacts with 1,1-diphenyl-2-propyn-1-ol and 2-methyl-3-butyn-2-ol to give the hydride-hydroxyvinylidene-ð-alkynol derivatives [OsH{dCdCHC(OH)R2}{è2-HCtCC(OH)R2}(PiPr3)2]BF4 (R ) Ph (2), Me (3)), where the ð-alkynols act as four-electron donor ligands. Treatment of 2 and 3 with HBF4 and coordinating solvents leads to the dicationic hydride-alkenylcarbyne compounds [OsH(tCCHdCR2)S2(PiPr3)2][BF4]2 (R ) Ph, S) H2O (4), CH3CN (5); R ) Me, S ) CH3CN (6)), which in acetonitrile evolve into the alkenylcarbene complexes [Os(dCHCHdCR2)(CH3CN)3(PiPr3)2][BF4]2 (R ) Ph (7), Me (8)) by means of a concerted 1,2- hydrogen shift from the osmium to the carbyne carbon atom. Treatment of 2-propanol solutions of 5 with NaCl affords OsHCl2(tCCHdCPh2)(PiPr3)2 (10), which reacts with AgBF4 and acetonitrile to give [OsHCl-
(tCCHdCPh2)(CH3CN)(PiPr3)2]BF4 (11). In this solvent complex 11 is converted to [OsCl(dCHCHdCPh2)(CH3CN)2(PiPr3)2]BF4 (12). Complex 5 reacts with CO to give [Os(dCHCHdCPh2)(CO)(CH3CN)2-(PiPr3)2][BF4]2 (15). DFT calculations and kinetic studies for the hydride-alkenylcarbyne to alkenylcarbenetransformation show that the difference of energy between the starting compounds and the transition states,which can be described as è2-carbene species (OsdC(R)H), increases with the basicity of the metallic center. The X-ray structures of 4 and 7 and the rotational barriers for the carbene ligands of 7, 8, and 12 are also reported.
The elongated dihydrogen complex [Os{C6H4C(O)CH3}(è2-H2)(H2O)(PiPr3)2]BF4 (1) reacts with 1,1-diphenyl-2-propyn-1-ol and 2-methyl-3-butyn-2-ol to give the hydride-hydroxyvinylidene-ð-alkynol derivatives [OsH{dCdCHC(OH)R2}{è2-HCtCC(OH)R2}(PiPr3)2]BF4 (R ) Ph (2), Me (3)), where the ð-alkynols act as four-electron donor ligands. Treatment of 2 and 3 with HBF4 and coordinating solvents leads to the dicationic hydride-alkenylcarbyne compounds [OsH(tCCHdCR2)S2(PiPr3)2][BF4]2 (R ) Ph, S) H2O (4), CH3CN (5); R ) Me, S ) CH3CN (6)), which in acetonitrile evolve into the alkenylcarbene complexes [Os(dCHCHdCR2)(CH3CN)3(PiPr3)2][BF4]2 (R ) Ph (7), Me (8)) by means of a concerted 1,2- hydrogen shift from the osmium to the carbyne carbon atom. Treatment of 2-propanol solutions of 5 with NaCl affords OsHCl2(tCCHdCPh2)(PiPr3)2 (10), which reacts with AgBF4 and acetonitrile to give [OsHCl-
(tCCHdCPh2)(CH3CN)(PiPr3)2]BF4 (11). In this solvent complex 11 is converted to [OsCl(dCHCHdCPh2)(CH3CN)2(PiPr3)2]BF4 (12). Complex 5 reacts with CO to give [Os(dCHCHdCPh2)(CO)(CH3CN)2-(PiPr3)2][BF4]2 (15). DFT calculations and kinetic studies for the hydride-alkenylcarbyne to alkenylcarbenetransformation show that the difference of energy between the starting compounds and the transition states,which can be described as è2-carbene species (OsdC(R)H), increases with the basicity of the metallic center. The X-ray structures of 4 and 7 and the rotational barriers for the carbene ligands of 7, 8, and 12 are also reported.