Hydride-Carbyne to Carbene Transformation in an Osmium-Acetate-bis(triisopropylphosphine) System: Influence of the Coordination Mode of the Carboxylate and the Reaction Solvent
Autores: Tamara Bolaño, Ricardo Castarlenas, Miguel A. Esteruelas y Enrique Oñate
Ref. revista: Organometallics, 26, 2037-2041, (2007)
The bis-solvato hydride-allenylidene complex [OsH(dCdCdCPh2)(CH3CN)2(PiPr3)2]BF4 (1) reacts with acetic acid to give the hydride-carbyne [OsH(2-O2CCH3)(tCCHdCPh2)(PiPr3)2]BF4 (2), which in 1,2-dichloroethane under reflux is stable and does not evolve into its five-coordinate carbene isomer. In acetonitrile at room temperature, complex 2 is in equilibrium with [OsH{1-OC(O)CH3}(tCCHd CPh2)(CH3CN)(PiPr3)2]BF4 (4; ¢H° ) -6.4 ( 0.3 kcalâmol-1, ¢S° ) -22.9 ( 1.1 eu). At 353 K, complex 4 is transformed into the carbene [Os{1-OC(O)CH3}(dCHCHdCPh2)(CH3CN)2(PiPr3)2]BF4
(5; 40%), which is obtained in high yield (88%) by reaction of [Os(dCHCHdCPh2)(CH3CN)3(PiPr3)2]-
[BF4]2 with sodium acetate in 2-propanol. The hydride-carbyne to carbene transformation is analyzed by DFT calculations.
The bis-solvato hydride-allenylidene complex [OsH(dCdCdCPh2)(CH3CN)2(PiPr3)2]BF4 (1) reacts with acetic acid to give the hydride-carbyne [OsH(2-O2CCH3)(tCCHdCPh2)(PiPr3)2]BF4 (2), which in 1,2-dichloroethane under reflux is stable and does not evolve into its five-coordinate carbene isomer. In acetonitrile at room temperature, complex 2 is in equilibrium with [OsH{1-OC(O)CH3}(tCCHd CPh2)(CH3CN)(PiPr3)2]BF4 (4; ¢H° ) -6.4 ( 0.3 kcalâmol-1, ¢S° ) -22.9 ( 1.1 eu). At 353 K, complex 4 is transformed into the carbene [Os{1-OC(O)CH3}(dCHCHdCPh2)(CH3CN)2(PiPr3)2]BF4
(5; 40%), which is obtained in high yield (88%) by reaction of [Os(dCHCHdCPh2)(CH3CN)3(PiPr3)2]-
[BF4]2 with sodium acetate in 2-propanol. The hydride-carbyne to carbene transformation is analyzed by DFT calculations.