CO-induced ring-slippage reactions of molybdenocene and tungstenocene carbonyl complexes. Electrochemical and elevated-pressure infrared evidence for an electron-transfer catalysis
Abstract Infrared studies at a CO pressure of 120 bar show (η 5 -C 5 H 5 ) 2 W(CO) to be completely resistant to an excess of CO in the absence of oxidants, but cyclovoltammetric measurements with this complex and with (η 3 -C 5 H 5 )(η 5 -C 5 H 5 )W(CO) 2 in THF solution at 0°C indicate that the ring-slipped dicarbonyl complex is catalytically generated by a one-electron oxidation of the tungstenocene monocarbonyl under CO at ambient pressure. Similar results are found for the reaction of (η 5 -C 5 H 5 ) 2 Mo(CO) with CO.
Equilibria and kinetics in the CO-induced, reversible disproportionation of ((C5H5)2TiCl)2 to (C5H5)2TiCl2 and (C5H52Ti(CO)2. An IR study at elevated CO gas pressures
Abstract IR studies of toluene solutions of ((C 5 H 5 ) 2 TiCl) 2 under elevated CO pressures indicate the formation of a carbonyl complex, probably (C 5 H 5 ) 2 Ti(CO)Cl, with ν(CO) 2068 cm − . This species predominates at CO pressures above 100 bar, and is reasonably stable at temperatures around −30°C. At higher temperatures, disproportionation to (C 5 H 5 ) 2 Ti(CO) 2 and (C 5 H 5 ) 2 TiCl 2 occurs. This disproportionation is reversible; at +30°C and 1 bar of CO, roughly equal concentrations of ((C 5 H 5 ) 2 TiCl) 2 and of dicarbonyl and dichloride products are in equilibrium with each other. Practically complete formation of these products occurs at CO pressures above 10 bar. Rate laws and reaction mechanisms have been studied for the disproportionation reaction and for its reverse, the comproportionation of (C 5 H 5 ) 2 Ti(CO) 2 and (C 5 H 5 ) 2 TiCl 2 to ((C 5 H 5 ) 2 TiCl) 2 , which predominates at lower CO pressures.
Highly enantio- and diastereoselective synthesis of β-methyl-γ-monofluoromethyl-substituted alcohols.
Enanatiopure β-methyl-γ-monofluoromethyl alcohols were prepared from the allylic alkylation between fluorobis(phenylsulfonyl)methane with Morita-Baylis-Hillman carbonates. The reaction was catalyzed by using the Cinchona alkaloid derivative, (DHQD)(2)AQN. The origin of the stereoselectivity was verified by DFT methods. Calculated geometries and relative energies of various transition states strongly support the observed stereoselectivity.