Reactions of Monomeric [1,2,4-(Me3C)3C5H2]2CeH and CO with or without H2: An Experimental and Computational Study
- 8 February 2007
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 129 (9) , 2529-2541
- https://doi.org/10.1021/ja066482h
Abstract
Addition of CO to [1,2,4-(Me3C)3C5H2]2CeH, CeH, in toluene yields the cis-( Ce)2(μ-OCHCHO), in which the cis-enediolate group bridges the two metallocene fragments. The cis-enediolate quantitatively isomerizes intramolecularly to the trans-enediolate in C6D6 at 100 °C over 7 months. When the solvent is pentane, Ce(OCH2)Ce forms, in which the oxomethylene group or the formaldehyde dianion bridges the two metallocene fragments. The cis-enediolate is suggested to form by insertion of CO into the Ce−C bond of Ce(OCH2)Ce , generating CeOCH2COCe . The stereochemistry of the cis-enediolate is determined by a 1,2-hydrogen shift in the OCH2CO fragment that has the OC(H2) bond anti-periplanar relative to the carbene lone pair. The bridging oxomethylene complex reacts with H2, but not with CH4, to give CeOMe, which is also the product of the reaction between CeH and a mixture of CO and H2. The oxomethylene complex reacts with CO to give the cis-enediolate complex. DFT calculations on C5H5 model metallocenes show that the reaction of Cp2CeH with CO and H2 to give Cp2CeOMe is exoergic by 50 kcal mol-1. The net reaction proceeds by a series of elementary reactions that occur after the formyl complex, Cp2Ce(η2-CHO), is formed by further reaction with H2. The key point that emerges from the calculated potential energy surface is the bifunctional nature of the metal formyl in which the carbon atom behaves as a donor and acceptor. Replacing H2 by CH4 increases the activation energy by 17 kcal mol-1.Keywords
This publication has 69 references indexed in Scilit:
- Hydrogen for Fluorine Exchange in C6F6and C6F5H by Monomeric [1,3,4-(Me3C)3C5H2]2CeH: Experimental and Computational StudiesJournal of the American Chemical Society, 2004
- Homogeneous Catalysis with Methane. A Strategy for the Hydromethylation of Olefins Based on the Nondegenerate Exchange of Alkyl Groups and σ-Bond Metathesis at ScandiumJournal of the American Chemical Society, 2003
- Density Functional Study of CO Insertion into the Metal−Alkyl Bond in Bis(cyclopentadienyl)−Zr−(CH3)2Organometallics, 2000
- Ab Initio Characterization of the HCOx (x = −1, 0, +1) Species: Structures, Vibrational Frequencies, CH Bond Dissociation Energies, and HCO Ionization Potential and Electron AffinityThe Journal of Physical Chemistry A, 1999
- A density functional study on the activation of hydrogen-hydrogen and hydrogen-carbon bonds by Cp2Sc-H and Cp2Sc-CH3Journal of the American Chemical Society, 1993
- Mono(pentamethylcyclopentadienyl) complexes of cerium(III). Synthesis, molecular structure, thermal stability, and reactivity of (C5Me5)CeX2 (X = 2,6-di-tert-butylphenoxo, CH(SiMe3)2, and N(SiMe3)2) complexesOrganometallics, 1989
- Chemical origins of substituent effects in alkylpentacarbonylmanganese(I) group migration reactionsJournal of the American Chemical Society, 1988
- Fischer-Tropsch intermediates: tris[(.eta.2-formaldehyde)zirconocene] from the carbonylation of a zirconium hydrideJournal of the American Chemical Society, 1983
- Reduction of coordinated carbon monoxide to "zirconoxy" carbenes with permethylzirconocene dihydrideJournal of the American Chemical Society, 1979
- Reduction of carbon monoxide promoted by alkyl and hydride derivatives of permethylzirconoceneJournal of the American Chemical Society, 1978