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Group 9 Metallacyclopentadienes as Key Intermediates in [2+2+2] Alkyne Cyclotrimerizations. Insight from Activation
Marco Dalla Tiezza1, F Matthias Bickelhaupt2,3, Laura Orian1
1Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35129, Padova, Italy.
Abstract:
The intramolecular oxidative coupling converting a bis-acetylene complex of formula CpM (C2 H2 )2 (Cp=C5 H5- ; M=Co, Rh, Ir) into a 16-electron metallacycle is studied in silico. This reaction is paradigmatic in acetylene [2+2+2] cycloaddition to benzene catalyzed by CpM fragments, being the step with the highest activation energy, and thus affecting the whole catalysis. Our activation strain and quantitative molecular orbital (MO) analyses elucidate the mechanistic details and reveal why cobalt performs better than rhodium and iridium catalysts outlining general principles for rational design of catalysts to be used in these processes.
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In a chemical reaction, a relationship exists between the concentration of reactants and the rate at which the reaction proceeds. The study to measure this relationship is known as the kinetics of a chemical reaction. Kinetic studies are used to deduce the rate law of a chemical reaction, which provides information about the species involved during the transition state of the rate-determining step. Thus, kinetic studies help to derive the mechanism of a...
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When the nucleophile approaches the electrophilic carbon with its lone pairs, the halide acts as a leaving group and moves away with the electron-pair bonded to the carbon. Dotted partial bonds represent the bonds being formed or broken...
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If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not...

