title: Computational insights into carbon-carbon homocoupling reactions mediated by organolanthanide(III) complexes.
abstract: Homocoupling of terminal alkynes into trienediyl complexes by alkyl samarocenes is known experimentally. By means of computational techniques, we investigated the mechanism of this reaction in detail. The overall reaction sequence is: σ-bond metathesis, dimerisation of metallocenes, and homocoupling of two acetylides into trienediyl. We show that the rate-determining step corresponds to the homocoupling of two anionic acetylides. This coupling takes place at a bis-samarocene dimer complex in which the bridging mode of the two acetylide moieties is critical for the reaction to proceed. The limited energy barrier for the homocoupling of the carbanions originates from a synergistic effect of the two samarium centres within the dimer. Variation of the steric demand of both substrates and lanthanocenes allowed rationalising all the experimental data available for these systems.
authors.affiliation: Université de Toulouse et CNRS, INSA, UPS, UMR 5215, LPCNO, 135 Avenue de Rangueil, F-31077 Toulouse, France. laurent.maron@irsamc.ups-tlse.fr.
authors.forename: Christos E
authors.initials: CE
authors.lastname: Kefalidis
authors.forename: Lionel
authors.initials: L
authors.lastname: Perrin
authors.forename: Laurent
authors.initials: L
authors.lastname: Maron