Regioselective C-C bond formation between ethylene and alpha-naphthylcarbaldimines catalyzed by Ru-3(Co)12: NMR spectroscopic investigations on the proceeding of the reaction

The reaction of ethylene with imines derived from alpha -naphthylcarbaldehy de catalyzed by Ru-3(CO)(12) leads to the selective and quantitative format ion of products in which one molecule of ethylene has been inserted into th e C-H bond in ortho position with respect to the exocyclic imine substituen t. The stoichiometric reaction of the same ligands with Ru-3(CO)(12) leads to dinuclear ruthenium carbonyl complexes showing the same regioselectivity of C-H activation but the hydrogen atom is shifted in an intramolecular hy drogen transfer reaction towards the former imine carbon atom. If the catal ytic alkylation of alpha -naphthylcarbaldimines is monitored by NMR the occ urrence of the dinuclear product of the stoichiometric reaction is observed before the reaction again quantitatively yields the imines bearing an ethy l group in 2-position of the naphthalene core. This proofs that there must be an equilibrium between the dinuclear ruthenium carbonyl complex which is also observed if alpha -naphthylcarbaldimines are treated with an equimola r amount of Ru-3(CO)(12) and another ruthenium compound where the ethylene might be inserted catalytically into a ruthenium carbon bond. (C) 2001 Else vier Science B.V. All rights reserved.