RUTHENIUM MEDIATED CARBON-CARBON AND CARBON-NITROGEN BOND FORMATION -PARAMETERS GOVERNING THE REACTIVITY OF THE METAL CENTER

A series of C,N-cyclometallated N, N-dimethylbenzylamine derivatives, [(C,N-benzylamine)RuCl(eta(6)-arene)] (eta(6)-arene = benzene or para- cymene), have been reacted with various alkynes in order to define the electronic and steric parameters governing the overall heterocyclisat ion reaction. As a general trend the electronic perturbations introduc ed by the substituents on the cycloruthenated substrate have a rather strong influence onto the reactivity of the Ru-center whereas the anci llary eta(6)-arene ligands show a less pronounced effect. The alkynes, ie, their substituents, were found to dramatically alter the course o f the reaction. When the insertion of the alkyne into the Ru-C bond le d to a compound displaying an ester group onto the metallated vinyl C- atom the reaction stopped at this organometallic intermediate whereas for aryl or alkyl substituents the insertion step was instantaneously followed by the C-N bond formation giving an isoquinolinium unit. Thes e latter observations lead us to propose a reductive elimination pathw ay for the formation of the C-N bond.