The [M(NHC)] (M=Pd, Pt) fragment in the synthesis of heteronuclear clusters
Date of Issue2014
School of Physical and Mathematical Sciences
While heteronuclear clusters having phosphine ligands are well-known, those containing nitrogen heterocyclic carbenes (NHCs) seem less explored. This describes work on the synthesis and characterization of new heteronuclear clusters of the heavier groups 8 (Ru and Os) and 10 (Pd and Pt) metals containing nitrogen heterocyclic carbenes (NHC). The reactivity of the [M(NHC)] (where M = Pd or Pt) synthon with various group 8 metal carbonyl clusters afforded a new synthetic methodology for such heterometallic clusters. A number of these clusters have been prepared and fully characterized, and their stability and reactivity investigated. A reasonable mechanism for their formation, supported by computational studies, has been proposed. In the course of this study, it was found that the reaction of free NHCs with the osmium carbonyl cluster Os3(CO)12 afforded a stable, zwitterionic, acyl metalate cluster. This cluster has been isolated and fully characterized, including by an X-ray crystallographic study, and it has been shown to lead to an NHC-substituted cluster. This represents the first direct structural evidence that nucleophilic substitution in carbonyl complexes involves initial nucleophilic attack at a carbonyl ligand.