Ruthenium-olefin complexes: Effect of ligand variation upon geometry

The development of a model system to study ruthenium-olefin complexes relevant to the mechanism of olefin metathesis has been reported recently. Upon addition of the ligand precursor 1,2-divinylbenzene to [RuCl2(PY)(2)(H(2)IMes)(=CHPh)] (H(2)IMes= 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene), two ruthenium-olefin adducts are formed. Based on H-1 NMR spectroscopy experiments and X-ray crystallographic analysis, these complexes are assigned as side-bound isomers in which the olefin and HjMes ligands are coordinated cis to each other. Herein is reported an investigation of the generality of these observations through variation of the N-heterocyclic carbene ligand and the ligand precursor.