Synthesis and Characterization of New Ruthenium Vinylidene Complexes

The synthesis of three new ruthenium vinylidene complexes I-III with general formula [RuCl2 (=C=CHR)(PCy3)2] (R= p-C6H4CF3 (I), p-C6H4F (II) and C6H9 (III)) has been reported. The vinylidene complexes were isolated as crystalline solids and characterized by 1H, 13C, 19F and 31P NMR, FT-IR spectroscopy, X-ray diffraction and elemental analyses. Due to the electronic repulsion between the chlorines and the steric repulsion between the cyclohexyl ring of PCy3 and the substituent on the vinylidene ligand, the complexes I-III showed a distorted square-pyramidal structure. These complexes exhibited the high catalytic efficiency in the cross-metathesis degradation of challenging natural rubber (NR) in the presence of d-limonene and citrus oils as chain transfer agents.