Relative Reaction Rates of Olefin Substrates with Ruthenium(II) Carbene Metathesis Initiators

The metathesis of terminal olefins having different steric bulk and different geometries as well as electronically different para-substituted styrenes was studied with the ruthenium-based metathesis initiators trans-(PCy_3)_2Cl_2RuCHR. Bulkier olefins were found to react slower, and trans internal olefins were found to be slower than cis. The kinetic product of all reactions was found to be the alkylidene rather than the methylidene. Observed effects were used to explain the mechanism of ring-opening cross metathesis. No linear electronic effects were observed.