KINETIC-STUDIES OF OLEFIN BINDING TO SULFIDO SITES IN DINUCLEAR MOLYBDENUM COMPLEXES

The reactions of olefins with a series of molybdenum complexes of the formula (R-CpMo-(mu-S))(2)S(2)CHX, where R = H, CH3, CO2Na, and X = H, CN, CMe(3), have been studied. Olefin reagents have included propene, l-butene, cis- and trans-2-butene, and isomers of hexene. Olefin additions to the sulfide ligands in the dimers result in alkanedithiolate complexes. The rates of these reactions have been monitored by visible spectroscopy, and rate constants, K-on, have been compared as dimer substituent and olefin structure have been varied. The rate constants for olefin dissociation from the alkanedithiolate complexes, k(off), have also been determined by NMR spectroscopy. The studies have permitted us to probe the relative contributions of k(on) and k(off) to the equilibrium constants for reversible olefin binding as inductive and steric effects are varied. The potential for using these systems in olefin separation schemes is discussed.