Rates of oxidative elimination reactions of tungsten and molybdenum carbonyls with mercuric halides

Abstract

Kinetic data have been obtained for the oxidative elimination reactions of M(CO)4L2 (M = Mo, W; L2 = 2,2'-bipyridine, 1,10-phenanthroline) with mercuric halides which yield M(CO)3L2(HgX)(X) and CO.Both acetone and 1,2-dichloro- ethane were used as solvents.In acetone the reaction involves the initial rapid formation of M(CO)4L2-2HgX2 which de- composes in the rate-determining step to yield the final product.Equilibrium constants for the formation of the inter- mediate have been calculated for the tungsten systems using both HgCl2 and HgBr2.For both compounds studied the equilibrium constant is larger for HgBr2 than for HgCl2.No intermediate is observed for the reactions of the molybdenum compounds, but the kinetic data are consistent with the mechanism proposed for the tungsten systems.In 1,2-dichloro- ethane the kinetic data indicate the presence of both M(CO)4L2'HgX2 and M(CO)4L2 • 2HgX2 as intermediates.