A process for the preparation of palladium and platinum organometallic complexes in the zerovalent state is described. The process comprises contacting a palladium or platinum compound containing palladium or platinum ions having a valence of at least +1 with complexing ligands such as phosphines, phosphites, arsines, stibines, olefins, and the like. The contacting is carried out in the liquid phase and in the presence of an alcoholic media and in the substantial absence of oxygen preferably at elevated temperatures. The products have known utility as catalysts, for example, in butadiene dimerization reactions, additionally they are useful as catalysts for butadiene co-trimerization reactions with compounds containing an active hydrogen, as well as oxidation reactions.