PROTONATION OF CYCLOPROPENE COMPLEXES OF PLATINUM(0) AND THE REDUCTION OF CYCLOPROPENE BY NITROGENASES

The reactions of a series of platinum(0) cyclopropene complexes with H Cl have been studied, and it is shown that the products include both r ing-intact (cyclopropane-type) and ring-opened (propene-type) material s. All products are believed to be formed by hydrocarbon insertions in to transient platinum-hydrogen bonds formed by addition of HCl to plat inum. Mechanistic interpretation is complicated by group migrations, a nd double-bond shifts. Oxidative additon of a sigma-cyclopropyl to pla tinum plays a part in ring-opening reactions, whereas the cyclopropane s are believed to be produced by further hydrocarbon insertions into t ransient platinum-hydrogen bonds. The relevance of these models to the mechanism of reduction of cyclopropene by nitrogenases is discussed. (C) 1998 Elsevier Science S.A. All rights reserved.