Ruthenium and osmium vinylidene complexes and some related compounds

A review of the large number of studies completed during the current decade on the chemistry of ruthenium and osmium vinylidene complexes is presented. Interest in these studies arises not only from the reactivity modes and structural properties, but also because vinylidene species play an important role in the selective catalytic transformation of terminal alkynes (polymerization, C-C bond formation in the condensation of alkynes with other substrates, etc.). Attention is mainly focused on the mononuclear compounds, studying their preparative methods where coordinatively unsaturated species and good donor ligands are often involved. Recent methods of synthesis from polyhydrides are also summarized. Metal alkynyl derivatives are closely related to vinylidene complexes, both being common precursors to, and reaction products of vinylidene complexes. Subsequently, l-alkyne and x-alkyne to vinylidene rearrangements on these metal centers are studied. The transformations from vinyl 14 electron to hydride-vinylidene 16 electron species and from hydride-vinylidene to ethylidyne species, etc, are also considered. (C) 1999 Elsevier Science S.A. All rights reserved.