Ruthenium: Organometallic ChemistryBased in part on the article Ruthenium: Organometallic Chemistry by Ulrich Koelle which appeared in the Encyclopedia of Inorganic Chemistry, First Edition .

Abstract

Abstract In the slightly more than half a century that the organometallic chemistry of ruthenium has had time to develop, it has become clear that the metal's position as the ‘middle child’ of the Group 8 metals is richly reflected in its organometallic derivatives. That is, despite many similarities in the compounds of the iron–ruthenium–osmium triad, addition and elimination reactions of ruthenium, for example, are slower than those of iron but are more facile than those of osmium. Similarly, complexes with hydride and alkyl bonds are generally more stable for ruthenium than for iron, but the ruthenium compounds are often unstable or highly fluxional compared to analogous osmium species. Carbonyl cluster complexes are an important feature of organoruthenium chemistry, and mixed‐ligand carbonyl species with high nuclearity are known, in some cases with more than 10 ruthenium atoms. Interstitial carbides and nitrides are often encountered in ruthenium clusters, and carbonyl hydrides are of interest as hydroformylation catalysts (conversion of alkenes to aldehydes). The cyclopentadienyl ligand is found extensively throughout organoruthenium chemistry, and with a decomposition temperature around 600°C, the sandwich complex ruthenocene Ru(C 5 H 5 ) 2 is among the most stable organometallic compounds known. The stability of ruthenocene and its derivatives allow them to be incorporated as labels into biomolecules such as peptides. Ruthenocene derivatives have also been studied as potential second‐order nonlinear optical materials, and they have played a central role in the development of 30 valence electron triple‐decker cations of the iron group. The high ligand field stabilization of Ru II enables combinations of π‐acceptor ligands together with even the hardest σ‐donors, such as carbonate, sulfate, or nitrate, and hence Ru II carbonyl and phosphine complexes are known with myriad coligand combinations having O, N, or S binding functionalities. In particular, the ability of the (η‐arene)Ru moiety to bind N‐ and O‐ligands has been used to complex various amines, imines, Schiff bases, and amino acids to generate diastereomeric salts, which can serve as chiral catalysts; they are valuable in stereoselective organic syntheses and in the production of biologically active compounds.