Aspects of ruthenium and osmium cluster chemistry

In this paper, we survey the synthesis, structure and bonding of a series of cluster carbonyl compounds of ruthenium and osmium containing from three to ten metal atoms. Members of this series include neutral, anionic hydrido and carbido clusters, all of which are derived from their [M 3 (CO) 12 ] parent. In general, the synthesis of these compounds involves the pyrolysis of either [M 3 (CO) 12 ] or, with osmium, some higher nuclearity cluster. The mechanism by which these reactions occur is believed to involve the form ation of highly unstable, unsaturated derivatives. Many of these clusters contain frameworks of metal atoms that may be regarded as fragments of close-packed metallic arrangements; others may be regarded as examples of tetrahedral growth patterns. They exhibit a new and diverse chemistry, much of which may now be understood in terms of simple bonding arguments.