Structure and Reactivity of Coordinatively Unsaturated Half‐Sandwich Iron, Ruthenium and Osmium Complexes

This review deals with the study of coordinatively unsaturated half‐sandwich iron, ruthenium and osmium complexes, in particular those bearing bulky phosphane ligands. The synthesis, properties and structure of neutral complexes of the type [(C5R5)MX(L)] and their cationic derivatives [(C5R5)M(L)2]+, are described here. We will also refer to related compounds containing hydrotris(pyrazolyl)borate (Tp) ligands, given the formal relationship existing between these and those containing cyclopentadienyl groups. In addition, we discuss the reactivity of these unsaturated species towards small molecules and alkynes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)