The Important Role of Some Ancillary Ligands in the Chemistry of Carbonylmetal Cluster Complexes − Selected Reactivity of Triruthenium Clusters Containing Deprotonated 2-Aminopyridines

The presence of deprotonated 2-aminopyridines (apy ligands) as face-capping ancillary ligands in carbonyltriruthenium cluster complexes facilitates their reactivity (mild reaction conditions) and increases the regioselectivity of their reactions. This is probably due to the hemilabile character of the apy ligands that help maintain the cluster nuclearity and also provides reaction pathways of low activation energy. Thus, the presence of apy ligands in triruthenium cluster complexes of the type [Ru3(µ-H)(µ3-apy)(CO)9] has allowed an extensive and regioselective derivative chemistry that is surveyed in this review. A comparative study of the reactivity of 2-amino-, 2-mercapto- and 2-hydroxypyridines with triruthenium clusters is followed by a survey of selective reactions of apy-bridged triruthenium cluster complexes that covers substitution processes, protonation reactions, oxidative addition of hydrogen, hydrosilanes and hydrostannanes, reactions with alkynes and diynes, reactions of coordinated alkenyl and ynenyl ligands, synthesis and reactivity of cationic non-hydridic clusters, preparation of higher-nuclearity clusters and some catalytic applications. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)