Recent chemistry based on the [RuCp(CH3CN)3]+ cation:: Reappraisal of an old precursor

This article gives an overview of recent chemistry based on the tris-acetonitrile complex [RuCp(CH3CN)(3)](+). Due to the labile nature of the CH3CN ligands, substitution reactions are a dominant feature of this complex. Important derivatives are the highly reactive complexes [RuCp(PR3)(CH3CN)(2)](+) which are a source of the 14e(-) fragment [RuCp(PR3)](+). These species are catalytically active in the redox isomerization of allyl alcohols to give aldehydes and ketones. Furthermore, the cationic complex [RuCp(kappa (1)(P),eta (2)-PPh2CH2CH2CH=CH2)(CH3CN)]PF6 derived from the reaction of [RuCp(CH3CN)(3)](+) with PPh2CH2CH2CH=CH2 is a model compound for studying coupling reactions of olefins and acetylenes. In addition, [RuCp(CH3CN)(3)](+) is a valuable precursor for the synthesis of configurationally stable chiral three-legged piano-stool ruthenium complexes. These are currently being intensively investigated as Lewis acid catalysts in asymmetric synthesis.