The fragment bis(acetylacetonato)ruthenium: a meeting-point of coordination and organometallic chemistry

Abstract

The classical coordination compound tris(acetylacetonato)ruthenium(III), Ru(acac)3, is a useful precursor to a range of coordination and organometallic complexes containing the fragment Ru(acac)2 in which the metal atom displays the oxidation states +2 and +3. The review summarizes work on the alkene and alkyne complexes, in particular, the behaviour of the ruthenium(III) compounds towards nucleophiles. Reduction of [Ru(acac)3] with zinc in THF/H2O provides a range of coordination and organometallic complexes containing RuII(acac)2, whose chemistry is reviewed. Most of these compounds, including those containing alkenes, undergo reversible one-electron oxidation to their RuIII(acac)2 counterparts, and the alkene-ruthenium(III) cations have been detected by spectroelectrochemistry. The cations derived from the chelate N-donor ligands o-CH2CHC6H4NMe2 and o-PhCCC6H4NMe2 have been isolated and structurally characterized. Comparison of the metrical data establishes that, whereas the alkene is less firmly bound to RuIII than to RuII, the alkyne is bound about as strongly to RuIII as to RuII. Some uncharged nucleophiles (pyridine, diethylamine, PPh3) react with the cationic RuIII complexes to give unusual, paramagnetic RuIII-C σ-bonded chelate complexes.