Carbonyl substitution chemistry of neutral and cationic triruthenium cluster complexes derived from 1,1-dimethylhydrazine.: Incorporation of two and three phosphane ligands

The reactivity of the neutral triruthenium carbonyl cluster [Ru3(μ-H)(μ3-HNNMe2)(CO)9] (1) and its protonated derivative [Ru3(μ-H)2(μ3-HNNMe2)(CO)9][BF4] (2), both containing a face-capping five-electron donor 1,1-dimethylhydrazido ligand, with an excess of triphenylphosphane and with bis(diphenylphosphanyl)methane (dppm) has been studied. With PPh3, compound 1 gives initially two independent monosubstituted isomeric intermediates that react with more ligand to afford [Ru3(μ-H)2(μ3-HNNMe2)(C6H4PPh2)(PPh3)(CO)6] as the final product. This complex contains terminal and cyclometalated triphenylphosphane ligands attached to the same Ru atoms as the NMe2 and the NH fragments, respectively. The reaction of complex 2 with PPh3 affords, sequentially, the cationic mono-, di- and trisubstituted derivatives [Ru3(μ-H)2(μ3-HNNMe2)(PPh3)n(CO)9−n][BF4] (n=1–3). Unusually, the di- and trisubstituted complexes contain one PPh3 ligand in an axial position. The reaction of complex 1 with dppm gives the disubstituted derivative [Ru3(μ-H)(μ3-HNNMe2)(μ-dppm)(CO)7], which contains the P atoms attached to the same Ru atoms as the NH fragment. Protonation of this complex with [HOEt2][BF4] gives the cationic derivative [Ru3(μ-H)2(μ3-HNNMe2)(μ-dppm)(CO)7][BF4]. However, the reaction of complex 2 with dppm leads to an inseparable mixture of products. Many of these results contrast with those previously known for carbonyl substitution reactions on triruthenium clusters isostructural with compounds 1 and 2 but containing other face-capping five-electron donor ligands. The hardness of the donor atoms of the bridging ligand is presented as an important factor in relation to the observed regioselectivity.