Revisiting the reactivity of Ru3(CO)12 with PhC≡CPh (diphenylacetylene)‒new findings of a thermic effect towards higher nuclearity

Abstract

In this paper we report tri- and tetranuclear ruthenium carbonyl compounds containing PhC≡CPh ligand showing μ3-η2, μ3-η4, μ4-η2 coordination modes. A one-pot reaction between [Ru3(CO)12] and PhC≡CPh in THF (tetrahydrofuran) at 66 °C gave the new trinuclear compound [Ru3(CO)6(μ-CO)2(μ3-η4-C4Ph4)] (2) in 30% yield together with the previously reported [Ru3(CO)8(μ3-η2-C2Ph2)2] (1) in 25% yield. Compound 1 converts to 2 under refluxing condition in THF. A similar reaction involving [Ru3(CO)12] with PhC≡CPh in refluxing benzene (80 °C) afforded previously reported closo-tetraruthenium compounds [Ru4(CO)12(μ4-η2-C2Ph2)] (3) and [Ru4(CO)10(μ-CO)(μ4-η2-C2Ph2)2] (4) in 25 and 16% yields, respectively along with 2 in 20% yields. Compounds 1, 2 and 4 were characterized by single-crystal X-ray diffraction analysis in addition to IR and 1H NMR spectroscopic methods.