C–H and C–C bond activations of terminal alkynes in the presence of a butterfly-shaped heteronuclear Ru3Au cluster

The reaction of compound [Ru3(CO)10(μ–Cl)(μ–AuPPh3)] (1) with terminal alkynes HCCR; (R = C6H4–4–CH3, C6H3–2,5–(CH3)2, C6H2–2,4,5–(CH3)3, C(CH3) = CH2, Si(CH3)3), under very mild conditions yielded isostructural compounds [Ru3(CO)9(μ–AuPPh3)(μ3–η2–⊥–CCR)] (R = C6H4–4–CH3 (2), C6H3–2,5–(CH3)2 (3), C6H2–2,4,5–(CH3)3 (4), C(CH3)CH2 (5), Si(CH3)3) (6)) respectively; where the alkynes suffer oxidative additions to the metallic fragment coordinating as acetylide groups in a μ3–η2–perpendicular fashion by breaking the C(sp)–H bond of the alkynes. The AuPPh3 fragment remains without change in all compounds. All of these clusters have been characterized in solution by i.r. and n.m.r. spectroscopy and their structures have been established by single crystal X–ray diffraction studies.

The compounds [Ru3(CO)9(μ–AuPPh3)(μ3–η2–⊥–CCR)] (RC6H4–4–CH3 (2), C6H3–2,5–(CH3)2 (3), C6H2–2,4,5–(CH3)3 (4), C(CH3)CH2 (5), Si(CH3)3) (6)) were synthesized by the reaction of the tetranuclear ruthenium–gold cluster [Ru3(CO)10(μ–Cl)(μ–AuPPh3)] (1) with the corresponding terminal alkynes under mild conditions. In every case the acetylide fragment is coordinated in a μ3–η2–perpendicular fashion by breaking the C(sp)–H bond of the alkynes All compounds were studied by NMR spectroscopy in solution and by single crystal X-ray diffraction in the solid state.Figure optionsDownload as PowerPoint slideHighlights
► Synthesis of five new clusters of general formula [Ru3(CO)9(μ–AuPPh3)(μ3–η2–⊥–CCR)].
► Ru3Au carbonyl cluster promote activation of C–H and CC bonds of terminal alkynes.
► Rehybridization of the C(sp)– C(sp) bond was observed in acetylenic carbon atoms.
► The rupture of C(sp)–H bond of terminal alkynes was observed during reactions.
► The analysis of 13C NMR gave the charge alteration and polarization in the CC bond.