Experimental and computational studies on the reaction of silanes with the diphosphine-bridged triruthenium clusters Ru3(CO)10(μ-dppf), Ru3(CO)10(μ-dppm) and Ru3(CO)9{μ3-PPhCH2PPh(C6H4)}

Abstract

Reactions of Ru3(CO)10(μ-dppf) (1) (dppf = 1,1′-bis(diphenylphosphino)ferrocene), Ru3(CO)10(μ-dppm) (2) (dppm = bis(diphenylphosphino)methane), and the orthometalated derivative Ru3(CO)9{μ3-PPhCH2PPh(C6H4)} (3) with silanes (Ph3SiH, Et3SiH, Ph2SiH2) are reported. Treatment of 1 with Ph3SiH and Ph2SiH2 at room temperature leads to facile Si–H bond activation to afford Ru3(CO)9(μ-dppf)(SiPh3)(μ-H) (4) (60% yield) and Ru3(CO)9(μ-dppf)(SiPh2H)(μ-H) (6) (53% yield), respectively. The reaction of 1 with Ph3SiH has been investigated by electronic structure calculations, and these data have facilitated the analysis of the potential energy surface leading to 4. Compound 1 does not react with Et3SiH at room temperature but reacts at 68 °C to give Ru3(CO)9(μ-dppf)(SiEt3)(μ-H) (5) in 45% yield. Reaction of 2 with Ph3SiH at room temperature yields two new products: Ru3(CO)9(μ-dppm)(SiPh3)(μ-H) (7) in 40% yield and Ru3(CO)6(μ3-O)(μ-dppm)(SiPh3)(μ-H)3 (8) in 15% yield. Interestingly, at room temperature compound 7 slowly reverts back to 2 in solution with decomposition and liberation of Ph3SiH. Complex 8 can also be prepared from the direct reaction between 7 and H2O. Similar reactions of 2 with Et3SiH and Ph2SiH2 give only intractable materials. The orthometalated compound 3 does not react with Ph3SiH, Et3SiH and Ph2SiH2 at room temperature but does react at 66 °C to give Ru3(μ-CO)(CO)7{μ3-PPhCH2PPh(C6H4)}(SiR2R1)(μ-H)](9, R = R′ = Ph, 71% yield; 10, R = R′ = Et, 60% yield; 11, R = Ph, R′ = H, 66% yield) by activation of the Si–H bond. Compounds 4 and 8–11 have been structurally characterized. In 4, both the dppf and the hydride bridge a common Ru–Ru vector, whereas NMR studies on 7 indicate that two ligands span different Ru–Ru edges. Compound 8 contains a face-capping oxo moiety, a terminally coordinated SiPh3 ligand, and three bridging hydride ligands, whereas 9–11 represent simple oxidative addition products. In all of the compounds examined, the triruthenium framework retains its integrity and the silyl groups occupy equatorial sites.