Stoichiometric and Catalytic Activation of Si−H Bonds by a Triruthenium Carbonyl Cluster, (μ<sub>3</sub>,η<sup>2</sup>:η<sup>3</sup>:η<sup>5</sup>-acenaphthylene)Ru<sub>3</sub>(CO)<sub>7</sub>:  Isolation of the Oxidative Adducts, Catalytic Hydrosilylation of Aldehydes, Ketones, and Acetals, and Catalytic Polymerization of Cyclic Ethers

Treatment of the ruthenium cluster (μ<sub>3</sub>,η<sup>2</sup>:η<sup>3</sup>:η<sup>5</sup>-acenaphthylene)Ru<sub>3</sub>(CO)<sub>7</sub> (<b>1</b>) with stoichiometric amounts of trialkylsilanes results in liberation of a CO ligand followed by oxidative addition of a Si−H bond. The trinuclear silyl complexes (μ<sub>3</sub>,η<sup>2</sup>:η<sup>3</sup>:η<sup>5</sup>-acenaphthylene)Ru<sub>3</sub>(H)(SiR<sub>3</sub>)(CO)<sub>6</sub> (<b>2</b>) were isolated in good yield. They were characterized by NMR spectroscopy and X-ray crystallography. Compound <b>1 </b>catalyzes the hydrosilylation of olefins, acetylenes, ketones, and aldehydes. In particular, the reactions of aldehydes and ketones proceed at room temperature to form the corresponding silyl ethers in good yield; the catalytic activities are superior to those with RhCl(PPh<sub>3</sub>)<sub>3</sub>. The RhCl(PPh<sub>3</sub>)<sub>3</sub>-catalyzed hydrosilylation of ketones with Me<sub>2</sub>(H)SiCH<sub>2</sub>CH<sub>2</sub>Si(H)Me<sub>2</sub> results in selective reaction of only one Si−H terminus, while similar reactions, when catalyzed by <b>1</b>, allow utilization of both Si−H groups. Significantly different regio- and stereoselectivities, compared with those obtained in reactions catalyzed by RhCl(PPh<sub>3</sub>)<sub>3</sub>, also were observed in the hydrosilylation of α,β-unsaturated carbonyl compounds and 4-<i>tert</i>-butylcyclohexanone, respectively. The reactions with acetals and cyclic ethers also take place under similar conditions. The reaction of trialkylsilanes with an excess of a cyclic ether resulted in ring-opening polymerization. Polymerization of THF was investigated as a representative example. Treatment of trialkylsilanes with an excess of THF (10−10<sup>2</sup> equiv with respect to silanes) in the presence of a catalytic amount of <b>1</b> resulted in production of polytetrahydrofuran with <i>M</i><sub>n</sub> = 1000−200 000 and <i>M</i><sub>w</sub>/<i>M</i><sub>n</sub> = 1.3−2.0. Changing the ratio of THF to HSiR<sub>3</sub> can control the molecular weight. NMR studies suggested that the structure of the polymer is R<sub>3</sub>SiO−[(CH<sub>2</sub>)<sub>4</sub>O]<i><sub>n</sub></i>−CH<sub>2</sub>CH<sub>2</sub>CH<sub>2</sub>CH<sub>3</sub>. Mechanistic considerations based on differences in the catalytic activities between the catalysts <b>1</b> and <b>2</b> are discussed.