Reactions of a hydrido(hydrosilylene)tungsten complex with oxiranes

Reactivity of a hydrido(hydrosilylene)tungsten complex, Cp∗(CO)2(H)Wdouble bond; length as m-dashSi(H)[C(SiMe3)3] (1), toward oxiranes was investigated. Treatment of 1 with racemic mono-substituted oxiranes with a substituent R (R = Ph, vinyl, tBu, or nBu) at room temperature produced dihydrido(vinyloxysilyl)tungsten complexes, (E)- and/or (Z)-Cp∗(CO)2(H)2W{Si(H)(OCHdouble bond; length as m-dashCHR)[C(SiMe3)3]} [(E/Z)-2: R = Ph, (E)-3: R = vinyl, (E)-4: R = tBu, (E/Z)-5: R = nBu] in high yields via regioselective ring-opening of oxiranes. When the substituent R on oxirane was relatively large, (E)-isomers (2, 3, and 4) were obtained predominantly (87–97%), while the substituent was a relatively small nBu group, an approximately 1:1 mixture of (E)- and (Z)-isomers [(E/Z)-5] was obtained. Reaction of 1 with 2,2-dimethyloxirane afforded the corresponding complex, Cp∗(CO)2(H)2W{Si(H)(OCHdouble bond; length as m-dashCMe2)[C(SiMe3)3]} (6), quantitatively. A reaction mechanism is also discussed.