Unusual Rearrangement of [(α-(Silyl)alkyl)alkoxycarbene]tungsten Complexes: X-ray Crystal Structure of (E)-(CO)5W[C(N(CH3)2)CH2CH2CH=C(OCH3)Si(CH3)3]

David W. Macomber, Puttannachetty Madhukar, Robin D. Rogers

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Treatment of the α-lithio carbene anions (CO)5W[C(XR)CH2]Li (3; XR = OCH3, N(CH3)2) with the α,β-unsaturated carbene complexes (CO)5W[C(OCH3)C(SiR′3)=CH2] (4; R′ = CH3, C6H5) followed by quenching the reaction with the appropriate electrophilic reagent EX (EX = (CH3)3SiCl, CF3CO2H, CH2C02H) afforded the a-silylated vinyl ether complexes (CO)5W[C(XR)CH2CH2CH=C(OCH3)SiR′3] (5) in yields ranging from 23 to 89%. For complexes 5 only the isomers having the E configuration about the carbon-carbon double bond of the α-silylated vinyl ether groups were obtained. Treatment of 3b (XR = N(CH3)2) with 4a (R′ = CH3) followed by only column chromatography afforded 5b (XR = N(CH3)2, R′ = CH3) in 10% yield as well as the Gi-bis(carbene))ditungsten complex (CO)5W[C(N(CH3)2)CH2C-H2CH2C(OCH3)]W(CO)5 (6) in 58% yield. On the other hand, treatment of 3b (XR = N(CH3)2) with 4b (R’ = C6H5) followed by HCl at −78 C produced the (μ-bis[(α-(triphenylsilyl)alkyl)carbene])ditungsten complex (CO)5W[C(N(CH3)2)CH2CH2CH(Si(C6H5)3)C(OCH3)]W(CO)5 (7d). Complex 7d underwent clean rearrangement in C6H6 solution at 25 °C to give 5d (XR = N(CH3)2, R′ = C6H5) and W(CO)6. Acidic hydrolysis of the a-trimethylsilylated vinyl ether group in complexes 5a (XR = OCH3, R′ = CH3) and 5b (XR = N(CH3)2, R′ = CH3) resulted in good yields of the corresponding acylsilanes (CO)5W[C(XR)-CH2CH2CH2C(O)Si(CH3)3] (10). Complex 5b (XR = N(CH3)2, R′ = CH3) was also characterized by single-crystal X-ray diffraction methods. Complex 5b crystallizes in the centric P21/n space group with cell constants (at 20 °C) a = 6.840 (7) Å, b = 22.425 (6) Å, c = 13.721 (9) Å, ß = 98.64 (9)°, and = 1.71 g cm−3 for Z = 4. Least-squares refinement based on 2832 independent observed [Fo ≥ 5σ(Fo)] reflections led to a final conventional R value of 0.026.

Original languageEnglish (US)
Pages (from-to)2121-2126
Number of pages6
Issue number7
StatePublished - Jul 1 1991

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