Chemistry of bridging ketene from facile carbonylation of a ditungsten methylene complex with no metal-metal bond

Yu Lee Yang, Luxti Jun Jieh Wang, Ying Chih Lin, Shou Ling Huang, Ming Chou Chen, Gene Hsiang Lee, Yu Wang

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Abstract

The reaction of Cp(CO)3W- (Cp = η5-C5H5) with CH2I2 in CH3CN at -20 °C gives the dinuclear acetylide complex Cp2(CO)6W2(μ-C≡C) (2). When the same reaction is carried out in methanol at -20 °C, a dinuclear ketene complex, Cp2(CO)5W2(μ,η12-CH2CO) (5), is isolated. The oxygen atom of the ketene unit in 5 is weakly coordinated to one of the tungsten metal centers. Upon dissolution in CH3CN at room temperature, complex 5 transforms to 2. A bridging methylene complex, Cp2(CO)4[P(OMe)3]2W 2(μ-CH2) (4a), has been isolated, and its facile carbonylation gives a different ketene complex, Cp2(CO)2[P(OMe)3]2W 2(μ,η11- CH2CO)(μ-CO) (6a), in CH3CN. Treatment of 5 with CO affords Cp2(CO)6W2(μ-CH2CO) (8), which, upon reacting with H2O, ROH (R = Me, Et, PhCH2), and i-PrNH2, generates mononuclear complexes Cp(CO)3WCH2COOH (9), Cp(CO)3WCH2COOR (12a-c), and Cp(CO)3WCH2CONH(i-Pr) (14), respectively. The more stable Cp′ (Cp′ = C5H4Me) analogues 2′, 5′, and 8′ are also prepared. An experiment using a mixture of 5 and 5′ to afford only 2 and 2′ without the crossover product shows that intermolecular coupling is not involved in this transformation. The reaction of 5 with PR3 (R = OMe, Et, Ph) yields only the trans product Cp2(CO)5(PR3)W2(μ-CH 2CO) (10a-c). But the reaction of 5 with t-BuNC gives both the trans and cis products of the ketene complex Cp2(CO)5(t-BuNC)W2(μ-CH2CO) (11). Complexes 2′, 5′, 8′, and 11 have been characterized by single-crystal X-ray diffraction analysis.

Original languageEnglish
Pages (from-to)1573-1580
Number of pages8
JournalOrganometallics
Volume16
Issue number8
DOIs
StatePublished - 15 Apr 1997

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