Chemistry of Bridging Ketene from Facile Carbonylation of a Ditungsten Methylene Complex with No Metal−Metal Bond

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,η1,η2-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]2W2(μ-CH2) (4a), has been isolated, and its facile carbonylation gives a different ketene complex, Cp2(CO)2[P(OMe)3]2W2(μ,η1,η1-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 affo...