Photochemical synthesis and spectroscopic characteristic of the first vinylsilane carbonyl complexes of tungsten(0)

A series of new vinylsilane complexes of the type [W(CO)5(η2-H2CCHSiR3)] (1a–e) and trans-[W(CO)4(η2-H2CCHSiR3)2] (2a–e) (R = Me, OMe, OCH2CH2OMe, and Cl) have been synthesized photochemically and characterized by IR and 1H, 13C and 29Si NMR spectroscopy. The values of the coordination shifts of the vinylic protons and carbons, Δδ = δ (free vinylsilane) − δ (coordinated vinylsilane), strongly suggest that trimethylvinylsilane (a) is coordinated more loosely to the tungsten atom in compounds of type 1 and 2 than other vinylsilanes (b–e). The strongest dπ–π* interaction takes place between the carbonyltungsten moiety and trichlorovinylsilane. Analysis of 13C NMR data of vinylsilane compounds revealed that the electron-donating methyl substituents and the electron-withdrawing chlorine substituents at the silicon atom cause opposite deviations from the ideal symmetrical η2-coordination of vinylsilane to the tungsten atom. The bis(vinylsilane) complexes 2a–e are shown to exist in several isomeric forms, whose solution dynamics were investigated by variable-temperature 1H NMR studies.

A series of new vinylsilane complexes of the type [W(CO)5(η2-H2CCHSiR3)] (1a–e) and trans-[W(CO)4(η2-H2CCHSiR3)2] (2a–e) (R = Me, OMe, OCH2CH2OMe, and Cl) have been synthesized photochemically and characterized by IR and 1H, 13C and 29Si NMR spectroscopy. The bis(vinylsilane) complexes 2a–e are shown to exist in several isomeric forms.Figure optionsDownload as PowerPoint slide