Matrix photochemistry of the complexes (CO)5M = C(OMe)Ph (M = Cr, W) having close-lying reactive MLCT and LF states

Article abstract of DOI:10.1016/0022-328X(90)85082-A

This article describes the photochemistry of (CO)5M=C(OMe)Ph (M = Cr, W) in inert gas matrices as 10 K at different irradiation wavelengths.The reactions were studied by following the IR spectral changes in the carbonyl and carbene stretching region.Irradiation with visible light into the low-energy MLCT band resulted in complete conversion of the complexes from anti- into syn-configurations.A similar isomerization reaction occurred as the primary photoprocess upon irradiation into the LF band at ca. 350 nm but this reaction was followed by release of CO as a secondary photoprocess, and in the case of the W-complex a subsequent third photochemical reaction was also observed.The photoproduct of this last reaction appeared to be coordinatively saturated, although it still contained a W(CO)4-moiety.In agreement with an earlier proposal based on flash-photolysis data, it is suggested that a C-H bond of the carbene methoxy group interacts with W via a two-electron, three-centre bond, thus occupying the open site at the metal.Conclusions are drawn about the reactivity of the MLCT and LF states of the isomers.