MATRIX PHOTOCHEMISTRY OF THE COMPLEXES (CO)5CR=C(OME)PH, (CO)5W=C(OME)PH HAVING CLOSE-LYING REACTIVE MLCT AND LF STATES

This article describes the photochemistry of (CO)5 MC(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 CH 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. © 1990.