We report a synchrotron-radiation-excited photoemission study of the adsorption of W(CO)6 on Si(111)2 x 1. W(CO)6 is shown to adsorb molecularly on Si at 100 K, and to undergo dissociation at room temperature (RT). Exposure of a reacted surface at 100 K to unmonochromatized synchrotron light results in the formation of a metal layer on Si. Such a metal layer is stable during RT annealing.