PHOTOGENERATED METALCARBONYL SPECIES ON ALUMINA AND PALLADIUM-ALUMINASURFACES

The photochemically-induced CO substitution reactions of [M(CO)(6)], ( M = Mo and W) have been investigated in the presence of triphenylphosp hine (PPh3), gamma-Al2O3 and Pd/y-Al2O3. Two Aluminas having different surface areas (206 and 98 m(2).g(-1)), were used as supports. On the surface, the disubstituted species are present in majority. The trans- [W(CO)(4)(PPh3)(2)] species are in greater concentration, when compare d to the cis one. Moreover, comparing Pd/gamma-Al2O3 (206 m(2).g(-1)) with gamma-Al2O3 (206 m(2).g(-1)), there is a smaller content of metal subcarbonyl species [M(CO)(6-x)L-x, x = 1,2], in the catalyst, probab ly because Pd atoms might promote the decarbonylation reaction. Bridge d CO species could be detected on the case of [W(CO)(6)] reaction on t he Pd/gamma-Al2O3 (96 m(2).g(-1)) surface, after some days, as a resul t of tungstencarbonyl species decomposition and CO adsorption on Pd.