Photochemistry of Fe(CO)5 adsorbed onto porous vycor glass

Fe(CO)/sub 5/ physisorbs onto porous Vycor glass without disruption of its primary coordination sphere. The spectral properties of the adsorbed complex mirror those found in fluid solution, and UV photolysis in vacuo leads to formation of the tetracarbonyl with a quantum yield of unity. The tetracarbonyl rapidly reacts with the PVG surface and chemisorbed water to form the spectrally distinct, oxidative addition products H-Fe(CO)/sub 4/-OSi and H-Fe(CO)/sub 4/-OH. These undergo secondary photolysis to form, depending on the initial loading, either elemental iron or the trimeric cluster Fe/sub 3/(CO)/sub 12/. Diffuse reflectance FTIR spectra, recorded after CW or pulsed laser excitation, establish the presence of dimeric and trimeric intermediates. Trapping experiments with CO and trimethylphosphine indicate a photochemically driven, stepwise reaction sequence in which the so-called mobile intermediate, principally Fe(CO)/sub 3/, reacts with H-Fe(CO)/sub 4/-OH and Fe(CO)/sub 5/(ads) to form dimeric and trimeric products.