IR investigation of Ni(CO)4 interaction with silicalite, ZSM-5, zeolite-Y, and g-Al2O3

The interaction of Ni(CO)4 with Lewis and Brönsted acid centers at the surface of ZSM-5, H-Y, and γ-Al2O3 gives O-bonded adducts with approximate C3v symmetry. The (A1)1 stretching mode essentially localized on carbonyls O-bonded to Lewis acid centers is lowered by about 100-150 cm-1 with respect to the unperturbed carbonyl molecule. The downward shift of the (A1)1 mode is roughly equal to the sum of the upward shifts of the remaining (A1)2 and E modes of the surface adducts. In Ni(CO)4 O-bonded (or hydrogen bonded) to Brönsted sites (H-Y zeolite), the perturbed carbonyl frequency is 40 cm-1 lower than that of the unperturbed carbonyl, while the other modes are practically unaltered. On all samples, upon lowering the pressure, a decomposition process is favored with formation of subcarbonylic species and small neutral particles.