Formation of Brønsted acid site on halide clusters of group 5 and 6 transition metals

Molecular halide clusters of Nb, Mo, Ta, and W supported on SiO2 developed catalytic activity for methylation of toluene with methanol when treated above 300 °C. Methylation of xylenes also proceeded. However, the main reaction of trimethyl- and tetramethylbenzenes was isomerization. Demethylation of pentamethyl- and hexamethylbenzenes proceeded. IR analyses of adsorbed pyridine showed the formation of a Brønsted acid site.