Reactions of Ti+ with methanol and acetonitrile clusters. Efficient dehydration of methanol dimer by TiO+

A striking difference in the clustering and reaction efficiencies of Ti+ with methanol and acetonitrile has been observed following the reactions of laser-generated Ti+ with preformed clusters of methanol and acetonitrile. Evidence for a catalytic conversion of methanol dimer into dimethyl ether by TiO+ is presented. The resulting sequence TiO+(CH3OCH3)(CH3OH)n shows enhanced ion intensity at n=4 suggesting the formation of a stable octahedral structure TiO+(CH3OCH3)(CH3OH)4. In contrast to methanol, the major reactions of Ti+ with acetonitrile clusters involve simple clustering producing Ti+(CH3CN)n. The difference in reactivity is attributed to the formation of TiO+ through the reactions of Ti+ with methanol clusters.