Oligomerization of trimethylsilyl acetylene to form large molecules on reduced surfaces of TiO 2(0 0 1)

Abstract

The catalytic cyclotrimerization of alkynes on reduced TiO 2(0 0 1) surfaces has been explored to probe the active sites for carboncarbon bond formation. The influence of surface–adsorbate interactions on the reaction mechanism was further probed by studies designed to characterize the steric effects of differently functionalized alkynes. The chemistry of trimethylsilyl acetylene on surfaces containing Ti 2+ sites clearly demonstrates that cyclotrimerization of heteroatom-containing alkynes is feasible. Trimethylsilyl acetylene can be cyclized to form tris-(trimethylsilyl)-benzene on the reduced titania surface. However, the principal product on both reduced and stoichiometric surfaces of TiO 2(0 0 1) is the hydrogenation product, trimethylvinylsilane (TMVS). The low yield of oligomeric products is attributed to the steric effect of the bulky trimethylsilyl group.