Novel Supported Catalysts for Terminal Alkene Metathesis

Abstract

Non metathesis active molybdenum oxides supported on TiO2, SiO2, Al2O3, ZrO2 and SnO2 are changed by treating their surfaces with tetramethyltin (SnMe4) into catalysts for terminal alkene metathesis, which accompany no hydrogen shift and isomerization of the produced alkenes. Making use of the advantage some applications are reviewed and the relative activities of metallacyclobutane (MCB) intermediates are elucidated on MoO2.9-2.3/TiO2-SnMe4 with an equimolar mixture of perhydrogenated and perdeuterated alkenes. During treating these supported molybdenum oxides with SnMe4, methane formed. This fact was interpreted such that α-hydrogen abstraction from methyls occurs (2CH3→CH4 + CH2) concurrently with picking up hydrogens from surfaces by methyls (CH3 + H from surface→CH4) and the CH2 species thus formed are grafted onto Mo cations. If Mo=CH2 species predominantly participate in propene metathesis, turnover frequencies are estimated to correspond to more than 0.3 on these supported Mo catalysts. The interaction between MoO3/SiO2 and SnMe4 was studied with X-ray photoelectron spectroscopy.