MeReO3/Al2O3 and Me4Sn-activated Re2O7/Al2O3 alkene metathesis catalysts have similar active sites

Abstract

We studied the solid-state NMR signatures of Re₂O₇/Al₂O₃ activated with Me₄Sn (Me₄Sn/Re₂O₇/Al₂O₃), a heterogeneous alkene metathesis catalyst. These studies showed that the activation step with SnMe₄ generates μ-methylene Al-CH₂ReO₃ species, similar to the intermediates observed in MeReO₃/Al₂O₃. The μ-methylene species probably forms through the in situ generation of MeReO₃. These results establish the role of Me₄Sn in this oxide-based heterogeneous catalyst and explain why Me₄Sn/Re₂O₇/Al₂O₃ has a reactivity profile more similar to MeReO₃/Al₂O₃ than parent Re₂O₇/Al₂O₃.