A General Strategy for Open-Flask Alkene Isomerization by Ruthenium Hydride Complexes with Non-Redox Metal Salts

4 years ago

A General Strategy for Open-Flask Alkene Isomerization by Ruthenium Hydride Complexes with Non-Redox Metal Salts

Zhuqi Chen, Wenrui Zheng, Wanling Mo, Zhanao Lv, Haibin Wang, Guochuan Yin, Yue Hu

A homogenous metal hydride (M−H) catalyst for isomerization normally requires rigorous air-free techniques. Here, we demonstrate a highly efficient protocol in which simple non-redox metal ions as Lewis acids can promote olefin isomerization dramatically with a commercially available RuH2(CO)(PPh3)3 complex in an open-flask system. Isomerization can be accomplished within a short time, and a satisfactory selectivity for different types of unsaturated compounds can be obtained. Meanwhile, an excellent turnover number up to 17208 was achieved under air, and open-flask gram-scale experiments further demonstrated the efficiency of the RuH2(CO)(PPh3)3/non-redox-metals system. We used FTIR spectroscopy, GC–MS, NMR spectroscopy and kinetics studies to evidence that in the sluggish RuH2(CO)(PPh3)3 catalyst, bloated PPh3 ligands cause steric hindrance for the coordination of the free alkene. Alternatively, the addition of non-redox metal ions could induce the dissociation of the PPh3 ligand to offer unoccupied coordination sites for the alkene and to form the Mg-bridged adduct OC−Ru−H2−Mg2+ as the highly active species, which benefited the isomerization significantly through the metal hydride addition–elimination pathway. Finally, this strategy was demonstrated as an impactful approach for hydride catalysts of other transition metals such as Os. Open up: Simple non-redox metal salts can promote olefin isomerization dramatically in the form of commercially available metal hydride complexes in an open-flask system.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/cctc.201700687