Non-redox metal ions can promote Wacker-type oxidations even better than copper(II): a new opportunity in catalyst design.

摘要: In Wacker oxidation and inspired Pd(ii)/Cu(ii)-catalyzed C-H activations, copper(ii) is believed to serve in re-oxidizing of Pd(0) the catalytic cycle. Herein we report that non-redox metal ions like Sc(iii) can promote Wacker-type oxidations even better than Cu(ii); both Cu(ii) greatly Pd(ii)-catalyzed olefin isomerization which redox properties are not essential, indicating Lewis acid play a significant role activations addition its properties. Characterization catalysts using UV-Vis NMR indicated adding Sc(OTf)3 acetonitrile solution Pd(OAc)2 generates new Pd(ii)/Sc(iii) bimetallic complex having diacetate bridge serves as key active species for isomerization. Linkage trivalent Pd(ii) makes it more electron-deficient, thus facilitating coordination cation. Due improved electron transfer from cation, benefits nucleophilic attack water on olefinic double bond, leading efficient oxidation. The presence excess prevents palladium(0) black formation, has been rationalized by formation Sc(iii)H-Pd(ii) intermediate. This intermediate inhibits reductive elimination H-Pd(ii) facilitates oxygen insertion form HOO-Pd(ii) intermediate, avoids inactive black. promoted demonstrated here may open up opportunity catalyst design versatile activations.