Atomically dispersed palladium catalyzes H/D exchange and isomerization of alkenes via reversible insertion and elimination

Abstract

H/D exchange and hydrogen-mediated isomerization (HMI) of alkenes require the reversible alkene insertion and elimination process. However, heterogeneous metal catalysts with ubiquitous, active hydrogen species involved in the hydrogenation reactions inevitably result in alkane production. We demonstrate in this work that H 2 can be heterolytically activated into H + and H − on the atomically dispersed Pd 1 /Cu 2 O for the selective H/D exchange and HMI of alkenes. While the hydride can selectively mediate the H/D exchange and the HMI of alkenes, the proton transfer for the production of alkanes is inhibited due to the basicity of oxygen atoms on Cu 2 O. Moreover, with enhanced stability at an elevated temperature, the atomically dispersed Pd catalyst supported on Cu 3 N not only shows outstanding selectivity and stability in the HMI of various alkenes, but also exhibits about one order higher activity than the reported homogeneous and heterogeneous catalysts. • Chemo- and regioselective H/D exchange and isomerization of alkene • Direct production of deuterated alkene from alkyne • Heterolytic dissociation of H 2 over atomically dispersed Pd on Cu 2 O • Paired reactive hydride and passivated proton for reversible alkene insertion/elimination H 2 is widely used in catalytic reactions, such as hydrogenation, hydrogen-mediated isomerization (HMI), hydrocracking, etc. Compared with the alkene hydrogenation that requires the addition of two H atoms activated from H 2 onto the C=C bond, the HMI and H/D exchange of alkene can be achieved with the insertion of only one H atom. In the latter case, it is critical to control the reactivity of the activated H species. We now demonstrate that the atomically dispersed Pd 1 /Cu 2 O catalyst can heterolytically activate H 2 into proton and hydride for catalyzing the HMI and H/D exchange of alkene. While the appropriate Pd-H bond strength allows hydride to be utilized in the reversible alkene insertion and elimination, the strong binding of a proton with basic oxygen on Cu 2 O restricts the proton transfer to the alkyl intermediate, thus switching off the alkane production. This finding also implies that some inactive hydrogenation catalysts might be active for the HMI and H/D exchange of alkene. Selective H/D exchange and isomerization of alkenes are achieved over atomically dispersed Pd catalysts via reversible alkene insertion and elimination.