Hydrogenolysis of Dinuclear PCN^R Ligated Pd^II μ‐Hydroxides and Their Mononuclear Pd^II Hydroxide Analogues

Abstract

The hydrogenolysis of mono-and dinuclear Pd II hydroxidesw as investigated both experimentally and computationally.I tw as found that the dinuclear m-hydroxidereact with H 2 to form the analogous dinuclear hydride species {[(PCN R )Pd] 2 (m-H)}(OTf). The dinuclear m-hydride complexes were fully characterized, and are rare examples of structurally characterizedu nsupported singly bridged m-H Pd II dimers. The {[(PCN Me )Pd] 2 (m-OH)}(OTf) hydrogenolysis mechanism was investigated through experimentsa nd com-putations. The hydrogenolysis of the mononuclear complex (PCN H )Pd-OHr esulted in am ixed ligand dinuclears pecies [(PCN H )Pd](m-H)[(PCC)Pd] (PCC = ad ianionic version of PCN H boundt hrough phosphorus P, aryl C, and pyrazole Ca toms) generated from initial ligand "rollover" CÀHa ctivation. Further exposure to H 2 yields the bisphosphine Pd 0 complex Pd[(H)PCN H ] 2 .When the ligand was protected at the pyrazole 5-position in the (PCN Me )PdÀOH complex, no hydride formed under the same conditions;t he reactionp roceeded directly to the bisphosphine Pd 0 complex Pd[(H)PCN Me ] 2 .R eaction mechanisms for the hydrogenolysis of the monomeric and dimerichydroxides are proposed.[a] Dr.Supporting information (selected crystallographic parameters of the solved XRD structures, NMR spectra of all the described compounds, further computationald etails)a nd the ORCID identification number(s) for the author(s) of this article can be found under:h ttps://doi.