Efficient transfer hydrogenation reaction Catalyzed by a dearomatized PN3P ruthenium pincer complex under base-free Conditions

A dearomatized complex [RuH(PN3P)(CO)] (PN3PN, N′-bis(di-tert-butylphosphino)-2,6-diaminopyridine) (3) was prepared by reaction of the aromatic complex [RuH(Cl)(PN3P)(CO)] (2) with t-BuOK in THF. Further treatment of 3 with formic acid led to the formation of a rearomatized complex (4). These new complexes were fully characterized and the molecular structure of complex 4 was further confirmed by X-ray crystallography. In complex 4, a distorted square-pyramidal geometry around the ruthenium center was observed, with the CO ligand trans to the pyridinic nitrogen atom and the hydride located in the apical position. The dearomatized complex 3 displays efficient catalytic activity for hydrogen transfer of ketones in isopropanol.

Graphical abstractA dearomatized PN3P Ru pincer complex (3) efficiently catalyzes transfer hydrogenation of ketones with i-PrOH via metal-ligand cooperation.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Novel PN3P ruthenium pincer complexes were prepared. ► Aromatization–dearomatization through N–H deprotonating was achieved. ► The dearomatized complex efficiently catalyze transfer hydrogenation of ketones.