Acceptorless Dehydrogenation And Dehydrogenative Coupling Of Alcohols Catalysed By Protic NHC Ruthenium Complexes

Alcohols are abundant natural and renewable biomass-derivates.Catalytic acceptorless alcohols dehydrogenation(AAD)can obtain carbonyl compounds and be considered as a key step in dehydrogenative coupling reaction of primary and secondary alcohols,giving alkylated ketones or alcohols.The AAD reaction is also related to the field of energy chemistry.The prime objective of this study was designing and synthesizing a new family of Protic NHC complexes.These new and bifunctional metal-ligands coordination complexes have reaction activity in skeleton of ligands and metal center,whith is confirmed by stoichiometric reaction.These protic NHC complexes can act as excellent catalysts for acceptorless dehydrogenation of secondary alcohols and dehydrogenative coupling of primary and secondary alcohols,leading to formation of a variety of carbonyl compounds with releasing H2.This catalytic system represents the advantages of high efficiency and selectivity,whith is expected to be applied in the field of future biomass conversion and catalysis.This study was synthesized a group of original N-heterocyclic carbine Ru complexes via the utilization of tautomerism of phosphine-tethered bidentate ligand with cyclopentadienyl of Ru complexes,which the structures can be confirmed by NMR and single crystal diffraction.Under the optimized condition,protic NHC ruthenium complexes represented good catalytic activity in acceptorless dehydrogenation of aliphatic and aromatic alcohols,giving corresponding acetophenone derivatives in yields of 53-96%.H2 as a by-product is also relevant to the field of energy chemistry.The C-C coupling of primary and secondary alcohols can be achieved by 'borrowing hydrogen'method with protic NHC ruthenium complexes in the preparation a series of selected and alkylated ketone derivatives.The fast selective hydrogenation could be favored by the ability of the catalyst to control the process efficiently,leading to realize the selective and catalytic coupling reaction by reaction mechanism.