Effects of ancillary ligands in acceptorless benzyl alcohol dehydrogenation mediated by phosphine-free cobalt complexes  

作　　者：Yan Xu Lu Wang Junwei Wu Guanzhong Zhai Daohua Sun 

机构地区：[1]Department of Chemical and Biochemical Engineering,College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361005,China [2]Department of Chemical and Biochemical Engineering,National Engineering Laboratory for Green Chemical Productions of Alcohols−Ethers−Esters,College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361005,China [3]Luoyang Ship Material Institute,Luoyang 471039,China

出　　处：《Frontiers of Chemical Science and Engineering》2023年第3期314-325,共12页化学科学与工程前沿（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant No.22078269).

摘　　要：Acceptorless alcohol dehydrogenation stands out as one of the most promising strategies in hydrogen storage technologies.Among various catalytic systems for this reaction,cost-effective molecular catalysts using phosphine-free ligands have gained considerable attention.However,the central challenge for using non-precious metals is to overcome the propensity of reacting by oneelectron pathway.Herein,we synthesized a phosphine-freeη^(5)-C_(5)Me_(5)-Co complex by using the metal-ligand cooperative strategy and compared its activity with analogous catalysts toward acceptorless alcohol dehydrogenation.The catalyst showed excellent performance with a turnover number of 130.4 and a selectivity close to 100%.The improved performance among the class ofη^(5)-C_(5)Me_(5)-Co complexes could be attributed to the more accessible Co center and its cooperation with the redox-active ligand.To further study the systematic structure-activity relationship,we investigated the electronic structures ofη^(5)-C_(5)Me_(5)-Co complexes by a set of characterizations.The results showed that the redox-active ligand has a significant influence on theη^(5)-C_(5)Me_(5)-Co moiety.In the meantime,the proximal O−/OH group is beneficial for shuttling protons.For the catalytic cycle,two dehydrogenation scenarios were interrogated through density functional theory,and the result suggested that the outer-sphere pathway was preferred.The formation of a dihydrogen complex was the rate-determining step with aΔG value of 16.9 kcal∙mol‒1.The electron population demonstrated that theη^(5)-C_(5)Me_(5)ligand played a key role in stabilizing transition states during dehydrogenation steps.This work identified the roles of vital ligand components to boost catalytic performance and offered rationales for designing metal-ligand cooperative nonprecious metal complexes.

关 键 词：acceptorless alcohol dehydrogenation η^(5)-C_(5)Me_(5)-Co metal-ligand cooperation theoretical calculation 

分 类 号：O64[理学—物理化学]