Effect of Substituents in Functional Bipyridonate Ligands on Ruthenium‐Catalyzed Dehydrogenative Oxidation of Alcohols: An Experimental and Computational Study
Effect of Substituents in Functional Bipyridonate Ligands on Ruthenium‐Catalyzed Dehydrogenative Oxidation of Alcohols: An Experimental and Computational Study
复制标题
功能联吡啶酮酸配体中取代基对钌催化醇脱氢氧化的影响：实验和计算研究
DOI：
10.1002/cctc.202200280
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发表时间：
2022
期刊：
影响因子：
4.5
通讯作者：
Fujita Ken-ichi
中科院分区：
文献类型：
--
作者：
Shimbayashi Takuya;Ito Hajime;Shimizu Mineyuki;Sano Hayato;Sakaki Shigeyoshi;Fujita Ken-ichi
为了开发优良的醇类催化剂，合成了一系列具有4，4 '-功能化的2，2'-联吡啶-6，6 '-二酮（bpyO）配体的六亚甲基钌（HMB）-钌配合物2 - 5，该配合物具有金属-配体协同催化作用.有趣的是，催化活性以3（CF 3）<4（OMe）<2（H）<5（NMe 2）的顺序增加，其中bpyO配体的4，4 '-位上的取代基在括号中。这与简单的给电子能力的顺序不同。DFT计算表明，速率限制步骤是从醇到复合物的协同质子/氢化物转移。随着醇质子与bpyO配体中O原子之间的相互作用增强，活化能降低，NMe 2基团的引入降低了活化能，而CF 3基团的引入则使活化能增加，4的催化活性低于2，这是由于熵-熵补偿效应造成的.
A series of hexamethylbenzene (HMB)–Ru complexes2–5bearing a 4,4’‐functionalized 2,2’‐bipyridine‐6,6’‐dionate (bpyO) ligand, which exhibits metal‐ligand cooperative catalysis, was prepared with the aim of developing excellent catalyst for dehydrogenative oxidation of alcohols. Interestingly, the catalytic activity increased in the order3(CF3) <4(OMe)<2(H) <5(NMe2), where substituents at 4,4’‐positions of bpyO ligand are in parentheses. This is different from the order of simple electron‐donating ability. DFT calculations revealed that the rate‐limiting step is the concerted proton/hydride transfer from the alcohol to the complex. The activation energy decreases as the interaction between the alcoholic proton and the O atom of the bpyO ligand becomes stronger; hence, the introduction of the NMe2group decreases the activation energy, whereas that of the CF3group increases it. The unexpectedly lower catalytic ability of4than that of2results from the enthalpy–entropy compensation effect.