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首页> 外文期刊>ACS catalysis >Y Mechanism of N,N,N-Amide Ruthenium(II) Hydride Mediated Acceptor less Alcohol Dehydrogenation: Inner-Sphere beta-H Elimination versus Outer-Sphere Bifunctional Metal-Ligand Cooperativity
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Y Mechanism of N,N,N-Amide Ruthenium(II) Hydride Mediated Acceptor less Alcohol Dehydrogenation: Inner-Sphere beta-H Elimination versus Outer-Sphere Bifunctional Metal-Ligand Cooperativity

机译：N，N，N-氨基钌（II）氢化物介导的受体少醇脱氢的Y机理：内球β-H消除与外球双功能金属配体的协同作用

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The reversible transformations between ketones and alcohols via sequential hydrogenation dehydrogenation reactions are efficiently achieved using a single precatalyst HRu(bMepi)(PPh3)(2) (bMepi = 1,3-bis(6'-methyl-2'-pyridylimino)isoindolate). The catalytic mechanism of HRu(bMepi)(PPh3)(2) mediated acceptorless alcohol dehydro-genation (AAD) has been investigated by a series of kinetic and isotopic labeling studies, isolation of intermediates, and evaluation of Ru(b4Rpi)(PPh3)(2)Cl (R = H, Me, Cl, OMe, OH) complexes. Two limiting dehydrogenation scenarios are interrogated: inner-sphere beta-H elimination and outer-sphere bifunctional double hydrogen transfer. Isotopic labeling experiments demonstrated that the proton and hydride transfer in a stepwise manner. Catalyst modifications suggest that the imine group on the bMepi pincer scaffold is not necessary for catalytic alcohol dehydrogenation. Evaluation of the kinetic experiments and catalyst modifications suggests a pathway whereby HRu(bMepi)(PPh3)(2) operates via the inner-sphere beta-H elimination mechanism. Following a single PPh3 dissociation, an alcohol substrate can bind and undergo proton transfer followed by a turnover-limiting beta-H elimination step. Analysis of the Eyring plot established activation parameters for the beta-H elimination reaction as Delta H-double dagger = 15(1) kcal/mol and Delta S-double dagger = -41(3) eu. AAD reactions using a series of Ru(b4Rpi)(PPh3)(2)Cl complexes indicated that the ortho-substituted methyl groups of bMepi slightly impede catalytic activity, and electronic modifications of the pincer scaffold have a minimal effect on the reaction rate.
机译：使用单个预催化剂HRu（bMepi）（PPh3）（2）（bMepi = 1,3-双（6'-甲基-2'-吡啶基limino）异吲哚酸酯）可有效实现酮和醇之间通过顺序加氢脱氢反应的可逆转化。通过一系列动力学和同位素标记研究，中间体的分离以及Ru（b4Rpi）（PPh3）的评估，研究了HRu（bMepi）（PPh3）（2）介导的无受体醇脱氢（AAD）的催化机理。 （2）Cl（R = H，Me，Cl，OMe，OH）配合物研究了两种限制的脱氢方案：内球β-H消除和外球双功能双氢转移。同位素标记实验表明，质子和氢化物以逐步方式转移。催化剂改性表明，bMepi钳式支架上的亚胺基对于催化醇脱氢不是必需的。动力学实验和催化剂改性的评估表明HRu（bMepi）（PPh3）（2）通过内球β-H消除机理起作用。单个PPh3解离后，醇底物可以结合并进行质子转移，然后进行限制周转的β-H消除步骤。 Eyring图的分析建立了β-H消除反应的活化参数，即Delta H-双匕首= 15（1）kcal / mol和Delta S-双匕首= -41（3）eu。使用一系列Ru（b4Rpi）（PPh3）（2）Cl络合物的AAD反应表明，bMepi的邻位取代甲基略微阻碍了催化活性，而钳形支架的电子修饰对反应速率的影响最小。

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