β-Hydride Elimination and C–H Activation by an Iridium Acetate Complex, Catalyzed by Lewis Acids. Alkane Dehydrogenation Cocatalyzed by Lewis Acids and [2,6-Bis(4,4-dimethyloxazolinyl)-3,5-dimethylphenyl]iridium,Journal of the American Chemical Society

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β-Hydride Elimination and C–H Activation by an Iridium Acetate Complex, Catalyzed by Lewis Acids. Alkane Dehydrogenation Cocatalyzed by Lewis Acids and [2,6-Bis(4,4-dimethyloxazolinyl)-3,5-dimethylphenyl]iridium
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2017-04-18 00:00:00 , DOI: 10.1021/jacs.6b12995
Yang Gao ₁ , Changjian Guan ₁ , Meng Zhou _{1,

2} , Akshai Kumar _{1,

3} , Thomas J. Emge ₁ , Ashley M. Wright ₄ , Karen I. Goldberg ₄ , Karsten Krogh-Jespersen ₁ , Alan S. Goldman ₁

Affiliation

NaBAr^F₄ (sodium tetrakis[(3,5-trifluoromethyl)phenyl]borate) was found to catalyze reactions of (Phebox)Ir^III(acetate) (Phebox = 2,6-bis(4,4-dimethyloxazolinyl)-3,5-dimethylphenyl) complexes, including (i) β-H elimination of (Phebox)Ir(OAc)(n-alkyl) to give (Phebox)Ir(OAc)(H) and the microscopic reverse, alkene insertion into the Ir–H bond of (Phebox)Ir(OAc)(H), and (ii) hydrogenolysis of the Ir–alkyl bond of (Phebox)Ir(OAc)(n-alkyl) and the microscopic reverse, C–H activation by (Phebox)Ir(OAc)(H), as indicated by H/D exchange experiments. For example, β-H elimination of (Phebox)Ir(OAc)(n-octyl) (2-Oc) proceeded on a time scale of minutes at −15 °C in the presence of (0.4 mM) NaBAr^F₄ as compared with a very slow reaction at 125 °C in the absence of NaBAr^F₄. In addition to NaBAr^F₄, other Lewis acids are also effective. Density functional theory calculations capture the effect of the Na⁺ cation and indicate that it operates primarily by promoting κ²–κ¹ dechelation of the acetate anion, which opens the coordination site needed to allow the observed reaction to proceed. In accord with the effect on these individual stoichiometric reactions, NaBAr^F₄ was also found to cocatalyze, with (Phebox)Ir(OAc)(H), the acceptorless dehydrogenation of n-dodecane.

中文翻译：

路易斯酸催化的乙酸铱络合物消除β-氢化物和CH-H活化。路易斯酸和[2,6-双（4,4-二甲基恶唑啉基）-3,5-二甲基苯基]铱共同催化的烷烃脱氢

发现NaBAr ^F₄（四[（3,5-三氟甲基）苯基]硼酸钠）催化（Phebox）Ir ^III（乙酸）（Phebox = 2,6-双（4,4-二甲基恶唑啉基）-3， 5-二甲基苯基）络合物，包括（i）通过β-H消除（Phebox）Ir（OAc）（n-烷基），得到（Phebox）Ir（OAc）（H）和微观的反向链，烯烃插入Ir– （Phebox）Ir（OAc）（H）的H键，以及（ii）（Phebox）Ir（OAc）（n-烷基）的Ir-烷基键的氢解和微观逆向的（Phebox）激活C–H如H / D交换实验所示，Ir（OAc）（H）。例如，β-H消除（Phebox）Ir（OAc）（n-辛基）（2-Oc）进行的分钟的时间尺度在-15℃下在（0.4毫摩尔）NaBAr存在^˚F₄为具有在125℃下在不存在NaBAr一个非常缓慢的反应相比^˚F₄。除了NaBAr ^F_4以外，其他路易斯酸也是有效的。密度泛函理论计算捕获的Na的效果⁺阳离子和指示它通过促进κ主要操作² -κ ¹乙酸盐阴离子，其打开以允许观察到的反应进行所需的配位点的dechelation。根据对这些单独的化学计量反应的影响，NaBAr ^F₄还发现它与（Phebox）Ir（OAc）（H）共同催化正十二烷的无受体脱氢。

更新日期：2017-05-03

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