The Discovery of [Ni(NHC)RCN]<sub>2</sub> Species and Their Role as Cycloaddition Catalysts for the Formation of Pyridines
作者:Ryan M. Stolley、Hung A. Duong、David R. Thomas、Janis Louie
DOI:10.1021/ja3075924
日期:2012.9.12
added IPr, zeroth order in nitrile, and zeroth order in diyne. Extensive stoichiometric competition studies were performed, and selective incorporation of the exogenous, not dimer bound, nitrile was observed. Post cycloaddition, the dimeric state was found to be largely preserved. Nitrile and ligand exchange experiments were performed and found to be inoperative in the catalytic cycle. These observations
Ni(COD)(2)、IPr 和腈的反应以高产率提供二聚体 [Ni(IPr)RCN](2)。X 射线分析显示这些物质同时显示 η(1)- 和 η(2)- 腈结合模式。这些二聚体能够催化二炔和腈的环加成形成吡啶。动力学分析表明该反应在[Ni(IPr)RCN](2) 中为一级反应,在添加的IPr 中为零级反应,在腈中为零级反应,在二炔中为零级反应。进行了广泛的化学计量竞争研究,并观察到外源性、非二聚体结合的腈的选择性掺入。环加成后,发现二聚体状态大部分得到保留。进行了腈和配体交换实验,发现在催化循环中不起作用。这些观察结果表明催化剂通过部分二聚体打开、随后与外源腈结合以及随后的氧化杂偶联而被激活。