Influence of <i>N</i>-Heterocyclic Carbene Steric Bulk on Selectivity in Nickel Catalyzed C–H Bond Silylation, Germylation, and Stannylation
作者:Matthew R. Elsby、Junyang Liu、Sha Zhu、Lingfei Hu、Genping Huang、Samuel A. Johnson
DOI:10.1021/acs.organomet.8b00786
日期:2019.1.28
smallest IBn and iPr2Im NHC ligands. Using the larger IMes carbene resulted in a 66:34 mixture of silylation and hydroarylation products, and the largest NHC, IPr, gave exclusive conversion to the hydroarylation product, C6F5CH2CH2SiMe3. DFT calculations are provided that give insight into the mechanism and key reaction steps, such as the relative difficulty of the critical β-Sn, Ge, and Si elimination
一系列Ni(0)化合物由电子相似的N-杂环卡宾(NHC)辅助配体(含5%V bur的范围)支撑,用作芳基C–H键甲硅烷基化,杀菌和锡烷基化的催化剂。尽管催化剂的静止状态几乎没有结构变化,但NHC的空间体积极大地影响了C–H官能化的选择性,从而产生了新的碳-杂原子键与烯烃加氢芳基化反应。研究由下反应进行6 ˚F 5 H和H 2 C═CHER 3(ER 3 = SnBu 3,GePh 3,森达3),使用催化量的Ni(COD)的2NHC配体IPr,IMes,IBn和i Pr 2 Im。催化的C–H锡烷基化反应可得到C 6 F 5 SnBu 3,而且所有配体都很容易。催化C-H germylation反应比甲锡烷基化更加困难,但使用H证明2 C═CHGePh 3得到C,6 ˚F 5 GePh 3为所有,但最大的NHC。最大的NHC IPr给出了96:4的氢芳基化产物C 6 F 5 CH 2 CH 2