Dynamic Behavior of N-Heterocyclic Carbene Boranes: Boron–Carbene Bonds in <i>B</i>,<i>B</i>-Disubstituted <i>N</i>,<i>N</i>-Dimethylimidazol-2-ylidene Boranes Have Substantial Rotation Barriers
作者:Krishnan Damodaran、Xiben Li、Xiangcheng Pan、Dennis P. Curran
DOI:10.1021/acs.joc.5b00324
日期:2015.5.1
Dynamic NMR spectroscopy has been used to measure rotation barriers hi five B,B-disubstituted 1,3-dimethylimidaol-2-ylidene boranes. The barriers are attributed to the sp(2)-sp(3) bond between C(1) of the N-heterocyclic carbene ring and the boron atom: Bonds to boron atoms bearing a thexyl (1,1,2-trimethylpropyl) group Show especially high barriers, ranging from 75-86 kJ mol(-1). 2-Isopropyl-1,3,5-trimethylbenzene is used as a comparable to help understand the nature and magnitude of the barriers.