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 Krishnan Damodaran Xiben Li Xiangcheng Pan Dennis P. Curran 10.1021/acs.joc.5b00324.s001 https://acs.figshare.com/articles/journal_contribution/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/2170642 Dynamic NMR spectroscopy has been used to measure rotation barriers in five <i>B</i>,<i>B</i>-disubstituted 1,3-dimethylimidazol-2-ylidene boranes. The barriers are attributed to the sp<sup>2</sup>–sp<sup>3</sup> 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<sup>–1</sup>. 2-Isopropyl-1,3,5-trimethylbenzene is used as a comparable to help understand the nature and magnitude of the barriers. 2015-05-01 00:00:00 group show boron atom measure rotation barriers boron atoms Dynamic Behavior Bond Substantial Rotation BarriersDynamic NMR spectroscopy Borane