A Pyridine‐Stabilized<i>N</i>‐Phosphinoamidinato<i>N</i>‐Heterocyclic Carbene‐Diboravinyl Cation: Boron Analogue of Vinyl Cation
Jun Fan, Pei‐Ting Chia, Zhengfeng Zhang, Ming‐Chung Yang, Ming‐Der Su, Cheuk‐Wai So
Abstract
Abstract A boron analogue of vinyl cation, pyridine‐stabilized N ‐phosphinoamidinato N ‐heterocyclic carbene (NHC)‐diboravinyl cation 2 + , was synthesized by displacement of bromide in diborene 1 with excess pyridine. Experimental and computational studies showed that the positive charge is mainly at the B−B skeleton with delocalization to the pyridine ligand. One of the main modes of reactivity is through the B=B double bond alongside activation of the pyridine substituent, where the B pyridine center is the predominant nucleophilic center and the predominant electrophilic center is either the activated pyridine para position or the B NHC center, illustrating the presence of diborene cation A , borylene‐borenium cation B and diborene‐pyridinium cation C resonance structures in cation 2 + .