Saturated NHC-Stabilized Borenium, Boronium, Hydride-Bridged Boron Cations, and a Bora-Acyl Chloride
Gargi Kundu, P. R. Amrutha, Srinu Tothadi, Sakya S. Sen
Abstract
This study investigates the reactivity of 5-SIDipp-boranes and haloboranes (5-SIDipp = 1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene) with Lewis acids (AlCl 3 and GaCl 3 ). The reaction between 5-SIDipp·BH 3 and GaCl 3 resulted in the formation of 3c-2e hydride-bridged boron cations ( 1 ). Treatment of AlCl 3 to the mixture of 5-SIDipp and BHCl 2 ·SMe 2 produced a tetra-coordinate boronium cation of the composition 5-SIDipp → [B(H)Cl] + ← SMe 2 ( 2 ). The SMe 2 moiety remains coordinated to the boron center throughout the reaction, playing a crucial role in the isolation of compound 2 . The interaction of 5-SIDipp·BCl 3 with AlCl 3 led to the formation of a tri-coordinate borenium cation ( 4 ). However, the formation of 4 was always accompanied by the generation of a bora-acyl chloride (B(═O)Cl) derivative ( 5 ).