Investigation on reactivity of non-classical carbenes with sterically hindered Lewis acid, B(C6F5)3 under inert and open conditions

Abstract

Reactions of B(C6F5)3 with abnormal N-heterocyclic carbene (aNHC), L1 and cyclic (alkyl)(amino) carbene (cAAC), L2 in the presence of moisture as well as in its absence, have been investigated in toluene. Reaction of aNHC with 1 equivalent of B(C6F5)3 under inert condition produced classical Lewis acid-base adduct, [L1.B(C6F5)3], 1. Further, probing the same reaction with cyclic (alkyl)(amino) carbene (cAAC), having different electronic property, led to the isolation of [L2.B(C6F5)3], 2 under inert condition. Interestingly, reaction of aNHC or cAAC with 1 equivalent of B(C6F5)3 in the presence of moisture resulted in water splitting leading to the formation of [L1-H][(OH)B(C6F5)3], 3 and [L2-H][(OH)B(C6F5)3, 4. All these compounds (1-4) were characterized in solution by 1H, 13C, 19F and 11B NMR spectroscopy. Additionally, the solid-state structures were unambiguously established by crystallographic analysis of compounds 1-4. Reactions of B(C6F5)3 with abnormal N-heterocyclic carbene or cyclic (alkyl)(amino) carbene in absence and in presence of moisture in toluene led to the formation of B(C6F5)3-carbene 1:1 adducts and water splitting products, respectively.