Stepwise B–H bond activation of a meta-carborane

Abstract

Stepwise multiple B–H bond activation is a major challenge in synthetic chemistry. Herein, we have developed a controlled stepwise method to monitor the process of B–H bond activation based on a meta-carborane. In this process, the metallacyclic 3 [Pd₂(C₁₀N₂H₈)₂(SCNPh)₄(m-C₂B₁₀H₁₀)₂] can be achieved through non-covalent bond interactions between the carboranylthioamide ligand and transition metal fragment. Importantly, it slowly converts to product 4 [Pd(C₁₀N₂H₈)(SCNPh)(SCNHPh)(m-C₂B₁₀H₉)] via mono B–H bond activation, and then a second B–H activation leads to 5 [Pd₂(C₁₀N₂H₈)₂(SCNPh)₂(m-C₂B₁₀H₈)]. The obtained organometallic palladium pincer complex shows acid–base responsive behaviour, namely reversible structural transformation between the mononuclear pincer complex and a trimetallic Pd/S metallacycle. This work provides a potential strategy for exploring the mechanisms of B–H bond activation.