Nickel-Catalyzed Deuteration of Primary, Secondary, and Tertiary Silanes: Scope and Mechanistic Insights

Abstract

Deuterated silanes are crucial reagents for deuteration, with a diverse range of applications in materials science, pharmaceuticals, and isotopic labeling. While most methods for synthesizing deuterated silanes rely on stoichiometric environmentally harmful processes or noble metal catalysts, research into more sustainable alternatives has received relatively less attention. In this study, we introduce a catalyst based on a nickel PBP-pincer system (PBP = bis(phosphino)boryl), which effectively facilitates catalytic hydrogen/deuterium exchange for primary, secondary, and tertiary silanes, as well as tertiary siloxanes and certain boranes, utilizing a catalyst loading of 2 mol % at 25 °C. DFT calculations identify two reaction pathways that require overcoming similar energy barriers for the H/D exchange step: silane activation assisted by the PBP ligand (ΔG^⧧ = 24.1 kcal mol^–1) and H/D exchange promoted by nucleophilic Ni-hydride (ΔG^⧧ = 22.4 kcal mol^–1). These results suggest that both pathways are feasible, with a slight energetic preference for the latter. We also present detailed mechanistic studies, including control experiments, an analysis of catalyst deactivation pathways, and kinetic studies that are in excellent agreement with the outcome of the theoretical calculations.