Modulating dehydrogenative coupling of hydride-terminated silicanes: a systematic study of Lewis base catalysis

Controlled formation of silicon-silicon (Si-Si) bonds is essential for advancing silicon-based materials, but existing synthetic methods often require harsh conditions or metal catalysts. In a previous work, we accidentally found that Si-Si bond formation can be achieved via dehydrogenative coupling on hydride-terminated silicane (HSi), without the aforementioned harshness, in the presence of dimethyl sulfoxide (DMSO), a Lewis base (LB). Despite this serendipity, the general knowledge of how the structural and electronic properties of LBs affect the reaction efficiency remains unknown. Here, we address this gap by systematically investigating a broad range of LBs for this catalysis. Kinetic analysis reveals pronounced, structure-dependent variation in catalytic activity, modulated by the interplay of basicity, steric accessibility, and electronic stabilization of the intermediate. By integrating experimental kinetics with density functional theory (DFT) calculations, we identify the Si⁺(SiH₃)₃ affinity as a unified descriptor that quantifies the nucleophilic engagement of LBs in catalyzing Si-Si formation. This parameter correlates strongly with both calculated activation barriers and experimental performance across oxygen-, nitrogen-, and sulfur-based LBs, suggesting its potential utility as a guiding descriptor for catalyst design.