Aluminum versus Gallium: Differences in Bis(bis(trimethylsilyl)methyl) Element Halides, Hydrides, and Oxygen‐Bridged E/P Frustrated Lewis Pairs

Extremely sterically demanding bis(bis(trimethylsilyl)methyl)‐substituted aluminum and gallium compounds are particularly suitable for applications in frustrated Lewis pair (FLP) chemistry. A selective exchange reaction between Bis 2 GaBr (Bis = CH(SiMe 3 ) 2 ) and Bis 2 AlH affords the previously inaccessible Bis 2 GaH, a monomeric gallium hydride, in solution, as confirmed by diffusion ordered spectroscopy NMR, IR spectroscopy, quantum chemical calculations, and—indirectly—by hydrogallation of phenylacetylene. A simple one‐pot route enables access to Bis 2 EOP t Bu 2 FLPs (E = Al, Ga) via formal HBr adducts and subsequent deprotonation with KHMDS. As predicted for Bis 2 GaOP t Bu 2 , H 2 activation is favored, although it proceeds slowly and irreversibly. Surprisingly, variable‐temperature NMR studies unveil a dynamic equilibrium between the H 2 adduct Bis 2 Ga(H)OP(H) t Bu 2 and the free gallium hydride and phosphine oxide, shedding new light on reversible hydrogen activation in main‐group FLP systems.