Frustrated Lewis Pair (FLP) Reactivity from Carbone–BPh₃ Lewis Adduct

We present a systematic investigation of the Frustrated Lewis Pair (FLP) chemistry of carbodicarbenes (fCDCs) featuring varied steric profiles in combination with strong (B(C₆F₅)₃, BCF) and weak (BPh₃) boron Lewis acids. The resulting CDC–borane systems display a full spectrum of behaviors: (i) tightly bound Lewis adducts lacking FLP reactivity, (ii) adducts exhibiting reversible dissociation and activate small molecules via FLP-type reactivity, and (iii) a “classical” FLP that remain unbound. The most reactive Lewis adduct, 1·BPh₃, which exhibits the lowest dissociation energy, activates a broad range of bonds (C─H, O─H, N─H, H─B, H─Si, S─S, and CO₂) and catalyzes hydroboration and hydrosilylation of ketones under mild, metal-free conditions. NMR exchange spectroscopy and DFT calculations reveal that its FLP reactivity originates from reversible dissociation and the formation of a reactive transient encounter complex. These findings establish carbone-based Lewis adducts as tunable platforms for FLP-type small molecule activation and main-group catalysis, where reactivity can be regulated through steric and electronic modulation.