Cooperative Bond Activation and Catalysis by Tetrylene-Stabilized Low-Valent Main-Group Compounds

ConspectusThe study of main-group molecules that mimic transition metal (TM) complexes in bond activation and catalysis has attracted considerable interest in recent decades. However, main-group elements lack the same electronic versatility that endows TM complexes with diverse reactivity patterns. This limitation has driven efforts to develop innovative strategies to harness and expand the reactivity of main-group compounds. Among these, leveraging cooperative effects between main-group centers has emerged as a particularly promising approach to fine-tune their reactivity, as exemplified by frustrated Lewis pairs (FLPs) and bimetallic main-group complexes. Despite these advances, examples of cooperative interactions involving multiple low-valent main-group element centers remain rare. Such cooperativity is of great interest because the presence of multiple low-valent centers facilitates enhanced multielectron transfer capabilities. Consequently, advancing the design and synthesis of multinuclear low-valent main-group compounds holds great promise for unlocking new reactivity in main-group chemistry.This Account details our studies of the synthesis of heavier tetrylene-stabilized low-valent main-group compounds and their applications in cooperative bond activation and catalysis. We describe the design of new types of multidentate silylene ligands and demonstrate their effectiveness in stabilizing boron(I) and aluminum(I) compounds, referred to as borylene and aluminylene, respectively. The cooperation between B(I)/Si(II) and Al(I)/Si(II) centers enables the cleavage of various bonds, including the N-H bond in aniline, the C=O bond in ketones and carbon dioxide, the N=O bond in nitrosoarenes, and the C≡O bond in carbon monoxide. These compounds serve as effective precatalysts for carbon dioxide reduction and the reductive coupling of nitrosoarenes to azoxyarenes, respectively. Using a bis(germylenyl)carborane ligand, we have isolated zerovalent group 14 compounds, such as stannylone and plumbylone. The cooperation between Sn(0)/Ge(II) and Pb(0)/Ge(II) centers enables multiple electron transfers to cleave the N=O bonds of nitrous oxide and nitro compounds. The stannylone acts as an efficient precatalyst for the deoxygenation of nitrous oxide and nitro compounds, leading to the formation of dinitrogen and hydrazines, respectively. These results provide a unique proof-of-concept, underscoring their potential as versatile platforms for challenging bond activation and catalysis.