Compounds with Low-Valent p-Block Elements for Small Molecule Activation and Catalysis

The past decade has witnessed staggering progress in the chemistry of compounds with low-valent main-group elements. Although these discoveries are mostly fundamental by nature, these compounds show promising reactivity towards small molecule activation. The reactivity of these compounds stems from the modest HOMO-LUMO energy gap; a characteristic known for the transition metals. The journey began in 2005 with the facile activation of dihydrogen by an alkyne analog of germanium [ArGeGeAr; Ar=2,6-Trip(2)-C6H3 (Trip=2,4,6-iPr(3)-C6H2)]. Subsequently, tremendous progress has been achieved in understanding and elucidating the potential of these compounds to activate small molecules as well as to use them in a variety of stoichiometric and catalytic transformations. In this review, we focus on developments in the activation of H-2, NH3, CO, and CO2 by compounds with multiply bound or open shell main-group elements. Emphasis will be given to their catalytic activity.