Germanium-Mediated Catalysis via Ge(II)/Ge(III)/Ge(IV) or Ge(II)/Ge(IV) Redox Cycling

Main group elements have recently emerged as promising candidates for redox catalysis, challenging the traditional reliance on transition metals. Despite heavy group 14 elements, such as germanium, possessing variable oxidation states that suggest their redox catalytic potential, their practical applications have been limited. In this study, we present the synthesis of a carbodiphosphoranyl germanium(II) compound and investigate its redox catalytic application. This organogermanium(II) species exhibits excellent catalytic performance in promoting the transfer hydrogenation of azoarenes and imines under mild conditions. Mechanistic studies revealed two distinct catalytic platforms based on Ge^II/Ge^III/Ge^IV and Ge^II/Ge^IV redox cycles at a single germanium center. These results enable us to achieve the catalytic hydrogenation of azoarenes mediated by frustrated radical pairs (FRPs), as well as the catalytic chemoselective dearomatization of N-heteroarenes undergoing a Ge^II/Ge^IV redox process. Our work demonstrates the capacity of main group catalysts to facilitate diverse challenging chemical transformations through regulating the catalytic modes.