A cyclic (alkyl)(boryl)germylene derived from a cyclic (alkyl)(amino)germylene

A cyclic (alkyl)(amino)germylene undergoes a ring expansion reaction with dibromomesitylborane (MesBBr${}_2$) to afford a six-membered dibromogermane derivative. In the presence of Lewis bases (PMe${}_3$ or ${}^{Me}$NHC), reduction of the latter with two equivalents of potassium graphite (KC${}_8$) gives rise to cyclic (alkyl)(boryl)germylene–Lewis base adducts. Upon heating, the germylene-PMe${}_3$ adduct reacts with H${}_2$ to yield a germane, probably via a base-free germylene featuring a small HOMO–LUMO gap. (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)