Dinitroxide Carbenes, A New Class of Carbenes with Autoumpolung Character: Preparation in Solution and Stabilization in Transition Metal Complexes We thank Prof. P. Audebert, ENS Cachan (Paris), for undertaking the cyclic voltammetric measurements and Dr. F. Hampel, Universität Erlangen-Nürnberg, for performing the crystal-structure analysis.

By deprotonation of the nitronylnitrosonium cation 1 the dinitroxide carbene 2 was prepared in solution (see scheme, S=singlet, T=triplet). Carbene 2 is the first example of a new class of carbenes with autoumpolung capability, the electronic structure of which is discussed in terms of configurations 2 a–c. Stable transition metal complexes derived from 2 a were synthesized and structurally characterized.