Ariai, JamaJamaAriaiZiegler, MayaMayaZieglerWürtele, ChristianChristianWürteleGellrich, UrsUrsGellrich2024-11-222024-11-222024https://jlupub.ub.uni-giessen.de/handle/jlupub/19897https://doi.org/10.22029/jlupub-19252We report the preparation of a new organic σ-donor with a C6H4-linker between an N-heterocyclic carbene (NHC) and an exocyclic methylidene group, which we term N-heterocyclic quinodimethane (NHQ). The aromatization of the C6H4-linker provides a decisive driving force for the reaction of the NHQ with an electrophile and renders the NHQ significantly more basic than analogous NHCs or N-heterocyclic olefins (NHOs), as shown by DFT computations and competition experiments. In solution, the NHQ undergoes an unprecedented dehydrogenative head-to-head dimerization by C−C coupling of the methylidene groups. DFT computations indicate that this reaction proceeds via an open-shell singlet pathway revealing the diradical character of the NHQ. The product of this dimerization can be described as conjugated N-heterocyclic bis-quinodimethane, which according to cyclic voltammetry is a strong organic reducing agent (E1/2=−1.71 V vs. Fc/Fc+) and exhibits a remarkable small singlet–triplet gap of ΔES→T=4.4 kcal mol−1.enNamensnennung - Nicht kommerziell 4.0 Internationalddc:540