Isolated carbon(I) species featuring a carbone cation radical

Carbynes, characterized by their radical and carbene attributes, possess three non-bonding electrons and have garnered substantial scientific interest. The high reactivity and complex hybridization of valence orbitals in carbynes have impeded the isolation of free carbon(I) species. Carbodicarbenes are divalent carbon(0) species with two electron lone pairs, which are in principle capable of losing an electron to generate a radical cation carbon(I) species containing three non-bonded electrons, similar to the frontier orbital of a carbyne without a vacant orbital. Here we describe the isolation of a crystalline cation radical carbon(I), [1-CDC]^•+, prepared by a single-electron transfer between a carbodicarbene and a nitroaromatic compound to generate a stable radical ionic pair. Electron paramagnetic resonance and X-ray crystallography with quantum chemical analysis show that the unpaired electron of [1-CDC]^•+ resides in the p(π) atomic orbital of the secondary carbon with some delocalization to the N-heterocyclic carbene ligands. Exploring the reactivity of this carbon(I) radical cation revealed its capacity to mediate a variety of C–O and C–C cross-coupling reactions with electron-deficient aryl halides. These findings not only expand the understanding of carbon(I) radical chemistry but also potentially open new avenues for radical methodologies in organic synthesis and catalysis. (Figure presented.)