A New Class of Singlet Carbene Ligands



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What are you? Deprotonation of fluorenylidene phosphonium salts generates reactive intermediates that can be described as push–pull cumulenes or singlet carbenes (see scheme). Whereas the NMR data are ambiguous, the coordination behavior shows the ready availability of a lone pair at the central C atom. The donor ability of singlet carbene ligands of this new class exceeds that of the commonly used N-heterocyclic carbenes (NHCs).