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Mononuclear biscarbene complexes by direct nucleophile addition to a CO ligand of Fischer arylcarbene complexes.

Mononuclear Group 6 Fischer biscarbene complexes I, which are organometallic compounds that have two carbene ligands bonded to the same transition-metal atom, have been much less investigated than the corresponding Fischer monocarbene complexes II (Figure 1). Only very few examples of this class of compounds I have been reported and characterized by reactivity and/or X-ray studies, and their synthetic potential remains to be explored. In addition, there is a lack of a general method to produce such complexes.