Oxidation-induced coupling reactions of bi(metallacycloprop-1-ene) complexes.

The feasibility of coupling of two carbene ligands of biscarbene complexes L n M(CR 2 ) 2 to form alkene complexes L n M(η 2 -R 2 CCR 2 ) was predicted theoretically as early as 1982. However, until now, there appear still no reports on carbene coupling reactions of well-defined biscarbene complexes. This work reports oxidation-induced coupling reactions of bi(metallacycloprop-1-ene) complexes to give η 4 -butadiene complexes, a unique example of coupling of two carbene ligands of biscarbene complexes.