Transition metal methylene complexes, VII. Studies on metal–metal bonds, V. Preparation and molecular structure of a carbonylcobalt complex containing a novel carbocyclic μ‐methylene ligand

Dicarbonyl(η⁵‐cyclopentadienyl)cobalt (1) reacts with 2‐diazo‐1,3‐dioxoindane (2) under thermal conditions (boiling benzene) to yield the dinuclear cobalt complex 3 which contains the carbene derived from 2 as a bridging ligand. An x‐ray diffraction study proved that both the cyclopenta‐dienyl rings are oriented trans to each other, which is also true for the two metal–carbonyl groups. While four‐bonded, the methylene carbon is highly distorted from tetrahedral geometry [∢Co(1)C(3)Co(2): 79.0(1)°, ∢C(4)C(3)C(11): 104.3(3)°]. The cobalt — cobalt distance is 247.5(1) pm and the CoC(C₅H₅) and CoC(CO) distances and angles are normal. The μ‐1,3‐dioxoindane‐2‐ylidene backbone is bent by 2° along the vector joining the two carbonyl carbon atoms of the dione system.