The reactivity of complexed carbocycles : XII. Neutral dimetallic complexes with bridging cyclooctatetraene. X-ray structure of μ-[1–4:5–8η-cyclooctatetraene]cyclopentadienylcobalt-tricarbonylmolybdenum (CoMo)

The reaction of CpCoC₈H₈ with (diglyme)Mo(CO)₃, (CH₃CN)₃Cr(CO)₃ and (DMF)₃W(CO)₃ yields dimetallic complexes CpCoC₈H₈M(CO)₃ which contain bridging fluctional cyclooctatetraene. The electron deficiency of the Mo(CO)₃ groups relative to CpCo is believed to be balanced by a π-donor metal—metal bond. This is indicated by an unusually low absorption band in the IR spectrum, and by the X-ray structure of the CoMo dimer, which shows a shortened MoCO bond trans to the metal—metal bond. A further product is the nonfluctional dimer CpCoC₈H₈Mo(CO)₄, in which cyclooctatetraene retains a rigid “tub” conformation. Reaction of C₈H₈Fe(CO)₃ with (diglyme)Mo(CO)₃ also yields a dimeric product (CO)₃FeC₈H₈Mo(CO)₃ with a fluctional bridge ligand.