Facial coordination of cyclooctatetraene to a Co2Ni triangle in a heterometallic trinuclear cluster complex

Reaction of [(η-C5H5)NiCo3(CO)9] (5) with 1,3,5,7-cyclooctatetraene or 1,4-(SiMe3)2C8H6, respectively, yields the complexes [Co2Ni(CO)6(μ3-η8-C8H6R2)] (R=H, SiMe3) (7a, b). Dramatic modifications of the tetrametallic cluster core and the ligand sphere of 5 to give the trinuclear complex 7 are driven by the preference of the cyclopolyenes for facial (μ3-η8) coordination. The title complexes are the first examples of facial cyclooctatetraene coordination to a heterometallic (Co2Ni) triangle.