Fluorenone and Fluorene Complexes with a Slipped Triple Decker Structure DisplayingVariable Hapticity of ((Pentaalkyl)cyclopentadienyl)cobalt(I) Fragments

The reaction of the toluene triple decker complexes [{(η 5 ‐Me 5 C 5 )Co} 2 μ‐(η 6 :η 6 ‐toluene)] and [{(η 5 ‐EtMe 4 C 5 )Co} 2 μ‐(η 6 :η 6 ‐toluene)] with fluorenone leads to the first triple decker compounds [{(η 5 ‐Me 5 C 5 )Co} 2 μ‐(η 5 :η 4 ‐fluorenone)] ( 1 ) and [{(η 5 ‐EtMe 4 C 5 )Co} 2 μ‐(η 5 :η 4 ‐fluorenone)] ( 2 ) of this ligand. In 1 and 2 two [(η 5 ‐RMe 4 C 5 )Co] fragments are bridged by a fluorenone ligand. One Co atom in 1 and 2 is coordinated by the five‐membered ring of the fluorenone ligand in a η 5 ‐fashion, whereas the other Co atom is coordinated by the six‐membered ring in a η 4 ‐fashion. The reaction of [{(η 5 ‐Me 5 C 5 )Co} 2 μ‐(η 6 :η 6 ‐toluene)] with 9 H ‐fluorene results in the formation of the first slipped triple decker [{(η 5 ‐Me 5 C 5 )Co} 2 μ‐(η 5 :η 3 ‐1 H ‐fluorene)] ( 3 ) of this ligand. One {(η 5 ‐Me 5 C 5 )Co} fragment is bonded to the fluorene ligand via one of the six‐membered rings in a η 3 ‐fashion, whereas the other {(η 5 ‐Me 5 C 5 )Co} fragment is coordinated by the five‐membered ring of the fluorene ligand in a η 5 manner. In 3 the coordination of the {(η 5 ‐Me 5 C 5 )Co} fragments leads to tautomerism of the fluorene ligand, one H atom has been moved from C9 to C1, consequently 9 H ‐fluorene has been tautomerised to 1 H ‐fluorene.