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

Abstract

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 9H-fluorene results in the formation of the first slipped triple decker [{(η 5 -Me 5 C 5 )Co} 2 µ-(η 5 :η 3 -1H-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 9H-fluorene has been tautomerised to 1H-fluorene.

A Cobaltocenium Complex of Dibenzo[c,g]fluorenide and Its Structural and Electrochemical Properties

“…η 5 -Coordination of Flu − to a cobalt center was finally confirmed in 1992 by the publication of the solid-state structure of (η 5 -Flu)(η 5 -carborane)cobaltocene . Recent examples of fully characterized cobalt triple-decker complexes containing η 5 -Flu − ligands were reported by Schneider et al in 2007 . Mutseneck et al were able to transfer the fluorenide anion onto a (tetramethylcyclobutadienyl)cobalt(I) fragment, although the product turned out to be too sensitive to yield satisfactory analytical data .…”

“…10 Recent examples of fully characterized cobalt tripledecker complexes containing η 5 -Fluligands were reported by Schneider et al in 2007. 11 Mutseneck et al were able to transfer the fluorenide anion onto a (tetramethylcyclobutadienyl)cobalt(I) fragment, although the product turned out to be too sensitive to yield satisfactory analytical data. 12 To the best of our knowledge, no cobaltocene of an isomer or higher benzannulated homologue of Fluhas been described up to now.…”

Indenyl Ligands as Supports for Reactive, Low-Valent Cobalt(I) Fragments

“…Our efforts have centered on the preparation of reactive, low-electron-count Co(I) fragments for small-molecule activation using substituted fluorenyl or indenyl ancillary ligands. Our initial inspiration was driven by the potential formation of 18-electron complexes, stabilized by an intramolecular L 2 interaction with the benzo fragment of the ligand. , We envisioned benzo dissociation, due to ring strain, which could allow access to a reactive, 14-electron Co(I) intermediate. Herein we report our initial efforts toward this goal.…”

Synthesis and structure of mono- and dinuclear cyclopentadienyl–indenyl complexes of iron(II) and further reactions to mixed tri- and tetranuclear iron–cobalt complexes

“…They are accessible in a reductive ligand degradation from [(g 5 -Me 5 C 5 )Co(O,O 0 -acac)] [17] by potassium metal in various arenes [18]. It is possible to substitute the arene middle deck under mild conditions by various other arenes [18][19][20]. Therefore, it should also be possible to use arene-metal complexes with non-coordinated ring systems as ligands to substitute the toluene molecule and thereby to prepare compounds of higher nuclearity and mixed metal complexes.…”