page_title: Transition metal indenyl complex
section_title: Preparation and structure
hierarchical_section_title: Transition metal indenyl complex / Preparation and structure
caption_attribution_description: English: Metallocenes for olefin polymerization catalysts
context_page_description: In organometallic chemistry, a transition metal indenyl complex is a coordination compound that contains one or more indenyl ligands. The indenyl ligand is formally the anion derived from deprotonation of indene. The η⁵-indenyl ligand is related to the η⁵cyclopentadienyl anion, thus indenyl analogues of many cyclopentadienyl complexes are known. Indenyl ligands lack the 5-fold symmetry of Cp, so they exhibit more complicated geometries. Furthermore, some indenyl complexes also exist with only η³-bonding mode. The η⁵- and η³-bonding modes sometimes interconvert.
context_section_description: Indene is deprotonated by butyl lithium and related reagents to give the equivalent of the indenyl anion:
  C₉H₈  +  BuLi  →  LiC₉H₇  +  BuH
  The resulting lithium indenide can be used to prepare indenyl complexes by salt metathesis reactions of metal halides.  When the metal halide is easily reduced, the trimethylstannylindenyl can be used as a source of indenyl anion:
  Me₃SnC₉H₇  +  TiCl₄   →   Me₃SnCl  +  C₉H₇TiCl₃
  The M-C distances in indenyl complexes are comparable to those in cyclopentadienyl complexes.  For the metallocenes M(Ind)₂, ring slipping is evident for the case of M = Co and especially Ni, but not for M = Fe.  A number of chelating or ansa-bis(indenyl complexes are known, such as those derived from 2,2'-bis(2-indenyl) biphenyl
caption: Metallocene dichloride 1, containing two Cp ligands (C2v symmetry), a related complex bis(indenyl) complex 2 (C2 symmetry), and a mixed Cp-fluorenyl complex 3 (Cs symmetry).  Such compounds are precursors to Ziegler–Natta catalysts.
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