Transition metal indenyl complex

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 (Cp), 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. 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 INDMZRside.png|side view of (indenyl)2ZrMe2 INDMZRtop.png|Top view of (indenyl)2ZrMe2 INDMZRdownC2.png|View of (indenyl)2ZrMe2 down C2 symmetry axis.{{cite journal|author1=Atwood, J. L. |author2=Hunter, W. E. |author3=Hrncir, D. C. |author4=Samuel, E. |author5=Alt, H. |author6=Rausch, M. D. |title=Molecular Structures of the Bis(.Eta.5-Indenyl)Dimethyl Derivatives of Titanium, Zirconium, and Hafnium|journal=Inorganic Chemistry|year=1975|volume=14|issue=8|pages=1757–1762|doi=10.1021/ic50150a003}} The indenyl effect refers to an explanation for the enhanced rates of substitution exhibited by η5-indenyl complexes vs the related η5-cyclopentadienyl complexes.