text: Benzyl and allyl ligands often exhibit similar chemical properties.  Benzyl ligands commonly adopt either η or η bonding modes. The interconversion reactions parallel those of η- or η-allyl ligands:
  :CpFe(CO)(η-CHPh) → CpFe(CO)(η-CHPh) + CO
  In all bonding modes, the benzylic carbon atom is more strongly attached to the metal as indicated by M-C bond distances, which differ by ca. 0.2 Å in η-bonded complexes. X-ray crystallography demonstrate that the benzyl ligands in tetrabenzylzirconium are highly flexible. One polymorph features four η-benzyl ligands, whereas another polymorph has two η- and two η-benzyl ligands.