Highly variable Zr-CH₂-Ph bond angles in tetrabenzylzirconium: Analysis of benzyl ligand coordination modes

Analysis of a monoclinic modification of Zr(CH₂Ph)₄ by single-crystal X-ray diffraction reveals that the bond angles Zr-CH ₂-Ph in this compound span a range of 25.1° , which is much larger than previously observed for the orthorhombic form (12.1°). In accord with this large range, density functional theory calculations demonstrate that little energy is required to perturb the Zr-CH₂-Ph bond angles in this compound. Furthermore, density functional theory calculations on Me ₃ZrCH₂Ph indicate that bending of the Zr-CH₂-Ph moiety in the monobenzyl compound is also facile, thereby demonstrating that a benzyl ligand attached to zirconium is intrinsically flexible, such that its bending does not require a buffering effect involving another benzyl ligand.