Analysis of a monoclinic modification of Zr(CH 2 Ph) 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−CH 2 −Ph bond angles in this compound. Furthermore, density functional theory calculations on Me 3 ZrCH 2 Ph indicate that bending of the Zr−CH 2 −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.
A new class of tripodal L(2)X ligands that feature three oxygen donors, namely the tris(2-oxo-1-tert-butylimidazolyl) and tris(2-oxo-1-methylbenzimidazolyl)hydroborato ligands, [To(Bu(t))] and [To(MeBenz)], has been synthesized via the reactions of NaBH(4) with the respective imidazolone. Structural and spectroscopic studies indicate that both [To(Bu(t))] and [To(MeBenz)] are significantly more sterically demanding but less electron donating than the related [O(3)] donor ligand, [CpCo{P(O)(OEt)(2)}(3)].
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