STRUCTURES OF HOMOLEPTIC BENZYL DERIVATIVES OF ZIRCONIUM

Crystals of Zr(P-CH2C6H4CMe3)(4), tetra(4-tert-butylbenzyl)zirconium ( 1), have been studied by X-ray diffraction. The crystals belong to the tetragonal system, space group I (4) over bar, with a = 16.481 (2), c = 7.131(4) Angstrom, so that chemically equivalent ligands are also s tructurally equivalent, unlike other known homoleptic M(CH2C6H5)(4) co mpounds. Zr-CH2-C-ipso bond angles of 90.0(2)degrees suggest that liga nds are eta(2)-bonded. The structure is discussed along with that of Z r(CH2C6H5)4, tetrabenzylzirconium (2) (redetermined), which is crystal lographically unsymmetrical but also of approximate S-4 symmetry. The distortion of (2) from tetragonal symmetry (the four Zr-CH2-C-ipso bon d angles being rather different) is discussed along with crystal packi ng.