Preparation of organozirconium aromatic compounds in mixed aqueous-organic solvents: X-ray structures of [Cp2ZrCl(μ2-O′,O"C-C6H5)], [(CpZr)3(μ2-O′,O"C-C6H3Cl2)3(μ3-OH)(μ2-OH)3](Cl2C6H3COO)2, and [(CpZr)3(μ2-O′,O"C-C6H4Cl)3(μ3-OH)(μ2-OH)3]Cl2•CH2Cl2

A new and facile method is presented for the synthesis of zirconocene carboxylate compounds, in which zirconocene dichloride (Cp2ZrCl2) is dissolved in 1 M aqueous HCl solution and the requisite ligand is dissolved in an organic solvent. Five such compounds [Cp2ZrCl(mu(2)-O',O '' C-C6H5)] (1), [Cp2ZrCl(mu(2)-O',O '' C-C6H3Cl2)] (2), [Cp2Zr(mu(2)-O',O '' C-C6H3(OH)Cl)(2)] (3), [Cp2Zr(mu(2)-O',O '' C-C6H3(OH)(NO2))(2)] (4), and [Cp2Zr(mu(2)-O',O '' C-C6H(OH)Cl-3)(2)] (5) have been obtained by this method. The effect of pH on the stability of Cp2ZrCl2 in 1 M HCl solution has been investigated by UV/vis spectrophotometry and H-1 NMR spectrometry. The results showed that the aqueous Cp2ZrCl2 solutions became less stable with increasing pH, liberating cyclopentadiene. Accordingly, at higher pH (similar to 7), two trinuclear zirconium monocyclopentadienyl compounds, [(CpZr)(3)(mu(2)-O',O '' C-C6H3Cl2)(3)(mu(3)-OH)(mu(2)-OH)(3)](Cl2C6H3COO)(2) (6) and [(CpZr)(3)(mu(2)-O',O '' C-C6H4Cl)(3)(mu(3)-OH)(mu(2)-OH)(3)]Cl-2 center dot CH2Cl2 (7), were obtained. All compounds 1-7 have been characterized by FT-IR, H-1 NMR spectra and elemental analysis. In all of the compounds, the aromatic acid acts as a bidentate ligand in coordinating to the zirconium; both chelating and bridging modes are observed. X-ray crystallographic studies on 1, 6, and 7 have revealed that the geometries at zirconium are distorted octahedral in 6 and 7, and distorted trigonal-bipyramidal in 1. (C) 2009 Elsevier B.V. All rights reserved.