Synthesis, characterization, and reactivity of organometallic Zr(IV) carboxylate complexes

Abstract

A series of zirconium(IV) complexes, [ZrX 2(XDK)], where XDK is the constrained carboxylate ligand m-xylylenediamine bis(Kemp's triacid imide), were prepared and structurally characterized. The solid state structure of the mononuclear carboxylate alkyl complex [Zr(CH 2Ph) 2(XDK)] reveals that one benzyl group is bonded in an η 2-fashion to the metal center. The reactivity of [Zr(CH 2Ph) 2(XDK)] displays its electrophilic character toward nucleophiles strong enough to displace the η 2-benzyl group. Thus, weak sigma donor ligands such as CO, alkynes and anilines do not react, whereas strong sigma donors, such as pyridines and isocyanides, rapidly form the monoadduct [Zr(CH 2Ph) 2(4-tert-butylpyridine)(XDK)] and [Zr{η 2-2,6-Me 2PhNCCH 2Ph} 2(XDK)], an η 2-iminoacyl derivative, respectively. Attempts to prepare zirconium amido complexes with H 2XDK generally afforded the eight-coordinate [Zr(XDK) 2] complex but use of the small amido ligand precursorZr(NMe 2) 4 allowed [Zr(NMe 2) 2(4-tert-butylpyridine)(XDK)] to be isolated in good yield.