Conformationally rigid diamide complexes of zirconium: Electron deficient analogues of Cp(2)Zr

Zirconium complexes bearing a pyridine-diamide ligand [2,6-(RNCH(2))(2)NC5H3](2-) (R = 2,6-diisopropylphenyl, 2,6-diethylphenyl (BDEP), 2,6-dimethylphenyl) have been synthesized. The mixed amide complexes [2,6-(RNCH(2))(2)NC5H3]Zr(NMe(2))(2) are prepared in high yield from [2,6-(RHNCH(2))(2)NC5H3] and Zr(NMe(2))(4). The mixed amides react with excess ClSiMe(3) to afford the dichlorides [2,6-(RNCH(2))(2)NC5H3]ZrCl2 in nearly quantitative yield. Dimethyl complexes are prepared from [2,6-(RNCH(2))(2)NC5H3]ZrCl2 and 2 equiv of MeMgBr. A single-crystal X-ray diffraction study of (BDEP)ZrMe(2) revealed a distorted trigonal bipyramid structure with the amides occupying the axial positions. The frontier orbitals of a model of the fragment (BDEP)Zr are very similar the those of Cp(2)Zr, suggesting that complexes bearing the pyridine-diamide ligand may behave as sources of Cp(2)Zr.