CONFORMATIONALLY RIGID DIAMIDE COMPLEXES OF ZIRCONIUM - ELECTRON-DEFICIENT ANALOGS 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 exce ss 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 bipyr amid structure with the amides occupying the axial positions. The fron tier orbitals of a model of the fragment (BDEP)Zr are very similar the those of Cp(2)Zr, suggesting that complexes bearing the pyridine-diam ide ligand may behave as sources of Cp(2)Zr.