SYNTHESIS OF 1,2-CYCLOPENTADIENYL DIIMINE ANIONS AND THEIR ZIRCONIUM COMPLEXES

1,2-disubstituted cyclopentadienyl diimine anions are examples of exte nded pi-systems that bind metals through the nitrogen atoms. Reaction of Cp2Mg with benzonitrile gives the product (1,2-C5H3(C(Ph)NH)(2))CpM g(NCPh) (1) in 98% yield. In an analogous manner, the related complexe s (1,2-C5H3(C(Ph)NH)(2))CpMg(OEt2) (2) and (4-Me3SiC5H2)(1,2-(C(Ph)NH) (2))(Me3SiC5H4)Mg(OEt2) (3) were prepared in situ. Demetalation of the se complexes 1-3 yields the corresponding free diimine ligands of form ulation H[(1,2-C5H3(C(Ph)NH)(2))] (4) and H[4-Me3SiC5H2-1,2-(C(Ph)NH)( 2)] (5). Hydrolysis of compound 4 leads to the fulvene derivative 1-(C (OH)Ph)-2-(O=C(Ph))C5H3 (6). The zirconium complexes (C5H3-1,2-(C(Ph)N H)(2))ZrCl3(THF) (7) and (C5H3-1,2-(C(Ph)NH)(2))(3)ZrCl (8) were isola ted from reactions of 4 with ZrCl4(THF)(2). X-ray crystallographic stu dies of 1, 7, and 8 are reported. Evidence suggests that these new 1,2 -disubstituted cyclopentadienyl diimine anions impart some charge delo calization, thus offering a new approach to electrophilic metal center s. This view is supported by EHMO calculations.