New 1,3-disubstituted side-chain functionalized indenyl ligands and zirconium complexes derived from them

Abstract

New functionalized indenyl ligands Ind X = 1,3 C 9 H 5 (Pr i )(CH 2 CH 2 X) (X = OMe or NMe 2 ) and 1,3 C 9 H 5 (Pr i )[CMe 2 CH 2 (2´ py)] and the zirconium sandwich complexes (Ind X )Cp*ZrCl 2 (Cp* is pentamethylcyclopentadienyl) were synthesized. The photochemical behavior and the reduction reactions of zirconocene dichlorides were investigated. The properties of these compounds are determined mainly by the high lability of Zr-Ind bonds. The reduc tion of (Ind X )Cp*ZrCl 2 (X = NMe 2 ) selectively affords the complex Cp*[η 5 :η 2 (C,N) C 9 H 5 (Pr i )CH 2 CH 2 N(Me)CH 2 ]ZrH as the intramolecular NCH 2 -H bond activation product. The molecular structures of the complex (Ind X )Cp*ZrCl 2 (X = OMe) and its photochemical decomposition product [Cp*ZrCl 2 (OMe)] 2 were established by X ray diffraction.In recent years, it has been shown 1-4 that, due to the unusual η 9 coordination, indenyl ligands containing bulky substituents (SiMe 2 R or Pr i ) at positions 1 and 3 can stabi lize the Zr II center in zirconium sandwich complexes with out loss of high reactivity. In continuation of our studies on the chemistry of functionalized cyclopentadienyl deriv atives of Group IV metals, we synthesized and character ized the complexes [1,3 C 9 H 5 (Pr i )(CR 2 CH 2 X)]Cp*ZrCl 2 (R = H or Me) containing the heteroatomic functional group (X = OMe, NMe 2 , or 2 py) in one of the substitu ents of the five membered ring of the indenyl ligand. In vestigations of the reduction of zirconocene dichlorides and a comparison of these data with the results of our previous research on their tetramethylcyclopentadienyl analogs 5-8 are of particular interest. Results and Discussion Synthesis of ligands and Zr IV complexesDisubstituted indenes 1,3 C 9 H 6 (Pr i )(CH 2 CH 2 X) (X = OMe (1) or NMe 2 (2)) were synthesized by the reac tion of lithium 3 isopropylindenide with ClCH 2 CH 2 X without the isolation of intermediates (Scheme 1). To syn thesize metal complexes, the resulting oily compounds were transformed into the corresponding lithium indenides (Li 1) and (Li 2).