Di(alkylamido)zirconium dichlorides and tri(arylamido)zirconium monochlorides having hemilabile N, O ligands and their methyl derivatives

•LiN(R)SiMe2(OtBu) react with ZrCl4(THF)2 to give L2ZrCl2 or L3ZrCl, depending on R.•L2ZrCl2, L = N(tBu)SiMe2(OtBu), shows low activity for ethene polymerization.•Arylamides furnish complexes of the type L3ZrCl.•L3ZrCl complexes, when treated with MeMgBr, produce L3ZrMe.

For their potential use in the polymerization of α-olefins, secondary amides with pendent N-tert- butyoxydimethylsilyl groups and some of their zirconium complexes were synthesized. Treatment of cis-ZrCl4(THF)2 with LiLtBu, where LtBu is the anion of the mixed N, O-donor ligand Me2Si(OtBu) (NHtBu), gave cis-(LtBu)2ZrCl2. A single-crystal X-ray analysis revealed a pseudo-octahedral zirconium center with two chlorides and two chelating N, O ligands. Substitution of tert-butylamine with p-toluidine or p-anisidine furnished the sterically smaller Me2Si(OtBu) (NH-p-C6H4Me) = HLpTol and Me2Si(OtBu) (NH-p-C6H4OMe) = HLpAnis, respectively. Reactions of cis-ZrCl4(THF)2 with two equivalents of either LiLpTol or LiLpAnis invariably gave only the triamido–monochlorido complexes (LpTol)3ZrCl and (LpAnis)3ZrCl, respectively. Alkylation of these monochlorides with MeMgBr furnished the corresponding methyl complexes (LpTol)3ZrMe and (LpAnis)3ZrMe. The dichloride cis-(LtBu)2ZrCl2, when activated with MAO, showed low activity for the polymerization of ethylene.

Graphical abstractHemilabile amides of the general formula [Me2Si(OtBu) (NR)]− furnish disubstituted, pseudo-octahedral zirconium complexes of the type L2ZrCl2 when R = tBu, but trisubstituted, pseudo-tetrahedral complexes of the type L3ZrCl with pseudo-threefold symmetry when R = aryl.Figure optionsDownload full-size imageDownload as PowerPoint slide