Bis(3,5-dimethylpyrazol-1-ato) zirconium complexes as precursors for ethylene polymerisation upon activation with MAO: Syntheses, characterisation and X-ray molecular structure of [Zr(η2-3,5-Me2Pz)2Cl2(η1-3,5-Me2PzH)2]·(3,5-Me2PzH) and [Zr(η2-3,5-Me2Pz)2(CH2Ph)2] (3,5-Me2Pz=3,5-dimethylpyrazol-1-ato)

Abstract The bis(3,5-dimethylpyrazol-1-ato) zirconium complex [Zr(η2-3,5-Me2Pz)2(NMe2)2(NHMe2)2] (2) is obtained by treatment of [Zr(NMe2)4] with 2 equiv. of 3,5-dimethylpyrazole 1. The reaction of the [ZrCl4(THF)2] adduct with 2 equiv. of the potassium salt of 1 affords the dichloro derivative [Zr(η2-3,5-Me2Pz)2Cl2]n (3), while reaction with 4.1 equiv. of 1 in the presence of 2.1 equiv. of NEt3 affords the dichloro pyrazole adduct [Zr(η2-3,5-Me2Pz)2Cl2(η1-3,5-Me2PzH)2] (4). Treatment of [Zr(CH2Ph)4] with 2 equiv. of 1 gives the dibenzyl complex [Zr(η2-3,5-Me2Pz)2(CH2Ph)2] (5) via alkane elimination. Compound 4 presents fluxional behaviour in CDCl3 solution, which was studied and quantified…