An NMR study on the reaction of substituted dimethyl zirconocenes with dimethylanilinium borate

The reaction of a series of dimethyl zirconocenes [Me2Si(Cp)2ZrMe2, 1; Cpt−bu2ZrMe2, 2; Cpn−bu2ZrMe2, 3; Ind2ZrMe2, 4; CpMe42ZrMe2, 5; Cp∗2ZrMe2, 6] with [HNMe2Ph][B(C6F5)4] was investigated by means of NMR spectroscopy. It was found that protonolysis of a Zr–Me group occurred generating a coordinative vacancy at the metal center and methane. Cations coming from 1–4 dimethyl precursors bound NMe2Ph, liberated from the protonation process, and formed zirconaaziridinium ion pairs {[Me2Si(Cp)2Zr(η2–CH2NMePh)][B(C6F5)4], 7; [Cpt−bu2Zr(η2–CH2NMePh)][B(C6F5)4], 8; [Cpn−bu2Zr(η2–CH2NMePh)][B(C6F5)4], 9; [Ind2Zr(η2–CH2NMePh)][B(C6F5)4], 10}, reasonably as a consequence of CH activation of one Me group of coordinated NMe2Ph and methane elimination. The intramolecular/interionic structures and dynamics of 7–10 ion pairs were investigated by 1H, 13C and 19F 1D-and 2D-NMR techniques. The reactions of 7 and 10 ion pairs with 2-methyl-1-heptene afforded stable diastereoisomeric ion pairs bearing a five-member azametallacycle.

Graphical abstractZirconaaziridinium ion pairs were synthesized and fully characterized by means of 1D and 2D-NMR techniques.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Reaction of substituted zirconocenes with [HNMe2Ph][B(C6F5)4] was investigated. ► The effect of ring substituent in the formation of zirconaaziridinium ion pairs was explored. ► Reaction products were fully characterized by NMR spectroscopy.