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; Cp^t−bu₂ZrMe₂, 2; Cp^n−bu₂ZrMe₂, 3; Ind₂ZrMe₂, 4; Cp^Me4₂ZrMe₂, 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; [C^pt−bu₂Zr(η²–CH₂NMePh)][B(C₆F₅)₄], 8; [C^pn−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.