Mono- and bis-(2-dimethylaminoethyl)tetramethylcyclopentadienyl zirconium(IV) complexes: synthesis and structural studies in crystalline state and in solutions

A novel half-sandwich Zr(IV) complex [η5:η1-N-C5(CH3)4CH2CH2N(CH3)2]ZrCl3 (6) together with zirconocene dichlorides [η5-C5(CH3)4CH2CH2N(CH3)2][η5-C5(CH3)5]ZrCl2 (4) and [η5-C5(CH3)4CH2CH2N(CH3)2]2ZrCl2 (5) have been prepared. Complex 6 has been isolated and characterized in three different forms, namely, as an adduct with THF 6a, an adduct with tetrahydrothiophene 6b, and a solvent-free form 6c. Molecular structures of complexes 4, 6b, and 6c have been established by X-ray diffraction analysis. Complex 6c has been shown to be a monomeric solvent-free half sandwich Zr(IV) complex. The dynamic behavior of complex 6a in a non-solvating medium (an equilibrium between 6a and 6c along with a degenerate interconversion of the Zr–Ccp–CH2–CH2–N(CH3)2–(Zr) pseudo-five-member metallacycle) have been studied by the variable-temperature 1H and 13C{1H} NMR spectroscopy. The activation parameters for the degenerate five-member cycle interconversion have been elucidated.