1H and 13C NMR evidence for the intermediate species 1:η5-C5H4)>2. Cyclopentadienyl C-H bond activation by thermolysis of n, Cp2Zr(R)Cl, and 2

Article abstract of DOI:10.1016/0022-328X(90)80173-W

Thermal decomposition at 80 deg C of n (1) (Cp = η⁵-C5H5), Cp2Zr(R)Cl (2b) (R = cyclohexyl) and (Cp2ZrCl)2 gives the fulvalenide dizirconium complex <(CpZrCl)2(μ-η⁵ : η⁵-C5H4-C5H4)> (4) via the intermediate <(CpZrCl)(μ-η¹ : η⁵-C5H4)>2 (5).Complex (5) can also be prepared by treating Cp2ZrCl2 with sodium amalgam (1.5 eq) in refluxing toluene.In the presence of cyclic polyenes, such as 1,5-cyclooctadiene (1,5-COD) thermolysis of 1 takes place at room temperature probably to give initially a labile ? allyl species, which can be formulated in the case of the reaction with 1,5-COD as Cp2Zr(η³-C8H11)Cl.This is the first example in zirconium(IV) chemistry of cyclopentadienyl C-H bond activation resulting in hydrogenation of unsaturated substrates.