Novel reactivity of ferrocene derivatives toward Lewis acids: Decomplexation with boron trichloride and synthesis of a triple-decker-like iron-zinc complex

Ferrocene derivatives bearing the 8-quinoline-tetramethyl-Cp ligand (1) possess a free nitrogen donor function. Because of the methyl groups at the Cp ring, the quinoline adopts an orientation that locates the N-donor above the five-membered ring. Additional molecules that are bound by the N-donor function are therefore in proximity to the pi-system of the Cp ring. Zinc dichloride, which binds to the N-donor, interacts slightly with the ferrocene moiety, and the triple-decker-like complex 5 is formed. The more Lewis acidic boron trichloride interacts with the functionalized Cp ring much more strongly so that the iron(II) ion cannot compete and is eliminated. Thus the organoborane 6 with intramolecular donor coordination is formed quantitatively.