Cp* as a removable protecting group: low valent Zn(i) compounds by reductive elimination, protolytic and oxidative cleavage of Zn–Cp*

Abstract

Zn–Cp* bond cleavage reactions leading to novel monovalent cationic zinc species are presented (Cp* = pentamethylcyclopentadienyl). The treatment of [Zn₂Cp*₂] with two equiv. of [H(Et₂O)₂][BAr₄^F] (BAr₄^F = B{C₆H₃(CF₃)₂}₄) yields the triple-decker complex [Cp*₃Zn₄(Et₂O)₂][BAr₄^F] (1) via protolytic removal of a Cp* ligand as Cp*H, whereas the reaction with an equimolar amount of [FeCp₂][BAr₄^F] (Cp = cyclopentadienyl) results in the formation of [Cp*Zn₂(Et₂O)₃][BAr₄^F] (2) under oxidative cleavage of a Cp* ring giving decamethylfulvalene, (Cp*)₂, and [FeCp₂] as by-products. The molecular structures of compounds 1 and 2 are established by single-crystal X-ray diffraction studies. A new synthetic pathway for the formation of [Zn₂Cp*₂] based on the reductive elimination of Cp*H from in situ formed Cp*ZnH is presented.