A selective synthesis of hydroxyborate anions as novel anchors for zirconocene catalysts

Abstract

A new family of hydroxytris(pentafluorophenyl)borate anions [B(C₆F₅)₃OH]⁻ associated with organic and aprotic cations c⁺ (imidazolium, pyrrolidinium and phosphonium) has been prepared by a general one-pot synthesis that implies the chloride borate analogues [B(C₆F₅)₃Cl]⁻[c]⁺. The [c]⁺[B(C₆F₅)₃OH]⁻ salts have been isolated and fully characterized. The borate anion [B(C₆F₅)₃OH]⁻ has been shown to protonate the Zr–Me bond in the Cp₂ZrMe₂ complex forming CH₄ and the first published example of anionic [Cp₂Zr(Me)OB(C₆F₅)₃]⁻ species. Standard spectroscopic methods demonstrate the covalent character of the Zr metal center and the anionic character of the boron atom. This protonolysis methodology using [B(C₆F₅)₃OH]⁻ anion affords a new route for the incorporation of a covalently bonded anionic functionality on organometallic complexes. This provides a new way to immobilize transition metal complexes in ionic liquids.