Synthesis and single-molecule magnet properties of a trimetallic dysprosium metallocene cation

Abstract

The dimetallic fulvalene-bridged dysprosium complex [{Dy(Cp*)(μ-BH₄)}₂(Fv^tttt)] (1, Cp* = C₅Me₅) is converted into the trimetallic borohydride-bridged species [{Dy(Cp*)(Fv^tttt)}₂Dy(μ-BH₄)₃] (2). In turn, 2 is reacted with a silylium electrophile to give [{Dy(Cp*)(μ-BH₄)(Fv^tttt)}₂Dy][B(C₆F₅)₄] ([3][B(C₆F₅)₃]), the first trimetallic dysprosocenium cation. Compound [3][B(C₆F₅)₃] can also be formed directly from 1 by adding two equivalents of the electrophile. A three-fold enhancement in the effective energy barrier from 2 to 3 is observed and interpreted with the aid of ab initio calculations.