Synthesis And Single-Molecule Magnet Properties Of A Trimetallic Dysprosium Metallocene Cation

The dimetallic fulvalene-bridged dysprosium complex [{Dy(Cp*)(mu-BH4)}(2)(Fv(tttt))] (1, Cp* = C5Me5) is converted into the trimetallic borohydride-bridged species [{Dy(Cp*)(Fv(tttt))}(2)Dy(mu-BH4)(3)] (2). In turn, 2 is reacted with a silylium electrophile to give [{Dy(Cp*)(mu-BH4)(Fv(tttt))}(2)Dy][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.