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

The dimetallic fulvalene-bridged dysprosium complex [{Dy(Cp*)(μ-BH 4 )} 2 (Fv tttt )] (1, Cp* = C 5 Me 5 ) is converted into the trimetallic borohydride-bridged species [{Dy(Cp*)(Fv tttt )} 2 Dy(μ-BH 4 ) 3 ] (2). In turn, 2 is reacted with a silylium electrophile to give [{Dy(Cp*)(μ-BH 4 )(Fv tttt )} 2 Dy][B(C 6 F 5 ) 4 ] ([3][B(C 6 F 5 ) 3 ]), the first trimetallic dysprosocenium cation. Compound [ 3 ][B(C 6 F 5 ) 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. The first trimetallic dysprosocenium single-molecule magnet is described. This material signposts a polycationic dysprosium metallocene SMM with properties that could surpass those of leading systems.