Multimetallic Half-Sandwich Complexes of the Rare-Earth Metals

Multimetallic half-sandwich complexes of the paramagnetic lanthanides gadolinium, terbium, dysprosium, holmium, and erbium as well as of diamagnetic yttrium are readily accessible via AlMe4/halogenido exchange reactions of Cp*Ln(AlMe4)2 with the mild halogenido transfer reagents Me3SiI and Me3GeX (Cp* = C5Me5; X = Br, Cl). Depending on the rare-earth-metal center and halogenido ion size, complexes with distinct structural motifs and nuclearities are obtained, including dimeric compounds [Cp*Ln(AlMe4)(mu 2-Cl)]2 for the smaller metal centers Ln = Ho, Er, iodido-bridged tetranuclear rings [Cp*Ln(mu 2-I)2]4 (Ln = Y, Tb, Dy, Ho, Er), and a heterobimetallic tetramethylaluminato-bridged gadolinium cluster [Cp*4Gd4I7(AlMe4)]2. The tetranuclear dysprosium complex [Cp*Dy(mu 2-I)2]4 shows single-molecule magnet (SMM) behavior in zero applied field with an effective energy barrier of 164(10) cm-1.