Azide as a Bridging Ligand and Magnetic Coupler in Transition Metal Clusters

The synthesis of transition metal spin-clusters has become an important sub-discipline of coordination chemistry, especially since the discovery of single-molecule magnets (SMMs) in the early nineties. In this context, complexes with high spin-numbers and large anisotropy are particularly desired. The use of the azide ligand to act as a bridge and magnetic coupler within cages of paramagnetic ions has become increasingly common in this field, especially during the last five years, mainly because of the coordination versatility of this ligand, which is capable of bridging several metals in a variety of coordination modes, and its ability to induce ferromagnetic interactions. Several high-spin 3d metal aggregates have been prepared in this manner, a significant number of which behave as SMMs. This review covers the rapid progress made with this relatively recent synthetic approach by describing the structures and summarising the magnetic properties of the systems prepared in this manner. Some of the trends identified could serve as a privileged starting point for the further development of this promising area. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)