Polynuclear transition metal complexes of metal⋯metal-bridging compartmental pyrazolate ligands

The present article reviews the structures and properties of di-, oligo- and polynuclear transition metal complexes of substituted pyrazolate (pz) ligands with ligating side arms (Dn) in which the N2-unit of the pyrazole ring acts as a bridge between two metal centres. Extensive literature surveys covering the literature until the beginning of 2008 of symmetrical 3,5-disubstituted ligands of the type D-pz-D-, D2-pz-D2- and D3-pz-D3 with uni-, bi- and terdentate side arms, respectively, as well as of unsymmetrical 3,5-disubstituted ligands of the type D1n-pz-D2m, are presented together with a comprehensive survey of the structurally characterised complexes thereof. Catalytic and/or stoichiometric reactions of the dinuclear systems are discussed where appropriate.