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Synthesis and characterization of two centrosymmetric cobalt(III/II/III) compounds, [CoII{(μ-L1)(μ-OOCCH2CH2COOH)CoIII(DMF)}2](ClO4)2 (1) and [CoII{(μ-L2)(μ-OOCCH2CH2COOH)CoIII(DMF)}2](ClO4)2·2CH3CHO (2) with two tetradentate ligands, H2L1 (2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(phenol) and H2L2 (2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(4-chlorophenol), and succinate as anionic co-ligands have been reported. Single crystal X-ray diffraction studies have confirmed the structures of the compounds.

Different synthetic routes and structures of several lead(II) and mercury(II) complexes with diamine-based bis-pyridine Schiff base ligands have been discussed in this review. The applications of the complexes have also been included. It is noteworthy that only those complexes are considered in this review whose X-ray structures are available.

The cyanide groups of [Cr(CN)6]3−, [Mo(CN)8]3− and [W(CN)8]3− may be used to bridge several mono-nuclear transition metal-salen complexes to form different di-, tri-, tetra- hexa- and poly-nuclear complexes of different molecular architectures. The synthetic strategy of the complexes generally involves the formation of H2salen type ligands by the 1:2 condensation of the appropriate diamine and salicylaldehyde derivatives in appropriate solvent at the beginning, followed by the formation of mononuclear transition metal-salen complexes, which are finally connected by [Cr(CN)6]3−, [Mo(CN)8]3− and [W(CN)8]3− bridges to form poly-nuclear complexes. In some cases, however, transition metal-salen units were not isolated, but they have been used in situ to synthesize cyanide bridged poly-nuclear complexes. The magnetic properties of these complexes are interesting. This review represents an overview on the synthetic strategies, structures, magnetic properties of these complexes. It is noteworthy that only those complexes are considered in this review whose X-ray structures are available.

Hydrazine may be used to form azines, which are widely used as very good chelating ligands for the synthesis of complexes of different transition and non-transition metals. Mono-, di- and poly-nuclear zinc(II) complexes with di-azine Schiff bases have been synthesized and their structures and properties have been reported in literature. Few hetero-nuclear zinc(II)-lanthanoid(III) complexes are also included in this review. This review represents an overview of the synthetic strategies, structures and properties of these complexes. The less explored areas of potential applications of these complexes are also highlighted.