Ditopic bidentate ligand

While Wemer complexes are based on discrete coordination complexes, another type of coordination compound with a distinctive extension into 2D layers through utilization of ditopic bidentate ligands was developed and first reported by K. A. Hofmann in 1897, Ni(NH3)2Ni(CN)4 2(C6H6). Hofmann-type compounds also exhibit inclusion properties of suitably sized guest molecules. Iwamoto and coworkers prepared a number of derivatives of Hofmann clathrates (Figure 2). 

Figure 5 The structure of gable porphyrin ditron(II) complex with ditopic interaction of bisimidazole ligand, (a) T-state model each iron may be deviated from the porphyrin planes due to short bidentate ligand, bisimidazolyhnethane. (b) R-state model each iron is in-plane because of the sufficient length of bisimidazolylpropane compared to the distance between two Fe atoms...

All of these ligands can be considered as bis-bidentate (bidentate ditopic) and could coordinate simultaneously to two metal cations. 

Ditopic Ligands for the Construction of Bidentate Phosphine Ligands... 

This strategy was particularly elegant, since the reaction between the oxamate ligands with metal ions afforded pre-defined metaUotectons. For example, coordination of Cu(II) through the bidentate N,0-oxamate donor set of 8 was aimed to afford the linear, ditopic metallotecton [Cu (8)] -, while reaction of the same... 

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