Pentanuclear complexes, cyanide-bridged

Three types of pentanuclear cyanide-bridged complexes were described, namely, TBPs, cross-shaped clusters, and open chains. As shown by the Dunbar group (173-177), the TBP architecture is amenable to a wide variety of transition metal ions. In fact, neutral complexes of the general formula [M tmphen)2]3[M CN)6]2 were prepared with 22 different combinations of metal ions (Table V). In these structures (Fig. 34), two [M (CN)6] anions occupy the axial positions of the TBP core. Three cyanide ligands of each hexacyanometalate unit act as bridges, whereas... 

An interesting case of spin transition behavior was discovered in our laboratories for the pentanuclear complex [Co(tmphen)2]3[Fe(CN)6]2 (175), which adopts a TBP structure (175, 176) (Fig. 34). Strictly speaking, this compound does not undergo spin crossover, but we consider this compound in the current section because its properties are unique among discrete cyanide-bridged clusters. As established by a combination of X-ray crystallography, Mossbauer spectroscopy. 

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