Hexacyanometallates

L.M. Siperko and T. Kuwana, Electrochemical and spectroscopic studies of metal hexacyanometalate films. I. Cupric hexacyanoferrate. J. Electrochem. Soc. 130, 396-402 (1983). 

Hexacyano-dinickelate (1) ion, 4 141 Hexacyanofeirate ion, 3 24-25 Hexacyanometalate anions, 43 244—245 Hexadecacarbonylhexairidium, reaction with soft nucleophiles, 30 193 Hexadecacarbonylhexarhodium reactions of reduction, 30 176 with soft nucleophiles, 30 193... 

The Structure of Polycyanometalates metal hexacyanometalates. The chemical formulae indicate the... 

The most important feature of all polymeric metal hexacyanometalates is that they possess channels and holes, the size of which is mostly determined by the... 

Since many metal hexacyanometalates have very similar structures, the formation of solid solutions is possible. The positions and can be occupied not only by one kind of ion, but by a variety of similar ions, allowing the existence of substitutional solid solutions with a random distribution of the different ions on their specific positions. Table 2 gives an overview of the types of solid solutions that can be formed and some examples. 

The differences in formal potentials of different metal hexacyanometalates is the basis of tuning the redox properties of PCMs by synthesis of mixed solutions, as far as that is possible due to the ion radii. Examples for a continuous tuning of the hexacyanoferrate redox potential are mixed nickel/iron hexacyanoferrates [30], mixed copper/iron hexacyanoferrates [56], and mixed cadmium/iron hexacyanoferrates [33]. 

Fig. 6 Correlation between the formal potentials of the hexacyanometalate units of the solid hexacyanometalates and the inverse lattice constant L of the solid compounds [53, 55].

Metal pentacyanonitrosyl metalates show an electrochemical behavior similar to that of hexacyanometalates. The compounds show electrocatalytic properties [69]. 

HEXACYANOMETALLATES AS TEMPLATES FOR DISCRETE PENTANUCLEAR AND HEPTANUCLEAR BIMETALLIC CLUSTERS... 

Scheme 1. Generation of five-coordinate Cu geometries. Around a hexacyanometallate core (adapted from Ref. 4 with permission from the American Chemical Society).

The reaction of hexacyanometalates with metal complexes chelated by penta-dentate ligands may afford polynuclear complexes. The presence of the penta-dentate ligand precludes the polymerization that leads to extended systems. The preparation of a representative heptanuclear, mixed-valance iron complex, [Fe (CNFe° (salmeten))6]Cl2 6H20, is detailed herein. 

Propylene oxide is one of the raw materials used to manufacture rubbery and crystalline polyepoxides. R. J. Herold and R. A. Livigni describe propylene oxide polymerization with hexacyanometalate salt complexes as catalyst. Polyphenylene oxide is made by copper catalyzed oxidative coupling of 2,6-dimethylphenol. G. D. Cooper, J. G. Bennett, and A. Factor discuss the preparation of copolymers of PPO by oxidative coupling of dimethylphenol with methylphenylphenol and with diphenylphenol. 

Hexacyanometalate Salt Complexes as Catalysts for Epoxide Polymerizations... 

Salt or Acid Form of Hexacyanometalate + Metal Salt... 

Figure 1. Generalized scheme for preparation of hexacyanometalate salt complex catalysts...

Hexacyanometalate anions containing cobalt (III) and a combination of iron (II) and iron (III) gave the most active catalysts. The particular hexacyanometalate compound used as a precipitant often had an effect on the catalyst preparation. Potassium coprecipitated, with the zinc salts and use of potassium hexacyanometalate resulted in less-... 

No particular significance is attached to the fact that the molar amounts of glyme and diglyme in these two catalysts are almost the same. Extensive vacuum drying of the cobalt catalyst, which reduced the water level from 4.29 to less than 1.0 mole per mole of the zinc salt (and, presumably, reduced the glyme to a similar or larger extent), gave no appreciable effect on catalytic activity. This result emphasizes the nonstoichiometric nature of the catalytic forms of the hexacyanometalate salt complexes. 

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