- Pseudohalogen
Pseudohalogens are binary
inorganic compounds of the general form XY, where X is acyanide ,cyanate ,thiocyanate etc. group and Y is any of X, or a truehalogen . Not all combinations are known to be stable. Examples includecyanogen , (CN)2, andiodine cyanide , ICN. These anions behave ashalogen s and the presence of the internaldouble bond s ortriple bond s do not appear to affect their chemical behavior.Nanoclusters of
aluminium (often referred to assuperatom s) are sometimes considered to be pseudohalogens since they, too, behave chemically ashalide ions, forming Al13I2− (analogous to I3−) and similar compounds. This is due to the effects ofmetallic bonding on small scales.Another complex pseudohalogen is
dicobalt octacarbonyl , Co2(CO)8. This substance can be considered as adimer of thehypothetical cobalt tetracarbonyl, Co(CO)4. It can easily be reduced to the "pseudo -halide ", Co(CO)4-. The acid HCo(CO)4 is in fact quite a strongacid , though its lowsolubility renders it not as strong as the truehydrohalic acid s.References
*New Scientist, issue 2495 (16th April 2005), pp30-33, "A new kind of alchemy", Philip Ball.
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