Iron compounds chalcogen complexes

An interesting singularity in polynuclear chalcogen/carbonyl complexes is the tetranuclear iron compound [Fe4Te(CO) 16l-- which has no metal-metal bonds. 

In contrast to the chalcogen-bridged complexes, no similar oxygen-bridged compounds of iron, cobalt, or nickel exist. However, we obtained such oxo or i-ol-carbonyl complexes of chromium and its homologs, as well as of rhenium. The compounds are the products of the reactions of the respective metal carbonyls with bases (VII). 

Compared with cluster complexes of lower nuclearities, the number of mixed chalcogen/carbonyl complexes having more than six metal atoms is small. Besides some complexes containing iron and cobalt, no manganese compound within this class of complexes is known. 

The second octanuclear mixed chalcogen/carbonyl compound so far known is the complex anion [Fe8Te8(Te2)(CO)2o] . " " This novel cage system (Fig. 31) contains two cuboidal Fe4Te4(CO)ioTe2 fragments, which share the atoms of the ditelluride group. With a total of 144 valence electrons, the complex anion is electron-precise without any iron-iron bonds. 

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