Metal carbonyl clusters featuring only two chemically and electrochemically reversible oxidation states

2 Metal carbonyl clusters featuring only two chemically and electrochemically reversible oxidation states 

3 HTMCC featuring three chemically and electrochemically reversihle oxidation states 

The first two entries are examples of HTMCC with a planar metal framework. In the [AuFe4(CO)i6] n = 1,2,3) system only the parent monoanion has so far been investigated by X-ray diffraction (Fig. la) whereas the corresponding di- and trianions have only been characterized spectroscopically. The [AuFe4(CO)i6] anion can be considered as a square-planar d Au- + complex stabilized by two bidentate [Fe2(CO)8] ligands, isolobal with diphosphine. Crystal-field theory 

The [Fe3Cu3(CO)i2] trianion is isoelectronic with [Fe3Pt3(CO)i5], and has an identical metal framework. EHMO calculations indicate, however, a wide HOMO-LUMO gap of ca 3 eV the composition of its HOMO is, furthermore, 

A series of carbonyl-substituted osmium clusters of general formula Os6(CO)2i-. Lv (L = P(OMe)3, X = 1-6 L = MeCN, x = 1-3) is also structurally related to [Fe3Pt3(CO)i5] and features six extra cluster-valence electrons. As predicted theoretically,these raft-like osmium clusters have a similar capacity to add two more electrons reversibly. The electro-generated anions are stable on the cyclovoltammetry time-scale. 

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