Triangular complexes M Fe, Ru

As illustrated in Fig. 1, all the complexes of formula [M3(CO)i2] (M = Fe, Ru) are characterized by an almost equilateral M3 triangle, although there are some differences in the disposition of their carbonyl groups - in [Fe3(CO)i2] and [Fe2Ru(CO)i2] ten are terminal and two bridge the same edge in [Ru3(CO)i2] and [FeRu2(CO)i2] all are terminal.  

According to normal electron counting rules , these complexes are isoelectronic all have 48 cluster valence electrons (CVE). 

In dichloromethane solution, [Fe3(CO)i2] undergoes two sequential one-electron reductions, Fig. The first step [Fe3(CO)i2]/[Fe3(CO)i2] is chemically reversible whereas the second step [Fe3(CO)i2] /[Fe3(CO)i2] is complicated by slow decomposition of the dianion. 

In contrast, in dichloromethane solution [Ru3(CO)i2] undergoes an irreversible, single-step, two-electron reduction.  

Although a detailed electrochemical investigation has not appeared, it has been reported that [Fe2Ru(CO)i2] and [FeRu2(CO)i2], upon electrolysis at low temperature, afford the corresponding short-lived monoanions,i.e. the mixed-metal complexes seem to exhibit intermediate behavior (single one-electron additions leading, however, to quite unstable anions) with respect to their homonuclear precursors. 

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