Iron compounds octahedral clusters

For the purposes of this chapter, we limit the discussion to /a-oxo bridged clusters. Model compounds of binuclear octahedral iron without oxo bridges have electromagnetic properties different from the related clusters with ju-oxo bridges (Surerus et al. (1989) only the fi-oxo bridged clusters have been found in proteins so far. 

Cobalt and rhodium also form a series of high nuclearity carbido-cluster compounds. Contrasting with carbido compounds of the iron group which have a clear tendency to put the carbide atom in octahedral cavities, carbides of the group 9 often place it in trigonal prismatic cavities. As shown in scheme in Fig. 3.12, the parent compound [Co6(CO)i5C] of a series of encapsulated car-bido-cobalt species may be prepared by the reaction of Co3(CO)9CCl with [Co(CO)4]. The same scheme also describes some carbido-cobalt cluster interconversions. Rhodium carbide clusters are in general similar to the cobalt ones. 

Typical structural motifs for S-, Sc-, and Te-containing iron cluster compounds shown in Scheme 9 (E, E = S, Se, Te cf. Scheme 1) involve the tetrahedral monocapped species with the closed iron triangle 118 and the dicapped triiron species with the open Fcs framework 121, which can also be regarded as a square-pyramidal c2,EE skeleton with an Fcafifi basal plane 121. The protonated forms of 118 (119 and 120) and the dicapped octahedral structure 122 based on an Fc4 square are also known. Butterfly 11 and interstitial structures (14 and 15 Scheme 1) are very rare for non-first-row main group elements, and a rare example of the /44-S butterfly cluster 116 is discussed in Section... 

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