FeCs clusters

Oxidized, active Fe hydrogenase exhibits an EPR spectrum (g = 2.10,2.05, 2.01 [74]) that could come from low-spin Fec(III). MCD spectroscopy excludes the possibility of a so-called HiPIP, [4Fe-4S]3+ cluster [85,86], It thus appears that the active H cluster contains both an —Fe(CN)2CO-like moiety and a regular [Fe-4S] cubane, i.e., a total of 5Fe. 

Figure 16-12 The structures of some representative carbido carbonyl cluster species, (a) FeC(CO)iS, (b) Ru C(CO)17, (c) [Os10C(CO)24]2-, and (d) Fe4C(CO)13.

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