Heteroligated cores

To date, iron-bound carbide occurs in molecular form only in strong-field carbonyl clusters, via CO reduction, and in porphyrin and porphyrin-like dimers,by reduction of tri- or tetrahalomethanes. In the biosynthesis of the FeMo-cofactor, carbide appears to come from the methyl group of S-ade-nosylmethionine, although the process by which it is converted to interstitial carbide remains unresolved. Available routes for carbide incorporation are therefore quite limited, and substantial synthetic development is probably necessary before Fe-C-S clusters can be realized. Alternative heteroligated Fe-Q-S cores, however, have been achieved. These efforts constitute necessary first steps toward the systematic construction of cofactor-relevant heteroligated cores. 

The synthetic manifold in Scheme 5.9 summarizes the preparation of mixed-core [Fe4(N Bu) S4 Cl4P cubane clusters [n = 1-3 35-37). The homoleptic [n, z] = [0,2-/3-] and [4,0/1-] parent species are established, fundamental clusters in Fe-S and Fe-NR chemistry, and the mixed-core derivatives complete the congeneric set. The individual core-heteroligated clusters were synthesized via specific, composition-selective routes, with pure products isolated in moderate-to-good yields. The final cubane assembly reactions are all formal fragment condensations that employ a range of di- and... 

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