Tetrahedral iron centers ligands

Fig. 4. (a and b) Topologically distinct arrangements of protein ligands to tetrahedral iron centers. 

Ferredoxins and high-potential iron proteins (HiPIPs) involve clusters of two, three, and four tetrahedral Fe centers bridged by sulfido donors. The coordination sphere at Fe is completed by thiolate cysteine ligands. 

Iron-sulfur proteins. In an iroinsulfiir protein, the metal center is surrounded by a group of sulfur donor atoms in a tetrahedral environment. Box 14-2 describes the roles that iron-sulfur proteins play in nitrogenase, and Figure 20-30 shows the structures about the metal in three different types of iron-sulfur redox centers. One type (Figure 20-30a l contains a single iron atom bound to four cysteine ligands. The electron transfer reactions at these centers... 

Compared with the T-symmetric edge-bridged complexes described in Sect. 3, there are far fewer examples of T-symmetric complexes in which the octahedrally coordinated metal centers in the vertices of a tetrahedron are linked by tripodal tris-(bidentate) ligands that occupy the tetrahedral faces. In a one-pot reaction, the tetranuclear iron(III) chelate complex [Fe4(L7)4] (22) was generated from benzene-1,3,5-tricarboxylic acid trichloride 20 and bis-tcrt-butyl malonate 21 (R1 = /Bu). Alternatively, hexanuclear trigonal antiprismatic iron chelate complex [Fe6(L8)6] (23) was formed starting from bis-para-tolyl malonate 21 (R2 = pTol) by employing the same reaction conditions as for the synthesis of 22 (Scheme 8) [86-90],... 

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