Analysis of crystallographic and structural data of polymeric FeM (M = transition metals, lanthanides) complexes

This review covers crystallographic and structural data for almost fifty polymeric FeM complexes (M = transition Cu, Ag, Au, Mo, W, Mn, Co, Ni and Pt and lanthanide elements Sm, Er and Yb) where iron is involved in polymeric chains. The complexes are for the most part yellow or black, but there are complexes of brown, orange, red, purple, blue and green colour. The complexes crystallized in the monoclinic (by far prevails), triclinic, tetragonal, orthorhombic, trigonal, hexagonal and rhombohedral crystal classes. The iron atoms are found in oxidation states 0, +2 and +3, of which +3 by far prevails. The inner coordination spheres about the Fe(0) atom are tetrahedral (FeC₄) or sandwiched (FeC₁₀), Fe(II) atoms are six-coordinated, and Fe(III) are six or even seven-coordinated. The inner coordination about M atoms range from four- through six- to eight-coordinated. The shortest Fe-Fe, Fe-M (transition) and Fe-M (lanthanide) and M-M separations are: 8.08 Å, 3.033 Å for Fe-Cu, 3.010 Å for Fe-Yb and 2.505 Å for Mo-Mo.