STRUCTURE OF (ETA-5-CYCLOPENTADIENYL)(1,2,3,4,4A,10A-ETA-6-2-METHYL-DIBENZO[B,E][1,4]DIOXINE)IRON(II) HEXAFLUOROPHOSPHATE AT 163-K

[C18H15FeO2][PF6] (I), M(r) = 464.13, monoclinic, P2(1)/c, a = 7.976 (1), b = 8.959 (3), c = 24.936 (8) angstrom, beta = 99.00 (2)-degrees, V = 1760 (1) angstrom3, Z = 4, D(x) = 1.751 g cm-3, lambda(Mo K-alpha) = 0.71069 angstrom, mu = 10.153 cm-1, F(000) = 936, T = 163 (2) K, full-matrix least-squares refinement of (I) converged to R = 0.047 and wR = 0.044 with 3103 reflections [I > 3-sigma(I)] of 4065 total unique reflections. The dihedral angle between the arene rings of the dioxine ligand is 173.8 (1)-degrees; the C-O bond distances to the coordinated ring are significantly shorter than those of the uncoordinated ring. Inclusion of electronegative atoms (i.e. N) in the arene rings of thianthrenes and complexation of iron cyclopentadienyl (FeCp) to the arene rings, resulted in flattening of the dihedral angle. The effect was similar, but more pronounced, in phenoxathiins. The effect of an electron-releasing group (methyl) substituent on the arene ring of a thianthrene FeCp complex was to decrease the dihedral angle; but inconsistently, two methyl groups (in the 2 and 7 positions) increased the angle. Dibenzodioxine and other dibenzodioxines with varying numbers of chloro substituents are planar. The dihedral angle of the title compound is 173.8-degrees. It is not clear whether this is owing to the influence of the substituent methyl group, complexation, or packing forces.