Seven-co-ordination in metal complexes of quinquedentate macrocyclic ligands. Part IV. Crystal and molecular structures of two pentagonal bipyramidal iron (II) complexes

Abstract

The crystal structures of two iron(II) complexes of stoicheiometry [FeL(NCS)₂], where L is a 15- or 16-membered ‘N₅’ macrocycle, have been determined. Crystals of (I)(L = C₁₅N₅H₂₃) are triclinic with a= 12.923(11), b= 7.165(9), c= 11.673(8)Å, α= 93.24(11), β= 90.75(11), γ= 110.40(12)°, Z= 2, space group P. Crystals of (II)(L = C₁₆N₅H₂₅) are monoclinic, space group P2₁/c with a= 7.746(8), b= 11.747(12), c= 24.367(18)Å, β= 102.08(12)°Z= 4. The two structures were solved by Patterson and Fourier methods from 1 057 and 1 131 independent reflections above background collected by counter methods and refined to R 0.058 and 0.060, respectively. In both structures, the metal atoms have distorted pentagonal bipyramidal environments with the thiocyanate ligands in axial positions and the five nitrogen aioms of the macrocycle in equatorial positions. The Fe–N bond lengths and the conformations of the girdles are different in the two molecules as a consequence of the extra CH₂, group in (II). However, both molecules have similar structures to those of the analogous Fe^III cations.