Studies in the flexibility of macrocyclic ligands. Crystal and molecular structure of 2,13-dimethy1-3,6,9,12,18-pentaazabicyclo (12.3.1) octadeca-(18),14,16-triene-dichloroion (III) hexafluorophosphate

The crystal structure of the title compound FeL²Cl₂] PF₆] is reported. Crystals are monoclinic with a = 11.747(9), b = 16.051(11), c = 11.964(10)Å, β = 98.1(1)°, Z = 4, Spacegroup P2₁/n. 1173 independent reflections above background have been refined to R 0.09. The coordination geometry around the Fe(III) ion is pentagonal bipyramidal with the two chlorine atoms in axial positions Fe-Cl 2.348(7), 2.354(7)Å]. The five donor nitrogen atoms of the macrocycle form a pentagonal girdle with lengths in the range 2.20(2)–2.25(2)Å. The macrocycle conformation is compared to that found in CuL²]²⁺ and CoL²Cl]²⁺ where the 5N donor set provides respectively trigonal bipyramidal and square pyramidal environments and also to that found in the comparable 7-coordinate FeL¹(NCS)₂]⁺ where L¹ is the related pentaene.