Crystal structure of dichlorido(4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane)iron(III) hexafluoridophosphate

The title compound, [FeCl 2 (C 14 H 30 N 4 )]PF 6 , contains Fe 3+ coordinated by the four nitrogen atoms of an ethylene cross-bridged cyclam macrocycle and two cis chloride ligands in a distorted octahedral environment. In contrast to other similar compounds this is a monomer. Intermolecular C—H...Cl interactions exist in the structure between the complex ions. Comparison with the mononuclear Fe 2+ complex of the same ligand shows that the smaller Fe 3+ ion is more fully engulfed by the cavity of the bicyclic ligand. Comparison with the μ-oxido dinuclear complex of an unsubstituted ligand of the same size demonstrates that the methyl groups of 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane prevent dimerization upon oxidation.