Paramagnetic Complexes of Expanded Cage Amine Ligands

The synthesis and characterization of complexes of the macrobicyclic ligand Me₈tricosane (1,5,5,9,13,13,20,20-octamethyl-3,7,11,15,18,22-hexaazabicyclo-[7.7.7]tricosane) with Ni(II) and Mn(II) are reported, along with further details of the synthesis and characterization of complexes of Mn(II) and Cr(III) with the related ligand Me₅tricosane (1,5,9,13,20-pentamethyl-3,7,11,15,18,22-hexaazabicyclo[7.7.7]tricosane). X-ray structural analysis of (H₃O)[Cr(Me₅tricosane)]Cl₄·3H₂O revealed the presence of longer Cr-N bonds than in comparable Cr(III) hexaamine complexes, but this was accompanied by modest alterations to electronic spectroscopy and electrochemical behavior. Both Me₅tricosane and Me₈tricosane formed Mn(II) complexes which exhibited magnetic and electronic properties typical of high spin <i>d</i>⁵ systems. The solid-state structures of [Mn(Me₅tricosane)](NO₃)₂·1.5H₂O and [Mn(Me₈tricosane)]Cl₂·3H₂O revealed a distorted trigonal prismatic MnN₆ chromophore with longer Mn-N bonds than in similar Mn(II) complexes, and both [Mn(Me₅tricosane)]²⁺ and [Mn(Me₈tricosane)]²⁺ exhibited irreversible redox chemistry in cyclic voltammetry experiments. X-ray crystallographic analysis of [Ni(Me₈tricosane)](NO₃)₂·H₂O revealed remarkably long Ni(II)-N bonds, resulting in an unusual blue color for a Ni(II)N₆ complex.