Coordination of the Hexacyanoferrate(III) Anion to a Polyammonium Macrocycle. Crysta -Structure of [H₄L]_1.5[Fe(CN)₆]₂ (L=6,13-Dimethyl-1,4,8,11-tetraaza-cyclotetradecane-6,13-diamine)

Abstract

Crystals of [H₄L]_1.5[Fe(CN)₆]₂.3H₂O.¾HCN form readily from an aqueous solution of L=6HCI (L = 6,13-dimethyl-1,4,8,11- tetraazacyclotetradecane-6,13-diamine) and Na₃ [Fe(CN)₆]. The compound is monoclinic, space group P2₁/c, a 7.982(6), b 20.785(3), c 26.81(1) Å , β 101.37(5), Z = 4. Protonation is complete at the terminal primary nitrogens, but in the ring one trans pair is protonated and the other not, with short trans H…H distances. Hydrogen-bonding interactions are a feature of the structure, but are concentrated more strongly at the terminal NH₃⁺ groups. Interactions of [Fe(CN)₆]^3- nitrogens with both terminal amine protons and macrocycle ring amine protons are observed, and this structure represents a further example of a 'super complex' involving a complex anion and a protonated polyaza macrocycle.