Salts of 2-amino-5-iodo­pyridinium

Abstract

Compound 1 is the anhydrous form of the known crystal 2-amino-5-iodo­pyridinium bromide monohydrate and crystallizes in layers inclined ∼40° to the ab face. Hydrogen bonding between the amino and pyridinium ions to the bromide ion acceptor stabilizes the layers. Compound 2 is a salt of 2-amino-5-iodo­pyridium and a trihalidocobaltate(II) ion with one coordinated 2-amino-5-iodo­pyridine ligand. The halide ions are mixed Cl/Br with differing occupancies.

Reaction of 2-amino-5-iodo­pyridine (5IAP) with concentrated HBr at room temperature yielded 2-amino-5-iodo­pyridinium bromide, C₅H₆IN₂⁺·Br⁻ or (5IAPH)Br. The complex formed pale-yellow crystals, which exhibit significant hydrogen bonding between the amino and pyridinium N—H donors and bromide ion acceptors. Halogen bonding is also observed. Similarly, reaction of 5IAP with cobalt(II) chloride in mixed HCl/HBr in 1-propanol yielded 2-amino-5-iodo­pyridinium (2-amino-5-iodo­pyridine-κN¹)bromido/chlorido­(0.51/2.48)cobalt(II), (C₅H₆IN₂)[CoBr_0.51Cl_2.48(C₅H₅IN₂)] or (5-IAPH)[(5IAP)CoCl_2.48Br_0.51], as blue block-shaped crystals. Two of the three halide positions exhibit mixed occupancy [Cl/Br = 0.797 (5):0.203 (5) and 0.689 (6):0.311 (6)], while the third position is occupied solely by a chloride ion. Extensive hydrogen and halogen bonding is observed.