title: Rare examples of base pairing via a protonated pyridine N atom in two salts of N2,N6-bis(1,3-dimethylimidazolin-2-ylidene)pyridine-2,6-diamine.
abstract: The title compounds, namely 2,6-bis[(1,3-dimethylimidazolin-2-ylidene)amino]pyridinium perchlorate, C(15)H(24)N(7)(+) x ClO(4)(-), (I), and bis{2,6-bis[(1,3-dimethylimidazolin-2-ylidene)amino]pyridinium} mu-oxido-bis[trichloridoiron(III)], (C(15)H(24)N(7))(2)[Fe(2)Cl(6)O], (II), are structurally unusual examples of the organization of molecular units via base pairing. The cations in salts (I) and (II) are derived from the bisguanidine N(2),N(6)-bis(1,3-dimethylimidazolin-2-ylidene)pyridine-2,6-diamine, which associates in centrosymmetric pairs via two N-H...N hydrogen-bond interactions. N-H...N bridges are formed between the protonated pyridine N atom and one of the nonprotonated guanidine N atoms, with N...H distances of 2.01 (1)-2.10 (1) A. Compound (I) contains two crystallographically independent cations and anions per asymmetric unit. One of the perchlorate anions is disordered, while the [Fe(2)Cl(6)O](2-) anion lies on an inversion centre.
authors.affiliation: Department Chemie, Fakultät für Naturwissenschaften, Universität Paderborn, Warburgerstrasse 100, D-33098 Paderborn, Germany.
authors.forename: Adam
authors.initials: A
authors.lastname: Neuba
authors.forename: Enver
authors.initials: E
authors.lastname: Akin
authors.forename: Sonja
authors.initials: S
authors.lastname: Herres-Pawlis
authors.forename: Ulrich
authors.initials: U
authors.lastname: Flörke
authors.forename: Gerald
authors.initials: G
authors.lastname: Henkel
mesh_terms: D000631:Aminopyridines / Q000737:chemistry*; D020029:Base Pairing; D007093:Imidazoles / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D011522:Protons; D011725:Pyridines / Q000737:chemistry*
chemical_list: D000631:Aminopyridines; D007093:Imidazoles; C529753:N2,N6-bis(1,3-dimethylimidazolin-2-ylidene)pyridine-2,6-diamine; D011522:Protons; D011725:Pyridines; D009584:Nitrogen; C023666:pyridine