Acta Crystallographica Section C

Crystal Structure Communications

Volume 64, Part 5 (May 2008)

metal-organic compounds

 

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

A. Neuba, E. Akin, S. Herres-Pawlis, U. Flörke and G. Henkel

Abstract: The title compounds, namely 2,6-bis[(1,3-dimethylimidazolin-2-ylidene)amino]pyridinium perchlorate, C₁₅H₂₄N₇⁺·ClO₄^-, (I), and bis{2,6-bis[(1,3-dimethylimidazolin-2-ylidene)amino]pyridinium} -oxido-bis[trichloridoiron(III)], (C₁₅H₂₄N₇)₂[Fe₂Cl₆O], (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 N²,N⁶-bis(1,3-dimethylimidazolin-2-ylidene)pyridine-2,6-diamine, which associates in centrosymmetric pairs via two N-HN hydrogen-bond interactions. N-HN bridges are formed between the protonated pyridine N atom and one of the nonprotonated guanidine N atoms, with NH distances of 2.01 (1)-2.10 (1) Å. Compound (I) contains two crystallographically independent cations and anions per asymmetric unit. One of the perchlorate anions is disordered, while the [Fe₂Cl₆O]^2- anion lies on an inversion centre.

Formula: C₁₅H₂₄N₇⁺·ClO₄^- and (C₁₅H₂₄N₇)₂[Fe₂Cl₆O]

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