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Acetylenedicarboxylic Acid, Cobalt, Coordination Compound, Crystal Structure, Hydrogen Bonding
Abstract:
The crystal structure of [Co(NH3)6](ADC)(HADC) · 2 H2O (1) (ADC2− = acetylenedicarboxylate) (P21/n, Z = 4) was mistakenly described as containing the [Co(H2O)6]3+ ion [I. Stein, U. Ruschewitz, Z. Naturforsch. 2011, 66b, 471–478]. A revision is reported. While attempting to reproduce 1, we isolated phase-pure crystalline material of [Co(NH3)6]Cl2(HADC) · H2O (2), the crystal structure of which was also reported in the article above. Upon standing in the aqueous mother liquor at room temperature for several days, the needle-shaped crystals of 2 disappear, while block-shaped crystals of the formerly unknown compound [Co(NH3)6](ADC)(HADC) (3) grow. Satellite peaks in the X-ray diffraction frames indicate that the crystal structure is incommensurately modulated. Dissolving crystals of 3 in water at elevated temperature leads to plate-shaped crystals of the new compound [Co(NH3)6]2(ADC)3 · 3 H2O (4) upon slow cooling to room temperature. Compounds 2–4 were investigated by elemental analysis, powder X-ray diffraction and infrared spectroscopy. Structural characterization of 4 by single-crystal X-ray analysis was also achieved (P1̅, Z = 2). Complex 1, however, could not be reproduced.
