2, AND 4 AND HPY = PYRIDINIUM - STABILIZATION BY VERY STRONG N-H...O HYDROGEN-BONDS THE CRYSTAL-STRUCTURES OF [HPY]2[SB2OBRNCL6-N] WHERE N = 0

Crystal structures have been determined from X-ray diffraction data for [Hpy]2[Sb2OBrnCl6-n] where n = 0 (1), 2 (2), and 4 (3) and Hpy = pyridinium. The compounds are isostructural, crystallising in the monoclinic space group P21/c, with the following cell dimensions: a = 8.816(3), b = 8.61 5(3), c = 28.116(8) , = 112.73(5) for (1); a = 8.91 9(3), b = 8.81 3(3), c = 28.21 8(8) , = 113.57(4) for (2); and a = 8.982(3), b = 8.884(3), c = 28.343(8) , = 113.80(4) for (3). The structures have been solved by Patterson and Fourier methods and refined by full-matrix least squares to R 0.074 (2 652 observed reflections) for (1), 0.075 (2 887) for (2), and 0.066 (2 706) for (3). The compounds all contain a discrete [Sb2OX6]^2- anion in which the antimony atoms are triply bridged by one oxygen and two halogen atoms. Both (2) and (3) show halogen disorder. In the former, all six halogen positions are involved but the two bridging positions have ca. 53% occupancy by bromine; in (3) the disorder is between the two sets of terminal positions and the bridging positions are uniquely occupied by bromine. A major feature of the structures and probably a great contributor to the overall stability is a very strong hydrogen bond [2.68(1) in (1) and 2.72(1) in (2) and (3)] between the bridging oxygen and one of the pyridinium cations.

THE CRYSTAL-STRUCTURES OF [HPY]2[SB2OBRNCL6-N] WHERE N = 0, 2, AND 4 AND HPY = PYRIDINIUM - STABILIZATION BY VERY STRONG N-H...O HYDROGEN-BONDS Academic Article