X-Ray crystallographic study of guest–molecule orientations in the β-hydroquinone clathrates of acetonitrile and methyl isocyanide
- 1 January 1983
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 6,p. 777-781
- https://doi.org/10.1039/p29830000777
Abstract
Redetermination of the crystal structure of the Type III β-hydroquinone–acetonitrile clathrate, 3C6H4(OH)2·CH3CN (1), from new Mo-Kα diffractometer data confirmed the principal finding of previous studies, namely that the three symmetry-independent acetonitrile molecules fit snugly inside clathration cavities in a pseudo-rhombohedral host lattice (space group P3), with one guest molecule aligned in the opposite sense to the other two. A parallel study of the potentially isomorphous β-hydroquinone–methyl isocyanide clathrate, 3C6H4(OH)2·CH3NC (2), showed that it is a Type II clathrate (space group R3), in which all three guest molecules in the unit cell are equivalent and point in the same direction parallel to the c axis. The effective molecular length (linear molecular skeleton plus the sum of appropriate van der Waals radii at both ends) of CH3NC is inferred to be ca. 0.1 Å longer than that of CH3CN, in keeping with the relative stabilities and unit-cell dimensions of (1) and (2). Lattice parameters are: for (1), a= 16.003(2), c= 6.245(2)Å; for (2), a= 15.946(2), c= 6.348(2)Å. The structures have been refined to R values of 0.080 (1) and 0.056 (2) using, respectively, 1 277 and 600 observed reflections.Keywords
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