ISSN:
1573-1111
Keywords:
X-ray analysis
;
hydrogen bonds
;
molecular complexes
;
crown ethers
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The structure of 18-crown-6·4 thiourea has been determined by single crystal X-ray methods. The unit cell is monoclinic and the space group isP21, witha=9.251(3),b=19.285(8),c=16.556(7) Å and β=90.85(6)°. There are two formula units, C12H24O6·4CH4N2S, in the asymmetric unit; finalR=0.086. One thiourea is attached at either side of the macrocycle (‘biangular’ conformation) via N−N...O bonds and the patterns in the two crystallographically-independent adductsA andB differ slightly, involving two bifurcated hydrogen bonds inA. Core adducts are linked by additional thiourea molecules via N−H...S bonds. As compared to the analogous 18-crown-6·5 urea, the present 1:4 stoichiometry might be attributed to the longer S...N hydrogen bonding distance, i.e., to the bigger van der Waals radius of sulphur.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00665477
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