Abstract
The trigonal form of selenourea has been examined by x-ray crystallographic methods both at room temperature and at −100°C. The lattice parameters reported by earlier workers have been refined by least squares to a = 15.285(5) Å, c = 13.007(5) Å at 20°C and a = 15.201(5) Å, c = 12.950(5) Å at −100°C. The space group has been confirmed to be P31 or P32, which requires nine crystallographically distinct SeC(NH2)2 molecules. The crystal structure was solved using Patterson techniques and difference Fourier syntheses, and was refined by least squares using three-dimensional data obtained at −100°C. The unit cell contains nine three-fold spiral chains which run parallel to c. The similarity of the crystal structure to the urea- and thiourea-hydrocarbon complexes in discussed. Evidence is presented of N–H⋯Se hydrogen bonds, supporting their recent discovery in chemically related compounds.
