The structure of the crystalline complex of poly(ethylene oxide) with mercuric chloride, whose composition is (CH2CH2O)4 · HgCl2, has been determined by x-ray diffraction. The unit cell is orthorhombic with the dimensions of a = 13.55 Å, b = 8.58 Å, and c (fiber axis) = 11.75 Å, and the unit cell contains 4 HgCl2 molecules and 16 CH2CH2O units. Four chains pass through the lattice and four monomeric units are contained in the fiber identity period. The space group is Ccmm–D2h17, Ccm21–C2v12, Cc2m–C2v16 or C2221–D25. The positions of Hg and Cl atoms have been determined by the Patterson function synthesized by the use of intensity data of the fiber sample, and the molecular conformation of poly(ethylene oxide) has been determined by examining the space not occupied by mercuric chloride molecules in the crystal lattice. The conformation of polyethylene oxide in the complex has been found to be the form of T5GT5G ; that is, where G and G mean the right- and left-handed gauche forms, respectively. This molecular structure has been confirmed further by the results of the Fourier syntheses by using the more accurate data refined by the intensity measurements with a diffractometer on the powder sample. The bond length between Hg and Cl in the complex (2.30 Å) is a little longer than that of HgCl2 in the crystal (2.25 Å). This is consistent with the fact that the infrared absorption band associated with the antisymmetric stretching vibration of HgCl2 shifts to 353 cm?1 in the complex from 367 cm?1 in the crystal. It was also found that another type of complex, giving a different infrared spectrum and x-ray diffraction pattern, was obtained when the original complex was soaked much longer in a saturated ether solution of HgCl2.
