Structure of Ethylene Oxide Oligomer Complexes. I. A 1:1 Complex of Tetraethylene Glycol Dimethyl Ether with Mercuric Chloride

Molecular and crystal structure of a 1 : 1 molecular complex of tetraethylene glycol dimethyl ether CH3O-(CH2CH2O)4CH3 (TGM) with mercuric chloride has been determined by means of X-ray diffraction. The complex has a monoclinic unit cell with a=14.29, b=15.10, c=7.84 Å, and β=97.0°. The space group is P21/n. Four molecules of both TGM and mercuric chloride are contained in the unit cell. The structure was determined by the ordinary heavy atom method. The molecular conformation of TGM in the complex is approximately CH3–O–CH2–CH2–O–CH2–CH2–O–CH2–CH2–O–CH2–CH2–O–CH2–CH2–O–CH3, where T, G, and indicate trans, gauche, and minus gauche forms, respectively. All the CH2–O bonds are trans, while the CH2–CH2 bonds are gauche and minus gauche in the adjacent chemical units. The conforma-tional unit of O–CH2–CH2–O–CH2–CH2– was found to be very important and favorable for coordination between the O and Hg atoms. The molecule is circular but not closed, and the five oxygen atoms, which are nearly coplanar and located at the inner side of the circular molecule, enclose one HgCl2 molecule with close interatomic distances (2.78–2.96 Å) between the O and Hg atoms.