STRUCTURAL INVESTIGATION OF MERCURY-INTERCALATED TITANIUM DISULFIDE .1. THE CRYSTAL-STRUCTURE OF HG1.24TIS2

X-ray powder and single-crystal diffraction have been used together wi th thermogravimetric compositional analysis to determine the crystal s tructure of the superstoichiometric intercalation compound Hg1.24TiS2 at ambient temperature. Hg1.24TiS2 forms an unusual (3 + 1)-dimensiona l layered misfit compound, which can alternatively be described as int erpenetrating three-dimensional TiS2 and Hg sublattices. The symmetry of each sublattice can be described by the monoclinic space group C2/m . These sublattices share commensurate a and c axes but are incommensu rate with each other along the b axis [a = 5.9223(9) Angstrom, b(TiS2) = 3.4076(2) Angstrom, b(Hg) = 2.7566(1) Angstrom, c = 8.862(1) Angstr om, and beta = 102.33(3)degrees]. Hg forms infinite one-dimensional ch ains within the nearly trigonal prismatic sulfur channels created by h ost-layer restacking. The Hg chains exhibit metallic intrachain guest- guest bonding, with a bond distance of 2.76 Angstrom. Comparison of th e intrachain Hg-Hg bond distance to the Hg-n+-Hg-n+ bond distances for compounds containing linear Hg chains with a known ionic valence indi cates the intercalated Hg in Hg1.24TiS2 has very Little ionic characte r. Unlike other transition-metal dichalcogenide intercalation compound s that possess primarily ionic guest-host interactions, this compound exhibits weak covalent guest-host interactions and very Little ionic c harge transfer.