Polynuclear chloromercurate(II) systems in their chloropyridinium salts

Abstract

The chloromercurate(II) salts of 2-, 3- and 4-chloropyridine display a variety of anion stoichiometries and structures, including the rare [Hg3Cl10]4− stoichiometry. 2-Chloropyridinium trichloromercurate(II), (I), (C5H5ClN)[HgCl3], monoclinic, P21/n, a = 9.094 (8), b = 18.143 (4), c = 12.902 (3) Å, β = 106.13 (4)° with Z = 8, has the [HgCl3]− stoichiometry, but the anions are infinite chains composed of [HgCl3]−, HgCl2 and Cl− moieties linked by longer Hg...Cl contacts. Hydrogen bonds link the cations to the formal Cl− ions. Tetrakis(3-chloropyridinium) decachlorotrimercurate(II), (II), (C5H5ClN)4[Hg3Cl10], monoclinic, P21/n, a = 7.522 (2), b = 28.046 (3), c = 9.165 (2) Å, β = 105.78 (2)° with Z = 2, has the rare [Hg3Cl10]4− stoichiometry and contains infinite one-dimensional double-stranded {([HgCl4]2−)2 [HgCl2]} n anionic chains made up of linear HgCl2 and distorted [HgCl4]2− entities linked together by longer Hg...Cl contacts. The HgCl2 moieties are joined by double [HgCl4]2− bridges. Hydrogen bonds link the cations to the sides of the anionic columns. Tetrakis(4-chloropyridinium) decachlorotrimercurate(II), (III), (C5H5ClN)4[Hg3Cl10], triclinic, P1¯, a = 9.907 (3), b = 13.226 (2), c = 7.282 (2) Å, α = 84.41 (2), β = 74.81 (2), γ = 87.34 (2)° with Z = 1, also has the [Hg3Cl10]4− stoichiometry and the same type of {([HgCl4]2−)2[HgCl2]} n anionic chains that were found in compound (II), but the formal HgCl2 and [HgCl4]2− moieties are more discrete with much weaker contacts linking the individual units. Bifurcated hydrogen bonds with the cations cross-link the anionic chains to form an infinite two-dimensional network. Second forms of the 3- and 4-chloropyridinium salts were also obtained. 3-Chloropyridinium trichloromercurate(II), (IV), (C5H5ClN)[HgCl3], monoclinic, P21/c, a = 7.243 (5), b = 22.145 (8), c = 12.320 (3) Å, β = 99.52 (3)° with Z = 8, has the [HgCl3]− stoichiometry, but the anions are infinite chains composed of distorted [Hg2Cl6]2− moieties. Bifurcated hydrogen bonds from the cations cross-link the anionic chains to form infinite two-dimensional layers. Bis(4-chloropyridinium) hexachlorodimercurate(II), (V), (C5H5ClN)2[Hg2Cl6], monoclinic, C2/m, a = 13.447 (3), b = 7.534 (2), c = 9.939 (2) Å, β = 97.48 (2)° with Z = 2, contains highly symmetrical discrete [Hg2Cl6]2−anions. Bifurcated hydrogen bonds from the cations interconnect the anions to form infinite one-dimensional chains.