Crystal Structures of Cs+-Crown Ether Complexes Containing Polynuclear Mercury Iodide Anions

Reactions of CsI and HgI₂ with benzo-15-crown-5 (B15C5) and 15-crown-5 (15C5) in an ethanol-acetone mixture produced [Cs(B15C5)₂]₂[Hg₂I₆] (1) and {[Cs(15C5)]₂[Hg₂I₆]}_n (2), respectively. The structures of the two complexes are quite different. Molar ratios of Cs⁺ : crown ether are 1 : 2 in 1 and 1 : 1 in 2. Complex 1 consists of two Cs(B15C5)₂⁺ cations and a Hg₂I₆^2- anion. Cs⁺ lies between the two crown-5 ligands, resulting in a sandwich-type cation. Cationic Cs(B15C5)₂⁺ and anionic Hg₂I₆^2- are linked together by electrostatic interactions and the complex 1 is an ion pair compound. Complex 2 consists of infinite [Cs(15C5)]₂[Hg₂I₆] units. Each structural unit contains two Cs(15C5)⁺ cations and a Hg₂I₆^2- anion. Cs⁺ is coordinated by five oxygen atoms of 15C5, three iodine atoms of Hg₂I₆^2-, and an iodine atom of Hg₂I₆^2- in an adjacent structural unit. The interactions between the Cs⁺ of Cs(15C5)⁺ and an I^– in Hg₂I₆^2- from adjacent structural units polymerize the complex 2, resulting in a one-dimensional network structure. The anions of Hg₂I₆^2- in both complexes are similar. The two mercury atoms are linked through two bridging iodine atoms and each mercury is also coordinated by two terminal iodines. Crystal data for 1: space group P2₁/c (No. 14), a = 12.253(4), b = 20.945(7), c = 16.110(6) Å, = 111.0(1)°, V = 3860 ų, Z = 4, R = 0.082 (R_w = 0.089). Crystal data for 2: space group P2₁/c (No. 14), a = 12.157(4), b = 8.546(4), c = 20.666(6) Å, = 91.54(3)°, V = 2146 ų, Z = 4, R = 0.034 (R_w = 0.048).