SYNTHESIS, STRUCTURE AND PROPERTIES OF NONACHLORODITELLUROUS AND TETRACHLOROHYDROXOTELLUROUS ACID HYDRATES - CRYSTAL-STRUCTURES OF THE OXONIUM SALTS [H9O4]N[TE2CL9]N AND [H9O4][TECL4OH].H2O

Light yellow needles of crystalline nonachloroditellurous acid with the formal composition HTe2Cl9.4H2O (1) (space group C2/c, a = 11.642(6), b = 13.012(4), c = 12.663(5) angstrom, beta = 119.64(3)-degrees at 140 K) were isolated from a saturated solution of TeCl4 in conc. HC1. From a solution of more diluted HC1 the acid HTeCl4OH.5H2O (2) could be prepared (space group P2(1)2(1)2(1), a = 7.065(3), b = 8.551(2), c = 18.192(6) angstrom at 140 K). 1 is the first acid isolated from the system TeCl4/HCl/H2O with a polymeric anion. The novel polynuclear [Te2Cl9]n(n-) chains are built from alternately corner-sharing and edge-sharing distorted octahedral TeCl6 units. The mean bond distances are 2.356 angstrom for terminal Te-Cl and 2.805 angstrom for Te-mu(2) Cl.2 contains square-pyramidal [TeCl4OH]- anions with oxygen in the apical position (Te-Cl: 2.447-2.552 angstrom; Te-O: 1.926 angstrom). The cations in both structures are [H9O4]+ hydroxonium ions (O...O (1): 2.47(3), 2.55(2) and 2.57(1) angstrom; O...O (2): 2.550(4), 2.584(4) and 2.588(5) angstrom). Thus the formulae of the acids have to be written as [H9O4]n[Te2Cl9]n and [H9O4][TeCl4OH] . H2O. Raman spectra of both compounds are reported.