Two new compounds containing tellurite building blocks coordinated to copper and barium atoms have been isolated from hydrothermal solvents. A new layered compound, Ba2Cu4Te4O11Cl4 (I), has been obtained by reacting BaCl2.2H(2)O, CuO, and Te(OH)(6) in NH4Cl solution at 375 degrees C for 4 days. Green, platelike crystals of I crystallize in the centrosymmetric space group, P (1) over bar, with a = 9.275(2) Angstrom, b = 12.135(2) Angstrom, c = 9.263(2) Angstrom, alpha = 95.23(3)degrees, beta = 108.35(3)degrees, gamma = 110.90(3)degrees, and Z = 2. The compound contains two types of layers, one based on copper oxides linked by Te4O11 groups, and the other based on Cu2Cl4 units. The tellurium atoms adopt the common TeO3+1 units or TeO3 pyramids, and the oxygen-coordinated copper atoms adopt a square planar CuO4 arrangement. Dark green, prismatic crystals of BaCu2Te2O6Cl2 (II) were obtained by reacting BaCl2 . 2H(2)O, Cu2O, and Te(OH)(6) in NH4Cl solution at 375 degrees C for 18 h. Compound II was refined in the acentric monoclinic space group, P2(1) (a = 7.434(2) Angstrom, b = 7.448(2) Angstrom, c = 8.271(2) Angstrom, beta = 97.42(3)degrees, Z = 2), and is based on Te2O6 units connected by copper atoms or copper chloride groups. As in I, tellurium atoms are contained within TeO3+1 or TeO3 units and the connecting copper atoms are nearly square planar. The chloride-coordinated copper atoms group adopt a square pyramidal CuO3Cl2 geometry with a chlorine atom occupying the epical position. The formal oxidation stales of the copper atoms in compound I are distributed such that the connecting atoms in an oxide environment are 2+ and atoms within a chloride environment are 1+, whereas in compound II, all copper atoms are 2+. Bond valence sums for both compounds and magnetic susceptibility data for I support these assignments. The optical band gap for I was determined by diffuse reflectance spectroscopy and indicate that it is a wide band gap material (E-g = 3.00 eV).