The Cobalt(II) Oxidotellurate(IV) Hydroxides Co2(TeO3)(OH)2 and Co15(TeO3)14(OH)2

Previously unknown Co-2(TeO3)(OH)(2) and Co-15(TeO3)(14)(OH)(2) were obtained under mild hydrothermal reaction conditions (210 degrees C, autogenous pressure) from alkaline solutions. Their crystal structures were determined from single-crystal X-ray diffraction data. Co-2(TeO3)(OH)(2) (Z = 2, P1 over bar , a = 5.8898(5), b = 5.9508(5), c = 6.8168(5) & ANGS;, alpha = 101.539(2), beta = 100.036(2), gamma = 104.347(2)& DEG;, 2120 independent reflections, 79 parameters, R[F-2 > 2 sigma(F-2)] = 0.017) crystallizes in a unique structure comprised of undulating (2)(& PROP;)[Co-2(OH)(6/3)O3/3O2/2O1/1](4-) layers. Adjacent layers are linked by Te-IV atoms along the [001] stacking direction. Co-2(TeO3)(OH)(2) is stable up to 450 & DEG;C and decomposes under the release of water into Co6Te5O16 and CoO. Magnetic measurements of Co-2(TeO3)(OH)(2) showed antiferromagnetic ordering at & AP; 70 K. The crystal structure of Co-15(TeO3)(14)(OH)(2) (Z = 3, R3 over bar , a = 11.6453(2), c = 27.3540(5) & ANGS;, 3476 independent reflections, 112 parameters, R[F-2 > 2 sigma(F-2)] = 0.026) is isotypic with Co-15(TeO3)(14)F-2. A quantitative structural comparison revealed that the main structural difference between the two phases is connected with the replacement of F by OH, whereas the remaining part of the three-periodic network defined by [CoO6], [CoO5(OH)], [CoO5] and [TeO3] polyhedra is nearly unaffected. Consequently, the magnetic properties of the two phases are similar, namely being antiferromagnetic at low temperatures.

Automated summary

Previously unknown Co-2(TeO3)(OH)(2) and Co-15(TeO3)(14)(OH)(2) were obtained from alkaline solutions under mild hydrothermal conditions. Their crystal structures were determined, and magnetic measurements showed antiferromagnetic behavior at low temperatures. The main difference between the two phases is the replacement of F by OH in the crystal structure.