A NEW MIXED-VALENT OXIDE OF COBALT(I, II) - RB5CO2O4

For the first time we obtained a new mixed-valent oxide of mono- and divalent Cobalt. Black-red single-crystals of Rb5Co2O4 were prepared by heating powders of ''Rb6CdO4'' in closed Co-cylinders at 500-degrees during 48 days. Structure solution and refinement are covered by two measurements with four-circle diffractometers. MoKalphaBAR: 2145 I(o)(hkl), out of 2818 I(o)(hkl), R = 9.85%, R(w) = 5.93% AgKalphaBAR: 1813 I(o)(hkl) out of 4007 I(o)(hkl), R = 9.46%, R(w) = 6.51%) and confirm the space-group P1BAR. The lattice constants are a = 696.4(1) pm, b = 922.2(3) pm, c = 958.9(3) pm, alpha = 117.99(2)degrees, beta = 89.96(2)degrees, gamma = 108.12(2)degrees, Z = 2 According to its composition Rb10[OCoO]2[OCoO2CoO] the structure is built up by two Co atoms of chemically and crystallographically different nature. We find isolated dumb-bell-like anions [O-Co-O]3- being already known with monovalent Co (e.g. K3CoO2) together with units [OCoO2CoO]4- of two connected triangles CoO3 being well-known from K2BeO2 = K4[Be2O4]. ECoN/MEFIR calculations are made starting with values obtained by a new procedure called ''MEFIR-FIT''.