Transition metal tetramolybdate dihydrates MMo4O13・2H2O (M=Co,Ni) having a novel pillared layer structure

Hydrothermal synthesis in the M/Mo/O (M=Co,Ni) system was investigated. Novel transition metal tetramolybdate dihydrates MMo4O13·2H2O (M=Co,Ni), having an interesting pillared layer structure, were found. The molybdates crystallize in the triclinic system with space group P−1, Z=1 with unit cell parameters of a=5.525(3) A, b=7.058(4) A, c=7.551(5) A, α=90.019(10)°, β=105.230(10)°, γ=90.286(10)° for CoMo4O13·2H2O, and a=5.508(2) A, b=7.017(3) A, c=7.533(3) A, α=90.152(6)°, β=105.216(6)°, γ=90.161(6)° for NiMo4O13·2H2O The structure is composed of two-dimensional molybdenum-oxide (2D Mo-O) sheets pillared with CoO6 octahedra. The 2D Mo-O sheet is made up of infinite straight ribbons built up by corner-sharing of four molybdenum octahedra (two MoO6 and two MoO5OH2) sharing edges. These infinite ribbons are similar to the straight ones in triclinic-K2Mo4O13 having 1D chain structure, but are linked one after another by corner-sharing to form a 2D sheet structure, like the twisted ribbons in BaMo4O13·2H2O (or in orthorhombic-K2Mo4O13) are.