Crystal Structure of the Transition-Metal Molybdates and Tungstates. IV. Paramagnetic CuMoO4

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Abstract
Paramagnetic CuMoO4 is triclinic, space group P1̄ , with lattice constants a = 9.903 ± 0.028, b = 6.783 ± 0.015, c = 8.359 ± 0.0019 Å, α = 101.08° ± 0.20°, β = 96.88° ± 0.20°, and γ = 107.05° ± 0.20° at 298°K , with six formula weights in the unit cell. The integrated intensities of 6310 reflections within a reciprocal hemisphere of radius (sinθ) / λ = 1.02 Å−1 were measured with PEXRAD; of these, 3081 were independent and significantly above background. The atomic arrangement is similar to that in ZnMoO4 but with corresponding atoms displaced by as much as 0.4 Å. Refinement by the method of least squares gave a final agreement factor between measured and calculated structure factors of 0.064. Two of the independent copper atoms occupy axially distorted octahedra of oxygen atoms; the four short Cu–O bond distances in each octahedron range between 1.933 ± 0.010 and 1.980 ± 0.012 Å, with an average value of 1.953 Å. The axial Cu–O bonds range in length between 2.213 ± 0.012 and 2.619 ± 0.011 Å, with an average value of 2.364 Å. The third copper atom occupies a distorted tetragonal pyramidal arrangement of oxygen atoms, with basal Cu–O distances ranging from 1.894 ± 0.013 to 1.985 ± 0.010 Å, the average being 1.928 Å; the apical Cu–O bond length is 2.341 ± 0.009 Å. The three independent molybdenum atoms are surrounded by somewhat distorted oxygen tetrahedra with Mo–O distances varying between 1.701 ± 0.010 and 1.862 ± 0.008 Å, the average being 1.772 Å. All atoms in CuMoO4 vibrate with significant thermal anisotropy.

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