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Synthesis, Physical Properties, and Theoretical Study of R 16 Mo 21 O 56 Compounds (R = La, Ce, Pr, and Nd) Containing Bioctahedral Mo 10 Clusters and Single Mo Atoms

1999; American Chemical Society; Volume: 38; Issue: 20 Linguagem: Inglês

10.1021/ic981234a

1520-510X

Philippe Le Gall, Régis Gautier, Jean‐François Halet, P. Gougeon,

Nanocluster Synthesis and Applications

Polycrystalline samples and single crystals of R(16)Mo(21)O(56) compounds (R = La, Ce, Pr, and Nd) were synthesized by solid-state reactions at high temperature in sealed Mo crucibles. The structure of La(16)Mo(21)O(56) was determined by single-crystal X-ray diffraction methods. It crystallizes in a monoclinic lattice, P2(1)/c, with a = 13.532(2) Å, b = 13.464(1) Å, c = 13.447(1) Å, beta = 99.681(7) degrees, and Z = 2. It is isostructural to Ce(16)Mo(21)O(56) and Nd(16)Mo(21)O(56) previously reported. The R(16)Mo(21)O(56) compounds contain bioctahedral Mo(10) clusters and MoO(6) octahedral units linked together via oxygen bridges. Magnetic susceptibility measurements indicate that the oxidation state of the single Mo atoms is +4 and that of the Ce and Pr atoms is +3, affording 30 metallic valence electrons to the Mo(10) nonmagnetic clusters. Such an electron count per Mo(10) cluster is confirmed by molecular calculations performed on an isolated Mo(10) cluster unit. Resistivity measurements and extented Hückel tight-binding calculations show that the R(16)Mo(21)O(56) compounds are insulating materials.