Synthesis, crystal structure, and physical properties of the monoclinic form of the R4Mo4O11 compounds (R=Yb and Lu) containing infinite chains of trans-edge-shared octahedral clusters

Polycrystalline samples and single crystals of the R4Mo4O11 compounds (R=Yb and Lu) were synthesized by solid-state reactions at high temperature in sealed Mo crucibles. The structure of Lu4Mo4O11 (a=10.5611(1), b=5.61930(5), c=15.6877 (2), β=99.5131(4) and Z=4) was determined by single crystal X-ray diffraction and refined by least squares on F2 converging to R1=0.0425, wR2=0.0980 for 3508 intensities. Contrary to the R4Mo4O11 compounds with lighter rare earths, which crystallize in the orthorhombic space group Pbam, the Yb and Lu compounds crystallize in the monoclinic space group P2/m. The R4Mo4O11 compounds contain distorted infinite oxide-molybdenum chains of trans-edge-sharing Mo6 octahedra diluted with the rare earths. Magnetic susceptibility measurements indicate that the oxidation state of the Yb atoms is +3, affording 14 metallic valence electrons per Mo4 fragment and, the absence of localized moments on the Mo network. Resistivity measurements on single crystals show that the Yb4Mo4O11 and Lu4Mo4O11 compounds are small band-gap semi-conductors.