Redetermination of the structure of LaMo5O8 by single-crystal X-ray diffraction

We have redetermined the structure of LaMo5O8 by single-crystal X-ray diffraction. Its structure has been determined previously by powder X-ray and neutron diffraction with rather high R factors resulting from impurities in the sample. The crystal structure of LaMo5O8 is based on Mo10O18 cluster units, the Mo cores of which are Mo10 bioctahedra resulting from the edge-sharing of two Mo6 octahedra. These bioctahedral Mo10O18 cluster units share opposite O atoms to form infinite molybdenum oxide chains in which the Mo10 clusters are strongly linked through short Mo-Mo intercluster bonds of 2.6890 (7) A and two weaker Mo-Mo bonds of 2.9108 (5) and 3.0911 (5) A. These chains are then interconnected through Mo-O-Mo bonds to create four-sided channels in which the La3+ cations reside. The Mo-Mo distances within the Mo10 cluster range from 2.6102 (5) to 2.8279 (5) A (average 2.749 A). The Mo-O distances are in the range 1.990 (3)-2.146 (3) A (average 2.076 A). The La3+ cation is surrounded by ten O atoms at distances ranging from 2.443 (3) to 2.919 (3) A with an eleventh O atom at 3.232 (3) A. (orig.)