Pr4Mo9O18, an Atypical, Novel, Ternary Reduced Molybdenum Oxide Containing Unusual Mo7, Mo13, and Mo19 Clusters. Synthesis, Crystal Structure, and Physical Properties

Abstract

We present here the synthesis, crystal structure, and magnetic and resistivity studies of a remarkable ternary reduced molybdenum oxide Pr4Mo9O18. Its structure was determined on single crystal by X-ray diffraction in the space group R3m (ah = 11.3600(7) A, ch = 50.392(8) A, Vh = 5631.8(9) A3, Zh = 15; arh = 18.032(1) A, αrh = 36.720(3)°). The crystal stucture contains, in addition to the common triangular Mo3 cluster, the new Mo7, Mo13, and Mo19 clusters. Contrary to the previous high-nuclearity molybdenum clusters, the Mo13 and Mo19 present hemispherical and spherical geometries, respectively, while the Mo7 is planar. These four clusters with their oxygen environments form three different slabs parallel to the ab plane. The first slab is composed of Mo3 and Mo7 clusters in equal proportions. An infinite metallic plane based on connected Mo3 and Mo13 clusters forms the second slab. The Mo13 aggregate presents a hemispherical geometry and results from the cis-edge-sharing of three Mo6 octahedra having one...