Two Original Infinite Chains in the New Caesium Tetramolybdate Compound Cs2Mo4O13

Abstract

Although dicaesium tetramolybdate, Cs2Mo4013, is a member of the molybdate family, its structure deviates from those of other tetramolybdates. It crystallizes in the monoclinic system with an a parameter six times greater than those of the other tetramolybdates. The structure comprises two different infinite chains of [Mo4013] 2-, which propagate along the [001 ] direction. One contains blocks made up of two MoO6 octahedra sharing a face, which is unusual in molybdate compounds. The asymmetric unit of the other chain consists of a set of two MoO6 octahedra, one M005 square pyramid and one MoOn tetrahedron sharing edges and comers. CommentThe polymolybdate compounds of univalent ions with general formula A2Mo,,O3n+l were studied extensively in the 1970's. Table 3 reports the cell parameters of the known structures. Studies have shown that the structures of these compounds depend on the number of Mo atoms, n and the size of the counter ion, the potassium compounds being taken as structural models. With n = 1, the structure contains isolated MoOn ions of tetrahedral shape. The compounds with n = 2 comprise infinite chains built of blocks of two octahedra sharing an edge, each block being connected through comers by two tetrahedra. The building block of the chain of the n = 3 compounds consists of two trigonal bipyramids connected by an octahedron, each polyhedron sharing edges. With n = 4, the chain starts to widen. It comprises two blocks of two octahedra sharing edges in a plane. Each double block shares an edge with each of two others, situated above and below. When n is greater than 4, only compounds with n odd and prepared with heavy alkaline atoms are known. Their structures consist of double sheets of MoO6 octahedra sharing edges. The n = 4 compounds have been observed with all alkaline atoms except caesium.

Hydrothermal Synthesis of Molybdenum Oxide Based Materials: Strategy and Structural Chemistry

“…This was ascribed to a postulated size mismatch between the large Cs + ion and the [Mo 4 O 13 ] 2− chains 83. However, our hydrothermal experiments have now brought forward the long sought‐after triclinic Cs 2 Mo 4 O 13 84. 85 In addition, the hydrothermal reaction of Mo VI ‐precursor materials with specific alkali iodide combinations afforded new alkali trimolybdates of the (M/M′)Mo 3 O 10 type (M=Rb; M′=K, Cs) 86…”

Characterisation of heterogeneous molybdate and chromate phase assemblages in model nuclear waste glasses by multinuclear magnetic resonance spectroscopy

“…17 Indeed, there exists a series of cesium chromates with identical stoichiometry and similar structure to cesium molybdates (Cs 2 XO 4 , Cs 2 X 3 O 10 , and Cs 2 X 4 O 13 , where X = Mo or Cr). [18][19][20][21][22][23] Chromium is known to exist in waste glasses as eskolaite (Cr 2 O 3 ), or to partition into spinel-type compounds, 24 but the partitioning of Cr into molybdate phases has yet to be explored. We have prepared a series of chromium-containing sodium borosilicate model waste glasses (including cesium and molybdenum) to examine the fate of chromium upon devitrification, specifically its partitioning among glassy and crystalline phases.…”

Electrospray mass spectral study of isopolyoxomolybdates

“…The structures of alkali metal isopolyoxomolybdates with general formula [Mo m O 3m ϩ 1 A 2 ] (where A is an alkali metal ion and m is a positive integer) have also been investigated over the past two decades. 33 Structural studies have shown that the shapes of these compounds depend on the number of molybdenum atoms, m, and the size of the counter cation. 34 Electrospray mass spectrometry (ESMS) has displayed its utility in characterizing polyoxometalates dissolved in organic, aqueous-organic and purely aqueous solutions.…”