A Mixed-Valent Molybdenum Monophosphate with a "Butterfly"-Shaped Tunnel Structure Cs6Mo7O9(PO4)7 · H2O

✍ Scribed by A. Guesdon; M.M. Borel; A. Leclaire; A. Grandin; B. Raveau

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 374 KB
• Volume: 111
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1994.1233

✦ Synopsis

A new mixed-valent molybdenum monophosphate (\mathrm{Cs}{6} \mathrm{Mo}{7} \mathrm{O}{9}\left(\mathrm{PO}{4}\right){7} \cdot \mathrm{H}{2} \mathrm{O}) has been isolated by solid state chemistry. It crystallizes in the space group Pnma with (a=10.084(1) \AA), (b=21.297(3) \AA), (c=17.491(1) \AA). Its framework (\left[\mathrm{Mo}{7} \mathrm{P}{7} \mathrm{O}{37}\right]{\infty}) consists of two kinds of structural units formulated (\mathrm{Mo}{4} \mathrm{P}{6} \mathrm{O}{30}) and (\mathrm{Mo}{3} \mathrm{PO}{16}). The (\mathrm{Mo}{4} \mathrm{P}{6} \mathrm{O}{30}) units are built up from two edge-sharing (\mathrm{MoO}{6}) octahedra sharing their corners with two other (\mathrm{MoO}{6}) octahedra and six (\mathrm{PO}{4}) tetrahedra, whereas the (\mathrm{Mo}{3} \mathrm{PO}{16}) units, which also exhibit two edge-sharing octahedra, can be derived from the first type of units by removing one octahedron and five tetrahedra. The structure can then be described by the association of (\left[\mathrm{MO}{4} \mathrm{P}{6} \mathrm{O}{28}\right]{\infty}) layers, built up of corner-sharing (\mathrm{Mo}{4} \mathrm{P}{6} \mathrm{O}{30}) units, with (\left[\mathrm{Mo}{3} \mathrm{PO}{15}\right]{\infty}) chains, built up of corner-sharing (\mathrm{Mo}{3} \mathrm{PO}{16}) units. A comparison with leucophosphite is made. The host lattice (\left[\mathrm{Mo}{7} \mathrm{P}{7} \mathrm{O}{37}\right]{\infty}) delimits two kinds of tunnels running along a: a large butterfly-shaped tunnel where the (\mathrm{Cs}^{+})ions and (\mathrm{H}{2} \mathrm{O}) molecules are located, and smatler tunnels occupied by (\mathrm{Cs}^{+})ions only. Besides these tunnels, cages are also obtained, fully occupied by (\mathrm{Cs}^{+})ions. The ordered distribution of (\mathrm{Mo}(\mathrm{V})) and (\mathrm{Mo}(\mathrm{IV})) species is also demonstrated: (\mathrm{Mo}(\mathrm{V})) sits in (\mathrm{MoO}{6}) octahedra that exhibit one free apex, whereas Mo(IV) sits in the edge-sharing octahedra of the (\mathrm{MO}{4} \mathrm{P}{6} \mathrm{O}{30}) units. 1994 Academic Press, Inc.