M. M. Borel

A new three-dimensional sodium molybdenum(V) hydroxymonophosphate: Na8(Mo2O4OH)3(PO4)3(PO3OH)·12.25H2O

A new sodium molybdenum(v) hydroxymonophosphate, Na8(Mo2O4OH)3(PO4)3(PO3OH)·12.25 H2O has been synthesized. It crystallizes in the monoclinic space group P21 /c with a=13.024(4), b=25.936(4), c=13.276(3) A, β=111.72(2)°. Its structure involves Na[Mo6P4O27(OH)4 ]2clusters similar to those encountered in several other molybdenum(v) hydroxyphosphates. Such clusters built up of two rings of six edge-sharing Mo octahedra interconnected through one NaO6 octahedron differ from those previously described by the fact that hydrogen is mainly connected to the Mo–O bond forming twelve Mo(O5OH) octahedra, whereas among the eight tetrahedra one observes two P(O3OH) tetrahedra and six PO4 tetrahedra. The originality of this structure deals with the fact that such clusters form with several sodium octahedra, Na(H2O)4O2 and Na(H2O)2O4 , a three-dimensional framework that delimits intersecting tunnels running along a, b and c. The coordination of other sodium cations and H2O molecules that can be considered as intercalated species is also discussed.

Intercalation of primary diamines in the lamellar niobate HNb3O8•H2O

Abstract The intercalation of alkyl diamines in the protonic oxide HNb3O8 · H2O is quantitative for the diamines H2Nue5f8(CH2)nue5f8NH2 with n ranging from 2 to 10. All the intercalated oxides [H3Nue5f8(CH2)nue5f8NH3]0.5Nb3O8 · yH2O are hydrated at room temperature; they can be easily and reversibly dehydrated to the oxides [H3Nue5f8(CH2)nue5f8NH3]0.5Nb3O8. The structural behavior of those compounds is compared to that of the alkyldiammonium titanoniobates [H3Nue5f8(CH2)nue5f8NH3]0.5TiNbO5. An interpretation of their structural properties is given which takes into account the tendency of amines to assume an orientation transverse to oxide layers, the conformation of the amine chains, and the tendency to form dense organic layers.

KVPO5, an intersecting tunnel structure closely related to the hexagonal tungsten bronze

Cristallisation dans Pn2 1 a avec a=12,7640, b=10,5153, c=6,3648 A, Z=8; affinement jusqua R=0,028. La molecule est isostructurale avec KTiPO 5 decrit par Masse [Thesis (1974), Univ. of Grenoble, France]. Son reseau mixte comprend des octaedres VO 6 partageant des sommets et des tetraedres PO 4 delimitant des tunnels ou sont localises les cations K. On propose une nouvelle description de la structure. Le reseau hote VPO 5 comprend des chaines infinies doctaedres [VO 3 ] ∞ , de structure bronze de tungstene hexagonale

New mixed valent vanadium monophosphate with an intersecting tunnel structure Ba2V5O8(PO4)4

A new mixed valent vanadium monophosphate Ba2V5O8(PO4)4 has been synthesized. It crystallizes in the space group I1m1 with a=7.6405(1), b=22.777(1), c=11.6157(7) A and β=103.38(1)°. Its framework consists of [V4P4O22 ]∞ layers of corner sharing polyhedra, interconnected by VO4 tetrahedra which delimit tunnels in which the barium atoms are located. The vanadium atoms exhibit three kinds of coordination; pyramidal, octahedral and tetrahedral, in the same framework.

Two new diphosphates with SrV2(P2O7)2 structure: mercury and lead phases

Two new diphosphates of the AV2(P2O7)2 series involving a trans configuration of the bidentate P2O7 groups have been synthesized for A = Hg or Pb. Their structure, determined from a single-crystal X-ray diffraction study is similar to that of the Sr-phase. They crystallize in the P space group, Z= 1, a= 4.848(1)A, b= 6.892(1)A, c= 8.077(2)A, α= 92.65(1)°, β= 93.26(1)°, γ= 106.23(1)°, for the Hg phase and a= 4.804(1)A, b= 7.113(1)A, c= 7.898(2)A, α= 89.78(1)°, β= 92.62(1)°, γ= 106.10(2)°, for the Pb phase. The crystal structures, solved by the heavy-atom method, were refined. The final agreement factors are R= 0.027 and 0.033 for the Hg and Pb phases, respectively.A comparison with the other isotypic members of this series A = Sr, Cd and NaxMoP2O7(0.25 < x < 0.50) is presented. The great similarity between the lead and strontium phases is shown, demonstrating the absence of a lone-pair effect of PbII in this structure. The particular behaviour of the Hg phase is emphasized, due to the ability of this element to adopt the dumbbell (or 2 + 4) coordination; the strong covalent character of HgII induces a significant distortion of the PO4 tetrahedra, rarely observed to date in transition-metal phosphates.

Structure of KVP2O7

Cristallisation dans P2 1 /c avec a=7,3686, b=10,0527, c=8,1874 A, β=106,580°; Z=4; affinement jusqua R=0,027. Le compose du titre possede la meme structure que KMoP 2 O 7 . Le reseau est constitue dunites VP 2 O 11 de sommets communs, qui delimitent des cages, ou sont localises les atomes K. Ces cavites sont interconnectees de maniere a former une structure a tunnels croises

A new mixed valent molybdenum monophosphate with a tunnel structure: Cs3Mo8O11(PO4)8

Abstract A new mixed valent molybdenum monophosphate, Cs3Mo8O11(PO4)8, with a tunnel structure, has been synthesized. It crystallizes in the space group C2/m with a=20.203 (2) A, b=6.370 (1) A, c=14.379 (1) A and β=99.827 (7)°. Its [Mo8P8O43]∞ 3D-framework consists of single phosphate groups, single MoO6 octahedra, and bioctahedral units of corner-sharing octahedra Mo2O11 and of edge-sharing octahedra Mo2O10. The entire host lattice can be described by the association of [MoPO8]∞ chains running along b, through the corners of their octahedra and tetrahedra, and through the edges of their octahedra, forming large tunnels running along b where the Cs+ cations are located. Bond valence calculations show that in the bioctahedral units, the electrons are delocalized between the two Mo atoms.

CaV2O(PO4)2, isotypic with the Cd phase

The new V III monophosphate, calcium divanadium oxodiphosphate, CaV 2 O(PO 4 ) 2 , is isotypic with the Cd phase. Its structure consists of [V 2 PO 7 ]∞ layers, built up from [VO 4 ]∞ rutile chains and [VPO 8 ]∞ chains, interconnected through PO 4 tetrahedra. This framework delimits tunnels running along (011), at the intersection of which the calcium ions are located in a «6 + 1» coordination mode

Structure of Ba0.84Rb3Nb8P5O34

Le bronze du titre est isotype avec Na 2-x K 2 Nb 8 P 5 O 34 , cest-a-dire quil correspond au premier membre de la serie [K 3 Nb 6 P 4 O 26 ] n .KNb 2 PO 8 . Sa structure tunnel est etroitement apparentee a celle des bronzes de tungstene hexagonaux (HTB).

Structure of PbV2P2O10

Cristallisation dans P2 1 /c avec a=5,2306, b=8,5805, c=16,790A, β=91.01°, Z=4; affinement jusqua R=0,032. Ce compose est de meme type que BaV 2 P 2 O 10 . Sa structure est constituee dunites similaires V 2 P 2 O 14 construites a partir dun octaedre VO 6 , une pyramide VO 5 et de deux tetraedres PO 4 . Ces unites delimitent des tunnels dans lesquels les ions Pb sont localises. Coordination differente de Pb par rapport a celle de Ba