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Uranyl molybdate

The common six- and seven-coordinate uranyl-based polyhedra are also observed in the extended structures of uranyl molybdates containing M02O7 units. For example, the mineral iriginite, [(U02)Mo207(H20)2](H20), and the hydrothermally prepared [(U02)Mo207(H20)2], which is formed under more basic conditions, contain electroneutral sheets of [(U02)Mo207 (H20)2]. "... [Pg.275]

GA. Without additional anions or H2O 7.GB. With additional anions and/or H2O 7.H Uranium and uranyl molybdates and wolframates 7.HA.With 7.HB.With... [Pg.38]

However, in the structure of U2M0O8, adjacent sheets are linked together by sharing apical anions of the U and Mo polyhedra. In the structure of the Ag compound, two adjacent sheets are linked by additional Mo 04 tetrahedra which results in the formation of the complex [Mo502o] ° moiety shown in Fig. 18d. The Ag cations occupy the interior of the double uranyl molybdate sheets and are between the double sheets (Fig. 18d). [Pg.114]

Fig. 26a shows the complex uranyl molybdate sheet from the structure of Cs4[(U02)30(Mo04)2(MoOs)]. Within the sheet, three uranyl pentagonal bipyramids are linked into trimeric units interconnected by Mo polyhedra. In the structure. Mo occurs in three different coordinations (Fig. 26c). The Mo(3) atom... Fig. 26a shows the complex uranyl molybdate sheet from the structure of Cs4[(U02)30(Mo04)2(MoOs)]. Within the sheet, three uranyl pentagonal bipyramids are linked into trimeric units interconnected by Mo polyhedra. In the structure. Mo occurs in three different coordinations (Fig. 26c). The Mo(3) atom...
Fig. 40. The structure of M2[(U02)6(Mo04)7(H20)2] (M = NH4, Rb, Cs) (a) as consisting from double uranyl molybdate sheets (b), and projection of the single sheet (c). Fig. 40. The structure of M2[(U02)6(Mo04)7(H20)2] (M = NH4, Rb, Cs) (a) as consisting from double uranyl molybdate sheets (b), and projection of the single sheet (c).
Actinyl compounds with tetrahedral oxoanions TO4 (T = S, Cr, Se, Mo) that are based upon 3D networks of comer-sharing coorination polyhedra are listed in Table 9. To proceed with their stmctural description, we shall use graph theory analysis of heteropolyhedral frameworks as developed in [221], It turns out that the most actinyl-based 3D units with comer-sharing between chemically different polyhedra can be described as based upon ID stmctural elements for which we adopt the term fundamental chain suggested by Liebau [222] for tetrahedral frameworks in silicates and related materials. However, some actinyl oxosalt stmctures are better described as consisting of polymerized 2D sheets. For convenience, the frameworks will be classified into three major groups (1) frameworks based upon fundamental chains (2) microporous chiral uranyl molybdate frameworks (3) frameworks based upon 2D sheets. [Pg.157]

Microporous uranyl molybdate chiral frameworks. The general chemical formula of these compounds can be written as... [Pg.157]

Fig. 56. 3D uranyl molybdate framework from the structure of a-Cs2[(U02)2(Mo04)3] (a). The framework can he can be derived from the uranyl molybdate sheet observed in (3-Cs2[(U02)2(Mo04)3] (Fig. 53) by cutting it into ID chains (Fig. 56b, c) and re-assembling them into a 3D structure. [Pg.159]

Fig. 58. Uranyl molybdate framework in the structure of Ba(U02)3(Mo04)4(H20)4 (a) can be described as based upon two types of fundamental chains, ll/2a and 11/lb (b and c, respectively). Fig. 58. Uranyl molybdate framework in the structure of Ba(U02)3(Mo04)4(H20)4 (a) can be described as based upon two types of fundamental chains, ll/2a and 11/lb (b and c, respectively).
Fig. 59. The structure of (NH4)4[(U02)5(Mo04)7](H20) projected along the c axis (a), nodal representation of its [(1102)5(1 004)7] framework (b), nodal representation of its fundamental chain (c), and graphs isomorphous to nodal representations of fundamental chains of chiral uranyl molybdate frameworks with the U Mo ratio of 5 7, 4 5 and 6 7 (d, e and f, respectively). Fig. 59. The structure of (NH4)4[(U02)5(Mo04)7](H20) projected along the c axis (a), nodal representation of its [(1102)5(1 004)7] framework (b), nodal representation of its fundamental chain (c), and graphs isomorphous to nodal representations of fundamental chains of chiral uranyl molybdate frameworks with the U Mo ratio of 5 7, 4 5 and 6 7 (d, e and f, respectively).
Fig. 60. Chiral tubular units in the structures of the U Mo = 4 5 and 5 7 uranyl molybdate frameworks can be described in terms of tubular units (b and d, respectively). The tubular units can be obtained by folding and gluing tapes shown in (a) and (c), respectively. Fig. 60. Chiral tubular units in the structures of the U Mo = 4 5 and 5 7 uranyl molybdate frameworks can be described in terms of tubular units (b and d, respectively). The tubular units can be obtained by folding and gluing tapes shown in (a) and (c), respectively.
The alternative description of the 4 5 and 5 7 uranyl molybdate frameworks can be made in terms of tubes or tubular units fused into a 3D framework. Such tubular units for the 4 5 and 5 7 structures are shown in Fig. 60. The topological structure of these tubes can be exposed by unfolding them onto a 2D plane so that the result is a ID graph with local topology identical to that of the tube. To reform the tubular unit, one has to fold the tape and to join the points identified by the same letters. The tubular graphs shown in Figs. 60b and d symbolize channels in the uranyl molybdate frameworks. It is noteworthy that they have a chiral helical structure that is in agreement with the symmetry of the chaimels in the real structures (6522 for 4 5 and 65 for 5 7 frameworks). [Pg.161]

Fig. 62. The structure of U02Mo04(H20)2 projected along the b axis (a). The uranyl molybdate framework in this compound can be spUtted into alternating A and B sheets (c and d, respectively) which are of the same topology (b). Fig. 62. The structure of U02Mo04(H20)2 projected along the b axis (a). The uranyl molybdate framework in this compound can be spUtted into alternating A and B sheets (c and d, respectively) which are of the same topology (b).
Fig. 63. Uranyl molybdate framework in A2[(U02)3(Mo04)4] (A = Na, K) can be described as consisting of uranyl molybdate sheets having the 12/3k topology (a, b) cross-linked by additional UO7 bipyramids and M0O4 tetrahedra (c). The linkage involves formation of (non-chiral) channels running along the b axis (d). Fig. 63. Uranyl molybdate framework in A2[(U02)3(Mo04)4] (A = Na, K) can be described as consisting of uranyl molybdate sheets having the 12/3k topology (a, b) cross-linked by additional UO7 bipyramids and M0O4 tetrahedra (c). The linkage involves formation of (non-chiral) channels running along the b axis (d).
The synthesis of chiral open-framework uranyl molybdates... [Pg.222]

More recently, several chiral open-framework uranyl molybdates have been successfully synthesized by Krivovichev et al., and this greatly enriches the family of... [Pg.222]

S. Krivovichev, C. Cahill, E. Nazarchuk, P. Burns, T. Armbruster, and W. Depmeier, Chiral Open-framework Uranyl Molybdates. 1. Topological Diversity Synthesis and Crystal... [Pg.261]

The uranyl molybdate minerals are relatively poorly characterized. The first uranyl molybdate mineral was recognized by Brophy and Kerr, but since then a number of minerals that belong to this group have been described from many different deposits (Table 14). An affinity of uranium and molybdenum, especially in roll-front type deposits, has been known for some time. Initially, only minerals with U were recognized, but the occurrence of such minerals as sedovite shows that U compounds also exist. [Pg.62]


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See also in sourсe #XX -- [ Pg.343 ]




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