The Ball‐Shaped Heteropolytungstates [{Sn(CH₃)₂(H₂O)}₂₄{Sn(CH₃)₂}₁₂(A‐XW₉O₃₄)₁₂]³⁶⁻

Abstract

Polyoxometalates can be considered as soluble metal-oxide fragments with an enormous structural variety and a multitude of interesting properties. [1][2][3][4][5][6] The first polyanions were reported almost two centuries ago. [7, 8] Nevertheless, interest in this class of compounds is larger than ever before. The search for novel polyanions is predominantly driven by the catalytic properties of many transition-metal-substituted polyoxotungstates, [9] and by potential applications in bioand nanotechnology.Besides being useful, the symmetry and molecular nature of polyoxometalates are highly attractive features. . [16] Recently we also reported on large polyoxotungstates based on titanium(iv). [17] It is important to realize that the mechanism of formation of polyoxometalates is still not well understood and commonly described as self-assembly. Therefore it is usually not possible to design a multi-step sequence for the synthesis of a novel polyoxometalate. As a result the design of novel polyoxometalates remains a challenge.In our search for a cationic linker which is hydrolytically stable and allows for covalent attachment of organic functional groups we identified the diorganotin group (R 2 Sn 2+ , R = CH 3 , C 6 H 5 etc.) as an interesting candidate. We have already demonstrated that this electrophile can be incorporated in lone-pair-containing polyanion precursors.[18] Furthermore, we have discovered that the two organic groups are always trans to each other, which allows the construction of large polyanions with unexpected geometries. Herein we report the reactivity of dimethyltindichloride with the trilacunary Keggin precursors [A-XW 9 O 34 ] 9À (X = P, As). Interaction of (CH 3 ) 2 SnCl 2 with Na 9 [A-PW 9 O 34 ] in the ratio 3:1 in aqueous medium (pH 4) resulted in the dodecameric, ball-shaped anion [{Sn(CH 3 ) 2 (H 2 O)} 24 {Sn(CH 3 ) 2 } 12 (A-PW 9 O 34 ) 12 ] 36À (1; Figure 1 and Figure 2). We were also able to prepare the isostructural arsenic analogue [{Sn(CH 3 ) 2 -(H 2 O)} 24 {Sn(CH 3 ) 2 } 12 (A-AsW 9 O 34 ) 12 ] 36À (2) by an identical procedure. Both compounds crystallized as mixed cesiumsodium salts and are in fact isomorphous. [19] Owing to the high symmetry of the solid state arrangement (space group Im3 ), the asymmetric unit of 1 and 2 is very small and includes only five tungsten and two tin atoms (Figure 1). The spherical structure of 1 and 2 is spectacular in terms of geometry and size (diameter of % 30 ) and is unprecedented in polyoxotungstate chemistry (Figure 2 and Figure 3). This supermolecular assembly is composed of 12 trilacunary [A-XW 9 O 34 ] 9À (X = P, As) Keggin fragments which are linked by a total of 36 dimethyltin groups (12 inner (CH 3 ) 2 Sn 2+ and 24 outer (CH 3 ) 2 (H 2 O)Sn 2+ groups) resulting in a polyanion with T h symmetry. Note that 1 and 2 have almost 1000 atoms and a

Control of the modularity of {Mo2O2S2}-containing polyoxometalates. Synthesis, structure and characterization of tri- and tetra-modular assemblies based on the [β-B-AsW9O33]9− anion

“…The choice of the dual combination, electrophilic linker/nucleophilic POM unit, represents a key parameter for the targeted geometry of the resulting assembly. The control of the design can be achieved using an electrophilic linker with reduced coordinative requirement as exemplified by Kortz et al using the dimethyltin cation {SnMe 2 } 2+ where four equatorial coordination sites are available [45][46][47][48][49]. The length of the linker can be increased, for example by using the dinuclear unit {Mo 2 O 2 S 2 } 2+ , which permits to enlarge the size of the resulting modular species [50].…”

1D pure inorganic helical chain framework built upon banana-shaped molybdovanadates: Synthesis, crystal structure, and magnetic properties

“…ACCEPTED MANUSCRIPT 4 The plots of χ m T versus T and 1/χ m versus T of compound 1 measured from 2 to 300 K in an applied magnetic field of 1000Oe are shown in Figure 3. The experimental χ m T value of 1 at room temperature is 21.13 cm 3 K mol -1 , which is slightly lower than the expected value 23.75 cm 3 K mol -1 for five isolated Fe 3+ ions (S = 5/2, g = 2.00) and one Co 2+ ion (S = 3/2, g = 2.00) [24][25].…”

Electronic structure and surface properties of the mixed-valence doughnut shaped polyoxomolybdate nanocapsule Mo57V6

“…Large structures can also be formed based on polyoxotungstates. For example, Pope's group isolated a large polyoxotungstate containing 148 tungsten atoms [11][12][13][14][15] and more recently, Kortz et al have synthesized hybrid organic-inorganic polyanions with $1000 atoms containing hydrophobic cavities of up 7 Å in diameter [16]. Furthermore, porous molybdenum oxide based Keplerates capsules [17] may be used as models for Li + nanotransport processes that occur in nature on a cellular level [18,19].…”