Polyoxotungstates containing uranyl group: Germanotungstates with Keggin sandwich structure

A new sandwich polyoxometalate based on Keggin-type monolacunary polyoxotungstoborate anion, [Zr(α-BW11O39)2]14−

“…In the development of POM chemistry, lacunary polyoxoanions play an important role because they can serve as the nucleophilic inorganic multidentate ligands to incorporate the transition metal or lanthanide cations to form the substituted-type POMs [6,7] in which those species based on mono-and trivacant Keggin fragments represent the largest classes, the study of these subclasses has led to the discovery of a large number of compounds [8][9][10][11][12]. Compared with a large number of researches on other structural polyoxometalates, the study on vacant Keggin fragments with a boron atom as the center hetero atom is relatively rare [13][14][15][16][17][18][19][20][21][22][23][24][25][26], and to date only two examples determined by X-ray single-crystal diffraction are known, both of them contain a Keggin-type monolacunary polyoxotungstoborate anion coordinated to lanthanide cation, one is K 8.5 H 3.5 [Eu(BW 11 O 39 )-(W 5 O 18 )]Á25H 2 O, containing a Keggin-type monolacunary polyoxotungstoborate anion coordinated to europium with an isopolyoxotungstate anion [18], and another is H 2 (NH 4 ) 10 [Ce 2 (B-W 11 O 39 ) 2 (H 2 O) 6 ]Á21H 2 O, a one-dimensional polymer where Keggin-type anions are bridged by Ce 3+ cations [23].…”

“…In the IR spectra, the wavenumber of the main bands of [a-BW 12 2) aqueous solution displays a couple of peaks at À683(E pc ) and À468 mV(E pa ) in the potential range from À1200 to 500 mV, which corresponds to the redox processes of [a-BW 11 O 39 ] 9À , but no wave in the potential range 300-1000 mV was observed in the cyclic voltammogram, so it is indicated that there is no redox processes of complexed zirconium ion. Similar behaviors were observed in the other reported compounds [30].…”

“…To our knowledge, this is the first report of crystal structure for the sandwich Keggin-type polyoxotungstoborate.The compound was synthesized by the conventional solution method[28]. It was formed by self-assembly of the WO 2À 8À at room temperature or the saturated [a-BW12 O 40 ] 5À while increasing the temperature, and when pH is larger than 8, the polyanion may be destroyed only leaving borate and tungstate in solution…”

The actinides

“…38 A number of phosphorus ylids form complexes with uranyl salts-at 0 1C, two uranyl nitrate complexes [UO 2 (ylide) 2 (NO 3 ) 2 ] (ylide = ABPPY, BPPY) containing O-bound ylide are obtained (the first U VI ylides); under reflux, BPPY forms the salt 39 Uranyl groups with pentagonal bipyramidal coordination are found in two Keggin-type germanotungstates, Na 14 [Na 2 (UO 2 ) 2 (GeW 9 O 34 ) 2 ]Á Á ÁxH 2 O (x = 42, 48). 40 One carboxylate complex [(UO 2 ) 2 (m 2 -OH)(pdc) 2 Zn(bpy)(Ac) 2 (H 2 O) 9 ] possesses infinite water cluster chains, which help to hold together the polymeric structure, whilst [UO 2 (pdc)(H 2 O)] has microporous channels capable of adsorbing suitable small molecules like H 2 O and MeOH. 41…”

Structural peculiarities of actinyl complexation with monolacunary polyoxometalates

“…The first structurally characterized polyoxometalate compounds of An(VI) with trilacunary anions, [M 2 (UO 2 ) 2 (α-PW 9 O 34 ) 2 ] 12-(M= Na, NH 4 , K), were described in paper [5] which stimulated increase of interest to structural chemistry of actinide polyoxometalates. Not only the crystal structures of numerous uranyl compounds with different isomers of di-and trivacant anions or condensed "giant" polyoxometalate polylacunary anions have been determined [6][7][8][9][10][11][12][13][14][15], but also Np(V) [16] and Np(VI) [17,18] complexes have been obtained. Progress in structural chemistry of actinide polyoxometalates has been summarized in the work [19].…”