Heteropolytungstate complexes of the lanthanide elements. Part I. Preparation and reactions

Abstract

Salts of the anions Ln111Wl o0357-(Ln = La, Ce. Pr, Nd, Sm, Ho, Er, Yb, and Y) and Ce1"Wl0O3~-have been prepared and analysed. The formulae of the previously reported 8-tungstocerates are revised. All the anions are unstable outside the pH range 5-5-8.5, and stable solutions of the free acids cannot be obtained. Lanthanide cations react rapidly with unsaturated heteropolyanions to give complexes LnL and LnL, (L = SiW,,0,9e-, etc.). Salts of several of the LnL, complexes have been isolated. The mode of co-ordination of L is discussed.THE only lanthanide element hitherto known to be capable of acting as the heteroatom in a heteropolyanion is cerium. The 12-molybdocerate(1v) anion, CeMo120,,8-, has long been kn0wn.l More recently, Ripan and Todorut reported 8-tungstocerate-(111) and -(Iv) anions , -* which they formulated CeW,0B5-and CeW,0B4-after analysing a number of salts and titrating solutions of the free acids. We have re-investigated the tungstocerates and have prepared salts of heteropolytungstate anions with other lanthanides (La, Pr, Nd, Sm, Eu, Ho, Er, and Yb, and also Y) as heteroatoms. We find, however, that all the anions are hetero-10rather than hetero-8-tungstates. We have also examined the reaction of lanthanide cations with the heteropolyanions SiWl103,8-, PWllO3d-, and P2W1,-O6,lo-which result from the partial degradation of the corresponding hetero-12-or hetero-18-tungstate anions in near-neutral sol~tion.~ These ' unsaturated ' anions, L, react6 with divalent and trivalent cations of the first-transition series to give complexes of stoicheiometry ML which are members of a larger family of heteropoly-anion^.^,^ We find that with lanthanide cations complexes ML and ML, are formed, and have isolated salts of the latter. EXPERIMENTALHetero-1 O-tungstates.-The general preparative procedure was based on that of refs. 2 and 3. A hot aqueous solution of sodium tungstate (pH 6.5-7.5; a pH just over 7 gave the best yield) was treated dropwise with a warm solution of the lanthanide chloride or nitrate. The sodium salt which separated from the filtered solution a t 5" was converted into the potassium, caesium, ammonium, or guanidinium salt which was recrystallised several times and analysed.lO-TungstoPraseudymate(II1) .-Na,W0,,2H20 (50 g, 0.15 mol) was dissolved in water (100 ml) and the pH was adjusted to 7.2 with glacial acetic acid. A warm, neutral solution of Pr(NO,),, prepared from Pr6011 (2.6 g, 0.0152 g

Luminescent Polyoxotungstoeuropate Anion‐Pillared Layered Double Hydroxides

“…Literature methods were used to prepare sodium or potassium salts of the polyoxotungstoeuropate anions [EuW 10 O 36 ] 9-, [49] [Eu-(BW 11 O 39 )(H 2 O) 3 ] 6-, [31] and [Eu(PW 11 O 39 ) 2 ] 11-. [50] The Zn-Al LDH starting material, ZnAl[NO 3 -], was prepared as described previously.…”

Spectroscopic Studies of Polyoxometalates and their Complexes with Lanthanide(III) Ions in Solution

“…The sandwich complexes, furst proposed by Peacock and Weakley [22] based on stoichiometry and IR spectra, were confirmed by X-ray investigation of Cs12[U(GeW11O39)2.14H2O, K16[Ce(P2W17O61)2].50H2O and Ce(W5O18)9-2 [23]. In these complexes, both uranium and cerium were coordinated to the two ligands via 4 oxygen atoms each in an approximate square anti-prismatic configuration.…”

Modular Polyoxometalate‐Layered Double Hydroxide Composites as Efficient Oxidative Catalysts

“…Na3[PW12O40]·15H2O [39] (Na-PW12), K6[P2W18O62]·14H2O [40] (K-P2W18), Na9LaW10O36·32H2O [41] (Na-LaW10) and the tripodal ligand-stabilized layered double hydroxide (Tris-LDH-CO3) [21] were synthesized according to the literature procedures, respectively. The POMs were intercalated into Tris-LDH-CO3 by using anion-exchange method under CO2-existing conditions.…”