Complexation of Heteropoly Anion [MnMo9O32]6− with Lanthanide Ions

Abstract

Previously, the 95 Mo and 139 La NMR study [1] confirmed complexation of heteropoly anion ( HPA ) of the type [ X IV Mo 9 O 32 ] 6-for X IV = Ni with Ln ions. It was shown that complex formation involves the cis -MoO 2 group of heteropoly ligand. The coordination active center is formed by two O atoms of the Mo 3 O 13 triplet and the O atom of the MoO 6 octahedron.This work was undertaken with the aim to study complexation of [ MnMo 9 O 32 ] 6-( HPA1 ) with Ln 3+ ions using electron and IR spectroscopies and X-ray diffraction analysis. EXPERIMENTALThe synthesis of the salts [ N ( CH 3 ) 4 ] 2 La [ HMnMo 9 O 32 ] · 6 H 2 O ( II ) and (NH 4 ) 6 [MnMo 9 O 32 ] · 8 H 2 O ( III ) was carried out following the procedures described in [2] and [3], respectively. In order to obtain single crystals of heteropoly complex ( HPC ) [ La 2 ( H 2 O ) 12 ( MnMo 9 O 32 )] · 2 H 2 O ( I ) , the analytical grade La chloride was added to a freshly prepared solution of ammonium salt of HPA1 with concentration ~2 × 10 -3 mol/l (Mn : La = 1 : 10). In 7-10 days, in the presence of the "pract" grade tetramethylammonium chloride ( c = 3-5 × 10 -3 mol/l), at room temperature, crystals I were formed as plates. In this case, crystals of the La salt [ N ( CH 3 ) 4 ] 2 La [ HMnMo 9 O 32 ] · 6 H 2 O, having the cubooctahedral form, were not formed. Note that tetramethylammonium ions do not enter the composition of a new HPC 1 , but their presence in a solution is necessary for the crystals of a complex to be formed.Crystals I were analyzed as follows. A weighed sample (0.2 g) was treated with a 5% NaOH solution. The precipitates of MnO 2 · x H 2 O and La 2 O 3 · y H 2 O formed on boiling were separated by subsequent dissolution of La(III) hydroxide in dilute HNO 3 (1 : 20). Lanthanum was determined by complexometric titration with methyl orange indicator [4,5]. The content of Mn was found by dissolving MnO 2 · x H 2 O in a titrated solution of the Mohr salt; an excess of Mn was determined by permanganatometric method [6]. A filtrate obtained after separation of Mn(IV) and La(III) was used to determine Mo as PbMoO 4 [7]. The water content was found by calcining a separate weighed sample at 500°ë .The electronic absorption spectra of I were recorded on a SF-4A spectrometer at 350-540 nm (UV spectra were referenced to a solution of HPA1 with La; the spectra in a visible region were referenced to water, l = 1 cm).The concentration of HPA1 solutions was 2 × 10 -3 mol/l in terms of a heteroatom. The Ln 3+ ions were added as solutions of Ce nitrate and La chloride with concentration 5 × 10 -2 mol/l. The titre of Ln(III) solutions was established by complexometric method [4,5]. The ratio HPA1 : Ln(III) solutions was 1 : 0.2 (at pH 4.23 for Ce(III) and pH 4.30 for La(III)), since at a higher amount of Ce, the study of complexation was difficult due to the formation of precipitates, characterized by For [La 2 (H 2 O) 12 (MnMo 9 O 32 )] · 2H 2 O Abstract -The properties of [MnMo 9 O 32 ] 6-heteropoly anion (HPA 1), as a macroligand with respect to the lant...

Syntheses, Structures and Spectroscopic Characterization of Extended Waugh‐Type Polyoxometalates with Metal Ions as Linkers

“…2a). There are two kinds of crystallographic independent sodium ions, Na(1) and Na (2). The coordination surroundings of them are completed by five terminal oxygen atoms from two homochiral [MnMo 9 O 32 ] 6Ϫ polyanions and a coordinated water molecule (Na1ϪO: 2.299Ϫ2.543 Å ; Na2ϪO: 2.319Ϫ2.450 Å ).…”

“…In the aspect of synthesizing new compounds based on such precursors, examples are very few. Gavrilova and Molchanov reported a lanthanum ion derivative of [MnMo 9 O 32 ] 6Ϫ polyanion [2]. Recently, our group also reported a supramolecular compound based on [MnMo 9 O 32 ] 6Ϫ and moroxydine [3].…”

“…Because the Waugh-type polyanions have multiple coordination active centres, being good candidates as building blocks to react with electrophilic substrates, we further studied the reaction between [MnMo 9 O 32 ] 6Ϫ and metal ions. Two compounds, (NH 4 ) 4 2 ] 3ϩ bimetal aggregates to form two kinds of alternately arranged zigzag chains, which are further weaved into a 2D polymeric sheet by sodium ions. In addition, the influence of the synthesis conditions has also been studied.…”