Polyoxopalladates Encapsulating Yttrium and Lanthanide Ions, [X^IIIPd^II₁₂(AsPh)₈O₃₂]⁵⁻ (X=Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)

Abstract

A series of novel yttrium- and lanthanide-containing heteropolyoxopalladates have been prepared and isolated as hydrated sodium salts, Na(5)[X(III)Pd(II)(12)(AsPh)(8)O(32)]y H(2)O (X=Y (1), Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Ho (9), Er (10), Tm (11), Yb (12), Lu (13); y=15-27). The polyanions [X(III)Pd(II)(12)(AsPh)(8)O(32)](5-) consist of a cuboid framework of twelve Pd(II) ions with eight phenylarsonate heterogroups located at the vertices and a central guest ion X. The compounds 1-13 have been prepared in a simple one-pot self-assembly reaction of Pd(CH(3)COO)(2), phenylarsonic acid and the respective salt of the element X in 0.5 M aqueous sodium acetate solution (pH 6.9), and characterized in the solid state by single-crystal X-ray diffraction, elemental and thermogravimetric (TGA) analyses, and IR spectroscopy. It was demonstrated that small, medium, and also large lanthanide ions can be incorporated in the center of the novel heteropolypalladate [X(III)Pd(II)(12)(AsPh)(8)O(32)](5-). The Ln-O bond lengths follow the expected trend decreasing from left to right in the lanthanide series. This indicates that the {Pd(II)(12)O(32)} shell can adjust to the coordination requirements of the encapsulated guest cation. Compounds 3 and 5 were selected for electrochemical studies. Their cyclic voltammetry in a lithium acetate buffer at pH 5.9 showed a Pd(0) deposition process on the glassy carbon electrode surface. Coulometry indicated that all Pd(II) centers were reduced to Pd(0). The film was stable and could be taken out of the deposition medium and characterized in pure pH 5.9 buffer. Magnetic susceptibility and EPR measurements were carried out on 5 and 6. The former was confirmed to be diamagnetic and the latter strongly paramagnetic with a S=7/2 ground state. DFT calculations for some of the polyoxometalates have been also performed.

Noble Metals in Polyoxometalates

“…[147] The LnÀO bond lengths within the inner {LnO 8 } cube follow the expected trend, decreasing from Ln = Pr to Lu, indicating the flexible nature of the {Pd 12 O 8 -(PhAsO 3 ) 8 } shell which can adapt to the size of the encapsulated cation guest. [146] The solution stability of the diamagnetic [MPd 12 O 8 (LXO 3 ) 8 ] nÀ polyanions has been confirmed by 31 P or 77 Se NMR spectroscopy on the Se-, PhP-, and P-capped, Zn II -and Lu III -centered derivatives. [147,149] Mass spectrometry measurements on some of the Se IV -and PhAs vcapped POMs showed that in solution they exist as aggregates with Na countercations and protons.…”

“…[145] The central Pd II cation guest in the {Pd 12 } nanocuboid host can be replaced by a large range of lanthanide (Ln) and transition-metal (M) ions (Table 1), by performing the synthesis in neutral or slightly acidic solution in the presence of the respective lanthanide/transition-metal salt. [146][147][148][149] 8 } cube, which appears to be symmetrical based on Xray diffraction studies, is actually strongly distorted on the faster EPR time scale. [147] The LnÀO bond lengths within the inner {LnO 8 } cube follow the expected trend, decreasing from Ln = Pr to Lu, indicating the flexible nature of the {Pd 12 O 8 -(PhAsO 3 ) 8 } shell which can adapt to the size of the encapsulated cation guest.…”

Synthesis and Characterization of the Dicopper(II)‐Containing 22‐Palladate(II)[CuII2PdII22PV12O60(OH)8]20−

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The recently discovered area of water-soluble noble-metalbased polyoxometalates (POMs) [1a] is currently developing fast, not only because of their interesting structures and properties but also because of the promising applications of these compounds. [1][2][3][4][5] Currently polyoxopalladates(II) are the noble-metalbased polyanion family comprising the largest number of members.In 2008 the parent 13-palladate [Pd II 13 As V 8 O 34 (OH) 6 ] 8À ("Pd 13 As 8 ") was reported, which consists of a cuboctahedral {Pd 12 } cage, a central Pd II guest, and eight {AsO 4 } capping groups leading to an overall cubic shape of the polyanion. [1a] Later it was shown that the {As V O 4 } 3À capping groups can also be replaced by {Se IV O 3 } 2À or {PhAs V O 3 } 2À , which unexpectedly lead to coordination numbers of 6 (octahedral) and even 8 (cubic), respectively, for the central Pd II .

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“…The recently discovered area of water-soluble noble-metalbased polyoxometalates (POMs) [1a] is currently developing fast, not only because of their interesting structures and properties but also because of the promising applications of these compounds. [1][2][3][4][5] Currently polyoxopalladates(II) are the noble-metalbased polyanion family comprising the largest number of members.…”

Synthese und Charakterisierung des Dikupfer(II)‐haltigen 22‐Palladats(II) [CuII2PdII22PV12O60(OH)8]20−

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Der erst kürzlich entdeckte Bereich der wasserlöslichen Edelmetall-Polyoxometallate entwickelt sich schnell, nicht nur im Hinblick auf die interessanten Strukturen und Eigenschaften, sondern auch auf die Anwendungen derartiger Verbindungen. [1][2][3][4][5] Gegenwärtig sind Polyoxopalladate(II) die Edelmetall-Polyanionenfamilie mit den meisten Mitgliedern. 2008 wurde über das 13-Palladat [Pd II 13 As V 8 O 34 (OH) 6 ] 8À ("Pd 13 As 8 ") berichtet, das aus einem kuboktaedrischen {Pd 12 }-Käfig, einem zentralen Pd II -Gast und acht überdachenden {AsO 4 }-Gruppen besteht, was insgesamt ein kubisches Polyanion ergibt.

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