Polyoxotungstate Archetype {P₄W₂₇} and its 3d Derivatives

Abstract

The propensity of the new, phenylphosphonate‐stabilized polyoxotungstate [(C6H5PVO)2P4W24O92]16− to act as a precursor for new 3d metal‐functionalized polyanions has been investigated. Reactions with MnII and CuII induce the formation of the previously unknown polyoxotungstate archetype {P4W27}, isolated as salts of the polyanions [Na⊂{MnII(H2O)}{WO(H2O)}P4W26O98]13− (1) and [K⊂{CuII(H2O)}{W(OH)(H2O)}P4W27O99]14− (2), which were characterized in the solid state (single‐crystal X‐ray diffraction, elemental and TG analyses, IR spectroscopy, SQUID magnetometry) and in aqueous solution (UV/Vis spectroscopy, cyclic voltammetry).

Trigonal Prismatic Coordination of Discrete Rare Earth Ions, Enforced by the Polyoxotungstate [P4W27O99(H2O)]16–

“…[32] The cyclic voltammogram recorded at pH 4.0 in non-buffered 2 M Li 2 SO 4 /H 2 SO 4 medium generally follows the same trend, however only three redox couples, two of which are not very well separated from each other, could be observed in this medium before solvent discharge (Figure S34). [25] in 0.5 M NaOAc buffer (pH 4.8), see Figure S37, clarifies several aspects. Firstly, the first redox couple presumably attributed to the W VI centers directly bound to the heterometal ion [25] appears at nearly the same potential of À 0.405 V for the Mn II and Gd III derivatives, which both comprise the heterometal in trigonal prismatic coordination, and at a significantly more positive potential for the Cu II -based species (À 0.305 V).…”

“…[25] in 0.5 M NaOAc buffer (pH 4.8), see Figure S37, clarifies several aspects. Firstly, the first redox couple presumably attributed to the W VI centers directly bound to the heterometal ion [25] appears at nearly the same potential of À 0.405 V for the Mn II and Gd III derivatives, which both comprise the heterometal in trigonal prismatic coordination, and at a significantly more positive potential for the Cu II -based species (À 0.305 V). The latter could be explained by a release of Cu II ions from the POM due to its reduction to Cu 0 state at À 0.18 V. Secondly, all the other redox couples in the CV graph of Gd3 are shifted to more negative potentials in comparison to the CV curves of the transition metal derivatives, which suggests a higher redox stability for the Ln-POMs.…”

“…We hypothesize that this allows to minimize local pH fluctuations during the reaction and hence decreases a decomposition rate of the POT precursor, thus preventing a presence of significant excess of Ln III 14 À , although the reactions for these derivatives were performed in a sodium acetate buffer medium with higher pH, 4.8). [25] This suggests that P 4 W 24 PhP represents a convenient precursor for the species of the {MP 4 W 27 } structural type, which until now could not be prepared by any other method. Thus, reactions of well-known [H 2 P 2 W 12 O 48 ] 12À ({P 2 W 12 }) [26] [27] POMs with Ln III ions at similar conditions did not result in Lnx polyanions.…”

“…These data are provided free of charge by the joint Cambridge In this regard, the structure of Lnx polyanions is very similar to that of the {MnP 4 W 27 } POM that we recently reported. [25] One of the faces of the O 6 prism is defined by two O atoms of the peripheral W VI centers (one from each W VI ion) and a μ 2 -O connecting it to W c . The second trigonal face of the O 6 prism is formed by two oxygens of the {PW 4 } belts of the {P 2 W 12 } units located on the opposite sides with respect to oxygens coordinated to W c , and a H 2 O ligand.…”

“…Importantly, using a similar synthetic approach, namely reactions of P 4 W 24 PhP with 3d heterometals, we were also able to isolate Mn II and Cu II derivatives of the same {P 4 W 27 } POM archetype as found in Ln x , [Na⊂{Mn II (H 2 O)}{WO(H 2 O)}P 4 W 26 O 98 ] 13− and [K⊂{Cu II (H 2 O)}{W(OH)(H 2 O)}P 4 W 27 O 99 ] 14− , although the reactions for these derivatives were performed in a sodium acetate buffer medium with higher pH, 4.8). [25] This suggests that P 4 W 24 PhP represents a convenient precursor for the species of the {MP 4 W 27 } structural type, which until now could not be prepared by any other method. Thus, reactions of well‐known [H 2 P 2 W 12 O 48 ] 12− ({P 2 W 12 }) [26] and [H 2 P 4 W 24 O 94 ] 22− ({P 4 W 24 }) [27] POMs with Ln III ions at similar conditions did not result in Ln x polyanions.…”