Monomericα-Keggin-type polyoxotungstate-coordinated mono-and di-palladium(II) complexes, i. e., Cs 5 O 39 {Pd II-(Me 2 ppz)}] • 5H 2 O (Cs-1) (Me 2 ppz = N,N'-dimethylpiperazine), [(CH 3 ) 4 N] 4 H[α-PW 11 O 39 {Pd II (Me 2 ppz)}] • 8H 2 O (TMA-1), and Cs 2.5 H 0.5 [α-PW 11 O 39 {Pd II (en)} 2 ] • 7H 2 O (en = ethylenediamine) (Cs-2), were synthesized by 1 : 1 or 1 : 2 stoichiometric reactions of mono-lacunary α-Keggin polyoxotungstate [α-PW 11 O 39 ] 7À with PdCl 2 (Me 2 ppz) and PdCl 2 (en) in aqueous solution. Subsequent purification from water afforded these compounds as analytically pure homogeneous yellow precipitates. Single-crystal Xray structural analysis of Cs-1 revealed that a palladium(II) moiety, i. e., [Pd(Me 2 ppz)] 2 + , was coordinated to two oxygen atoms in the mono-vacant site of [PW 11 O 39 ] 7À with an asymmetric configuration, resulting in an overall C 1 symmetry. With regard to the crystal structure of Cs-2, two palladium species of the [Pd(en)] 2 + type were coordinated to two oxygen atoms in the mono-vacant site with symmetric configuration, resulting in an overall C s symmetry. A unique structural transformation of the mono-lacunary α-Keggin structure of Cs-1 to the di-lacunary γ-Keggin polyoxotungstate Cs 7 [γ-PW 10 O 36 ] was observed upon the addition of cesium chloride.
Hydrophilic platinum‐polyoxotungstate colloidal particles formed by a self‐assembly of Cs4[{Pt(OH)2}2·SiW12O40] were successfully obtained by calcining a cesium salt of α‐Keggin‐type diplatinum(II)‐coordinated silicotungstate, Cs4[α‐SiW11O39{cis‐PtII(NH3)2}2]·11H2O (Cs‐Si‐Pt), in air at 300 °C. During the thermal treatment, the structure of the mono‐lacunary Keggin‐type silicotungstate ligand {SiW11O39} transformed to that of {SiW12O40}, and the diplatinum sites in Cs‐Si‐Pt transformed to the platinum hydroxides with the elimination of the ammonia molecules coordinated to the platinum sites. All four cesium ions in Cs4[{Pt(OH)2}2·SiW12O40] could be ion‐exchanged by four tetramethylammonium ions, and hydrophilic [(CH3)4N]4[{Pt(OH)2}2·SiW12O40] colloidal particles were also formed in aqueous solution. The calcined sample acted as a photocatalyst for hydrogen evolution from aqueous triethanolamine (TEOA) under visible light irradiation (λ = ≥440 nm) in the presence of Eosin Y, K5[α‐SiW11{Al(OH2)}O39]·7H2O, and titanium dioxide. Although relatively rapid deactivation was observed, the turnover frequency was 3588 h–1 after 20 min, and the turnover number exceeded 4600 after 3 h of light irradiation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.