Author(s)

Chika Nozaki Kato^1,2*, Shunsaku Suzuki¹, Yuki Ihara¹, Koki Aono¹, Rie Yamashita³, Keisuke Kikuchi³, Tetsuji Okamoto³, Hidemitsu Uno⁴

¹Department of Chemistry, Shizuoka University, Shizuoka, Japan.
²Green Chemistry Research Division, Research Institute of Green Science and Technology, Shizuoka University, Shizuoka, Japan.
³Industrial Research Institute of Shizuoka Prefecture, Shizuoka, Japan.
⁴Department of Chemistry and Biology, Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan.

The tetramethylammonium salts of diplatinum(II) complexes composed of mono-lacunary Keggin-type silico and germanotungstates, [(CH₃)₄N]₄[α-SiW₁₁O₃₉{cis-Pt(NH₃)₂}₂]·13H₂O (TMA-Si-Pt) and [(CH₃)₄N]₄[α-GeW₁₁O₃₉{cis-Pt(NH₃)₂}₂]·11H₂O (TMA-Ge-Pt), were synthesized and crystallized. Single crystals of a tetramethylammonium salt of Keggin-type diplatinum(II)-coordinated phosphotungstate [(CH₃)₄N]₃[α-PW₁₁O₃₉{cis-Pt(NH₃)₂}₂]×10H₂O (TMA-P-Pt) were also obtained. The X-ray structural analyses revealed that the two cis-platinum(II) moieties, [cis-Pt(NH₃)₂]²⁺, were each coordinated to two oxygen atoms in a mono-vacant site of [XW₁₁O₃₉]^(12-n)- (Xⁿ⁺ = Si⁴⁺, Ge⁴⁺, P⁵⁺). FTIR spectra of TMA-Si-Pt and TMA-Ge-Pt also suggested that the two platinum(II) moieties were coordinated to the vacant site of [SiW₁₁O₃₉]^8- and [GeW₁₁O₃₉]^8-. The ¹H NMR spectra in DMSO-d₆ of TMA-Si-Pt and TMA-Ge-Pt showed signals assigned to the two sets of NH₃ ligands coordinated to the platinum sites. These three platinum compounds showed hydrogen evolution from aqueous triethanolamine solution under visible light irradiation (λ ≥ 400 nm) in the presence of eosin Y, α-Keggin mono-aluminum-substituted silicotungstate, and titanium dioxide. The catalytic activities were influenced by the central atoms, and TMA-P-Pt showed the highest activities among the three platinum compounds.

Polyoxometalates, Diplatinum(II) Complex, Hydrogen Evolution, Visible Light, X-Ray Crystallography

Kato, C. , Suzuki, S. , Ihara, Y. , Aono, K. , Yamashita, R. , Kikuchi, K. , Okamoto, T. and Uno, H. (2016) Hydrogen Evolution from Water under Visible-Light Irradiation Using Keggin-Type Platinum(II)-Coordinated Phospho-, Silico-, and Germanotungstates as Co-Catalysts. Modern Research in Catalysis, 5, 103-129. doi: 10.4236/mrc.2016.54010.