Catalysis Today, Vol.332, 2-10, 2019
Syntheses and characterization of alpha-Keggin- and alpha(2)-Dawson-type diplatinum(II)-coordinated polyoxotungstates: Effects of skeletal structure, internal element, and nitrogen-containing ligand coordinated to the platinum center for hydrogen production from water under light irradiation
The tetramethylammonium and cesium salts of diplatinum(II) complexes composed of mono-lacunary alpha-Kegginand alpha(2)-Dawson-type polyoxotungstates, [(CH3)(4)N](4)H[alpha-AlW11O39{cis-Pt(NH3)(2)}(2)]center dot 11H(2)O (TMA-AlW11-Pt-NH3), [(CH3)(4)N](4)H[alpha-BW11O39{cis-Pt(NH3)(2)}(2)]center dot 9H(2)O (TMA-BW11-Pt-NH3), Cs-4[alpha-GeW11O39{Pt(bpy)}(2)]center dot 10H(2)O (bpy= 2,2'-bipyridine; Cs-GeW11-Pt-bpy), Cs3.5H0.5[alpha-GeW11O39{Pt(phen)}(2)]center dot 3H(2)O (phen= 1,10-phenanthroline; Cs-GeW11-Pt-phen), and Cs-6[alpha(2)-P2W17O61{cis-Pt(NH3)(2)}(2)]center dot 13H(2)O (Cs-P2W17-Pt-NH3), were synthesized and characterized by X-ray crystallography, elemental analysis, TG/DTA, FTIR, and solution {H-1 and P-31} NMR spectroscopy. The characterization results showed that the two platinum(II) moieties, [cis-Pt (NH3)(2)](2+), [Pt(bpy)](2+), and [Pt(phen)](2+), were coordinated to the mono-vacant site of [XW11O39]((12-n))-(Xn+ = Al3+, B3+, and Ge4+) and [alpha(2)-P2W17O61](10-). When the eight platinum(II) compounds, [(CH3)(4)N](3)[alpha-PW11O39{cis-Pt(NH3)(2)}(2)]center dot 10H(2)O (TMA-PW11-Pt-NH3), [(CH3)(4)N](4)[alpha-SiW11O39{cis-Pt(NH3)(2)}(2)]center dot 13H(2)O (TMASiW(11)-Pt-NH3), [(CH3)(4)N](4)[alpha-GeW11O39{cis-Pt(NH3)(2)}(2)]center dot 11H(2)O (TMA-GeW11-Pt-NH3), TMA-AlW11-Pt-NH3, TMA-BW11-Pt-NH3, Cs-GeW11-Pt-bpy, Cs-GeW11-Pt-phen, and Cs-P2W17-Pt-NH3 were used as photocatalysts for hydrogen evolution from aqueous triethanolamine (TEOA) solution under the light irradiation, Cs-P2W17-Pt-NH3 exhibited the highest activities among the eight diplatinum(II) compounds.