Syntheses and characterization of α-Keggin- and α 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

Abstract The tetramethylammonium and cesium salts of diplatinum(II) complexes composed of mono-lacunary α-Keggin- and α 2 -Dawson-type polyoxotungstates, [(CH 3 ) 4 N] 4 H[α-AlW 11 O 39 { cis -Pt(NH 3 ) 2 } 2 ]⋅11H 2 O ( TMA-AlW 11 -Pt-NH 3 ), [(CH 3 ) 4 N] 4 H[α-BW 11 O 39 { cis -Pt(NH 3 ) 2 } 2 ]⋅9H 2 O ( TMA-BW 11 -Pt-NH 3 ), Cs 4 [α-GeW 11 O 39 {Pt(bpy)} 2 ]⋅10H 2 O (bpy = 2,2′-bipyridine; Cs-GeW 11 -Pt-bpy ), Cs 3.5 H 0.5 [α-GeW 11 O 39 {Pt(phen)} 2 ]⋅3H 2 O (phen = 1,10-phenanthroline; Cs-GeW 11 -Pt-phen ), and Cs 6 [α 2 -P 2 W 17 O 61 { cis -Pt(NH 3 ) 2 } 2 ]⋅13H 2 O ( Cs-P 2 W 17 -Pt-NH 3 ), were synthesized and characterized by X-ray crystallography, elemental analysis, TG/DTA, FTIR, and solution { 1 H and 31 P} NMR spectroscopy. The characterization results showed that the two platinum(II) moieties, [ cis -Pt(NH 3 ) 2 ] 2+ , [Pt(bpy)] 2+ , and [Pt(phen)] 2+ , were coordinated to the mono-vacant site of [XW 11 O 39 ] (12− n )− (X n + = Al 3+ , B 3+ , and Ge 4+ ) and [α 2 -P 2 W 17 O 61 ] 10− . When the eight platinum(II) compounds, [(CH 3 ) 4 N] 3 [α-PW 11 O 39 { cis -Pt(NH 3 ) 2 } 2 ]⋅10H 2 O ( TMA-PW 11 -Pt-NH 3 ), [(CH 3 ) 4 N] 4 [α-SiW 11 O 39 { cis -Pt(NH 3 ) 2 } 2 ]·13H 2 O ( TMA-SiW 11 -Pt-NH 3 ), [(CH 3 ) 4 N] 4 [α-GeW 11 O 39 { cis -Pt(NH 3 ) 2 } 2 ]·11H 2 O ( TMA-GeW 11 -Pt-NH 3 ), TMA-AlW 11 -Pt-NH 3 , TMA-BW 11 -Pt-NH 3 , Cs-GeW 11 -Pt-bpy , Cs-GeW 11 -Pt-phen , and Cs-P 2 W 17 -Pt-NH 3 were used as photocatalysts for hydrogen evolution from aqueous triethanolamine (TEOA) solution under the light irradiation, Cs-P 2 W 17 -Pt-NH 3 exhibited the highest activities among the eight diplatinum(II) compounds.