The sodium potassium citrato oxotungstate(VI) dimer, Na 4K 2〔W 2O 5\|(cit) 2〕·11H 2O (H 4cit = citric acid) was obtained by the reaction of sodium tungstate(VI) and excess potassium citrate monobasic (KH 3cit) ...The sodium potassium citrato oxotungstate(VI) dimer, Na 4K 2〔W 2O 5\|(cit) 2〕·11H 2O (H 4cit = citric acid) was obtained by the reaction of sodium tungstate(VI) and excess potassium citrate monobasic (KH 3cit) in neutral solution. The crystal data for the title compound: monoclinic, C 12 H 30 K 2Na 4W 2O 30 , M r =1192.21, space group P2 1/n, a=17.427(4), b=10.022(2), c=18.637(3) , β=92.62(1)°, V=3252(2) 3, Z=4, D c =2.435 g/cm 3, μ( Mo Kα )=76.38 cm -1 , F( 000)=2288. The structure was refined to R =0.0434 for 6327 independent observed reflections with I>3σ(I) . The complex anion contains a quasi centrosymmetric (O 2W)O b(WO 2) core with a bent bridging oxo group 〔W-O b-W 175.0(4)°〕. Each citrate as tridentate ligand coordinates to a tungsten atom through the alkoxy, α carboxyl, and one β carboxyl group, while the other β carboxyl group remains uncoordinated. Principal dimensions are: W-O b 1.883(6) , (W=O t)av 1.715(6) , W-O (alkoxy) 1.959(6) , W-O ( α carboxy) 2.176(6) and W-O ( β carboxy) 2.231(6) . The tungsten atom is located in a distorted octahedron environment.展开更多
The active sites of samarium orthovanadate(SmVO_(4))were studied by means of ESR,NO TPD and temperature programmed ^(18) O_(2) isotope exchange(TPIE)methods.The results of ESR and NO TPD confirm the presence of V ^(4+...The active sites of samarium orthovanadate(SmVO_(4))were studied by means of ESR,NO TPD and temperature programmed ^(18) O_(2) isotope exchange(TPIE)methods.The results of ESR and NO TPD confirm the presence of V ^(4+) in the catalyst.The TPIE revealed that the ^(18)O_(2) isotope exchange was carried out through a single exchange procedure.The V^(4+)species associated with oxygen vacancies are the sites for O_(2) activation.展开更多
文摘The sodium potassium citrato oxotungstate(VI) dimer, Na 4K 2〔W 2O 5\|(cit) 2〕·11H 2O (H 4cit = citric acid) was obtained by the reaction of sodium tungstate(VI) and excess potassium citrate monobasic (KH 3cit) in neutral solution. The crystal data for the title compound: monoclinic, C 12 H 30 K 2Na 4W 2O 30 , M r =1192.21, space group P2 1/n, a=17.427(4), b=10.022(2), c=18.637(3) , β=92.62(1)°, V=3252(2) 3, Z=4, D c =2.435 g/cm 3, μ( Mo Kα )=76.38 cm -1 , F( 000)=2288. The structure was refined to R =0.0434 for 6327 independent observed reflections with I>3σ(I) . The complex anion contains a quasi centrosymmetric (O 2W)O b(WO 2) core with a bent bridging oxo group 〔W-O b-W 175.0(4)°〕. Each citrate as tridentate ligand coordinates to a tungsten atom through the alkoxy, α carboxyl, and one β carboxyl group, while the other β carboxyl group remains uncoordinated. Principal dimensions are: W-O b 1.883(6) , (W=O t)av 1.715(6) , W-O (alkoxy) 1.959(6) , W-O ( α carboxy) 2.176(6) and W-O ( β carboxy) 2.231(6) . The tungsten atom is located in a distorted octahedron environment.
文摘The active sites of samarium orthovanadate(SmVO_(4))were studied by means of ESR,NO TPD and temperature programmed ^(18) O_(2) isotope exchange(TPIE)methods.The results of ESR and NO TPD confirm the presence of V ^(4+) in the catalyst.The TPIE revealed that the ^(18)O_(2) isotope exchange was carried out through a single exchange procedure.The V^(4+)species associated with oxygen vacancies are the sites for O_(2) activation.
