Selective Oxidation of Sulfides to Sulfones by H2O2 Catalyzed by Fe-Substituted Sandwich

Selective oxidation of sulfides to sulfones by H2O2 catalyzed by Fe-substituted sandwich type polyoxometalate

HedayatHaddadi[*]a, MostafaRiahiFarsanib

aDepartment of Chemistry, Faculty of Sciences, Shahrekord University, P.O. Box 115, Shahrekord, Iran

bDepartment of Chemistry, Islamic Azad University, Shahrekord branch, Shahrekord , Iran

Supporting Information

Typical procedure for the oxidation reactions

The oxidation of sulfides was conducted in a 25 mL round bottom flask equipped with a magnetic stirring bar. The typical procedure is as follows: Acetonitril (solvent, 3 mL), TBA salt of catalyst (0.01 mmol), and thioanisole (1 mmol, 0.124 g) were added to the flask continuously. Then, aqueous hydrogen peroxide (30 wt %) was dropwise added within 5 min under stirring. The mixture was sampled periodically and analyzed by GC. After completion of the reaction, the product was extracted with CH2Cl2 and the combined organic layers were dried over anhydrous Na2SO4. The solvent was removed under reduced pressure to give the corresponding pure products.

Catalyst synthesis

Δ-Na8HPW9O34·19H2O, β-Na8[HAsW9O34].11H2O, α-Na10[SiW9O34]·15H2Oand The tetrabutylammonium (TBA) salts [(XW9O34)2M4](n−m)−, (X=P, Si, As and M=MnII, FeIII, CoII, NiII, CuII and ZnII) were prepared and purified by literature methods[1-9].

Na8HPW9O34.24H2O. First 30.0 g of Na2WO4.2H2O was dissolved in 37 mL of distilled water with stirring. Then 0.75 mL of 85% H3PO4, followed by 5.5 mL of glacial acetic acid, was added to the stirring solution. After a few seconds the solution became cloudy and after about 1 min a heavy white precipitate had formed. The solid was collected on a sintered-glass frit and dried under aspiration until easily manipulated.

Kl0[Mn4(H2O)2(PW9O34)2]·20H2O. A 2g of Δ-Na8HPW9O34·19H2O (dried at 140 ºC during 1 h) was slowly added to a solution containing 0.2366 g of MnSO4.H2O in 15 mL of H2O. This orange solution was gently heated, and any insoluble material was removed by warm filtration through paper. Excess solid KCl (5 g) was added to the orange solution resulting in the immediate precipitation of an orange solid, which was collected in a sintered-glass frit and redissolved in H2O. IR (KBr pellet): 1086 (m), 1034 (w), 970(m), 950 (m, sh), 932 (m, sh), 868 (s), 823 (s), 769 (s), 702 (s), .Anal. Calcd for Kl0[Mn4(H2O)2(PW9O34)2]·20H2O: K, 7.24; Mn, 4.07; P, 1.15; W, 61.26. Found(%): K, 7.21; Mn, 4.05; P, 1.16; W, 60.04.

Anal.Calcd for [(CH3CH2CH2CH2)4N]10[Mn4(PW9O34)2]: C, 27.05; H, 5.11; Mn, 3.09; N, 1.97; P, 0.87; W, 46.58. Found(%):C, 27.15; H, 5.16; Mn, 3.12; N, 1.91; P, 0.89; W, 46.01.IR (KBr pellet): 1084 (m), 1032(w), 974 (m), 940 (m, sh), 930 (m, sh), 864 (s), 820 (s), 764 (s), 707 (s).

K10[Zn4(H2O)2(PW9O34)2]·20H2O. Solid ZnC12 (0.19 g, 1.4mmol) was dissolved in 15 mL of water. To this solution was added with stirring 2.0 g of solid Δ-Na8HPW9O34 (1 atm, 140 ºC, 1-2 h). The solution was heated until nearly homogeneous and then filtered hot by gravity filtration through paper. Excess solid KC1 (4-6 g) was added to the clear filtrate, resulting in the immediate precipitation of a white solid. After the mixture was cooled to room temperature, this solid was collected on a sintered-glass frit and dried under aspiration. IR (KBr pellet): 1104 (m), 1032(w), 980 (m), 940 (m, sh), 864 (s), 820 (m). Anal.Calcd K10[Zn4(H2O)2(PW9O34)2]·20H2O: K, 7.18; P, 1.14; W, 60.79; Zn, 4.80 Found(%): 7.17; P, 1.18; W, 61.47; Zn, 4.83.

Anal.Calcd for [(CH3CH2CH2CH2)4N]10[Zn4(PW9O34)2]: C, 26.90; H, 5.08; N, 1.96; P, 0.87; W, 46.31; Zn, 3.66. Found:C, 26.85; H, 5.04; N, 1.92; P, 0.82; W, 45.46; Zn, 3.62.IR (KBr pellet): 1104 (m), 1032(w), 980 (m), 940 (m, sh), 864 (s), 820 (m).

K10[Co4(H2O)2(PW9O34)2].22H2O. Solid Co(NO3)·6H2O (0.41 g, 1.4 mmol) was dissolved in 15 mL of water. To this light pink solution was added with stirring 2.0 g of solid Δ-Na8HPW9O34 (1 atm, 140ºC, 1-2 h). The solution was heated until a homogeneous purple to burgundy solution resulted. Excess solid KC1 (4-6 g) was added, and a blue-purple precipitate formed. After the mixture was cooled to room temperature, this solid was collected on a sintered-glass frit and dried under aspiration. IR (KBr pellet): 1104 (m), 1032(w), 980 (m), 940 (m, sh), 864 (s), 820 (m). Anal.Calcd for K10[Co4(H2O)2(PW9O34)2].22H2O: Co, 4.32; K, 7.17; P, 1.14; W, 60.67. Found(%):Co, 4.36; K, 7.15; P, 1.14; W, 61.18.

Anal.Calcd for [(CH3CH2CH2CH2)4N]10[Co4(PW9O34)2]: C, 26.99; H, 5.10; Co, 3.31; N, 1.97; P, 0.87; W, 46.48. Found:C, 26.95; H, 5.12; Co, 3.36; N, 1.92; P, 0.84; W, 47.11.IR (KBr pellet): 1104 (m), 1032(w), 980 (m), 940 (m, sh), 864 (s), 820 (m).

K6[Fe4(H2O)2(PW9O34)2].15H2O To a solution of ferrous chloride tetrahydrate (FeCl2·4H2O, 0.48 g) in 25mL of H2O was added slowly as a solid 3.0 g of Δ-Na8HPW9O34with vigorous stirring. After the solution was heated to 60 °C for 10min, it was filtered hot through a medium frit. Potassium chloride(3.6 g) was added to precipitate a dark solid. The precipitate was collected and dried under water aspirator vacuum for 1 h. IR (KBr pellet): 1066 (m), 1014 (w), 970(m), 950 (m, sh), 932 (m, sh), 868 (s), 823 (s), 769 (s), 702 (s). Anal.Calcd for K6[Fe4(H2O)2(PW9O34)2].15H2O: Fe, 4.33; K, 4.55; P, 1.20; W, 64.14. Found: Fe, 4.30; K, 4.57; P, 1.21; W, 65.04.

Anal.Calcd for [(CH3CH2CH2CH2)4N]6[Fe4(PW9O34)2]: C, 18.79; H, 3.55; Fe, 3.64; N, 1.37; P, 1.01; W, 53.92. Found: C, 18.73; H, 3.58; Fe, 3.68; N, 1.34; P, 1.03; W, 53.14.IR (KBr pellet, ): 1069(m), 1017 (w), 971 (m), 950 (m, sh), 932 (m, sh), 870 (s), 823 (s), 769 (s), 705 (s).

K6Na4[Ni4(H2O)2(PW9O34)2].24H2O:100 mL of an aqueous solution containing 33 g (100 mmol) of Na2WO4·2H2O and 1.57 g (11 mmol)of Na2HPO4 (pH adjusted to 7.1 with acetic acid) was added a solution of 5.53 g (22 mmol) of Ni(II) acetate in 50 mL H2O. The resulting yellow solution (pH 6.9) was refluxed for 2 hands hot filtered, and then 4g of potassium acetate was added before allowing the solution to cool to room temperature. After several hours, a mixture of chunky small yellow crystals and powder is obtained. IR (KBr pellet): 1106 (m), 1034 (w), 970(m), 950 (m, sh), 935 (m, sh), 873 (s), 823 (s), 769 (s), 705 (s.Anal. Calcd for K6Na4[Ni4(PW9O34)2]:K, 4.35; Na, 1.71; Ni, 4.36; P, 1.15; W, 61.41. Found(%):K, 4.30; Na, 1.73; Ni, 4.39; P, 1.16; W, 60.48.

Anal.Calcdfor [(CH3CH2CH2CH2)4N]10[Ni4(PW9O34)2]: C, 27.00; H, 5.10; N, 1.97; Ni, 3.30; P, 0.87; W, 46.49. Found: C, 27.05; H, 5.12; N, 1.93; Ni, 3.30; P, 0.89; W, 47.1.IR (KBr pellet): 1108 (m), 1038 (w), 970(m), 950 (m, sh), 935 (m, sh), 873 (s), 820 (s), 769 (s), 705 (s).

α-Na10[SiW9O34]·15H2O:Sodium tungstate (1.82 g, 0.55 mol) and sodium metasilicate (1.1 g, 50 mmol) are dissolved in 200mL of hot water. 130 mL of 6 M HCl added dropwise in 30 min to this solution with vigorous stirring. The solution is boiled until the volume is 300mL. Unreacted silica is removed by filtration or by centrifugation. 150 mL of water contain 50gr anhydrous sodium carbonate slowly added to the first solution with gentle stirring. A precipitate forms slowly. It is removed by filtering, using a sintered glass filter, after 1 h. The solid is stirred with 1 L of 4M NaCl solution and filtered again. It is then washed successively with two 100 mL portions of ethanol and l00mL of diethyl ether and dried under vacuum. IR (KBr pellet), 985(w), 940(w), 930(w), 865(br), 848(sh), 808(sh), 712(w).

K11Na1[Co4(H2O)2(SiW9O34)2]·26H2O: To an aqueous solution of Co(NO3)2·6H2O (0.32 g, ∼1.1 mmol) dissolved in 15mL of distilled water, freshly prepared α-Na10[SiW9O34]·15H2O (1.00 g, 0.37 mmol) was added very slowly at room temperature over one hour and the resulting solution was heated to 70–80 °C for half an hour, followed by cooling to room temperature. After cooling, the solution was centrifuged and filtered to remove all possible impurities and unreacted compounds. 5g KCl was then added under stirring and a precipitate was formed immediately. The product was isolated by filtration. Anal.Calcd for.K11Na1[Co4(H2O)2(SiW9O34)2] (%):Co, 4.22; K, 7.70; Na, 0.41; Si, 1.01; W, 59.28. Found (%):Co, 4.20; K, 7.72; Na, 0.41; Si, 1.01; W, 58.48. IR (KBr pellet): 993 (sh), 941 (sh), 888 (br), 796 (br), 708 (br).

Anal.Calcd for [(CH3CH2CH2CH2)4N]12[Co4(SiW9O34)2]: C, 30.35; Co, 3.10; N, 2.21; Si, 0.74; W, 43.55.Found (%):C, 30.31; Co, 3.04; N, 2.23; Si, 0.71; W, 42.21. IR (KBr pellet): 993 (sh), 941 (sh), 887 (br), 798 (br), 711 (br).

K11Na1[Ni4(H2O)2(SiW9O34)2]·27H2O: To an aqueous solution of Ni(NO3)2·6H2O (0.32 g, ∼1.1 mmol) dissolved in 15 mL of distilled water, freshly prepared α-Na10[SiW9O34]·15H2O (1.00 g, 0.37 mmol) was added very slowly at room temperature over 1 h. The resulting solution was heated to 70–80 °C for half an hour and then cooled to room temperature. After cooling, the solution was filtered to remove all possible impurities and unreacted compounds. 5 gKCl was added under stirring, followed by immediate formation of a precipitate. The product was filtered and a light green solid was obtained. Anal.Calcd for. (%):K, 7.68; Na, 0.41; Ni, 4.19; Si, 1.00; W, 59.10. Found (%):K, 7.65; Na, 0.41; Ni, 4.24; Si, 1.01; W, 58.22. IR (KBrpellet ): 985 (m), 941 (sh), 890 (br), 801 (br), 717(s).

Anal.Calcd for [(CH3CH2CH2CH2)4N]12[Ni4(SiW9O34)2]: C, 30.35; N, 2.21; Ni, 3.09; Si, 0.74; W, 43.55. Found (%):C, 30.31; N, 2.23; Ni, 3.12; Si, 0.71; W, 44.15. IR (KBr pellet): 984 (m), 943 (sh), 894 (br), 798 (br), 714(s).

K4Na6Mn[Mn4(H2O)2(SiW9O34)2]·33H2O: A 2.23 g (0.75 mmol) sample of K8[SiW10O36] was added with stirring to a solution of 0.36 g (2.25 mmol) MnCl2.2H2O in 100 mL of a 1.0 M sodium acetate buffer (pH 4.8). This solution was heated to 90 °C for 40 min and then cooled to room temperature. Addition of solid KCl (10 g) led to a yellow product, which was filtered off and air-dried. Anal.Calcd for K4Na6Mn[Mn4(SiW9O34)2]: K, 2.80; Mn, 4.92; Na, 2.47; Si, 1.01; W, 59.21. Found(%):K, 2.81; Mn, 4.94; Na, 2.45; Si, 1.02; W, 58.48. IR(KBr pellet): 983 (w), 949 (s), 902 (vs), 871 (vs), 849 (sh), 754 (vs), 721 (vs).

Anal.Calcd for [(CH3CH2CH2CH2)4N]12[Mn4(SiW9O34)2]: C, 30.41; H, 5.74; Mn, 2.90; N, 2.22; Si, 0.74; W, 43.64. Found(%) C, 31.24; H, 5.78; Mn, 2.93; N, 2.20; Si, 0.75; W, 44.70.IR(KBr pellet): 985 (w), 947 (s), 900 (vs), 874 (vs), 849 (sh), 757 (vs), 724 (vs).

K4Na8[Cu4(H2O)2(SiW9O34)2]·23H2O: A 2.23 g (0.75 mmol) sample of K8[SiW10O36] was added with stirring to a solution of 0.38 g (2.25 mmol) CuCl2.2H2O in 100 mL of a 1.0 M sodium acetate buffer (pH 4.8). This solution was heated to 90 °C for 40 min and then cooled to room temperature. Addition of solid KCl (10 g) led to a yellow product, which was filtered off and air-dried.IR(KBr pellet): 986 (w), 949 (s), 899 (vs), 881 (vs), 849 (sh), 761 (vs), 724 (vs) cm-1. Anal.Calcd for K4Na8[Cu4(H2O)2(SiW9O34)2]·23H2O: Cu, 4.62; K, 2.84; Na, 3.35; Si, 1.02; W, 60.19 .Found: Cu, 4.63; K, 2.95; Na, 3.37; Si, 91; W, 60.61 .

Anal.Calcd for [(CH3CH2CH2CH2)4N]12[Cu4(SiW9O34)2]: C, 30.28; H, 5.72; Cu, 3.34; N, 2.21; Si, 0.74; W, 43.44. Found(%):C, 30.24; H, 5.75; Cu, 3.30; N, 2.20; Si, 0.78; W, 44.14. IR(KBr pellet ): 984 (w), 949 (s), 897 (vs), 880 (vs), 851 (sh), 763 (vs), 728 (vs).

K3Na9[Zn4(H2O)2(SiW9O34)2]·34H2O: A 2.23 g (0.75 mmol) sample of K8[SiW10O36] was added with stirring to a solution of 0.31 g (2.25 mmol) ZnCl2.2H2O in 100 mL of a 1.0 M sodium acetate buffer (pH 4.8). This solution was heated to 90 °C for 40 min and then cooled to room temperature. Addition of solid KCl (10 g) led to a yellow product, which was filtered off and air-dried. IR(KBr pellet): 985 (w), 949 (s), 907 (vs), 894 (vs), 844 (sh), 760(vs), 721 (vs).Anal. Calcd for K3Na9[Zn4(H2O)2(SiW9O34)2]·34H2O: K, 2.06; Na, 3.64; W, 58.18; Zn, 4.60; Si, 0.99. Found: K, 2.01; Na, 3.62; W, 58.10; Zn, 4.34; Si, 1.11.

Anal.Calcd for [(CH3CH2CH2CH2)4N]12[Zn4(SiW9O34)2]: C, 30.25; H, 5.71; N, 2.20; Si, 0.74; W, 43.40; Zn, 3.43. Found: C, 30.20; H, 5.75; N, 2.22; Si, 0.64; W, 44.10; Zn, 3.45. IR(KBr pellet): 984(w), 948 (s), 906 (vs), 897 (vs), 842 (sh), 761(vs), 721 (vs.

Anal.Calcd for [(CH3CH2CH2CH2)4N]10[Ni4(AsW9O34)2]:C, 26.67; H, 5.04; As, 2.08; N, 1.94; Ni, 3.26; W, 45.92. Found(%):C, 26.61; H, 5.00; As, 2.11; N, 1.91; Ni, 3.29; W, 46.26. (KBr pellet, 1300-400cm−1 ): 941 (m), 870 (br), 831 (br), 734(s).

K8Na2[Mn4(H2O)2(AsW9O34)2].18H2O: Solid MnCl2·4H2O(0.30 g, 1.5 mmol) was dissolved in 15 mL of water. To this solution was added with stirring 2.0 g (0.75 mmol) of solid β-Na8HAsW9O34 (1atm, 140 oC,1-2 h). The solution was heated until nearly homogeneous and then filtered hot by gravity filtration through paper. Excess solid KCl (4.5 g) was added to the clear filtrate, resulting in the immediate precipitation of a orange solid. After the mixture was cooled to room temperature, this solid was collected on a sintered-glass frit and dried under aspiration. Anal.Calcd for K8Na2[Mn4(H2O)2(AsW9O34)2].18H2O: As, 2.73; K, 5.70; Mn, 4.01; Na, 0.84; W, 60.32. Found(%):As, 2.70; K, 5.71; Mn, 4.08; Na, 0.87; W, 61.02. (KBrpellet ): 945 (m), 874 (br), 835 (br), 737(s).

Anal.Calcd for [(CH3CH2CH2CH2)4N]10[Mn4(AsW9O34)2]: C, 26.72; H, 5.05; As, 2.08; Mn, 3.06; N, 1.95; W, 46.02. Found(%):C, 26.62; H, 5.09; As, 2.13; Mn, 3.10; N, 1.90; W, 45.12. IR (KBr pellet): 947 (m), 877 (br), 837 (br), 734(s).

K7Na3[Fe4(H2O)2(AsW9O34)2].18H2O: Solid FeSO4·7H2O(0.42 g, 1.5 mmol) was dissolved in 15 mL of water. To this solution was added with stirring 2.0 g ( 0.75mmol ) of solid β-Na8HAsW9O34(1atm, 140 oC,1-2 h). The solution was heated until nearly homogeneous and then filtered hot by gravity filtration through paper. Excess solid KCl (4.5 g) was added to the clear filtrate, resulting in the immediate precipitation of a brown solid. After the mixture was cooled to room temperature, this solid was collected on a sintered-glass frit and dried under aspiration..Anal.Calcd for K7Na3[Fe4(H2O)2(AsW9O34)2].18H2O: As, 2.74; Fe, 4.08; K, 5.00; Na, 1.26; W, 60.46. Found: As, 2.70; Fe, 4.12; K, 5.08; Na, 1.27; W, 61.14. IR (KBr pellet): 940 (m), 878 (br), 840 (br), 739(s).

Anal.Calcd for [(CH3CH2CH2CH2)4N]10[Fe4(AsW9O34)2]: C, 26.71; H, 5.04; As, 2.08; Fe, 3.10; N, 1.95; O, 15.12; W, 45.99. Found(%):C, 26.65; H, 5.09; As, 2.05; Fe, 3.14; N, 1.98; W, 45.09.

IR (KBr pellet): 942 (m), 880 (br), 842 (br), 741(s).

K8Na2[Co4(H2O)2(AsW9O34)2].18H2O: Solid Co(NO3 )2· 6H2O(0.45g, 1.5 mmol) was dissolved in 15 mL of water. To this light pink solution was added with stirring 2.0 g ( 0.75mmol ) of solid β-Na8HAsW9O34(1atm, 140 oC,1-2 h). The solution was heated until a homogeneous purple to burgundy solution resulted. Excess solid KCl (5.0 g) was added , and a blue-purple precipitate formed. After the mixture was cooled to room temperature, this solid was collected on a sintered-glass frit and dried under aspiration. Anal.Calcdfor K8Na2[Co4(H2O)2(AsW9O34)2].18H2O:As, 2.72; Co, 4.28 K, 5.69; Na, 0.84; W, 60.15 . Found(%):As, 2.77; Co, 4.21 K, 5.54; Na, 0.81; W, 61.01. (KBr pellet): 941 (m), 874 (br), 835 (br), 735(s).

Anal.Calcd for [(CH3CH2CH2CH2)4N]10[Co4(AsW9O34)2]: C, 26.66; H, 5.03; As, 2.08; Co, 3.27; N, 1.94; W, 45.91. Found: C, 26.50; H, 5.08; As, 2.12; Co, 3.30; N, 1.90; W, 44.61. (KBr pellet): 940 (m), 871 (br), 833 (br), 737(s).

K10[Ni4(H2O)2(AsW9O34)2].20H2O: Solid NiCl2·6H2O(0.37 g, 1.5 mmol) was dissolved in 15 mL of water. To this solution was added with stirring 2.0 g ( 0.75mmol ) of solid β-Na8HAsW9O34(1atm, 140 oC,1-2 h). The solution was stirred at room temperature until all the B-AsW9 was dissolved. Excess solid KCl (4.5 g) was added to the yellow-green solution, resulting in the immediate precipitation of a yellow solid. This solid was collected on a sintered-glass frit and dried under aspiration. Anal.Calcd for K10[Ni4(H2O)2(AsW9O34)2].20H2O: As, 2.71; Co, 2.14; K, 5.67; Na, 0.83; Ni, 2.13; W, 59.96. Found(%):K, 6.90; As, 3.02; W, 55.70; Ni, 4.17; . (KBr pellet): 942 (m), 874 (br), 833 (br), 735(s)..

K8Na2[Cu4(H2O)2(AsW9O34)2].32H2O: Solid CuCl2·2H2O(0.26 g, 1.5 mmol) was dissolved in 15 mL of water. To this solution was added with stirring 2.0 g (0.75 mmol ) of solid β-Na8HAsW9O34(1atm, 140 oC,1-2 h). The solution was stirred at room temperature until all the B-AsW9 was dissolved. Excess solid KCl (4.5 g) was added to the light green solution, resulting in the precipitation of a pale green solid. This solid was collected on a sintered-glass frit and dried under aspiration. Anal.Calcd for K8Na2[Cu4(H2O)2(AsW9O34)2].32H2O: As, 2.60; Cu, 4.40; K, 5.42; Na, 0.80; W, 57.33. Found(%): As, 2.63; Cu, 4.44; K, 5.40; Na, 0.82; W, 56.66. (KBrpellet): 940(m), 870(br), 830(br), 736(s). Anal.Calcd for [(CH3CH2CH2CH2)4N]10[Cu4(AsW9O34)2]: C, 26.60; H, 5.02; As, 2.07; Cu, 3.52; N, 1.94; W, 45.80. Found: C, 26.57; H, 4.95; As, 2.10; Cu, 3.48; N, 1.90; W, 46.20 (KBr pellet): 941 (m), 868 (br), 829 (br), 739(s).

K8Na2[Zn4(H2O)2(AsW9O34)2].20H2O. Solid ZnCl2 (0.21 g, 1.5 mmol) was dissolved in 15 mL of water. To this solution was added with stirring 2.0 g ( 0.75mmol ) of solid β-Na8HAsW9O34(1atm, 140 oC,1-2 h). The solution was heated until nearly homogeneous and then filtered hot by gravity filtration through paper. Excess solid KCl (4.5 g) was added to the clear filtrate, resulting in the immediate precipitation of a white solid. After the mixture was cooled to room temperature, this solid was collected on a sintered-glass frit and dried under aspiration. Anal.Calcd for K8Na2[Zn4(H2O)2(AsW9O34)2].20H2O: As, 2.69; K, 5.62; Na, 0.83; W, 59.48; Zn, 4.70. Found(%):As, 2.67; K, 5.50; Na, 0.80; W, 58.67; Zn, 4.77. (KBr pellet): 943 (m), 872 (br), 833 (br), 733(s).

Anal.Calcd for [(CH3CH2CH2CH2)4N]10[Zn4(AsW9O34)2]: C, 26.57; H, 5.02; As, 2.07; N, 1.94; W, 45.75; Zn, 3.62. Found(%): C, 26.51; H, 5.08; As, 2.11; N, 1.90; W, 46.54; Zn, 3.68. (KBr pellet): 944 (m), 871 (br), 831 (br), 729(s).

Synthesis of TBAn[M4(XW9O34)2] (X=P, Si and As, M = Co2+, Ni2+, Zn2+, Mn2+ and Fe3+):The tetra-n-butylammonium (TBA) salts of these compounds were prepared by a metathesis reaction. To 0.1 mmol of KxNay[M4(XW9O34)2] (X=P, Si and As, M = Co2+, Ni2+, Zn2+, Mn2+ and Fe3+) salts in 30 mL H2O, 10 mmol of tetra-n-butylammoniumbromidewas added with stirring.CH2Cl2(250 mL) was added to this cloudy solution, and the mixture was shaken in a separatory funnel. After standing for 30 min, the mixture separated into a cloudy colorless upper layer and a clear yellow lower layer. The bottom organic layer was collected and concentrated to a thick oil with a rotary evaporator. A yellow solid was then precipitated from the concentrated organic layer by addition of diethyl ether (100 mL). The resulting solid was collected on a medium frit and dried under vacuum for 24 h (yield 80%). IR, CHNS and ICP analyses establish that product have not changed during the counter-ions exchange[4].

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