TUNGSTOVANADATEHETEROPOLY COMPLEXES Inorganic Chemistry, Vol. 10, No. 12, 1971 2745 Then, assuming that the difference is also reflected in line widths were somewhat broader than those of the Tze,much broader epr lines are expected for the mono- VO(H20)42+spectrum. That observation is compatible chloro species, which would be difficult to detect in the with a decreased re relative to that of the aquo complex, presence of the sharper spectrum of VO(H20)2C12. but a much more detailed investigation of the relaxa- The liquid solution epr spectra for a number of tion processes would be necessary for quantitative HC1 concentrations were also observed in this labora- comparison. tory. The intensity of the spectrum attributed to VO (H~0)4~+appeared to follow qualitatively the rela- Acknowledgments.-We are indebted to Dr. W. tive concentrations indicated in Tables I1 and I11 and Burton Lewis and others for helpful comments during Figure 4. However, no attempt was made to do an discussions of the work reported here. We also wish absolute spin count. In 12 M HC1 solution the (g) to thank Dr. B. B. McInteer and Mr. R. M. Potter of and (A) values obtained corresponded well with the Los Alamos Scientific Laboratory for supplying those reported by Kon and Sharpless and the observed the enriched "'0. CONTRIBUTIONFROM THE DEPARTMENTOF CHEMISTRY, GEORGETOWNUNIVERSITY, WASHINGTON, D. C. 20007 Tungstovanadate Heteropoly Complexes. 11. Products of Acidification of v2w&lg4- BY C. M. FLY", JR., AND M. T. POPE* Receiz'ed April 30, 1971 Acidification of solutions of VzW40104- is an efficient means of preparing the red complex V~WQO~O~-,isolated as K, "4, Na, N(CH3)4, C(NHZ)~,and C~H~(NH~)Zsalts. This complex is the same as that previously formula- ted as V~W7031~-. This complex is most stable at pH near 3. At pH 5 it is converted to VZW~O~Q~-and isopolytungstate. On acidification it does not give an oxide precipitate; the free acid can be extracted with ether. Infrared data, elemental analyses, chemical behavior, and comparisons with metatungstate lead to proposal of a Keggin structure V(WoV3)040~-for the complex. At least three other complexes are formed on acidification of VZW~O~~~-;one of these has been isolated as orange-red KeVsWloO4o .20H20. It appears to have a Keggin structure V(WIOVZ)O~O~-. Introduction Sodium metatungstate was prepared by Pope and Varga4 As part of our investigations on tungstovanadate according to Freedman's meth~d.~ The preparation of other reagents not obtained commercially heteropoly complexes,2 we have obtained at least four has been described.z products on acidification of salts of VZW~O~~~-in the Guanidinium Metatungstate.-A solution of 0.5 mmol of pH range 0-3. One of these products has been isolated sodium metatungstate in 20 ml of hot water was treated with a as potassium, ammonium, sodium, and organic cation solul ion of 3 mmol of guanidinium chloride in 3 ml of water. The salts; their analyses all agree with the composition mixture was reheated and allowed to cool. A nearly white powder separated on cooling. It was filtered off, washed with M'~V4Wg040 nH2O. These salts evidently contain water followed by 95y0 ethanol, and air dried. Anal. Calcd the same anion as some prepared, e.g., by Rosenheim for (CN~HE)E(HZW~ZO~O).~HSO:C, 2.08; H, 1.28. Found: C, and Pieck3 which, however, they formulated as (modern 2.30; €1, 1.40. notation) M'6V3W7031-nHz0. Our characterization of Tetramethylammonium Metatungstate.-A solution of 0.5 these compounds, presented here, leads to a structure mmol of the sodium salt in 5 ml of water was treated with a solu- tion of 6 mmol (0.7 g) of tetramethylammonium chloride in 3 ml proposal based on a 12-tungstometalate (Keggin) of water. The resulting white precipitate was isolated and re- constitution. Only one of the other products has been crystallized from water containing 1 mmol of tetramethylam- successfully purified. It has been isolated as monium chloride by room-temperature evaporation. Colorless KsVaW10040.20H~0and appears also to possess a (very pale yellow in bulk) six-sided tablets or blocks (parallel extinction, optically biaxial) were obtained. They were iso- Keggin structure. lated by washing with water-ethanol and 95y0 ethanol and air Experimental Section drying. The crystals were stored over sodium sulfate deca- Ammonium paratungstate was prepared by reaction of WO3. hydrate, since they are efflorescent in a dry atmosphere. Anal. HzO with excess NHaOH in aqueous solution. After all the solid Calcd for [N(CH~)~]P,[H~W~ZO~~].10H~0: C, 8.30; H, 2.73; had reacted and dissolved, the solution was evaporated at 80- W, 63.4. Found: C, 8.41; H, 2.70; W (by ignition to 600"), 90'. Ammonium hydroxide was added at intervals to keep the 63.4. p€I in the range 5-7. The white slightly soluble product which Salts of the 9-Tungsto-4-vanadate(V) Anion, M '8v4w~040.n- separated was collected on a Biichner funnel, washed with small HzO (M' = Univalent Cation). (a) Potassium Salt.-A portions of hot water, and air dried. Anal. Calcd for ("4)10- solution of 50 mmol of K4V2W4019was prepared from stoichio- metric quantities of KICO~,\'%Ob, and WO~.HZO.~The solution (HZWIZO~Z).~H~O:"4, 5.76; W, 70.43. Found: "4, 5.72, 5.74; W (by ignition to 600°), 70.67, 70.74. was diluted to about 200 ml and treated with a solution of 70 mmol (9.5 g) of KHSO4 in 50 ml of water. There was little or (1) Presented as part of Paper IN-10 at the Sixth Middle Atlantic Re- no immediate visible change. The mixture was heated and gional Meeting of the American Chemical Society, Baltimore, Md., Feb 3-5, stirred at about 80' for 4 hr, during which time it became red and 1971. ___~ (2) C. M. Flynn, Jr., and M. T. Pope, Inovg. Chem., 10, 2524 (1971). (4) M. T. Pope and G. M. Varga, Jr.,Inorg. Chem., 6, 1249 (1966). (3) A. Kosenheim and M. Pieck, Z.Anovg. Allg. Chem.,98, 223 (1916). (5) M. L. Freedman, J.Amy. Chem. Soc., 81, 3834 (1959). 2'746 Inorganic Chemistry, Vol. 10, No. 12, 1971 c. &#I.FLYNN,JR., AND >I.T. POPE TABLEI ANALYSES OF TUNGSTOVAKADATES 7-- yo Compound V w Cation H W/V Cation/%' KbV8Wi031' 19H20 Calcd 6.18 52.0 7,90d 1,54 KeVdWoOio. 24H20 Calcd 6.44 52.3 7.41d 1.52 FW 3165,4 Foundn 6.43 (2) 51.9 (2) 7.40 (2)d 1.49 (1) 2 24 0 670 (NHj)jV3\r~7031.18.5HzO Calcd 6.48 54.6 3. 2.45 (NH~)~V~WBO~O* 22H20 Calcd 6.79 551 3. 606 2.29 FW 3003.0 Found 6.64 55.1 (1) 3.56 (2)e 2.30b 2 29 0 660 p\Ta6V4W~040~15Hz0 Calcd 6.87 55.8 1.02 FW 2966.5 Found 6.96 56.7 1.04 (1) 2 26 [K(CHs)a]6V4WsOto. 3H20 Calcd 6 80 55.2 9.62i 2.62 FW 2997,3 Found 6.85 (1) 55 2 (1) 8.68i 2 50 2 24 0 603 [C(NH2)3]sVaWo040. 4H20 Calcd 6.96 56.5 2.46f 1.51 FW 2930.9 Found 6.88 56.3 2 49J 1 50 2 27 0 677 [C~H~(XH~)~I~Y~W~O~O~12H20 Calcd 7.03 57.0 2.49J 1.87 FW 2900.9 Found 6.95 57.3 2.60i 1.88 2 28 0 695 KbVaWioOio. 20H20 Calcd 4.79 57.7 6.13a 1.26 FW 3187.1 Found 4.80 57,8 6.54d 1 17c 3 33 0 532 a Material balance 99.1%,. By ignition to 600'. allowing for (SH4)zO. By difference, K. e SHn. c. deposited a red-brown precipitate (T'p06). The mixture was (c) Sodium Salt.-Potassium g-tungsto-4-vanadate(~~lhy- finally filtered to remove the T'zOj, giving an orange-red solution. drate (16 g, 5.0 mmol) was dissolved in 50 ml of warm water. (The VzOj was isolated and dissolved in dilute sodium hydroxide, The solution was passed through a 20 X 400 cm column of Dowel: and an aliquot was taken for analysis. The amount of vana- 50TV-X8 (Sa-). A spot test on the eluted solution with sodium dium recovered as oxide was thus found to be 12 mmol.) tetraphenylborate showed complete removal of potassium. The The filtrate was evaporated at room temperature or with solution was evaporated to dryness over calcium chloride, giving heating to crystallize the products fractionally. The principal 14.1 g of rust-colored powder. products were leaflets with brass luster and large scarlet to cherry (d'l Other Salts.-These were prepared by metathesis with red cuboctahedral crystals. Other products, obtained in the the potassium salt, A solution of 1 mmol (3.2 g) of potassium later crops of crystals, were red rhombohedra and sometimes 9-tungsto-4-vanadate(V) in 10 ml of 0.1 F HOICCH2C1-0.1 F bright reddish orange rods and potassium sulfate. The desired IiOzCCH2C1 was treated with 12 mmol of hlCl in 6 ml of water cuboctahedral crystals of K6V4&'g010 24H20 were separated (M = guanidinium, tetramethylammonium, or '/%(ethylenedi- mechanically from the other phases and recrystallized by room- ammonium)). Much precipitate (initially oil \yith the ethylene- temperature evaporation from about 200 ml of water containing diamrnonium salt) formed in each case.