Tetracontatungstotetraarsenate III and Its Cobalt II Complex

The potassium salt of [KAS4W40O, can be obtained by the previous procedure, using a K2WO4 solution prepared by the action of a stoichiometric amount of potassium hydroxide on an aqueous suspension of tungsten(Vl) oxide. 

The compound is an air-stable, white, crystalline solid, soluble in water. Its aqueous solution is stable between pH 4 and 7.5. Its polarogram in 0.5 M tris(hydroxymethyI)aminomethane + 0.5 M NaCl buffer, pH 7.5, obtained with a dropping mercury electrode, shows two waves with half-wave potentials —1.06 and —1.16 V versus SCE. There is a shoulder on the electronic spectrum in the UV region at240nm(c= 1.4-10 M cm ). The 250-MHz WNMR spectrum in H2O-D2O (90 10) solution shows six resonance lines with relative intensities 2 1 2 2 2 1 at = —93.8, — 103.7, - 104.8, — 118.6, — 189.8, and — 196.8 ppm, respectively (reference external 2 M Na2WO4 in alkaline D2O). 

Aqueous 1 M Co(NO)j (5mL, 5 mmol) is added with stirring to a solution of 30 g (2.5 mmol) of the sodium salt of tetracontatungstotetraarsenate 

The material is recrystallized by dissolution in 60mL of lukewarm water. Yield 19 g (70%). 

AMMONIUM SODIUM HENICOSATUNGSTONONA-ANTIMONATE(III), (NH4), g [NaSbgWj lOge] -24H20 

40[W04]2 - + ACHjAsOj] + 28Na + 56H + 28H2O — Na27 [Na As4W4oO,4o]-60H20 

AMMONIUM TETRACONTATUNGSTODICOBALTOTETRA-ARSENATE(III), (NH4)23[NH4As4 V4oO,4o(Co(H20))2] I9H2O 

---