Thallium water exchange

The B oH o2 anion is best obtained by heating [Et3NH]2[BioHi2] to 160 °C. Its alkali metal salts are soluble in water, while the thallium salt is insoluble. The white alkali metal salts are stable up to 500 °C. Their aqueous solutions react neutral because the corresponding acid is a strong acid. It can be isolated as [H30]2[B1oH1o] (m.p. 202 °C) from its aqueous solutions obtained by ion exchange from the alkali metal salts. 

Reaction of the anion 21 with Cp or Cp metal fragments provides further metallocene-type complexes with a pendant phosphaferrocene side-chain. For example, the reaction of the thallium derivative T1 21 with [Cp RhCl2]2 yields the cationic pentamethylrhodocenium 24 as its chloride (Scheme 1.5.10). This is an interesting species because it is a chiral water-soluble P ligand. The chloride anion can be exchanged by PF,s to make the compound more soluble in organic solvents. 

To a stirred solution of chalcone (5 mmol) in trimethyl orthoformate (20 ml) was added Dowex 50 x 4 cation exchange resin (3 g). After stirring at room temperature for 20 h, the mixture was filtered into a solution of HTI (2.37 g, 6 mmol) in trimethyl orthoformate (10 ml) and kept for 12 h. It was then quenched with 10% aqueous sodium bicarbonate (25 ml) and extracted with dichloromethane. The combined organic layers were washed with water, dried and concentrated the residue was purified by column chromatography on silica gel (benzene), to afford methyl 2,3-diaryl-3-methoxypropanoates in 80-94% yield. This method was better than that reported with thallium (III) nitrate not only because this toxic reagent is avoided but also because yields were considerably higher. 

Almost linear decrease of adsorption capacity has been observed with thallium—sodium zeolites of type A (n = 1.98) for water vapor with an increase of the degree of exchange (Figure 1). This is a result of a decrease of the cation electric field which causes a decrease of the adsorption layer density. 

Using thallium—sodium zeolites of type X (n = 2.30), we observed an increase of adsorption capacity for water vapor and benzene at 38% replacement of sodium ions by thallium ions, and then its decrease with an increase in the degree of exchange. As thallium ions replace sodium ions in the position Sm (25) we may assume redistribution of cations at dehydration under the conditions of high vacuum and thermal treatment at 350°C, and stronger chemical bonds of thallium atoms in screened positions in comparison with sodium atoms. 

Figure 1. Dependence of the number of adsorbed water molecules per unit cell on the degree of exchange of sodium ions by thallium ions at different relative pressures from 0.05 to 0.50...

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