Phosphines dithiophosphinic acid

The metal and ammonium salts of dithiophosphinic acids tend to exhibit far greater stability with respect to this thermal decomposition reaction, and consequently these acids are often prepared directly in their salt form for convenience and ease of handling. Alkali-metal dithiophosphinates are accessible from the reaction of diphosphine disulfides with alkali-metal sulfides (Equation 22) or from the reaction of alkali-metal diorganophosphides with two equivalents of elemental sulfur (Equation 23). Alternatively, they can be prepared directly from the parent dithiophosphinic acid on treatment with an alkali-metal hydroxide or alkali-metal organo reagent. Reaction of secondary phosphines with elemental sulfur in dilute ammonia solution gives the dithiophosphinic acid ammonium salts (Equation 24). 

Mono- and disulfur substitutes of diesters of phosphoric acids, phosphonic acids, and phosphinic acids, possessing soft-donor atoms in their structures, present large An(III)/Ln(III) selectivities, especially the dialkyl-dithiophosphinic acid used in the Chinese CYANEX 301 process or its chlorophenyl derivative used in the German ALINA process. 

Cyanex 301 One of the solvent extraction processes, used together with UREX, for separating the components of used nuclear fuel. This process uses a complex phosphinic acid, [bis(2,4,4-trimethylpentyl)dithiophosphinic acid], made by Cytec Industries, Canada. Its purpose is to separate americium, curium, and lanthanide fission products from the other components. 

Figure 88 General diagrams of phosphinic acid, monothiophosphinic acid and dithiophosphinic acid,...

The fact that dithiophosphinic acids show the greatest selectivity for An over Ln " as compared to phosphinic and monothiophosphic acids is due to an increased covalency in the An—S bonds but not necessarily a shorter An—S bond. In addition, trivalent actinides show a thermodynamic preference to form bonds with soft donor atoms. The structural differences observed in the complexes of An with the three ligands studied are due to differences in the hard and soft nature of the oxygen and sulfur atoms, respectively, and their hydrogen-bonding ability."" ... 

Lanthanide-actinide separation has been attempted by NDSX method using diphenyl dithiophosphinic acid derivatives. Geist et al. [48] employed a synergistic mixture of bis(chlorophenyl)-dithiophosphinic acid (BCDTA) and tri-n-octyl phosphine oxide (TOPO) in a hollow-fiber module for the lanthanide-actinide separation. About 99.99% Am(lll) could be extracted by the contactor from 0.5 M nitric acid with about 33% contaminations from lanthanides, namely, Y,... 

FIGURE 5.15 Extraction of base metals as function of pH by (a) CYANIiX 301 (di(2,4,4-trimethylpentyl)dithiophosphinic acid and (b) CYANEX 302 (di(2,4,4-trimethylpentyl)thio-phosphinic acid. (From Sole, K. C. and Cole, P. M. 2001. In Ion exchange and solvent extraction, vol. 15, New York Mareel Dekker. With permission.)... 

The SH stretching vibration in dialkyl dithiophosphoric acids [(R0)2PSSH] absorbs broadly in the liquid state at 2480-2440 cm A band at 865-835 cm is probably due to SH bending. Dithiophosphinic acids (R2PSSH) absorb broadly in the condensed state at 2420-2300 cm due to SH S bonding. In dilute solution the free SH in the above dithiophosphoric and phosphinic acids absorbs sharply" " " at 2590-2550 cm" ... 

Phosphoric, phosphinic, and phosphonic acid. Phosphinic acid-based extractants contain the P(0)0H acid functionality as well as two R groups attached to the phosphorus, where R can be hydrogenic, aliphatic, or aromatic. Sulfur containing derivatives are known as monothiophosphinic acids, where the phosphonyl oxygen is replaced with a sulfur, and dithiophosphinic adds, where both oxygens are replaced with sulfur (Figure 88). 

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