Dithiophosphinic acid

Singh, R. Khwaja, A. R. Gupta, B. Tandon, S. N. Extraction and separation of nickel(II) using bis(2,4,4-trimethylpentyl) dithiophosphinic acid (Cyanex 301) and its recovery from spent catalyst and electroplating bath residue. Solvent Extr. Ion Exch. 1999, 17, 367-390. 

Numerous methods have been used for the synthesis of R2P(S)-S -P(S)R2 compounds. However, probably the most convenient and generally applicable for a range of alkyl, aryl, alkoxy and aryloxy R substituents is the reaction of alkali metal dithiophosphinates with thiophosphinic bromides for n = 1 (Equation 11), or the oxidation of dithiophosphinic acids or their alkali metal salts with I2, SC12 or S2C12 for n = 2, 3 or 4 respectively (Equations 12-14).1,34... 

Numerous preparative methods have been reported for these acids and their salts and ester derivatives.1 4 Dithiophosphoric acids are accessible from the reaction of phosphorus pentasulfide with alcohols or phenols (Equation 18). Dithiophosphinic acids can be prepared from thiophosphinic chlorides and sodium hydrosulfide (Equation 19), although the phenyl derivative is better prepared using a modified Friedel-Crafts reaction in which phosphorus pentasulfide is reacted with benzene in the presence of anhydrous aluminium trichloride (Equation 20). 

Dithiophosphoric and dithiophosphinic acids are strong acids, with pKa values typically in the range 1-2 (in water or alcohol solutions).1 Dithiophosphinic acids are predominately thermally unstable compounds, and tend to undergo a condensation reaction with elimination of H2S on storage at room temperature (Equation 21). Although dithiophosphoric acids can also undergo a similar decomposition reaction, higher temperatures are usually required (>120°C). 

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). 

Trithiophosphonic acids (RPS3H2) are thermally unstable compounds, undergoing decomposition reactions at temperatures sometimes as low as — 10°C depending upon the electronic and steric properties of the R substituent. Decomposition usually occurs via a condensation reaction (similar to that observed for dithiophosphinic acids - Equation 21) to give the di-thiadiphosphatene disulfide and eliminate H2S (Equation 35).48 Similar to dithiophosphinic acids, their metal and ammonium salts are far more thermally stable and are therefore the preferred synthetic target in most cases. 

Dithiophosphoric and dithiophosphinic acids can also react with organic compounds containing multiple carbon-nitrogen bonds, often under very mild conditions, to give thioamides and other related compounds (e.g., Equation 82).163... 

Phosphor-1,1-dithiolates comprise ligands derived from dithiophosphoric acid 0,0-dithioesters (further called simply dithiophosphates), dithiophosphinic acids (dithiophosphinates), and the hybrid dithiophosphonic acid O-monoes-ters (dithiophosphonates) (Scheme 1). 

Although silver is not treated by solvent extraction in any of the flow sheets, silver is recovered from aqueous solution in several other situations. For these processes, Cytec developed reagents with donor sulfur atoms to extract this soft element. For example, tri-isobutylphosphine sulfide (CYANEX 47IX) extracts silver from chloride, nitrate, or sulfate media selectively from copper, lead, and zinc [32]. The silver is recovered from the loaded organic phase by stripping with sodium thiosulfate, and the metal recovered by cementation or electrolysis. Silver can also be extracted from chloride solution by a dithiophosphinic acid (CYANEX 301) [33]. 

Cavell, R. G., Sanger, A. R. Metal complexes with substituted dithiophosphinic acids. 

Using a typical poly (vinyl chloride) (PVC)-based membrane with different ionophores - Zn-bis(2,4,4-trimethylpen-tyl) dithiophosphinic acid complex [450], protoporphyrin IX dimethyl ester [451], porphyrin derivative [452] and hemato-porphyrin IX [453], tetra(2-aminophenyl) porphyrin [454], cryptands [455, 456], 12-crown-4 [457], benzo-substituted macro-cyclic diamide [458], 5,6,14,15-dibenzo-l, 4-dioxa-8,l 2, diazacyclopentadecane-5,14-diene [459], and (A-[(ethyl-l-pyrrolidinyl-2 -methyl) ] methoxy-2-sulfamoyl-5 -benza-mide [460] - the sensors for zinc ions were prepared and investigated. The armed macrocycle, 5,7,7,12,14,14-hexamethyl-1,4,8,11 -tetraazacyclo tetradeca-4,11 -diene dihydrogen perchlorate was used for the preparation of polystyrene-based Zn(II)-sensitive electrode [461]. 

Bis(dialkyldithiophosphinato)nickel(II) complexes were prepared by the direct synthesis of an alkali metal or ammonium salt of the dithiophosphinic acid and a nickel salt in aqueous solution.2039,2061"2063 Ni(S2AsR2)2 and Ni(Se2PR2)2 complexes were prepared in a similar way.2064"2066 All of these complexes are square planar like their dithiophosphate analogues. X-Ray crystal structures of the complexes Ni(S2PR2)2, with R = Me,2067 Et, Ph,1983 R2 = Me/ Et 2°w r2 = Me/2-thienyl,2069 and Ni(Se2PPh2)21984 have been reported (Table 90). 

Sulfur donors of the dithiophosphinic acid type. In 1994, Jarvinen et al of Los Alamos National Laboratory (LANL) et al. reported significantly large separation... 

Jarvinen, G., Barrans, R., Schroeder, N. et al. 1994. Selective extraction of trivalent actinides from lanthanides with dithiophosphinic acids and tributylphosphate. American Chemical Society, San Diego, CA, March. LA-lJR-94-4350. 

Chen, J., Jiao, R., Zhu, Y. 1997. A cross-flow hot test for separating Am from fission product lanthanide by bis(2,4,4-trimethylpentyl)dithiophosphinic acid. Radiochim. Acta 76 (3/4) 129-130. 

Modolo, G., Seekamp, S., Nabet, S. 2002. Development of an extraction process for separation of actinoids(III)/lanthanoids(ni) with the aid of dithiophosphinic acids. Chem. Ing. Tech. 74 (3) 261-265. 

Geist, A., Modolo, G., Weigl, M. 2003. SANEX-IV process development studies Di(chlorophenyl)dithiophosphinic acid as selective extractant for actinides(III). Proc Int Workshop on P T and ADS Development. SCK-CEN, Mol, Belgium, October 6-8. 

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. 

FIGURE 3.22 Soft S-donor dithiophosphinic acidics developed for An(III)/Ln(III) separation. 

Jensen, M.P., Bond, A.H., Rickert, P.G., Nash, K.L. 2002. Solution phase coordination chemistry of trivalent lanthanide and actinide cations with bis(2,4,4-trimeth-ylpentyl)dithiophosphinic acid. Journal of Nuclear Science and Technology (S3) 255-258. 

Modolo, G., Odoj, R. 1998. The separation of trivalent actinides from lanthanides by dithiophosphinic acids from HN03 acid medium. Journal of Alloys and Compounds 271-273 248-251. 

G. Modolo and S. Nabet. Thermodynamic study on the synergistic mixture of bis(chlorophenyl) dithiophosphinic acid and tris(2-ethylhexyl) phosphate for separation of actinides(iii) from lanthanides(iii). Solvent Extr. IonExch., 23(3) 359-373, 2005. 

Sulfur-containing organophosphorus compounds are prone to oxidation and degradation, especially in the presence of acids and strong oxidants. Their hydrolytic and thermal stability increase in the order dialkyl dithiophosphoric acids ((RO)2PSSH) < dialkyl dithiophosphinic acids (R2PSSH), due to the absence of the weak ether bridge. 

In the family of phosphonates (RO)2R PO, the aryl derivatives were more stable than the related alkyl compounds, and the benefit was higher than the effect observed from alkylphosphate to alkylphosphonate (96). The same tendency has been observed with dithiophosphinic acids (RO)R PSSH namely, aromatic ligands were more resistant to hydrolysis and radiolysis than aliphatic compounds (49, 61). It was noted that the introduction of chlorine into the phenyl rings reinforced the radiolytic stability of the extractant (49, 61). 

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