Patent GB-787083-A (GB)
Title: Aromatic dithiophosphinic acids, salts thereof, and methods for preparing same
IPC: C09F9/00
Filed: 1955-01-24
Abstract: The invention comprises compounds of the formula <FORM:0787083/IV (b)/1> where R and R1 are the same or different aromatic radicals having six or more carbon atoms, each bonded directly to phosphorus through a benzenoid carbon atom and one or both having at least one of the substituents specified below attached to the aromatic ring, M is hydrogen or metal, and n is the valence of M. The specified substituents are chloro-, alkyl-, cycloalkyl-, aryl-, alkoxy-, aryloxy-, and thioaryloxy-.  The invention also comprises a process for making aromatic dithiophosphinic acids by heating and reacting an aromatic compound as defined below with phosphorus pentasulphide in the presence of an aluminium trihalide of the formula AlX3 where X is halogen, using a molar ratio of halide to pentasulphide of at least 1 : 1.  An aromatic compound is defined as a compound which contains at least one substituted or unsubstituted aromatic ring having at least one hydrogen attached thereto and no functional groups such as -OH, -SH, -NH2 which are reactive with P2S5 at low temperatures in the absence of a catalyst, and which has an ionization constant of less than 1 X 10-10 at 25 DEG  C. in water.  Aromatic compounds mentioned include benzene, naphthalene, anthracene, phenanthrene, naphthacene, chrysene, pyrene, triphenylene, biphenyl, terphenyl, toluene, n-butyl-, lauryl-, cyclohexyl-, lauroxy-, nitro-, and chloro-benzenes, phenoxybiphenyl, diphenyl sulphide, and propyl-nitro-naphthalene. The aluminium halides mentioned are AlCl3 and AlBr3. The reaction may be conducted at 25-300 DEG  C. and at atmospheric or sub- or super-atmospheric pressure, at least 4 mols. of aromatic compound being used per mol. of P2S5.  Inert solvents such as naphtha, kerosene or hexane or an excess of the aromatic compound may be used as diluent, and halides such as SnCl4, ZnCl2, BF3 and FeCl3 may be present. Dithiophosphinic acids having dissimilar aromatic radicals are made by using a substantially equimolar mixture of two aromatic compounds.  The reaction may be effected by mixing the aromatic compound, P2S5 and AlX3 at room temperature and heating, by adding mixed AlX3 and P2S5 to the heated aromatic compound, by adding P2S5 to a heated mixture of AlX3 and aromatic compound, or preferably by adding AlX3 to a heated mixture of P2S5 and aromatic compound, and heating until the theoretical H2S is evolved or until evolution ceases.  The dithiophosphinic acid is liberated from the reaction mass by treatment with water or dilute mineral acid, the organic layer is separated, the solvent removed and the product purified by recrystallization or by reprecipitation from alkaline solution.  Dithiophosphinic acid salts mentioned are those of the alkali and alkaline-earth metals, Mg, Zn, Cd, Cu, Fe, Pb and Cr.  In examples, dithiophosphinic acids are made by the action of P2S5 in the presence of AlCl3 on (1) benzene, (2) toluene, (4) caprylbenzene, (5) chlorobenzene, (6) diphenyl sulphide, (7) sec-amyl-benzene, (8) keryl-benzene, (9) capryl-naphthalene, (10) o-dichloro-benzene, (11) xylene, (12) isopropyl-benzene, (13) ethylbenzene, (14) wax-substituted diphenyl ether; (15) P2S5 is reacted with benzene in the presence of AlBr3; in further examples there are prepared (16) zinc di-(isopropyl-phenyl) phosphinodithioate from the free acid and zinc oxide, (17) barium bis - (di - sec - amyl - phenyl) phosphinodithioate from the acid and BaO, (18) cupric di - (sec - amyl - phenyl) phosphinodithioate from the acid and CuO, and (19) sodium diphenylphosphinodithioate from the acid and NaHCO3; in Example (2) di-tolyl phosphinic acid is made by reacting di-tolyl dithiophosphinic acid with nitric acid.ALSO:In Example 16, a mineral oil composition containing zinc di-(isopropyl-phenyl)-phosphinodithioate, a low viscosity mineral oil and methylcyclohexanol is described.