Process for preparing ethylenedialkylphosphinic acids, esters and salts by means of acetylene and use thereof

A process for preparing ethylenedialkylphosphinic acids, or salts or esters thereof comprising the steps of

• a) reacting a phosphinic acid source (I)
• with olefins IV
• in the presence of a catalyst A to give an alkylphosphonous acid (II), or salt or ester thereof,
• b) reacting the alkylphosphonous acid (II), or salt or ester thereof with at least one acetylenic compound (V)
• in the presence of at least one catalyst B to give an ethylenedialkylphosphinic acid derivative (III)
• where R1-R6 are each H, R11-R14 are each H,X is H, Ca, Mg, Al, Zn, Ti, Mg, Ce, Fe, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert- butyl, phenyl, 2-hydroxethyl, 2-hydroxypropyl, 3-hydroxypropyl, 4-hydroxybutyl, allyl, glycerol or a combination thereof and the catalyst A is a transition metal or a transition metal compound catalyst system comprising of a transition metal or a transition metal compound and at least one ligand, and the catalyst B is peroxide-forming compound, peroxo compound, azo compound or a combination thereof selected from the group consisting of hydrogen peroxide, sodium peroxide, lithium peroxide, potassium persulfate, sodium persulfate, ammonium persulfate, sodium peroxodisulfate, potassium peroxoborate, peracetic acid, benzoyl peroxide, di-t-butyl peroxide, peroxodisulfuric acid, azodiisobutyronitrile, 2,2′-azobis(2-amidinopropane) dihydrochloride, 2,2′-azobis(N,N′-dimethyleneisobutyramidine) dihydrochloride and a combination thereof.