Organische Phosphorverbindungen XXXVI. Darstellung und Eigenschaften von Bis‐(dialkoxyphosphonyl‐methyl)‐, Bis‐(alkoxyphosphinyl‐methyl)‐und Bis‐(oxophosphoranyl‐methyl)‐phosphinsäureestern sowie der entsprechenden Säuren [1]

High yields of bis‐(dialkoxyphosphonyl‐methyl)‐ phosphinic esters, (RO) 2 (O)‐PCH 2 P(O)OR, bis‐(aloxyphosphinyl‐methyl)‐phosphinic esters, [R(RO)(O)PCH 2]2 P(O)OR, are obtained by heating bis‐chloromethyl‐phosphinic esters, (CICH 2)2 P(O)OR, with alkylphoshites, phosphonites and phosphinites, repectively, at 170 to 180°C for several hours. Hydrolysis of these esters in achieved by refluxing with conc. HCl for extended periods. Bis‐(dihydroxyphosphonyl‐methyl)‐phosphinic acid, HO(O)P[CH 2 P(O) (OH) 2 ] 2 , obtained by hydrolysis of the all‐ethyl ester, titrates in aqueous solution as a tetrabasic acid with breaks at pH = 5,2 (three equivalents) and at pH = 8,8 (one equivalent). The fifth proton can be titrated only after addition of NaCl. This acid is an excellent chelating agent for metal ions. The 1 H‐ and 31 P‐NMR. spectra of all the compounds prepared are discussed.