metal-organic compounds
The crystal structures of phosphonoacetic acid, C2H5O5P [H3AP, (I)], and its salts potassium phosphonoacetate hydrate, K+.C2H4O5P−.H2O [KH2AP.H2O, two crystalline forms, α, (II), and β, (III)], ammonium phosphonoacetate, NH4+.C2H4O5P− [(NH4)H2AP, (IV)], lithium phosphonoacetate, Li+.C2H4O5P− [LiH2AP, (V)], sodium phosphonoacetate dihydrate, Na+.C2H4O5P−.2H2O [NaH2AP.2H2O, (VI)], dipotassium phosphonoacetate, 2 K+.C2H3O5P2− [K2HAP, (VII)], diammonium phosphonoacetate, 2NH4+.C2H3O5P2− [(NH4)2HAP, (VIII)], disodium phosphonoacetate dihydrate, 2Na+.C2H3O5P2−.2H2O [Na2HAP.2H2O, (IX)], triammonium phosphonoacetate dihydrate, 3NH4+.C2H2O5P3−.2H2O [(NH4)3AP.2H2O, (X)], and trisodium phosphonoacetate decahydrate, 3Na+.C2H2O5P3−.10H2O [Na3AP.10H2O, (XI)], are described. In all cases, one of the phosphonate O atoms (denoted O2) is nearly antiperiplanar to the carboxylic C1 atom. There is also an evident tendency for the plane through the carboxyl group to be almost perpendicular to the plane through the methylene C atom C2, P and O2. In the acid anions the dihedral angles between these planes range from 75.6 (1)° in (V) to 89.0 (1)° in (VII) whereas in the free acid, (I), this angle is 50.6 (1)°.