The complex chemistry of N-(phosphonomethyl)glycine (glyphosate): preparation and characterization of the ammonium, lithium, sodium (4 polymorphs) and silver(I) complexes

A series of complexes with the herbicide glyphosate [N-(phosphonomethyl)gly cine = H3L] has been synthesized and characterized using infrared spectrosc opy, and in the case of five of these, by single crystal X-ray diffraction. The compounds are ammonium glyphosate [NH4][H2L] 1, lithium glyphosate Li( H2L) 2, sodium glyphosate hemi-hydrate Na(H2L). 0.5H(2)O 3, sodium glyphosa te monohydrate Na(H2L). H2O 4, sodium glyphosate dihydrate Na(H2L). 2H(2)O 5, disodium glyphosate nonahydrate Na-2(HL). 9H(2)O 6 and disilver glyphosa te Ag-2(HL) 7. The crystal structures of 1, 3, 4, 6 and 7 have been determi ned. Compound 1 consists of a hydrogen-bonded lattice structure in which al l of the available ammonium protons are involved in hydrogen bonding, toget her with the zwitterionic amine group and the single phosphonate proton. Co mpounds 3 and 4 are both polymeric and based on dimeric repeating units wit h six-co-ordinate sodium centres. Complex 6 is based on both discrete octah edral [Na(HL)(H2O)(5)](-) anionic complex units with the unidentate glyphos ate ligand bonded via a carboxylate oxygen, together with a cationic [Na-2( H2O)(8)](2+) ribbon polymer. All structures have extensive hydrogen bonding interactions. The silver complex 7 is a polymer structure which involves t he phosphonate ligands in linear chains joined through the carboxyl group a t one end (via bis-O,O' bridged silver dimers) and silver co-ordinated phos phonate oxygens at the other.