Disproportionation of manganese(II) (1-hydroxyethylidene) diphosphonate in reaction with 2-aminoethanol

Abstract

Reaction of poorly soluble manganese(II) bis(1-hydroxyethylidene)diphosphonate tetrahydrate Mn(H₃L)₂ · 4H₂O with 2-aminoethanol H₂NCH₂CH₂OH in an aqueous solution on heating to 70–80°C causes the initial formation of soluble tris(2-hydroxyethanaminium) manganese(II) bis(1-hydroxyethylidene) diphosphonate Mn(H₃L)₂ · 3H₂NCH₂CH₂OH · 4H₂O, which next disproportionates into poorly soluble 2-hydroxyethanaminium manganese(II) (1-hydroxyethylidene)diphosphonate MnH₂L · H₂NCH₂CH₂OH and metal-cation-free coordination polymer of (1-hydroxyethylidene)diphosphonic acid with 2-aminoethanol. Poorly soluble MnH₂L · H₂NCH₂CH₂OH can be readily converted into the soluble form by treatment with 2-aminoethanol or 2-amino-2-(hydroxymethyl)propane-1,3-diol H₂NC(CH₂OH)₃.