Formation of a layered framework structure based upon 4-methyl-2,6- bis(methylphosphonic acid) phenol

The trifunctional ligands, (HO)₂P(O)CH_{2 2}C₆H₂(R)OH, (5-H₄) (R = CH ₃, Br) were prepared in good yield via an Arbusov reaction between P(OEt)₃ and the respective 4-R-2,6-bis(chloromethyl)phenols followed by acidic aqueous hydrolysis and they were spectroscopically characterized by IR and NMR techniques. The ligand 5-H₄-CH₃ readily dissolves lanthanide hydroxide residues and it forms a crystalline complex from aqueous LaCl₃ solutions. This complex was characterized by single crystal X-ray diffraction methods and found to adopt a complex 2-D lamellar network in the bc plane. The La(iii) inner coordination sphere is seven coordinate formed by oxygen atoms from two water molecules and five phosphonate oxygen atoms from three different ligands. The phenolic oxygen atom is not involved in the ligand binding to La(iii).