Synthesis of molecular phosphonates of group III elements


                           Libor Tanzinger, Zdeněk Moravec, Jiří Pinkas

                 Masaryk University, Department of Chemistry, Brno, Czech Republic


The general procedur es for preparation of transition metal phosphonates involve hydrothermal
synthesis. Common traits shared by hydrothermally prepared metal phosphonates are layered 2D
structures and a low solubility in a wide range of solvents. On the other hand, phosphonates
produced by a simple salt metathesis in aprotic organic solvents, such as pyridine, can form
products with very different molecular cluster geometries. A series of reactions of ScCl[3], YCl[3]
and LaCl[3] with tert-butyl, phenyl and vinyl phosphonic acids have been performed in dry pyridine.
Obtained products have been studied by ^31P NMR spectroscopy and by single-crystal XRD analysis.
Three products have been isolated and structurally characterized using SCXRD. From the the
reactions of tert-butyl phosphonic acid with yttrium(III) and La(III) it is
[μ[3]-^tBuP(O)[3]][4](YClpy[2])[2](YCl[2]pyH)[2] in pseudo-cubane geometry with
[Hpy][3][YCl[6]]·2py as a byproduct and
La[4][μ[6]-^tBuP(O)[3]][2][μ[4]-^tBuPO[2](OH)][2](μ[2]-Cl)[2]Cl[8](Hpy)[6] with bridged-square
geometry. Moreover, such molecular products still exhibit reasonable solubility in organic
solvents, such as pyridine and DMSO.