Structural homologies in benzylamino-N,N-bis methylphosphonic acid and its layered zirconium derivative

A new layered zirconium diphosphonate fluoride, ZrF(O 3PCH 2) 2NHCH 2C 6H 5 has been prepared and its structure determined ab initio by X-ray powder data and refined with the Rietveld method (orthorhombic, a=8.9429(2)Å, b=9.1746(2)Å, c=31.5654(7)Å, space group Pbca, V=2589.9(1)Å3, Z=8, Rwp=0.080). Both phosphonic groups of each diphosphonate building block are bonded to zirconium atoms on the same side of each layer. Benzyl groups from adjacent layers are interdigitated in the interlayer region, with probable π-π stacking interactions. The structure of the free benzylamino-N,N-bis methylphosphonic acid has been determined by single crystal X-ray data (monoclinic, space group P2 1, a=6.990(3)Å, b=5.635(2)Å, c=15.551(6)Å, β=92.930(3)°, V=611.7(4)Å3, Z=2, R1=0.072, wR2=0.150). As in the zirconium derivative, benzyl groups from adjacent layers are interdigitated and create a regular alternation of polar and non-polar regions. The structure of a new layered zirconium diphosphonate fluoride, solved by X-ray powder diffraction data, and that of the corresponding diphosphonic acid showed similar features, due to analogous structure orienting factors.