Novel aluminium phenyl, benzyl, and bromobenzylphosphonates: structural characterisation and hydration–dehydration reactions

Abstract

Reaction of phosphonic acids RPO(OH)2 (R = phenyl, benzyl, 4-bromobenzyl) with aluminium nitrate and sulfate under various hydrothermal conditions led to three novel aluminium phosphonates, Al(OH)(O3PCH2C6H4Br)·H2O, Al(OH)(O3PCH2C6H5)·H2O and Al2(O3PC6H5)3·H2O. All the compounds were characterised by powder XRD, elemental analysis, TGA, 27Al and 31P MAS NMR and IR spectroscopy. The same tools were used to study the dehydration–rehydration reactions. Refinement of the structure of Al(OH)(O3PCH2C6H4Br)·H2O by the Rietveld method showed a lamellar arrangement similar to the methyl analogue ζ-Al(OH)(O3PCH3)·H2O. Al(OH)(O3PCH2C6H4Br)·H2O crystallises in the monoclinic system, space group P21/c with unit cell parameters a = 16.4972(2) A, b = 7.0673(1) A, c = 9.4950(2) A and β = 113.477(1)°. Based on the powder XRD, IR and NMR data the two benzyl compounds were found to be isostructural.