High-resolution solid-state magic angle spinning nuclear magnetic resonance studies on the layered antimony hydrogen phosphate, HSb(PO4)2·2H2O, and its reaction products with tetrakis(pyridyl)iron(II) chloride

Abstract

The antimony hydrogen phosphate, HSb(PO 4 ) 2 ·2H 2 O (denoted H 1 SbP 2 ·2H 2 O), has been synthesised via the ion exchange of crystalline KSb(PO 4 ) 2 , (K 1 SbP 2 ), with 9 m HNO 3 . Scanning electron microscopy (SEM) confirmed that the crystalline K 1 SbP 2 was formed by the so-called ‘deck of cards’ mechanism to give randomly orientated lamellae. The synthesised H 1 SbP 2 ·2H 2 O host material was studied using 1 H and 31 P magic angle spinning nuclear magnetic resonance (MAS NMR) techniques. Intercalation studies were carried out using tetrakis(pyridyl)iron(ii) chloride, [Fe(py) 4 Cl 2 ]·H 2 O. The resulting products were analysed using powder X-ray diffraction (PXRD) and 31 P MAS NMR techniques. The former suggested that the [Fe(py) 4 Cl 2 ]·H 2 O complex lost its water of crystallisation during the reaction and did not intercalate in its intact state between adjacent layers of the H 1 SbP 2 ·2H 2 O crystallites. 31 P MAS NMR data suggested that the H 1 SbP 2 ·2H 2 O–[Fe(py) 4 Cl 2 ] reaction products contained phosphorus resonances which could be assigned as belonging to (i) unaltered host H 1 SbP 2 ·2H 2 O (protonated) phosphate groups, (ii) phosphate groups bonded to the intercalating species. In addition, a separate, Q P 3 , resonance was also noted which was thought to arise from a chemically unaltered phosphate group of the host H 1 SbP 2 ·2H 2 O perturbed by the close proximity of the sorbed [Fe(py) 4 ] 2+ cationic species.