High resolution solid state 31P and 15N magic angle spinning nuclear magnetic resonance studies of amorphous and microcrystalline, layered metal (IV) hydrogenphosphates

Abstract

High resolution solid state 31P and 15N MAS NMR have been used to probe the structure of amorphous and microcrystalline layered hydrogenphosphates and their amine intercalation compounds. A linear relationship between δ 31P and electronegativity of the metal centre was observed. In the case of both forms of the titanium and zirconium hydrogenphosphates a linear relationship was seen between isotropic chemical shift and the number of bridging P-O-M oxygens (connectivity) of the phosphate groups. In a further study of the intercalation compounds of tin (IV) hydrogenphosphate monohydrate, the NMR data indicated there to be more proton transfer in the propylamine intercalation (SnP-PrA) compound than is the case with trans-N,N'-diethyl 2-butene-1, 2-diamine (NNBD) and that there is more proton transfer in the case of NNBD that in the ammonium intercalation compound. The extent of protonation of ammonia by different strength acids has also been observed by 15N MAS NMR and has been correlated to the isotropic chemical shift.