High-resolution solid-state 31P and 119Sn magic-angle spinning nuclear magnetic resonance studies of amorphous and microcrystalline layered metal(IV) hydrogenphosphates

Abstract

High-resolution solid-state ³¹P and ¹¹⁹Sn magic-angle spinning nuclear magnetic resonance (MAS NMR) and Mössbauer spectroscopies have been used to probe the structure of amorphous and microcrystalline layered hydrogenphosphates and some of their intercalation compounds. A linear relationship between δ(³¹P) and the Allred–Rochow electronegativity of the metal atom was observed. In the case of both α and γ forms of titanium and zirconium hydrogenphosphates, a linear relationship was seen between the isotropic chemical shift (δ_iso) 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 (SnP), the NMR data indicated there to be more electron transfer in the propylamine intercalation compound than is the case with E-N,N′-diethylbut-2-ene-1,4-diamine (NNBD) and that there is more electron transfer in the case of NNBD than in the ammonium intercalation compound. A linear relationship was observed when δ(¹¹⁹Sn) was plotted as a function of δ(³¹P). The Sn Mössbauer spectrum of the host material was indicative of ionic character around the metal atom and similar to that of SnF₄.