Amine-Intercalated Layered $Sn^{II}$ Phosphates with Open-Framework Structures

Abstract

Three new $Sn^{II}$ phosphate materials, $[NH_3(CH_2)_3NH_2(CH_2)_2-NH_2(CH_2)_3NH_3]·2[Sn_2P_2O_8]$ (I), $[(N_2C_5H_{14})_2][Sn_4P_4O_{16}]·3H_2O$ (II) and $[(N_2C_5H_{14})][Sn_2P_2O_8]·H_2O$ (III), have been synthesised by means of hydrothermal methods using N,N'-bis(3-aminopropyl)ethylenediamine (BAPEN; for I) and homopiperazine (H-PIP; for II and III), respectively, as the structure-directing organic amines. The solids I–III have layered architectures. The structures of all three compounds consist of strictly alternating vertex-sharing trigonal-pyramidal $SnO_3$ and tetrahedral $PO_4$ moieties forming infinite layers possessing apertures bound by 4- and 8-T atoms (T = Sn, P). The distorted 4- and 8-membered apertures within the layers suggest the subtle influence of the lone-pair of electrons of SnII on the structure. The interlamellar space is occupied by the protonated organic amine molecules which interact with the framework through N–H···O hydrogen bonding. The compounds I–III bear some structural relationship to the layered zinc phosphite phases