Hydrothermal Synthesis, Crystal Structure, and Thermal Stability of Two New Metal Phosphonates with a Pillared Layered Structure

Two new metal phosphonates with a 3D pillared layered framework based on N , N′ ‐piperazinebis(methylenephosphonic acid), H 2 O 3 PCH 2 NC 4 H 8 NCH 2 PO 3 H 2 (H 4 L), Sn[O 3 PCH 2 NHC 4 H 8 NHCH 2 PO 3 ] ( 1 ) and Pb 3 (OH) 2 [O 3 PCH 2 NC 4 H 8 NCH 2 PO 3 ] ( 2 ), have been synthesized under hydrothermal conditions and structurally characterized by single‐crystal X‐ray diffraction as well as with infrared spectroscopy, elemental analysis and thermogravimetric analysis. For compound 1 , each ψ‐square pyramidal SnO 4 unit is in turn corner‐shared by four CPO 3 tetrahedral from four different phosphonate ligands to form two‐dimensional inorganic puckered layers in ab planes. In compound 2 , the complicated inorganic layer ( bc planes) is built up of ψ‐PbO 4 N, PbO 6 and CPO 3 polyhedra. The overall structure for two compounds may be described in terms of alternating inorganic infinite layers and organic pillars {CH 2 N(C 2 H 4 ) 2 NCH 2 }, to form a 3D pillared layered structure.