New Lead Inorganic−Organic Hybrid Microporous and Layered Materials: Synthesis, Properties, and Crystal Structures

Two new lead(II) phosphonates, namely, Pb2{PMIDA}·1.5H2O (1) (H4PMIDA = H2O3PCH2N(CH2CO2H)2) and Pb(H2L) (2) (H4L = CH3N(CH2PO3H2)2), have been synthesized by hydrothermal reactions at 150 °C. Complex 1
crystallized in tetragonal P42/n with cell dimensions of a = 17.317(7) and c = 7.507(5) Å and Z = 8. In complex
1, Pb(1) is 6-coordinated by chelation in a tetradentate fashion by a PMIDA ligand (3 O, 1 N) and two phosphonate
oxygen atoms from neighboring Pb(PMIDA) units in a severely distorted octahedral geometry, whereas Pb(2) is
6-coordinated by 4 carboxylate and 2 phosphonate oxygen atoms also with a severely distorted octahedral
environment. These two different types of Pb(II) ions are interconnected through bridging carboxylate and phosphonate
groups, resulting in a 3D network with micropores, whose cavity is filled by lattice water molecules interlinked via
hydrogen bonds. Each PMIDA ligand bridges with 8 Pb(II) ions (3 Pb(1) and 5 Pb(2)). Complex 2 is orthorhombic,
P212121, with a = 7.382(5), b = 7.440(6), and c = 30.75(2) Å and Z = 8. The structure of 2 features a 2D double
lead(II) phosphonate layer along the ab plane. Each lead(II) ion is 5-coordinated by five phosphonate oxygen
atoms from four ligands in a distorted trigonal bipyramid geometry. These double layers are further interconnected
via hydrogen bonds between the protonated and uncoordinated phosphonate oxygens along the c-axis.