Hydrothermal synthesis , characterization and crystal structures of two new layered lead( ii ) diphosphonates
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Hydrothermal reactions of N-benzyliminobis(methylenephosphonic acid), C6H5CH2N(CH2PO3H 2)2 (H4L), with lead(II) chloride and lead(II) acetate resulted in two novel lead(II) phosphonates, namely, Pb 5(H2L)2(HL)2·2H2O (1) and Pb3(H2L)2Cl(H2O) 3·Cl·2H2O (2). Compound 1 is orthorhombic, Pbca, with Z = 4. Compound 1 features a layered structure in which the lead(II) ions are bridged by phosphonate groups. Two lead(II) ions (Pb1 and Pb3) are three-coordinated with a distorted tetrahedral geometry in which one apex is occupied by the lone pair of the lead(II) ion, the third lead(II) ion (Pb2) is six-coordinated by six phosphonate oxygen atoms from six ligands. Two ligands are doubly protonated whereas the other two are singly protonated. Compound 2 crystallizes in I2/a with Z = 4. In compound 2, one lead(II) ion is six-coordinated by four phosphonate oxygen atoms from four ligands, one aqua ligand and one chloride anion in a distorted octahedral geometry; the other lead(II) ion is coordinated by four phosphonate oxygen atoms from four ligands and two aqua ligands with a severely distorted octahedral geometry. One phosphonate group of the ligand bridges with five lead(II) ions, whereas the other one is unidentate. The interconnection of the lead(II) ions through bridging phosphonate groups results in the formation of a 〈040〉 layer. In both compounds, the phenyl groups of the ligand are oriented toward the interlayer space.
author list (cited authors)
Sun, Z., Mao, J., Sun, Y., Zeng, H., & Clearfield, A.