SYNTHESIS AND X-RAY-POWDER STRUCTURES OF COVALENTLY PILLARED LAMELLARZINC BIS(PHOSPHONATES)

Two new lamellar metal phosphonates, zinc phenylenebis(phosphonate), Z n-2[(O3PC6H4PO3)(H2O)(2)] (1), and zinc biphenylylenebis(phosphonate), Zn[HO3P(C6H4)(2)PO3H] (2), have been synthesized. The structures of t hese compounds were solved ab initio from X-ray powder diffraction dat a and refined by Rietveld methods. Compound 1 is orthorhombic: space g roup Pnnm, a=19.2991(6) Angstrom, b=4.8232(2) Angstrom, c=5.6545(2) An gstrom, and Z=2. The structure is layered, and its layer arrangement i s similar to that in zinc phenylphosphonate. The zinc atoms are octahe drally coordinated. Two of the oxygens of the phosphonate group are in volved in chelation and bridging the metal atoms. The third oxygen bin ds to only one metal atom. The sixth coordination site is occupied by a water molecule. The adjacent layers are bridged by the phenylene gro up of the bis(phosphonate). Compound 2 is triclinic: space group <P(1) over bar>, a=9.5097(3) Angstrom, b=5.0074(2) Angstrom, c=14.2109(4) An gstrom, alpha=92.797(3)degrees, beta=99.725(3)degrees, gamma=92.003(3) degrees, and Z=2. In this case the metal atoms are tetrahedrally coord inated by four oxygens. two from each of the phosphonate groups of the bis(phosphonate). The third oxygen of the phosphonate group is proton ated and is not involved in metal binding. The structure consists of d ouble chains with alternating Zn and P atoms connected to each other b y phosphonate bridges. These double chains run along the b axis and ar e linked to similar chains along the a direction through hydrogen bond s involving P-OH groups. This arrangement leads to loosely bound metal -CPO3 networks in the ab plane which are bridged by the biphenylylene groups along the c axis. Thus in a broad sense this compound may also be considered as layered.