Hydrothermal synthesis and single-crystal structural characterization of (VO) 2[CH 2(PO 3) 2] · 4H 2O

Abstract

The layered compound (VO) 2[CH 2(PO 3) 2] · 4H 2O has been prepared by hydrothermal synthesis and characterized by single-crystal X-ray diffraction. The structure is orthorhombic, space group pbca with a = 12.805(4) Å, b = 10.592(3) Å, c = 15.037(5) Å, Z = 8, D x = 2.462 g/cm 3, R = 0.0372, and R w = 0.0500 for 2038 independent reflections. The structure is formed from layers of vanadium and oxygen atoms and methylenediphosphonate groups, with coordinated water molecules directed into the interlayer space, resulting in a layer repeat distance ( d 001) of 15.037(5) Å. The layers contain two types of V 4+O 6 octahedra connected through corners by [O 3PCH 2PO 3] 4- groups. V(1) is coordinated by one terminal oxygen atom and three oxygen atoms from water molecules, and chelated by one [O 3PCH 2PO 3] 4- group. V(2) is coordinated by one terminal oxygen atom, one water molecule, and two oxygen atoms from separate [O 3PCH 2PO 3] 4- groups, and chelated by one [O 3PCH 2PO 3] 4- group. The connectivity can be represented as VO 1 1 (H 2O) 3 1 O 2 2 VO 1 1 (H 2O) 1 1 O 4 2 (O 3 2 PCH 2 PO 3 2 ) . The structure illustrates the versatility of the [O 3PCH 2PO 3] 4- group as a connecting unit.