Synthesis and ab initio structural determination of a new pillared nickel diphosphonate: VSB-6 or Ni_5.4(OH,F)₄[O₃P- (CH₂)₃-PO₃]₂ (H₂O)_1.4·1.2H₃O

Ni_5.4(OH,F)₄[O₃P- (CH₂)₃PO₃]₂ (H₂O)1.4·1.2H₃O or VSB-6 was prepared under hydrothermal conditions (4-6 days, 180°C, autogenous pressure). It was structurally characterized, ab initio, from laboratory X-ray powder diffraction data: orthorhombic, space group Pmmn (n°59), a = 17.937(1), b = 6.4299(4), c = 4.4936(3) Å, V = 518.27(4)ų,D_c = 2.694 g·cm^-3. The structure is built up from inorganic layers, Ni_5.4(OH,F)₄O₁₂P₄ (H₂O)1.4, constructed from chains of edge-sharing octahedra onto which are grafted phosphonate groups and statistically occupied nickel octahedra. The alkyl chain of the organic moiety connects the inorganic layers to form a pillared solid. VSB-6 is stable under air up to 400°C. On cooling to 6 K, VSB-6 orders magnetically with a canted antiferromagnetic structure.