Hybrid framework iron(II) phosphate-Oxalates

Abstract

Two inorganic-organic hybrid framework iron phosphate-oxalates, I, [N₂C₄H₁₂]_0.5[Fe₂(HPO₄)(C₂O₄)_1.5] and II, [Fe₂(OH₂)PO₄(C₂O₄)_0.5], have been synthesized by hydrothermal means and the structures determined by X-ray crystallography. Crystal Data: compound I, monoclinic, SPACEGROUP=P2₁/c (No. 14), a=7.569(2) Å, b=7.821(2) Å, c=18.033(4) Å, β=98.8(1)°, V=1055.0(4) ų, Z=4, M=382.8, D_calc=2.41 g cm^-3, MoKα, R_F=0.02; compound II, monoclinic, SPACEGROUP=P2₁/c (No. 14), a=10.240(1) b=6.375(3) Å, c=9.955(1) Å, β=117.3(1)°, V=577.4(1) ų, Z=4, M=268.7, D_calc=3.09 g cm^-3, MoKα, R_F=0.03. These materials contain a high proportion of three-coordinated oxygens and [Fe₂O₉] dimeric units, besides other interesting structural features. The connectivity of Fe₂O₉ is entirely different in the two materials resulting in the formation of a continuous chain of Fe-O-Fe in II. The phosphate-oxalate containing the amine, I, forms well-defined channels. Magnetic susceptibility measurements show Fe^II to be in the high-spin state (t⁴_2ge²_g) in II, and in the intermediate-spin state (t⁵_2ge¹_g) in I.