Hybrid Framework Iron(II) Phosphate-Oxalates

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) Å3, 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) Å3, 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 FeII to be in the high-spin state (t 4 2g e 2 g ) in II, and in the intermediate-spin state (t 5 2g e 1 g ) in I.