Synthesis, structure, and magnetic properties of a new three-dimensional iron phosphite, [C<SUB>4</SUB>N<SUB>2</SUB>H<SUB>12</SUB>][Fe<SUB>4</SUB>(H<SUB>2</SUB>O)<SUB>3</SUB>(HPO<SUB>3</SUB>)<SUB>7</SUB>]&#183;(H<SUB>2</SUB>O)<SUB>x</SUB>x = 0.6

A new open-framework iron phosphite, [C4N2H12][Fe4(H2O)3(HPO3)7]&#183;(H2O)xx = 0.6 (1), has been prepared by the hydrothermal reaction between FeCl3&#183;6H2O, H3PO3, and piperazine. The three-dimensional structure is comprised of a network of FeO6, FeO5(H2O), and HPO3 polyhedral units connected through their vertices. The structure has layers formed by the well-known 4.6.12-net connectivity and is stacked in an AAAA... sequence, penetrated by the one-dimensional pillar units, forming a three-dimensional pillared-layer structure. This connectivity gives rise to two independent 12-ring channel systems. Magnetic studies indicate antiferromagnetic behavior at high temperatures, with a small ferromagnetic polarization at low temperatures