A novel two-dimensional oxalate-bridged complex {[Cu(en)~2]~4[KFe (C~2O~4)~3]~4}~n has been synthesized and structurally and magnetically and magnetically characterized. In this complex the eight-coordinate environment of K^+ ions leads to a unique structural arrangement with two C~2O~4^2^- bridges and two or one K^+ ion linking pairs of Fe^Ⅲ ions. As a consequence, a novel 2D[KFe(C~2O~4) ~3]~n^2^n^- network forms. Another feature of the structure is the presence of hydrogen bonding connecting the Cu(en)~2^2^+ entities and [KFe(C~2O~4)~3]~n^2^n^- network through (en)N-H...O(C~2O~4). The magnetic susceptibility data good fits to the experimental data from room temperature to 4.2K were obtained for J=-0.17cm^-^1.

Key words: CRYSTAL STRUCTURE, MAGNETISM, HYDROGEN BONDS, OXALATO COMPLEX, ETHANEDIAMINE, COPPER COMPOUNDS, IRON COMPOUNDS, POTASSIUM COMPOUNDS