Three iron(II) complexes with a linear symmetrical pentadentate ligand H 2 L 1 and a monodentate ligand X (X=N 3 − , NCS − , NCSe − ), [Fe II N 3 (H 2 L 1 )]BPh 4 (1), [Fe II NCS(H 2 L 1 )]BPh 4 (2), and [Fe II NCSe(H 2 L 1 )]BPh 4 (3), were synthesized and characterized, where H 2 L 1 denotes bis(N,N′-2-methylimidazol-4-yl-methylideneaminopropyl)methylamine. Compounds 1, 2 and 3 consist of a mononuclear complex-cation of [Fe II X(H 2 L 1 )] + (X=N 3 − , NCS − , NCSe − ) and a tetraphylborate (BPh 4 − ) anion. Each complex-cation has an octahedral coordination geometry with N 6 donor atoms of a linear pentadentate ligand of H 2 L 1 and a nitrogen atom of N 3 − , NCS − , or NCSe − , in which the linear pentadentate ligand is folded to coordinate to Fe II ion in a cis-form. One of two imidazole groups of a complex-cation is hydrogen bonded to N 3 − , NCS − , or NCSe − of the adjacent complex-cation to form a cyclic dimer structure for 1 and a zigzag-chain structure for 2 and 3. The temperature dependence of the magnetic data revealed that 1, 2 and 3 are high-spin (HS) complexes.