New Haldane gap compounds with S = 1 have been characterized by single-crystal X-ray analyses and magnetic measurements. From these results, it has been found that the magnitude of the Haldane gaps can be controlled by substituting the bridging groups and in-plane ligands. The magnetic measurements of quasi-one-dimensional halogen-bridged binuclear Ru complexes with S = 3/2, Ru-2(CH3COO)(4)X (X = Cl, Br and I) have revealed that the Br- and I-bridged compounds show one-dimensional antiferromagnetic interactions but no spin-Peierls transition over the temperature range measured, while the Cl-bridged compound shows no magnetic interaction among binuclear Rug units through the bridging Cl- ions along the chain but spin-crossover behavior between S = 3/2 and 1/2 in the binuclear Ru-2 unit. The oxalato-bridged Fe2+ compound with S = 2, Fe(ox).2H(2)O has no Haldane gap but shows metamagnetism under the high magnetic field.