Abstract: The complex of Co(C_(13)H_(14)N_2)Cl_2 was prepared and crystal structures of the Iigand and the complex were determined by X-Ray diffraction. The crystallogr- aphic data and atomic coordinates with equivalent isotropic of the two structures are listed in Table 1 and Table 2 respectively. The tetrahedral coordination is found in the complex of Co(C_(13)H_(14)N_2)Cl_2. The torsion angle between pyridine ring and benzene ring is 5.0° in C_(13)H_(14)N_2 and 73.7° in Co(C_(13)H_(14)N_2)Cl_2. The confor- mations of the ligand in two crystal structures are very different (see Fig.2). The differences of the torsion angles of τ_1, τ_2, τ_3 and τ_4 between conformation 1 (conformation of C_(13)H_(14)N_2 in crystal state) and conformation 2 (conformation of C_(13)H_(14)N_2 in Co(C_(13)H_(14)N_2)Cl_2 crystal state) are 22.5°, 79.1°, -113.2° and 63.3° respectively. EHMO and DPCILO calculations were applied to describe the change of ligand conformations.