The crystal structures of a pair isomers of [Co(3,3 tri)(amp)Cl] (here 3,3 tri = N (3 Aminoprop yl) 1,3 propanediamine; amp=2 (Aminomethyl)pyridine) have been determined by single crystal X ray diffraction. They are the epimers with the only difference of the orientation of the Sec NH proton in 3,3 tri ligand. The crystals with the anti epimer (m1·CH3OH·H2O) are monoclinic, space group C2/c with eight molecules in a unit cell of dimensions a=30.401(5)?,b=8.0469(13)?,c=18.817(3)?,β=93.346(3)°,V=4595.3(12)?3,Dc=1.708g·cm-3,Z=8,F000=2416,R=0.0462,Rw=0.1304. The crystals of the syn epimer (m2·H2O) are triclinic, space group with two molecules in a unit cell of dimensions a=8.9752(12)?,b=9.8855(12)?,c=12.6886(16)?,α=89.228(3)°,β=76.447(2)°,γ=80.428(3)°,V=1078.8(2)nm3,Dc=1.721g·cm-3,Z=2,F000=568,R=0.0313,Rw=0.0929. The crystal parameters, such as bond lengths and angles, are well consistent with the data of an ab initio computational result (RHF/LANL2DZ optimised structure). The average error for bond length is about 1.6%, only two of them in the isomer m3 (Co N2 and Co N4) are over 3%, (3.09% and 4.28% respectively). The errormax for bond angle is 2.52%, the bond angles with an over 2% error are only 3.6% out of all bond angles.
