MANGANESE(II) COMPLEX OF THE TRIPOD LIGAND TRIS(2-BENZIMIDAZOLYLMETHYL)AMINE - 5-COORDINATE AND 6-COORDINATE MN(II) IN THE CRYSTAL-STRUCTURE

From the reaction of manganese dichloride with tris(2-benzimidazolylme thyl)amine (L) in ethanol, golden yellow crystals of compound 1 were o btained upon slow evaporation of the solvent. The structural assignmen ts of 1 that were made in part by elemental analysis and FAB mass spec troscopy were confirmed by single crystal X-ray diffraction studies. T he crystal structure reveals that compound 1 crystallizes in the tricl inic space group P (1) over bar with two independent molecules in a ce ll of dimensions a = 13.805(4), b = 14.185(4), c = 18.176(5) Angstrom, alpha = 81.23(2), beta = 70.32(2), gamma = 61.45(2)degrees. The struc ture has been refined to an R factor of 0.060 based on 4822 observed r eflections. Two independent manganese containing molecules were found in the unit cell. Molecule 1a is dichloro(tris(2-benzimidazolylmethylm anganese(II), with a distorted octahedral geometry. The Cl-Mn-Cl bond angle in the molecule is 96.8(1)degrees showing a severe steric constr aint imposed by the ligand which may lead to the elongation of the fif th and the sixth axial bond lengths, (Mn(1)-Cl(1) and Mn(1)-N(1) bond lengths of 2.538(2) and 2.515(7) Angstrom, respectively). The other mo lecule in the unit cell is a ro(tris(2-benzimidazolylmethyl)amine)mang anese(II) cation (1b), in which the geometry around the manganese atom could best be described as a distorted trigonal bipyramid. The trigon al plane is occupied by the ligating nitrogen atoms from the benzimida zolyl functions with bond lengths of 2.135(8), 2.145(6) and 2.147(4) A ngstrom. The axial positions are occupied by the ligating sp(3) nitrog en and chlorine atoms with bond lengths of 2.514(6) and 2.316(2) Angst rom, respectively. This Mn(II) complex shows a remarkable resistance t oward oxidation to higher metal oxidation states even with 30% hydroge n peroxide.