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-benzimidazolylmethyl)amine (L) in ethanol, golden yellow crystals of compound 1 were obtained upon slow evaporation of the solvent. The structural assignments of 1 that were made in part by elemental analysis and FAB mass spectroscopy were confirmed by single crystal X-ray diffraction studies. The crystal structure reveals that compound 1 crystallizes in the triclinic space group P (1) over bar with two independent molecules in a cell 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 structure has been refined to an R factor of 0.060 based on 4822 observed reflections. Two independent manganese containing molecules were found in the unit cell. Molecule 1a is cis-dichloro(tris(2-benzimidazolylmethylmanganese(II), with a distorted octahedral geometry. The Cl-Mn-Cl bond angle in the molecule is 96.8(1)degrees showing a severe steric constraint imposed by the ligand which may lead to the elongation of the fifth 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 molecule in the unit cell is a chloro(tris(2-benzimidazolylmethyl)amine)manganese(II) cation (1b), in which the geometry around the manganese atom could best be described as a distorted trigonal bipyramid. The trigonal plane is occupied by the ligating nitrogen atoms from the benzimidazolyl functions with bond lengths of 2.135(8), 2.145(6) and 2.147(4) Angstrom. The axial positions are occupied by the ligating sp(3) nitrogen and chlorine atoms with bond lengths of 2.514(6) and 2.316(2) Angstrom, respectively. This Mn(II) complex shows a remarkable resistance toward oxidation to higher metal oxidation states even with 30% hydrogen peroxide.