SYNTHESIS AND CHARACTERIZATION OF A LINEAR μ-OXO DIIRON(III) COMPOUND AND A COPPER(II) NITRITE COMPLEX CONTAINING, A TRIPODAL POLYBENZIMIDAZOLE LIGAND

Abstract

Iron(III) and copper(II) complexes of the polybenzimidazole ligand, tris((benzimidazol-2-yl)methyl)amine (tmba) have been synthesized and structurally characterized. The mononuclear complex [Cu(tmba)(NO2)]+[CH3OH][NO− 2], 1, has been isolated and characterized by X-ray crystallography. The complex crystallizes in the triclinic space group P1 with two molecules in the unit cell of dimension a = 8.891(5), b = 11.775(6), and c = 13.702(8)Å, and α = 67.76(1), β = 71.79(2) and γ = 88.96(1)°, and volume = 1253.0(12)Å3. The structure was refined to a final agreement factor R = 0.0901 using 4134 observed reflections. The complex consists of cationic copper(tmba) complex covalently bonded to a nitrite, and a pair of these cations is dibridged by a pair of nitrite anions. The gap between this dimer is occupied by a methanol molecule. The coordination environment around each copper can be described as trigonal bipyramidal, with the tertiary amine, a benzimidazole nitrogen and an oxygen from the nitrite providing the ligating atoms of the trigonal plane. The μ-oxo bridged binuclear complex [Fe2O(tmba)2Cl2](H2O)(EtOH)2·Cl2, 2, was also characterized by single crystal X-ray diffraction and magnetic susceptibility. The complex crystallizes in the triclinic space group P1 with one molecule in the unit cell of dimensions, a = 11.5791(7), b = 13.3369(8), and c = 13.7002(9) Å, and α = 103.904(1), β = 108.903(2) and γ = 112.845(1)°, and volume = 1674.1(2) å3. The structure was refined to a final agreement factor R = 0.073 using 5597 observed reflections. The complex is a centrosymmetric dimer, with the two iron(III) atoms bridged by an oxygen atom, with an Fe—O—Fe angle of 180°, and a Fe—Fe distance of 3.61(1)Å. The coordination around each iron(III) is best described as octahedral, with the bridging oxygen trans to one end of the benzimidazole group, and a chlorine atom trans to the tertiary amine nitrogen of the ligand.