Inorganic Chemistry, Vol.34, No.3, 728-736, 1995
Structure of Dicopper Complexes of N,N,N’,N’-Tetrakis((2-Benzimidazolyl)Methyl)-2-Hydroxy-1,3-Diaminopropane with Chloride Counterions
The structures of four dicopper complexes of binucleating ligand HL-H (N,N,N’,N’-tetrakis[(2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane) with chloride counterions were investigated by the X-ray diffraction method. In Cu-2(HL-H)Cl-4.2H(2)O.Et(2)O.CH3OH (a = 33.837(9) Angstrom, b = 9.648(3) Angstrom, c = 32.027(8) Angstrom, beta = 118.82(3)degrees, Z = 8, monoclinic, C2/2), 1, one chloride is not coordinated. A square pyramidal geometry is found for both the CuN3Cl2 and CuN3OCl coordination sites in which the N-3 tripodal coordination sites come from the two symmetric halves of the ligand. In Cu-2(HL-H)Cl-4.5H(2)O.2CH(3)OH.0.5CH(3)CN (a = 12.124(5) Angstrom, b = 14.354(5) Angstrom, c = 16.361(6) Angstrom, alpha = 67.52(3)degrees, beta = 89.97(3)degrees, gamma = 65.77(3)degrees, Z = 2, triclinic, P (1) over bar), 2, which was obtained from the same solution as that for 1 on addition of sodium azide, the basic coordination environments of the two copper ions are the same as in 1 : CuN3Cl2 and CuN3OCl in square pyramidal geometry. 1 and 2 are rotational isomers. In Cu-2(HL-H)Cl-2(ClO4)(2).1.5Et(2)O.CH3OH (a = 11.684(4) Angstrom, b = 13.543(5) Angstrom, c = 17.750(7) Angstrom, alpha = 110.78(4)degrees, beta = 72.63(3)degrees, gamma = 109.67(3)degrees, Z = 2, triclinic, P (1) over bar), 3, the complex exists asa dimer; the two monomers are connected by two bridging chloride ions. The basic coordination environments of the two copper ions are square pyramidal CuN3Cl2 and CuN3OCl. In Cu-2(HL-H)Cl-2(ClO4)(2).5H(2)O.Et(2)O.C2H5OH (a = 11.70(2) Angstrom, b = 14.65(3) Angstrom, c = 19.45(4) Angstrom, alpha = 100.2(2)degrees, beta = 105.7(1)degrees, gamma = 107.0(2)degrees, Z = 2, triclinic, P (1) over bar), 4, the coordination of both copper ions is CuN3OCl; the hydroxy group bridges between two copper ions. However, the geometries of the two copper ions are distinct; one is square pyramidal, and the other is distorted trigonal bipyramidal. Together with the known structures of dicopper complexes of HL-Et, HL-H types of ligands are obviously flexible. The distances between the two copper ions in each monomer are in the range 4.9-7.2 Angstrom. All copper ions in 1-4 are pentacoordinate. This tendency of tripodal N-3 coordinated Cu(II) to form pentacoordinate Cu(II). is used to rationalize the structures of 1-4. The endogenous hydroxy groups in 1-4 do not deprotonate. 1-4 are the first reported structurally characterized examples of coordination of nondeprotonated alcoholic hydroxy groups to Cu(II) in dicopper complexes. In 4, the hydroxy group even bridges between two Cu(II) ions.
Keywords:DINUCLEAR COPPER(II) COMPLEXES;RAY CRYSTAL-STRUCTURE;MAGNETIC-PROPERTIES;ACTIVE-SITE;MOLECULAR-STRUCTURE;HEMOCYANIN MODELS;DIOXYGEN BINDING;SPECTROSCOPIC COMPARISONS;BINUCLEATING LIGANDS;REVERSIBLE BINDING