65123-84-4Relevant academic research and scientific papers
Copper-Catechol Chemistry. Synthesis, Spectroscopy, and Structure of Bis(3,5-di-tert-butyl-o-semiquinato)copper(II)
Thompson, Jeffry S.,Calabrese, Joseph C.
, p. 1903 - 1907 (1986)
The synthesis, spectroscopy, structure, and reactivity of bis(3,5-di-tert-butyl-o-semiquinato)copper(II), Cu(DTBSQ)2, a Cu(II)-semiquinone complex, are presented.This compound was prepared by reacting X (X = ClO4, Cl) with the corresponding benzoquinone or a basic Cu(II) dimer, (ClO4)2, with the catechol.The complex, which was characterized by analytical, spectroscopic, and X-ray diffraction techniques, crystallizes in the triclinic space group with Z = 2 in a unit cell of dimensions a = 10.262 (3) Angstroem, b = 14.554(4) Angstroem, c = 9.418(2) Angstroem, α = 101.09(2) deg, β = 92.31(2) deg, γ = 108.87(2) deg at -100 deg C.Least-squares refinement of 298 variables led to a value of the conventional R index of 0.049 and Rw = 0.046 for 2296 reflections having I > 3?(I).Each copper ion is coordinated to four oxygen atoms from two DTBSQ ligands.In addition, there is a fifth oxygen atom from a neighboring Cu(DTBSQ)2 molecule coordinated to the copper atom in an axial position; thus, the overall geometry about the metal ion approaches square pyramidal.The C-O bond lengths of the DTBSQ ligands range from 1.290(7) to 1.296(6) Angstroem.The spectroscopic properties and reactions of Cu(DTBSQ)2 are consistent with the Cu(II)-semiquinone formulation.These results suggest that the copper oxidation of catechols takes place in two one-electron-transfer steps.
Coligand-dependent shifts in charge distribution for copper complexes containing 3,5-di-tert-butylcatecholate and 3,5-di-tert-butylsemiquinonate ligands
Speier, Gabor,Tisza, Sandor,Tyeklár, Zoltan,Lange, Christopher W.,Pierpont, Cortlandt G.
, p. 2041 - 2045 (2008/10/08)
Cu(py)2(3,5-DBCat) has been prepared by reacting copper metal with 3,5-di-tert-butyl-1,2-benzoquinone (3,5-DBBQ) in pyridine solution. Crystallographic characterization of the complex obtained as the pyridine solvate (triclinic, P1, a = 13.909(2) ?, b = 14.187(2) ?, c = 14.570(3) ?, α = 75.26(1)°, β = 72.37(1)°, γ = 80.57(1)°, V = 2637.9(9) ?3, Z = 2) has shown that the molecule is dimeric with square pyramidal metal ions bridged at basal positions by oxygen atoms of the catecholate ligands. Pyridine ligands occupy basal and apical sites of the centrosymmetric dimer. The magnetic moment for the dimer decreases from 2.84 μBat room temperature to 0.52 μB at 5.0 K; exchange coupling is antiferromagnetic and has been theoretically fit with a J value of -95.3 cm-1. Cu(PPh3)2(3,5-DBSQ) has been prepared by reacting stoichiometric proportions of 3,5-DBBQ, PPh3, and copper metal in acetonitrile solution. When the reaction was carried out with twice the stoichiometric quantity of copper metal, the product obtained was [CuI(NCCH3)(PPh3)]2[Cu II(3,5-DBCat)2]. Crystallographic characterization (monoclinic, P21/n, a = 16.163(2) ?, b = 9.245(1) ?, c = 21.312(3) ?, β = 99.78(2)°, V = 3138.3(7) ?3, Z = 2) has shown that the centrosymmetric complex molecule consists of a central [Cu(3,5-DBCat)2]2- anion with cationic [Cu(NCCH3)(PPh3)]+ units bonded to bridging oxygen atoms of the catecholate ligands. The EPR spectrum of the complex in the solid state is typical of Cu(II). The EPR spectrum of [CuI(NCCH3)(PPh3)]2[Cu II(3,5-DBCat)2] in toluene solution was characteristically the radical spectrum of (PPh3)2Cu(3,5-DBSQ). This observation is explained in terms of a Cat-to-Cu(II) electron-transfer reaction.
