691402-11-6Relevant articles and documents
Tetradentate Bis(o-iminobenzosemiquinonate(1-)) π Radical Ligands and Their o-Aminophenolate(1-) Derivatives in Complexes of Nickel(II), Palladium(II), and Copper(II)
Min, Kil Sik,Weyhermueller, Thomas,Bothe, Eberhard,Wieghardt, Karl
, p. 2922 - 2931 (2004)
The coordination chemistries of the potential tetradentate ligands N,N′-bis(3,5-di-tert-butyl-2-hydroxyphenyl)ethylenediamine, H 4[L1], the unsaturated analogue glyoxal-bis(2-hydroxy-3,5-di-tert-butylanil), H2[L2], and N,N′-bis-(2-hydroxy-3,5-di-tert-butylphenyl)-2,2-dimethylpropylenediamine, H4[L3], have been investigated with nickel(II), palladium(II), and copper(II). The complexes prepared and characterized are [NiII(H3L1)2] (1), [Ni II(HL2)2]·5/8CH2Cl 2 (2), [NiII(L3··)] (3), [pd II(L3··)][pdII(H 2L3) (4), and [CuII(H2O)(L 4)] (5), where (L4)2- is the oxidized diimine form of (L3)4- and (L3··) 2- is the bis(o-iminosemiquinonate) diradical form of (L 3)4-. The structures of compounds 1-5 have been determined by single crystal X-ray crystallography. In complexes 1 and 2, the ligands (H3L1)- and (HL2) - are tridentate and the nickel ions are in an octahedral ligand environment. The oxidation level of the ligands is that of an aromatic o-aminophenol. 1 and 2 are paramagnetic (μeff ～ 3.2 μ B at 300 K), indicating an S = 1 ground state. The diamagnetic, square planar, four-coordinate complexes 3 and [pdII(L 3··)] in 4 each contain two antiferromagnetically coupled o-iminobenzosemiquinonate(1-) π radicals. Diamagnetic [pd II(H2L3)] in 4 forms an eclipsed dimer via four N-H...O hydrogen bonding contacts which yields a nonbonding Pd...Pd contact of 3.0846(4) A. Complex 5 contains a five-coordinate CuII ion and two o-aminophenolate(1-) halves in (L4) 2-. The electrochemistries of complexes 3 and 4a ([Pd II(L3··)] of 4) have been investigated, and the EPR spectra of the monocations and -anions are reported.
