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Copper Complexes of “Superpodal” Amine Ligands and Reactivity Studies towards Dioxygen
Author(s) -
Jozwiuk Anna,
Ünal E. Alper,
Leopold Stefan,
Boyd John P.,
Haryono Marco,
Kurowski Nadine,
Escobar Francisco Velazquez,
Hildebrandt Peter,
Lach Jochen,
Heinemann Frank W.,
Wiedemann Dennis,
Irran Elisabeth,
Grohmann Andreas
Publication year - 2012
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201101265
Subject(s) - chemistry , copper , ligand (biochemistry) , crystallography , square pyramidal molecular geometry , reactivity (psychology) , electron paramagnetic resonance , bond length , macrocyclic ligand , yield (engineering) , stereochemistry , photochemistry , crystal structure , nuclear magnetic resonance , medicine , biochemistry , physics , receptor , alternative medicine , organic chemistry , pathology , materials science , metallurgy
The results of studies focussed on copper complexes of a variety of ligands with an NN 4 donor set are reported. The permethylated tetrapodal ligand 2 forms a complex with copper(I) which, upon reaction with dioxygen at –90 °C, yields a product having a bis(μ‐oxido)dicopper(III) core (“O‐type” product, 10 ), as inferred from UV/Vis and resonance‐Raman spectroscopic data. The UV/Vis spectrum of 10 has two bands at 300 and 404 nm, with extinction coefficients of 9400 and 10400 L mol –1 cm –1 , respectively. Resonance‐Raman spectra display two 16 O/ 18 O‐sensitive bands which, based on the isotopic shifts and the absolute frequencies, are attributed to the Cu–O stretching modes of the O‐type product. Complex 10 shows tyrosinase‐like activity, as its reaction with sodium p ‐ tert ‐butylphenolate at –90 °C in THF yields p ‐ tert ‐butylcatechol, in an ortho ‐hydroxylation reaction (yield: 30 %). Two new rigid tetrapodal pentadentate ligands (the “superpods” 3 and 4 ) can be synthesized by condensation of the primary polyamine 1 with paraformaldehyde. Their copper(II) complexes ( 5 and 6 ) have been spectroscopically characterized. As ascertained by X‐ray crystallography, 5 has the Cu II ion in a tetragonal‐pyramidal environment, with almost uniform Cu–N bond lengths (basal bonds: 2.052 Å and 2.070 Å; apical bond: 2.077 Å). No significant Jahn–Teller distortion is observed here. In 6 , the ligand acts as a multinucleating donor, which leads to the formation of a ladder‐like cluster of [Cu(μ 3 ‐OH)] units containing a total of two ligands, six copper(II) ions, four hydroxido ligands and eight trifluoroacetate ions. Two of the trifluoroacetate ions are non‐coordinating. Variable‐temperature magnetic susceptibility data are reported for this hexanuclear copper(II) cluster. Copper(I) complexes of 1 and 3 have been characterized and allowed to react with molecular oxygen, which caused the decomposition of the complexes. The IR spectra of the oxygenation products have bands at 1652 and 1632 cm –1 , respectively, which are absent in the spectra of 1 and 3 , suggesting that amine functions have been oxidized to imines.