Stoichiometric quantities of 3,5-di-tert-butylcatechol and aqueous ammonia react in pyridine solution to form 2-amino-4,6-di-tert-butylphenol. Under an atmosphere of dioxygen the aminophenol is oxidized to either the corresponding iminosemiquinone or iminobenzoquinone. In the presence of Cu(II) iminosemiquinone condensation with the aminophenol gives the Cat-N-SQ radical ligand obtained as the Cu(py)2(Cat-N-SQ) complex. Metal and ligand magnetic orbitals are orthogonal and couple ferromagnetically to give a S = 1 molecular spin state at temperatures up to 300 K. In nonpolar solvents the complex undergoes ligand oxidation and disproportionation to give Cu(Cat-N-BQ)2. Crystallographic characterization on crystals obtained as the i-propanol solvate [orthorhombic, C2221, a = 19.548(3) A, b = 24.536(5) A, c = 23.655(5) A, V = 11346(4) A3, Z = 8, R = 0.068] show that the expected Jahn−Teller distortion appears in the trans Cu−O lengths of the equatorial plane rather than for the axial Cu−N lengths. Reactions ca...

Studies on Aerobic Reactions of Ammonia/3,5-Di-tert-butylcatechol Schiff-Base Condensation Products with Copper, Copper(I), and Copper(II). Strong Copper(II)−Radical Ferromagnetic Exchange and Observations on a Unique N−N Coupling Reaction

Three octahedral complexes containing a (cis-cyclam)iron(III) moiety and an O,N-coordinated o-iminobenzosemiquinonate π radical anion have been synthesized and characterized by X-ray crystallography at 100 K:  [Fe(cis-cyclam)(L1-3ISQ)](PF6)2 (1−3), where (L1-3ISQ) represents the monoanionic π radicals derived from one-electron oxidations of the respective dianion of o-imidophenolate(2−), L1, 2-imido-4,6-di-tert-butylphenolate(2−), L2, and N-phenyl-2-imido-4,6-di-tert-butylphenolate(2−), L3. Compounds 1−3 possess an St = 0 ground state, which is attained via strong intramolecular antiferromagnetic exchange coupling between a low-spin central ferric ion (SFe = 1/2) and an o-imino-benzosemiquinonate(1−) π radical (Srad = 1/2). Zero-field Mossbauer spectra of 1−3 at 80 K confirm the low-spin ferric electron configuration:  isomer shift δ = 0.26 mm s-1 and quadrupole splitting ΔEQ = 1.96 mm s-1 for 1, 0.28 and 1.93 for 2, and 0.33 and 1.88 for 3. All three complexes undergo a reversible, one-electron reduction...

Octahedral (cis-cyclam)iron(III) complexes with O,N-coordinated o-iminosemiquinonate(1-) pi radicals and o-imidophenolate(2-) anions.

2-Amino-4.6-di-tert.-butyl-phenoxyl (1) reagiert mit Arylzinnhalogeniden unter Bildung 8-gliedriger paramagnetischer Heterocyclen (3–7). Der Reaktionsweg und die Eigenschaften, insbesondere die Sn-Hyperfeinstruktur der stabilen Radikale, werden untersucht.



Synthesis of Paramagnetic Tin Heterocycles



2-Amino-4,6–di-tert-butylphenoxyl (1) reacts with aryltin halides to give 8-membered heterocycles (3–7) which exhibit paramagnetism. The course of the reaction and the properties of these stable radicals, particularly of the Sn-HFS, are described.

mitbearbeitet von Fritz Stöcker). Synthese paramagnetischer Zinnheterocyclen

Specific features of the synthesis and structures of the complexes of Group 14 elements (Si, Ge, Sn, Pb) with o-iminoquinone ligands are discussed. The chemical reactions of the above indicated compounds accompanied by the transformation of the redox-active ligand in the coordination sphere of the complex- forming agent are considered.

Chemistry of Complexes of Group 14 Elements Based on Redox-Active Ligands of the o-Iminoquinone Type

Group 6 complexes M(ONO)2 (M = Cr, Mo, W; ONO = bis(2-oxy-3,5-di-tert-butylphenyl)amide) are prepared by the reaction of divalent metal halide precursors with Pb(ONOQ)2. Analogous complexes containing the 2,4,6,8-tetra-tert-butyl-1,9-dioxophenoxazinate ligand (DOPO) are prepared by protonolysis of chromocene with H(DOPOQ) or by reaction of Pb(DOPOQ)2 with M2Br4(CO)8 (M = Mo, W). The molybdenum and tungsten complexes are symmetrical, octahedral compounds for which spectroscopic data are consistent with M(VI) complexes with fully reduced [LCat]3– ligands. Quantitative analysis of the intraligand bond lengths, by comparison with literature standards, allows calculation of metrical oxidation states (MOS) for the ONO ligands. The MOS values of the tungsten and molybdenum complexes indicate that π donation from the ligand is weak and that differences between the ONO and DOPO ligands are small. In both the solid state and in solution, Cr(DOPO)2 is paramagnetic with localized quinone and semiquinone ligands bound...

Metal and ligand effects on bonding in group 6 complexes of redox-active amidodiphenoxides.

2-Amino-4.6-di-tert.-butyl-phenol (1) kann durch verschiedene Agentien in das entsprechende Phenoxyl 1a ubergefuhrt werden. Dieses Radikal unterliegt weiteren Reaktionen, bei denen schlieslich Phenoxazinsysteme entstehen. Der Reaktionsweg und die verschiedenen stabilen paramagnetischen Reaktionsprodukte werden untersucht.

Helga Bürk

Papers

ESR-Untersuchungen einer Modell-Phenoxazinsynthese