194734-55-9Relevant academic research and scientific papers
New main-group and early transition-metal complexes of mono-pendant arm triazacyclononane ligands
Bylikin, Sergei Y.,Robson, David A.,Male, Nigel A. H.,Rees, Leigh H.,Mountford, Philip,Schroeder, Martin
, p. 170 - 180 (2007/10/03)
A family of new Group 3, Group 13 and early transition metal complexes of the previously described monoanionic, pendant arm macrocyclic ligands La, Lb and Lc are described where HLa = (3,5-dimethyl-2-hydroxybenzyl)-4,7-diisopropyl-1,4,7-triazacyclononane 1a, HLb = (3,5-di-tert-butyl-2-hydroxybenzyl)-4,7-diisopropyl-1,4,7-triazacyclonon ane 1b, and HLc = (3,5-di-tert-butyl-2-hydroxybenzyl)-4,7-dimethyl-1,4,7-triazacyclononane 1c. The ligand precusors 1a-c are quantitatively converted to the corresponding new potassium salts KLa, KLb and KLc 2a-c by reaction with potassium hydride in tetrahydrofuran (THF). An improved synthesis of HLc 1c is also reported. Reaction of KLa-c with Group 13 metal salts MCl3 (M = Al, Ga or In) gives monomeric derivatives [M(κ4-La-c)Cl2] 3-5 in good yields. The crystal structure of [In(κ4-Lb)Cl2] 5b has been determined and confirms the six-coordinate, cis-dichloride structures proposed for these complexes. Reaction of KLa-c with TlCl3 gives the asymmetric, binuclear analogues [Tl(κ4-La-c)Cl2]2 6a-c. Reaction of [Al(κ4-Lc)Cl2] 3c with AlCl3 gives the unstable, five-coordinate cation [Al(κ4-Lc)Cl]+ as its AlCl4- salt 8c. Reaction of KLa-c with MCl3, (M = Sc or Y) or [MCl3(THF)3] (M = Ti, V, Cr) in THF gives generally good yields of the Group 3 cis-dichloride derivatives [M(κ4-L1a-c)Cl2] (M = Sc 8a-c or Y 9b,c) and the early transition metal analogues [M(κ4-Lb,c)Cl2] (M = Ti 10b,c, V 11b,c or Cr 12b,c). Reaction of HL1a-c with TlOEt yields the monomeric, four-coordinate thallium(I) derivatives [Tl(κ4-L1a-c)] 13a-c as confirmed by the X-ray crystal structures of 13b and 13c. The Royal Society of Chemistry 2001.
Phenoxyl radical complexes of zinc(II)
Sokolowski, Achim,Müller, Jochen,Weyhermüller, Thomas,Schnepf, Robert,Hildebrandt, Peter,Hildenbrand, Knut,Bothe, Eberhard,Wieghardt, Karl
, p. 8889 - 8900 (2007/10/03)
A series of phenoxyl radical complexes of zinc(II) have been generated in solution and, in one instance, isolated as solid material (5) in order to study their spectroscopic features by EPR, resonance Raman, and UV-vis spectroscopy. They serve as model complexes for the active form of the copper containing fungal enzyme galactose oxidase. The complexes [Zn(L1H2)]BF4·H2O (1), [Zn(L2H2)]BF4·H2O (2), [Zn(L2H)] (2a), [Zn(L3)(Ph2acac)] (3), [Zn(L4)(Ph2acac)] (4), and [Zn(L4)(Me-acac)] (6) were synthesized from solutions of Zn(BF4)2·4H2O and the corresponding ligand (L1H3 = 1,4,7-tris(3,5-tert-butyl-2-hydroxybenzyl)-1,4,7-triazacyclononane; L2H3 = 1,4,7-tris-(3-tert-butyl-5-methoxy-2-hydroxybenzyl)- 1,4,7-triazacyclononane; L3H = 1,4-dimethyl-7-(3,5-di-tert-butyl-2-hydroxybenzyl)-1, 4,7-triazacyclononane; L4H 1,4-dimethyl-7-(3-tert-butyl-5-methoxy-2-hydroxybenzyl)-1,4,7 -triazacyclononane, Ph2acac- = 1,3-diphenyl-1,3-propanedionate, and Me-acac- = 3-methyl-2,4-pentanedionate). Complexes 2, 3·0.5 toluene·1n-hexane, and 4 were structurally characterized by single-crystal X-ray crystallography. An electrochemical investigation of these complexes in CH3CN and/or CH2Cl2 solution revealed that the coordinated phenolate ligands undergo reversible one-electron oxidations with formation of coordinated phenoxyl radicals. Synthetically, the microcrystalline, paramagnetic (μ(eff) = 1.7 μ(B)), solid material of [Zn(L4)(Ph2acac)]PF6 (5) was produced by one electron oxidation of 4 by 1 equiv of ferrocenium hexafluorophosphate in dry CH2Cl2. Oxidation of coordinated phenol pendent arms in 1, 2, and 2a occurs at significantly higher potentials and is irreversible. Electronic (UV-vis), electron paramagnetic resonance (EPR), and resonance Raman (RR) spectra of the radicals have been studied in solution and allow the description of the electronic structure of these coordinated phenoxyl radical complexes.
