Dinuclear copper(II) complexes of four new pyrazole-containing macrocyclic ligands are active catalysts in the oxidative coupling of 2,6-dimethylphenol

• Published in: Inorganica Chimica Acta Vol. 355; pp. 374 - 385
• Main Authors: Schuitema, Anna M, Aubel, Peter G, Koval, Iryna A, Engelen, Mireille, Driessen, Willem L, Reedijk, Jan, Lutz, Martin, Spek, Anthony L
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20-11-2003
• Subjects: Crystal structures; Dimethyl phenol; Dinuclear copper complexes; Macrocycle; Oxidative coupling; Crystal structures; Dinuclear copper complexes; Oxidative coupling; Dimethyl phenol; Macrocycle
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/S0020-1693(03)00362-1

Four new macrocyclic ligands of varying ring size, [22]py4pz, [22]pr4pz, [18]py2pz and [20]py2pz, containing four or two endocyclic pyrazole groups, form dinuclear copper compounds. The single crystal X-ray structures of [Cu(pr2pz)(ClO
4)
2] (
A), [Cu
2([22]pr4pz)Cl
4](MeOH) (
B), [Cu
4([18]py2pz)
2(μ-Cl)
4Cl
2]Cl
2 (
C) and [Cu
2([18]py2pz)(CH
3CN)
4(ClO
4)
2](ClO
4)
2(CH
3CN)
1.6 (
D), show the pyrazole groups and the amine nitrogens all to be involved in the coordination of the copper(II) ions. In the mononuclear compound
A the copper ion is in a distorted octahedral geometry, with the equatorial plane formed by four nitrogen donor atoms from the ligand and the axial positions occupied by two oxygen atoms from mono-coordinated perchlorate anions. In compound
B each copper ion is in a distorted square pyramidal environment, with the three ligand nitrogens and a chloride atom in the equatorial plane and another chloride atom in the axial position. The cation of compound
C contains four copper centers. Two bridging Cl atoms connect the two central copper atoms to form a centrosymmetric four membered ring. Two macrocyclic units are present in the cation, each containing two copper atoms bridged by a chloride atom. One copper is fivefold coordinated and the second copper is distorted octahedral. In compound
D both copper(II) ions are in a distorted octahedral N
5O environment, with the equatorial plane formed by the three ligand nitrogens and a nitrogen from an acetonitrile molecule. A second acetonitrile molecule and a mono-coordinated perchlorate anion are weakly bound in the axial positions. The copper nitrate compounds of these new ligands are to some degree active catalysts in the oxidative coupling of 2,6-dimethylphenol with molecular dioxygen to poly(2,6-dimethyl-1,4-phenylene ether).
Four new macrocyclic ligands of varying ring size, [22]py4pz, [22]pr4pz, [18]py2pz and [20]py2pz, containing four or two endocyclic pyrazole groups, form dinuclear copper compounds. The copper nitrate compounds of these new ligands are active catalysts in the oxidative coupling of 2,6-dimethylphenol to poly(2,6-dimethyl-1,4-phenylene ether). The single crystal X-ray structures of [Cu(pr2pz)(ClO
4)
2], [Cu
2([22]pr4pz)Cl
4](MeOH), [Cu
4([18]py2pz)
2(μ-Cl)
4Cl
2]Cl
2 and [Cu
2([18]py2pz)(CH
3CN)
4(ClO
4)
2](ClO
4)
2(CH
3CN)
1.6, show the pyrazole groups and the amine nitrogens all to be involved in the coordination of the copper(II) ions.