title: Synthesis and characterization of completely delocalized mixed-valent dicopper complexes.
abstract: The multidentate ligands tris[(N'-tert-butylureayl)-N-ethyl)]amine (H(6)1) and 1-(tert-butylaminocarbonyl)-2,2-dimethylaminoethane (H(2)2) have been used to investigate the assembly and properties of complexes with Cu(1.5)Cu(1.5) units. The complexes [Cu(H(5)1)](2)(+) and [Cu(H2)](2)(+) have been isolated and structurally characterized by X-ray diffraction methods. [Cu(H(5)1)](2)(+) has a Cu(1.5)Cu(1.5) core, with each copper ion having square planar coordination geometry. The copper ions are linked through two mono-deprotonated urea ligands, which coordinate as mu-1,3-(kappaN:kappaO) ureate bridges to produce a Cu-Cu distance of 2.39 A. The remaining two urea arms of [H(5)1](-) form intramolecular hydrogen bonds, the result of which is to confine the Cu(1.5)Cu(1.5) unit within a pseudomacrocycle. The structure of [Cu(H2)](2)(+) lacks intramolecular hydrogen bonds and thus does not have a pseudomacrocyclic structure. However, the structural properties of the Cu(1.5)Cu(1.5) core in [Cu(H2)](2)(+) are nearly identical to those of [Cu(H(5)1)](2)(+). Both complexes exhibit rhombic EPR spectra at 77 K, which do not change upon cooling to 4 K. The optical spectra of [Cu(H(5)1)](2)(+) and [Cu(H2)](2)(+) are dominated by an intense band at approximately 700 nm. These spectral characteristics are consistent with [Cu(H(5)1)](2)(+) and [Cu(H2)](2)(+) being classified as fully delocalized (type III) mixed-valent species.
mesh_terms: D000588:Amines / Q000138:chemical synthesis* / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004563:Electrochemistry / Q000379:methods; D004578:Electron Spin Resonance Spectroscopy; D008024:Ligands; D008956:Models, Chemical; D008968:Molecular Conformation; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D010084:Oxidation-Reduction
chemical_list: C471927:1-(tert-butylaminocarbonyl)-2,2-dimethylaminoethane; D000588:Amines; D008024:Ligands; D009942:Organometallic Compounds; C471928:tris((N'-tert-butylureayl)-N-ethyl)amine; D003300:Copper