title: Substituent effects of beta-diketiminate ligands on the structure and physicochemical properties of copper(II) complexes.
abstract: Substituent effects of beta-diketiminate ligands on the structure and physicochemical properties of the copper(II) complexes have been systematically investigated by using 3-iminopropenylamine derivatives R1LR3H, R3-N=CH-C(R1)=CH-NH-R3, where R1 is Me, H, CN, or NO2, and R3 is Ph, Mes (mesityl), Dep (2,6-diethylphenyl), Dipp (2,6-diisopropylphenyl), or Dtbp (3,5-di-tert-butylphenyl). When the ligands with R3=Ph or Dtbp were treated with CuII(OAc)2, bis(beta-diketiminate) copper(II) complexes exhibiting distorted tetrahedral geometries were obtained, the crystal structures of which were nearly the same as each other regardless of the alpha-substituent (R1); dihedral angles between the two beta-diketiminate coordination planes are 62.5 +/- 1.2 degrees, and the Cu-N bond lengths are 1.959 +/- 0.008 A. The distorted tetrahedral structures are maintained in solution, but the spectroscopic features, especially gII values of the ESR spectra and the d-d bands of the absorption spectra, as well as the electrochemical behaviors of the complexes, are significantly affected by the electronic nature of R1. The ligands with R3=Mes and Dep, on the other hand, gave di(mu-hydroxo)dicopper(II) complexes, and their crystal structures as well as spectroscopic and electrochemical features have also been explored. Furthermore, the ligand with the more sterically encumbered aromatic substituent (Dipp) provided a mononuclear four-coordinate square planar copper(II) complex supported by one beta-diketiminate ligand and one didentate acetate ion. Thus, the beta-diketiminate ligands with a variety of substituents (R1 and R3) have been explored to provide coordinatively unsaturated (four-coordinate) mononuclear and dinuclear copper(II) complexes with significantly different coordination geometry and properties.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan.
authors.forename: Chizu
authors.initials: C
authors.lastname: Shimokawa
authors.forename: Seiji
authors.initials: S
authors.lastname: Yokota
authors.forename: Yoshimitsu
authors.initials: Y
authors.lastname: Tachi
authors.forename: Nagatoshi
authors.initials: N
authors.lastname: Nishiwaki
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ariga
authors.forename: Shinobu
authors.initials: S
authors.lastname: Itoh