language: en

DOI: 10.1002/zaac.200700513

[Synthese, Struktur und EPR-Untersuchungen von binuklearen Bis(N, N, N񮽙, N񮽙tetraisobutyl-N񮽙, N񮽙-isophthaloylbis(thioureato))-Komplexen des Cu II , Ni II , Zn II , Cd II und Pd II]

Synthesis, Structure and EPR Investigations of binuclear Bis(N, N, N񮽙, N񮽙tetraisobutyl-N񮽙, N񮽙-isophthaloylbis(thioureato)) Complexes of Cu II , Ni II , Zn II , Cd II and Pd II

Axel Rodenstein, Jan Griebel, Rainer Richter und Reinhard Kirmse*
Leipzig,
Institut für Anorganische Chemie der Universität

[Bei der Redaktion eingegangen am 15. November 2007.]

Abstract. The synthesis of binuclear Cu II -, Ni II -, Zn II -, Cd II - and Pd II -complexes of the quadridentate ligand N, N, N񮽙, N񮽙-tetraisobutyl-N񮽙, N񮽙-isophthaloylbis(thiourea) and the crystal structures of the Cu II - and Ni II -complexes are reported. The Cu II -complex crystallizes in two polymorphic modifications: triclinic, P1 ¯ (Z 񮽙 1) and monoclinic, P2 1 /c (Z 񮽙 2). The Ni II -complex was found to be isostructural with the triclinic modification of the copper complex. The also prepared Pd II -, Zn II - and Cd II -complexes could not be characterized by X-ray analysis. However, EPR studies of diamagnetically diluted Cu II /Pd II - and Cu II /Zn II -powders show axiallysymmetric g and A Cu tensors suggesting a nearly planar co-ordination within the binuclear host complexes. Diamagnetically diluted Cu II /Cd II powder samples could not be prepared. In the EPR spectra of the pure binuclear Cu II -complex exchange-coupled Cu II -Cu II pairs were observed. According to the large Cu II -Cu II distance of about 7, 50 A å small fine structure parameter D 񮽙 26 · 10 񮽙4 cm 񮽙1 is observed; T-dependent EPR measurements down to 5 K reveal small antiferromagnetic interactions for the Cu II -Cu II dimer. Besides of the dimer in the EPR spectra the signals of a mononuclear Cu II species are observed whose concentration is T-dependent. This observation can be explained assuming an equilibrium between the binuclear Cu II -complex (Cu II -Cu II pairs) and oligomeric complexes with " isolated " Cu II ions.

Keywords: Quadridentate N-acylbis(thiourea); Binuclear metal(II) complexes; Crystal structures; EPR investigations Einleitung