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Rödel, Nicolas (2008): Beiträge zur Koordinationschemie der Aziridine, 2H-Azirine und Phosphirane. Dissertation, LMU München: Faculty of Chemistry and Pharmacy
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Abstract

This thesis contributes to the coordination chemistry of aziridines, 2H-azirines and P-mesitylphosphirane as ligands towards transition metals. The focus is set on transition metal halides and organometallic complexes of electron rich transition metals like for example W(0), Re(I), Rh(III), Ir(III), Ni(II), Pd(II), Pt(II), Cu(II) or Zn(II). Different strained mono- and bidentate three-membered ring systems are used as ligands. In many cases the purified complexes were characterized by routine analytical methods like NMR, IR, UV/Vis, elemental analysis and mass spectrometry and also by single crystal X-ray diffraction. Beyond the discussion of solid state structures, selected NMR- and IR-spectroscopic data of the complexes and the free ligands are compared and the coordination induced effects of various transition metals are discussed. In the case of aziridine and 2H-azirine ligands a remarkable stabilization of the ligand system was observed. This effect is rather surprising, if Lewis- or Brønsted-acid induced polymerization reactions of aziridine or transition metal induced rearrangement reactions of 2H-azirines are taken into consideration. The ionic chain polymerization mechanism of aziridines is obviously disfavoured compared to complexation and template reactions under the applied reaction conditions. Nevertheless when excess ligand stoichiometry was applied, metal mediated template dimerization reactions of aziridines yielding N-aminoalkylaziridine complexes could be observed. In collaboration with Budzisz et al. the cytotoxic activity of selected aziridine and 2H-azirine complexes towards cancer cells was studied and is presented in this work. A series of 2H-3-(4-R-C5H4)-azirine (R = H, Me, Cl, Br) derivatives with electron withdrawing and weak electron donating substituents were prepared and used as novel highly strained imine ligands in the coordination chemistry of zinc(II)- and palladium(II)halides as well as organometallic rhodium(III), iridium(III) and rhenium(I) complexes. In the 2H-3-arene-azirine ligand series a surprisingly strong reduction of the sigma-donor strength from methyl to chlorine substituents was observed. This effect is primarily due to the negative inductive effect of the halogeno substituent of the phenyl moiety. The high reactivity of the strained, monodentate 2H-3-phenyl-azirine ligand system towards nucleophiles was demonstrated by the reaction of zinc(II) and palladium(II)-azirine-complexes with alcohols like methanol and ethanol. Their nucleophilic attack yielded in the template dimerization of the azirine ligands in vicinal position to each other in the case of zinc(II) or ring opening reactions of the azirine ligands in trans position to each other in the case of palladium(II). Postulated mechanisms for both reactions are presented in this work. Four of the solvolysis products were characterized by single crystal X-ray diffraction. Finally the bulky three membered P-heterocycle P-mesitylphosphirane was prepared and used as ligand. It was possible to isolate two phosphirane complexes of ruthenium(II) and iridium(III). The iridium(III) complex was characterized by single crystal X-ray diffraction and exhibits interesting structural information concerning the three-membered ring geometry compared to analogous aziridine complexes. In summary a series of by the majority electron rich complexes of aziridines, 2H-aryl-azirines and P-mesitylphosphirane were synthesized. In many cases structural characterization by single crystal X-ray diffraction was possible and yielded manifold coordination geometries. Additionally promising results concerning the biological activity of selected ligands and complexes against a series of cancer cells are presented.