PUB - Publikationen an der Universität Bielefeld

The ligand susan(6-Me) (susan(6-Me) 4,7-dimethyl-1,1,10,10-tetra(6 methyl-2-pyridylmethyl)-1,4,7,10-tetraazadecane) allows the synthesis of a peroxo complex that is only a transient species under catalytic conditions with the closely related ligand susan (susan - 4,7-dimethyl-1,1,10,10-tetra(2-pyridylmethyl)-1,4,7,10- tetraazadecane). For the synthesis of a peroxo complex - analogous to that of susan(6-Me) we present here the three air- sensitive complexes [(susan){(FeCl2)-Cl-II}(2)], [(susan){Fe-II(OTf)(2)}(2)], and [(susan){Fe-II(mu-OH)(2)Fe-II}](ClO4)(2) as potential precursors. [(susan){Fe-II(mu-OH)(2)Fe-II}](ClO4)(2) shows weak antiferromagnetic coupling and a g -16 EPR signal. Dissolving [(susan){Fe-II(OTf)(2)}(2)] in CH3CN forms Rsusan){Fe-II(CH3CN)(2)}(2)](4+) that shows a spin transition upon cooling as evidenced by UV-Vis, H-1 NMR, and Mbssbauer spectroscopies. In the UV-Vis-NIR spectra the combination of (i) the energy of the MLCT, (ii) the energy, and (iii) the splitting of the d-d transitions provide insight into the overall electron donation and into the different sigma-donor/pi-donor/pi-acceptor capabilities of the exogenous ligands. These experimental signatures provide insight into the molecular structures in solution e.g. during reactions with O-2.