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The subject of the presented work is the synthesis and investigation of dinitrosyl complexes of iron as well as carbonylnitrosyl complexes of cobalt with nitrogen containing chelating ligands.

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Academic year: 2021

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Abstract

The subject of the presented work is the synthesis and investigation of dinitrosyl complexes of iron as well as carbonylnitrosyl complexes of cobalt with nitrogen containing chelating ligands.

A series of Aryl-BIAN-irondinitrosyl [Fe(Aryl-BIAN)(NO)

2

] and Aryl-BIAN- cobaltcarbonylnitrosyl [Co(Aryl-BIAN)(CO)(NO)] complexes was successfully synthesised, in which the following Aryl-BIAN derivatives were used: Ph-BIAN, Mes-BIAN, 4-

i

Pr-Ph- BIAN, 2-Me-Ph-BIAN and 4-NO

2

-Ph-BIAN (Aryl-BIAN = Bis(N-arylimino)-acenaphthene).

The compounds were characterised using IR-, UV/Vis- and EPR spectroscopy as well as spectroelectrochemical UV/Vis-experiments. For [Fe(Mes-BIAN)(NO)

2

] and [Co(Mes- BIAN)(CO)(NO)] additional magnetic measurements were carried out. The nitrosyl ligand could be identified as NO

+

(IR-spectroscopy) in all cases. The Aryl-BIAN ligands are neutral (UV/Vis-absorption spectroscopy), hence the oxidation states of the metals are Fe

-II

and Co

-I

. UV/Vis-, electrochemical as well as spectroelectrochemical investigations on both the iron and the cobalt complexes showed the reversible reduction of the complexes to be ligand centred (diimine-π

*

), while the oxidations are metal centred.

The second part of this work deals with the synthesis and characterisation of iron dinitrosyl and cobalt carbonylnitrosyl complexes with various other α-diimine ligands. The α-diimines applied were bpy (2,2´-bipyridine), phen (1,10-Phenanthrolin), pyphen (Dipyrido[3,2-f:2´,3´- h]quinoxalin) and dppz (Dipyrido[3,2a:2´,3´-c]phenazin). The reversible reductions could again be proven to be ligand centred by performing electrochemical as well as UV/Vis- spectroelectrochemical measurements, while the oxidations were again metal centred.

A comparison of all systems investigated in this work and the well studied complexes with

diazabutadiene ligands (R-DAB) reveals significant differences in the ligand-metal interaction

between the strong donors (and poor -acceptors) such as bpy and phen and the excellent π-

acceptors (but poor -donors) such as Aryl-BIAN, R-DAB and dppz. The two extremely

electron rich systems [Fe(NO)

2

] and [Co(CO)(NO)] are very well suited for the assessment of

those effects.

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