Chemie superbasischer Chelatliganden für H+, Cu+ und Mn2+

In Rahmen dieser Arbeit wurde ein neues Konzept im Design von Protonschwämmen entwickelt. Das Konzept der „Schwesinger Basen“ wurde mit dem Konzept der Proton-chelatisierenden Naphthalin-Protonenschwämme vereint. Der neue Protonenschwamm 1,8-Bis(hexamethyltriaminophosphazenyl)naphthalin HMPN basiert...

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Bibliographic Details
Main Author: Gauchenova, Ekaterina
Contributors: Sundermeyer, Jörg (Prof. Dr.) (Thesis advisor)
Format: Dissertation
Published: Philipps-Universität Marburg 2006
Online Access:PDF Full Text
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Table of Contents: The first part of this work is devoted to the synthesis and characterisation of the new bisphosphazene "proton sponges", while the second one to the investigation of coordination chemistry of copper and manganese cations supported by the peralkylated and NH-functionalised guanidines. It is shown that a combination of Schwesinger's phosphazene base concept and the idea of the disubstituted 1,8-naphthalene spacer yields a new superbase HMPN 1. This superbase represents the up to date most basic representative of this class of "proton sponges" as evidenced by the measured pKBH+ (in MeCN) value of 29.9 ± 0.2 and the theoretically estimated proton affinity (PA) of 274 kcal/mol. The second part of the work is devoted to the coordination chemistry of copper and manganese cations supported by the bis- and trisguanidines. Guanidines belong to the strongest neutral organic bases known. They are several orders of magnitude more basic than tertiary amines due to the excellent stabilisation of the positive charge over their resonance stabilised cations. The metallocomplexes based on such ligands have been extensively used to model the structure and reactivity of active sites in metalloproteins (biomimetic models), transfer oxygen after O–O bond cleavage, or use oxygen as H-atom acceptor, such hemocyanine, tyrosinase, and galactose oxidase. In contrast to the peralkyguanidines, the NH-functionalised guanidine ligands can form intramolecular hydrogen bridge (IHB) with axial bonded ligands in the metallocomplexes. This project was focused on the investigation of reductive activation of O2, PhIO, TsN3 and PhI(OAc)2 in the coordination slot of electron rich copper(I) complexes with and without IHB-interaction. It is found, that the end-on superoxo copper complexes [TMG3trenCu(O2)]+ and [DMEG3trenCu(O2)]+ are reversible formed by reaction of peralkylaguanidine copper(I) complexes with O2 at low temperatures. The progress of this reaction can readily be followed by UV-Vis, NMR or resonance Raman spectroscopy. The molecular structure of [Cu(TMG3tren)O2]SbF6 is confirmed by X-ray technique. The NMR investigations have shown that the end-on superoxo copper cation [TMG3trenCu(O2)]+ is paramagnetic. The estimated effective magnetic moment was counted for 3.02 B.M. (S = 1, triplet state). In order to isolate stable oxo and nitrene peralkylguanidine copper complexes the oxidation of [TMG3trenCu]+ and [DMEG3trenCu]+ has been carried out with TsN3 and PhIO. Surprisingly the reaction leads to selective hydroxylation and oxidative amination, respectively, one of the methyl groups of the ligand. For these reactions the „rebound“ mechanism is proposed on the basis of the experimental data and DFT calculations. The reaction with O2 proceeds differently for the peralkylated and the NH-functionalised guanidine copper(I) complexes. The NMR investigations have shown that the equilibrium is shifted to the side of starting materials in the case of the NH-functionalised guanidine copper(I) compounds. Moreover, the reaction of the NH-functionalised guanidine copper(I) complexes with PhIO or TsN3 is non-selective and the CH activation process does not take place. After oxidation of the NH-functionalised guanidine copper(I) complexes with PhI(OAc)2 the isolated Cu(II) products possess intra- and inter- molecular secondary IHB-interaction in solid state. Less sterically demanding bisguanidine ligands, as methyldi[2-(2N-(1,1,3,3-tetramethylguanidino))ethyl]amine and 2,6-di[2N-(1,1,3,3-tetramethyl-guanidino)methyl]-pyridine, have been used in the synthesis of crystalline dinuclear copper(I) complexes. These extremely sensitive to air products were fully characterised. The guanidine Mn(II) complexes have been synthesised in good yields by combining the dehydrated manganese(II) diperchlorate with one equivalent of peralkylated or NH-functionalised guanidine ligands in dry acetonitrile. The oxidation of the manganese(II) complexes with 0.5 equiv. of PhI(OAc)2 leads to the formation of Mn(II) acetate derivatives and Mn(IV) side products. This finding may be explained by the disproportion of an unstable Mn(III) acetate complex, which might be formed in the first step of reaction. The air-stable cobalt(II) complex [TMG3trenCo(MeCN)](ClO4)2 has been obtained in good yield by adding TMG3tren to acetonitrile solution of dehydrated cobalt(II) diperchlorate. This cobalt(II) complex was found to be paramagnetic with μeff of 3.93 B.M. (S = 3/2).