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Chemie mit superbasischen Guanidin-Elektronendonoren : Zusammenspiel und Konkurrenz zwischen Säure-Base-, Redox- und Koordinationschemie

Emeljanenko, Dimitri

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In this work reactions of guanidinyl-functionalised aromatic compounds 1,2,4,5-tetrakis-(N,N,N´,N´,-N´´,N´´,N´´´,N´´´-tetramethylguanidino)-benzene (1), 1,2,4,5-tetrakis-(N,N‘-dimethyl-N,N‘-ethyleneguanidino)–benzene (3) and 1,2-bis-(N,N,N´,N´-tetramethylguanidino)-benzene (2) with Cu(I), Ag(I) and Au(I) salts are explored. 1 and 2 are able to transfer two electrons to an acceptor and act as ligand by coordination with imine nitrogen atoms to metal centers, wich results in formation of binuclear complexes. Reaction of 1 with CuCl and CuCN leads to trigonal-planar coordination compounds 1(CuCl)2 and 1(CuCN)2. Oxidation of 1(CuI)2 with I2 leads to formation of semiconductive coordination polymer {[1(CuI)2][2I3]}n with band gap of 1.05 eV. Decomposition of this polymer is achieved with 1,10-phenanthroline with simultaneous oxidation of copper(I)-centers to Cu(II). A radical cationic complex [1(Cu2Cl2I2)][I3] is obtained by analogous reaction of 1(CuCl)2 with I2. DF-calculations show two Cu(II)-centers and one free electron located within the C6-backbone of the ligand. The strong oxidation agent Br2 allows the synthesis of [2Br1(CuBr2)2][CuBr4] by four electron oxidation of 1(CuBr)2, wich goes along with bromination of 1. The choice of electron acceptors determines the number of transferred electrons from the coordination compounds 1(CuBr)2 and 1(CuI)2. Formation of trigonal-planar complexes 2(CuX) (X = I, CN) is observed in case of using 2 as ligand. First coordination compounds of ligand 1 with AgX (X = Cl, Br, I) are obtained. Polarity of the solvent influences the progress of reaction. Using unpolar solvent toluene prefers coordination of Ag(I)-centers and formation monomer 1(AgCl)2, while in more polar acetonitrile coordination, oxidation and formation of polymeric structures is observed and product mixture of 1(AgCl)2, {[1][Ag4Cl6]}n and [1][2Cl] is obtained. Polymer compounds [1(AgBr)2]n and [1(AgI)2]n are synthesised by reaction of 1 with AgBr and AgI in acetonitrile. Pyrolysis leads to formation of graphite-like carbonitride phase with semiconducting properties. In methanol electrondonor nature of ligand 1 dominates over coordination character and oxidation of 1 in presence of AgCl and AgBr to dication 12+ is observed, while in presence of AgI oxidation is associated by coordination and dicationic units of 12+ are connected by silverhalogenide-cluster. The different properties of ligand 1 within the 1/AgX-system (X = Cl, Br, I) can be influenced by the selection of the solvent and/or halogenides, which offers an access to different products involving the guanidinyl-functionalised ligand 1. 1D-Chains of [1(AgBr)2]n and [1(AgI)2]n show different behaviour towards the oxidizing agents I2, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,3,5,6-tetrachlorobenzoquinone (TCQ) and tetracyanoquinodimethane (TCNQ). Polymer structures such as {[1][Ag5Br4I3]}n as well as donor-acceptor couple such as [1][2DDQ] are obtained. The formation of this compounds coincides with change of coordination geometry respectively dissociation of Ag(I)-centers from ligand. 1 acts as two-electron donor towards the oxidizing agent. First Au(I)-cyanomethylcomplex 3/[PPh3AuCH2CN]2 is obtained by reaction of 3 with AuPPh3Cl in acetonitrile. Coordination of Au(I) to guanidine-groups is not observed. The interplay of basic properties and steric feature of guanidine-groups allows 3 the deprotonation of the C-H-acidic compound acetonitril. The presence of 3 and AuPPh3Cl allows also deprotonation of phenylacetylene, 3-ethynylpyridine, 4-ethynylpyridine, 1,4-diethylylbenzene and 4-ethinyl-1,1´-biphenyle. Two reaction channels are observed. Redox-channel leads to formation of [3][2Au(RX)2] whereas the deprotonation channel results in formation of neutral Au(I)-complexes PPh3Au(RX). Favored linear geometry in all Au(I)-complexes is realized.

Item Type: Dissertation
Supervisor: Himmel, Prof. Dr. Dr. Hans-Jörg
Date of thesis defense: 12 April 2013
Date Deposited: 10 May 2013 08:14
Date: 2013
Faculties / Institutes: Fakultät für Chemie und Geowissenschaften > Institute of Inorganic Chemistry
Subjects: 540 Chemistry and allied sciences
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