Towards an effective control of the electronic properties in Au(I)-complexes.
From basic principles to asymmetric catalysis.
by Elisa González Fernández
Date of Examination:2017-02-03
Date of issue:2017-02-21
Advisor:Prof. Dr. Manuel Alcarazo
Referee:Prof. Dr. Manuel Alcarazo
Referee:Prof. Dr. Lutz Ackermann
Referee:Prof. Dr. Claudia Höbartner
Referee:Prof. Dr. Franc Meyer
Referee:Prof. Dr. Dietmar Stalke
Referee:Dr. Inke Siewert
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EnglishThe dissertation is divided in two different parts, both related with gold(I) chemistry. In the first part, a new class of gold(I)-carbene complexes, the acyclic (amino)-(ylide)carbene (AAYCs) gold(I) chlorides, are presented together with a study of their reactivity. Their cyclic counterparts, (amino)-(ylide)carbenes, have been already reported as ligands to transition metals and present interesting properties, including an excellent σ-donor ability, keeping moderate π-acceptor attributes. Acyclic carbenes have significant stereoelectronic differences compared with cyclic scaffolds, together with the advantage of being easily accessible from the nucleophilic attack to certain metal-isonitrile complexes. Based on the synthesis of acyclic (diamino)carbene-gold(I) chlorides, we have developed a modular strategy for obtaining the AAYC-gold(I) chlorides through the nucleophilic attack of ylides to isonitrile-gold(I) chlorides. Moreover, the presence of additional functional groups on the carbenes side arm allowed their easy derivatisation, leading to the synthesis of heterobinuclear — bearing Rh(I) and Au(I) centres — and cationic AAYC-gold(I) complexes, together with an unprecedented Au(I)→Rh(III) and Au(I)→Ru(II) carbene transmetalation. In the second part of this thesis, TADDOL-based, α-cationic phosphonite ligands are developed and applied to the enantioselective synthesis of hexahelicene derivatives: helical, polyaromatic compounds with potential applications as ligands in asymmetric catalysis,liquid crystals with non-linear optical responses or molecular switches.The use of these novel class of cationic phosphonites as ancillary ligands allowed a highly regio- and enantioselective synthesis of substituted -carbohelicenes through a sequential Au(I)-catalysed intramolecular hydroarylation of achiral diynes. Key for these results are the modular structure of the chiral, cationic phosphonites, and the enhanced reactivity that they impart to Au(I)-centres after coordination due to the presence of a positive charge adjacent to the phosphorus atom.
Keywords: carbenes; gold catalysis; enantioselective catalysis; helicenes; cationic phosphonites