Design, Synthesis and Applications of new cationic ligands of the 15th main group elements

by Hendrik Tinnermann
Doctoral thesis
Date of Examination:2017-11-01
Date of issue:2017-12-08
Advisor:Prof. Dr. Manuel Alcarazo
Referee:Prof. Dr. Manuel Alcarazo
Referee:Prof. Dr. Dietmar Stalke
Referee:Prof. Dr. Franc Meyer
Referee:Prof. Dr. Sven Schneider
Referee:Dr. Shoubhik Das
Referee:Dr. Franziska Thomas
Persistent Address: http://dx.doi.org/10.53846/goediss-6633

 

 

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Abstract

English

The dissertation focuses on the development of new cationic phosphines and their applications in transition metal catalyses. In pi-acid catalysis they proved their superiority in comparison with state of the art ligand systems described in literature. The pyridinium phosphines were prepared through a concise two step sequence (methylation and phosphination) from commercially available starting materials in excellent yields. We evaluated their electronic structure by CO-stretching frequency analysis of the corresponding Vaska-type complexes and by cyclic voltammetry. Furthermore, we have examined the solid state structure of the phosphine themselves and the corresponding metal complexes through x-ray analysis. The coordination behaviour to Au(I), Pt(II), Rh(I) and Pd(II) sources was also evaluated and the obtained complexes were applied in catalyses. The newly developed pyridinium phosphines show tremendous effects in the described reactions. For example in hydroarylations reaction times as short as a few minutes can be achieved, while classical ligands like triphenylphosphine need several hours to achieve similar conversions. This beneficial effect was shown in two platinum, one gold and one palladium catalysed reaction. After this promising results we then further improved the pyridinium phosphines through introduction of an aryl unit towards the nitrogen of the pyridinium moiety allowing secondary stabilizing interactions to the coordinated metal centre. The benefits of this additional stabilisation was shown along a [2+2] cycloaddition. In comparison to the previously described methyl substituted pyridinium phosphines the aryl substituted pyridinium phosphine gave even better results.
Keywords: metal organic chemistry; cationic phosphines; gold catalysis; platinum catalysis
 
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