Development, Application and Understanding of Synthetic Tools!

Transcription

1 Homogene Katalyse Wie kann man schneller, effizienter und umweltfreundlicher organische Moleküle und Polymere synthetisieren? Wie funktionieren diese Synthesewerkzeuge? Prof. Dr., Organometallic Chemistry, Alarich-Weiss-Str. 12, TU Darmstadt,64287 Darmstadt, Germany, 1

2 Development, Application and Understanding of Synthetic Tools! RESEARCH TOPICS superior synthetic tools = Development of new catalysts better synthesis = new approaches for the synthesis of organic molecules and polymers precise mechanism = mechanistic studies of transition-metal catalyzed transformations CATALYSIS Pd-catalyzed cross coupling reactions Ru-catalyzed Olefin Metathesis fluorescent dyes 2

3 What is Olefin Metathesis? A catalytic reaction which rearranges substituents around a carbon-carbon double bond. see: 3

4 fast and low-loading RCM catalysis 100 ppm 88% 100 ppm 89% 15 ppm 91% 50 ppm 89% P. Kos, R. Savka, H. Plenio, Adv. Synth. Catal. 2013, 355,

5 Research Topic: Polymers switched ROMP E/Z = 0.64 E/Z = 0.85 Stereoblock co-polymers with distinct materials properties can be synthesized using redox-switchable catalysts for ring-opening metathesis polymerization L. H. Peeck, S. Leuthäußer, H. Plenio, Organometallics 2010, 29, 4339; doi: /om100628f 5

6 Research Topic: Renewables Ethenolysis of natural rubber and tire rubber natural rubber cis-polyisoprene Hevea brasiliensis n The ethenolysis of natural rubber or tire rubber granulate leads to the depolymerization of the polymer, resulting in the facile formation of small terpenes, which might be suitable for the synthesis of fragrances. n [Ru] -catalyst +ethene On the ethenolysis of end-of-life tire granulates S. Wolf, H. Plenio, Green Chem. 2013, 15, 31;

7 organic solubles obtained after ethenolysis of ELT powder [Ru] 80 o C 7 bar ethene toluene 10 g of ELT fest yield up to 5 g of organic solubles flüssig 10 g of ELT require 0.04 g of ruthenium complex 7

8 Research topic: Fluorescent dyes Tagged catalyst complexes Transition metal complexes tagged with fluorescent dyes can be used to monitor an ongoing catalytic transformation via fluorescence spectroscopy or microscopy down to the level of individual molecules. T. Vorfalt, K.-J. Wannowius, V. Thiel, H. Plenio, Chem. Eur. J. 2010, 16, 12312; doi: /chem

9 Research Topic: Mechanism Understanding how catalysts work. Progress in catalysis critically relies on detailed mechanistic understanding. The development of olefin metathesis over the last decades from ill-defined, low-activity catalysts to powerful synthetic tools is an excellent example for this. On the Mechanism of the Initiation Reaction in Grubbs-Hoveyda Complexes V. Thiel, M. Hendann, K. J. Wannowius, H. Plenio, J. Am. Chem. Soc. 2012, 134, 1104; 9

10 k obs (s -1 ) absorbance absorbance Research Topic: Mechanism Understanding how catalysts work nm] M [2+2] M CH 2 M M [2+2] absorbance at 377 nm equaton y = A1*exp(-x/t1) + y0 R^ value error y E-4 A t time (s) [BuVE] (mol L -1 ) k obs = a [olefin]/(1+b [olefin]) + c [olefin] The activation of precatalysts leads to the generation of a catalytically active species. Analysis of initiation kinetics with time-dependent spectroscopic techniques provides a clearer picture of the elementary steps of precatalyst activation. 10

11 Research topic: Sensors Fluorescent paper strip based H 2 -detection Synthese a) b) c) a) plain paper strip b) paper strip impregnated with a solution of complex 8b c) the same strip following exposure to H 2 = fluorescent! P. Kos, H. Plenio, Angew. Chem. Int. Ed. 2015, 54, DOI: /anie