Allylcalcium complexes : synthesis, reactivity and application in homogeneous catalysis

The main objective of the present work is to study preparation, coordination behavior and basic reactivity patterns of allylcalcium compounds. Examples for catalytic reactions of the resulting calcium compounds are given to evaluate the scope of applications. The first part describes the isolation of 1-alkenyl calcium complexes and their structural properties in solution and in the solid state. Model reactions with carbonyls and I2 reveal a distinct reactivity of bis(allyl)calcium towards electrophiles. The isolation of an alkylcalcium complex is briefly described. The second part presents the coordination behavior of bis(allyl)calcium in the presence of (aza)crown ethers. Despite isolation of an unprecedented crown ether complex bearing one monohapto- and one trihapto-allyl ligand, the basicity of the latter ligands leads to ether cleavage reactions. The decomposition pathway of the obtained adducts is described. The third part of this work reports on reactions of bis(allyl)calcium with Brønsted and Lewis acids and in situ generated allylcalcium monocations. Whereas ion pairs containing [Ca(C3H5)]+ are smoothly formed with several reagents, their isolation is prevented by ligand exchange equilibria towards the homoleptic species. A brief comparison of the activity in alpha-olefin polymerization is given. The parent compound bis(allyl)calcium is active in the polymerization of 1,3-butadiene but inactive in the polymerization of ethylene. Compounds bearing cationic [Ca(C3H5)]+ show no activity in the polymerization of 1,3-butadiene or ethylene. The fourth part focuses on the reactivity of bis(allyl)calcium towards pyridine and furan derivatives. A series of insertion and C-H bond activation products was isolated from reactions with N-heteroaryls and fully characterized. Mechanisms are studied and show a distinct balance between nucleophilicity and basicity of the employed allylcalcium compounds. The reactivity towards furans is found to result in undefined product mixtures. The last part of this work describes the reactivity of allylcalcium complexes towards dihydrogen, silanes and other hydrogenating agents. Special emphasis is given on the isolation a cationic calcium hydride cluster with a hypervalent hydridosilicate anion. The isolation of a ketyl radical complex hints at a redox non-innocent behavior of this ion pair. This unprecedented compound is active in hydrogenation of an 1-alkene with H2.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2011

Author dc:creator

• Jochmann, Phillip

Contributors dc:contributor

• Okuda, Jun

• info:eu-repo/classification/ddc/540
• Calciumion
• Erdalkalimetall
• Homogene Katalyse
• Polymerisation
• Katalytische Hydrierung
• Metallorganische Chemie
• Chemie
• Allylkomplexe
• organocalcium chemistry
• allyl complexes
• homogeneous catalysis
• hydrogenation

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-124482%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:63016