University thesis:
Dissertation, Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2021
Footnote:
Description:
Summary Aiming towards more sustainable chemistry, the development of efficient catalysts for the valorization of bulk and fine chemicals is a vivid area of research. Palladium, as one of the central metals for catalytic transformations, has received great attention during the last decades. However, breakthroughs such as the synthesis of terminal imido complexes, which could allow for the direct n-selective amination of alkanes or the isolation of the proposed active species in palladium(0–II) catalysis with PEPPSITM, remained elusive. The lack of these structures limits our understanding of their chemical properties. This work focused on the development of (a) the first isolable palladium terminal imido complex and (b) on the isolation of a palladium(0) complex which models the elusive active species of palladium(0–II) catalysis. First Terminal Palladium Imido Complex In a detailed computational study, the stability of palladium terminal imido complexes with common ligand systems was investigated. In particular, the influence of ancillary ligands and imido substituents was examined with respect to the electronic ground state and the reactivities of these compounds. This study enabled the deduction of general trends concerning the ideal properties of the ligand system to stabilize a terminal imido complex. For instance, the high valent palladium(IV) imido complex should be best stabilized by a strongly donating and chelating ligand. For palladium(II) terminal imido complexes CAAC ligands with strong sigma-donor and pi-acceptor properties in combination with electron withdrawing imido substituents have been predicted to be an excellent choice for the stabilization of terminal imido complexes with populated pi-antibonding HOMO and singlet ground state. Based on the insights gained from the computational considerations, a synthesis was developed and the first palladium(II) terminal imido complex was successfully isolated. Characterization confirmed the anticipated closed shell d 8 complex with a pi-antibonding HOMO ...