|Ph.D Student||Karmel Isabell Sarah|
|Subject||Synthesis of Organoactinide Complexes Containing N-Donor|
Ligands and Their Application in Homogeneous
|Department||Department of Chemistry||Supervisor||Professor Moris Eisen|
|Full Thesis text|
__________________________________________________________________________ The use of actinide coordination complexes in catalytic organic transformations can be traced back to the early 1970s. Due to their high catalytic activity in various catalytic organic processes, as well as their often complementary reactivity as compared to main group and transition metal catalysts, organoactinide and actinide coordination compounds have received growing attention from the scientific community over the past four decades. Despite the large variety of catalytic reactions mediated by actinide compounds, reactions with oxygen containing substrates have long been excluded from actinide catalysis. Normally, it is well expected that due to their oxophilicity, actinide coordination complexes will be very prompt to form oxygen-metal bonds precluding actinide complexes to be active catalysts with oxygen containing substrates.
In this thesis the design of post-metallocene actinide catalysts with nitrogen donating ligand platforms, such as the amidinate, or the imidazolin-2-iminato motif is presented. The synthesis of actinide bis(amidinate) complexes, with an additional electron donating functionality on the amidinate ligand was accomplished by using salt metathesis reactions. The respective actinide bis(amidinate) complexes were successfully applied as active catalysts in the ring opening polymerization of the cyclic ester e-caprolactone, displaying moderate to high catalytic activities. In addition, a new class of actinide imidazolin-2-iminato complexes was synthesized and structurally characterized. Owing to the ability of the super-basic and highly nucleophilic imidazolin-2-iminato moiety to act as a 2s, 4p electron donor, the respective imidazolin-2-iminato actinide complexes display short An-N (An = U, Th) bonds and large, nearly linear An-N-C angles, suggesting a higher bond order than one for the An-N bond. Hence, these compounds exhibit a lightly decreased electrophilicity and oxophilicity, enabling a better catalytic performance in processes with oxygen containing substrates. We have investigated actinide imidazolin-2-iminato complexes in the ring opening polymerization of e-caprolactone, in which a uranium bis(imidazolin-2-iminato) complex displayed an unusual high catalytic activity. In addition, a series of mono(imidazolin-2-iminato) actinide complexes was investigated in the dimerization of aromatic, cyclic and branched aliphatic aldehydes, thus allowing for the first actinide-mediated asymmetric Tishchenko reaction between an aromatic and a cyclic, or branched aliphatic aldehyde. Furthermore, the scope of actinide mediated was further expanded using a mono(imidazolin-2-iminato) thorium (IV) complex. The thorium compound [(ImDippN)Th(N(SiMe3)2)3] was successfully used as pre-catalysts for the insertion of E-H (E = N, P, S) bonds into heterocumulene systems, such as carbodiimides, isocyanates, and isothiocyanates, displaying a high tolerance toward functional groups and heteroatoms, thus allowing for a wide scope of accessible products.