|M.Sc Student||Andrea Tamer|
|Subject||Terminal Alkynes Dimerization, Hydroamination and Coupling|
with Isonitriles, Promoted by Organouranium
|Department||Department of Chemistry||Supervisor||Professor Moris Eisen|
In this work we present the studies of various catalytic reactions mediated by organoactinide complexes. This family of complexes proved to be good catalysts toward diverse reactions such as oligomerization, hydroamination, hydrosilylation of terminal alkynes, isomerization of a-olefins and others. However, there is a lack of information concerning their catalytic activity on more sophisticated systems such as diyne, and also on demanding organic transformations such as the 1,1-insertion of isonitriles to terminal alkynes.
Here we describe the investigation we performed using two different organouranium complexes; the first is a cationic complex [(Et2N)3U]+[BPh4]-, whereas the second is the neutral complex Cp*2UMe2 (Cp* = pentamethylcyclopentadienyl). We succeeded to crystallize the neutral complex and to characterize it by X-ray diffraction analysis and found that it crystallizes in tetragonal space group I41/a.
The cationic complex catalyses the dimerization of non-activated terminal diynes regioselectively and produces the geminal dimer as a major product with traces of higher oligomers. Kinetic studies showed first order dependence on the catalyst and the diyne n= k[catalyst]1[diyne]1. A plausible mechanism was suggested.
The hydroamination of methylenedianiline by the cationic complex generates the geminal E- mono and di-hydroamination products regioselectively.
With the cationic catalyst the trans mono-insertion product between terminal alkynes and tBuNC was observed as the major product. With Cp*2UMe2, the double insertion of two equivalents of isonitrile with one equivalent of terminal alkyne was observed beside the previously mentioned mono-insertion product. Here we present a plausible mechanism for both the mono and double insertion products.