The Study Of Chiroptically Switchable Ni/Pd Complexes And The Aminohalogenation Of Olefins

1. The study of chiroptically switchable Ni/Pd complexes based on formation and cleavage of metal-ligand coordination bondsThe dissertation describes the design of asymmetric, pentadentate ligands. Upon coordination with Ni(Ⅱ) and Pd(Ⅱ), the corresponding diastereomeric complexes processing two new elements of chiralty:stereogenic axis and helix. It is important to note that due to stereo-congested structural characteristics of the corresponding Ni(Ⅱ) complexes the formation of diastereomeric products is highly stereoselective allowing preparation of only four out of eight possible stereochemical combinations. The diastereomeric transformation between products (Sa′,Mh′,Rc′) and (Sa′,Ph′,Rc′) occurs via intramolecular trans-coordination of two Ni-O bonds. This trans-coordination results in loss and regeneration of axial and helical chiralty with retention and inversion respectively. The stereogenic center in this case remains unchanged. As it follows from the crystallographic studies, in the solid state there is an obvious selectivity in Ni-O coordination. Generally, Ni/Pd prefers to coordinate with oxygen with high electronic density. In the variable NMR study, we observed four stable configurational complexes at low temperature (193 K). With the increase of temperature, the ratio of trans-coordination increases. For the first time, we calculate the energy difference between nickel/palladium and carbonyl coordinations. Considering the modular nature of this design, it is expected that modification of the three major "Phenone", "Acid" and "Amine" modules will allow for substantial structural and functional flexibility in preparation of this type of complexes making them more sensitive to external stimulus such as temperature, solvent or pH of the reaction medium. Furthermore, we could develop its application in nanoscale information technology as a new type of molecular switch.2. TsNHMe as nitrogen sources for aminohalogenationTo access new application of the product formed by aminohalogenation, introducing branch chain on the nitrogen sources is a feasible approach. After our careful investigation, we achieved the reactions with no catalyst. The reactions were very convenient to carry out at room temperature without the protection of inert gases and the starting materials were easily accessible. These bromoamino products have been characterized by 1H NMR,13C NMR, MS and IR.