The goal of the proposed research plan is the preparation of nickel complexes as catalysts for the oxidation of hydrocarbons using environmentally friendly oxidants like molecular oxygen (O2) or hydrogen peroxide (H2O2). The complexes will be prepared using highly robust nitrogen-based ligand scaffolds and carbene N-heterocyclic systems. Different ligands with different architectures (from bidentate to pentadentate) will be used in order to evaluate the most suitable scaffold for nickel and several substrates will be used in order to test the activity of the prepared catalysts in oxidation reactions of inactivated organic compounds. Moreover, their ability to perform stereospecific reactions using more complicated targets (natural products) bearing several non-equivalent C-H bonds will also be tested. This subject is specially relevant and interesting due to the importance of selectively incorporate oxidized functionality into organic frameworkds. The performance of asymmetric oxdiation processes may be achieved by the use of chiral ligands. Moreover, the active species implicated in the oxidation processes will be studied. In this sense, the preparation of nickel complexes based on carbene N-heterocyclic ligands may allow the access to low-valent complexes (Ni0 or NiI) which may be capable of direct activation of molecular O2 leading to the formation and detection of Ni-O2 species which may be responsible for the oxidation reactions. Relevant aspects to be considered are their electronic structure, the reversibility of the interaction, the basicity and electrophilicity of these species and their ability to oxidize organic substrates. These Ni-O2 species may possess different oxidation profiles towards exogenous substrates depending on the ligand architecture.
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