Binucleating Ligands: Design and Reactivity

Pincer ligands are a cornerstone of modern transition metal catalysis. An increasing interest in bimetallic catalysis motivated us to develop binucleating variants of these mononucleating ligands. Expanded variants of the PDI and PyBOX ligands were targeted, leading to the development of the Naphthyridine Diimine (“NDI”) and Naphthyridine Bisoxazoline (“NapBOX”) ligands, respectively. Metalation of NDI with appropriate metal precursors yielded Fe2, Co2 and Ni2 complexes which exhibited unique stoichiometric and catalytic reactivity. Metalation of the NapBOX ligand with nickel carboxylate salts yielded Ni2 complexes which were capable of catalyzing an asymmetric intermolecular [4+1] cycloaddition reaction between 1,1-dichloroalkene-derived vinylidenes and 1,3-dienes. Each of these processes were studied experimentally and computationally in order to understand the fundamental reactivity of organic substrates across metal-metal bonds.