Multimetallic organometallic complexes: in pursuit of novel dinuclear complexes bearing N N-heterocyclic carbene ligands

Well-defined organometallic complexes comprising multiple proximal metals are highly attractive compounds, as the metal-proximity engenders unique properties in the context of, for instance, magnetism and electrochemistry. In this context, this PhD study has disclosed the synthesis and characterization of two novel macrocyclic tetra imidazolium proligands, which were envisioned to ditopically coordinate two proximal metal ions via chelating N-heterocyclic carbenes, NHCs. However, the resulting metal adducts are telling of a single complex architecture, wherein a single metal bears a macrocyclic tetra NHC ligand. Complexes bearing macrocyclic tetra NHC ligands are of increasing interest, as such complexes provide an electronically distinctive, yet similar, coordination environment to that of N-porphyrins, efficient in stabilizing reactive high-valent metal centers. In this context, the straightforward preparation of air and moisture-stable Ni(III) and Pd(IV) complexes are disclosed. Moreover, the Pd-complex(IV) appears to be catalytically competent in water oxidation (oxygen-evolving reaction) under mild conditions using environmentally benign and non-toxic hypervalent iodanes as sacrificial oxidants, in the absence of any irradiation.