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

Pursuant to the exploration of dinuclear complexes, two naphthalene-based macrocyclic tetra imidazolium proligands were developed and characterized by a variety of different techniques. Both were envisioned to ditopically coordinate via the chelating Nheterocyclic carbenes, NHCs, and the naphthalene moieties serving to separate the metal centers and induce a discriminating binding pocket. To support that two palladium(II) ions spatially fit a ligand architecture comprising two fused benzene rings, the homoleptic paddlewheel complex resulting from 1,8-naphthyridine was studied. Indeed, support for such an arrangement and proximity-induced redox properties were found.
Encouraged by this result, the connectivity of the metal complexes resulting from the naphthalene-proligands was sought through three different strategies focusing on palladium(II) following its predictable coordination chemistry: the metalation adducts are all telling of single complex architecture, wherein the metal bears a macrocyclic NHC ligand. Additionally, a subtle intraligand difference concerning the NHC spacing results in the separation of either a square-planar complex, demonstrating accessible axial coordination sites, or a complex demonstrating a would-be unsymmetric binding pocket.
Of the former type, the chemistry concerning nickel(II) and palladium(II) complexes was explored from which surprisingly stable high-valent adducts were isolated; the bona fide Ni(III) and Pd(IV) complexes demonstrate surprising stability in air. Furthermore, I found data suggesting that a dichlorido Pd(IV) complex acts as an apt catalyst precursor for water-oxidation, specifically the oxygen-evolving reaction.
In closing, a chapter on my research exchange with Professor Theodore Betley at Harvard University, where I account for the synthesis of a triruthenium cluster, the cluster framework supported by a weak-field ligand, and each Ru bound by a phosphine.