Structure and Reactivity of Copper Dipyridyl Carbinol- and Rhenium Diphosphine Complexes

Abstract

Two series of terphenyl-based ligands were designed and synthesized, and the reactivity of their transition metal complexes was examined in the context of small molecule activation. Ligands bearing pyridyl donors and pendant hydroxyl groups were synthesized in order to accommodate multiple copper centers with varying steric environments. Copper(I) complexes of these ligands were prepared and characterized, in which copper is coordinated only via the pyridyl nitrogen donors. Treatment of the Cu(I) species with O2 or deprotonation of the ligand followed by metallation with Cu(II) generates multinuclear copper cores supported by bridging alkoxides. Mono-, di-, tetra-, and hexanuclear copper complexes have been synthesized by changing the protonation state and backbone geometry of the ligand. The resulting copper complexes have been characterized by a variety of techniques including single-crystal X-ray diffraction and 1H NMR spectroscopy. Rhenium(I) carbonyl coordination chemistry was explored using a series of terphenyl diphosphine ligands with varying steric properties and substituents. Structural differences between complexes of the meta and para ligand variants have been characterized by single crystal X-ray diffraction and 31P-NMR spectroscopy. Cyclic voltammetry studies reveal differences in redox properties, though neither complex appears to exhibit catalytic activity under CO2. Subsequently, we investigate the chemistry of rhenium complexes of 2-methoxy-5-tert-butyl- or 2-methoxy-5- dimethylamino modified ligands.