Development of Geometrically Constrained Ligand Architectures and Multimetallic Complexes for Catalytic Applications

The development of novel catalytic reactions for the production of value-added polymers and sustainable materials and feedstock are worthwhile endeavors. Attention has been focused on the bio-inspired design and creation of multinuclear complexes that display cooperative reactivity between proximal metal centers. However, more guidelines are needed for achieving bimetallic cooperativity and to direct reactivity towards products and polymers with desirable properties. This proposal concerns the design, synthesis, and applications of rigidly linked bimetallic assemblies featuring metal-ligand moieties that function as catalyst motifs. Significantly, these structures offer limited conformational flexibility, yet variations in M···M distances and orientations are accessible and amenable for controlling reactivity. The impact of various linker components, as well as steric effects that can impose preferred conformations, and their capacity to modify and tune reactivity with respect to activation and enchainment of substrates, will be addressed. It is envisaged that a convergent reaction environment between synergistic active sites can be generated. Diverse cooperative reactivity in polymerization catalysis and organic transformations using different catalyst motifs will be targeted, particularly those that normally proceed via bimolecular mechanisms. Ligand design strategies that can increase catalytic efficiency and alter substrate selectivity are proposed, and preliminary results in support of these (including catalytic proficiency and cooperativity for new bis-(M-ligand) frameworks) have been obtained. The underlying aim is to develop new bimetallic catalyst systems for the formation of important chemicals and polymers with unusual composition and characteristics.