Transition Metal Mediated Non-Directed C-H Functionalization

The structure and reactivity of organometallic species relevant to non-directed C- H activation and C-H functionalization are studied to inform the design of discrete pre- catalysts suitable for incorporation into supramolecular scaffolds. First, a study of transmetallation of hydrocarbyl ligands between transition metals demonstrates potential for dual-metal catalysis, in which one species cleaves C-H bonds and transfers the metallated fragment to a second metal suited for functionalization of the metal-carbon bond. Ligand modification of a rhodium (PNP) pincer complex gives rise to 100-fold rate enhancements toward non-directed C-H activation and this stoichiometric reactivity is leveraged to develop a catalytic method for non-directed C-H functionalization. During investigation of C-H activation with (PNP)Rh complexes, a heterobimetallic transition state analogue was isolated and characterized. Bonding analysis of the analogue demonstrates that the unusual geometry is supported by the same types of bonding interactions as those found in the putative transition state. Isolation and characterization of palladacycles coordinated by mono-protected amino acids (MPAA) reveals an unexpected MPAA-bridged di-palladium structure. Steady state kinetic analysis of Pd- MPAA catalyzed C-H functionalization, in particular the kinetic method of continuous variation, reveals that MPAA-bridged di-palladium complexes are responsible for MPAA- dependent rate acceleration and enantioinduction.