AER/I Seminar

About the event

Speaker: Cole Fisher

Group: Dr. Jim Boncella

Title: Synthesis and Characterization of Ruthenium Complexes Bearing PNNNP and PNP Ligands and their Catalytic Applications

Abstract: Ruthenium complexes bearing pincer ligand have been utilized for many different transformations and are unique due to their metal ligand cooperation. Two common pincer ligands are the PNNNP and PNP ligands. The iPrPNHNNHP ligand reacts with [(cymene)RuCl2]2 to produce κ3-iPrPNHNNHPruCl2 that can react with two equivalents of NaHMDS in the presence of PMe3 to produce the double dehydrohalogenated complex κ3-iPrPNNNPRu(PMe3)2.  This compound is capable of undergoing 1,3-addition to the ligand N and Ru atoms. The 1,3-addition of alcohols such as water and phenol gave the expected products, κ3-iPrPNHNNPRu(OH)(PMe3)2 and κ3-iPrPNHNNPRu(OPh)(PMe3)2 respectively, with the water addition product existing in equilibrium with the starting materials. Attempts at 1,3-addition of alcohols that contained a proton beta to the hydroxyl group (MeOH, iPrOH) underwent beta-hydride elimination to form κ3-iPrPNHNNPRu(H)(PMe3)2. Attempts at generating the same complex from the 1,3-addition of H2 were also successful. Additionally, by utilizing the recently reported MesPNHP ligand and [(cymene)RuCl2]2 a monomeric κ3-MesPNHPRuCl2 complex can be produced, which after two dehydrohalogenations using NaHMDS yields κ5-MesPNHPRu(N2) as both the fac and mer isomers. Full conversion to the fac isomer is achieved by heating in benzene at 80 °C for 2 hours. The isolated fac- κ5-MesPNHPRu(N2) displays the ability to undergo hydrogen-deuterium exchange of the ortho methyl groups of the MesPNHP ligand with C6D6 over the course of 2 hours at 80 °C resulting in fac-d22-κ5-MesPNHPRu(N2). This process is shown to be reversible by heating the isolated fac-d22-κ5-MesPNHPru(N2) in proteo-benzene for 80 °C for 2 hours. The complex fac- κ5-MesPNHPru(N2) is additionally able to perform H-D exchange with other aryl compounds such as pyridine. Finally, the use of fac- κ5-MesPNHPru(N2) as a catalyst for H-D exchange was determined utilizing various aryl substrates with good functional group tolerance.