44692-GB3
Advancing Organometallic Catalysis via Incorporating Weakly-Coordinating Carborane Anions into Cationic Half-Sandwich Electrophilic Complexes
The main goal of our research proposal is development of the reactive pro-catalytic and catalytic ruthenium-based systems with carborane counterion. The optimization of the synthetic conditions for the ruthenium carborane complexes leads us in search of the new protonating agents.
In addition to the protonation agents that we had synthesized previously (ether and toluene salts of carborane anions [H Ln]+ [carborane]-, where L is a solvent of choice ), we attempted and completed per-methylation of the carborane cage to yield CB11Me12 and H-CB11Me11 anions via reaction with methyl triflate in sulfolane (using CaH2 as a base). We subsequently synthesized the ether and toluene acids with it. Currently we are working on the protonation reactions using these new reagents with the ruthenium Cp*(NO) systems. Per-methylation of the carborane cage results in vastly improved solubility of the organometallic compounds. Currently we are working on optimization of the crystallization conditions for the ruthenium products. The carborane complexes appear to be reactive towards halogenated hydrocarbons abstracting chloride from them.
Ruthenium ditriflate analog of the carborane complexes oxidizes alcohols to yield aldehydes (or ketones). We continued the kinetic and thermodynamic variable temperature NMR experiments on this system. We have also characterized structurally by single crystal X-ray diffraction methods two products relevant to this reaction (in collaboration with Phillip Coppens group in SUNY Buffalo). First complex is a model intermediate for initial alcohol coordination step, -the chelate stabilized ethylene glycol complex, and second compound is an organometallic product of ruthenium center reduction, - the ruthenium-ruthenium double bond dimer. Both structures were reported in Acta Crystallographica publications this year, with undergraduate students listed as coauthors.
We have engaged in a fruitful collaboration with the group of Professor Ulrich Fekl in University of Toronto, interested in highly unsaturated platinum complexes with weakly coordinating anions, such as various derivatized carboranes. The hexa-bromocarborane anion acts as weak tripodal ligand for the platinum center in compound (3), as was reported in our recent publication in Canadian Journal of Chemistry. Currently we are planning to use per-methylated anions with even less coordinating properties in this system.
In the past year of funding cycle a total of four undergraduate students were involved in the projects, directly or indirectly. Phil Byers was a senior at the time and is now in Florida State University Ph.D. program in chemistry. John Dymon and Shawn Eady are currently chemistry and biochemistry juniors and both have plans for continuing their studies in graduate school. Cole Lechleiter is biochemistry major, an African American student, and was funded via SUMR program for the past summer. He has plans to continue his education in biochemistry research. John Dymon and Shawn Eady are also involved in a related project – on synthesis and characterization of low melting salts with weakly-coordination cluster carbon-boron anions. This research resulted in a publication in Dalton Transactions this year, which was among top-ten most accessed publications in Dalton fro the month of May 2008.
John Dymon has traveled to the ACS meeting in New Orleans (March 2008) for a poster presentation of our research. Last years SUMR scholar, biochemistry junior Jason Diaz, has presented his results at the ACS meeting in Philadelphia (August 2008). The P.I. participated in the International Conference on Coordination Chemistry (ICCC38) with a poster presentation. All participants have gained valuable experience through the involvement with the project and are looking forward to its' continuation.
