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44692-GB3
Advancing Organometallic Catalysis via Incorporating Weakly-Coordinating Carborane Anions into Cationic Half-Sandwich Electrophilic Complexes

Anna S. Larsen, Ithaca College

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. One of these alternative new protonating agents has been synthesized in toluene and can be described as  [H(toluene)_n]⁺ [Carborane]^-.  It is an analog of the earlier described ether –carborane salt (synthesis shown). Protonated toluene salt reagent is expected to have superior reactivity compared to the currently used protonated ether analog due to the higher acidity of protonated toluene moiety.  Currently we are working on the resolution of the low solubility issue with this novel reagent. Another avenue that we are currently exploring involves the use of per-methylated CB₁₁Me₁₂ anion.

We developed efficient and simple procedure for the synthesis of [H+(ether)₂] carborane^-.  In this procedure no use of hydrogen chloride gas is needed any more.  Commercially available hydrogen chloride solutions in ether are used and problems with cannulation of carborane salts suspensions are alleviated.

Ruthenium ditriflate analog of the carborane complexes oxidizes alcohols. Kinetic and thermodynamic NMR experiments have been carried out to evaluate the role of triflate ion in this process. It appears that triflate counterion is likely to form close ion pairs in dichloromethane solution, and thus the triflate dissociation equilibria reported previously may not be described as simplistically. The effect of triflate overall concentration on the rate of the alcohol oxidation in our case is more complex.

The synthesis of the carborane complex of ruthenium is being constantly optimized. The identity of the major decomposition product is determined to be hexa-acetonitrile ruthenium (+ 2) complex paired with two carborane counter-ions.   Currently we are working on X-ray structural characterization of the main product of the protonation reaction (shown in the first frame).

There have been four undergraduate students involved in this project within past year and a half. KelLee Rich (IC chemistry senior) worked on NMR studies of triflate role in the alcohol oxidation reaction in summer of 2006 (supported by Research corporation grant). KelLee will be graduating with B.S. in chemistry in Spring of 2008 and is planning to enroll in ophthalmology program in New York City.  Ryan Wibby (chemistry B.S. graduate 2007, currently employed by Avion, Inc) has worked on general carborane anion synthesis in spring and summer of 2006, and presented his research results (concerning this and another research project in our laboratory) at the ACS meeting in Chicago in March of 2007.  More recently an outstanding minority student, Jason Diaz (IC chemistry junior) has worked on the synthesis of carborane complexes and NMR studies of their reactions (supported via SUMMR program). Jason has quickly mastered air-sensitive techniques with Schlenck and vacuum lines, and also worked in the new inert –atmosphere camera, that was recently purchased by our laboratory. John Dymon (IC chemistry sophomore) joined my group during his freshman year, worked in the laboratory in summer 0f 2007 and is making good progress in learning organometallic synthesis techniques. John has been very helpful in synthesizing and devitalizing carborane salts that are used in this and other projects in our lab. John has also helped to install and continues every-day maintenance of the solvent purification system that was purchased by Ithaca College with the partial support of the ACS PRF grant. John and Jason will be presenting at the next ACS national meeting in New Orleans in April of 2008.

The P.I. of this research project has participated in five conferences  since June 1^st of 2007:  National Science Foundation Workshop in Inorganic Chemistry (June 2006, WA) – with a talk concerning this project,  Gordon research Conference in Inorganic Chemistry (July 2006, RI) – as a section mediator and  presenting a poster on this research,  ACS National meeting (September 2007, CA) – presenting a poster on this project,  Gordon research Conference in Inorganic Reaction Mechanisms (February 2007, CA) – presented a poster on this project and was invited to give a talk, and  Gordon Research Conference in Inorganic Chemistry (July 2007, RI) – with a poster on related project.  During this conferences a number of interesting collaborations started through the initial contacts with professor LeeGrande Slaughter( Oklahoma State University),  professor  Ulrich Fekl  (University of Toronto),  professor Phillip Coppens (SUNY Buffalo), and others. 

 Overall, all the researchers involved have grown professionally and personally via various activities related to their participation in this research project.  We are looking forward with excitement to continuation of our work in this field.

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