Research Interests

Our research focuses on the reactions of gas phase transition metal ions.  One intriguing characteristic of these species is their ability to activate sigma bonds, resulting in species which occur as, or serve as models for intermediates in catalytic mechanisms.  In such mechanisms, typically unreactive (but often abundant) molecules such as methane are functionalized to yield useful products.  It is well-recognized that the outcomes of reactions involving bare transition metal ions can be profoundly influenced by the electronic configuration of the metal.  Clearly, the promise with respect to catalysis is that this electronic sensitivity might be exploited in order to selectively control formation of desired products.  Our contributions to the study of transition metal ion chemistry have focused on (1) characterizing state distributions of metal ions formed within a sputtering glow discharge, and (2) the application of this device to an examination of the reactions of several late transition metal ions with small hydrocarbons.  We have shown that the glow discharge is an intense and stable source of a wide variety of metal ions, and have examined factors influencing metastable excited state ion production in the glow discharge using electronic state chromatography (ESC).  In this method, different configurations of the ion are separated on the basis of their different mobilities in He.  We have demonstrated that relative state populations can be influenced by specific discharge conditions, including discharge pressure and working gas composition.  This suggests that different "synthetic methods" can be devised to obtain different metal ion configurations from the discharge, which can then be used to examine state-specific interactions of these sputtered ions with a variety of neutral species.  We have focused on the state-specific chemistry of several late transition metal ions with several small alkenes and alkanes.  This work has revealed that association products are formed primarily from ground state metal ions.  Observed bimolecular product channels are often adequately explained using accepted ideas regarding conservation of electron spin and required orbital occupancy.  However, some third-row systems exhibit more complex behavior, suggesting that other factors are governing the outcomes of these reactions.

Funding for this research has been provided by the National Science Foundation ,  Research Corporation and the Petroleum Research Fund of the American Chemical Society . Additional support has been provided by the National Center for Toxicological Research and the Arkansas Science and Technology Authority.

Selected Publications

Last updated January 13, 2003