Electronic State-Specific Transition Metal ION Chemistry

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The importance of transition metal centers as catalysts for selective trans­ formations of small molecules into useful chemicals has prompted exten­ sive studies in the condensed phase. In the last decade or so , chemical analogues to these processes have also been investigated in the gas phase. The promise of the gas phase research is that more quantitative infor­ mation regarding the dynamics, kinetics, and thermochemistry of these processes can be obtained in a more controlled environment. A particularly active component of this gas phase research is the chemistry of atomic transition metal ions, which are conveniently studied by several types of mass spectrometric techniques (1-7). Although the relationship between this gas phase endeavor and condensed phase organometallic chemistry is still evolving , one area in which gas phase studies have contributed some insight into the reactivity at transition metal centers concerns the influence of the electronic state (8a). The abundance of low-lying electronic statcs is one of the features of transition metals that is integral to their ability to catalyze chemistry , since it allows a metal center to be a versatile reaction template in which many different types of species can bond and subsequently react. Unfortunately, this same feature makes it difficult to generate transition metals (atoms, ions , or complexes) in specific electronic states. Table I shows the extent of the problem for the first row transition metal ions. Since ion generation