Gas-Phase Chemistry of Organotransition Metal Ions

Abstract

The gas-phase chemistry of many transition metal ions has been investigated by Fourier transform ion cyclotron resonance spectrometry (FTICR). Emphasis is on organometallic chemistry, including an application to geochronology, but inorganic and bio-inorganic systems have also been investigated. Quantum chemical calculations have been performed to address problems in interstellar chemistry and also traditional physical organic chemistry. Chapter I is concerned with the chemistry of ions OsOn+(n=0-4) with several small molecules, including methane. A wide variety of reactions are observed, including many that are archetypes for fundamental mechanistic processes in organometallic chemistry. In Chapter II, the differences in the gas-phase chemistry of Os+ and Re+ are applied to analytical problems associated with the 187RE-187 dating method, which is important in geology. Chapter III is a survey of the reactivity of third-row transition metal ions, with emphasis on the unusual reactions involving methane. Fundamental concepts that have proven useful in the interpretation of chemistry in the first and second transition series are also applicable in the third row. Chapter IV describes the gas-phase synthesis of positive and negative metalloporphyrin ions by reactions of metal-containing ions with porphine vapor. Chapter V presents some possibilities for transition metal catalysis in interstellar clouds. A very low value is calculated for the rate of radiative association of Fe+ and hydrogen atoms, suggesting that transition metal chemistry is not important in these systems. Chapter VI involves scaling the results of ab initio calculations in order to predict accurate singlet-triplet energy gaps in many substituted carbenes. Observed trends are rationalized using a synergistic bonding model. A simple relationship based upon electronegativity is presented to permit carbene singlet-triplet gaps to be computed using minimal resources, such as a hand calculator. Chapter VII deals with five different experimental issues that have arisen during FTICR studies of reactive transition metal ions. Difficulties, helpful techniques, and data analysis are discussed.