Coupling of a High-Temperature Ion Trap Reactor with an Electron-Spray-Ionization Source for Reactions of Mass-Selected Organometallic Ions

Organometallics play a vital role in catalytic and synthetic processes. Understanding the individual elementary steps of the reactions of organometallic compounds is crucial for the development and rational design of new organometallic reagents and catalysts. Study of gas-phase reactions is one of the key approaches to probe the individual elementary steps under isolated and reproducible conditions. A series of investigations have been reported for the gas-phase reactions between organometallic ions and neutral molecules under room temperature conditions. However, studies about the reactions between organometallic ions and neutral molecules under heating conditions were very limited. In this work, an apparatus with an electrospray ionization source and an ion funnel trap that can couple with a high-temperature linear ion trap reactor was designed and built. The apparatus can be used to investigate the reactions between organometallic ions and neutral molecules under heating conditions. By using the apparatus, the adsorption reactions of Rh(PPh3)2+ + CO → Rh(PPh3)2CO+ and CuPPh3+ + CO2 → CuPPh3CO2+ under variable temperature conditions have been conducted. The experiments showed that the reaction rate constant of Rh(PPh3)2+ + CO increases first and then decreases with increasing temperature. In contrast, the rate constant of CuPPh3+ + CO2 decreases monotonically as the temperature increases. Density functional theory calculations indicate that the adsorption reaction of Rh(PPh3)2+ + CO → Rh(PPh3)2CO+ is subject to a small barrier, while CuPPh3+ + CO2 → CuPPh3CO2+ is barrierless, which is consistent with the experimentally observed temperature-dependent rate constants. The newly built apparatus can thus provide new kinetic information to address reaction mechanisms for organometallic ions.