On the propensity for electron transfer in high-energy collisions of iridium complex anions with cesium atoms

Iridium complex anions ( IrX 6 2 - , IrX 5 - , IrX 4 - , K + · IrX 6 2 - X = Cl, Br, and K + · IrCl 5 2 - ) were subjected to high-energy collisions with Cs atoms in an accelerator mass spectrometer. The experiments probed the complex anions’ propensity for electron attachment, which was only observed for IrCl 5 - , IrBr 5 - and K + · IrCl 5 2 - . These observations indicate that electron transfer is controlled by the relative stability of the Ir oxidation state and the availability of low-lying unoccupied molecular orbitals. Formation of IrX 5 2 - is notable since these ions are amongst the smallest molecular dianions observed in the gas-phase, while the K + · IrCl 5 3 - complex contains the smallest experimentally observed trianion.