Infrared Spectroscopy of Extreme Coordination: The Carbonyls of U+ and UO2+

摘要

Uranium and uranium dioxide carbonyl cations produced by laser vaporization are studied with mass-selected ion infrared spectroscopy in the C−O stretching region. Dissociation patterns, spectra, and quantum chemical calculations establish that the fully coordinated ions are U(CO)₈+ and UO₂(CO)₅+, with D_4d square antiprism and D_5h pentagonal bipyramid structures. Back-bonding in U(CO)₈+ causes a red-shifted CO stretch, but back-donation is inefficient for UO₂(CO)₅+, producing a blue-shifted CO stretch characteristic of nonclassical carbonyls.