Infrared spectroscopy of mass-selected metal carbonyl cations

Abstract

Metal carbonyl cations of the form M ( CO ) n + are produced in a molecular beam by laser vaporization in a pulsed nozzle source. These ions, and their corresponding rare gas atom “tagged” analogs, M ( CO ) n ( RG ) m + , are studied with mass-selected infrared photodissociation spectroscopy in the carbonyl stretching region and with density functional theory computations. The number of infrared-active bands, their frequency positions, and their relative intensities provide distinctive patterns allowing determination of the geometries and electronic structures of these complexes. Cobalt penta carbonyl and manganese hexacarbonyl cations are compared to isoelectronic iron pentacarbonyl and chromium hexacarbonyl neutrals. Gold and copper provide examples of “non-classical” carbonyls. Seven-coordinate carbonyls are explored for the vanadium group metal cations (V +, Nb + and Ta +), while uranium cations provide an example of an eight-coordinate carbonyl.