Reactions of laser-ablated iron atoms and cations with carbon monoxide: Infrared spectra of FeCO+, Fe(CO)2+, Fe(CO)x, and Fe(CO)x− (x=1–4) in solid neon

Abstract

Laser-ablated iron atoms, cations, and electrons have been reacted with CO molecules during condensation in excess neon. The FeCO molecule is observed at 1933.7 cm−1 in solid neon. Based on isotopic shifts and density functional calculations, the FeCO molecule has the same Σ−3 ground state in solid neon that has been observed at 1946.5 cm−1 in a recent high resolution gas phase investigation [Tanaka et al., J. Chem. Phys. 106, 2118 (1997)]. The C–O stretching vibration of the Fe(CO)2 molecule is observed at 1917.1 cm−1 in solid neon, which is in excellent agreement with the 1928.2 cm−1 gas phase value for the linear molecule. Anions and cations are also produced and trapped, absorptions at 1782.0, 1732.9, 1794.5, and 1859.7 cm−1 are assigned to the linear FeCO−, Fe(CO)2−, trigonal planar Fe(CO)3−, and C3v Fe(CO)4− anions, respectively, and 2123.0, 2134.0 cm−1 absorptions to the linear FeCO+ and Fe(CO)2+ cations. Doping these experiments with CCl4 virtually eliminates the anion absorptions and markedly increases the cation absorptions, which confirms the charge identifications. Higher iron carbonyl Fe(CO)3, Fe(CO)4, and Fe(CO)5 absorptions are produced on photolysis.