Photoelectron velocity map imaging spectroscopy of group 14 elements and iron tetracarbonyl anionic clusters MFe(CO)4− (M = Si, Ge, Sn).

The heteronuclear group 14 M-iron tetracarbonyl clusters MFe(CO)₄⁻ (M = Si, Ge, Sn) anions have been generated in the gas phase by laser ablation of M–Fe alloys and detected by mass and photoelectron spectroscopy. With the support of quantum chemical calculations, the geometric and electronic structures of MFe(CO)₄⁻ (M = Si, Ge, Sn) are elucidated, which shows that all the MFe(CO)₄⁻ clusters have the M–Fe bonded, iron-centered, and carbonyl-terminal M–Fe(CO)₄ structure with the C_2v symmetry and a ²B₂ ground state. The M–Fe bond can be considered a double bond, which includes one σ electron sharing bond and one π dative bond. The C–O bonds in those anionic clusters are calculated to be elongated to different extents, and in particular, the C–O bonds in SiFe(CO)₄⁻ are elongated more. The Si–Fe alloy thus turns out to be a better collocation to activate the C–O bonds in the gas phase among group 14. The present findings have important implications for the rational development of high-performance catalysts with isolated metal atoms/clusters dispersed on supports. [ABSTRACT FROM AUTHOR]