Infrared Photodissociation Spectroscopy of Mass-Selected Heteronuclear Iron–Copper Carbonyl Cluster Anions in the Gas Phase

Abstract

Mass-selected heteronuclear iron–copper carbonyl cluster anions CuFe­(CO)_<i>n</i>^– (<i>n</i> = 4–7) are studied by infrared photodissociation spectroscopy in the carbonyl stretching frequency region in the gas phase. The cluster anions are produced via a laser vaporization supersonic cluster ion source. Their geometric structures are determined by comparison of the experimental spectra with those calculated by density functional theory. The experimentally observed CuFe­(CO)_<i>n</i>^– (<i>n</i> = 4–7) cluster anions are characterized to have (OC)₄Fe–Cu­(CO)_<i>n</i>−4 structures, each involving a <i>C</i>_3<i>v</i> symmetry Fe­(CO)₄^– building block. Bonding analysis indicates that the Fe–Cu bond in the CuFe­(CO)_<i>n</i>^– (<i>n</i> = 4–7) cluster anions is a σ type single bond with the iron center possessing the most favored 18-electron configuration. The results provide important new insight into the structure and bonding of hetronuclear transition metal carbonyl cluster anions