Quadruple bonding between iron and boron in the BFe(CO)3- complex.

While main group elements have four valence orbitals accessible for bonding, quadruple bonding to main group elements is extremely rare. Here we report that main group element boron is able to form quadruple bonding interactions with iron in the BFe(CO)3- anion complex, which has been revealed by quantum chemical investigation and identified by mass-selected infrared photodissociation spectroscopy in the gas phase. The complex is characterized to have a B-Fe(CO)3- structure of C3v symmetry and features a B-Fe bond distance that is much shorter than that expected for a triple bond. Various chemical bonding analyses indicate that the complex involves unprecedented B≣Fe quadruple bonding interactions. Besides the common one electron-sharing σ bond and two Fe→B dative π bonds, there is an additional weak B→Fe dative σ bonding interaction. This finding of the new quadruple bonding indicates that there might exist a wide range of boron-metal complexes that contain such high multiplicity of chemical bonds

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

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

Infrared Photodissociation Spectroscopy of Mass Selected Homoleptic Copper Carbonyl Cluster Cations in the Gas Phase

Infrared spectra of mass-selected homoleptic copper carbonyl cluster cations including dinuclear Cu₂(CO)₆⁺ and Cu₂(CO)₇⁺, trinuclear Cu₃(CO)₇⁺, Cu₃(CO)₈⁺, and Cu₃(CO)₉⁺, and tetranuclear Cu₄(CO)₈⁺ are measured via infrared photodissociation spectroscopy in the carbonyl stretching frequency region. The structures are established by comparison of the experimental spectra with simulated spectra derived from density functional calculations. The Cu₂(CO)₆⁺ cation is characterized to have an unbridged <i>D</i>_3<i>d</i> structure with a Cu–Cu half bond. The Cu₂(CO)₇⁺ cation is determined to be a weakly bound complex involving a Cu₂(CO)₆⁺ core ion. The trinuclear Cu₃(CO)₇⁺ and Cu₃(CO)₈⁺ cluster cations are determined to have triangle Cu₃ core structures with <i>C</i>₂ symmetry involving two Cu­(CO)₃ groups and one Cu­(CO)_<i>x</i> group (<i>x</i> = 1 or 2). In contrast, the trinuclear Cu₃(CO)₉⁺ cluster cation is determined to have an open chain-like (OC)₃Cu–Cu­(CO)₃–Cu­(CO)₃ structure. The tetranuclear Cu₄(CO)₈⁺ cluster cation is characterized to have a tetrahedral Cu₄⁺ core structure with all carbonyl groups terminally bonded