Boron Carbonyl Analogues of Hydrocarbons: An Infrared Photodissociation Spectroscopic Study of B3(CO) n+ ( n = 4-6).

ABSTRACT

The boron carbonyl cluster cations in the form of B3(CO) n+ ( n = 4-6) are produced and studied by infrared photodissociation spectroscopy in the carbonyl stretching frequency region in the gas phase. Their geometric structures are determined with the aid of density functional theory calculations. The B3(CO)4+ cation is characterized to have a D2 d (OC)2B═B═B(CO)2 structure and 1A1 electronic ground state with a linear boron skeleton. The B3(CO)5+ cation is determined to have a chain boron framework with C2 v symmetry. The B3(CO)6+ cation is a weakly bound CO-tagged complex involving a B3(CO)5+ ion core. Bonding analysis reveals that B3(CO)4+ has a chemical bonding pattern similar to allene, while bonding in B3(CO)5+ is similar to that in allyl anion.