Infrared spectroscopy of Be(CO 2 ) 4 + in the gas phase: electron transfer and C-C coupling of CO 2 .

Beryllium-carbon dioxide cation complexes Be(CO 2 ) n + are produced by a laser vaporization-supersonic expansion ion source in the gas phase. Mass-selected infrared photodissociation spectroscopy supplemented by theoretical calculations confirms that Be(CO 2 ) 4 + is a coordination saturated complex that can be assigned to a mixture of two isomers. The first structure involves a bent CO 2 - ligand that is bound in a monodentate η 1 -O coordination mode. Another isomer has a metal oxalate-type C 2 O 4 - moiety with a C-C hemibond.