Photoelectron Spectroscopic Characterization of the Niobium−Benzene Anion Produced by Reaction of Niobium with Ethylene

We report the 488 nm photoelectron spectrum of the NbC6H6 - anion produced by reaction with ethylene in a flow tube reactor equipped with a niobium cold cathode discharge source. The vibrationally resolved photoelectron spectrum of the mass-selected NbC6H6 - product is the same as that obtained upon reaction with benzene. Through comparison with the results of density functional calculations, the observed state of NbC6H6 - is assigned as the 3A1 ground state of an η6 Nb−benzene complex. Photodetachment transitions access the 2A1 ground state of neutral NbC6H6 and an excited state 0.713 ± 0.004 eV higher in energy, also assigned as a 2A1 state. Vibrational frequencies for the totally symmetric modes active in each transition are reported for the protonated and perdeuterated complexes. The electron affinity of NbC6H6 is 0.893 ± 0.006 eV.