MELISSA A. BAUDHUIN, PRAVEENKUMAR BOOPALACHANDRAN, SRIJAY S. RAJAN AND DOREEN G. LEOPOLD, Department of Chemistry, University of Minnesota, Minneapolis, MN 55455 .

We report the 488 nm photoelectron spectrum of the NbCr- anion. For the 2 Delta ground state of neutral NbCr, the short bond length (1.894 Å) and high bond energy (D0 3.0263(6) eV) measured by R2PI spectroscopy indicate high order multiple bonding. We find that the NbCr- anion has a 1 Sigma+ ground state, in which the "extra" electron occupies the (4d) delta bonding orbital, giving a 1 sigma21 pi41 delta42 sigma2 valence electron configuration and a formal bond order of 6. Low-lying excited states of NbCr (assigned as two 2 Sigma+ states) and NbCr- (3 Delta) are also observed. The spectra provide the electron affinity of NbCr, energies of the 2 Sigma+ and the 3 Delta excited states, vibrational frequencies for the NbCr and NbCr- ground states and for the 2 Sigma+ excited states, and (from Franck-Condon analyses) differences among the bond lengths of the observed states. These results are compared with our previous data for the Group 5/6 congeners NbMo, VCr, and VMo, and with DFT predictions. We also report results for ongoing experiments on the flow tube reactions of the Group V metals Nb and Ta with butadiene, and the vibrationally-resolved photoelectron spectra of some of the organometallic reaction product anions.