The electronic structures of the molecules (tBuO) 3M≡N (M = Cr, Mo, W) have been investigated with gas phase photoelectron spectroscopy and density functional calculations. It is found that the alkoxide orbitais mix strongly with the M≡N triple bond orbitais and contribute substantially to the valence electronic structure. The first ionization of (tBuO)3Cr≡N is from an orbital of a2(C3v) symmetry that is oxygen based and contains no metal or nitrogen character by symmetry. In contrast, the first ionizations of the molybdenum and tungsten analogues are from orbitais of a1 and e symmetry that derive from the highest occupied M≡N σ and π orbitais mixed with the appropriate symmetry combinations of the oxygen p orbitais. In this a1 orbital, the oxygen p orbitais mix with the highest occupied M≡N orbital of σ symmetry. This mixing reduces the metal character, consequently reducing the metal-nitrogen overlap interaction in this orbital. From computational modeling, the polarity of the M≡N bond increases down the group such that W≡N has the highest charge separation. In addition to investigation of the effects of the metals, the electronic influences of substitution at the alkoxide ligands have been examined for the molecules (RO)3Mo≡N (R = C(CH3)2H, C(CH3)3, and C(CH3)2CF3). The introduction of CF3 groups stabilizes the molecular orbital energies and increases the measured ionization energies, but does not alter the overall electronic structure. The bonding characteristics of the ( tBuO)3M≡N series are compared with those of organic nitriles.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry