Coordination of niobium and tantalum oxides by Ar, Xe and O2: Matrix isolation infrared spectroscopic and theoretical study of NbO2(Ng)2 (Ng = Ar, Xe) and MO4(X) (M = Nb, Ta; X = Ar, Xe, O2) in solid argon

The combination of matrix isolation infrared spectroscopic and quantum chemical calculation results indicate that the NbO2 molecule is coordinated by two noble gas atoms in forming the NbO2(Ng)2 (Ng = Ar, Xe) complexes in solid noble gas matrixes. In contrast, the TaO2 molecule is not able to form similar noble gas complex. The niobium and tantalum dioxides further react with dioxygen to form the side-on bonded superoxo-dioxide complexes MO4 (M = Nb, Ta), which are coordinated by one argon atom in solid argon matrix. The coordinated Ar atom in MO4(Ar) can be replaced by O2 or Xe in forming the MO6 and MO4(Xe) complexes. The results indicate that the NbO2, NbO4 and TaO4 molecules trapped in solid noble gas matrixes should be regarded as the NbO2(Ng)2 and MO4(Ng) (Ng = Ar, Xe; M = Nb, Ta) complexes instead of “isolated” metal oxide species.