ELECTRONIC SPECTRUM OF HEXAFLUORONICKELATE(4) ANION

The electronic spectrum of the hexafluoronickelate(IV) anion has been studied by diffuse reflection in Na2NiF6 and K2NiF6, between 4 and 45 kK. The weak absorptions at 12.9 and 16.0 kK and the stronger bands at 19.0 and 25.3 kK are assigned, respectively, to d-d transitions from a 1A1g(t2g6) ground state to 3T1g, 3T2g, 3T1g, and 1T2g(t2g5eg) states, and the intense bands at 30.8 and 38.9 kK, to π →eg excitations. The broad band at 19.0 kK shows marked vibrational fine structure which is attributed to the superposition of a symmetric α1g progression on the vibronically (t1u) allowed transition. Least-squares fitting of the d-d bands using the full Tanabe and Sugano strong-field matrices yields Dq = 2010 cm-1, B = 515 cm-1, and β = 0.43. The degree of covalency indicated, although exceptionally high for a fluoride complex, is not unexpected in view of the large formal charge on the metal. © 1969, American Chemical Society. All rights reserved.