Electronic Structure of Bis (tropolonato) nickel (II)

Abstract

111-NMR, X-ray photoelectron, and electronic absorption spectra have been measured for two kinds of complexes, monomer troNi. ( II ) and dimer (troNi (II))₂. which are formed between tropolone and nickel ( II ). From these spectral data together with MO calculations using a modified Pariser-Parr Pople approximation, the electronic and molecular structure of the above complexes has been clarified. In the solid state, the central metal ion of troNi( II ) takes a tetrahedral sp³ hybridization. On the other hand, in solution, the metal ion takes an octahedral d²sp³ hybridization, being linked with solvent or water (contained in the solvent) molecules. Furthermore in solution, the two tropolonato skeletal planes are coplanar, and are arranged transoid. The 402, 339 and 240.2 nm bands of troNi ( II ) observed in ethanol are assigned to the calculated ππ², ππ² and ire transitions, respectively. A weak band observed at around 674 nm is due to d-d transitions. The XPS Ni^2p band of troNi ( II ) is observed at 857.8eV, and that of (troNi(II))² at 858 eV. Both bands accompany with shake-up bands, indicating that the two complexes are paramagnetic in the solid states.