Cationic indenylnickel complexes bearing a 1,5-cyclooctadiene ligand: Synthesis and characterization

Abstract

The reaction of [Ni(η-1-R-Ind)2] (R=H, Me) with one equivalent of 1,5-cyclooctadiene (COD), in the presence of a stoichiometric amount of HBF4 (in Et2O), at low temperature, afforded the corresponding cationic [Ni(η-1-R-Ind)(η4-COD)]BF4 in high yields. In the solid state, these complexes showed a slightly distorted pseudo-square-planar geometry around the metal centre. In solution, 1H NMR spectra showed the existence of a fluxional process involving the 1,5-cyclooctadiene ligand. This process was investigated by DFT calculations and the results exclude the possibility of η5-indenyl rotation.