Hydrated cobalt(II) and nickel(II) trifluoromethanesulfonates have
been prepared by a previously reported procedure, and have been
characterized for the first time as [ Co(H₂O)₆] (CF₃SO₃)₂H₂O and [Ni(H₂O)₆] (CF₃SO₃)₂. These formulations are based on analyses,
near-infrared spectra, and on measurements of the ligand field
electronic spectra and the magnetic susceptibilities. The metal ions
are high-spin and octahedrally coordinated in both compounds.
Methods have been developed for the preparation of the pure
anhydrous cobalt(II) and the previously unknown nickel(II) trifluoromethanesulfonates
from the hydrates. By determination of the d-d
spectra and the magnetic moments, these are found to contain high-spin
octahedrally coordinated metal cations, and therefore contain
coordinated trifluoromethanesulfonate anions. The near-infrared
spectral absorptions of these anions have been observed. The magnetic
moment reported by previous workers for anhydrous cobalt(II) trifluoromethanesulfonate corresponds to the value found in this work
for the hydrate.
By vacuum line methods, pressure-composition data have been
obtained for the triethylamine-cobalt(II) and nickel(II) trifluoromethanesulfonate
systems. Breaks in the 25° isothermal phase diagrams show
that very unstable adducts containing two molecules of triethylamine
per metal ion are formed in each system. These could not be
isolated.
Various experimental methods for the preparation of quinuclidine
complexes were investigated. The one found to be successful involved
mixing, by Schlenk techniques, acetonitrile solutions of the anhydrous
metal trifluoromethanesulfonate and of an excess of quinuclidine,
evaporating the solvent, and removing the excess quinuclidine by sublimation.
The solid complexes obtained in this way were characterized
as [ Co(QUIN)₄] (CF₃SO₃)₂ and [ Ni(QUIN)₂(CF₃SO₃)₂] by their
analyses, ligand field spectra, magnetic moments, and the near-infrared
absorptions of the anions.
As expected, quinuclidine is found to be a better ligand than its
more sterically demanding analogue, triethylamine. The quinuclidine
complexes of cobalt(II) and nickel(II) trifluoromethanesulfonates are
much more stable. In the case of the cobalt complexes, the metal ion
has a greater ligation number for quinuclidine than for triethylamine.
In these solid salts and complexes, the trifluoromethanesulfonate ion shows a much greater tendency to coordinate than had been expected,
based on a previous study using it in aqueous solution
