Abstract
This dissertation presents the 57Fe Mössbauer spectroscopy study of 24 complexes of
Fe, Co, Ni and Pd with 3-ferrocenyl-1H-pyrazolyl-5-R and 3-ferrocenyl-5-R-pyrazolyl-2-
methylenepyridine (where R = Me or H). The study includes the synthesis of 12 novel
complexes of FeCl2, FeBr2, FeCl3 and CoCl2 fully characterized by elemental analysis, mass
spectrometry and infrared spectroscopy.
Mössbauer spectroscopy confirms the pyrazolyl-derivative of ferrocene, increases the
electron-density at the Fe-site while also facilitating the Fe-to-ring back-donated electrondensity.
The coordination of the ferrocenyl-pyrazolyl ligand to a metal reduces the electrondensity
at the ferrocenyl-site while increasing the electron-density at the coordination Fe site.
The electron-density at the coordination site is inversely proportional to the electronegativity
of the halide substituent, however the 5-position substituent on the pyrazolyl (R = Me or H)
has a greater effect on the electron density at the coordination site than the halides (Cl or Br).
For the pyridyl-pyrazolyl complexes, when R = Me, the reduced π-acceptor ability of
the pyrazolyl, increases the electron-density at the ferrocenyl-Fe centre and when R = H, the
electron-density at the coordination site increases. For coordination to metals other than Fe
(i.e., Co, Ni and Pd) the electron density at the ferrocenyl-Fe is also significantly reduced
upon coordination of the ligand to the metal.
An Fe(III) species found in most of the complexes was identified by Mössbauer
spectroscopy and mass spectrometry as the oxidative product [FeX4]-. These species arise
from the oxidation of ferrocene and the coordinating Fe-halides and seems to be a photooxidation
process occurring under standard lighting conditions, with possible contributions
from aerated solvents. The tetrahaloferrate species is not readily crystallized and the bulk
material of a sample may thus contain the species while being absent in the single-crystals.
M.Sc. (Chemistry)