Synthesis, Spectroscopic Characteristics and Conductometric Investigation of New Tetrachloro- and Tetrabromoferrates(1-)

Synthetic pathways have been traced for new tetrachloro- and tetrabromoferrates(1-) of empirical formulae [AH][FeX4], (AH)2FeBr5, (AH)3Fe2Cl9 and (AH)4Fe2Cl10, where A stands for pyridine, quinoline and their derivatives, andX= Cl, Br. The spectroscopic evidence (IR, far-IR, Raman and UV-Vis) has shown that the FeX4 ions preserve their tetrahedral structure and that the nitrogen atom in the rings of pyridine and quinoline is protonated. On the basis of conductometric measurements relative stabilities of the anions were estimated in methanol (MeOH), dimethyl sulfoxide (DMSO) and dichloromethane (CH2Cl2), representing both polar (amphiprotic and protic) and non-polar solvents. Dissociation constants of the compounds were calculated based on the expanded Pitt's equation. Results of the conductometric measurements have been supported by electronic spectra.