FT-IR STUDIES ON THE FORMATION OF TETRAZINC LONG STRAIGHT-CHAIN (EVEN-NUMBERED C6-C18) MU-4-OXO-HEXA-MU-CARBOXYLATES FROM THE CORRESPONDING BIS(CARBOXYLATO)ZINC COMPOUNDS

The bis(carboxylato)zinc(II) salts of even-numbered straight-chain fatty acids (C6-C18) were successfully prepared in boiling n-octane by neutralization. The mid-FT-IR spectra of n-octane solutions of the samples were recorded at 388 K. As a consequence of the dissolution process, the coordination of the carboxylate groups changed partially from bidentate to monodentate. The influence of water added to the solution on the solute was studied by means of FT-IR spectroscopy. Formation of Zn4O(RCOO)6 was detected, confirming the general validity of the earlier proposed mechanism of formation of the tetranuclear oxo-centered complexes of aliphatic carboxylic acids. The key factor is the presence of water in the system, which shifts the following equilibrium towards formation of the tetranuclear complex: 4Zn(RCOO)2 + H2O half arrow right over half arrow left Zn4O(RCOO)6 + (RCOOH)2.