THE COMPLEXATION EQUILIBRIA OF CALCIUM ION IN ALL-FLUORINE ENVIRONMENT WITH OXYGEN-DONATING LIGANDS

Alojz Demšar, Franc Perdih, Andrej Petriè, Andrej Pevec and Saša Petrièek

Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerèeva 5, P.O.B. 537, SI-1001 Ljubljana, Slovenia; e-mail: alojz.demsar@uni-lj.si

Abstract

Calcium ion in [{(C₅Me₄Et)TiF₃}₄CaF₂] 1 is capable of increasing its coordination number from eight to nine by binding an additional ligand. The complexation equilibria of 1 with ligands tetrahydrofurane (THF), dioxane (diox) and hexamethylphosphoramide (HMPA) have been studied by variable temperature 19F NMR spectroscopy. The following )H and )S values for complexation reactions were found: -22.8(5) kJ mol-1 and -70.4(3) J mol-1 K-1 (THF); -22.7(8) kJ mol-1 and -67.9(5) J mol-1 K-1 (diox); -25(1) kJ mol-1 and -56.3(6) J mol-1 K-1 (HMPA); respectively.