Conductance Study of Tetraphenylboride Salts of Alkaline Earth Metals in Tetrahydrofuran

Abstract

SUMMARYThe conductance behavior of the tetraphenylboride salts of the alkaline earth metals (MB,) has been studied in the temperature range from + 20°C to -70°C in tetrahydrofuran (THF). A detailed knowledge of their dissociation into free MB+ and B-ions is desirable in order to better understand their influence in anionic polymerizations of e.g. styrene with alkaline earth metals as counterions. The thermodynamic parameters as well as the X+,-values for the respective salts are taken to indicate a double solvent separated ion pair structure for the calcium and strontium salt represented as B-//M,+//B-and a mixed ion pair structure for BaBz represented as B-, Ba2+/IB-. For MgB, an ion pair structure B-,Mg2+//B-is proposed at higher temperature changing to B-//Mgz +//B-at lower temperatures.