Separation of Boron Isotopes. VIII. BF3 Addition Compounds of Dimethyl Ether, Dimethyl Sulfide, Dimethyl Selenide, Dimethyl Telluride, Dibutyl Ether, and Ethyl Formate

Abstract

Studies were made of the physical and chemical properties of molecular addition compounds formed by BF3 and Group VIb donors. The dimethyl telluride complex was too unstable to exist at temperatures above −30°C. The freezing point of the 1:1 dimethyl selenide·BF3 compound was −43°C. From room temperature to its freezing point, the saturation pressure of the 1:1 dimethyl selenide complex was given by log10 P=9.945— (1824/T). The 1:1 butyl ether and ethyl formate complexes formed at 25°C but deteriorated slowly with the formation of noncondensible gases. The freezing points of these complexes were −30° and −8°C, respectively. Between room temperature and their freezing point, the saturation pressures of freshly prepared Bu2O·BF3 and HCOOEt·BF3 were given by logP=5.65— (1010/T) and logP=5.70— (1330/T), respectively. For the same temperature range, the equilibrium constant for the isotopic exchange reaction B10(g)+A·11BF3(l)=11BF3(g)+A·10BF3(l)was given by logKeq=(8.13/T) −0.0131, when A was dimethyl selenide and logKeq= (1.6/T)+0.0059, when A was dibutyl ether. Previously reported equilibrium constants for the Me2O and Me2S exchange reactions were redetermined: for Me2O, logKeq= (8.76/T) −0.0179, and for Me2S, logKeq= (10.7/T) − 0.0200. Related thermodynamic data were also computed.