Structures of tetrakis(trifluoromethyl)diphosphane and -diarsane: experimental and theoretical investigations

Several spectroscopic methods were used in studying the conformations of tetrakis(trifluoromethyl)diphosphane and -diarsane to determine the gauche effect. The first complex exists as trans conformer in the solid and as a mixture of about 70% trans and 30% gauche in the liquid and gaseous states based on its vibrational spectra. It has a trans-to-gauche ratio of 90:10 while the trans conformer of tetrakis(trifluoromethyl)diarsane has been detected in all phases.