Molecular Structure and Conformational Preferences of Trimethyl Phosphorotrithioite,P(SMe)_3,Evaluated by Gas-Phase Electron Diffraction and Quantum Chemical Calculations

摘要

Free P(SMe)_3 molecule was studied by gas electron diffraction (GED) and by B3PW91/6-311+G* (DFT) and MP2/6-31+G* calculations.Each conformer is characterized by three dihedral angles tau(CSPlp),where lp denotes the direction of the lone electron lone pair on the P atom.DFT calculations indicate that the most stable conformer is an anti,gauche+,gauche- (ag+g-) conformer of C_s symmetry;the next are the ag+g+ (DELTAE = 2.5 kJ mol~(-1)),g+g+g+ (DELTAE = 5.2 kJ mol~(-1)),and aa+g+ (AE = 12.5 kJ mol~(-1)) conformers.The MP2 calculations give the similar order,with the relative energies of 0.3,4.3,and 10.6 kJ mol~(-1),respectively.The experimental GED data agree well with the presence of only two conformers:X,(ag+g+) = 80(20)% and X(ag+g-) = 20(10)%.