The Molecular Structures and Conformational Preferences

D ensity functional theory calculations on E (SbM e2)2, E = S or Te, Me = C H 3, indicate that the equilibrium structures are syn-syn or near syn-syn conform ers with overall C2w or C2 symmetry. The calculations further indicate the existence o f syn-anti conform ers about 4 kJ m ol-1 (E = S) or 1 kJ m o l '1 (E = Te) above the equilibrium structure. G as electron diffraction data show that both conform ers are present in gaseous S(SbM e2)2, while the presence o f the syn-anti conform er in gaseous Te(SbM e2)2 is uncertain. The S b S and S b Te bond distances are 241.4(4) and 278.1(3) pm, respectively, the valence angles o f the synsyn conform ers are <SbSSb = 98.7(5)° and <SbTeSb = 91(2)°.