Theoretical studies of cyclopropylsilylenes: The structures and stability of cyclopropylsilylene C3H5SiH

Ab initio molecular orbital calculations at the G2(MP2) level have been car ried out on cyclopropylsilylene C3H5SiH. Four equilibrium structures were l ocated. Like H2Si, the ground state Of C3H5SiH is singlet and the triplet i s the low-lying excited state. The singlet-triplet separation energy is 127 .9 kJ/mol. The cis-trans isomerization path of singlet cyclopropylsilylene was investigated by intrinsic reaction coordinate (IRC) calculations. The c alculations show that no gauche conformers exist along the potential energy curve of the cis-trans isomerization and the isomerization happens with a barrier of 30.1 kJ/mol. Changes (DeltaH and DeltaG) in thermodynamic functi ons, equilibrium constant K(T), and A factor and reaction rate constant k(T ) in Eyring transition state theory of the cis-trans isomerization were als o calculated. (C) 2001 John Wiley & Sons, Inc.