MECHANISTIC, STRUCTURAL, AND VIBRATIONAL ASPECTS OF THE DIMERIZATION OF SILAETHYLENE

The dimerization of silaethylene to form 1,3-disilacyclobutane (1,3-DSCB) and 1,2-disilacyclobutane (1,2-DSCB) is studied using ab initio quantum mechanical techniques. The dimerization reaction leading to 1,3-DSCB is predicted to proceed through a concerted 2S + 2S mechanism due to a relaxation of the Woodward-Hoffmann rules for this case. With use of a double-zeta-basis set augmented with polarization functions on C and Si (DZ + d), at the single and double excitation coupled cluster (CCSD) level of theory, this reaction is predicted to be exothermic by 79.1 kcal/mol, and to have a barrier height of 5.2 kcal/mol. 1,2-DSCB is predicted to lie 19.8 kcal/mol higher in energy than 1,3-DSCB at the DZ + d self-consistent field (SCF) level of theory, and the dimerization reaction leading to 1,2-DSCB is predicted to proceed through a two-step mechanism involving a diradical intermediate.