Theoretical studies on the mechanism of formation of a heteropolycyclic germanic compound between dimethyl‐germylidene and ethylene

Mechanism of the cycloadditional reaction between singlet dimethyl‐germylidene (R1) and ethylene (R2) has been investigated with MP2/6‐31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by CCSD(T)//MP2/6‐31G* method. From the potential energy profile, it can be predicted that the dominant reaction pathway of the cycloadditional reaction of forming a heteropolycyclic germanic compound between singlet dimethyl‐germylidene and ethylene consists of three steps: (1) the two reactants (R1, R2) first form a three‐membered intermediate (INT1) through a barrier‐free exothermic reaction of 39.6 kJ/mol. (2) Three‐membered intermediate (INT1) isomerizes to an active four‐membered intermediate (INT2) via a transition state (TS2), for which the barrier is 50.1 kJ/mol. (3) Four‐membered intermediate (INT2) reacts further with ethylene (R2) to form a heteropolycyclic germanic compound (P3), which is also a barrier‐free exothermic reaction of 87.7 kJ/mol. This dominant reaction has an excellent selectivity and differs considerably from its competitive reactions in thermodynamic property and reaction rate. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010