Theoretical studies of mechanism of cycloaddition reaction between germylidene and formaldehyde

摘要

Mechanism of the cycloadditional reaction between singlet germylidene (R1) and formaldehyde (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 between singlet germylidene and formaldehyde is reaction (4), which consists of three steps: the two reactants (R1, R2) first form an intermediate INT1b through a barrier-free exothermic reaction of 28.1 kJ/mol; this intermediate reacts further with formaldehyde (R2) to give an intermediate INT4, which is also a barrier-free exothermic reaction of 37.2 kJ/mol; subsequently, the intermediate INT4 isomerizes to a heteropolycyclic germanic compound P4 via a transition state TS4, for which the barrier is 18.6 kJ/mol. The dominant reaction has an excellent selectivity and differs considerably from its competitive reactions in thermodynamic property and reaction rate. (C) 2007 Wiley Periodicals, Inc.