I have a system for which I could not find the transition state using Gaussian09 corresponding to the experimental product formation. I have tried
route command fixing the two atoms in the (C-C) bond formation. It worked well showing the vibration in the bond formation in this direction (one -ve frequency of about -200), however, when i release the constraint and do a TS search, it gave a TS for a remote bond rotation (no longer along C-C bond formation).
I have tried to do a PES scan along the C-C bond forming direction varying the bond length from 3 Angstrom to 1.2 Angstrom, there is no maxima (but a minimum) within this range; the energy of the system only increases when the C-C bond approaches too close to each other.
What other ways can I try?