Ethylene vibrational coordinates

It is believed that this unique reaction is facilitated by the presence of the highly exposed and coordinatively unsaturated metal-metal bond in 10. The activity of the fulvalene hydride (3) as a catalyst for this reaction is also consistent with the belief that two, adjacent titanium centers are required. The IR spectrum of 3 after the reaction with ethylene shows no Ti—H stretching vibration suggesting that a titanium-olefin derivative (rather than the hydride) is the actual catalyst. 

These results are valid and apply for all addition reactions involving olefinic double bonds. Addition reactions are characterized by an increase in the number of normal modes of vibration. In this case the ethylene molecule has 12 normal modes of vibration while thiirane has 15. One of these, the CS stretching mode, coincides with the reaction coordinate and does not contribute to the isotope effect. Out of the net gain of two, the CCS bending mode is not sensitive to isotopic substitution and does not generate an isotope effect, but the twist of the CH2 group which... 

The trends in metal ion-ethylene binding energies in Table 5 can be analysed as functions of basis set, theoretical level and metal ion. In contrast to the proton affinity calculation described above where zero-point energy difference contributed more than 6 kcalmoP to the final binding energy (BE) value, the vibrational frequencies in Table 7 show that the electronic energy part of the complex coordination energy will be reduced only by about... 

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