Hydrogen singlet-triplet interaction

H, Me). Inclusion of relativistic effects was found to be important for results on the model to agree with experiment. For R = H, the calculated transition state was calculated to be close to the reactants, while for R = Me, the transition state is product-like. Both the ethyl and propyl products show an agostic interaction with a -hydrogen. A second study used DFT methods to explore the oxidative addition of the C-F bond in fluoromethane to unsaturated Rh(I) species modeled by Rh(X)(PH3)2 (R = H, Me, Cl). The activation barrier was found to correlate with the magnitude of the singlet-triplet splitting and to be lowered by the presence of r-donor ligands. ... 

It is interesting to note here that the value of the rate constant for DPC (14a), 1-NC (a-12), methoxycarbonylphenylcarbene (53), and FL (23) with O2 are 5 X 10 , (3.5 0.7) X 10 , 8.6 x 10 and (1.4 0.2) x 10 AT s-, respectively. The difference in the rate constants is not as large as that observed for the hydrogen atom abstraction rate constants for those carbenes (Table 9.9) and do not reflect the difference in the magnitude of AGst- The reason is probably because the rate constant of triplet carbenes is very fast and because the singlet states do not interact with triplet oxygen because of the spin restriction. 

Griesbeck, A.G. and Bondock, S. (2001) Paterno-Biichi reactions of allylic alcohols and acetates with aldehydes hydrogen-bond interaction in the excited singlet and triplet states Journal of the American Chemical Society, 123 (25), 6191-6192. 

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