Spin-forbidden reactions

[3] When a reaction converts a metal from a singlet to triplet state (or vice versa): Strong spin-orbital coupling can satisfy the 2nd condition.

Potential Energy Surfaces that are adiabatic rely on the use of the full electronic Hamiltonian, which includes the spin-orbit term.

where The probability of hopping (psh) is calculated from Landau-Zener theory giving where in which the spin-orbit coupling derived off the diagonal Hamiltonian matrix element between two electronic states (H12), the relative slope of the two surfaces at the crossing seam [F(Δ)], the reduced mass of the system through its movement along the hopping coordinate (μ), and the kinetic energy of the system passing through the crossing point (E) are used.

It is useful to note that when Eh < Ec (when below the minimum energy crossing point) the probability of hopping between spin states is null.

The difference in rates of C-H activation of methane for CoCp(CO), RhCp(CO), and IrCp(CO) readily demonstrate this property.

[8] Metal-oxo species, due to their small spatial extent of metal-centered d orbitals leading to weak bonding, often have similar energies for both the low spin (

[9] This similarity in energy between the low- and high spin configurations of oxo-species lends itself to the study of spin-forbidden reactions, such as Mn(salen)-catalyzed epoxidation.

Singlet and Triplet Cobalt Complexes. The ground state of Tp i -Pr,Me Co(CO) has two unpaired electrons . [ 2 ]
Potential energy surfaces for spin-forbidden reactions of both diabatic and adiabatic variety. The difference between the two adiabatic surfaces is 2H 12 , where H 12 = <Ψ 1 | H soc |Ψ 2 >.
Reactions of manganese-oxo complexes with alkenes. Depending on the spin state of the starting material, triplet or quintet in this case, route A, B, or C can be followed, yielding potentially different products. The reactions also proceed differently for different R substitutes, where one is always alkyl and the second one is alkyl in the case of route A , aryl , alkenyl , or alkynyl in the case of route B , or alkyl, aryl, alkenyl, or alkynyl for route C . For routes B and C , the alkyl R is internal for the radical case.