D substitution mechanism

The pressure dependence for the substitution of pyridine and substituted pyridine is reported in Figure 23, from which it follows that the larger effects observed for the 4-acetyl- and 4-cyanopyridine complexes are consistent with the volume difference expected between the LF and MLCT excited states. The positive volumes of activation support the operation of a dissociative D substitution mechanism as a result of LF excitation [101], The photosubstitution reactions of complexes of the type M(CO)4phen (M = Cr, Mo, W) have received attention from various groups, mainly because of possible roles played by both LF and MLCT excited states in such processes (Fig. 24). For the overall reaction given in Eq. (30),... 

While experimental data that exhibit these relationships support both the validity of the steady-state approximation and a D substitution mechanism, the exceedingly low [ML5] concentration that forms on the basis of this approximation renders the detection of this intermediate impossible in many cases. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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