Activation of C-H bonds in C-1-C-3 alkanes by titanium(IV) and zirconium(IV) cationic complexes: a DFT study

A DFT study of a model reaction [(eta (5)-C5H5)(2)MCH3](+) + RH reversible arrow [(eta (5)-C5H5)(2)MR](+) + CH4 (M = Ti-IV, Zr-IV; R = Me, Et, Pr, Pr- i) was carried out with the PBE density functional, Exchange of cr-bonded l igand proceeds through the formation of agostic complexes [Cp2M(RH)CH3](+) followed by their isomerization into complexes [CP2M(CH4)R](+) via an inner -sphere migration of a hydrogen atom. The calculated rate constants for suc h migrations involving the primary and secondary C-H bonds of propane molec ule differ by 930 times for Ti-IV complexes and by 47 times for Zr-IV compl exes, which is due to the effect of steric factors.