Effect of the ring size of TMC ligands in controlling C–H bond activation by metal-superoxo species

Abstract

Metal-superoxo species are very important in carrying many metal-mediated catalytic transformation reactions. Such catalytic reactivity is affected by many factors such as by nature of metal ions and ring size...

Theoretical study of the formation of metal–oxo species of the first transition series with the ligand 14-TMC: driving factors of the “Oxo Wall”

“…There are two possible spin states for chromium(IV)-oxo species, i.e., 3 Cr hs -Int and 1 Cr ls -Int, and our results show that the high-spin state ( 3 Cr hs -Int) is found as the ground state, which is in agreement with the previous studies. 73,78 The computed Cr-O bond length was found to be 1.715 Å, which is in agreement with the experimental observation. 95 Chromium-oxo species also play an important role during hydrogen and oxygen atom transfer reactions.…”

“…In our previous studies, we have performed DFT calculations with the two possible isomers based on the orientation of the methyl groups of the TMC ring (either syn or anti to the superoxo unit), and we found that the anti isomer is more stable than the syn isomer. 73 Thus, here, we performed the calculations on the 3d metal hydroperoxo species with a 14-TMC ligand having chlorine at the position trans to the hydroperoxo, i.e., the anti isomer, and studied the structure and energetics of the metal hydroperoxo species, O⋯O bond cleavage and formed metal-oxo species, followed by a comparative study. Here, we started the calculations with the chromium hydroperoxo species.…”

“…In our previous studies, method assessment using functionals such as B3LYP, 75,76 B3LYP-D2, 77 wB97XD, 78 B97D, 77,79 M06-2X, 80 TPPSh, 81 and MP2 82 has been performed, and it was found that the B3LYP-D2 functional is superior for predicting the correct spin state. 5,37,66,73 Thus, here, we have restricted our calculations to the B3LYP-D2 functional. The basis set LanL2DZ was used for the metals (Cr, Mn, Fe, Co, Ni, and Cu) [83][84][85][86] and 6-31G 87 was used for carbon, hydrogen, nitrogen, oxygen, and chlorine.…”

“…DFT calculations were performed on all possible spin states ( 4 Mn hs -Int and 2 Mn ls -Int) of the formed manganese(IV)-oxo species, and it is found that the 4 Mn hs -Int spin state is the ground state, which is in agreement with the earlier study. 27,73 Manganese-oxo species are also involved in C-H/O-H activation and oxygen atom transfer reactions. [27][28][29] Iron(III) hydroperoxo species Similar to those of the chromium(III) and manganese(III) hydroperoxo species, all the possible spin states of the iron hydroperoxo species i.e.…”

“…We selected this ligand for our study because several metal complexes have been reported with TMC ligands. [71][72][73] O⋯O bond cleavage in metal hydroperoxo species leads to the formation of metal-oxo species. 66 In this work, the formation of 3d metal-oxo (Cr-Cu) species and a comparative study among them have been carried out, and we have tried to figure out what are the driving factors for the formation of the "Oxo Wall".…”