Alkylation versus trans-silylation of N-methyl-N-trimethylsilylacetamide with ambident electrophiles (chloromethyl)fluorosilanes

Tetrel Bonding along the Pathways of Transsilylation and Alkylation ofN-Trimethylsilyl-N-methylacetamide with Bifunctional (Chloromethyl)fluorosilanes

“…The energy profiles of the transsilylation and alkylation reactions of tautomers 1a and 1b with silanes 2 , 5 , and 6 , including the transition states between the reagents, intermediates, and final products, were calculated (Schemes and ). According to calculations, the reactions are exothermic; complexes 7a , 10a , and 11a precede the first transition states TS1 having activation energies of 17.4, 19.8, and 21.7 kcal/mol, respectively, at the M06-2X/6-311G­(d,p) level. The relationship between the complexes of amide 1a with silanes 2 – 5 and the corresponding transition states of the transsilylation TS1 and alkylation TS1 ′ reactions must cause similar changes in energetic, geometric, and topological parameters as the charge is transferred along the reaction coordinate, as is the case when the tetrel-bonded complexes participate in S N 2 reactions at silicon. , Since the orientation of amide 1a and silanes in complexes 7a – 10a is the same, the analyzed parameters are given in Figure by taking the example of the reaction of 1a with (chloromethyl)­trifluorosilane 2 .…”

“…The effect of solvent polarity and specific solvation on the formation of the tetrel bond was studied by calculating complex 7a′ and solvate 1:1 complexes of 7a′ with chloroform, in which the solvent molecule forms a hydrogen bond with the axial fluorine (Si–F ax ) or chlorine atom (C–Cl ax ), as well as 1:2 complexes in which two molecules of the solvent are bound to both halogens, in chloroform solution (Figure S4). The choice of the solvent was determined by the fact that it was used for carrying out IR monitoring of the reaction . QTAIM analysis showed the presence of BCPs on the O···Si bonds of the complex, which in all cases are tetrel bonds, whereas no BCPs were found between the CH 2 Cl carbon and the carbonyl oxygen atoms (Figure S5).…”

“…The choice of the solvent was determined by the fact that it was used for carrying out IR monitoring of the reaction. 18 QTAIM analysis showed the presence of BCPs on the O•••Si bonds of the complex, which in all cases are tetrel bonds, whereas no BCPs were found between the CH 2 Cl carbon and the carbonyl oxygen atoms (Figure S5). Topological characteristics of the O•••Si bonds and the values of their energies prove that these bonds are substantially stronger than those in 7a′ in the gas phase (Tables 4 and 5).…”

“…Their close values of V max of 53.72 and 53.54 kcal/mol indicate the possibility of formation of tetrel bonds with participation of both the silicon atom and the carbon atom of the chloromethyl group with the oxygen atom of amide 1a or the nitrogen atom of imidate 1b . This allows us to explain the interplay of dual reactivity and the formation of both the transsilylation and alkylation products in the reaction of silane 2 with tautomers 1a and 1b . Two types of complexes are initially formed in the reaction of amide 1a and silane 2 .…”

“…Recently, there is growing interest on studying the S N 2 type prereaction complexes by spectral and quantum chemical methods. − However, the question of the structure of intermolecular complexes formed in the first stage of the reaction of N -trimethylsilyl- N -methylacetamide with (chloromethyl)­fluorosilanes ClCH 2 SiMe n F 3– n ( n = 0–2) is still unanswered …”