Reduction of 2-H-substituted pyrrolinium cations: the carbon-carbon single bond in air stable 2,2'-bipyrrolidines as a two-electron-source.

Reduction of 2-H-substituted pyrrolinium cations via initially formed secondary radicals results in either dimerisation or H-abstracted products, while the outcome depends on the N-substituents. The resultant central carbon-carbon single bond in the dimerised 2,2'-bipyrrolidine derivatives can be oxidised chemically and electrochemically. The notably air and moisture-stable dimers were subsequently utilised as a source of two electrons in various chemical transformations.

Contrasting reactivity of (boryl)(aryl)lithium-amide with electrophiles: N- vs. p-aryl-C-nucleophilic substitution.

Herein we report two different reactivity modes of lithium(aryl)(boryl)amide, 4, when it is reacted with chlorosilanes such as SiCl4 and MeSiHCl2, and chlorophosphine, Ph2PCl. Thus, the reaction of lithium(aryl)(boryl)amide, 4, with MeSiHCl2 leads exclusively to an N-substitution product, 6. On the other hand, the reaction of 4 with SiCl4 and Ph2PCl proceeds completely differently affording exclusively p-aryl-C-substitution products, 5 and 7, respectively.

Reactivity of silagermenylidene toward nitrous oxide: a preliminary DFT study.

The possible reaction mechanism of silagermenylidene and its NHC (N-heterocyclic carbene) coordinated form with N2O were investigated by DFT methods. Mainly, the potential energy surfaces of the five pathways I-IV were explored. Pathways I, II, III, and III' deal with the oxidation of silagermenylidene, whereas that of NHC coordinated form is associated with pathways I, III, III', and IV. Pathway I is initiated by the interaction between terminal N atom of N2O and Si atom of silagermenylidene in a stepwise manner. Pathway II details concerted direct oxidation of silagermenylidene. Pathways III and III' are related to the concerted 1,3-dipolar cycloaddition steps. Pathway IV is about the interaction of terminal atoms of N2O with carbenic Ge atom of silagermenylidene. All the proposed pathways I-IV portray the isomerization of silagermenylidenes to silagermoxiranylidenes. The subsequent N2O addition to the silagermoxiranylidenes was also investigated in the present study. Somehow with a trend similar to silagermenylidenes, the proposed pathways I-IV exist for the second molecule N2O activation by silagermoxiranylidenes. A comparison of the free energy profiles of the proposed pathways gave the important result that pathways III and III' remain the most facile mechanisms to activate N2O in all cases. We strongly believe that the proposed mechanisms will be effective to better understand the chemistry of heavier vinylidenes and provide further impetus to this field. Graphical Abstract The possible oxidation reaction mechanism of silagermenylidene with nitrous oxide was investigatedthrough density functional calculations. The concerted 1,3-dipolar cycloadditions are determined to beenergetically most facile pathways.

A mechanistic investigation on the formation and rearrangement of silaspiropentane: A theoretical study.

The formation of silaspiropentane from addition of singlet silacyclopropylidene 1 and silacyclopropylidenoid 8 to ethylene has been investigated separately at the B3LYP, X3LYP, WB97XD, and M05-2X theories using the 6-31+G(d,p) basis set. The silacycloproylidenoid addition follows a stepwise route. In contrast, a concerted mechanism occurs for silacyclopropylidene addition. Moreover, the intramolecular rearrangements of silaspiropentane 9 to methylenesilacyclobutane 11 and 2-silaallene + ethylene 12 have been studied extensively. The required energy barrier for the isomerization of 9 to 10 was determined to be 44.0 kcal mol(-1) at the B3LYP/6-31+G(d,p) level. After formation of 10, the rearrangement to methylenesilacyclobutane 12 is highly exergonic by -15.9 kcal mol(-1), which makes this reaction promising. However, the conversion of 9 to 11 is calculated to be quite endergonic, by 26.5 kcal mol(-1).