1,2-Addition Reaction of Monosubstituted Disilenes:  An Ab Initio Study

Abstract

Mechanisms of 1,2-addition reactions of the monosubstituted disilenes H 2 SidSiHMe, H 2 SidSiHF, H 2 SidSiH(CtCH), and H 2 SidSiH(NH 2 ) were investigated in detail by the ab initio MO method. All reactions start from the electrophilic and nucleophilic initial complexes C E and C N . Four initial complexes and, therefore, four reaction channels were found for the reactions of methyldisilene with water and of ethynyldisilene with water. Only two complexes were found, however, in the reactions of fluorodisilene and aminodisilene with water/hydrogen fluoride. The reaction of the polar substrate aminodisilene shows reaction profiles similar to that of the polar substrate silene. In addition, product switching of the stereochemistry, depending on the acidity of the reagent, was found for the reaction of aminodisilene.

The Addition of a Cyclopropyl Alkyne to an Asymmetrically-Substituted Disilene: A Mechanistic Study

“…To proceed through a zwitterionic intermediate, we propose that a non-aryl substituent, such as a fluoro or an amino substituent, would have to be utilized to sufficiently polarize the SiSi bond and change the nature of the intermediate. 18 ■ EXPERIMENTAL SECTION General Methods and Instrumentation. All reactions were conducted under a nitrogen atmosphere using an MBraun Labmaster 130 glovebox.…”

“…Evidently, the difference between a phenyl substituent and a Tip substituent is not sufficient to polarize the disilene bond to alter the mechanism of alkyne addition. To proceed through a zwitterionic intermediate, we propose that a non-aryl substituent, such as a fluoro or an amino substituent, would have to be utilized to sufficiently polarize the SiSi bond and change the nature of the intermediate …”

Theoretical study on the addition reactions of MeOH, PhOH and PhSH to silastannenes

“…The second complex and the final product (P) were then reached via two transition states (TS). The whole mechanism is very similar to that for addition reactions of water or methanol toward disilene [6,10]. Considering the similarity between reactions 1 and 4, only the molecular structures of complexes, transition states and products for reaction 4a and 4b are shown in Fig.…”

“…The theoretical studies show that the addition reactions of ROH monomer to silenes [5][6][7] or disilenes [6,[8][9][10] start generally by the formation of an intermolecular complex which is converted to the final product through a four-membered transition state. In subsequent studies [11][12][13] it was found that the reaction of silenes or disilenes with the ROH dimer is much more favorable than with the monomer.…”

Temperature-Dependent Low-Frequency Vibrations of Thiamine Crystal Containing Hydrated Ions

“…The crystalline monohydrate of 1 is considered a snapshot of the moment when water attacks the chloride ion in the initial stage of dissolution. Previously, we have found from gas-phase calculations that a water addition reaction starts with the formation of an initial complex via intermolecular hydrogen bonding. − Thiamine (vitamin B1), studied herein, is a water-soluble vitamin and is commercially available in the form of thiamine chloride hydrochloride, 1 , which increases its solubility. Most vitamins have regions that mimic DNA or amino acids, and thiamine is a very important vitamin for human beings.…”