The X2Ge=Si： （X = H, Me, F, reaction is a new area for the study of silylene between singlet CI2Ge=Si： and formaldehyde CI, Br, Ph, At...） is a new species. Its cycloaddition chemistry. The mechanism of cycloaddition reaction has been investigated with CCSD（T）//MP2/6-31G＊ method. From the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction pathways. The reaction rule presented is that the two reactants firstly form a four-membered Ge-heterocyclic ring silylene through the [2＋2] cycloaddition reaction. Owing to the 3p unoccupied orbital of Si： atom in the four-membered Ge-heterocyclic ring silylene and the π orbital of formaldehyde forming a π-p donor-acceptor bond, the four-membered Ge-heterocyclic ring silylene further combines with formaldehyde to form an intermediate. Because the Si： atom in intermediate shows sp3 hybridization after transition state, the intermediate isomerizes to a spiro-Si-heterocyclic ring compound involving Ge via a transition state. Simultaneously, the ring strain of the four-membered Ge-heterocyclic ring silylene makes it isomerize to a twisted four-membered ring product. The research result indicates the laws of cycloaddition reaction between X2Ge=Si： （X = H, Me, F, C1, Br, Ph, Ar...） and the asymmetric g-bonded compounds, which are significant for the synthesis of small-ring and spiro-Si-heterocyclic ring compound involving Ge The study extends the research area and enriches the research content of silvlene chemistrv.
The synthesis of 1,3,5-substituted-1,2,4-triazoles from α-imino-3-pyridine formic acid,acetamidine and anisole hydrazine as a model reaction in this paper and the synthesis mechanism of 1,3,5-substituted-1,2,4-triazole compounds from carboxylic acids,amidines and hydrazines have been first investigated with the B3 LYP/6-311＋＋G＊＊ method.According to the potential energy profile,it can be predicted that the course of the reaction consists of five reactions containing six elementary reactions.The α-imino-3-pyridine formic acid and acetamidine form first an intermediate product through a dehydration reaction; the intermediate product further combines with hydrogen ion to form a positive ion; the positive ion reacts with anisole hydrazine by a dehydration reaction to form another positive ion; then,followed by two isomerization reactions,the final reaction with the acetate ion（Ac-） produces the final product.The research results reveal the laws of synthesis reaction of 1,3,5-substituted-1,2,4-triazoles by the carboxylic acids,amidines,hydrazines and their derivatives on theoretical level.It provides the systemic theoretical basis for the synthesis,development and application of 1,3,5-substituted-1,2,4-triazole compounds.
X2Si=Sn:(X = H, Me, F, Cl, Br, Ph, Ar…) are new species of chemistry. The cycloaddition reaction of X2Si=Sn: is a new study field of stannylene chemistry. To explore the rules of cycloaddition reaction between X2Si=Sn: and the symmetric p-bonded compounds, the cycloaddition reactions of Cl2Si=Sn: and ethylene were selected as model reactions in this paper.The mechanism of cycloaddition reaction between singlet Cl2Si=Sn: and ethylene has been first investigated with the MP2/GENECP(C, H, Cl, Si in 6-311++G**;Sn in LanL2dz) method in this paper. From the potential energy profile, it could be predicted that the reaction has one dominant reaction channel. The reaction rule presented is that the 5p unoccupied orbital of Sn in Cl2Si=Sn: and the π orbital of ethylene forming a p→p donor-acceptor bond, resulting in the formation of an intermediate. Instability of the intermediate makes it isomerize to a four-membered Si-heterocyclic ring stannylene. Because the 5p unoccupied orbital of Sn atom in the four-membered Si-heterocyclic ring stannylene and the π orbital of ethylene form a p→p donor-acceptor bond, the four-membered Si-heterocyclic ring stannylene further combines with ethene to form another intermediate. Because the Sn atom in the intermediate shows sp3 hybridization after transition state, the intermediate isomerizes to a Si-heterocyclic spiro-Sn-heterocyclic ring compound. The research result indicates the laws of cycloaddition reaction between X2Si=Sn: and the symmetric π-bonded compounds. The study opens up a new research field for stannylene chemistry.
X2Si=Ge： （X = H, Me, F, CI, Br, Ph, Ar...） is a new species. Its cycloaddition reaction is a new area for the study of germylene chemistry. The mechanism of cycloaddition reaction between singlet state Me2Si=Ge： and formaldehyde has been investigated with the CCSD（T）//MP2/cc-pvtz method. From the potential energy profile, it could be predicted that the reaction has one dominant reaction pathway. The reaction rule presented is that the two reactants first form a four-membered Si-heterocyclic ring germylene through the [2＋2] cycloaddition reaction. Because of the 4p unoccupied orbital of Ge： atom in the four-membered Si-heterocyclic ring germylene and the π orbital of formaldehyde form a π→p donor-acceptor bond, the four-membered Si-heterocyclic ring germylene further combines with formaldehyde to form an intermediate. Because the Ge atom in the intermediate undergoes sp^3 hybridization after transition state, then the intermediate isomerizes to a spiro-Ge-heterocyclic ring compound involving Si via a transition state. The research result indicates the laws of cycloaddition reaction between HzSi=Ge： and formaldehyde. It has important reference value for the cycloaddition reaction between X2Si=Ge： （X = H, Me, F, CI, Br, Ph, Ar…） and asymmetric to-bonded compounds, which is significant for the synthesis of small-ring and spiro-Ge-heterocyclic compounds involving Si. The study extends research area and enriches the research content of germylene chemistry.
The mechanism of cycloaddition reaction between singlet state H2Ge=Ge： and acetaldehyde has been investigated with the MP2/6-311＋＋G＊＊ method. From the potential energy profile, it could be predicted that the reaction has two competitive dominant reaction pathways. The reaction rule presented is that the two reactants firstly form a four-membered Ge-heterocyclic ring germylene through the [2＋2] cycloaddition reaction. As the 4p unoccupied orbital of Ge： atom in the four-membered Ge-heterocyclic ring germylene and the π orbital of acetaldehyde form a π→p donor-acceptor bond, the four-membered Ge-heterocyclic ring germylene further combines with acetaldehyde to give an intermediate. Because the Ge atom in intermediate exhibits sp3 hybridization after transition state, the intermediate isomerizes to a spiro-Ge-heterocyclic ring compound via a transition state. Simultaneously, the ring strain of the four-membered Ge-heterocyclic ring germylene makes it isomerize to a twisted four-membered ring product.
