Ab initio Study of Mechanism of Cycloaddition Reaction between Germylene Silylene (H2GeSi:) and Acetone

The mechanism of the cycloaddition reaction between singlet H2Si=Si: and formaldehyde has been investigated with the CCSD(T)//MP2/6-31G* method. From the potential energy profile, it could be predicted that the reaction has three competitive dominant reaction pathways. The reaction rules presented is that the 3p unoccupied orbital of the Si: atom in H2Si=Si: inserts the π orbital of formaldehyde from the oxygen side, resulting in the formation of an intermediate. Isomerization of the intermediate further generates a four-membered ring silylene (the H2Si–O in the opposite position). In addition, the [2+2] cycloaddition reaction of the two π-bonds in H2Si=Si: and formaldehyde also generates another four-membered ring silylene (the H2Si–O in the syn-position). Because of the unsaturated property of the Si: atom in the two four-membered ring silylenes, the two four-membered ring silylenes could further react with formaldehyde, generating two silicic bis-heterocyclic compounds. Simultaneously, the ring strain of the four-membered ring silylene (the H2Si–O in the syn-position) makes it isomerize to a twisted four-membered ring product.

The mechanism of the cycloadditional reaction between singlet dichloro-germylidene(R1) and (acetaldehyde(R2) has been investigated with MP2/6-31G* method, including geometry optimization, vibrational analysis and energies for the involved stationary points on the potential energy surface. From the potential energy profile, we predict that the cycloaddition reaction between singlet dichloro-germylidene and acetaldehyde has two competitive dominant reaction pathways. Going with the formation of two side products (INT3 and INT4), simultaneously. The two competitive reactions both consist of two steps: (1) two reactants firstly form a three-membered ring intermediate (INT1) and a twisted four-membered ring intermediate (INT2), respectively, both of which are barrier-free exothermic reactions of 44.5 and 63.0 kJ/mol; (2) then INT1 and INT2 further isomerize to a four-membered ring product (P1) and a chlorine-transfer product (P2) via transitions (TS1 and TS2), respectively, with the barriers of 9.3 and 1.0 kJ/mol; simultaneously, P1 and INT2 react further with acetaldehyde(R2) to give two side products (INT3 and INT4), respectively, which are also barrier-free exothermic reaction of 65.4 and 102.7 kJ/mol.

X2Sn=Sn: (X = H, Me, F, Cl, Br, Ph, Ar, …) are new species of chemistry. The cycloaddition reaction of X2Sn=Sn: are new study field of stannylene chemistry. To explore the rules of cycloaddition reaction between X2Sn=Sn: and the symmetric π-bonded compounds, the cycloaddition reactions of H2Sn=Sn: and ethylene were selected as model reactions in this paper. The mechanism of cycloaddition reaction between singlet H2Sn=Sn: and ethylene has been first investigated with the MP2/GENECP (C, H 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 two reactants firstly form a four-membered Sn-heterocyclic ring stannylene through the [2 + 2] cycloaddition reaction. Because of the 5p unoccupied orbital of Sn: atom in the four-membered Sn-heterocyclic ring stannylene and the π orbital of ethylene forming a π → p donor-acceptor bond, the four-membered Sn-heterocyclic ring stannylene further combines with ethylene to form an intermediate. Because the Sn: atom in intermediate happens sp3 hybridization after transition state, then, intermediate isomerizes to a spiro-Sn-heterocyclic ring compound. The research result indicates the laws of cycloaddition reaction between X2Sn=Sn: and the symmetric π-bonded compounds. The study opens up a new research field for stannylene chemistry.

The mechanism of the cycloaddition reaction between singlet silylene silylene (H2SiSi:) and acetone has been investigated with the CCSD (T)//MP2/6‐31G∗︁ method. According to the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction channels. The present rule of this reaction is that the [2+2] cycloaddition reaction of the two π‐bonds in silylene silylene (H2SiSi:) and acetone leads to the formation of a four‐membered ring silylene (E3). Because of the unsaturated property of Si: atom in E3, it further reacts with acetone to form a silicic bis‐heterocyclic compound (P7). Simultaneously, the ring strain of the four‐membered ring silylene (E3) makes it isomerize to a twisted four‐membered ring product (P4).

The mechanism of the cycloaddition reaction between singlet silylene silylene (H₂Si=Si:) and acetaldehyde has been investigated with CCSD(T)//MP2/6-31G* and CCSD(T)//MP2/6-31G** method, from the potential energy profile, we could predict that the reaction has three competitive dominant reaction pathways. The present rule of this reaction is that the 3p unoccupied orbital of the Si: atom in silylene silylene (H₂Si=Si:) inserts on the π orbital of acetaldehyde from oxygen side, resulting in the formation of an intermediate. Isomerization of the intermediate further leads to the generation of a four-membered ring silylene (the H₂Si-O in the opposite position). In addition, the [2 + 2] cycloaddition reaction of the two π-bonds in silylene silylene and acetaldehyde generates another four-membered ring silylene (the H₂Si-O in the syn-position). Because of the unsaturated property of Si: atom in the two four-membered ring silylenes, they could further react with acetaldehyde, resulting in the generation of two spiro-heterocyclic ring compounds with Si. Simultaneously, the ring strain of the four-membered ring silylene (the H₂Si-O in the syn-position) makes it isomerize to a twisted four-membered ring product.

The mechanism of the cycloaddition reaction between singlet H2Ge = Ge: and acetone has been investigated with CCSD(T)//MP2/6-31G* 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. Because of the 4p-unoccupied orbital of Ge atom in the four-membered Ge-heterocyclic ring germylene and the π-orbital of acetone forming a π → p donor–acceptor bond, the four-membered Ge-heterocyclic ring germylene further combines with acetone to form an intermediate. Because the Ge atom in intermediate happens sp3 hybridization after transition state, then, 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.

The mechanism of the cycloaddition reaction between singlet dimethyl-silylene carbene and formaldehyde has been investigated with MP2/6-31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by zero-point energy and 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 main products of first dominant reaction pathway are a planar four-membered ring product (P4) and its H-transfer product (P4.2). The main product of second dominant reaction pathway is a silicic bis-heterocyclic compound (P5). © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

The mechanism of cycloaddition reaction between singlet alkylidene carbene and ethylene has been investigated with second‐order Moller‐Plesset perturbation theory (MP2). By using 6–31G* basis, geometry optimization, vibrational analysis and energetics have been calculated for the involved stationary points on the potential energy surface. The results show that the title reaction has two major competition channels. An energy‐rich intermediate (INT) is firstly formed between alkylidene carbene and ethylene through a barrier‐free exothermic reaction of 63.62 kJ/mol, and the intermediate then isomerizes to a three‐membered ring product (Pl) and a four‐membered ring product (P2) via transition state TS1 and TS2, in which energy barriers are 47.00 and 51.02 kl/mol. respectively. PI is the main product.

The mechanism of the cycloaddition reaction between singlet 2,2-dimethyl(2-germavinylidene) [(CH3)2Ge=C:] and formaldehyde has been investigated with CCSD(T)//MP2/6-311G** method. From the potential energy profile, it could be predicted that the reaction has two competitive dominant reaction pathways. The first pathway consist of the transfer of formaldehyde oxygen π-electrons to the 2p unoccupied orbital of the C: atom in 2,2-dimethyl(2-germavinylidene) with a formation of intermediate which then isomerizes to a four-membered heterocyclic ring carbene (Ge and O in the 1,3-position). The second pathway is a direct [2 + 2] cycloaddition reaction in which the interaction of two π-bonds in 2,2-dimethyl(2-germavinylidene) and formaldehyde generates another four-membered heterocyclic ring carbene (Ge and O in 1,2-position). Because of the unsaturated property of the C: atom in the two four-membered heterocyclic ring carbenes, the two four-membered heterocyclic ring carbenes could further react with formaldehyde, generating two spiro-heterocyclic ring compounds.

X2C=Sn: compounds (X=H, Me, F, Cl, Br, Ph, Ar) are new species. The cycloaddition reactions of X2C=Sn: are also a new study field of unsaturated stannylene chemistry. The mechanism of cycloaddition reaction between singlet Me2C=Sn: and ethene was investigated for the first time using the MP2/GENECP (C, H in 6-311++G**; Sn in LanL2dz) method. From the potential energy profile, it was predicted that the reaction has one dominant channel in which the 5p unoccupied orbital of Sn: in Me2C=Sn: and the π orbital of ethene form a π→p donor-acceptor bond in an intermediate product. Instability of the intermediate product results in its isomerization to a four-membered ring of stannylene. The four-membered stannylene further combines with ethene to form another intermediate product that further isomerizes to a spiro-Sn-heterocyclic ring compound.

Theoretical study on the mechanism of cycloaddition reaction between silylene carbene and formaldehyde

The mechanism of the cycloaddition reaction between singlet dimethyl-silylene carbene and acetone has been investigated with density functional theory, From the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction pathways. The presented rule of this reaction: the [2+2] cycloaddition effect between the π orbital of dimethyl-silylene carbene and the π orbital of π-bonded compounds leads to the formation of a twisty four-membered ring intermediate and a planar four-membered ring product; The unsaturated property of C atom from carbene in the planar four-membered ring product, resulting in the generation of CH3-transfer product and silicic bis-heterocyclic compound.

Theoretical study on the mechanism of cycloaddition reaction between dimethyl germylidene and formaldehyde

The mechanism of the cycloaddition reaction between singlet dichloro‐germylene carbene and aldehyde has been investigated with MP2/6‐31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by zero‐point energy and 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 channel (A) consists of four steps: (1) the two reactants (R1, R2) first form an intermediate INT2 through a barrier‐free exothermic reaction of 142.4 kJ/mol; (2) INT2 then isomerizes to a four‐membered ring compound P2 via a transition state TS2 with energy barrier of 8.4 kJ/mol; (3) P2 further reacts with aldehyde (R2) to form an intermediate INT3, which is also a barrier‐free exothermic reaction of 9.2 kJ/mol; (4) INT3 isomerizes to a germanic bis‐heterocyclic product P3 via a transition state TS3 with energy barrier of 4.5 kJ/mol. The process of channel (B) is as follows: (1) the two reactants (R1, R2) first form an intermediate INT4 through a barrier‐free exothermic reaction of 251.5 kJ/mol; (2) INT4 further reacts with aldehyde (R2) to form an intermediate INT5, which is also a barrier‐free exothermic reaction of 173.5 kJ/mol; (3) INT5 then isomerizes to a germanic bis‐heterocyclic product P5 via a transition state TS5 with an energy barrier of 69.4 kJ/mol. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

The mechanism of the cycloaddition reaction between singlet dichlorosilylene carbene (Cl2Si=C:) and formaldehyde has been investigated with MP2/6-31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by Zero-point energy and 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 first dominant reaction pathway consists of two steps: (1) the two reactants (R1, R2) firstly form a four-membered ring intermediate (INT4) through a barrier-free exothermic reaction of 387.9 kJ/mol; (2) intermediate (INT4) then isomerizes to H-transfer product (P4.2) via a transition state (TS4.2) with energy barrier of 4.7 kJ/mol. The second dominant reaction pathway as follows: on the basis of intermediate (INT4) created between R1 and R2, intermediate (INT4) further reacts with formaldehyde (R2) to form the intermediate (INT5) through a barrier-free exothermic reaction of 158.3 kJ/mol. Then, intermediate (INT5) isomerizes to a silicic bis-heterocyclic product (P5) via a transition state (TS5), for which the barrier is 40.1 kJ/mol.