Ab initio study of mechanism of forming bis-heterocyclic compound with Si and Ge between dimethylsilylene germylidene (Me2Si=Ge:) and ethene

The mechanism of the cycloaddition reaction between singlet dimethylsilylene germylidene (Me₂Si=Ge:) and ethene has been investigated with the CCSD(T)//MP2/6-31G* method. From the potential energy profile, it could be predicted that the reaction has one dominant reaction pathway. The reaction rules presented is that the two reactants firstly form a Si-heterocyclic four-membered ring germylene through the [2+2] cycloaddition reaction. Due to the sp ³ hybridization of the Ge: atom in Si-heterocyclic four-membered ring germylene, the Si-heterocyclic four-membered ring germylene further combined with ethene to form a bis-heterocyclic product with Si and Ge (P2).     

Ab initio study of mechanism of forming bis-heterocyclic compound with Si and Ge between silylene germylene (H2Si=Ge:) and formaldehyde

The mechanism of the cycloaddition reaction between singlet state silylene germylene (H₂Si=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 rules presented is that [2?+?2] cycloaddition reaction between two reactants firstly generates a Si-heterocyclic four-membered ring germylene. Because of the 4p unoccupied orbital of the Ge atom in (the) Si-heterocyclic four-membered ring germylene and the ?? orbital of formaldehyde forming a ??????p donor?Cacceptor bond, the Si-heterocyclic four-membered ring germylene further combines with formaldehyde to form an intermediate. Because the Ge atom in intermediate happens sp ³ hybridization after transition state, then, intermediate isomerizes to a bis-heterocyclic compound with Si and Ge via a transition state.     

Density functional theory study of mechanism of forming a spiro-Ge-heterocyclic ring compound from H2Ge=Ge: and ethene

The mechanism of the cycloaddition reaction between singlet H₂Ge=Ge: and ethene has been investigated by the B3LYP/6-311 ++G** method. From the potential energy profile and change of Gibbs free energy, it could be predict that the reaction has only one dominant reaction pathway at 298 K and 149.825 kPa. The reaction rule presented is that the two reactants first 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 ethene forming a π → p donor–acceptor bond, the four-membered Ge-heterocyclic ring germylene further combines with ethene to form an intermediate; and because the Ge: atom in intermediate happens sp³ hybridization after transition state, then the intermediate isomerizes to a spiro-Ge-heterocyclic ring compound via a transition state.     

Ab initio Study on Formation Mechanism of Spiro-Si-Heterocyclic Ring Compound Involving Ge from H2Ge=Si: and Formaldehyde

H₂Ge=Si: and its derivatives (X₂Ge=Si:, X=H, Me, F, Cl, Br, Ph, Ar,…) are new species. Its cycloaddition reactions are new area for the study of silylene chemistry. The cycloaddition reaction mechanism of singlet H₂Ge=Si: and formaldehyde has been investigated with the MP2/aug-cc-pVDZ method. From the potential energy profile, it could be predicted that the reaction has one dominant reaction pathway. The reaction rule is that two reactants firstly form a four-membered Ge-heterocyclic ring silylene through the [2+2] cycloaddition reaction. Because of 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 the intermediate undergoes sp³ hybridization after transition state, then the intermediate isomerizes to a spiro-Si-heterocyclic ring compound involving Ge via a transition state. The result indicates the laws of cycloaddition reaction between H₂Ge=Si: or its derivatives (X₂Ge=Si:, X=H, Me, F, Cl, Br, Ph, Ar,…) and asymmetric π-bonded compounds are significant for the synthesis of small-ring involving Si and Ge and spiro-Si-heterocyclic ring compounds involving Ge.     

Density Functional Theory Study on Mechanism of Forming Spiro-Ge-heterocyclic Ring Compound from Me2Ge=Ge: and Acetaldehyde

The H₂Ge=Ge:, as well as and its derivatives (X₂Ge=Ge:, X=H, Me, F, Cl, Br, Ph, Ar, : : :) is a kind of new species. Its cycloaddition reactions is a new area for the study of germy-lene chemistry. The mechanism of the cycloaddition reaction between singlet Me₂Ge=Ge: and acetaldehyde was investigated with the B3LYP/6-31G* method in this work. From the potential energy profile, it could be predicted that the reaction has one dominant re-action pathway. The reaction rule 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 acetaldehyde forming a π→p donor-acceptor bond, the four-membered Ge-heterocyclic ring germylene further combines with acetaldehyde to form an intermedi-ate. 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. The research result indicates the laws of cycloaddition reaction between Me₂Ge=Ge: and ac-etaldehyde, and lays the theory foundation of the cycloaddition reaction between H₂Ge=Ge: and its derivatives (X₂Ge=Ge:, X=H, Me, F, Cl, Br, Ph, Ar, : : :) and asymmetric π-bonded compounds, which are significant for the synthesis of small-ring and spiro-Ge-heterocyclic ring compounds.     

Ab initio study of the mechanism of forming a spiro‐heterocyclic ring compound involving Si and Ge from dichlorosilylene germylidene(Cl2SiGe:) and formaldehyde

The mechanism of the cycloaddition reaction between singlet dichlorosilylene germylidene (Cl₂Si?Ge:) 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 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 forming 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 intermediate undergoes sp3 hybridization after transition state, then, the intermediate isomerizes to a spiro‐heterocyclic ring compound involving Si and Ge via a transition state. © 2012 Wiley Periodicals, Inc.     

Ab initio study of mechanism of forming a spiro-ge-heterocyclic ring compound

The mechanism of cycloaddition reaction between singlet state dichloromethylenegermene (Cl₂C=Ge:) and ethene has been investigated with the CCSD(T)//B3LYP/6-31G* method. From the potential energy profile, it could be predicted that the reaction has one dominant reaction channel. The reaction rule presented is that the 4p unoccupied orbital of Ge in dichloromethylenegermene and the π orbital of ethene forming a π → p donor–acceptor bond resulting in the formation of a three-membered ring intermediate. Ring-enlargement effect make the three-membered ring intermediate isomerizes to a four-membered ring germylidene. Because the 4p unoccupied orbital of Ge atom in the four-membered ring germylidene and the π orbital of ethene form a π → p donor–acceptor bond, the four-membered ring germylidene further combines with ethene to form another intermediate. Because the Ge atom in the intermediate happens sp ³ hybridization after transition state, the intermediate isomerizes to a spiro-Ge-heterocyclic ring compound.     

Ab initio study of mechanism of cycloaddition reaction between H2Ge = Ge: and acetone

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.     

Ab initio study of mechanism of forming a Spiro-Si-heterocyclic ring compound

The mechanism of the cycloaddition reaction of forming a spiro-Si-heterocyclic ring compound between singlet dichloroalkylidenesilylene (Cl₂C=Si:) and ethene has been investigated with CCSD(T)//MP2/6-31G* method. From the potential energy profile, it can be predicted that the reaction has one dominant reaction pathway. The presented rule of this reaction is that the 3p unoccupied orbital of Si in dichloroalkylidene and the π orbital of ethene forming the π → p donor-acceptor bond, resulting in the formation of a three-membered ring intermediate. Ring-enlargement effect make the three-membered ring intermediate isomerizes to a four-membered ring silylene. Due to sp ³ hybridization of Si atom in the four-membered ring silylene, the four-membered ring silylene further combines with ethene to form a spiro-Si-heterocyclic ring compound.     

Theoretical study on the mechanism of cycloaddition reaction between dichlorogermylene silylene (Cl<Subscript>2</Subscript>Ge=Si:) and acetaldehyde

The mechanism of the cycloaddition reaction between singlet state dichlorogermylene silylene (Cl₂Ge=Si:) and acetaldehyde has been investigated with the MP2/cc-pvtz//MP2/6-31G* method. According to the potential energy profile, it can be predicted that the reaction has four competitive dominant reaction pathways. The presented rule of this reaction is that the 3p unoccupied orbital of Si: atom in dimethylgermylene silylene(Cl₂Ge=Si:) inserts the π orbital of acetaldehyde from the oxygen side, resulting in the formation of intermediate. In the intermediate and two reactants, two four-membered ring silylenes, with Si and O in the syn-position and opposite orientation, respectively, are generated, as the [2+2] cycloaddition reaction has occurred between the two bonding π orbital in dichlorogermylene silylene and acetaldehyde. Because of the unsaturated property of Si: atom in the two four-membered ring silylenes, they can further react with acetaldehyde to form two silicic bis-heterocyclic compounds. Simultaneity, the drive of ringlet tensility and unsaturated property of Si: atom in the four-membered ring silylene makes it isomerize into a distorted four-membered ring product and a Cl-transfer product and a H-transfer product, respectively.     

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

The mechanism of the cycloaddition reaction between singlet germylene silylene (H₂GeSi:) and acetone has been investigated with CCSD(T)/6‐31G*//MP2/6‐31G* method. From the potential energy profile, we could predict 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 (‐bonds in germylene silylene and acetone generates a four‐membered ring silylene with Ge. Because of the unsaturated property of Si atom in the four‐membered ring silylene with Ge, it could further react with acetone, resulting in the generation of a bis‐heterocyclic compound with Si and Ge. Simultaneously, the ring strain of the four‐membered ring silylene with Ge makes it isomerize to a twisted four‐membered ring product.     

Ab initio study of mechanism of forming a silicic <Emphasis Type="Italic">bis</Emphasis>-heterocyclic compound between (CH<Subscript>3</Subscript>)<Subscript>2</Subscript>Si=Si: and ethane

The mechanism of the cycloaddition reaction of forming a silicic bis-heterocyclic compound between singlet state (CH₃)₂Si=Si: and ethene has been investigated with the CCSD(T)//MP2/6-31G* method. From the potential energy profile, it can be predicted that the reaction has one dominant reaction pathway. The presented rule of this dominant reaction pathway that the 3p unoccupied orbital of Si: in (CH₃)₂Si=Si: and the π orbital of ethane forming a π → p donor-acceptor bond, resulting in the formation of a three-membered ring intermediate (INT1); Then, INT1 isomerizes to a four-membered ring silylene (P1), which driven by ring-enlargement effect; Due to sp ³ hybridization of Si: atom in the four-membered ring silylene (P1), P1 further combines with ethene to form a silicic bis-heterocyclic compound (P2).     

Density functional theory study of a mechanism of formation of a spiro heterocycle with the Ge spiroatom from dimethylgermylidene germylene (Me2Ge=Ge:) and ethylene

The B3LYP/6-311++G** study of the mechanism of the cycloaddition of singlet 2,2-dimethyl-1,2-digermavinylidene (Me₂Ge=Ge:) to ethylene was performed. [2+2] Cycloaddition of the reactants first produced four-membered cyclic germylene, then the interaction of unoccupied 4p orbital of the Ge atom with the π orbital of another ethylene molecule yielded intermediate with the π → p donor-acceptor bond. Isomerization of this intermediate via low-laying transition state resulted in spirocyclic compound with the sp³ hybridized Ge spiroatom.     

Ab initio study of mechanism of forming a spiro-heterocyclic ring compound involving Si from dichlorosilylenesilylene (Cl2Si=Si:)→Cl2Si=Si: and aldehyde

The mechanism of the cycloaddition reaction between singlet dichlorosilylenesilylene (Cl₂Si=Si:)→Cl₂Si=Si: and aldehyde has been investigated with the CCSD(T)//MP2/6-31G* method. From the potential energy profile, it could be predicted that the reaction has one dominant reaction pathway. The reaction rules presented is that the two reactants firstly form a four-membered ring silylene through the [2+2] cycloaddition reaction. Because of the 3p unoccupied orbital of Si: atom in the four-membered ring silylene and the π orbital of aldehyde forming a π → p donor–acceptor bond, the four-membered ring silylene further combines with aldehyde to form an intermediate. Because the Si: atom in the intermediate happens sp ³ hybridization after transition state, then the intermediate isomerizes to a spiro-heterocyclic ring compound involving Si via a transition state.     

Ab initio Study on Mechanism of Forming a Silicic Bis-Heterocyclic Compound Between Dimethylmethylenesilylene and Ethene

The mechanism of the cycloaddition reaction of forming a silicic bis-heterocyclic compound between singlet dimethylmethylenesilylene (Me₂C=Si:) and ethene has been investigated with the CCSD(T)//MP2/6-31G^* method. From the potential energy profile, it can be predicted that, this reaction has one dominant channel. The presented rule of this dominant channel: the 3p unoccupied orbital of Si in dimethylmethylenesilylene and the π orbital of ethene forming the π→p donor-acceptor bond, resulting in the formation of three-membered ring intermediate (INT1); INT1 then isomerizes to a four-membered ring silylene (P2), which is driven by ring-enlargement effect; due to sp³ hybridization of Si atom in P2, P2 further combines with ethene to form a silicic bis-heterocyclic compound.     

Theoretical study of mechanism of cycloaddition reaction between 2,2-dimethyl(2-germavinylidene) [(CH3)2Ge=C:] and formaldehyde

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.     

Ab initio study on the mechanism of cycloaddition reaction between H<Subscript>2</Subscript>Si=Si: and formaldehyde

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.     

An amidinate-stabilized germatrisilacyclobutadiene ylide

The synthesis and characterization of new amidinate-stabilized germatrisilacyclobutadiene ylides [L(3)Si(3)GeL'] (L=PhC(NtBu)(2); L'=?L; ?=Ge (3), Si (7)) are described. Compound 3 was prepared by the reaction of [LSi-SiL] (1) with one equivalent of [LGe-GeL] (2) in THF. Compound 7 was synthesized by the reaction of 2 with excess 1 in THF. The bisamidinate germylene [L(2)Ge:] (4) is a by-product in both reactions. Moreover, compound 7 was prepared by the reaction of 3 with one equivalent of 1 in THF. Compounds 3 and 7 have been characterized by NMR spectroscopy, X-ray crystallography, and theoretical studies. The results show that compounds 3 and 7 are not antiaromatic. The puckered Si(3) Ge four-membered rings in 3 and 7 have a ylide structure, which is stabilized by amidinate ligands and the electron delocalization within the Si(3) Ge four-membered ring.     

Theoretical Study of the Mechanism of Cycloaddition Reaction between Silylene Silylene (H2SiSi:) and Acetone

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).     

Alkyne Addition and Insertion Reactions of [(Me3Si)3Si]2Ge⋅PMe3

Silylated germylene–PMe₃ adducts exchange their phosphane moiety smoothly for an N‐heterocyclic carbene or isocyanide species to form their respective base adducts. Reaction of the silylated germylene–PMe₃ adducts with monosubstituted alkynes produce germylene adducts with the alkyne inserted into a Ge?Si bond. A computational study of this process provides evidence for the initial formation of a germirene, which rearranges to a vinylgermylene species. The thermodynamic driving force for this reaction is provided by subsequent adduct formation with PMe₃. Reaction of the PMe₃ adduct of bis[(trimethylsilyl)silyl]germylene with disubstituted alkynes leads to the formation of stable germirenes, which can be isomerized further to silagermetes.