Theoretical study on germylenoid H2GeFBeF

The germylenoid H₂GeFBeF was studied by using the DFT B3LYP and QCISD methods in gas phase and in benzene, diethylether, tetrahydrofuran, acetone, and dimethyl sulphoxide solvents. Geometry optimization calculations indicated that H₂GeFBeF has three equilibrium configurations, in which the p-complex structure is the lowest in energy and is the most stable structure. The solvent effect on the geometries, energies, and isomerization reactions were discussed. For the stablest structure, the infrared spectrum was simulated.     

The insertion and H<Subscript>2</Subscript> elimination reactions of H<Subscript>2</Subscript>GeFMgF germylenoid with RH (R = Cl,SH, PH<Subscript>2</Subscript>)

In present paper, the insertion and H₂ elimination reactions of H₂GeFMgF germylenoid with RH (R = Cl, SH, PH₂) were investigated by means of B3LYP and QCISD calculation methods. One transition state and one intermediate were found along the potential energy surface in each insertion reaction, while for the H₂ elimination reactions, only one transition state was found between the reactants and products in each reaction process. Both for the insertion and H₂ elimination reactions, RH reactivity increases in the following order: H–Cl > H–SH > H–PH₂. The insertion and H₂ elimination reactions were compared, and the results demonstrated that the H₂ elimination should be more favorable than the corresponding insertion. The solvent effects on these two types of reactions were considered. The calculated results indicated that the solvents could accelerate the reactions by reducing their barrier heights.     

DFT Studies on the addition reaction between germylene and furan

The mechanism of the addition reaction of germylene H₂Ge and furan has been investigated with B3LYP/6-311+G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. From the surface energy profile, it can be predicted that there are four reactions (1)–(4). Reactions (1) and (2) are similar, which are reactions between H₂Ge and C=C of isolated furan. Furthermore, H₂Ge can react with oxygen atom of furan to form a stable complex H₂Ge-Furan. Reactions (3) and (4) are similar, which are reactions between H₂Ge and C=C of the complex H₂Ge-Furan. All the reactions consist of two steps: the two reactants first form an intermediate (INT) through a barrier-free exothermic reaction; this intermediate then isomerizes to a product (P) via a transition state (TS). The article is published in the original.     

Reaction Mechanism of the Hydrogermylation/Hydrostannylation of Unactivated Alkenes with Two‐Coordinate EII Hydrides (E=Ge,Sn): A Theoretical Study

Quantum chemical calculations using density functional theory with the TPSS+D3(BJ) and M06‐2X+D3(ABC) functionals have been carried out to understand the mechanisms of catalyst‐free hydrogermylation/hydrostannylation reactions between the two‐coordinate hydrido‐tetrylenes :E(H)(L⁺) (E=Ge or Sn, L⁺=N(Ar⁺)(SiiPr₃); Ar⁺=C₆H₂{C(H)Ph₂}₂iPr‐2,6,4) and a range of unactivated terminal (C₂H₃R, R=H, Ph, or tBu) and cyclic [(CH)₂(CH₂)₂(CH₂)_n, n=1, 2, or 4] alkenes. The calculations suggest that the addition reactions of the germylenes and stannylenes to the cyclic and acyclic alkenes occur as one‐step processes through formal [2+2] addition of the E?H fragment across the C?C π bond. The reactions have moderate barriers and are weakly exergonic. The steric bulk of the tetrylene amido groups has little influence on the activation barriers and on the reaction energies of the anti‐Markovnikov pathway, but the Markovnikov addition is clearly disfavored by the size of the substituents. The addition of the tetrylenes to the cyclic alkenes is less exergonic than the addition to the terminal alkenes, which agrees with the experimentally observed reversibility of the former reactions. The hydrogermylation reactions have lower activation energies and are more exergonic than the stannylene addition. An energy decomposition analysis of the transition state for the hydrogermylation of cyclohexene shows that the reaction takes place with simultaneous formation of the Ge?C and (Ge)H?C′ bonds. The dominant orbitals of the germylene are the σ‐type lone pair MO of Ge, which serves as a donor orbital, and the vacant p(π) MO of Ge, which acts as acceptor orbital for the π* and π MOs of the olefin. Inspection of the transition states of some selected reactions suggests that the differences between the activation energies come from a delicate balance between the deformation energies of the interacting species and their interaction energies.     

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.     

Theoretical investigation on H2 elimination reactions of germylenoid H2GeLiF with RH (R = F, OH, and NH2)

The H₂ elimination reactions of the germylenoid H₂GeLiF with RH (R = F, OH, NH₂) have been studied by using the DFT B3LYP and QCISD methods. The calculated results indicate that all the mechanisms of the three reactions are identical to each other and under the same condition the H₂ elimination reactions should occur easily in the order of H-F > H-OH > H-NH₂. In THF solvent the H₂ elimination reactions get more difficult than in gas phase. Compared with the insertion reactions of H₂GeLiF with RH (R = F, OH, NH₂), the H₂ elimination reactions have the lower activation barriers and should be more favorable.     

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.     

Reaction Mechanism of the Symmetry‐Forbidden [2+2] Addition of Ethylene and Acetylene to Amido‐Substituted Digermynes and Distannynes Ph2NEENPh2, (E=Ge,Sn): A Theoretical Study

Quantum chemical calculations of reaction mechanisms for the formal [2+2] addition of ethylene and acetylene to the amido‐substituted digermyne and distannyne Ph₂N?EE?NPh₂ (E=Ge, Sn) have been carried out by using density functional theory at the BP86/def2‐TZVPP level. The nature and bonding situations were studied with the NBO method and with the charge and energy decomposition analysis EDA‐NOCV. The addition of ethylene to Ph₂N?EE?NPh₂ takes place through an initial [2+1] addition to one metal atom and consecutive rearrangement to four‐membered cyclic species, which feature a weak E?E bond. Rotation about the C?C bond with concomitant rupture of the E?E bond leads to the 1,2‐disubstituted ethanes, which have terminal E(NPh₂) groups. The overall reaction Ph₂N?EE?NPh₂+C₂H₄→(Ph₂N)E?C₂H₄?E(NPh₂) has very low activation barriers and is slightly exergonic for E=Ge but slightly endergonic for E=Sn. The analysis of the electronic structure shows that there is charge donation of nearly one electron to the ethylene moiety already in the first part of the reaction. The energy partitioning analysis suggests that the HOMO(Ph₂N?EE?NPh₂)→LUMO(C₂H₄) interaction has a similar strength as the HOMO(C₂H₄)→LUMO(Ph₂N?EE?NPh₂) interaction. The [2+2] addition of acetylene to Ph₂N?EE?NPh₂ also takes place through an initial [2+1] approach, which eventually leads to 1,2‐disubstituted olefins (Ph₂N)E?C₂H₂?E(NPh₂). The formation of the energetically lowest lying conformations of cis‐(Ph₂N)E?C₂H₂?E(NPh₂), which occurs with very low activation barriers, is clearly exergonic for the germanium and the tin compound. The trans‐coordinated isomers of (Ph₂N)E?C₂H₂?E(NPh₂) are slightly lower in energy than the cis form but they are separated by a substantial energy barrier for the rotation about the C?C bond. The energy decomposition analysis indicates that the initial reaction takes place under formation of electron‐sharing bonds between triplet fragments rather than HOMO–LUMO interactions.     

Quantum chemical study of interactions of carbenes and their analogs of the EH2 and EHX types (E = Si, Ge, Sn; X = F, Cl, Br) with HX and H2, respectively: the insertion and substituent exchange reactions

Interactions of carbenes and carbene analogs EH₂ and EHX with HX and H₂ (E = C, Si, Ge, Sn; X = F, Cl, Br), respectively, were studied by quantum chemical methods. Theoretical analysis of the carbene and silylene systems was carried out at the G3 level of theory using the MP2(full)/6?C31G(d) calculated geometries and vibrational frequencies. The stannylene systems were examined at the MP2 level using a modified LANL2DZ basis set for the Sn atoms and the 6?C31+G(d,p) basis sets for other atoms. Transformations in the germylene systems were studied within the framework of both approaches, which gave similar results. This allowed one to compare the reaction pathways and their energy profiles for the whole series of systems. In addition to the insertions into the H-X and H-H bonds, the exchange reactions resulting in interconversions of EH₂ and EHX can proceed in the systems under consideration. The effects of the nature of the E and X atoms on the reaction barriers and exothermicity of both the insertion and exchange reactions are analyzed. Possible role of radical processes in these systems is assessed.     

Germanium-oxygen interactions in acyl-substituted germyleneazines L2GeNNC(COX)(COY)

MNDO calculations have been carried out on the reactions of the electron-rich germylene L₂Ge [L=(H₃Si)₂N] with diazo compounds, as models for the experimentally observed reactions of L₂Ge [L=(Me₃Si)₂N]. The most stable form of the 11 adduct of L₂Ge with N₂C(COOMe)₂ is found to have a cyclic configuration resulting from a strong intramolecular interaction between the oxygen of one of the carbonyl groups and the germanium atom. Protonation of this cyclic adduct occurs at nitrogen, giving an intermediate, addition to which of nucleophiles X^– provides acyclic L₂Ge(X)NHN(COOMe)₂, as observed experimentally. Two similar cyclic adducts are formed between L₂Ge and N₂C(COCH₃)(COOCH₃), the most stable of which provides, after a proton shift, the observed 1,3,4,2-oxadiazagermine system . Adduct formation between Me₂Si=NSiMe₃ and simple Lewis bases (H₂O, NH₃, THF, H₂CO) is calculated to be strong, but the corresponding adducts of Me₂Ge=NSiMe₃ are very weak: much stronger adducts are predicted for L₂GeNNC(COOMe)₂.     

Low coordinate germanium and tin compounds (ArO)2ME and (ArO)2MM′Ln M=Ge, Sn; E=S, Se, –NSiMe3 M′=Cr, W, Fe, Pt [Ar=2,4,6-tris((dimethylamino)methyl)phenyl-]

The reactions of the divalent species (ArO)₂M (Ar=2,4,6-[(CH₃)₂NCH₂]₃C₆H₂; M=Ge, Sn) with either Me₃SiN₃, elemental S₈, Se or transition metal complexes M′(CO)_n+1 (M′=Fe, n=4; M′=Cr, W; n=5) (Ph₃P)₂Pt·C₂H₄ have resulted in the isolation of either the new stable formal metallanimines (ArO)₂M=N–SiMe₃, germanethione, -selone (ArO)₂Ge=E (E=S, Se) (the expected formations of the stannanethione and -selone were not observed), or the (ArO)₂M=M′(CO)_n, (ArO)₂M=Pt(PPh₃)₂ complexes, respectively. The direct oxidation of the (ArO)₂M species with various oxidizing agents led to the formation of the corresponding metalloxanes [(ArO)₂M–O–]₂. All of the chalcogenido- and transition metal–metal 14 complexes have been physicochemically and chemically characterized. The reactions of the (ArO)₂Ge=E (E=S, Se) compounds with 3,5-di-tert-butyl-1,2-benzoquinone produced, by extrusion of sulfur or selenium, the dioxametalloles corresponding to the formal addition of the divalent species (ArO)₂M to the benzoquinone. A substitution reaction of chalcogen (S/Se) has been observed permitting to go from germaneselone to germanethione.     

Formation and Dissociation Mechanism of Amide Complexes,IV. Protonation and deprotonation of the Cu2+ and Ni2+ complexes of 3,7-diazanonanediamide and 3,7-diazanonane-N,N′-diethylamide

The protonation and deprotonation rates of the coordinated amide groups in the Ni²⁺ and Cu²⁺ complexes of 3,7-diazanonanediamide (DANA) and in the Cu²⁺ complex of 3,7-diazanonane-N,N′-diethylamide (DANEA) have been studied by stopped-flow techniques. For the interconversion M(H_?2L) ? ML, two consecutive reactions are observed in the case of Cu²⁺ with DANA or DANEA, whereas there is only one reaction for Ni²⁺ with DANA. Cu(H_?2DANEA) is unusually labile, indicating a strong interaction between the N-ethyl groups. The conversion of the O- into the N-coordinated amide groups in NiDANA²⁺ is 25 times slower than in CuDANA²⁺. In the case of Ni²⁺ this excludes a step with water substitution, which is involved in one of the reaction paths observed for the Cu²⁺ complexes, since the rates of water exchange differ by a factor of 10⁵ for the two metal ions.     

Theoretical study on the insertion reactions of the germylenoid H2GeClMgCl with RH (R = F, OH, NH2)

The insertion reactions of the germylenoid H₂GeClMgCl with RH (R = F, OH, NH₂) have been studied by using the DFT B3LYP and QCISD methods. The geometries of the stationary points on the potential energy surfaces of the reactions were optimized at the B3LYP/6-311+G(d, p) level of theory. The calculated results indicate that all the mechanisms of the three insertion reactions are identical to each other. The QCISD/6-311++G(d, p)//B3LYP/6-311+G(d, p) calculated potential energy barriers for the three insertion reactions of R = F, OH, and NH₂ are 164.62, 193.30, and 200.73 kJ mol^?1, and the reaction energies for the three reactions are ?57.46, ?35.65, and ?22.22 kJ mol^?1, respectively. Under the same situation, the insertion reactions should occur easily in the following order H-F > H-OH > H-NH₂. In THF solvent the insertion reactions get more difficult than in gas phase.     

三重态类硅烯HB＝SiLiF的结构及其与R—H(R=F,OH,NH_2)的插入反应

用密度泛函理论(DFT)和二次组态相互作用(QCISD)方法研究了三重态类硅烯HB=SiLiF的结构及其与RH(R=F,OH,NH2)的插入反应.计算结果表明,类硅烯HB=SiLiF有三种平衡构型,其中四元环构型能量最低,是其存在的主要构型.HB=SiLiF与HF,H2O和NH3发生插入反应的机理相同.QCISD/6-311++G(d,p)//B3LYP/6-311+G(d,p)计算的三个反应的势垒分别为124.85,140.67和148.16kJ·mol-1,反应热分别为-2.22,20.08和23.22kJ·mol-1.相同条件下发生插入反应时,反应活性都是H—FH—OHH—NH2.     

Density functional study on the bromination of heteroelement-substituted acetylenes

The reactions of heteroelement-containing alkynes H₃SiC≡CH and R₃MC≡CPh [R₃M = H₃Si, Et₃Si, Et₃Ge, (MeO)₃Si, (EtO)₃Ge, N(CH₂CH₂O)₃Si, N(CH₂CH₂O)₃Ge, Bu₃Sn] with one and two bromine molecules were studied in terms of the density functional theory. Transition states along reaction channels leading to products of both addition at the triple bond (cis- and trans-dibromoalkenes and 1,1-dibromoalkenes) and cleavage of the M-C≡ bond were localized.     

Free radical decomposition of bromoacetonitrile in liquid cyclohexane

The kinetics of the gamma radiation induced free radical chain decomposition of BrCH₂CN in liquid cyclohexane (RH) was investigated over the temperature range of 60–170°C. In addition competitive experiments in the presence of CCl₄ were carried out between 80 and 180°C. For the reactions the following Arrhenius expressions were derived: where θ = 2.303RT in kcal/mol. The effect of CN substitution on the activation energies of reactions (2) and (3) was evaluated based on the present and previously published results. The CN group effect on halogen atom abstraction [reaction (2)] is discussed in terms of inductive and enthalpic factors. The differences E₃ ? E(CH₃ + RH) and E(CCl₂CN + RH) ? E(CCl₃ + RH), which yield a value of about 5.5 kcal/mol, are considered to reflect the cyano stabilization effect at the radical center confirming D(CH₂(CN)–H) ～ 93 kcal/mol.     

Yttrium pyrogermanate,Y2Ge2O7

The structure of diyttrium digermanate, Y₂Ge₂O₇, has been determined in the tetragonal space group P4₃2₁2. It contains one Y, one Ge (both site symmetry 1 on general position 8b) and four O atoms [one on special position 4a (site symmetry ..2) and the remaining three on general positions 8b]. The basic units of the structure are isolated Ge₂O₇ groups, sharing one common O atom and displaying a Ge—O—Ge angle of 134.9 (3)°, and infinite helical chains of pentagonal YO₇ dipyramids, parallel to the 4₃ screw axis. The crystal investigated here represents the left‐handed form of the tetragonal R₂Ge₂O₇ compounds (R = Eu³⁺, Tb³⁺, Er³⁺, Tm³⁺ and Lu³⁺).     

Stable N‐Heterocyclic Germylenes of the Type [Fe{(η5‐C5H4)NR}2Ge] and Their Oxidation Reactions with Sulfur,Selenium, and Diphenyl Diselenide

Three new N‐heterocyclic germylenes of the type [Fe{(η⁵‐C₅H₄)NR}₂Ge] ( 1R Ge) containing particularly bulky alkyl [R = 2‐adamantyl (Ad), 1,1,2,2‐tetramethylpropyl (Pr*)] or aryl substituents [R = 2,6‐diisopropylphenyl (Dipp)] were prepared and structurally characterized, in two cases (R = Ad, Dipp), by single‐crystal X‐ray diffraction. Together with the previously described homologues with R = trimethylsilyl (TMS), tert‐butyl (tBu), and mesityl (Mes) their oxidative addition reactions with S₈ and Se₈ were studied, which afforded compounds of the type [ 1R Ge(μ‐E)]₂ (E = S, Se). The low solubility of most of these products severely hampered their purification and characterization. Nevertheless, their structural characterization by single‐crystal X‐ray diffraction was possible in six cases (E = S, R = Ad, Pr*; E = Se, R = Ad, Pr*, Mes, Dipp). No solubility problems were encountered in oxidative addition reactions with diphenyl diselenide, affording products of the type 1R Ge(SePh₂)₂, whose crystal structures could be determined in four cases (R = TMS, tBu, Mes, Dipp). Short intramolecular CH ··· Se contacts compatible with hydrogen bonds were observed for [ 1Ad Ge(μ‐Se)]₂, [ 1Pr* Ge(μ‐Se)]₂, and 1tBu Ge(SePh₂)₂.     

Germanium(II) pseudohalides: Ge(CN)2, Ge(NCO)2 and Ge(NCS)2; syntheses and reactivities

The hitherto unknown germanium(II) pseudohalides: Ge(CN)₂, Ge(NCO)₂ and Ge(NCS)₂, have been prepared by reactions of germanium(II) halides with corresponding silver or potassium salts; they are stable in tetrahydrofuran or acetone solution in which they are extremely sensitive to moisture, and they undergo cycloaddition, insertion, and Lewis acid-base reactions characteristic of highly reactive germylenes. Infrared spectra indicate that in tetrahydrofuran solution Ge(CN)₂ is the normal cyanide, whereas Ge(NCO)₂ and Ge(NCS)₂ are the isocyanate and isothiocyanate, respectively.