Theoretical studies on the imine germylenoid HNGeNaF and its insertion reaction with R–H (R=F, OH, NH2, CH3)

Theoretical prediction on the insertion reactions of stannylenoid H2SnLiF with CH3X and SiH3X (X = F, Cl, Br)

Density functional theory was used to study the insertion reaction of stannylenoid H2SnLiF with CH3X, SiH3X (X = F, Cl, Br). Comparing the reaction barrier of H2SnLiF with CH3X, SiH3X, it can be found that the order of the difficulty of insertion reaction is F > Cl > Br. The insertion reaction potential barrier of SiH3X is lower than that of CH3X, which means that SiH3X is easier to react. According to the calculation results, the reaction law in THF solvent is consistent with that in vacuum, while in THF solvent, the barrier is lower and therefore more prone to reactions. This work provides theoretical support for the reaction properties of stannylenoids.

Diverse reactions of a fluorostannylenoid towards ethynes

Fluoro(dialkyl)stannylenoid 2 exhibits unique reactivity towards ethynes with acetylenic hydrogen and those with trimethylsilyl groups, though the corresponding free dialkylstannylene 1 is inactive against those ethynes. Stannylenoid 2 reacts smoothly with gaseous ethyne and phenylethyne at room temperature, giving the corresponding diethynylstannanes, di(phenylethynyl)stannane 3 and diethynylstannane 6, respectively, in good yields with the concomitant evolution of H₂. Trimethylsilyl-substituted ethynes such as 1-trimethylsilyl-(2-phenyl)ethyne and 1,2-bis(trimethylsilyl)ethyne react similarly to give 3 and bis(trimethylsilylethynyl)stannane 8, respectively. Rather unexpectedly, the reaction of 2 with (trimethylsilyl)ethyne affords 1,2-bis(ethenylstannyl)ethyne 7 in a good yield. The reactions of 2 with methyl and ethyl propynoates give the same products 4 and 5 as those obtained during the reaction of dialkylstannylene 1 without CsF. Pathways involving the nucleophilic attack of cesium acetylide to an ethyne-complexed stannylene were proposed, while the detailed mechanisms remain unknown. The structure of 7 was studied by single crystal X-ray diffraction analysis.

The addition reactions of germylenoid H2GeAlCl3 with ethylene: a theoretical investigation

Theoretical calculations using the M062X and QCISD methods were performed on the addition reactions of the aluminum germylenoid H₂GeAlCl₃ with ethylene. The most two stable structures of germylenoid H₂GeAlCl₃, i.e., the p-complex and three-membered ring structures, respectively, were employed as reactants. The calculated results indicate that, for the p-complex, H₂GeAlCl₃ there are two pathways, I and II, of which path I involves just one transition state, while path II involves two transition states between reactants and products. Comparing the reaction barrier heights of path I (44.6 kJ mol^-1) and II (37.6 kJ mol^-1), the two pathways are competitive, with similar barriers under the same conditions, while for the three-membered ring structure, another two pathways, III and IV, also exist. Path III has one transition state; however, in path IV, two transition states exist. By comparing their barrier heights, path III (barrier height 39.2 kJ mol^-1) could occur more easily than path IV (barrier height 92.8 kJ mol^-1). Considering solvent effects on these addition reactions, the PCM model and CH₂Cl₂ solvent were used in calculations, and the calculated results demonstrate that CH₂Cl₂ solvent is unfavorable for the reactions, except for path II. In CH₂Cl₂ solvent, paths II and III are more favorable than paths I and IV.

Reversible Stannylenoid Formation from the Corresponding Stannylene and Cesium Fluoride

A fluorostannylenoid (Cs⁺ [R₂ SnF]^- (9), R₂ =(TMS)₂ CCH₂ CH₂ C(TMS)₂ ) was prepared by reacting a stable dialkylstannylene (R₂ Sn (8), R₂ =(TMS)₂ CCH₂ CH₂ C(TMS)₂ ) with cesium fluoride at room temperature in THF. While 9 is stable in THF and DME, removal of the solvent leads to the regeneration of stannylene 8. No reaction occurred when 8 was treated with CsF in a hydrocarbon solvent. Addition of dibenzo-21-crown-7 ether to the THF solution of stannylenoid 9 followed by usual workup affords the corresponding crystalline stannylenoid crown ether complex, the X-ray structural analysis of which revealed a fluorine-bridged contact ion-pair structure. The reaction of 9 with excess phenylacetylene gives the corresponding di(phenylethynyl)stannane.

Theoretical prediction on the addition reaction of germylenoid H2GeFMgF with ethylene

The addition reaction of germylenoid H2GeFMgF with ethylene (C2H4) was first investigated in this work. All of the stationary points were optimized using the M062X method in conjunction with the 6-311[Formula: see text]G (d, p) basis set and the corresponding energies were calculated using the QCISD method with the 6-311[Formula: see text]G (d, p) basis set. The calculated results demonstrated that there are two different channels in the addition reaction of H2GeFMgF with C2H4, while only the channel I is feasible once the C2H4approaches H2GeFMgF in the proper conditions. The solvent effect upon the addition reaction was also investigated using PCM model. The results demonstrated that the tetrahydrofuran (THF) solvent could accelerate the addition reaction.

New insights into the insertion reactions of germylenoid H2GeLiF with RH (R = F, OH, NH2)

In the present work, a new pathway of the insertion reactions of H2GeLiF with RH (R = F, OH, NH2) was investigated using DFT B3LYP and QCISD methods. The geometries of the stationary points on the potential energy surfaces in the reactions were optimized at the B3LYP/6-311 + G (d, p) level and then the single-point energies were calculated at the QCISD/6-311++G (d, p) level. The calculated results indicated that the initial step of all the reactions is the isomerization of the p-complex structure to a three-membered-ring structure. After isomerization, the insertion reactions of three-membered-ring H2GeLiF with RH (R = F, OH, NH2) take place. The QCISD/6-311++G (d, p)//B3LYP/6-311 + G (d, p) calculated potential energy barriers of the three reactions were 89.77, 137.40, and 167.45 kJ mol(-1), respectively. Under the same situation, the insertion reactions should occur easily in the following order H-F > H-OH > H-NH2. Compared with the direct insertion reactions of H2GeLiF with RH (R = F, OH, NH2), the two-step insertions have lower activation barriers and should be more favorable.

Structure ofH2GeFMgFand its insertion reactions withRH(R=F,OH,NH2)

The structures of the germylenoid H2GeFMgF and its insertion reactions with RH ( R = F , OH , NH2) were studied using the DFT B3LYP and QCISD approaches for the first time. The geometries of all of the stationary points were optimized at the B3LYP/6-311+G (d, p) level of theory. And then the QCISD/6-311++G (d, p) single-point energies were calculated. The solvent effects on the geometries and insertion reactions were also computed using the PCM model. The calculated results suggested that H2GeFMgF had three equilibrium configurations, in which the p-complex structure had the lowest energy and was the most stable structure. The isomerization reactions among the three complexes had been studied. For the insertion reactions of H2GeFMgF with RH ( R = F , OH , NH2), along the potential energy surface, there were one transition state and one intermediate which connected the reactants and the products. For the three insertion reactions the mechanisms are identical. However, under the same conditions the insertion reactions should occur easily in the order of H - F > H - OH > H - NH2. The solvent effect calculations suggested the larger the solvent polarity is, the easier the reaction will be.

A new reaction mode of germanium-silicon bond formation: insertion reactions of H₂GeLiF with SiH₃X (X = F, Cl, Br)

A combined density functional and ab initio quantum chemical study of the insertion reactions of the germylenoid H2GeLiF with SiH3X (X = F, Cl, Br) was carried out. The geometries of all the stationary points of the reactions were optimized using the DFT B3LYP method and then the QCISD method was used to calculate the single-point energies. The theoretical calculations indicated that along the potential energy surface, there were one precursor complex (Q), one transition state (TS), and one intermediate (IM) which connected the reactants and the products. The calculated barrier heights relative to the respective precursors are 102.26 (X = F), 95.28 (X = Cl), and 84.42 (X = Br) kJ mol(-1) for the three different insertion reactions, respectively, indicating the insertion reactions should occur easily according to the following order: SiH3-Br > SiH3-Cl > SiH3-F under the same situation. The solvent effects on the insertion reactions were also calculated and it was found that the larger the dielectric constant, the easier the insertion reactions. The elucidations of the mechanism of these insertion reactions provided a new reaction model of germanium-silicon bond formation.

THEORETICAL INVESTIGATION ON THE INSERTION REACTIONS OF THE GERMYLENOIDH2GeLiFWITHRH(R=Cl,SH,PH2)

The insertion reactions of the germylenoid H2GeLiF with RH (R = Cl, SH , PH2) were studied for the first time 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 indicated that the mechanisms of the insertion reactions of H2GeLiF with HCl , H2S , and PH3are identical to each other. The QCISD/6-311++G(d,p)//B3LYP/6-311+G(d,p) calculated potential energy barriers of the three reactions are 81.80, 123.39 and 205.56 kJ/mol, and the reaction energies for the three reactions are -58.74, -33.51 and -13.35 kJ/mol, respectively. Under the same situation, the insertion reactions should occur easily in the following order H–Cl > H–SH > H–PH2. The insertion reaction in THF solution is easier than in gas phase.