Bing-Fei Yan

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 GERMYLENOID H2GeLiF WITH RH (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 PH3 are 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.

Structures of the germylenoid H2GeZnCl2 and its addition reactions with ethylene

Density functional theory calculations for the structures of the zinc germylenoid H2GeZnCl2 and its addition reactions with ethylene were carried out firstly in the present work. Two isomers of H2GeZnCl2: deformed tetrahedral structure (1) and p-complex structure (2) were found, in which the structure 1 is lower in energy than the structure 2. Because the isomerization reactions between structure 1 and 2 are difficult, these two structures can exist independently. The addition reactions of the two structures with ethylene were investigated, respectively, at the same level. The results revealed that reactions of structure 1 with ethylene could occur through two pathways (path A and B) and the path A is feasible, while reaction of structure 2 with ethylene could take place only via one pathway (path C). Solvent effects upon the equilibrium structures and the addition reactions were considered by coordination of one THF molecule to Zn atom of germylenoid species. The calculated results demonstrated that one THF solvated isomers can exist independently. The path A, B, and C of one THF solvated addition reactions are easier than that in vacuum.

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+G (d, p) basis set and the corresponding energies were calculated using the QCISD method with the 6-311++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 C2H4 approaches 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.

Structures of the phosphinidene germylenoid HP=GeLiF and its cycloaddition reaction with ethylene

The structures of phosphinidene germylenoid HP=GeLiF were studied for the first time by using DFT (density functional theory) calculations. The geometries were optimized at the B3LYP/6-311+G (d, p) level at first and then the single-point energies were calculated at QCISD/6-311++G (d, p) level. Theoretical calculations predicted that HP=GeLiF has two equilibrium structures, the p-complex (1) and the three-membered-ring (2) structures, in which structure 1 has the lower energy and is more stable than 2. To exploit the reactivity of HP=GeLiF, the cycloaddition reaction of 1 and ethylene was investigated at the same level of theory. From the potential energy profile, we predicted that the cycloaddition reaction has one dominant reaction pathway. The calculated result shows that the dominant reaction pathway is a [2 + 2] cycloaddition reaction which is the interaction of two π bonds in HP=GeLiF and ethylene molecule, and a four-membered-ring P-heterocyclic germylene is formed. Since sp3 hybridization of Ge atom in this four-membered-ring germylene, it may further react with another ethylene and finally forming a spiro-Ge-heterocyclic compound involving phosphorus. This means that this reaction involves a [2 + 2] cycloaddition as the initial step, and then a [2 + 1] cycloaddition carried out.

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

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.