The effect of substitution on the potential energy surfaces of RE13≡BiR (E13 = B, Al, Ga, In, and Tl; R = F, OH, H, CH3, SiH3, Tbt, Ar*, SiMe(SitBu3)2, and SiiPrDis2) is investigated using density functional theories (M06-2X/Def2-TZVP, B3PW91/Def2-TZVP, and B3LYP/LANL2DZ+dp). The theoretical results suggest that all of the triply bonded RE13≡BiR molecules prefer to adopt a bent geometry (i.e., ∠RE13Bi ≈ 180° and ∠E13BiR ≈ 90°), which agrees well with the bonding model (model (B)). It is also demonstrated that the smaller groups, such as R = F, OH, H, CH3, and SiH3, neither kinetically nor thermodynamically stabilize the triply bonded RE13≡BiR compounds, except for the case of H3SiB≡BiSiH3. Nevertheless, the triply bonded RʹE13≡BiRʹ molecules that feature bulkier substituents (Rʹ = Tbt, Ar*, SiMe(SitBu3)2, and SiiPrDis2) are found to have the global minimum on the singlet potential energy surface and are both kinetically and thermodynamically stable. In other words, both the electronic and the steric effects of bulkier substituent groups play an important role in making triply bonded RE13≡BiR (Group 13–Group 15) species synthetically accessible and isolable in a stable form.
Part of the book: Recent Progress in Organometallic Chemistry
The potential energy surfaces of the oxidative addition reactions, L2M + imidazoliumcation → product and CpM′L + imidazolium cation → product (M = Ni, Pd, Pt; M′ = Co, Rh, Ir; Cp = η5-C5H5; L = 1,3-aryl-N-heterocyclic carbene (NHC), aryl = 2,4,6-trimethylphenyl), are studied at the M06-L/Def2-SVP level of theory. The theoretical findings show that the singlet-triplet splitting (∆Est = Etriplet − Esinglet) for the L2M and CpM′L species can be used to predict the reactivity for their oxidative additions. That is to say, current theoretical evidence suggests that both a 14-electron L2M complex and a 16-electron CpM′Lcomplex with a better electron-donating ligand L (such as NHC) result in a reduced ∆Est value and facilitate the oxidative addition to the saturated C─H bond. The theoretical results for this study are in good agreement with the obtainable experimental results and allow a number of predictions to be made.
Part of the book: Descriptive Inorganic Chemistry Researches of Metal Compounds
The effect of substitution on the potential energy surfaces of RE13≡AsR (E13 = group 13 elements; R = F, OH, H, CH3, and SiH3) is determined using density functional theory (M06‐2X/Def2‐TZVP, B3PW91/Def2‐TZVP, and B3LYP/LANL2DZ+dp). The computational studies demonstrate that all triply bonded RE13≡AsR species prefer to adopt a bent geometry that is consistent with the valence electron model. The theoretical studies also demonstrate that RE13≡AsR molecules with smaller substituents are kinetically unstable, with respect to the intramolecular rearrangements. However, triply bonded R′E13≡AsR′ species with bulkier substituents (R′ = SiMe(SitBu3)2, SiiPrDis2, and NHC) are found to occupy the lowest minimum on the singlet potential energy surface, and they are both kinetically and thermodynamically stable. That is to say, the electronic and steric effects of bulky substituents play an important role in making molecules that feature an E13≡As triple bond as viable synthetic target.
Part of the book: Chemical Reactions in Inorganic Chemistry
A density functional study of {η2-(X@Cn)}ML2 complexes with various cage sizes (C60, C70, C76, C84, C90, C96), encapsulated ions (X = F−, 0, Li+) and metal fragments (M = Pt, Pd) is performed, using M06/LANL2DZ levels of theory. The importance of π back-bonding to the thermodynamic stability of fullerene-transition metal complexes ({η2-(X@Cn)}ML2) and the effect of encapsulated ions, metal fragments and cage sizes on the π back-bonding are determined in this study. The theoretical computations suggest that π back-bonding plays an essential role in the formation of fullerene-transition metal complexes. The theoretical evidence also suggests that there is no linear correlation between cage sizes and π back-bonding, but the encapsulated Li+ ion enhances π back-bonding and F− ion results in its deterioration. These computations also show that a platinum center produces stronger π back-bonding than a palladium center. It is hoped that the conclusions that are provided by this study can be used in the design, synthesis and growth of novel fullerene-transition complexes.
Part of the book: Fullerenes and Relative Materials
The mechanism of the photochemical fragmentation reaction is investigated theoretically using the model system, hydantoin, using the CAS(22,16)/6-31G(d) and MP2-CAS-(22,16)/6-311G(d)//CAS(22,16)/6-31G(d) methods. The model investigation demonstrates that the preferred reaction route for the photofragmentation reaction is as follows: hydantoin → Franck-Condon region → conical intersection → fragment photoproducts (i.e., CO, isocyanic acid, and methylenimine). The theoretical finding additionally suggests that no organic radicals exist during the fragmentation reaction. Moreover, due to the high activation energy, the theoretical evidences suggest that it would be difficult to yield the three fragments under the thermal reaction. All the above theoretical observations are consistent with the available experimental results.
Part of the book: Photochemistry and Photophysics
The potential energy surfaces for the chemical reactions of group 14 carbenes were studied using density functional theory (B3LYP/LANL2DZ + dp). Five group 14 carbene species containing a seven-member ring, 7-Rea-E, where E = C, Si, Ge, Sn and Pb, were chosen as model reactants for this work. Three types of chemical reactions (water addition, imine cycloaddition and dimerization) were used to study the reactivity of these 7-Rea-E molecules. Present theoretical investigations suggest that the relative reactivity of carbenes decreases in the order: 7-Rea-C > 7-Rea-Si > 7-Rea-Ge > 7-Rea-Sn > 7-Rea-Pb. That is, the heavier the group 14 atom (E), the more stable its corresponding 7-Rea-E compound to chemical reaction. This study’s theoretical findings suggest that all of the seven-member 7-Rea-E should be readily synthesized and isolated at room temperature, since they are quite inert to chemical reaction, except for reaction with moisture. Furthermore, the group 14 7-Rea-E singlet-triplet energy splitting, as described in the configuration-mixing model of Pross and Shaik, can be used as a diagnostic tool to predict their reactivity. The results obtained allow a number of predictions to be made.
Part of the book: Chemical Reactions in Inorganic Chemistry
The effect of substitution on the potential energy surfaces of RE13 ☰ PR (E13 = B, Al, Ga, In, Tl; R = F, OH, H, CH3, SiH3, SiMe(SitBu3)2, SiiPrDis2, Tbt, and Ar* is studied using density functional theory (M06-2X/Def2-TZVP, B3PW91/Def2-TZVP and B3LYP/LANL2DZ + dp). The theoretical results demonstrate that all triply bonded RE13 ☰ PR compounds with small substituents are unstable and spontaneously rearrange to other doubly bonded isomers. That is, the smaller groups, such as R 〓 F, OH, H, CH3 and SiH3, neither kinetically nor thermodynamically stabilize the triply bonded RE13 ☰ PR compounds. However, the triply bonded R’E13☰PR´ molecules, possessing bulkier substituents (R´ = SiMe(SitBu3)2, SiiPrDis2, Tbt and Ar*), are found to have a global minimum on the singlet potential energy surface. In particular, the bonding character of the R’E13☰PR´ species is well defined by the valence-electron bonding model (model [II]). That is to say, R’E13☰PR´ molecules that feature groups are regarded as R′-E13P-R′. The theoretical evidence shows that both the electronic and the steric effects of bulkier substituent groups play a prominent role in rendering triply bonded R′E13☰PR′ species synthetically accessible and isolable in a stable form.
Part of the book: Phosphorus
The effect of substitution on the potential energy surfaces of RAl☰SbR (R = F, OH, H, CH3, SiH3, SiMe(SitBu3)2, SiiPrDis2, Tbt, and Ar*) is investigated using density functional theories (M06-2X/Def2-TZVP, B3PW91/Def2-TZVP, and B3LYP/LANL2DZ + dp). The theoretical results demonstrated that all the triply bonded RAl☰SbR compounds with small substituents are unstable and can spontaneously rearrange to other doubly bonded isomers. That is, the smaller groups, such as R = F, OH, H, CH3 and SiH3, neither kinetically nor thermodynamically stabilize the triply bonded RAl☰SbR compounds. However, the triply bonded R’Al☰SbR´ molecules that feature bulkier substituents (R´ = SiMe(SitBu3)2, SiiPrDis2, Tbt, and Ar*) are found to possess the global minimum on the singlet potential energy surface and are both kinetically and thermodynamically stable. In particular, the bonding characters of the R’Al☰SbR´ species agree well with the valence-electron bonding model (model) as well as several theoretical analyses (the natural bond orbital, the natural resonance theory, and the charge decomposition analysis). That is to say, R’Al☰SbR´ molecules that feature groups are regarded as R′─Al Sb─R′. Their theoretical evidence shows that both the electronic and the steric effects of bulkier substituent groups play a decisive role in making triply bonded R′Al☰SbR′ species synthetically accessible and isolable in a stable form.
Part of the book: Basic Concepts Viewed from Frontier in Inorganic Coordination Chemistry