Computational study of the bonding structure in ylide compounds

Liao, Hsin‐Yi; Yen, Mei-Yin

doi:10.1039/b715049k

Cited by 9 publications

(4 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Moreover, the value of the sum of the bond angles about silicon (∑Si α = 298.8°) is in agreement with a strongly pyramidalized center. However, the bond-angle sum about silicon is much larger than the computed value (∑Si α = 268°) for the parent molecule H 3 P−SiH 2 , probably for steric reasons. These structural features suggest a highly polarized P−Si ylidic bond with little or no PSi π character, in marked contrast to the carbon congener I , which features a shortened P−C bond (∼1.68 Å) compared with that in phosphonium salts (1.78−1.80 Å) and a nearly planar carbon center due to the P−C negative hyperconjugation .…”

mentioning

confidence: 95%

Stable Phosphonium Sila-ylide with Reactivity as a Sila-Wittig Reagent

et al. 2009

View full text Add to dashboard Cite

The silicon congeners of well-known phosphonium ylides have been considered only as short-lived reactive intermediates. We successfully synthesized a remarkably stable phosphonium sila-ylide. Its X-ray structure reveals a long Si-P bond and a strongly pyramidalized silicon center, indicating a very weak P-Si pi interaction. In addition, it exhibits an alpha,beta-ambiphilic character with a nucleophilic silicon center, similar to its carbon-congener phosphonium ylides. This property of the phosphonium sila-ylide allows its use as a sila-Wittig reagent with carbonyl derivatives.

show abstract

mentioning

confidence: 95%

Stable Phosphonium Sila-ylide with Reactivity as a Sila-Wittig Reagent

et al. 2009

View full text Add to dashboard Cite

show abstract

“…The Lewis acid–base complexation of transient silylenes and germylenes with chalcogen and pnictogen donors was first studied experimentally by low-temperature spectroscopic methods in the 1980s by West and Ando and their co-workers, following an early theoretical study of the complexation and X–H insertion reactions of SiH 2 with the parent hydride donors by Raghavachari and co-workers . A later computational study of the complexation of SiH 2 , GeH 2 , and SnH 2 with the chalcogen and pnictogen hydrides predicted the Lewis acidities of the species to decrease in the order Si > Ge > Sn and demonstrated the more pronounced ylide character of the complexes with the third-row donors in comparison to those with the corresponding second-row homologues; more sophisticated theoretical studies of the bonding in SiH 2 -phosphine ylides and comparisons to those in methylenephosphorane and other, related systems have been carried out more recently. Other theoretical studies have ranked a variety of substituted silylenes and germylenes according to their electrophilicities and hardness; the latter is based on calculated binding energies with NH 3 and PH 3 , the relative magnitudes of which have led to the general classification of simple silylenes and germylenes as “hard” electrophiles .…”

Section: Introductionmentioning

confidence: 99%

Electronic and Steric Effects on the Lewis Acidities of Transient Silylenes and Germylenes: Equilibrium Constants for Complexation with Chalcogen and Pnictogen Donors

2012

View full text Add to dashboard Cite

The Lewis acid−base complexation reactions of dimethyl-, diphenyl-, and dimesitylsilylene (SiMe 2 , SiPh 2 , and SiMes 2 , respectively) and their germanium homologues (GeMe 2 , GePh 2 , and GeMes 2 ) with diethyl ether (Et 2 O), tetrahydrothiophene (THT), triethylphosphine (Et 3 P), and tricyclohexylphosphine (Cy 3 P) have been characterized in hydrocarbon solvents at 25 °C by laser flash photolysis methods. Together with previously reported (and some new) data for the complexation of the six transient tetrellylenes with methanol (MeOH), tetrahydrofuran (THF), and di-and triethylamine (Et 2 NH and Et 3 N, respectively), the results allow the first systematic assessment of the thermodynamics of Lewis acid−base complexation of simple dialkyl-and diarylsilylenes and their germanium homologues with chalcogen and pnictogen donors in solution. The equilibrium constants (K C ) for complexation of the six species with Et 2 O span a range of ca. 10 5 M −1 , decreasing in the order SiPh 2 > SiMe 2 > GePh 2 > GeMe 2 ≫ SiMes 2 > GeMes 2 . For each homologous MR 2 pair, K C is consistently 10−40 times larger for the silylene than the germylene, indicating a systematic difference in binding free energy of 1.5−2.2 kcal mol −1 . Equilibrium constants have been determined for complexation of SiMes 2 and GeMes 2 with all the donors in the series except Et 3 P, for which only a lower limit can be determined. Those for SiMes 2 decrease in the order Et 3 P > Cy 3 P > Et 2 NH > THT > Et 3 N > THF > Et 2 O; GeMes 2 is consistently less acidic, but its binding constants follow a similar ordering. The experimental data are supplemented with theoretical (Gaussian-4) calculations of thermochemical parameters for the complexation of SiMe 2 and GeMe 2 with 17 O, S, N, and P donors, which are shown to agree with experiment to within 1 kcal mol −1 for the 6 systems that have also been studied experimentally. The calculations confirm that, in general, trialkylphosphines bind most strongly, followed by amines, sulfides, and then ethers and alcohols. SiMe 2 and GeMe 2 are borderline-soft Lewis acids, stronger and softer than trimethylborane in both cases.

show abstract

“…The HOMO-LUMO gap is also generally considered to be a wonderful parameter in the analysis of cluster chemical reactivity. [27][28][29][30] In general, the energy gap between HOMO and LUMO reflects the relative chemical stability of clusters and represents the ability for the molecular participating to produce chemical reactions to some degree. Therefore, the systems with larger HOMO-LUMO energy gap have higher chemical stability.…”

Section: Electronic Structurementioning

confidence: 99%

Stability, Infrared Spectra and Electronic Structures of (ZrO₂)_n(n=3–6) Clusters: DFT Study

et al. 2011

View full text Add to dashboard Cite

The stability, infrared spectra and electronic structures of (ZrO 2 ) n (n＝3-6) clusters have been investigated by using density-functional theory (DFT) at B3LYP/6-31G* level. The lowest-energy structures have been recognized by considering a number of structural isomers for each cluster size. It is found that the lowest-energy (ZrO 2 ) 5 cluster is the most stable among the (ZrO 2 ) n (n＝3-6) clusters. The vibration spectra of Zr-O stretching motion from terminal oxygen atom locate between 900 and 1000 cm −1 , and the vibrational band of Zr-O-Zr-O four member ring is obtained at 600-700 cm -1 , which are in good agreement with the experimental results. Mulliken populations and NBO charges of (ZrO 2 ) n clusters indicate that the charge transfers occur between 4d orbital of Zr atoms and 2p orbital of O atoms. HOMO-LUMO gaps illustrate that chemical stabilities of the lowest-energy (ZrO 2 ) n (n＝ 3-6) clusters display an even-odd alternating pattern with increasing cluster size.

show abstract

Computational study of the bonding structure in ylide compounds

Cited by 9 publications

References 31 publications

Stable Phosphonium Sila-ylide with Reactivity as a Sila-Wittig Reagent

Stable Phosphonium Sila-ylide with Reactivity as a Sila-Wittig Reagent

Electronic and Steric Effects on the Lewis Acidities of Transient Silylenes and Germylenes: Equilibrium Constants for Complexation with Chalcogen and Pnictogen Donors

Stability, Infrared Spectra and Electronic Structures of (ZrO₂)_n(n=3–6) Clusters: DFT Study

Contact Info

Product

Resources

About

Computational study of the bonding structure in ylide compounds

Cited by 9 publications

References 31 publications

Stable Phosphonium Sila-ylide with Reactivity as a Sila-Wittig Reagent

Stable Phosphonium Sila-ylide with Reactivity as a Sila-Wittig Reagent

Electronic and Steric Effects on the Lewis Acidities of Transient Silylenes and Germylenes: Equilibrium Constants for Complexation with Chalcogen and Pnictogen Donors

Stability, Infrared Spectra and Electronic Structures of (ZrO2)n(n=3–6) Clusters: DFT Study

Contact Info

Product

Resources

About

Stability, Infrared Spectra and Electronic Structures of (ZrO₂)_n(n=3–6) Clusters: DFT Study