Molecular mechanics calculations (MM2) on organometallanes of germanium, tin, and lead

Allinger, Norman L.; Quinn, Maritza I.; Chen, Kuohsiang; Thompson, B. Blackburn; Frierson, Manton R.

doi:10.1016/0022-2860(89)80066-3

Cited by 17 publications

(3 citation statements)

References 35 publications

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“…Steric hindrance for Sn complexes grafted on the metallic surface was calculated by using SYBYL molecular modeling software from TRIPOS and Silicon Graphics Indigo as hardware. We used the classical TRIPOS force field data for H and C. Bond distances, angles, and constants not found in the TRIPOS force field were based on the literature values …”

Section: Methodsmentioning

confidence: 99%

Surface Organometallic Chemistry on Metals: Formation of a Stable ⋮Sn(n-C₄H₉) Fragment as a Precursor of Surface Alloy Obtained by Stepwise Hydrogenolysis of Sn(n-C₄H₉)₄ on a Platinum Particle Supported on Silica

et al. 1998

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Selective hydrogenolysis of Sn(n-C4H9)4 on a Pt/SiO2 catalyst has been carried out at various temperatures and coverages of the metallic surface to prepare via surface organometallic chemistry a well-defined class of bimetallic catalysts. The stoichiometry and kinetics of the reaction was followed by the careful analysis of reagents and products, including extraction of unreacted reagents, and elemental analysis of the samples. The various surface species formed were characterized by electron microscopy (CTEM and TEM EDAX) and EXAFS analysis. Possible structures of the surface organometallic fragments were considered using molecular modeling. At 50 °C, the hydrogenolysis reaction occurs selectively on the platinum surface with exclusive evolution of n-butane. There is first formation of a Sn(n-C4H9)3 fragment grafted on the platinum particle which undergoes a stepwise cleavage of two tin−carbon σ-bonds to form a stable Pt−Sn(n-C4H9) fragment. Regardless of the reaction time, surface coverage, or loading, the number of grafted butyl fragments per platinum is never greater than unity, that is to say that when Sn(n-C4H9)3 is formed the platinum coverage by tin is 0.3 whereas when Sn(n-C4H9) is formed the platinum coverage is closer to 1. It is therefore suggested that the surface composition is governed by the bulkiness of the alkyl chains which are “close packed” on the surface. At 100 °C, the reaction takes place both on the platinum and the silica surface. On the platinum surface, the same fragments (namely Sn(n-C4H9)3, Sn(n-C4H9)2, and Sn(n-C4H9)) were identified, but simultaneously on the silica surface, the well-described ⋮SiOSn(n-C4H9)3 species was also formed. Thermal treatment under hydrogen of Pts−Sn(n-C4H9) lead to alkyl-free tin atoms which are located at the periphery of the particle as evidenced by Sn K edge EXAFS (Pt−Sn distance of 2.75 Å with a coordination number of ca. 4). Even if the organotin fragments are grafted with a coverage of unity, after their complete hydrogenolysis at 300 °C, about 40% of the platinum is still accessible to H2 chemisorption. This could be explained by the increase of the particle diameter (+0.5 Å) which prevents a close packing of the tin atoms around the particle and leaves some platinum atoms still accessible to the hydrogen. After treatment of the catalyst at higher temperatures, typically 500 °C, the structure of the catalyst is slightly changed since the tin atoms migrate into the first monolayer of the particle, as evidenced by a significant increase of the tin coordination number (ca. 4.4−5.6) as determined by EXAFS. Hypothetical surface structures have been proposed on the basis of molecular modeling of platinum particles covered by various surface organotin fragments.

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Section: Methodsmentioning

confidence: 99%

Surface Organometallic Chemistry on Metals: Formation of a Stable ⋮Sn(n-C₄H₉) Fragment as a Precursor of Surface Alloy Obtained by Stepwise Hydrogenolysis of Sn(n-C₄H₉)₄ on a Platinum Particle Supported on Silica

et al. 1998

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“…1 A previous MM2 study on Group IV organometallanes (germanium, tin, and lead) has been published. 2 However, early versions of MM2 gave some minor errors, which were later corrected. Nevertheless, there still appear to be some significant systematic errors, and it would require substantial efforts to fix them.…”

Section: Introductionmentioning

confidence: 98%

Molecular mechanics (MM3) study of organogermanes

Chen

Allinger

1999

J. Phys. Org. Chem.

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“…One of the reasons for this is that the great variety of oxidation states and coordination geometries available precludes the existence of a truly universal set of parameters. Force fields must therefore either have a large number of situation-specific atom types, − or define sets of rules that quickly identify the type of structure and the corresponding set of parameters. , The number of parameters available for main-group elements is rather small and those available apply only to strongly covalent bonds between atoms; SBIs are simply neglected within molecular mechanics.…”

Section: Introductionmentioning

confidence: 99%

Parametrization of a Force Field for Te−N Secondary Bonding Interactions and Its Application in the Design of Supramolecular Structures Based on Heterocyclic Building Blocks

Cozzolino

Vargas‐Baca

2011

Crystal Growth & Design

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1,2,5-Telluradiazole rings have a remarkably strong tendency toward association through Te-N secondary bonding interactions in the solid state. The reproducibility of the bond lengths and angles in the known crystal structures allowed the parametrization of an anharmonic force field to accommodate both the inter-and intramolecular Te-N bonds. The new parameters were tested against published crystal structures and were able to accurately reproduce the experimentally observed geometries. The incorporation of these parameters into a molecular mechanics force field enables the modeling of large and complex structures with significantly less computational effort than Hartree-Fock (HF) or density functional theory (DFT) methods. Simple modifications to the parameter set allowed the modeling of the structures of acyclic tellurium diamides. A series of 4,7-disubstituted benzo-2,1,3-telluradiazoles were modeled to probe the steric barrier of dimerization; only the groups with large spherical bulks such as t-butyl, trimethylsilyl, and adamantyl were able to destabilize the dimers. Modeling based on bifunctional building blocks suggests strategies for the construction of novel two-and three-dimensional supramolecular architectures.

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Molecular mechanics calculations (MM2) on organometallanes of germanium, tin, and lead

Cited by 17 publications

References 35 publications

Surface Organometallic Chemistry on Metals: Formation of a Stable ⋮Sn(n-C₄H₉) Fragment as a Precursor of Surface Alloy Obtained by Stepwise Hydrogenolysis of Sn(n-C₄H₉)₄ on a Platinum Particle Supported on Silica

Surface Organometallic Chemistry on Metals: Formation of a Stable ⋮Sn(n-C₄H₉) Fragment as a Precursor of Surface Alloy Obtained by Stepwise Hydrogenolysis of Sn(n-C₄H₉)₄ on a Platinum Particle Supported on Silica

Molecular mechanics (MM3) study of organogermanes

Parametrization of a Force Field for Te−N Secondary Bonding Interactions and Its Application in the Design of Supramolecular Structures Based on Heterocyclic Building Blocks

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Molecular mechanics calculations (MM2) on organometallanes of germanium, tin, and lead

Cited by 17 publications

References 35 publications

Surface Organometallic Chemistry on Metals: Formation of a Stable ⋮Sn(n-C4H9) Fragment as a Precursor of Surface Alloy Obtained by Stepwise Hydrogenolysis of Sn(n-C4H9)4 on a Platinum Particle Supported on Silica

Surface Organometallic Chemistry on Metals: Formation of a Stable ⋮Sn(n-C4H9) Fragment as a Precursor of Surface Alloy Obtained by Stepwise Hydrogenolysis of Sn(n-C4H9)4 on a Platinum Particle Supported on Silica

Molecular mechanics (MM3) study of organogermanes

Parametrization of a Force Field for Te−N Secondary Bonding Interactions and Its Application in the Design of Supramolecular Structures Based on Heterocyclic Building Blocks

Contact Info

Product

Resources

About

Surface Organometallic Chemistry on Metals: Formation of a Stable ⋮Sn(n-C₄H₉) Fragment as a Precursor of Surface Alloy Obtained by Stepwise Hydrogenolysis of Sn(n-C₄H₉)₄ on a Platinum Particle Supported on Silica

Surface Organometallic Chemistry on Metals: Formation of a Stable ⋮Sn(n-C₄H₉) Fragment as a Precursor of Surface Alloy Obtained by Stepwise Hydrogenolysis of Sn(n-C₄H₉)₄ on a Platinum Particle Supported on Silica