The structure of 1-chlorosilatrane

An ab initio molecular orbital and a density functional theory study

G. Csonka, Pál Hencsei

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

The molecular geometries of the 1-chloro-, 1-fluoro-, 1-methyl-, and 1-hydrogenosilatranes were fully optimized by the restricted Hartree-Fock (HF) method supplemented with 3-21G, 3-21G(d), 6-31 G(d), and CEP-31G(d) basis sets; by MP2 calculations using 6-31G(d) and CEP-31G(d) basis sets; and by GGA-DFT calculations using 6-31G(d5) basis set with the aim of locating the positions of the local minima on the energy hypersurface. The HF/6-31G(d) calculations predict long (> 254 pm) and the MP2/CEP calculations predicted short ( ∼ 225 pm) equilibrium Si - N distances. The present GGA-DFT calculations reproduce the available gas phase experimental Si - N distances correctly. The solid phase experimental results predict that the Si - N distance is shorter in 1-chlorosilatrane than in 1-fluorosilatrane. In this respect the HF results show a strong basis set dependence, the MP2/CEP results contradict the experiment, and the GGA-DFT results in electrolytic medium agree with the experiment. The latter calculations predict that 1-chlorosilatrane is more polarizable than 1-fluorosilatrane and also support a general Si - N distance shortening trend for silatranes during the transition from gas phase to polar liquid or solid phase. The calculations predict that the ethoxy links of the silatrane skeleton are flexible. Consequently, it is difficult to measure experimentally the related bond lengths and bond and torsion angles. This is the probable origin of the surprisingly large differences for the experimental structural parameters. On the basis of experimental analogies, ab initio calculations, and density functional theory (DFT) calculations, a gas phase equilibrium (re) geometry is predicted for 1-chlorosilatrane. The semiempirical methods predict a so-called exo minimum (at above 310 pm Si - N distance); however, the ab initio and GGA-DFT calculations suggest that this form is nonexistent. The GGA-DFT geometry optima were characterized by frequency analysis.

Original languageEnglish
Pages (from-to)767-780
Number of pages14
JournalJournal of Computational Chemistry
Volume17
Issue number7
Publication statusPublished - May 1996

Fingerprint

Molecular orbitals
Density Functional
Density functional theory
p.m.
Predict
Gases
Geometry
Ab Initio Calculations
Phase Equilibria
Frequency Analysis
Structural Parameters
Probable
Skeleton
Local Minima
Bond length
Torsion
Hypersurface
Experiment
Analogy
Phase equilibria

ASJC Scopus subject areas

  • Chemistry(all)
  • Safety, Risk, Reliability and Quality

Cite this

The structure of 1-chlorosilatrane : An ab initio molecular orbital and a density functional theory study. / Csonka, G.; Hencsei, Pál.

In: Journal of Computational Chemistry, Vol. 17, No. 7, 05.1996, p. 767-780.

Research output: Contribution to journalArticle

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