A synthetic and computational study of fluorinated isocyanides

Thesis/Dissertation · Thu Dec 31 23:00:00 EST 1992

OSTI ID:7207399

Madappat, K V

Pentafluorosulfanyl isocyanide SF[sub 5]NC was prepared from pentafluorosulfanyl isocyanide dibromide SF[sub 5]NCBr[sub 2] using reagents such as magnesium, lithium alkyls, and samarium diiodide. The compound was obtained only in low yield. The new isocyanide is a colorless gas which has been characterized by its infrared, [sup 19]F NMR, and mass spectra as well as by a vapor density molecular weight determination. In the gas phase SF[sub 5]NC was found to isomerize to the cyanide SF[sub 5]CN even at room temperature. The kinetics of the isomerization of SF[sub 5]NC to SF[sub 5]CN were studied using Fourier transform infrared spectroscopy. The kinetics are best fit by a combination of first and second order rate laws. The experimental activation barrier was determined to be approximately 40 kJ/mole. Pentafluorosulfanyl isocyanide and its isomers were also studied by ab initio molecular orbital methods at the Hartree-Fock and MP2 levels using the 6-13G[sub *] basis set. The calculated energies for the isomerization of SF[sub 5]NC are comparable to the known isomerization energies of the organic isocyanides. There is no agreement between the experimental and calculated activation energies as the calculated values is approximately 200 kJ/mole. The normal-mode vibrational frequencies of SF[sub 5]NC and SF[sub 5]CN calculated at the MP2/6-31G[sup *] level are in excellent agreement with the experimental frequencies when appropriate scaling methods are employed. The calculations also indicate that SF[sub 5]NC should be a strong [pi]-acceptor ligand in metal complexes. Fluorinated methyl and vinyl isocyanides and cyanides were studied by computational methods. The calculations indicate that the [pi]-acceptor strength of the fluorinated methyl isocyanides should be enhanced with increasing degree of fluorination. A computational study of CF[sub 3]NHC(O)H represents another example of excellent agreement between theory and experiment.

• Research Organization: Alabama Univ., Birmingham, AL (United States)
• OSTI ID: 7207399
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ACTIVATION ENERGY
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL PROPERTIES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CYANIDES
ENERGY
FLUORINE COMPOUNDS
HALOGEN COMPOUNDS
ISOMERIZATION
KINETICS
REACTION KINETICS
STEREOCHEMISTRY
STRUCTURAL CHEMICAL ANALYSIS
SULFIDES
SULFUR COMPOUNDS
SYNTHESIS