A theoretical study of the bond-bond interaction force constant in XF2 molecules

1969 ◽  
Vol 14 (3) ◽  
pp. 232-241 ◽  
Author(s):  
Roy Bruns ◽  
Lionel Raff ◽  
J. Paul Devlin
Keyword(s):  
Force Constant ◽  
Theoretical Study ◽  
Interaction Force ◽  
Bond Interaction

Molecular Orbitals and CH3, CH2, and CH Deformation Group Frequencies

1980 ◽  
Vol 34 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Norman B. Colthup
Keyword(s):  
Linear Relationship ◽  
Electron Density ◽  
Force Constant ◽  
Molecular Orbital ◽  
Interaction Force ◽  
Molecular Orbitals ◽  
Deformation Vibration ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Symmetrical Deformation

A linear relationship has been found between the wavenumber of the CH3 symmetrical deformation vibration and the electron density on the CH3 carbon as calculated from CNDO/2 molecular orbital theory. Other CH deformation vibrations are also related to the electron density on the carbon and, as a result, can be correlated with the CH3 symmetrical deformation wavenumber. These include ν̄(CH2 def), ν̄(CH2 wag) and both components of ν̄(CH wag). The splitting of ν̄(CH3 sym def) in isopropyl and t-butyl groups has long been known. It is shown here that the effect is due to an interaction force constant relating to the CH3 symmetrical deformation vibrations of two or three different neighboring CH3 groups. The origin of the interaction is thought to be an H,H′ repulsion between hydrogens on the different CH3 groups.

Zur Stereochemie von Diazadien-Metall-Komplexen, V. Molekülstrukturen und CO-Kraftkonstanten nicht-starrer Chrom-, Molybdänund Wolframcarbonylderivate DAD M(CO)3(*CO) (*C0 = 12CO, 13CO, C180)/ Stereochemistry of Diazadiene Metal Complexes, V Molecular Structures and CO Force Constants of Non-Rigid Chromium, Molybdenum and Tungsten Carbonyl Derivatives DAD M(CO)3(*CO) (*CO = 12CO, 13CO, C18O)

1983 ◽  
Vol 38 (5) ◽  
pp. 568-579 ◽  
Author(s):  
Heindirk tom Dieck ◽  
Thomas Mack ◽  
Karl Peters ◽  
Hans-Georg von Schnering
Keyword(s):  
Force Constant ◽  
Good Accuracy ◽  
Interaction Force ◽  
Force Constants ◽  
Molecular Structures ◽  
X Ray ◽  
Carbonyl Derivatives ◽  
Donor Acceptor ◽  
Site Exchange ◽  
Ray Methods

AbstractDiazadiene metal tetracarbonyls, DAD M(CO)4, (M = Cr, Mo, W; DAD = R-N = CH-CH = NR with aliphatic and aromatic substituents R) show equidistribution of one labelled CO when synthesized from fac-DAD M(CO)3(CH3CN) as a consequence of intramolecular CO site exchange. The structures of two Mo-complexes (1: R = iso-propyl; 2: R = 2,6-diisopropylphenyl) with DAD's of different bulkiness have been solved by X-ray methods. From the infrared solution spectra, including those of isotopically labelled (13CO, C18O) compounds, all of the force constants k1, k2, ktt, kcc and kcc have been calculated independently. The ratios of interaction force constants deviate sharply from Cotton-Kraihanzel assumptions, perhaps because of the substantial deviation of the iraws-pair of CO groups from linearity (1: 154.5°, 2: 147.9°). The solid state N-Mo, Mo-C and C - O bond lengths are neither in agreement with the generally accepted picture for donor/acceptor influences nor with typical IR data and force constant interpretations. (2 with higher v(CO) and k1, k2 has the longer CO bonds and shorter Mo-C bonds than 1.) The force constant sets have been used to calculate CO frequencies for over 60 labelled compounds with good accuracy (Δv < 2 cm-1).

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