The boron–boron triple bond? A thermodynamic and force field based interpretation of the N-heterocyclic carbene (NHC) stabilization procedure

From thermodynamic and force constant discussion a new description of bonding of B2(NHC)2 (NHC = N-heterocyclic carbene C3N2H2(C6H3Pri2-2,6)2) as NHCBBNHC rather than NHC→BB←NHC is given.

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Symmetry Coordinates and Tentative Force Field Analysis of a PMo12O40 Model with the Keggin Structure

Zeitschrift für Naturforschung A ◽

10.1515/zna-1976-1221 ◽

1976 ◽

Vol 31 (12) ◽

pp. 1589-1600 ◽

Cited By ~ 2

Author(s):

Lennart Lyhamn ◽

S. J. Cyvin ◽

B. N. Cyvin ◽

J. Brunvoll

Keyword(s):

Experimental Data ◽

Force Field ◽

Force Constant ◽

Raman Spectra ◽

Vibrational Analysis ◽

Field Analysis ◽

Infrared And Raman Spectra ◽

Symmetry Coordinates ◽

Force Field Analysis ◽

Complex Ion

Abstract A complete vibrational analysis is performed for the 53 atomic PMo12O40 model of Td symmetry. The symmetry coordinates are classified into those of (a) ligand vibrations, (b) framework-ligand couplings, (c) framework vibrations, and (d) interligand vibrations. Simple valence force fields are estimated, and the influence of inclusion of redundancies on the calculated frequencies and symmetry force constants is investigated. Comments are made on calculated symmetry force constant values up to 345 mdyne/Å. Vibrational frequencies are calculated for the Mo3O7 and Mo3O13 units and for the PMo12O403- complex ion. For the latter compound the calculated values are compared with experimental data from infrared and Raman spectra.

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Molecular force field for chlorine trifluoride

Australian Journal of Chemistry ◽

10.1071/ch9650261 ◽

1965 ◽

Vol 18 (3) ◽

pp. 261 ◽

Cited By ~ 2

Author(s):

MG Krishna ◽

K Ramaswamy ◽

R Pichai

Keyword(s):

Force Field ◽

Force Constant ◽

Lone Pair ◽

Pair Interaction ◽

Pair Bond ◽

Approximate Relation ◽

Lone Pairs ◽

Bond Pair ◽

Molecular Force ◽

Molecular Force Field

An attempt has been made to modify the UBFF for chlorine trifluoride by taking into account the presence of lone pairs of electrons, on the lines suggested by Pariseau, Wu, and Overend. It was found that the lone-pair-bond-pair interaction is less than the lone-pair-lone-pair interaction which is considerably lower than the stretching force constant for the lone pair of electrons. An approximate relation between the above interactions was obtained.

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Comments on the paper by A. D. Walsh

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1951.0095 ◽

1951 ◽

Vol 207 (1088) ◽

pp. 30-31 ◽

Cited By ~ 1

Keyword(s):

Carbon Atom ◽

Force Constant ◽

Triple Bond ◽

The Other ◽

Carbon Nucleus ◽

Nucleus Plus ◽

The Difference ◽

Effective Attraction

I agree very much with Dr Walsh that a satisfactory knowledge of effective atomic electronegativities is very important and that we should concentrate on obtaining such knowledge. The effective electronegativity of an atom varies, of course, in different circumstances. This appears to be the explanation of the difference in strength (length and force constant) of the C—H bonds in methane and acetylene. The effective attraction of the carbon atom for the electrons in a C—H bond in methane is a resultant of the attraction of the carbon nucleus plus Is core and the repulsion of the electrons associated with the other three C—H bonds. In acetylene the effective attraction of the carbon atom for the electrons in the C—H bond is the resultant of the attraction of the nucleus plus core and the repulsion of the electrons in the triple bond. Because these last six electrons are drawn away into the triple bond on the far side of the carbon atom from the C—H bond it seems that their repulsion on the electrons in the C—H bond is less than that of the six electrons in the three other C—H bonds in methane which are relatively nearer.

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Normal Coordinate Analysis of Some Hexahalide Anions of IV Group Elements

Zeitschrift für Naturforschung A ◽

10.1515/zna-1971-0707 ◽

1971 ◽

Vol 26 (7) ◽

pp. 1137-1139 ◽

Cited By ~ 4

Author(s):

M. N. Avasthi ◽

M. L. Mehta

Keyword(s):

Force Field ◽

Force Constant ◽

Normal Coordinate Analysis ◽

Oxidation Number ◽

Normal Coordinate ◽

Valence Force ◽

Valence Force Field ◽

Isoelectronic Series ◽

Titanium Zirconium

Abstract The normal coordinate analysis has been applied to the hexachloride and hexabromide of tin, titanium, zirconium and hafnium, using the Urey-Bradley force field (UBFF) and orbital valence force field (OVFF). It is observed that the stretching force constant increases as the oxidation number of the metal increases within isoelectronic series.

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Force Field Study of Some Hexahalide Anions of Transition Metals

Zeitschrift für Naturforschung A ◽

10.1515/zna-1971-0706 ◽

1971 ◽

Vol 26 (7) ◽

pp. 1134-1136

Author(s):

M. N. Avasthi ◽

M. L . Mehta

Keyword(s):

Transition Metals ◽

Force Field ◽

Field Study ◽

Force Constant ◽

Approximation Method ◽

Matrix Approximation ◽

Oxidation Number ◽

Mean Amplitudes Of Vibration ◽

Valence Force Field ◽

The Mean

AbstractUsing the L matrix approximation method of Müller the seven independent force constants for the hexahalide anions of zirconium and hafnium metals have been evaluated employing general valence force field (GVFF). The stretching force constant increases as the oxidation number of the metal increases. The mean amplitudes of vibration have been calculated using the L matrix approximation method. The trends of mean amplitudes of vibration have also been discussed.

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MOLECULAR FORCE FIELD FOR SULFUR TETRAFLUORIDE

Canadian Journal of Chemistry ◽

10.1139/v65-062 ◽

1965 ◽

Vol 43 (2) ◽

pp. 463-469 ◽

Cited By ~ 7

Author(s):

M. G. Krishna Pillai ◽

K. Ramaswamy ◽

R. Pichai

Keyword(s):

Force Field ◽

Bond Length ◽

Force Constant ◽

Lone Pair ◽

Bond Pair ◽

Molecular Force ◽

Axial Stretching ◽

Sulfur Tetrafluoride ◽

The Relationship ◽

Lone Pair Interactions

An attempt has been made to modify the UBFF for SF4 by taking into account the presence of the lone pair of electrons. It has been found that the bond pair – lone pair interactions become of importance only when the angle between the bond pair and the lone pair approaches 90°. The equatorial S—F stretching force constant (4.0146 mdyn/Å) is greater than the axial stretching force constant (3.6237 mdyn/Å), which is consistent with the form of the relationship between the force constant and bond length.

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