Bent Bonds Research Articles

Interpretation of bond-length data for transition-metal–acetylene complexes, in particular the complex [C5H5NH][TaCl4(PhCCPh)(NC5H5)

By analogy with cyclopropene, a simple metallocene model for transition-metal–acetylene complexes should be described as containing bent bonds. On the basis of this model, a simple method for predicting metal–carbon and carbon–carbon distances is proposed and its application to [C5H5NH][TaCl4(PhCCPh)(NC5H5)] is described in detail. It is concluded that the reported structural data for this compound are fully consistent with those expected for a simple bent-bond model, and that there is no compulsion on the basis of bond-length data to invoke a contribution to bonding from four-electron donation from the acetylene to the metal, as was previously proposed.

Are bonds bent? To what extent do bond orbitals follow nuclear motions?

In order to make definitive statements about bent bonds and orbital following accurate ab initio self-consistent valence bond orbitals have been obtained for CH/sub 4/, NH/sub 3/, H/sub 2/O, and H/sub 2/S as a function of nuclear geometry. The directions of the orbitals are uniquely determined by the energy minimization criterion. It is found that the bonding orbitals on the central atoms are normally bent a small amount at equilibrium unless constrained to be otherwise by symmetry. More striking is the fact that in almost all cases these orbitals remain nearly stationary as the nuclei undergo bending motions about equilibrium. At the same time there are changes in hybridization which occur in a direction in accord with chemical intuition. Localized molecular orbital calculations were also carried out for comparison purposes. They lead to the same qualitative conclusion that, in general, orbital stasis is a much better approximation than complete orbital following.

Electron—density maps of bent bonds in non-cyclic molecules

Much structural evidence supports the crude notion that a chemical bond behaves much like a flexible spring and is readily bent by unbalanced 1 … 3 steric repulsions. Electron-density maps, derived experimentally (X-ray diffraction) or theoretically (extended-basis SCF calculations), show that such bending is expressed in a deformation-density peak slightly displaced off the bond axis. This is demonstrated in 2-cyanoguanidine, hydrazoic acid, cyanogen azide, formic acid, and diimide. Besides accounting for tilted methyl groups, as in methanol, and numerous similar violations of local symmetry, the flexible—spring model rationalizes a variety of conformational effects, such as the preferred syn-planar conformation of carboxylio acids, where the axis of internal rotation does not coincide with the internuclear vector.

Electron-density maps of bent bonds in non-cyclic molecules

Electron-density maps of bent bonds in non-cyclic molecules

X-Ray and neutron diffraction study of 1,1,1,2,2,2,3,3,3-nonacarbonyl-1,2;1,3-di-µ-hydrido-µ3-sulphido-triangulo-triosmium

The title complex [Os3(CO)9H2(S)] crystallises in the monoclinic space group C2/c with a= 20.476(10), b= 13.952(7), c= 12.939(6)A, β= 123.84(3)°, and Z= 8. Simultaneous refinement of a single parameter set to 2 436 X-ray [(sinθ)/λ > 0.45] and 1 292 neutron data has led to R 0.038 (X-ray) and 0.037 (neutron). The two longer edges of the Os3 isosceles triangle are bridged by hydrides, which lie on the opposite side of the Os3 plane to the triply bridging sulphur atom. Each osmium is also bonded to three terminal carbonyls. The Os–H–Os linkages can be described as ‘open’ three-centre two-electron bent bonds, with little direct Os–Os interaction. Both hydride bridges are significantly asymmetric, the hydrogen atoms being ca. 0.025 A closer to the unique osmium. The mean Os–H distance is 1.819 A, and both Os–H–Os angles are 106.5(2)°.

ChemInform Abstract: THE CHEMISTRY OF BENT BONDS. 51. THE RELATION OF POLARIZATION IN METAL‐CARBENE COMPLEXES TO THE DEGENERATE METATHESIS OF TERMINAL OLEFINS

Chemischer InformationsdienstVolume 8, Issue 15 Organoelement Compounds ChemInform Abstract: THE CHEMISTRY OF BENT BONDS. 51. THE RELATION OF POLARIZATION IN METAL-CARBENE COMPLEXES TO THE DEGENERATE METATHESIS OF TERMINAL OLEFINS P. G. GASSMAN, Search for more papers by this authorT. H. JOHNSON, Search for more papers by this author P. G. GASSMAN, Search for more papers by this authorT. H. JOHNSON, Search for more papers by this author First published: April 12, 1977 https://doi.org/10.1002/chin.197715284Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume8, Issue15April 12, 1977 RelatedInformation

The chemistry of bent bonds. 51. The relation of polarization in metal-carbene complexes to the degenerate metathesis of terminal olefins

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe chemistry of bent bonds. 51. The relation of polarization in metal-carbene complexes to the degenerate metathesis of terminal olefinsPaul G. Gassman and Thomas H. JohnsonCite this: J. Am. Chem. Soc. 1977, 99, 2, 622–623Publication Date (Print):January 1, 1977Publication History Published online1 May 2002Published inissue 1 January 1977https://doi.org/10.1021/ja00444a058RIGHTS & PERMISSIONSArticle Views66Altmetric-Citations12LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (271 KB) Get e-Alerts Get e-Alerts

ChemInform Abstract: CNDO 2 DIFFERENCE ELECTRON DENSITY CONTOURS IN SATURATED THREE‐MEMBERED RINGS

Theoretical difference electron density contours in the NCC, CCC, and OCC ring planes of ethyleneimine quinone, cis-1,2,3-tricyanocyclopropane and tetracyanoethylene oxide molecules, respectively, were calculated by the CNDO/2 molecular orbital method. They are qualitatively in good agreement with the experimental contours, and have reproduced the most characteristic features of the observed electron distributions in the bent bonds in the three-membered rings. The theoretical difference contours in the three-membered ring planes of aziridine, cyclopropane and oxirane molecules have shown essentially the same bonding electron distributions as the corresponding contours in the more complex molecules mentioned above.

CNDO/2 Difference Electron Density Contours in Saturated Three-membered Rings

Abstract Theoretical difference electron density contours in the NCC, CCC, and OCC ring planes of ethyleneimine quinone, cis-1,2,3-tricyanocyclopropane and tetracyanoethylene oxide molecules, respectively, were calculated by the CNDO/2 molecular orbital method. They are qualitatively in good agreement with the experimental contours, and have reproduced the most characteristic features of the observed electron distributions in the bent bonds in the three-membered rings. The theoretical difference contours in the three-membered ring planes of aziridine, cyclopropane and oxirane molecules have shown essentially the same bonding electron distributions as the corresponding contours in the more complex molecules mentioned above.

Chemistry of bent bonds. XLV. Norbornyne

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChemistry of bent bonds. XLV. NorbornynePaul G. Gassman and Joseph J. ValchoCite this: J. Am. Chem. Soc. 1975, 97, 16, 4768–4770Publication Date (Print):August 1, 1975Publication History Published online1 May 2002Published inissue 1 August 1975https://doi.org/10.1021/ja00849a056RIGHTS & PERMISSIONSArticle Views127Altmetric-Citations16LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (369 KB) Get e-Alerts Get e-Alerts

The chemistry of bent bonds : XLIV. Chemical evidence for the structure of the adduct obtained from quadricyclane and di-μ-chlorotetracarbonyldirhodium(I)

The structure of the adduct obtained from the reaction of tetracyclo [3.2.0.0 2,70 4,6] heptane (quadrdicyclane with di-gm-chlorotetracarbonyldirhodium(I) has been established on the basis of chemical evidence. The structure proposed by Cassar and Halpern was confirmed on the basis of the tricyclic alcohol isolated from the lithium aluminum deuteride reduction of the initially formed rhodium containing adduct.

The Electronic Structure and Localized Molecular Orbitals in S4N4 by the CNDO/BW Theory

The energies calculated for tetranitrogen tetrasulfide, S4N4, by the CNDO/BW theory favor a structure with coplanar nitrogen atoms and not a structure with coplanar sulfur atoms. Both structures have been proposed from experimental studies. Localized molecular orbitals are calculated for S4N4 and used to choose the appropriate Lewis structure for the molecule. The hybridization at the nitrogen and sulfur atoms is discussed. There is electron delocalization in the molecule, the S—N bond is a bent bond involving pure p-orbitals on the sulfur and nitrogen atoms and there is a pure p-bent bond between the sulfur atoms on the same side of the coplanar nitrogen atoms. There is no N—N bond in S4N4.

Chemistry of bent bonds. XLIV. Conformationally controlled solvolysis. Ion conformation as the determining factor in the ring expansion of bicyclo[2.1.0]pentane derivatives

Chemistry of bent bonds. XLIV. Conformationally controlled solvolysis. Ion conformation as the determining factor in the ring expansion of bicyclo[2.1.0]pentane derivatives

Chemistry of bent bonds. XLIII. Cycloadditions to cyclic 1,3-dienes. Diels-Alder route to inside-outside bicyclics

Chemistry of bent bonds. XLIII. Cycloadditions to cyclic 1,3-dienes. Diels-Alder route to inside-outside bicyclics

ChemInform Abstract: THE INTERMOLECULAR FORCE FIELD OF THE HYDROGEN BOND

Abstract A detailed examination has been made of the force field of the 24 hydrogenbonded complexes 4X-phenol/4Y-pyridine where X = F, Cl, Br, I, H or Me and Y = H, Me, Et or Ph. Referring to a harmonic force field, the following conclusions result: (1) An intermolecular hydrogen bond stretching force constant σ is obtained, which is independent of uncertainties in the phenol and pyridine internal force fields or the relative orientation of these moieties. (2) These values of ƒ σ are linearly related to the p K a of the phenol, or Δ v s , through the series with common base. (3) The OH stretching mode v s is well localised, and thus Δ v s is a good measure of the strength of complexing. (4) The introduction of the intermolecular force field alone, together with changes in the phenol force field, account for all the more notable shifts as a result of hydrogen bonding of the internal mode frequencies of both the phenols and the pyridines. Although they may occur, it is not necessary to invoke any other changes in the internal force fields. (5) The internal mode frequency shifts of the phenol indicate the OH ⋯ N bending force constant as ≅0.07 mdyn A −1 . (6) The introduction of a bent hydrogen bond or of non-bonded interactions destroys the correlation between ƒ σ and Δ v s , suggesting that these do not occur. (7) A harmonic interaction force constant ƒ I between OH and H ⋯ N stretching can be introduced, and a set of ƒ OH ,ƒ σ and ƒ I , compatible with the observed frequencies, fit values from the Lippincott-Schroeder potential to within 2 %. For the phenol/pyridine complex, the best fit values are ƒ σ = 0.631, ƒ OH = 8.49, ƒ I = 1.94 (mdyn A −1 ). (8) A measure of the intermolecular stretching force field, the parameter ƒ R = (ƒ OH ƒ σ − ƒ I ) 2 / (ƒ OH − 2ƒ I + ƒ σ ) is developed. This “relaxation” force constant corresponds to dissociation of the complex, allowing the proton to adopt its minimum energy throughout. Values of ƒ R , fitted to the data, are almost independent of ƒ I , and show similar dependence on structure etc. to ƒ σ , including correlation with Δ v s . (9) The associated high frequency parameter K H = (ƒ OH - 2ƒ I + ƒ σ ) correlates closely with Δ v s . (10) All harmonic force fields imply the D-bond to be slightly weaker than the H-bond. This is probably a result of anharmonic terms. (11) The Lippincott-Schroeder potential does not satisfactorily represent the anharmonicity, if only cubic terms are used. Force fields and assignments for the uncomplexed phenols and pyridines have also been obtained.

Chemistry of bent bonds. XLII. Stereospecific rearrangement of strained cyclobutylcarbinyl cations

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChemistry of bent bonds. XLII. Stereospecific rearrangement of strained cyclobutylcarbinyl cationsPaul G. Gassman and Eugene A. ArmourCite this: J. Am. Chem. Soc. 1973, 95, 18, 6129–6131Publication Date (Print):September 1, 1973Publication History Published online1 May 2002Published inissue 1 September 1973https://doi.org/10.1021/ja00799a057RIGHTS & PERMISSIONSArticle Views59Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (405 KB) Get e-Alerts Get e-Alerts

Hybridization in some macrocyclic polyacetylenes

The hybridization in several cyclic polyacetylene compounds has been calculated by the maximum overlap method, assuming planar and non-planar geometries of the molecules. In the planar configuration the hybrids describing the molecular skeleton deviate from the corresponding bond directions. We have a few “bent” bonds, but in contrast to the situation in small rings, here the deviation angles are negative, i.e., the hybrids point toward the inside of the ring. Non-planar structures in which acetylene groups are kept in a plane and CCH 2 or CH 2 groups are displaced out of the plane show less deviation from the bond directions of bent bonds. Furthermore, the deviation angles decrease with an increase in the out-of-plane displacement of methylene groups. Finally, when the angle of bending of the molecules approaches 50°, the deviation vanishes, predicting a puckered conformation for the molecules. Correlation between CC stretching vibration frequencies and the corresponding CC bond overlap is discussed.

Chemistry of bent bonds. XXX. Diels-Alder approach to inside-outside bicyclics

Chemistry of bent bonds. XXX. Diels-Alder approach to inside-outside bicyclics

Localized orbital calculations of the bonding in SO, SO2F2, ClO3F and SOCL2

AbstractLocalized valence molecular orbitals have been obtained for SO, SO2F2, ClO3F and SOCl2 by the method due to Boys and Foster. The bonding in these molecules, in which the second row atom is exhibiting an excess valency, is discussed in terms of the form of these localized orbitals. The bonding of the second row atom to an oxygen atom is described by three bent bond orbitals, whilst bonding to a halogen atom is described by a single bond orbital. The participation of 3d functions in the various bonding and nonbonding orbitals is analysed in this localized orbital framework.

Chemistry of bent bonds. XXIX. Solvent determined mechanisms in the transition metal complex promoted rearrangement of bicyclo[1.1.0]butanes

Chemistry of bent bonds. XXIX. Solvent determined mechanisms in the transition metal complex promoted rearrangement of bicyclo[1.1.0]butanes