Proposed type of chemical isomerism based on bond length
In chemistry, bond stretch isomerism is a concept of isomerism based on variations of bond length. The concept was proposed in the 1970s but was refuted in the 1990s.[1]
The phenomenon was first invoked to explain the observation of blue and green isomers of mer-MoOCl2(PMe2Ph)3, where PMe2Ph is dimethylphenylphosphine. These isomers were shown, purportedly, by X-ray crystallography to differ with respect to the length of the Mo-O bond, which differed by 0.2 Å. Subsequent work showed that the supposed green bond stretch isomer consisted of blue mer-MoOCl2(PMe2Ph)3 contaminated with a small amount of yellow mer-MoCl3(PMe2Ph)3. The nearly isomorphous replacement of Mo-O unit with small amounts of Mo-Cl unit results in artifactually long Mo-O distance in the green sample. In essence the deception arises because the crystallographic disorder was not modeled appropriately. Several such examples were uncovered.
^Parkin, G., "Bond-Stretch Isomerism in Transition Metal Complexes: a Reevaluation of Crystallographic Data", Chem. Rev. 1993, volume 93, 887-911. doi:10.1021/cr00019a003
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In chemistry, bondstretchisomerism is a concept of isomerism based on variations of bond length. The concept was proposed in the 1970s but was refuted...
alkane). When n is four or more, isomers are possible, distinguished by the position and conformation of the double bond. Alkenes are generally colorless...
Protein folding concerns the complex geometries and different isomers that proteins can take. A bond angle is the geometric angle between two adjacent bonds...
because of their different structures. Stereoisomers, a particular type of isomer, may have very similar physico-chemical properties and at the same time...
with a boiling point of 23.5 °C. It is the predominant tautomer and an isomer of cyanic acid (aka. cyanol) (H−O−C≡N). The derived anion of isocyanic acid...
higher pyramidal cations. Stohrer, W.D.; Hoffmann, R. (1972). "Bond-stretchisomerism and polytopal rearrangements in (CH)5+, (CH)5-, and (CH)4CO". J...
quantitatively estimate the bond energy, and the sign and magnitude of a bond's chemical polarity, which characterizes a bond along the continuous scale...
below the boiling point (where the cis isomer is more stable) because it does not actually increase the total bond order and because the unpaired electron...
Phase III is typically associated with large-deformation covalent bondstretching. Alpha-helices in proteins may have low-frequency accordion-like motion...
For different central metal geometries there can be different numbers of isomers depending on the ligand's topology and the geometry of the metal center...
magnetic properties of some six-coordinate cobalt(II) complexes' electronic isomers". J. Am. Chem. Soc. 83 (17): 3732–3734. doi:10.1021/ja01478a051. Edgar...
cation has an intense IR peak at 1987 cm−1 for the C=C+ stretching. More importantly, the bond angles between the vinyl cation carbons and the first carbon...
example of the trans effect is the synthesis of cisplatin and its trans isomer. Starting from PtCl42−, the first NH3 ligand is added to any of the four...
Coordination increased the C-C-CO bond angle and bond lengths, indicating increased ylidic character. Using the average CO stretching frequency as a measure of...
vibration of the B-H bond and the S-H bond. However, it has been pointed out that for o-carborane, which has a very strong B−H stretch at 2575 cm−1, the...
shows an infrared vibrational frequency of 1220 cm−1 due to the stretching of the bond. The free radical nature of PO makes it highly reactive and unstable...
vibrational progression from the stretching and breathing vibrations of IrB3 could be assigned in the overlaid spectra of both isomers present in the cluster beam...
This mode is known as symmetric stretch (v₁). The symmetry in the N-H bondstretching is reflected in this stretching motion. Of the three vibrational...
doubly bridging CO ligands, denoted μ2-CO or often just μ-CO, the bondstretching frequency νCO is usually shifted by 100–200 cm−1 to lower energy compared...
to the cis isomer which undergoes anti elimination (1.0108), both results are large enough to be indicative of weakening of the C-N bond in the transition...
[Cp*IrCl2]2 McGrady, John E. (2000). "[(Cp*RuCl)2(μ-Cl)2]: bond-stretch or spin-state isomerism?". Angewandte Chemie International Edition. 39 (17): 3077–3079...
been prepared. The molecules are linear. In ArAuCl the Ar−Au bond is 2.47 Å, the stretching frequency is 198 cm−1 and the dissociation energy is 47 kJ/mol...
as cis and trans isomers. The C=N bonds, which are near 129 picometers in length, are shorter than C-N single bonds. Cis/trans isomers are observed. The...
can have either cis or trans geometry. The controlled synthesis of each isomer of the polymer, cis-polyacetylene or trans-polyacetylene, can be achieved...
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