Posts Tagged ‘Hypervalency’

Chasing ever higher bond orders; the strange case of beryllium.

Monday, February 7th, 2022

Ever since the concept of a shared two-electron bond was conjured by Gilbert N. Lewis in 1916,[1] chemists have been fascinated by the related concept of a bond order (the number of such bonds that two atoms can participate in, however a bond is defined) and pushing it ever higher for pairs of like-atoms. Lewis first showed in 1916[1] how two carbon atoms could share two, four or six electrons to achieve a bond order of up to three. It took quite a few decades for this to be extended to four for carbon (and nitrogen) and that only with some measure of controversy and dispute (for one recent brief summary, see[2]).

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References

  1. G.N. Lewis, "THE ATOM AND THE MOLECULE.", Journal of the American Chemical Society, vol. 38, pp. 762-785, 1916. http://dx.doi.org/10.1021/ja02261a002
  2. H.S. Rzepa, "Routes involving no free C2 in a DFT-computed mechanistic model for the reported room-temperature chemical synthesis of C2", Physical Chemistry Chemical Physics, vol. 23, pp. 12630-12636, 2021. http://dx.doi.org/10.1039/D1CP02056K

Never mind main group “hypervalency”, what about transition metal “hypervalency”?

Sunday, March 18th, 2018

I have posted often on the chemical phenomenon known as hypervalency, being careful to state that as defined it applies just to “octet excess” in main group elements. But what about the next valence shell, occurring in transition metals and known as the “18-electron rule”? You rarely hear the term hypervalency being applied to such molecules, defined presumably by the 18-electron valence shell count being exceeded. So the following molecule (drawn in three possible valence bond representations) first made in 1992 intrigues.[1]

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References

  1. R. Ahlrichs, D. Fenske, H. Oesen, and U. Schneider, "Synthesis and Structure of [Ni(PtBu6)] and [Ni5(PtBu)6(CO)5] and Calculations on the Electronic Structure of [Ni(PtBu)6] and (PR)6, R = tBu,Me", Angewandte Chemie International Edition in English, vol. 31, pp. 323-326, 1992. http://dx.doi.org/10.1002/anie.199203231

Identification of a simplest hypervalent hydrogen fluoride anion.

Friday, December 8th, 2017

An article with the title shown above in part recently appeared.[1] Given the apparent similarity of HF1- to CH3F1- and CH3F2-, the latter of which I introduced on this blog previously, I thought it of interest to apply my analysis to HF1-.

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References

  1. M. Liu, H. Chen, C. Chin, T. Huang, Y. Chen, and Y. Wu, "Identification of a Simplest Hypervalent Hydrogen Fluoride Anion in Solid Argon", Scientific Reports, vol. 7, 2017. http://dx.doi.org/10.1038/s41598-017-02687-z

A connected world (journals and blogs): The benzene dication.

Thursday, April 10th, 2014

Science is rarely about a totally new observation or rationalisation, it is much more about making connections between known facts, and perhaps using these connections to extrapolate to new areas (building on the shoulders of giants, etc). So here I chart one example of such connectivity over a period of six years.

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A connected world (journals and blogs): The benzene dication.

Thursday, April 10th, 2014

Science is rarely about a totally new observation or rationalisation, it is much more about making connections between known facts, and perhaps using these connections to extrapolate to new areas (building on the shoulders of giants, etc). So here I chart one example of such connectivity over a period of six years.

(more…)

A connected world (journals and blogs): The benzene dication.

Thursday, April 10th, 2014

Science is rarely about a totally new observation or rationalisation, it is much more about making connections between known facts, and perhaps using these connections to extrapolate to new areas (building on the shoulders of giants, etc). So here I chart one example of such connectivity over a period of six years.

(more…)

A connected world (journals and blogs): The benzene dication.

Thursday, April 10th, 2014

Science is rarely about a totally new observation or rationalisation, it is much more about making connections between known facts, and perhaps using these connections to extrapolate to new areas (building on the shoulders of giants, etc). So here I chart one example of such connectivity over a period of six years.

(more…)

A connected world (journals and blogs): The benzene dication.

Thursday, April 10th, 2014

Science is rarely about a totally new observation or rationalisation, it is much more about making connections between known facts, and perhaps using these connections to extrapolate to new areas (building on the shoulders of giants, etc). So here I chart one example of such connectivity over a period of six years.

(more…)

A connected world (journals and blogs): The benzene dication.

Thursday, April 10th, 2014

Science is rarely about a totally new observation or rationalisation, it is much more about making connections between known facts, and perhaps using these connections to extrapolate to new areas (building on the shoulders of giants, etc). So here I chart one example of such connectivity over a period of six years.

(more…)

A connected world (journals and blogs): The benzene dication.

Thursday, April 10th, 2014

Science is rarely about a totally new observation or rationalisation, it is much more about making connections between known facts, and perhaps using these connections to extrapolate to new areas (building on the shoulders of giants, etc). So here I chart one example of such connectivity over a period of six years.

(more…)