Henry Rzepa's Blog Chemistry with a twist

November 10, 2013

The subtle effect of dispersion forces on the shapes of molecules: benzyl magnesium bromide.

Filed under: Interesting chemistry — Tags: , , — Henry Rzepa @ 1:19 pm

In the previous post I mentioned in passing the Grignard reagent benzyl magnesium bromide as having tetrahedral coordination at Mg. But I have now noticed, largely through spotting Steve Bachrach’s post on “Acene dimers – open or closed?” another geometric effect perhaps worthy of note, certainly one not always noted in the past; that of dispersion forces.


July 5, 2013

Is CLi6 hypervalent?

A comment made on the previous post on the topic of hexa-coordinate carbon cited an article entitled “Observation of hypervalent CLi6 by Knudsen-effusion mass spectrometry[1] by Kudo as a amongst the earliest of evidence that such species can exist (in the gas phase). It was a spectacular vindication of the earlier theoretical prediction[2],[3] that such 6-coordinate species are stable with respect to dissociation to CLi4 and Li2.



  1. H. Kudo, "Observation of hypervalent CLi6 by Knudsen-effusion mass spectrometry", Nature, vol. 355, pp. 432-434, 1992. http://dx.doi.org/10.1038/355432a0
  2. E.D. Jemmis, J. Chandrasekhar, E.U. Wuerthwein, P.V.R. Schleyer, J.W. Chinn, F.J. Landro, R.J. Lagow, B. Luke, and J.A. Pople, "Lithiated carbocations. The generation, structure, and stability of CLi5+", Journal of the American Chemical Society, vol. 104, pp. 4275-4276, 1982. http://dx.doi.org/10.1021/ja00379a051
  3. P.V.R. Schleyer, E.U. Wuerthwein, E. Kaufmann, T. Clark, and J.A. Pople, "Effectively hypervalent molecules. 2. Lithium carbide (CLi5), lithium carbide (CLi6), and the related effectively hypervalent first row molecules, CLi5-nHn and CLi6-nHn", Journal of the American Chemical Society, vol. 105, pp. 5930-5932, 1983. http://dx.doi.org/10.1021/ja00356a045

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