The di-anion of dilithium (not the Star Trek variety): Another “Hyper-bond”?

September 16th, 2017
No Gravatar

Early in 2011, I wrote about how the diatomic molecule Be2 might be persuaded to improve upon its normal unbound state (bond order ~zero) by a double electronic excitation to a strongly bound species. I yesterday updated this post with further suggestions and one of these inspired this follow-up.

Read the rest of this entry »

Two new types in the chemical bonding zoo: exo-bonds and hyper-bonds?

September 6th, 2017
No Gravatar

The chemical bond zoo is relatively small (the bond being a somewhat fuzzy concept, I am not sure there is an actual count of occupants). So when two new candidates come along, it is worth taking notice. I have previously noted the Chemical Bonds at the 21st Century-2017: CB2017 Aachen conference, where both were discussed.

Read the rest of this entry »

One more WATOC 2017 Report.

August 31st, 2017
No Gravatar

Conferences can be intense, and this one is no exception. After five days, saturation is in danger of setting in. But before it does, I include two more (very) brief things I have learnt.

Read the rest of this entry »

(another) WATOC 2017 report.

August 29th, 2017
No Gravatar

Another selection (based on my interests, I have to repeat) from WATOC 2017 in Munich.

  1. Odile Eisenstein gave a talk about predicted 13C chemical shifts in transition metal (and often transient) complexes, with the focus on metallacyclobutanes. These calculations include full spin-orbit/relativistic corrections, essential when the carbon is attached to an even slightly relativistic element. She noted that the 13C shifts of the carbons attached to the metal fall into two camps, those with δ ~+80 ppm and those with values around -8 ppm. These clusters are associated with quite different reactivities, and also seem to cluster according to the planarity or non-planarity of the 4-membered ring. There followed some very nice orbital explanations which I cannot reproduce here because my note taking was incomplete, including discussion of the anisotropy of the solid state spectra. A fascinating story, which I add to here in a minor aspect. Here is a plot of the geometries of the 52 metallacyclobutanes found in the Cambridge structure database. The 4-ring can be twisted by up to 60° around either of the C-C bonds in the ring, and rather less about the M-C bonds. There is a clear cluster (red spot) for entirely flat rings, and perhaps another at around 20° for bent ones, but of interest is that it does form something of a continuum. What is needed is to correlate these geometries with the observed 13C chemical shifts to see if the two sets of clusters match. I include this here because in part such a search can be done in “real-time” whilst the speaker is presenting, and can then be offered as part of the discussion afterwards. It did not happen here because I was chairing the meeting, and hence concentrating entirely on proceedings!

    Read the rest of this entry »

WATOC 2017 report.

August 29th, 2017
No Gravatar

The triennial conference is this year located in Munich. With 1500 participants and six parallel sessions, this report can give only a flavour of proceedings.

Read the rest of this entry »

The Bond Slam – a second peek inside.

August 12th, 2017
No Gravatar

At the moment, the bond slam is something of a home from home for this blog and since much of my activity is happening there rather than here, I thought I might give you pointers to some of the topics, which are evolving, so to speak, before our very eyes.

Read the rest of this entry »

Chemical Bonds at the 21st Century – 2017: the Bond Slam.

August 2nd, 2017
No Gravatar

It is always interesting to observe conference experiments taking place. The traditional model involves travelling to a remote venue, staying in a hotel, selecting sessions to attend from a palette of parallel streams and then interweaving chatting to colleagues both old and new over coffee, lunch, dinner or excursions. Sometimes conferences occur in clusters, with satellite meetings breaking out in the vicinity, after a main conference has done the job of attracting delegates to the region. Here I bring to your attention one such experiment, the Bond Slam which is part of a satellite meeting in Aachen to be held September 2-4 2017 on the topic of Chemical Bonds at the 21st Century, following on from the WATOC 2017 congress in Munich Germany a few days earlier.

Read the rest of this entry »

Wild flowers in West London.

July 24th, 2017
No Gravatar

Bees are having a tough time around the world. Oddly, they are surviving very well in cities. One reason are the wild flower meadows in London and for some summer relief I thought I would tell you the story of the one shown below.

Read the rest of this entry »

Accessing (raw) chemical data: a peek into the CIF format.

July 21st, 2017
No Gravatar

There is much focus at the moment on how to ensure experimental replicability in e.g. the molecular sciences. An important aspect of that is having access to FAIR data; data which is findable, accessible, inter-operable and re-usable. One of the “gold standards” in chemistry is the data associated with crystal structures. Here I take an inside peek into the standard file-type for carrying crystal structure data, the CIF file (the Crystallographic Information File).

Read the rest of this entry »

Dispersion “bonds” not involving just hydrogen: can it work for F…H?

July 18th, 2017
No Gravatar

The effects of loading up lots of dispersion attractions (between t-butyl groups) into a compact molecule has the interesting consequence of allowing two “non-bonded” hydrogen atoms to approach to ~1.5Å of each other, thus creating the appearance of a “bond” where one normally would not be found. Can such an effect be injected into other combinations of two atoms, say H and F? Here I briefly explore this notion.

Read the rest of this entry »