Mercury (IV) tetrafluoride attracted much interest when it was reported in 2007[cite]10.1002%2Fanie.200703710[/cite] as the first instance of the metal being induced to act as a proper transition element (utilising d-electrons for bonding) rather than a post-transition main group metal (utilising just s-electrons) for which the HgF2 dihalide would be more normal (“Is mercury now a transition element?”[cite]http://dx.doi.org/10.1021%2Fed085p1182[/cite]). Perhaps this is the modern equivalent of transmutation! Well, now we have new speculation about how to induce the same sort of behaviour for caesium; might it form CsF3 (at high pressures) rather than the CsF we would be more familiar with.[cite]10.1038/nchem.1754[/cite] Here I report some further calculations inspired by this report.
Archive for the ‘Hypervalency’ Category
VSEPR Theory: A closer look at chlorine trifluoride, ClF3.
Saturday, July 27th, 2013Valence shell electron pair repulsion theory is a simple way of rationalising the shapes of many compounds in which a main group element is surrounded by ligands. ClF3 is a good illustration of this theory.
The “shocking” Xe-Au bond.
Saturday, January 21st, 2012Chemistry rarely makes it to the cover of popular science magazines. Thus when this week, the New Scientist ran the headline “Forbidden chemistry. Reactions they said could never happen“, I was naturally intrigued. The examples included Woodward and Hoffmann’s “symmetry-forbidden” reactions, which have been the subject of several posts here already. But in the section on nobel gas chemistry, the same Hoffmann is reported as having been shocked to hear of a compound of xenon and gold, both of which in their time were thought of as solidly inert, and therefore even more unlikely to form a union.
Hunt the charge: the Cheshire cat of chemistry
Thursday, September 29th, 2011Charges in chemistry, like the grin on Lewis Carroll’s cat, can be mysterious creatures. Take for example the following structure, reported by Paul Lickiss and co-workers (DOI: 10.1039/b513203g).
Extreme chemical intimacy: the Xe2@C60 ion-pair.
Wednesday, August 3rd, 2011Unusual bonds are always intriguing, and the Xe-Xe bond is no exception. It was first reported (10.1002/anie.199702731) for the species Xe2+. Sb4F21– and its length (3.09Å) was claimed as “unsurpassed in length in main group chemistry by any other element -element bond”. Krapp and Frenking then creatively tweaked the bond (in a computer). The counterion was replaced by C60, and the two xenon atoms placed inside! Buckyballs have a fascinating ability to absorb electrons, up to six in fact, from whatever is placed inside the cavity, and so this assembly acts as a rather intriguing ion-pair. So the issue reduces to how many electrons does C60 manage to scavenge from two Xenon atoms, and what is the nature of any resulting bonding formed between these two atoms?
Hexavalent carbon revisited (and undecavalent boron thrown in).
Sunday, June 26th, 2011A little while ago, I speculated (blogs are good for that sort of thing) about hexavalent carbon, and noted how one often needs to make (retrospectively) obvious connections between two different areas of chemistry. That post has attracted a number of comments in the two years its been up, along the lines: what about carboranes? So here I have decided to explore that portal into boron chemistry. The starting point is the reported crystal structure of a molecule containing a CH12B11– anion (DOI: 10.1021/ja00201a073). This differs from the molecule I previously reported in having not so much 5C-C + 1C-H bonds around a single carbon, but instead 5B-C + 1C-H bonds. The basic cluster is much in fashion (as B12Cl122-) for its properties as a non-coordinating counterion.