Much like chocolate, some of us metallaholics cannot get enough. So WUQXIP proved an irresistible frolic (DOI: 10.1021/om020789h). Let us start with benzene.  It can have metals added in two ways, whilst preserving its essential aromaticity. Triple metal delight. Making a metal sandwich is of course very well known, ferrocene being the first example where the bonding was identified.

Do you fancy a story going from simplicity to complexity, if not absurdity, in three easy steps? Read on! The following problem appears in one of our (past) examination questions in introductory organic chemistry. From relatively mundane beginnings, one can rapidly find oneself in very unexpected territory. How would one make 3-nitrobenzonitrile?

One approach to reporting science which is perhaps better suited to the medium of a blog than a conventional journal article is the opportunity to follow ideas in unexpected, even unconventional directions. Thus my third attempt, like a dog worrying a bone, to explore hypervalency.

In the last post, IH ₇ was examined to see if it might exhibit true hypervalency. The iodine, despite its high coordination, turned out not to be hypervalent, with its (s/p) valence shell not exceeding eight electrons (and its d-shell still with 10, and the 6s/6p shells largely unoccupied). Instead, the 14 valence electrons (7 from H, 7 from iodine) fled to the H…H regions.

The Wikipedia page on hypervalent compounds reveals that the concept is almost as old as that of normally valent compounds.

Carbon dioxide is much in the news, not least because its atmospheric concentration is on the increase. How to sequester it and save the planet is a hot topic. Here I ponder its solid state structure, as a hint to its possible reactivity, and hence perhaps for clues as to how it might be captured. The structure was determined (DOI 10.1103/PhysRevB.65.104103) as shown below. The structure of solid carbon dioxide.

In this post, I will take a look at what must be the most extraordinary small molecule ever made (especially given that it is merely a hydrocarbon). Its peculiarity is the region indicated by the dashed line below. Is it a bond? If so, what kind, given that it would exist sandwiched between two inverted carbon atoms?

In the previous post, I ruminated about how chemists set themselves targets. Thus, having settled on describing regions between two (and sometimes three) atoms as bonds , they added a property of that bond called its order . The race was then on to find molecules which exhibit the highest order between any particular pair of atoms.

Climbers scale Mt. Everest, because its there , and chemists have their own version of this. Ever since G. N. Lewis introduced the concept of the electron-pair bond in 1916, the idea of a bond as having a formal bond-order has been seen as a useful way of thinking about molecules. The initial menagerie of single, double and triple formal bond orders (with a few half sizes) was extended in the 1960s to four, and in 2005 to five.

So ingrained is the habit to think of a bond as a simple straight line connecting two atoms, that we rarely ask ourselves if they are bent, and if so, by how much (and indeed, does it matter?). Well Hursthouse, Malik, and Sales, as long ago as 1978, asked just such a question about the unlikeliest of bonds, a quadruple Cr-Cr bond, found in the compound di-μ-trimethylsilylmethyl-bis-[(tri-methylphosphine)