For The First Time, A Five-fold Bond

[phantom power]

Chemists at UC Davis have made the first stable compound with a five-fold bond between two metal atoms. The work with chromium could give researchers new insights into the nature of chemical bonding.

Much of chemistry is about understanding how bonds are made and broken. For most of the history of chemistry, only single, double or triple bonds were known. Multiple bonds are particularly important in carbon chemistry, but only certain metals are theoretically capable of more than triple bonds, said Philip Power, professor of chemistry at UC Davis and senior author on the paper.

The dark red crystals were synthesized by Tailuan (Peter) Nguyen, a graduate student in Power's laboratory. The chromium-based compound is stable at room temperature but decomposes in the presence of water, and spontaneously ignites when exposed to air.

To make the compound, Nguyen and Power attached large carbon-based molecules to chromium atoms, constraining how they could behave. They were then able to coax the chromium atoms to bond with each other. The multiple bonding was confirmed by X-ray crystallography and magnetic measurements.

http://www.sciencedaily.com/releases/2005/10/051014072049.htm

[Ediacara]

1. Weird

How did they put this stuff in an XRD? And how do they store it? In oil (like alkaline metals), or in a vaccuum, or in the presence of neon or argon or something?

[NNadir]

4. It is probably stored under dry nitrogen.

Most chemists these days are accustomed to working under nitrogen. It is a rare compound that needs to be stored under argon, which is more expensive than nitrogen. Nitrogen is generally not all that reactive, and for most purposes is inert. To be absolutely scrupulous, one can pass the nitrogen over a drying agent, which is generally a hygroscopic solid. Some of these are commercial products like the product Drierite, which has a color indicator that turns it from blue to red when it has absorbed too much water.

Generally one uses rubber septa to seal flasks. In the case of difficult solids, it is possible to transfer them in a glove box, maintained with a positive nitrogen pressure. Transfers of liquid reactants or solutions is done using canulas which are tubes with needle point ends. The driving force is a little nitrogen pressure. Typically the gas is vented through a needle. The needle can be attached to a drying tube.

Sometimes it is possible to grow crystals simply by running a stream of dry nitrogen over a solvent until it evaporates.

Many instruments are equipped with nitrogen or argon purge lines as well.

Typically the use of oils is to be discouraged, except with certain reactive metals, most typically sodium and potassium, but also rubidium and cesium as well. Oils make compounds difficult to characterize.

In any case, this is cool work, and I hope I will remember to read it when it's published.

Quadruple metal-metal bonds have been known for some time. These bonds, for the benefit of anyone who might be interested in such things, consist of sigma electrons, 4 pi electrons and 2 delta electrons, obtained by mixing s, p and d orbitals of the two bonded atoms. The octachlorodirhenium anion, characterized in 1964, has such a bond, as does ditechnetium dichlorotetrapivaloate.

[pscot]

2. Ice nine

n/t

[ewagner]

3. Full Metal Alchemist?? n/t