Posted on 11/18/2005 12:13:38 PM PST by John Will
F. Albert Cotton and his coworkers at Texas A&M University surprised chemists in 1964 with evidence that the [Re2Cl8]2 ion contained the first known multiple bond between two metal atoms. Not only was it a multiple bond, it was an unprecedented quadruple bond. Cotton convinced the world that he was right, and inorganic chemistry hasn't been the same since.
Now, Philip P. Power at the University of California, Davis, and his coworkers report evidence for the first "quintuple" bond between two metal atoms in the dichromium complex, RCrCrR, where R is a bulky terphenyl ligand (Science, published online Sept. 22, dx.doi.org/10.1126/science.1116789). The chromium dimer exists as air- and moisture-sensitive dark red crystals that are stable up to 200 °C.
(Excerpt) Read more at pubs.acs.org ...
The name is Bond. Quintuple Bond...
(come on, somebody had to say it)
And you said it before me, dammit!
Sweet!
The energy requirements to break the bond must be staggering.
Not necessarily. The thing sounds pretty unstable, so it's clear that those electrons really don't enjoy being crammed into that hybrid orbital very much...
In other news scientists have finally found a way to make a monkey wash a cat!
http://www.brud.info/video/monkey_washing_cat.mov
Neat. I got my M.S. in chemistry at Texas A&M, although it was in organic chemistry.
Why aren't they the same making it?
Atoms shaken, not stirred.
If you can make armor out of this it would be nigh impenetrable!
Not necessarily. The thing sounds pretty unstable, so it's clear that those electrons really don't enjoy being crammed into that hybrid orbital very much...
Agreed...I'd need to see the orbits and all the details, but this is either INCREDIBLY dense and stable, or it's so volatile it makes Californium look like Cobalt.
SO it's an Ion Flemming?
A combination of Roger Moore, Piece Borsnan, Sir Sean Connery, Roger Dalton, David Niven?
I'd be very curious to learn what it's vibrational frequency would be compared to other metal-metal bonds. Without reading the article, I bet it involves lots of d orbitals.
Here is a line from the text.
Quintuple bond is proposed to form by the sharing of five electron pairs in five bonding 3d orbitals in this chromium dimer with bulky terphenyl ligands (R = isopropyl).
It sounds like they are sterically isolating most of the metal atoms so nothing else can get in to react with the metals. That would imply that this bond is highly reactive and needs a lot of protection to stay in tact.
"There are now thousands of examples of quadruple-bonded transition-metal compounds, including chromium(II) compounds with quadruple bonds, Cotton tells C&EN. The formulation of quadruple bonds in terms of the overlap of orbitals is clear, he says. But to consider a quintuple or sextuple bond "always entails some amount of heuristic argument."
In theory, diatomic transition-metal species can form up to six bonds between their valence shell s and d orbitals. A few sextuple-bonded compounds have been trapped at low temperature and observed spectroscopically, but they are unlikely to be isolated as stable compounds at room temperature."
Hmm...then again...
Transition elements tend to have high tensile strength, density and melting and boiling points. As with many properties of transition metals, this is due to d orbital electrons' ability to delocalise within the metal lattice. In metallic substances, the more electrons shared between nuclei, the stronger the metal.
There are several common characteristic properties of transition elements:
* They form coloured compounds
* They can have a variety of different oxidation states
* They are good catalysts
* They are silvery-blue at room temperature (except copper and gold)
* They are solids at room temperature (except mercury)
* They form complexes, which is described by crystal field theory.
We observe color as varying frequencies of electromagnetic radiation in the visible region of the electromagnetic spectrum. Different colors result from the changed composition of light after it has been reflected, transmitted or absorbed after hitting a substance. Because of their structure, transition metals form many different colored ions and complexes. Color even varies between the different ions of a single element - MnO4− (Mn in oxidation state 7+) is a purple compound, whereas Mn2+ is pale-pink.
The color of a complex depends on:
* the nature of the metal ion, specifically the number of electrons in the d orbitals
* the arrangement of the ligands around the metal ion (for example geometric isomers can display different colors)
* the nature of the ligands surrounding the metal ion. The stronger the ligands then the greater the energy difference between the split high and low 3d groups.
So, I guess we need to wait for the full analysis here...but I'd LOVE to see the results!
From what I read, and posted, you are spot on!
SHAME ON YOU!!!!!!
Appropriate screen name, though...
I bet it's got pretty typical physical properties of a large organic molecule. It sounds (as someone else has suggested) that the two triphenylmethyl ligands help to shield the chromium atoms and (my guess) help delocalize the electrons through resonance structures.
I get a new catalog from Aldritch and Alfa Aesar every year, and I'm always blown away by the wealth of new reagents that were not invented when I was a chemistry student.
Yes, but as they went from 2+ Ions across the period to 3+, they went from reducing to oxidizer....I'd love to see what this does.
The proton pull must be a Beeyotch here!
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