Monday, July 9, 2012

Рутений Made It Possible

Ruthenium, or Рутений in Russian, was named for Russia. We should call the element russium--that would at least be more historically descriptive--but ruthenium it is.* The first detectable amounts came from platinum ores in the Ural mountains--first discovered in the 1820's. The element is exceedingly rare--and thus expensive--and yet it too has its unique chemical niche. 

Ruthenium is the first element in the series 1 to 44 which can be fully stripped of 8 electrons to give a stable oxidation state of VIII.** Step just one atomic number backwards, to technetium, and there aren't 8 valence electrons to lose--only 7; step one element to the right, to rhodium, and the nucleus is already too electronegative to give up more than 6 electrons.  This makes ruthenium special--its willingness to fully yield to rapacious oxygen.

Ruthenium isn't really famous for much. It enjoyed brief fame in 1952 when ruthenocene was prepared by analogy to ferrocene, but it always seemed a little under-represented in catalysis until a chemist named Robert Grubbs (originally from Possum Trot holler in Kentucky), put ruthenium on the map with his Nobel-prize winning work centered around olefin metathesis.

"Olefin metathesis" has interesting history as a term--taken apart, "olefin" comes from oléfiant which means oil-forming and which ultimately comes from the roots oleum + facere. Olefin is an old word as chemistry words go--not so old to be practically archaic like oleum or vitriol, but still old. The modern term for olefin is alkene--organic hydrocarbons having one or more unsaturated double bond. The terms "polyunsaturated fat" and "trans fat" refer to olefins, FWIW.

Metathesis is a special word meaning rearrangement. There's a grammatical sense of the word which means transposition, and the chemical sense is just a metaphor. If we let the equal sign be a double bond, olefin metathesis refers to

a=b + c=d --> a=c + b=d.

See what happened there? Transposition.
*Ruthenia corresponded to a much smaller region of what is now in the Ukraine. The Ural region was unknown to the Romans.
**Wikipedia notes claims to the existence of Fe(VIII) as in FeO4 but the claim is tentative.

No comments:

Post a Comment