Palladium
DOI: 10.1063/PT.5.010034
Did you know that palladium is named after the asteroid Pallas ? William Hyde Wollaston, who discovered the element in 1803, picked the name to honor the asteroid’s discovery a year earlier.
I acquired that piece of periodic table trivia this morning when I was struggling to understand the science behind this year’s Nobel Prize in Chemistry . Richard Heck, Ei-ichi Negishi, and Akira Suzuki shared the prize “for palladium-catalyzed cross couplings in organic synthesis,” as the Royal Swedish Academy of Sciences put it.
Not knowing what “cross couplings” are and hoping for enlightenment, I turned to the 13-page Scientific Background that the academy posted on the Nobel website. The document described and explained the reactions that Heck, Negishi, and Suzuki developed. It also explained why those reactions are important. But it failed to satisfy my curiosity about what struck me as a key question: Why is palladium such an effective catalyst?
After some digging around on the internet, I found a partial answer. Palladium’s electronic configuration is
1s2 2s2p6 3s2p6d10 4s2p6d10
My apologies if you’re not familiar with notation. Anyway, the odd thing here is that it looks as though all palladium’s s, p, and d orbitals are full of electrons. Given that such repletion usually reduces, rather than enhances, an element’s chemical options, I had to dig further.
Palladium’s empty 5s orbital is lower in energy than its full 4d orbital. Presumably, when palladium reacts with other atoms, the ensuing exchange of electrons involves both the 5s and 4d orbitals. But that’s my presumption. If you know the electronic origin of palladium’s catalytic power, please tell me!
Despite my not attaining complete palladium enlightenment, I did discover another piece of trivia in the element’s Wikipedia entry :
In the run up to 2000, Russian supply of palladium to the global market was repeatedly delayed and disrupted because the export quota was not granted on time, for political reasons. The ensuing market panic drove the palladium price to an all-time high of $1100 per troy ounce in January 2001. Around this time, the Ford Motor Company, fearing auto vehicle production disruption due to a possible palladium shortage, stockpiled large amounts of the metal purchased near the price high. When prices fell in early 2001, Ford lost nearly US$1 billion.
The palladium ingot in the photo is about the size of two packs of playing cards. At today’s prices it would cost about $60 000.
