Better Than Word of Mouth

Hello, dear readers. It's been...a while. I promise the blog is not dead, just sleeping for now. My 2017 New Year's resolutions include sculpting specific time out for all the sci-writing goodness. Stay tuned.

Enough maudlin overtures. Now, on to the fun!

Strem has, as any synthetic guru would attest, the highest-quality metal precursors in the biz.* Now, you could spend a weekend cracking ampoules to find out, or just open to the Supporting Information of one of Jeff Bode's recent publications in Org. Lett. Perhaps you remember this reaction - SnAP synthesis of saturated heterocycles - best from a cheeky Derek Lowe tweet:

That's in reference to the stoichiometric incorporation of tin** in the reagent, which serves as a linchpin for the eventual transmetalation to a copper species and ring closure, neatly without disturbance of the ipso heteroatomic group.

Well, much to my surprise, Prof. Bode has climbed on the recent trend of showing one's work through tactful inclusion of smartphone pics to buoy up procedure adoption. Especially with fussy transition metals, valency, contaminants, poor environment, and a whole host of other factors lead to catalyst poisoning and color changes. In the SnAP case, the litmus test seems to be formation of a correctly ligated Cu(II) ion in lutidine relative to the (probable) hexaaquo cuprate species formed as a blue heterogeneous train wreck.

The kicker? The fairly indiscreet preference for the Strem copper(II) precursor over all other suppliers. Look at the change! Night and day, and key to making these reactions work.

You couldn't buy better advertising than this....right, Strem?
Bravo, Bode group! I look forward to seeing your colorful coupling chemistry in future reads.

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*Dear Strem: please send non-sequential $50 bills to See Arr Oh at Big City Company, USA
**SnAP. Get it? [drum kit]

Counterion Conundrum

(For Popkin's great Science News writeup, click here)
(Update - Also, Chemistry World!)

Update (11/13/13) - Blog buddy Lila Guterman of Science News has the inside scoop:
"An answer! Authors via @gabrielpopkin: cerium(III)chloride heptahydrate (99.9% pure) from Sigma (cat. nr. 228931-25G)"

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Fascinating news for the inorganic biochemistry fans out there: Scientists have ID'd a bacterium (Methylacidiphilum fumariolicum) living in highly acidic volcanic pools that seems to use rare earth metals in one of its enzymes. A multinational team modeled the enzyme with a variety of rare earth cores, and the bacterium appeared to selectively take them up in cell culture. Cool!

Just one small problem: What's the counterion?!?

My crack online reporting team has scoured the manuscript, finding only mentions of a mysterious Ce(III), along with triply-oxidized La* and Pr. Nowhere in the Supporting Information do they mention reagents used, and the reporter has confirmed that this subject wasn't broached.

Given the other salts the researchers added to the media, it's likely that they used either cerium (III) sulfate or cerium (III) chloride. However, Sigma-Aldrich sells no less than 10 different cerium (III) salts (Strem has over 20!), and I'm willing to bet they have markedly different bioavailability, oxidation potential, aqueous solubility...the works.

Readers, does anyone know what the cerium source is in this paper?** I certainly don't wish to draw unwarranted conclusions, but we're all still touchy over another recent dust-up having to do with a miraculous trace element.

Please let me know in the comments.

*IUPAC police: Throughout the paper, the authors refer to "Ln ions." Do you suppose they mean La (lanthanum)? Are elements abbreviated differently in other places?

**Interestingly, the authors note that their acidic growth media leached trace rare earths out of the glassware. I've never looked at that as a reaction contaminant, but I guess I'll have to start!