|Source: Thomas Porostocky / Nature News|
OK, I understand the point of the graphic, but I'd like to tackle a few pedagogical questions. First, has anyone ever seen a real-life compound like this? I searched Reaxys, but couldn't find any examples of a Re center bound to three different chalcogens. Closest I could find were some rhenium selenide clusters.
Second, what's the valency around that Re center? My good buddy Wikipedia (source of all truthful information on the internet, right?) informs me that Re can have oxidation numbers from -1 to +7. Well, OK, so I'll assume double bonds between all the heteroatoms and Re (which also doesn't come up via Reaxys or our buddy Google), but I'd still question whether, as drawn, we have Re(+4), five, six, or seven!
So let's assume a stable compound...is it actually "chiral?"
Textbooks on inorganic chemistry indicate that Re(VII) complexes with oxo ligands prefer the square pyramidal geometry. Well, you say, it has two other bivalent chalcogens, so maybe it's tetrahedral after all? My ligand field theory spider sense tells me that Re(VII) is d0, which should have a tetrahedral geometry, but I don't know enough about this peculiar complex to know if it takes on solvent molecules (becoming octahedral?) or undergoes inversion. Maybe in the gas phase (lasers!), in a vacuum, it's just a plain ol' tetrahedron.
I'm not attacking the artist, he's a graphical designer, not a chemist. And I get the message - it's a physical chemistry model experiment to show how chiral molecules show slightly different physical parameters, perhaps ones that can be measured. The designers use a single periodic column to show how molecular number assigns chirality (C-I-P convention) and to enforce a striking enantiomeric disparity. It's just hard for me, as a non-physical chemist, to go this far out on the edge.
Please, to illustrate this concept, let's use known examples (amino acids, anyone?) first, and then transition out to the edge. Then we won't suffer Feynman's cargo cult caveat: "...you should not fool the layman when you're talking as a scientist."
Update (1/5/12, 3:44PM) - I realize that the Darquie experiments referred to in the text involve (potential) formation of such a compound. I simply find "strange bedfellows" for text that leads with biological homochirality, since Re(VII) compounds are unlikely to be something one encounters in cells!
(1/5/12, 4:19) - Cleaned up text in grafs 2-3 to focus the post.