Rhodium Gets It Done

Interesting, informative intermediates from Rh(I) silylation

In this week's Science, Hartwig and Cheng disclose some pretty swanky C-H activation chemistry. By combining Rh(I) dimer, a really bulky diphosphine ligand, a cheap, bulky hydrosilane, and a hydrogen "acceptor," the pair turn relatively distant aromatic bonds into highly functional silicon handles. In certain cases, tricks like capping a carbazole with a bulky TIPS group direct the silylation para - all the way to the other side of the aromatic ring!

The authors quickly point out that this silylation runs at "low" temps (80 deg C), uses fairly cheap commercially-available reagents, and occurs with almost reversed selectivity to the corresponding direct borylation conditions. But my favorite part comes from a deep dive into the Supporting Information. Far from the discussion of academic over-publishing we've had for the past few days, Hartwig and Cheng really sculpt a great paper here: Stability studies. Reactivity differences (Si vs. B). Cross-couplings. Preliminary mechanistic details.

As always, there's tons more to do. Getting out of the glovebox with a more stable Rh precursor, or translating the reactivity to an earlier metal (a tall order!). Deeper mechanistic studies would certainly show the way. Even more tantalizing? Using single-enantiomer versions of the bulky ligands to incorporate some chiral-at-silicon synthons. I can't wait to see the rest of this story.