[Rh2(MEPY)4] and [BiRh(MEPY)4]: Convenient Syntheses and Computational Analysis of Strikingly Dissimilar Siblings

[Rh-2(MEPY)(4)] is a versatile catalyst for asymmetric synthesis but its preparation requires purification by chromatography on surface-modified silica. A higher yielding procedure based on a more convenient work-up is presented herein. Moreover, a much improved method for the preparation of [BiRh(OTfa)(4)] is described, which makes this heterobimetallic complex readily available. Subsequent exchange of the trifluoroacetate ligands opens access to a so far underappreciated family of (chiral) paddlewheel complexes. While [BiRh] complexes comprising four carboxylate ligands are highly adequate for intermolecular asymmetric cyclopropanation reactions, [BiRh(MEPY)(4)] as the heterobimetallic cousin of [Rh-2(MEPY)(4)] was found to be surprisingly unreactive; DFT calculations uncover the reasons for this inertia.

Automated summary

A more convenient and higher-yielding preparation method for [Rh-2(MEPY)(4)] catalyst is presented in this study, along with an improved preparation method for [BiRh(OTfa)(4)], making these compounds more readily available. The reactivity difference between [BiRh(MEPY)(4)] and [Rh-2(MEPY)(4)] in asymmetric synthesis is revealed, with DFT calculations uncovering the reasons for this inertness.