When the Ferrocene Analogy Breaks Down: Metallocene Transmetallation Chemistry

Abstract

AbstractFerrocene 1 and its dianionic Fe(bis)(dicarbollide) analogue 2 are classical compounds that display unusual stability. These compounds are not known to undergo transmetallation chemistry of the Fe‐center and have been used extensively as chemical building blocks with consistent integrity. In this manuscript we describe the preparation of a charge compensated Fe(bis)(dicarbollide) species 3 Fe and its unprecedented transmetallation chemistry to Ir. Such reactions are hitherto unknown for any transition metal metallocene or metallacarborane complex. Additionally, we show that 3 Fe can be deprotonated to afford the corresponding bis(NHC) Li‐carbenoid 5 that also displays unique reactivity. When 5 is reacted with [Ir(COD)Cl]2 it also undergoes a rapid transmetallation of the ferrocene “like” core to afford 6 but with the added twist that the Li‐carbenoid moiety stays intact and does not transmetalate. However, when 6 is subsequently treated with CuCl, the Li‐carbenoid transmetalates to Cu, which allows the controlled formation of the corresponding heterobimetallic Ir/Cu aggregate. Lastly, when Li‐carbenoid 5 is treated directly with CuCl, a double transmetallation occurs from both Fe to Cu and Li‐carbenoid to Cu, resulting in the trimetallic Cu cluster 8. These novel reactions pave the way for new synthetic methods to build complicated polymetallic clusters in a controlled fashion.