Reversible Hydride Migration from C5Me5 to RhI Revealed by a Cooperative Bimetallic Approach

The use of cyclopentadienyl ligands in organometallic chemistry and catalysis is ubiquitous, mostly due to their robust spectator role. Nonetheless, increasing examples of non-innocent behaviour are being documented. Here, we provide evidence for reversible intramolecular C−H activation at one methyl terminus of C₅Me₅ in [(η-C₅Me₅)Rh(PMe₃)₂] to form a new Rh−H bond, a process so far restricted to early transition metals. Experimental evidence was acquired from bimetallic rhodium/gold structures in which the gold center binds either to the rhodium atom or to the activated Cp* ring. Reversibility of the C−H activation event regenerates the Rh^I and Au^I monometallic precursors, whose cooperative reactivity towards polar E−H bonds (E=O, N), including the N−H bonds in ammonia, can be understood in terms of bimetallic frustration.