Bonding and Reactivity in Terminal versus Bridging Arenide Complexes of Thorium Acting as Th^II Synthons

Thorium redox chemistry is extremely scarce due to the high stability of ThIV . Here we report two unique examples of thorium arenide complexes prepared by reduction of a ThIV -siloxide complex in presence of naphthalene, the mononuclear arenide complex [K(OSi(Ot Bu)3 )3 Th(η6 -C10 H8 )] (1) and the inverse-sandwich complex [K(OSi(Ot Bu)3 )3 Th]2 (μ-η6 ,η6 -C10 H8 )] (2). The electrons stored in these complexes allow the reduction of a broad range of substrates (N2 O, AdN3 , CO2 , HBBN). Higher reactivity was found for the complex 1 which reacts with the diazoolefin IDipp=CN2 to yield the unexpected ThIV amidoalkynyl complex 5 via a terminal N-heterocyclic vinylidene intermediate. This work showed that arenides can act as convenient redox-active ligands for implementing thorium-ligand cooperative multielectron transfer and that the reactivity can be tuned by the arenide binding mode.