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 Th IV . Here we report two unique examples of thorium arenide complexes prepared by reduction of a Th IV -siloxide complex in presence of naphthalene, the mononuclear arenide complex [K(OSi(O t Bu) 3 ) 3 Th(η 6 -C 10 H 8 )] (1) and the inverse-sandwich complex [K(OSi(O t Bu) 3 ) 3 Th] 2 (μ-η 6 ,η 6 -C 10 H 8 )] (2). The electrons stored in these complexes allow the reduction of a broad range of substrates (N 2 O, AdN 3 , CO 2 , HBBN). Higher reactivity was found for the complex 1 which reacts with the diazoolefin IDipp=CN 2 to yield the unexpected Th IV 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.