Dinuclear indium and thallium diyls: biscarbenoids or metal cluster?

Using bis(beta-diketiminate) ligands we were able to synthesize unprecedented indium and thallium biscarbenoids. For indium, a novel four-membered metallacycle is derived from intra-and intermolecular In-In interactions in the solid state, while for thallium only an intramolecular Tl-2-pseudo-dimer is obtained. Computational studies revealed that the solid-state structures benefit significantly from dispersion stabilization.