Metal Vapour Synthesis of an Organometallic Barium(0) Synthon

A hydrocarbon‐soluble barium anthracene complex was prepared by means of metal vapour synthesis. Reaction of 9,10‐bis(trimethylsilyl)anthracene (Anth′′) with barium vapour gave deep purple Ba(Anth′′) which after extraction with diethyl ether crystallised as the cyclic octamer [Ba(Anth′′)⋅Et2O]8. Dissolution in benzene or toluene led to replacement of the Et2O ligand with a softer arene ligand and isolation of Ba(Anth′′)⋅arene. Diffusion ordered spectroscopy (DOSY NMR ) measurements in benzene‐d6 indicate solution species with a molecular weight that equals a trimeric constitution. Natural population analysis (NPA) assigned charges of +1.70 and −1.70 to Ba and Anth′′, respectively, relating to highly ionic Ba2+/Anth′′2− bonding. Preliminary reactivity studies with air, Ph2C=NPh, or H2 show that the complex reacts as a Ba0 synthon by release of neutral Anth′′. This soluble molecular Ba0/BaII redox synthon provides new routes for the syntheses of barium complexes under mild conditions. For over half a century, Mg(anthracene) has been a well‐known complex that reacts as a form of “atomic” Mg0, however, heavier alkaline‐earth metal anthracene complexes are unknown. Reaction of Ba0 vapour with an anthracene ligand gave a Ba anthracene complex that crystallizes as a cyclic octamer and reacts as a Ba0 synthon.