Fast and scalable solvent-free access to Lappert's heavier tetrylenes E{N(SiMe3)2}2 (E = Ge, Sn, Pb) and ECl{N(SiMe3)2} (E = Ge, Sn)

Solid-state mechanochemistry for the rapid and efficient synthesis of tris-cyclometalated iridium(iii) complexes

Tris-cyclometalated iridium(iii) complexes have received widespread attention as attractive prospective materials for e.g., organic light-emitting diodes (OLEDs), photoredox catalysts, and bioimaging probes. However, their preparation usually requires prolonged reaction times, significant amounts of high-boiling solvents, multistep synthesis, and inert-gas-line techniques. Unfortunately, these requirements represent major drawbacks from both a production-cost and an environmental perspective. Herein, we show that a two-step mechanochemical protocol using ball milling enables the rapid and efficient synthesis of various tris-cyclometalated iridium(iii) complexes from relatively cheap iridium(iii) chloride hydrate without the use of significant amounts of organic solvent in air. Notably, a direct one-pot procedure is also demonstrated. The present solid-state approach can be expected to inspire the development of cost-effective and timely production methods for these valuable iridium-based complexes, as well as the discovery of new phosphorescent materials, sensors, and catalysts.

Synthesis without solvent: consequences for mechanochemical reactivity

Solvents are so nearly omnipresent in synthetic chemistry that a classic question for their use has been: "What is the best solvent for this reaction?" The increasing use of mechanochemical approaches to synthesis-by grinding, milling, extrusion, or other means-and usually with no, or only limited, amounts of solvent, has raised an alternative question for the synthetic chemist: "What happens if there is no solvent?" This review focuses on a three-part answer to that question: when there is little change ("solvent-optional" reactions); when solvent needs to be present in some form, even if only in the amounts provided by liquid-assisted (LAG) or solvate-assisted grinding; and those cases in which mechanochemistry allows access to compounds that cannot be obtained from solution-based routes. The emphasis here is on inorganic and organometallic systems, including selected examples of mechanosynthesis and mechanocatalysis. Issues of mechanochemical depictions and the adequacy of LAG descriptions are also reviewed.