Recent Advances in Synthesis of Molecular Heteroleptic Osmium and Iridium Phosphorescent Emitters

The application of new procedures of organometallic synthesis based on alternative starting complexes has given rise to a significant enhancement in the preparation of osmium(IV), osmium(II), and iridium(III) emitters, since 2012. The choice of the precursors should be done taking into account its ligands, since they may cooperate in the emitter synthesis. Three different functions are clearly pointed out in the revised procedures: the ligands of the starting compounds can direct the selectivity of competitive ruptures of sigma-bonds of the chromophores, without having direct participation in the activation; on the contrary, they can directly participate in the generation of a ligand, being a part of the new coordinated group; and the ligands can also act as internal base in sigma-bond heterolytic activation reactions. In addition, the ability of the polyhydrides OsH6((PPr3)-Pr-i)(2) and IrH5((PPr3)-Pr-i)(2) to activate C-H bonds is pointed out as one of the determining factors of the success in many cases.

Automated summary

The application of new procedures in organometallic synthesis using alternative starting complexes has significantly enhanced the preparation of osmium(IV), osmium(II), and iridium(III) emitters since 2012. The choice of precursors should consider the ligands, as they play a role in emitter synthesis. Three different functions of ligands in the revised procedures have been identified, including directing selectivity in sigma-bond ruptures, participating in new coordinated groups, and acting as internal bases in activation reactions. Additionally, the ability of polyhydrides OsH6((PPr3)-Pr-i)(2) and IrH5((PPr3)-Pr-i)(2) to activate C-H bonds is highlighted as a key factor in the success of many cases.