Osmium(IV) Tetraaryl Complexes Formed from Prefunctionalized Ligands

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High Resolution Image Download MS PowerPoint Slide Transition metal(IV) tetraaryl, M(aryl) 4, complexes hold great promise as functional building blocks for complex organometallic materials, yet their widespread utility depends on the development of improved synthetic protocols and a deeper understanding of their chemical structure–property relationship(s). Here we show that Os(aryl) 4 complexes with preinstalled functional groups (–F, –Cl, –Br, –I, and –SMe) can be prepared from reactions between (Oct 4 N) 2 [OsBr 6 ] and Grignard reagents formed by halogen/magnesium insertion or exchange. This approach provides access to compounds that may otherwise prove challenging to prepare through postfunctionalization strategies, such as those comprising halogens in the 2- or 5-positions. We characterize these, as well as previously reported, materials using single-crystal X-ray diffraction, solution voltammetry, and UV–vis spectroscopy. Through a comparison of 13 differently substituted complexes, we identify correlations between their electrochemical and optical gaps, and between the E 1/2 of their 0/1+ redox event and an adjusted Hammett parameter that accounts for all aryl ligand substituents. The electronic property trends observed are further rationalized through a series of first-principles calculations based on density functional theory. Together, this work lays a foundation for advancing new preparative methods to further derivatize such species, and a robust experimental data set to help benchmark future experimental and computational compound characterization.