Synthesis and Systematic Structural Analysis of Cationic Half‐Sandwich Ruthenium Chalcogenocarbonyl Complexes

Although the chemistry of transition‐metal complexes with carbonyl (CO) and thiocarbonyl (CS) ligands has been well developed, their heavier analogues, namely selenocarbonyl (CSe) and tellurocarbonyl (CTe) complexes remain scarce. The limited availability of such CSe and CTe complexes has so far hampered our understanding of the differences between such chalcogenocarbonyl (CE: E=O, S, Se, Te) ligands. Herein, we report the synthesis and properties of a series of cationic half‐sandwich ruthenium CE complexes of the type [CpRu(CE)(H2IMes)(CNCH2Ts)][BArF4] (Cp=η5‐C5H5−; H2IMes=1,3‐dimesitylimidazolin‐2‐ylidene; ArF=3,5‐(CF3)2C6H3). A combination of X‐ray diffraction analyses, NMR spectroscopic analyses, and DFT calculations revealed an increasing π‐accepting ability of the CE ligands in the order O