Zerovalent Rh and Ir Silatranes Featuring 2‐center, 3‐electron Polar Sigma Bonds

Species with 2‐center, 3‐electron (2c/3e‐) σ‐bonds are of interest owing to their fascinating electronic structures and potential for interesting reactivity patterns. Herein we report the synthesis and characterization of a pair of zerovalent (d9) trigonal pyramidal Rh and Ir complexes that feature 2c/3e‐ σ‐bonds to the Si atom of a tripodal tris(phosphine)silatrane ligand. X‐ray diffraction, continuous wave and pulse electron paramagnetic resonance, density functional theory calculations, and reactivity studies have been used to characterize these electronically distinctive compounds. The data available highlight a 2c/3e‐ bonding framework with a σ*‐SOMO of metal 4‐ or 5dz2 parentage that is partially stabilized by significant mixing with Si (3pz) and metal (5‐ or 6pz) orbitals. Metal‐ligand covalency thus buffers the expected destabilization of transition metal (TM)‐silyl σ*‐orbitals via d–p mixing, affording well‐characterized examples of TM‐to‐main group, and hence polar, 2c/3e‐ σ "half‐bonds".

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