Synthesis of a Stable N‐Hetero ‐ Rh I ‐Metallacyclic Silanone

Abstract A novel N‐hetero‐Rh I ‐metallacyclic silanone 2 has been synthesized. The silanone 2 , showing an extremely large dimerization energy (Δ G =+86.2 kcal mol −1 ), displays considerable stability and persists in solution up to 60 °C. Above 120 °C, an intramolecular C sp3 −H insertion occurs slowly over a period of two weeks leading to the bicyclic silanol 5 . The exceptional stability of 2 , related to the unusual electronic and steric effects of Rh I ‐substituent, should allow for a more profound study and understanding of these new species. Furthermore, the metallacyclic silanone 2 presents two reactive centers (Si=O and Rh), which can be involved depending upon the nature of reagents. Of particular interest, the reaction with H 2 starts with the hydrogenation of Rh I center leading to the corresponding Rh III ‐dihydride complex 7 and it undergoes a cis / trans ‐isomerization via a particular mechanism, demonstrating that addition‐elimination processes can also happen for silanones just like for their carbon analogues!