Synthesis, structure, and reactivity of the methoxy-bridged dimer [Cp∧Ru(μ-OMe)]2 (Cp∧ = η5-1-methoxy-2,4-di-tert-butyl-3-neopentylcyclopentadienyl)

The methoxy-bridged Ru-II complex [Cp boolean AND Ru(mu-OMe)](2) (CP boolean AND = eta(5)-1-methoxy-2,4-di-tert-butyl-3-neopentylcyclopentadienyl) was obtained from the Ru-III complex [Cp boolean AND RuCl(mu-Cl)](2) by reaction with K2CO3 in methanol. In the presence of EtOH, the complex was converted into the ethoxy-bridged dimer [Cp boolean AND Ru(mu-OEt)](2). Due to the steric demand of the Cp boolean AND pi-ligand, complex [Cp boolean AND Ru(mu-OMe)](2) behaves differently than the parent complex [Cp*Ru(mu-OMe)](2). Reaction with Me3SiCl in the presence of LiCl gave the electronically unsaturated complex [Cp boolean AND Ru(mu-Cl)](2), whereas a tetrameric structure had been reported for the analogous Cp* complex. In contrast to the expected addition reaction, a monomeric complex [Cp boolean AND Ru(CO)(2)(CO2Me)] was obtained by ligand insertion of CO in the Ru-OMe bond. Moreover, an unprecedented transformation of cyclooctadiene into ethylbenzene in the coordination sphere of Ru was observed. Complex [Cp boolean AND Ru(mu-OMe)](2) was found to act as a highly active catalyst for atom transfer radical cyclization (ATRC) reactions on a diverse range of substrates such as N-substituted dichloro-and trichloroacetamides, enamides, ethers, and esters.