Synthesis, Structure, and Reactivity of the Methoxy-Bridged Dimer [Cp^∧Ru(μ-OMe)]₂ (Cp^∧ = η⁵-1-Methoxy-2,4-di<i>-tert</i>-butyl-3-neopentylcyclopentadienyl)

Abstract

The methoxy-bridged Ru II complex [Cp ∧ Ru(μ-OMe)] 2 (Cp ∧ = η 5 -1-methoxy-2,4-di- tert -butyl-3-neopentylcyclopentadienyl) was obtained from the Ru III complex [Cp ∧ RuCl(μ-Cl)] 2 by reaction with K 2 CO 3 in methanol. In the presence of EtOH, the complex was converted into the ethoxy-bridged dimer [Cp ∧ Ru(μ-OEt)] 2 . Due to the steric demand of the Cp ∧ π-ligand, complex [Cp ∧ Ru(μ-OMe)] 2 behaves differently than the parent complex [Cp*Ru(μ-OMe)] 2 . Reaction with Me 3 SiCl in the presence of LiCl gave the electronically unsaturated complex [Cp ∧ Ru(μ-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 ∧ Ru(CO) 2 (CO 2 Me)] 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 ∧ Ru(μ-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.