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)

Abstract

The methoxy-bridged RuII complex [Cp∧Ru(μ-OMe)]2 (Cp∧ = η5-1-methoxy-2,4-di-tert-butyl-3-neopentylcyclopentadienyl) was obtained from the RuIII complex [Cp∧RuCl(μ-Cl)]2 by reaction with K2CO3 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 Me3SiCl 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(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∧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.