Syntheses and molecular structures of ruthenium carbonyl complexes containing 1,2-naphthoquinone-1-oximate ligands

Abstract

The reaction of [Ru ₃ (CO) ₁₂ ] with 1-nitroso-2-naphthol (referred to as 1,2-naphthoquinone-1-oxime, Hnqo) in tetrahydrofuran (thf) at room temperature gave two isomeric mononuclear complexes, trans-[Ru{η ² -N(O)C ₁₀ H ₆ O} ₂ (CO) ₂ ] 1a and cis-[Ru{η ² -N(O)C ₁₀ H ₆ O} ₂ (CO) ₂ ] 1b. Compound 1b could be converted to 1a quantitatively in acidic media. Reaction of 1a with acetylpyridine in the presence of trimethylamine N-oxide afforded trans-[Ru{η ² -N(O)C ₁₀ H ₆ O} ₂ {NC ₅ H ₄ C(O)CH ₃ }(CO)] 2 in which one of the carbonyls was replaced by an acetylpyridine moiety. Similarly, complex 3, trans-[Ru{η ² -N(O)C ₁₀ H ₆ O} ₂ (NCMe)(CO)] was also obtained in high yield if acetonitrile was used instead of the acetylpyridine. When the reaction of [Ru ₃ (CO) ₁₂ ] and 1-nitroso-2-naphthol was carried out in refluxing thf for 1 h, two minor products [Ru ₃ (µ-η ³ -ONC ₁₀ H ₆ O) ₂ (CO) ₈ ] 4 and [Ru ₃ {µ-η ² -N(H)C ₁₀ H ₆ O}{µ-η ² -N(H)C ₁₀ H ₄ (O)NOC ₁₀ H ₆ }(CO) ₈ ] 5 were isolated in addition to 1a and 1b. Clusters 4 and 5 consisted of an open triruthenium metal core with the two nqo ligands (in 4) and two quinone–imine type ligands (in 5) bridging the open edge in a µ-η ³ and a µ-η ² -manner respectively.