SCHEDULED MAINTENANCE
η6-Coordinated ruthenabenzenes from three-component assembly on a diruthenium μ-allenyl scaffold†
Abstract
The room temperature reactions with internal alkynes, RC![[triple bond, length as m-dash]](https://www.rsc.org/images/entities/char_e002.gif)
CR, of the μ-allenyl acetonitrile complex [Ru2Cp2(CO)2(NCMe){μ–η1:η2-C1H![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
C2C3Me2}]BF4 (1-NCMe), freshly prepared from the tricarbonyl precursor [Ru2Cp2(CO)3{μ–η1:η2-C1HC2C3Me2}]BF4, 1, proceeded with alkyne insertion into ruthenium-allenyl bond and allenyl-CO coupling, affording compounds [Ru2Cp2(CO)2{μ–η2:η5-C(R)C(R)C1HC2(C3MeCH2)C(OH)}]BF4 (R = Ph, 2; R = CO2Me, 3; R = CO2Et, 4) in 83–94% yields. Deprotonation of 2–4 by triethylamine gave [Ru2Cp2(CO)2{μ–η2:η5-C(R)C(R)CHC(CMeCH2)C(O)}] (R = Ph, 5; R = CO2Me, 6; R = CO2Et, 7) in 75–88% yields, and 2–4 could be recovered upon HBF4·Et2O addition to 5–7. All the products, 2–7, were fully characterized by elemental analysis, IR and multinuclear NMR spectroscopy. The structure of 2 was ascertained by single crystal X-ray diffraction and investigated by DFT calculations, revealing a six-membered ruthenacycle with Shannon aromaticity index in line with related compounds. The formation of ruthenium-coordinated ruthenabenzenes from a preexistent diruthenium scaffold is a versatile but underdeveloped approach exploiting cooperative effects typical of a dimetallic core.
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