η-Coordinated ruthenabenzenes from three-component assembly on a diruthenium μ-allenyl scaffold

• Published in: Dalton transactions : an international journal of inorganic chemistry 2022-05, Vol.51 (21), p.839-84
• Main Authors: Bresciani, Giulio, Zacchini, Stefano, Pampaloni, Guido, Bortoluzzi, Marco, Marchetti, Fabio
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d2dt01071b

The room temperature reactions with internal alkynes, RC&z.tbd;CR, of the μ-allenyl acetonitrile complex [Ru 2 Cp 2 (CO) 2 (NCMe){μ-η 1 :η 2 -C 1 H&z.dbd;C 2 &z.dbd;C 3 Me 2 }]BF 4 ( 1-NCMe ), freshly prepared from the tricarbonyl precursor [Ru 2 Cp 2 (CO) 3 {μ-η 1 :η 2 -C 1 H&z.dbd;C 2 &z.dbd;C 3 Me 2 }]BF 4 , 1 , proceeded with alkyne insertion into ruthenium-allenyl bond and allenyl-CO coupling, affording compounds [Ru 2 Cp 2 (CO) 2 {μ-η 2 :η 5 -C(R)C(R)C 1 HC 2 (C 3 Me&z.dbd;CH 2 )C(OH)}]BF 4 (R = Ph, 2 ; R = CO 2 Me, 3 ; R = CO 2 Et, 4 ) in 83-94% yields. Deprotonation of 2-4 by triethylamine gave [Ru 2 Cp 2 (CO) 2 {μ-η 2 :η 5 -C(R)C(R)CHC(CMe&z.dbd;CH 2 )C(O)}] (R = Ph, 5 ; R = CO 2 Me, 6 ; R = CO 2 Et, 7 ) in 75-88% yields, and 2-4 could be recovered upon HBF 4 ·Et 2 O 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. A series of three ruthenabenzenes acting as hetero-arene ligands towards a second Ru centre was synthesized from a dimetallic precursor via double C-C bond coupling between allenyl, carbon monoxide and alkyne units.