: Dimetallic complexes are suitable platforms for the assembly of small molecular units, and the reactivity of bridging alkenyl ligands has been widely investigated to model C-C bond forming processes. Here, we report the unusual coupling of an alkenyl ligand, bridging coordinated on a diruthenium scaffold, with a series of alkynes, revealing two possible outcomes. The diruthenium complex [Ru2Cp2(Cl)(CO)(μ-CO){μ-η1:η2-C(Ph)CH(Ph)}], 2, was prepared in two steps from [Ru2Cp2(CO)2(μ-CO){μ-η1:η2-C(Ph)CH(Ph)}]BF4, [1]BF4, in 69% yield. Then, the reaction of 2 with C2(CO2Me)2, promoted by AgCF3SO3 in dichloromethane, afforded in 51% yield the complex [Ru2Cp2(CO)2{μ-η3:η2-C(Ph)CH(Ph)C(CO2Me)C(CO2Me)}]CF3SO3, [3]CF3SO3, containing a ruthenacyclopentene-based hydrocarbyl ligand. On the other hand, 2 reacted with other alkynes and AgX salts to give the butadienyl complexes [Ru2Cp2(CO)2{μ-η3:η2-C(R)CH(R')C(Ph)C(Ph)}]X (R = R' = H, [4]BF4; R = R' = Me, [5]CF3SO3; R = R' = Ph, [6]CF3SO3; R = Ph, R' = H, [7]CF3SO3), in 42-56% yields. All products were characterized by IR and NMR spectroscopy, and by single crystal X-ray diffraction in the cases of 2, [3]CF3SO3 and [6]BF4. DFT calculations highlighted the higher stability of [4-7]+-like structures with respect to the corresponding [3]+-like isomers. It is presumable that [3]+-like isomers initially form as kinetic intermediates, then undergo H-migration which is disfavoured in the presence of carboxylato substituents on the alkyne. Such hypothesis was supported by the computational optimization of the transition states for H-migration in the cases of R = R' = H and R = R' = CO2Me.

Alkyne-alkenyl coupling at a diruthenium complex

Bresciani, Giulio;Pampaloni, Guido;Marchetti, Fabio
2022-01-01

Abstract

: Dimetallic complexes are suitable platforms for the assembly of small molecular units, and the reactivity of bridging alkenyl ligands has been widely investigated to model C-C bond forming processes. Here, we report the unusual coupling of an alkenyl ligand, bridging coordinated on a diruthenium scaffold, with a series of alkynes, revealing two possible outcomes. The diruthenium complex [Ru2Cp2(Cl)(CO)(μ-CO){μ-η1:η2-C(Ph)CH(Ph)}], 2, was prepared in two steps from [Ru2Cp2(CO)2(μ-CO){μ-η1:η2-C(Ph)CH(Ph)}]BF4, [1]BF4, in 69% yield. Then, the reaction of 2 with C2(CO2Me)2, promoted by AgCF3SO3 in dichloromethane, afforded in 51% yield the complex [Ru2Cp2(CO)2{μ-η3:η2-C(Ph)CH(Ph)C(CO2Me)C(CO2Me)}]CF3SO3, [3]CF3SO3, containing a ruthenacyclopentene-based hydrocarbyl ligand. On the other hand, 2 reacted with other alkynes and AgX salts to give the butadienyl complexes [Ru2Cp2(CO)2{μ-η3:η2-C(R)CH(R')C(Ph)C(Ph)}]X (R = R' = H, [4]BF4; R = R' = Me, [5]CF3SO3; R = R' = Ph, [6]CF3SO3; R = Ph, R' = H, [7]CF3SO3), in 42-56% yields. All products were characterized by IR and NMR spectroscopy, and by single crystal X-ray diffraction in the cases of 2, [3]CF3SO3 and [6]BF4. DFT calculations highlighted the higher stability of [4-7]+-like structures with respect to the corresponding [3]+-like isomers. It is presumable that [3]+-like isomers initially form as kinetic intermediates, then undergo H-migration which is disfavoured in the presence of carboxylato substituents on the alkyne. Such hypothesis was supported by the computational optimization of the transition states for H-migration in the cases of R = R' = H and R = R' = CO2Me.
2022
Bresciani, Giulio; Boni, Serena; Zacchini, Stefano; Pampaloni, Guido; Bortoluzzi, Marco; Marchetti, Fabio
File in questo prodotto:
File Dimensione Formato  
219.pdf

accesso aperto

Tipologia: Documento in Pre-print
Licenza: Creative commons
Dimensione 640.96 kB
Formato Adobe PDF
640.96 kB Adobe PDF Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/1167027
Citazioni
  • ???jsp.display-item.citation.pmc??? 3
  • Scopus 10
  • ???jsp.display-item.citation.isi??? 10
social impact