Dialkylamino cyclopentadienyl ruthenium(ii) complex-catalyzed α-alkylation of arylacetonitriles with primary alcohols

Abstract

Aminocyclopentadienyl ruthenium complexes, [(η⁵-C₅H₄NMe₂)Ru(PPh₃)₂(CH₃CN)]⁺BF₄⁻ and [(η⁵-C₅H₄NEt₂)Ru(PPh₃)₂(CH₃CN)]⁺BF₄⁻, are moderately active catalysts for α-alkylation of arylacetonitriles with primary alcohols; on the other hand, the analogous unsubstituted cyclopentadienyl ruthenium complex [(η⁵-C₅H₅)Ru(PPh₃)₂(CH₃CN)]⁺BF₄⁻ shows very low catalytic activity. On the basis of experimental results and theoretical calculations, rationalization for the much higher catalytic activity of the aminocyclopentadienyl complexes over that of the unsubstituted Cp complex is provided. In the catalytic systems with the former, it is possible to regenerate the active solvento complexes via protonation of the metal hydride intermediates and subsequent ligand substitution; this process is, however, very nonfacile in the catalytic system with the latter.