C–C coupling formation using nitron complexes

Abstract

A series of Ru^II (1), Rh^III (2), Ir^III (3, 4), Ir^I (5) and Pd^II (6–9) complexes of the ‘instant carbene’ nitron were prepared and characterized by ¹H- and ¹³C-NMR, FT-IR and elemental analysis. The molecular structures of complexes 1–4 and 6 were determined by X-ray diffraction studies. The catalytic activity of the complexes (1–9) was evaluated in alpha(α)-alkylation reactions of ketones with alcohol via the borrowing hydrogen strategy under mild conditions. These complexes were able to perform this catalytic transformation in a short time with low catalyst and base amounts under an air atmosphere. Also, the Pd^II–nitron complexes (6–9) were applied in the Suzuki–Miyaura C–C coupling reaction and these complexes successfully initiated this reaction in a short time (30 minutes) using the H₂O/2-propanol (1.5 : 0.5) solvent system. The DFT calculations revealed that the Pd^0/II/0 pathway was more preferable for the mechanism.