Chalcogen-Dependent Palladation at the Benzyl Carbon of 2,3-Bis[(phenylchalcogeno)methyl]quinoxaline: Palladium Complexes Catalyzing Suzuki–Miyaura Coupling via Palladium–Chalcogen Nanoparticles

The reaction of PhS–/PhSe– with 2,3-bis(bromomethyl)quinoxaline has resulted in 2,3-bis[(phenyl-thio/-seleno)methyl]quinoxaline (L1/L2). They react with Na2PdCl4, resulting in [Pd2(L1–H)2Cl2] (1)/[PdL2Cl2] (2). External base-free activation of the benzyl group’s C(sp3)–H results in palladation of L1, forming palladacycle 1, whereas L2 forms a seven-membered chelate ring with Pd(II), resulting in 2. L1, L2, 1, and 2 have been characterized by IR, multinuclear NMR, mass spectrometry, and single-crystal X-ray diffraction. In the case of 1 bond lengths (A) are Pd–C = 2.001(9), Pd–N = 2.048(8), and Pd–S = 2.259(2) A. The Pd–Se bond length in complex 2 is 2.3924(15)–2.3991(15) A. Complexes 1/2 were explored in the catalyzed Suzuki–Miyaura coupling reactions of several aryl bromides (including deactivated ones). The palladacycle 1 shows better catalytic efficiency than complex 2, as its lower reaction time and catalyst loading (up to 0.006 mol %) are sufficient for significantly good conversions. The catalysis a...