A new Pd(II) complex of a sulfur ylide; Synthesis, X-ray characterization, theoretical study and catalytic activity toward the Suzuki-Miyaura reaction

The new sulfonium salt [SMe2CH2C(O)C6H4-m-OCH3]Br (1) was synthesized from the reaction of dimethyl sulfide and 2-bromo-3'-methoxyacetophenone. Further treatment with NaOH 10% gave the alpha-keto stabilized sulfur ylide SMe2C(H)C(O)C6H4-m-OCH3 (2). This ligand was reacted with the dichloro(1,5-cyclooctadiene)palladium(II) complex, [PdCl2(cod)1, in a 2:1 ratio to give the new C alpha-cobrdinated complexes cis- and trans-[PdCl2(SMe2C(H)C(O)C6H4-m-OCH3)(2)] (3a and 3b). Characterization of the obtained compounds was performed by elemental analysis, IR, H-1, C-13 NMR and mass spectroscopies. Since complexes 3a and 3b were insoluble in most organic solvents, we chose DMSO as a suitable solvent for the NMR spectroscopies. Crystallization of above solution led to the formation of single crystals. The X-ray analysis results revealed that complex 3a has undergone a ligand replacement reaction and the complex [PdCl2(SMe2C(H)C(O)C6H4-m-OCH3)center dot DMSO] (4) was formed. This complex has two Cl atoms in cis positions, one sulfur ylide and one S-coordinated DMSO as ligands. The air/moisture stable complexes 3a and 3b were employed as efficient catalysts for the Suzuki-Miyaura cross-coupling reaction of several aryl halides. The coupled products of these reactions were obtained in good to excellent yields and purity, with short reaction times and low catalyst loading. Also a theoretical study on the structure and nature of the Pd-C bond in complex 4 is reported here at the BP86/clef2-SVP level of theory. (C) 2016 Elsevier Ltd. All rights reserved.