New dimeric phosphine ylide copper (I) complexes: Synthesis, coordination behavior, and application in Suzuki cross-coupling reactions

The reaction of the non-symmetric phosphorus ylides, Ph2P(CH2)nPPh2C(H)C(O)PhR with CuCl in equimolar ratios using dry methanol as solvent give binuclear complexes of the type [Cu(μ-Cl){Ph2P(CH2)nPPh2C(H)C(O)PhR}]2 (n = 1: R = Br (1), OCH3 (2); n = 2: R = Br (3), OCH3 (4)). X-ray analyses of 1 demonstrate the Cl bridged dimeric structures with P,C-chelated ligands. Characterizations of these compounds were carried out by FT-IR and multinuclear NMR technique. Elemental analysis indicate a 1:1 stoichiometry between the ylides and the Cu(I) chloride in the four complexes. The precursor complexes 1 and 3 are found to exhibit high catalytic activity in the Cu-catalyzed Suzuki cross-coupling reactions in an air atmosphere at medium catalyst loading in DMF as a solvent. The use of 5 mol% catalyst in the presence of Cs2CO3 allows the coupling reaction to proceed with moderate to excellent yields.