Oxidative Addition of a Hypervalent Transannular Sulfur–Sulfur Bond to a Pd(0) Complex: Synthesis and Crystal Structures of 1,5-Dithiacyclooctanepalladium(II) Bis(trifluoromethanesulfonate) Having Phosphine Ligands

Abstract

Abstract A hypervalent compound 1,5-bis(trifluoromethylsulfonyloxy)-1λ4,5λ4-dithiabicyclo[3.3.0]octane (1) oxidatively reacted with Pd2(dba)3 (dba = dibenzylidene acetone) in acetonitrile to give a dicationic complex [Pd(dtco)(CH3CN)2](OTf)2 (2) (DTCO = 1,5-dithiacyclooctane), in which the DTCO ligand coordinated in cis-chelation to the palladium metal. Acetonitrile in 2 was labile enough to be readily replaced by phosphine ligands to give dicationic DTCO-phosphine palladium complexes of the formula [Pd(dtco)(L)2](OTf)2 (3: L = PMe2Ph; 4: L = PPh3; 5: L2 = 1,2-bis(diphenylphosphino)ethane; 6: L2 = (R)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl). Molecular structures of 5 and 6 have been characterized by X-ray analysis, indicating that each of these two complexes consists of a discrete dicationic palladium(II) species [Pd(dtco)L2]2+ and two trifluoromethanesulfonate ions without any cation–anion bonding interaction, and revealing that the DTCO is coordinated to the palladium center as a bidentate ligand and that two phosphorus atoms ultimately coordinated to the metal in cis-fashion.