Different bonding modes of sulfur bis-ylides in Pd complexes: Crystal structure of [Pd(μ-OAc){μ-[CH(SMe2)]2C(O)}(acac-O,O′)2]ClO4

The reaction of [Me2SCH2C(O)CH2SMe2]Br2 (1) with Pd(OAc)2 gives the mononuclear neutral complex cis-[PdBr2{η2-[CH(SMe2)]2C(O)}] (2) through double deprotonation of the bis-sulfonium salt. The sulfur bis-ylide coordinates in (2) as a C,C′-chelating ligand, and is obtained as a single diastereoisomer (meso form, RS/SR), in spite of the presence of two stereogenic ylidic centers. Reaction of (2) with AgClO4 and Tlacac gives [Pd(acac-O,O′){η2-[CH(SMe2)]2C(O)}]ClO4 (3), which shows the same bonding mode for the bis-ylide ligand. However, (2) reacts with Pd(OAc)2, AgClO4 and Tlacac to give the dinuclear [Pd(μ-OAc){μ-[CH(SMe2)]2C(O)}(acac-O,O′)2]ClO4 (4) as two different isomers. In complex (4) the bis-ylide bridges two palladium atoms and the presence of two isomers arise from the relative arrangement of the bis-ylide with respect to the acetate ligand. The X-ray crystal structure of (4) has been determined.