Synthesis, structure, and reactivity of Pd complexes with mixed P,S-Bis(ylide), ylide-sulfide, and ylide-methanide ligands

Abstract

The coordination properties of the ylide-sulfonium salts [Ph 3P=C(H)COCH2S(R1)R2]X [R1 = R2 = Et, X = Br (2); R1 = Me, R2 = Ph, X = ClO4 (5)], the phosphonium-sulfide salt [Ph3PCH 2COCH2SEt]Br (3) and the neutral ylide-sulfide [Ph 3P=C(H)COCH2SPh] (4) towards PdII have been studied. Four different bonding modes have been characterized. The reactions of the ylide-sulfonium salts 2 and 5 with PdCl2(NCMe)2 and NEt3 afford the chelating bis(ylide) complexes cis-[PdCl 2{Ph3PC(H)COC(H)S(R1)R2-κC,C}] [R1 = R2 = Et (6); R1 = Me, R2 = Ph (7)], which are obtained selectively in the meso form (RS/SR). This bonding mode is characterized, including by X-ray crystallography, in the acetylacetonate (acac) complexes [Pd(acac-O,O′){Ph3PC(H)COC(H) S(R1)R2-κC,C}]ClO4 [R1 = R2 = Et (8); R1 = Me, R2 = Ph (9)], which were obtained by reaction of the respective precursor 6 or 7 with AgClO4 and Tl(acac). On the other hand, the C,S-chelating bonding mode has been characterized in [PdCl2{Ph3PC(H)COCH2SR- κC,S}] [R = Et (10); R = Ph (11)], obtained by reaction of the phosphonium-sulfide salt 3 with PdCl2(NCMe)2 and NEt 3 or by reaction of the ylide-sulfide 4 with PdCl2(NCMe) 2, respectively. Furthermore, the tridentate bonding mode μ-S:κC,C,S has been determined in the dinuclear derivative [PdCl{Ph3PC(H)COC(H)SPh-μ-S:κC,C,S}]2 (13), synthesized by reaction of the ylide-sulfide 4 with PdCl2(NCMe) 2 and NEt3. Compound 13 reacts with PPh3 to afford the κC,C-chelate [PdCl{Ph3PC(H)COC(H)SPh-κC,C} PPh3] (14) after cleavage of the sulfide bridge. Compound 14 was obtained as a single diastereoisomer, which was characterized as the D,L form (RR/SS). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.