Insertion of Alkenyl Sulfides into a Palladium−Aryl Bond. 2. Stabilization of σ-yl-κS Chelates and Decomposition Reactions through C−S Cleavage

The reaction of [Pd(C 6 F 5 )Br(NCMe) 2 ] with the allylic sulfides R 1 SCH 2 CH CH 2 (R 1 = −CH 2 CH CH 2, Me), n -BuSCHMeCH CH 2, and n -BuSCH 2 CH CHMe results in insertion of the double bond into the Pd−C 6 F 5 bond and β-SR elimination (C−S cleavage) to give the corresponding (pentafluorophenyl)alkenes and a palladium thiolate. With alkenyl sulfides of longer carbon chains RS(CH 2 ) n CH CH 2 (R = n -Bu, Ph; n = 2, 3) five-membered ( n = 2, 13, 14 ) or six-membered ( n = 3, 16, 17 ) σ-yl-κ S -palladacycles were obtained. The six-membered derivatives isomerize to the corresponding five-membered palladacycles ( 18, 19 ) by one-step Pd-migration (Pd−H elimination−readdition). Inversion of the coordinated sulfur is observed in these derivatives, and the dynamic process has been studied for the monomeric complexes [(σ-κ S -(Rthio)alkyl)Pd(acac)] ( 13b, 14b, 18b, 19b ). Δ G ⧧ Tc values show that the S-inversion is easier for the Ph-substituted than for the n -Bu-substituted complexes. The decomposition of the σ-yl-κ S palladacycles occurs through Pd-migration and, when Pd and S are placed three bonds apart in the chain, β-SR elimination; this is the same process observed in the reaction of [Pd(C 6 F 5 )Br(NCMe) 2 ] with allylic sulfides. Double bond isomerization of the (pentaflurophenyl)alkene products formed in the decomposition reactions is observed, catalyzed by “Pd−H” intermediates. Double pentafluorophenyl arylation is also observed in some cases.