Insertion of alkenyl sulfides into a palladium-aryl bond .2. Stabilization of sigma-yl-kS chelates and decomposition reactions through C-S cleavage

The reaction of [Pd(C6F5)Br(NCMe)(2)] with the allylic sulfides R(1)SCH(2)CH=CH2(R(1) = -CH2- CH=CH2, Me), n-BuSCHMeCH-CH2, and n-BuSCH(2)CH=CHMe results in insertion at the double bond into the Pd-C6F5; bond and B-SR elimination (C-S cleavage) to give the corresponding (pentafluorophenyl)alkenes and a palladium thiolate. With alkenyl sulfides of longer carbon chains RS(CH2)(n)CH=CH2(R = n-Bu, Ph; n = 2, 3) five-membered (n = 2, 13, 14) or six-membered (n = 3, 16, 17) sigma-yl-KS-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 [(sigma-KS-(Rthio)alkyl)Pd(acac)](13b, 14b, 18b, 19b). Delta G(Tc)(double dagger) values show that the S-inversion is easier for the Ph-substituted than for the n-Bu-substituted complexes. The decomposition of the (sigma-yl-KS palladacycles occurs through Pd-migration and, when Pd and S are placed three bonds apart in the chain, beta-SR, elimination; this is the same process observed in the reaction of [Pd(C6F5)Br(NCMe)(2)] with allylic sulfides. Double bond isomerization of the (pentaflurophenyl))alkene products formed in the decomposition reactions is observed, catalysed by ''Pd-H'' intermediates. Double pentafluorophenyl arylation is also observed in some cases.