Palladium complexes phenylpalladium

A phenylpalladium complex also causes ring-opening rearrangement of methylenecyclobutane to a ji-allylpalladium complex, which arises from p-carbon elimination of an intermediate (cyclobutylmethyl)palladium complex [82]. 

We do not know if the vinylic alcohol is actually an intermediate or whether a hydride-71 complex of it rearranges directly to the aldehyde as probably happens in the palladium-catalyzed oxidation of ethylene to acetaldehyde. The formation of 4% 2-methyl-2-phenylpropanal is unexpected. This product must arise from a reversed addition of the phenylpalladium group followed by a hydrogen transfer from the hydroxyl-bearing carbon to the palladium, followed by reductive elimination of a hydridopalladium group. An alkyoxypalladium intermediate has been proposed (39). 

The reaction can be explained by the transmetalation of the borate with PdCl2 giving phenylpalladium intermediate and the subsequent insertion of a C=C double bond of norbornadiene into the Pd-Ph bond. Cationic 7t-allyl-palladium(II) and -rhodium(I) complexes having a BPhJ counter anion induce phenyl group migration from B to the transition metals at elevated temperature to form phenyl complexes [54,55] (Eq. 5.17). 

The reaction of norbornene with iodobenzene or bromobenzene in the presence of [Pd(PPh3)4] as the catalyst leads to pentacycle 83 (Scheme 11.29) [6, 31, 90-94], This process is known as the Catellani reaction. The parent transformation involves an insertion of the phenylpalladium(II) complex into the double bond of norbornene to give (Ti -phenyl)norbornyl palladium(II) complex 84, which then undergoes intramolecular paUadation to form 85. Further reaction of this paUadacycle with iodobenzene leads to 83. Biphenyl, tetracycle 86, and more complex derivatives 87 and 88, have also been isolated in this reaction [90, 93c, 94], Benzocyclobutenes... 

Transfer of aryl groups to palladium(ii) centers with the formation of arylpalladium(iv) complexes has been established.The first identified transfer of Ph from diphenyliodonium(iii) triflate (Scheme 26) to the metallacyclic complex [Pd(C4H8)(bpy)] led to the formation of a new phenylpalladium(iv) bond, providing easy access to species such as [Pd(OTf)G4H8(Ph)(bpy)] 163. This elegant procedure features a model reaction for suggested reactions of C(i/) )-X bonds with Pd(ii) substrates. " "" ... 

Treatment of the Pd(PPF-f-Bu)[P(o-tol)3] 30 with phenyl tosylate in benzene at room temperature formed the resulting phenylpalladium(II) tosylate complex 32 in good yields via an initial dissociation of the P(o-tol)3 ligand creating the more reactive bisphoshine palladium(O) species. The palladium(II) complex, holding the phenyl group cis to the less sterical hindered phosphino group, was produced as the... 

Even though an interchanged phenylpalladium(II) tosylate complex was obtained, the 1,2-migration proved to be very fast even at room temperature complementing the 1,2-migration from tricoordinated T-shaped palladium(II) complexes observed in the Heck reaction (Chap. 2). 

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