Kinetic studies, alkyl electrophile oxidative

Kinetics studies of the oxidative addition of a variety of unactivated primary alkyl electrophiles to several PdL2 complexes (L=trialkylphosphine) have been described [46]. For the reaction depicted in Eq. 17, the activation parameters are AU =20.8 kcal mol" (20 °C) AH =2A kcal mol" AS =-63 eu. The large negative AS" value that is observed is consistent with an associative pathway for oxidative addition. The rate of addition increases as the solvent polarity increases, as would be expected for the postulated 8 2 mechanism, and is not affected by added P(f-Bu)2Me, indicating that the alkyl bromide oxidatively adds to PdL2 (not PdLi or PdL3) [47]. 

The anodic oxidation of benzene produces a mixture of polyphenylene compounds. This oligomerization can be performed in acetonitrile [21] or in liquid sulfur dioxide [22]. Mixed coupling between naphthalene and alkyl benzenes has also been demonstrated (Table 1, numbers 12-16). The relative yield of mixed coupling products increases with the basicity of the alkyl benzene with mesitylene 19%, with tetramethylbenzene 42%, and with pentamethylbenzene 64% of mixed coupling products are obtained. This suggests an electrophilic reaction between naphthalene cation radicals and alkylbenzenes. The mixed coupling reaction of phenanthrene with anisole has been studied kinetically. The results indicate that initially a complex PA is formed between the phenanthrene radical cation and anisole, followed by an electron transfer from the complex. The resulting PA" -anisole complex then decomposes to the product [23]. 

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