Ion pairs as nucleophiles

The effect of the nature of ion pairs as nucleophiles in a metal-catalysed substitution reaction has been investigated by determining product ratios for the Pd-catalysed allylic alkylations of substrates (9)-(ll) under various conditions, particularly with respect to catalyst ligands, nucleophiles, and counterions. Each dienyl acetate ionizes to form initially the vinyl (7r-allyl)-Pd intermediate corresponding most closely to the leaving group, i.e. (12) from (9), (13) from (11), but (12) and (13) from (10). The initial intermediate can then either be trapped by the nucleophile or it can begin to equilibrate to some mixture of vinyl 7r-allyl intermediates. If nucleophilic addition occurs before full equilibration, the product ratio is different for each substrate if... 

Identity 5h 2 reactions of MeF + F- and MeCl + CP have been compared computationally with the reactions of MeF + LiF or NaF and of MeCl + LiCl.87 Calculations by new methods essentially confirm results obtained previously by other methods. Extension of the calculations to the corresponding ethyl systems gave lower barriers than for methyl systems in the reactions involving ion pairs as nucleophiles. 

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