| Abstract
| - New palladium π-allyl complexes with chelating phosphinocarbene ligands (P−C) have been preparedand fully characterized. The adopted synthetic strategy is based on the reaction between the appropriatesilver precursors and the labile [Pd(η3-allyl)OCOCF3]2. These complexes react with amines in the presenceof dimethyl fumarate, yielding the new palladium(0) complexes [Pd(η2-dmfu)(P−C)] and allylamine.Under pseudo-first-order conditions, the amination rates obey the simple law kobs = k2[NHR2], and thisobservation seems to rule out the possibility of a simultaneous amine attack at the central atom withdisplacement of the bidentate ancillary ligand (or of one of its donor groups). The k2 values increasewith increasing basicity of the amine, with decreasing steric hindrance at the allyl fragment, and withincreasing bulkiness of the P−C heterocyclic nitrogen substituent. Moreover a remarkable decrease ofthe amination rate is observed for the phosphinocarbene complexes as compared to the “isostructural”phoshinopyrazole (P−N) derivatives, in agreement with the strong σ-donating and weak π-acceptingcharacter of the carbene ligands. The new posphinocarbene ligands are tested in the palladium-catalyzedamination of 1,3-diphenylallylethyl carbonate, and the resulting low enantioselectivity may support theview of the comparable trans influence of carbene and phosphine ligands, which renders the correspondingtrans allyl carbons electronically equivalent.
- New π-allyl complexes of palladium(II) with phosphinocarbene (P−C) ligands were prepared and fully characterized. A comparative kinetic study of allylic amination between these substrates and their “isostructural” phosphinopyrazole (P−N) derivatives allows defining some of their interesting properties.
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