857641-50-0Relevant articles and documents
Apparent allyl rotation and Pd-N bond rupture in allylpalladium complexes with N-donor ligands - Evidence of an associative mechanism
Jalon, Felix A.,Manzano, Blanca R.,Moreno-Lara, Belen
, p. 100 - 109 (2007/10/03)
The new didentate N-donor ligands 2-(4-methyl-1H-pyrazol-1-yl)pyrimidine (4Me-pzpm, 1) and 2-(4-bromo-1H-pyrazol-1-yl)pyrimidine (4Br-pzpm, 2) have been synthesised and used to obtain the allylpalladium derivatives [Pd(η3-2Me-C3H4)(NN′)]X [X = BAr′4-, NN′ = 1 (3), NN′ = 2 (4); X = CF3SO3-, NN′ = 1 (5), NN′ = 2 (6)]. In complexes 3-6 two types of fluxional process have been found: apparent allyl rotation that is observed as Hsyn-Hsyn, H anti-Hanti interconversions and H4-H 6 interchange of the pyrimidine protons that must involve Pd-N(pm) bond rupture. The influence of different factors on both processes - such as the nature of the N-donor ligand, counterion, solvent, complex concentration and addition of water - has been studied. It has been concluded that the apparent allyl rotation has a lower free energy of activation and in both cases the presence of a species with coordinating ability favours the process. Negative entropies of activation have been found. Associative mechanisms involving participation of five-coordinate intermediates have been proposed. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
