The transamination of alkyl-palladium halide N-heterocyclic carbene complexes has enabled the isolation of products that reveal interesting insights into the factors which might be barriers to the development of a palladium-catalysed alkyl-amination reaction.

The dimers [trans-[(neopentyl)Pd(µ-Cl)(I t Bu)] 2 , 2, and (cis-[(neopentyl)Pd(µ-Cl)(IPr)] 2 , 3 (I t Bu ) 1,3bis-tert-butylimidazol-2-ylidene, IPr ) 1,3-bis-2,6-diidopropylimidazol-2-ylidene), have been synthesized from [Pd(neopentyl)(Cl)(1,5-COD)], and their reactivity toward a variety of nucleophiles has been evaluated. In particular, this study revealed that 2 can be readily cleaved by primary and secondary amines, affording stable transamination products, which are surprisingly resistant to deprotonation. Dimer 3 was subsequently used as a catalyst in a series of Buchwald-Hartwig amination reactions of aryl chlorides.

The reaction of Me 3 SiCH 2 I with [Pd(ItBu) 2 ] (ItBu = 1,3-ditert-butyl-imidazol-2-ylidene) results, not in simple oxidative addition, but in carbon-silicon bond activation and formation of [Pd(Me 3 Si)(ItBu)(µ-I)] 2 (2) and [Pd(CH 2 ItBu)I 2 ] (3). The zwitterionic nature of the latter has been confirmed by DFT studies, and a possible mechanism for the formation of these

The reaction between 2-chlorobenzylamine or 2-chlorobenzylalcohol and Pd(I(t)Bu)(2) (I(t)Bu = 1,3-di-tert-butylimidazol-2-ylidene) in benzene affords the dimeric complexes [Pd(I(t)Bu)(mu-NH{2-CH(2)C(6)H(4)})](2) and [Pd(I(t)Bu)(mu-O{2-CH(2)C(6)H(4)})](2); the latter has been structurally characterised. The syntheses, structural characterisation and reactivity of the Pd-NHC amine complexes [(I(t)Bu)Pd(R-4-C(6)H(4))(morpholine)Cl] (R = Me, OMe, CO(2)Me), intermediates in the Buchwald-Hartwig aryl amination reaction, are also reported.

Amines Q 0120Alkylpalladium N-Heterocyclic Carbene Complexes: Synthesis, Reactivity, and Catalytic Properties. -The carbene complexes are effective precatalysts for a series of Buchwald-Hartwig amination reactions of aryl halides. -(ESPOSITO, O.; GOIS, P. M. P.; DE K. LEWIS, A. K.; CADDICK*, S.; CLOKE, F. G. N.; HITCHCOCK, P. B.; Organometallics 27 (2008) 24, 6411-6418; Dep. Chem., Univ. Coll., London WC1H 0AJ, UK; Eng.) -Kieslich 18-071