Mixed carbene-isocyanide Pd(II) complexes: synthesis, structures and reactivity towards nucleophiles.

Reaction of the bromo-bridged dimeric monocarbene complex [PdBr(2)((i)Pr(2)-bimy)](2) (1) ((i)Pr(2)-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene) with various isocyanides afforded a series of mixed carbene-isocyanide complexes [PdBr(2)((i)Pr(2)-bimy)(CN-R)] (2a: R = Cy; 2b: R = (n)Bu; 2c: R = Xyl) as inseparable mixtures of trans- and cis-isomers. The reactivity of 2c towards nucleophiles was studied. A new mixed NHC-ADC Pd(ii) complex (4) was obtained in low yield when 2c was reacted with 2,6-dimethylaniline. Reaction of 2c with hydrazine yielded a hydrazine-bridged complex (6) via ligand substitution. In addition, salt metathesis of with AgO(2)C(2)F(3) afforded a cis arranged complex [Pd(O(2)CCF(3))(2)((i)Pr(2)-bimy)(CN-Xyl)] (cis-). Most complexes were fully characterized by multinuclei NMR spectroscopies, ESI or FAB mass spectrometry and X-ray diffraction analysis.