Mixed carbene–isocyanide Pd(ii) complexes: synthesis, structures and reactivity towards nucleophiles

Abstract

Reaction of the bromo-bridged dimeric monocarbene complex [PdBr₂(ⁱPr₂-bimy)]₂ (1) (ⁱPr₂-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene) with various isocyanides afforded a series of mixed carbene–isocyanide complexes [PdBr₂(ⁱPr₂-bimy)(CN-R)] (2a: R = Cy; 2b: R = ⁿBu; 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 2c with AgO₂C₂F₃ afforded a cis arranged complex [Pd(O₂CCF₃)₂(ⁱPr₂-bimy)(CN-Xyl)] (cis-7). Most complexes were fully characterized by multinuclei NMR spectroscopies, ESI or FAB mass spectrometry and X-ray diffraction analysis.