Synthesis- and crystal structure of palladium(0) and arylpalladium(II) bromide complexes of CataCXium A

Diphosphine palladium(0) (1) and arylpalladium(II) bromide complexes (2a-d) of di-1-adamantyl-n-butylphosphine (CataCXium A) have been synthesized. The PdL2 complex 1 takes a remarkable eclipsed conformation of the substituents along the P-Pd-P direction. NMR and X-ray studies of 2a showed its dimeric structure with the n-butyl groups of the coordinated phosphine ligands lying nearly parallel to the planes of the aromatic rings, which results in an anomalous H-1 NMR upfield shift of the n-butyl protons caused by the aromatic ring current effect.