Dinuclear palladium(I) complexes with isocyanide and N-donor bidentate ligands

Reactions of the dinuclear palladium(I) complex [Pd2Cl2(RNC)(4)] (R=2,4,6-Me(3)C(6)H(2)) 1 with the N-donor compounds 2,2'-bipyridyl (bipy), 1,10-phenanthroline (phen), and 2,9-dimethyl-1, 10-phenanthroline (dmphen) gave dipalladium(I) complexes with chelating N-donor ligands, [Pd-2(RNC)(2)L(2)] [PF6](2) (L=bipy 2, phen 3 or dmphen 4). The structures of 2 and 4 were characterized by X-ray crystallography. The cation of 2 is composed of two Pd atoms joined by a sigma bond [2.518(3)Angstrom] each of which has a square-planar co-ordination involving a terminal isocyanide and a chelating bipy ligand. Complex 3 is expected to have a structure similar to 2 on the basis of spectroscopic data. Complex 4 exhibits a distorted dinuclear structure due to the steric bulk of the N-donor ligand. The Pd-Pd bond length is 2.599(2)Angstrom. Each dmphen ligand; chelates to a Pd atom and the isocyanide acts as a semibridging ligand. The similar reactions of complex 1 with 2,2'-biquinoline (bquin) and 1,8-naphthyridine (napy) afforded the isocyanide-bridged dipalladium(I) complexes, [Pd-2(mu-RNC)(2)(bquin)(2)]-[PF6](2) 5 and [Pd-2(mu-RNC)(2)(napy)(4)] [PF6](2) 6, in 24-36% yields. Complex 6 comprises a dinuclear palladium(I) core bridged by two isocyanide ligands [Pd-Pd 2.747(4)Angstrom] with four terminal napy ligands co-ordinated in a monodentate fashion.