(pi-Allyl)palladium complexes with N,N'-diphenylbispidinone derivatives as a new type of chelating nitrogen ligand: Complexation studies, spectroscopic properties, and an x-ray structure of (3,7-diphenyl-1,5-dimethylbispidinone)[(1,3-eta(3)-propenyl)-palladium] trifluoromethanesulfonate

A series of 3,7-diazabicyclo[3.3.1]nonane (bispidine) derivatives have been synthesized, and their properties as bidentate nitrogen ligands for (pi-allyl)palladium complexes have been investigated. Complexes of these ligands and of N,N'-diphenylpiperazine (7) and N,N'-diphenyl-1,5-diazacyclooctane (8) with (1,3-eta(3)-propenyl)palladium are described, in particular their effects on the proton chemical shifts of the pi-allyl ligand. Ligand dynamics of the complexes is discussed. The structure of [(3,7-diphenyl-1,5-dimethylbispidinone) (propenyl)Pd]CF3SO3 (15) has been determined by X-ray crystallography. N,N'-Diphenylbispidine derivatives show an unusually large steric interaction with the pi-allyl ligand, indicated by a tilt of the pi-allyl plane toward the N-Pd-N plane by 122.8(8)degrees. Chemical shift changes of the pi-allyl protons due to the aromatic ring current are related to the geometry of the complexes. The ligands are tested on the larger 2-methylene-6,6-dimethylbicyclo[3.1.1]hept-2,3,10-eta(3)-enyl ligand, demonstrating their potential as chemical shift reagents.