Diphosphinoazines (Z,Z)-R2PCH2C(But)NNC(But)CH2PR2 with R groups of various sizes and complexes {[(Z,Z)-R2PCH2C(But)NNC(But)CH2PR2]-[η3-CH2C(CH3)CH2PdCl]2}

Abstract Four new ligands of diphosphinoazine type together with their dioxides were synthesized and characterized. The crystal structure of the dioxide Pr i  2 P(O)CH 2 C(Bu t )NNC(Bu t )CH 2 P(O)Pr i  2 , which crystallizes as a solvate with 1 mol of hydrogen peroxide, was determined by X-ray diffraction. The ligands were used to split the chlorine bridge of bis[μ-chloro-(η 3 -2-methylpropenyl)palladium], thus forming new binuclear palladium complexes with asymmetric η 3 -2-methylpropenyl ligand. Phase-sensitive 2D 1 H NOESY of the complexes revealed a short distance between syn protons on the terminal carbon of η 3 -2-methylpropenyl ligand cis to phosphorus and protons of substituent groups on phosphorus for isopropyl, cyclohexyl, and tert -butyl complex. This evidence is further borne out by specifically broad resonances in 13 C NMR spectra, suggesting hindered rotation of substituent groups on phosphorus. The diphosphinoazines can be grouped into a series with monotonous change of chemical shifts of selected nuclei ( 31 P, 13 C), however, the series is different from that obtained using published substituent contribution data on electron donor–acceptor properties of phosphines.