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

Four new ligands of diphosphinoazine type together with their dioxides were synthesized and characterized. The crystal structure of the dioxide Pri 2P(O)CH2C(But)NNC(But)CH2P(O)Pri 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-(η3-2-methylpropenyl)palladium], thus forming new binuclear palladium complexes with asymmetric η3-2-methylpropenyl ligand. Phase-sensitive 2D 1H NOESY of the complexes revealed a short distance between syn protons on the terminal carbon of η3-2-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 13C 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 (31P, 13C), however, the series is different from that obtained using published substituent contribution data on electron donor–acceptor properties of phosphines.