Diphosphinoazines (Z,Z)-R2PCH2C(But)=NN=C(But)C H2PR2 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 (Pr2P)-P-1(O)CH2C(Bu-t) NN=C(Bu-1)CH2P(O)Pr-2(1), 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[mu -chloro-(eta (3)-2-methylpropenyl)palladium], thus forming new binuclear palladium complexes with asymmetric eta (3)-2-methylpropenyl ligand. Phase-sensitive 2D H-1 NOESY of the complexes revealed a short distance between syn protons on the terminal carbon of eta (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 C-13 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 (P-31, C-13), however, the series is different from that obtained using published substituent contribution data on electron donor-acceptor properties of phosphines. (C) 2001 Elsevier Science B.V. All rights reserved.