Diphosphinoazines (Z,Z)-R2PCH2C(Bu-t)=NN=C(Bu-t)C H2PR2 with R groups of various sizes and complexes {[(Z, Z)-R2PCH2C(Bu-t)=NN=C(Bu-t)CH2PR2]-[eta(3)-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 NOE SY of the complexes revealed a short distance between syn protons on the te rminal carbon of eta (3)-2-methylpropenyl ligand cis to phosphorus and prot ons of substituent groups on phosphorus for isopropyl, cyclohexyl, and tert -butyl complex. This evidence is further borne out by specifically broad re sonances in C-13 NMR spectra, suggesting hindered rotation of substituent g roups on phosphorus. The diphosphinoazines can be grouped into a series wit h monotonous change of chemical shifts of selected nuclei (P-31, C-13), how ever, the series is different from that obtained using published substituen t contribution data on electron donor-acceptor properties of phosphines. (C ) 2001 Elsevier Science B.V. All rights reserved.