Synthesis of a new P2N2 ligand N,N′-bis[2-(diphenylphosphino)phenyl]propane-1,3-diamine, H2L2, and some of its complexes with elements of the nickel triad and rhodium: X-ray structure analyses of the neutral complex [NiL2] and the trans-spanned [Rh(CO)Cl(H2L2)]

Abstract

The new multidentate phosphorus–nitrogen P₂N₂ hybrid ligand N,N′-bis[2-(diphenylphosphino)phenyl]propane-1,3-diamine, H₂L², has been prepared by demetallation of its neutral deprotonated nickel complex [NiL²],(1a), obtaibed from the metal-template catalysed condensation of bis(2-phenylphosphinophenylamido)nickel(II), [Ni(HL¹)₂], with 1,3-bis(toluene-p-sulphonyloxy)-propane in the presence of base. Under basic conditions, H₂L² forms complexes (1b) and (1c) analogous to (1a) with palladium(II) and platinum(II) in which the ligand is tetradentate around a square-planar metal ion. The complexes (1) may be protonated to form the corresponding dications [M(H₂L²)]²⁺, (2a)–(2c). With rohodium(I), H₂L² forms both the monocation [Rh(H₂L²)]⁺, (3), and the neutral square-planar complex [Rh(CO)Cl(H₂L²)], (4), in which H₂L² behaves as a P₂trans-spanning bidentate ligand. X-Ray crystal-structure analyses of both (1a) and (4) have been performed. Compound (1a) crystallises with a molecule of mesitylene as solvate in the tetragonal space group I/4₁/a with a= 35.246(6) and c= 13.190(2)Å and Z= 16. Blocked full-matrix refinement of 2 837 unique reflections with I 3σ(I)(3.0 < θ < 25.0°) gave R= 0.065 and R′= 0.062. Crystals of (4) have the monolinic space group Cc with a= 12.192(2), b= 14.125(2), c= 20.474(4)Å, β= 92.85(2)°, and Z= 4. Blocked full-matrix refinement of 1 975 reflections with I > 2.5σ(I)(1.0 < θ < 25.0°) gave R= 0.041 and R′= 0.047.