Reactions of Coordinated Ligands. Part 19: Template Synthesis of a Macrocyclic Secondary Tetraphosphine by Oxidative Demetallation of Crown Phosphine Ni(II) Complexes

The nickel(II) complex 3 containing a 14-membered macrocyclic triphosphine phosphinate ligand is obtained by regioselective oxidation of the crown phosphine nickel(II) complex 2c with molecular oxygen. The X-ray structure of 3·H2O (space group P21/c) has been determined. Oxidation of the macrocyclic phosphinous acid nickel(II) complex 2a (P4 donor set) with H2O2/HCl or Br2 and subsequent demetallation affords the macrocyclic phosphinic acid 5. Reaction of its methylester 6 with thionyl chloride and subsequent reduction with LiAlH4 gives the novel macrocyclic PH functional tetradentate phosphine 8 in high yields.