Diverse donor properties exhibited by the facultative diphosphine diether ligand, 1,8-bis(diphenylphosphino)-3,6-dioxaoctane : six- and four-co-ordinate complexes and trans bidentate behaviour

Abstract

Reaction of the title ligand (dpdo) with nickel(II) salts leads to the isolation of [Ni(dpdo)X₂](X = Cl, Br, I, or NCS) complexes. In the solid state the previously prepared complex [Ni(dpdo)I₂] is distorted square planar, whilst [Ni(dpdo)X₂](X = Cl or Br) are pseudo-tetrahedral; all are planar in methylene chloride. A single-crystal X-ray analysis of the thiocyanate complex shows a monomeric planar species possessing a P–M–P angle of 175.9°. The ligand co-ordinates as a trans-bidentate diphosphine. The subtle effects governing the co-ordination properties of this ligand are illustrated by the isolation of the blue planar [Ni(dpdo)Br₂]·C₆H₅Me complex, The pseudooctahedral complex [Ni(dpdo)Cl₂]·4H₂O and the planar [Ni(dpdo)(H₂O)₂][BF₄]₂ have also been isolated.