Synthesis and characterization of complexes of PdII and PtII containing the iminophosphorane ligand Ph3P=NC≡N

Article abstract of DOI:10.1039/a805147j

The chemistry of the iminophosphorane Ph₃P=NC≡N towards different palladium(II) and platinum(II) subtrates has been investigated. This ligand shows a high selectivity for co-ordination through the terminal N atom (that of the cyanide group), while the phosphoiminic N atom shows very poor nucleophilic ability. The reaction of [PdCl₂(NCPh)₂] with Ph₃P=NCN (1:2 molar ratio) gives trans-[PdCl₂(NCNPPh₃)₂] 1. The crystal structure of 1 has been determined and shows the iminophosphorane co-ordinated selectively through the nitrilic N atom. The reaction of the cationic derivatives [M(C-P)(NCMe)₂][ClO₄] [M = Pd or Pt; C-P = o-CH₂C₆H₄P(C₆H₄Me-o) ₂] with Ph₃P=NCN (1:2 molar ratio) resulted in the formation of [M(C-P)(NCN=PPh₃)₂][ClO₄] (M = Pd 2 or Pt 3), for which the same terminal N-co-ordination has been observed. The reaction of [Pd(dmba)(NCMe)₂][ClO₄] (dmba = C₆H₄CH₂NMe₂-2) with Ph₃P=NCN (1:1 molar ratio) gave the dinuclear derivative [{Pd(μ-NCN=PPh₃)-(dmba)}₂][ClO₄]₂ 4 in which the iminophosphorane acts as an N,N-bridging ligand, while reaction in 1:2 molar ratio gave [Pd(dmba)(NCN=PPh₃)₂][ClO₄] 5 which possess N-terminal co-ordination. The reaction of this iminophosphorane with monosolvate complexes [Pd(dmba)(PPh₃)(THF)][ClO₄] or [Pt(C-P)(PPh₃)(NCMe)][ClO₄] (1:1 molar ratio) resulted in the formation of [Pd(dmba)(PPh₃)(NCN=PPh₃)][ClO₄] 6 or [Pt(C-P)(PPh₃)-(NCN=PPh₃)][ClO₄] 7, and the reaction with the halide bridging derivatives [{Pd(μ-Cl)(dmba)}₂] or [{Pt(μ-Cl)-(C-P)}₂] (2:1 molar ratio) produced cleavage of the bridging system and formation of [PdCl(dmba)(NCN=PPh₃)] 8 and [PtCl(C-P)(NCN=PPh₃)] 9. The same N-terminal co-ordination mode is observed in complexes 6-9.