Metal complexes of diiminodiphosphines. Structural and reactivity patterns

John C. Jeffery, Thomas B. Rauchfuss, Paul A. Tucker

Research output: Contribution to journalArticle

Abstract

The coordination chemistries of N,N′-bis[o-(diphenylphosphino)benzylidene]ethylenediamine (en=P2) and the corresponding 1,3-diaminopropane derivative (tn=P2) have been explored for the metals nickel, copper, and silver, and these results provide fundamental information on this novel class of metal complexes. The ligands function as tetradentate chelating agents for these metal ions as inferred from spectroscopic data and proven by the X-ray structure of [Cu(en=P2)]ClO4·CH2Cl2, the first iminophosphine chelate thus characterized. The crystals are triclinic, of space group P1, with a = 14.140 (3) Å, b = 24.926 (5) Å, c = 11.430 (3) Å, α = 94.45 (1)°, β = 81.91 (1)°, γ = 97.42 (1)°, and Z = 4. The complex adopts a severely distorted tetrahedral geometry, and this strain is manifested in its reactivity. The four-coordinate complexes M(en=P2)z (M = Cu or Ag, z = 1+; M = Ni, z = 2+) all react with additional ligands L (M = Ag or Cu, L = tert-butyl isocyanide (t-BuNC); M = Ni, L = Br-), affording five-coordinate adducts in the case of Ni(II) and Ag(I). Crystals of the derivative [Cu(en=P2)(t-BuNC)]ClO4, examined by X-ray methods show the metal to be tetrahedrally coordinated. The first coordination sphere contains only one imine functionality in addition to the isocyanide and the two phosphine moieties. The crystals are orthorhombic, of space group P222, with a = 30.232 (9) Å, b = 16.144 (4) Å, c = 8.450 (2) Å, and Z = 4. The complex is a unique example of a nine-membered chelate ring bound to a tetrahedral complex and is formed by the displacement of an internal donor of the chelate. All complexes are dynamic on the NMR time scale (-80 to 35°C), and mechanisms consistent with the spectroscopic and X-ray data are presented. The electrochemical behavior of the complexes demonstrate the interconvertability of the [M(en=P2)]z unit containing the metal ion in the d8, d9, and d10 configurations for M = Ni or Cu. The impact of the additional methylene group in the tn=P2 complexes vs. the en=P2 analogues is assessed chemically and electrochemically.

Original languageEnglish (US)
Pages (from-to)3306-3316
Number of pages11
JournalInorganic Chemistry
Volume19
Issue number11
StatePublished - 1980

ASJC Scopus subject areas

  • Inorganic Chemistry

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