Transition metal dithioacetylacetonates

Transition metal dithioacetylacetonates are coordination complexes containing dithioacetylacetonate (CH3CSCHCSCH−3, abbreviated SacSac-) as a bidentate ligand. Dithioacetylacetonate complexes are analogous to acetylacetonate complexes: both sulfur atoms bind to the metal to form a six-membered chelate ring. The simplest complexes have the formula M(SacSac)3 and M(SacSac)2. Mixed-ligand complexes are also known, e.g. Fe(SacSac)2(CO)2.[2]

Synthesis

Dithioacetylacetone is well-characterized, so complexes are prepared by indirect methods. In one approach, a solution of acetylacetone is treated with a mixture of hydrogen sulfide and hydrochloric acid prior to the addition of a metal halide. SacSac complexes can also be prepared by reduction of a 1,2-dithiolium salt with sodium borohydride followed by treatment with a metal salt.[3] A common unsymmetrical version of a HSacSac ligand is C6H5C(SH)=CHC(=S)OC2H5, which can be prepared from O-ethylthioacetate.[4]

Examples

Square planar complexes of the type M(SacSac)2 are known for Ni (red),[1] Pd (red), Pt (violet), Co (violet). Tetrahedral M(SacSac)2 are isomorphous for M = Mn, Zn, Cd.[5] In contrast with these structures, M(acac)2 are dimers or oligomeric for M = Co, Ni, Mn, Cd, Zn. The octahedral complex Fe(SacSac)3 is low-spin, in contrast to Fe(acac)3.[6]

Complexes are also well known for monothioacetylacetone (HSacac). The free ligand is readily obtainable as a distillable liquid,[7] which facilitates the preparation of these coordination complexes. Fe(Sacac)3 exhibits spin crossover behavior.

References

  1. ^ a b Beckett, Ronald; Hoskins, Bernard F. (1974). "Square-Planar Complexes of Pentane-2,4-dithione (Dithioacetylacetone): Crystal Structures of the Cobalt(II) and Nickel(II) Derivatives". Journal of the Chemical Society, Dalton Transactions (6): 622. doi:10.1039/dt9740000622.
  2. ^ Brown, S.J.; Kok, S. K. C.; Lay, P. A.; Masters, A. F. (1989). "Electrochemical Behavior of Bis[pentane-2,4-dithionato(1-)]iron(II), Fe(sacsac)2, and Dicarbonylbis[pentane-2,4-dithionato(1-)]iron(II), Fe(sacsac)2(CO)2". Australian Journal of Chemistry. 42 (11): 1839. doi:10.1071/ch9891839.
  3. ^ Lockyer, Trevor N.; Martin, Raymond L. (1980). "Dithiolium Salts and Dithio-β-Diketone Complexes of the Transition Metals". Progress in Inorganic Chemistry. Vol. 27. pp. 223–324. doi:10.1002/9780470166284.ch4. ISBN 978-0-471-06000-0.
  4. ^ Hendrickson, AR; Martin, RL (1972). "Thio-Derivatives of 1,3-Diketones and Their Metal Complexes ; O-ethyl thioacetothioacetate and Its Zinc(II), Cadmium(II), and Mercury(II) Derivatives". Australian Journal of Chemistry. 25 (2): 257. doi:10.1071/CH9720257.
  5. ^ Beckett, R.; Hoskins, B.F. (1972). "The Crystal and Molecular Structure of Bis(O-ethylthioacetothioacetato)zinc(II)". Inorganic and Nuclear Chemistry Letters. 8 (8): 679–682. doi:10.1016/0020-1650(72)80118-1.
  6. ^ Beckett, R.; Heath, G.A.; Hoskins, B.F.; Kelly, B.P.; Martin, R.L.; Roos, I.A.G.; Weickhardt, P.L. (1970). "X-Ray Diffraction, Magnetic, E.S.R., and Mossbauer Studies on the Low-Spin Complex Tris(dithioacetylacetonato)iron(III)". Inorganic and Nuclear Chemistry Letters. 6 (3): 257–260. doi:10.1016/0020-1650(70)80227-6.
  7. ^ Mayer, Roland; Hiller, G.; Nitzschke, Margot; Jentzsch, J. (1963). "Base-Catalysed Reactions of Ketones with Hydrogen Sulfide". Angewandte Chemie International Edition in English. 2 (7): 370–373. doi:10.1002/anie.196303701.
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