NICKEL-COMPLEXES OF THIOHYDRAZONATES .3. CRYSTAL AND MOLECULAR-STRUCTURES OF [2,4-PENTANEDIONE BIS(THIOACETHYDRAZONATO)]NICKEL(II)-ACETONITRILE ADDUCT, TETRABUTYLAMMONIUM [2,4-PENTANEDIONE BIS(THIOACETHYDRAZONATO)] NICKELATE(II), AND [PENTANETRIONE 2,4-BIS(THIOACETHYDRAZONATO)]NICKEL(II)

The crystal structures of the three related nickel thiohydrazonate complexes indicated in the title have been studied by single-crystal X-ray crystallography. The parent compound, [2,4-pentanedione bis(thioacethydrazonato)]nickel(II), crystallizes as an acetonitrile adduct, I, in the monoclinic space group P21/c, with a = 22.671 (14) Å, b = 7.253 (5) Å, c = 17.359 (12) Å, β = 112.90 (4)Δ, and Z = 8. This compound is an acid and the corresponding base has been crystallized as a tetra-n-butylammonium salt. This latter compound, II, crystallizes in the monoclinic space group P21/c with a = 21.662 (3) Å,b = 8.7604 (9) Å, c = 16.427 (3) Å, β = 101.49 (2)Δ, and Z = 4. The complex formed by air oxidation of the acid or the anion is a thiohydrazonate complex, III, derived from 2,3,4-pentanetrione and it crvstallizes in the triclinic space group P&&, a = 7.567 (3) Å, b = 9.957 (4) Å, c = 10.939 (5) Å, α = 123,09 (2)Δ, β = 107.47 (2)Δ, γ = 91.19 (3)Δ, and Z = 2. The structures contain planar nickel(II) complexes with similar coordination of the nickel atoms. The acetonitrile molecules in I are disordered. The two crystallographically independent molecules in I have similar molecular dimensions, but they do not have as high a symmetry as the complexes in II and III both of which have an effective twofold axis of symmetry. The bond lengths in the acetylacetone part of the ligand in the structures of I and II are similar, indicating that I is present in a dipolar tautomeric form. This result is supported by 1H NMR measurements. A comparison is given of the molecular dimensions of the structures internally and of related compounds, Finally the observed color differences between the three structures, of which I and II are red and III is green, are discussed in terms of simple MO theory. © 1979, American Chemical Society. All rights reserved.