NacNac

NacNac is the name for a class of anionic bidentate ligands. 1,3-Diketimines are often referred to as "HNacNac", a modification of the abbreviation Hacac used for α,β-diketones. These species can exist as a mixture of tautomers.[1]

Tautomers of a substituted HNacNac ligand precursor and an idealized complex (right) of the conjugate base (M = metal, L = other ligand)

Preparation of ligands and complexes

Acetylacetone and related 1,3-diketones condense with primary alkyl- or arylamine resulting in replacement of the carbonyl oxygen atoms with NR groups, where R = aryl, alkyl. To prepare 1,3-diketimines from bulky amines, e.g. 2,4,6-trimethylanilines, prolonged reaction times are required.

Deprotonation of HNacNac compounds affords anionic bidentate ligands that form a variety of coordination complexes.[2] Some derivatives with large R groups can be used to stabilize low valent main group and transition metal complexes.[3] Unlike the situation for the acetylacetonates, the steric properties of the coordinating atoms in NacNac− ligands is adjustable by changes in the R substituent. Attachment to a metal center is usually carried out by initial deprotonation of HNacNac with n-butyllithium; the lithium derivative is then treated with a metal chloride to eliminate LiCl. In some cases, HNacNacs also serve as charge-neutral 1,3-diimine ligands.

Related NacNac ligands

NacNac ligands are diimine analogues of acetylacetonate ligands. An intermediate class of ligands are derived from monoimino-ketones.[4][5]

Synthesis of "Jaeger" N2O2 ligand.

See also

References

  1. ↑ D. J. Mindiola, P. L. Holland,† T. H. Warren "Complexes of Bulky β-Diketiminate Ligands" Inorganic Syntheses, 2010, vol. 35, pp. 1–55. doi:10.1002/9780470651568.ch1
  2. ↑ Bourget-Merle, L.; Lappert, M. F.; Severn, J. R. (2002). "The Chemistry of Diketiminatometal Complexes". Chemical Reviews 102: 3031–3066. doi:10.1021/cr010424r.
  3. ↑ Qian, B.; Ward, D. L.; Smith, M.R. (1998). "Synthesis, Structure, and Reactivity of β-Diketiminato Aluminum Complexes". Organometallics 17: 3070–3076. doi:10.1021/om970886o.
  4. ↑ Dennis P. Riley, Daryle H. Busch "Macrocyclic Tetraazatetraenato Ligands and their Metal Complexes" Inorganic Syntheses, 1978, volume 18, p. 36. doi:10.1002/9780470132494.ch7
  5. ↑ Birgit Weber, Ernst-G. Jäger "Structure and Magnetic Properties of Iron(II/III) Complexes with N2O22– Coordinating Schiff Base Like Ligands" Eur. J. Inorg. Chem. 2009, pp. 455. doi:10.1002/ejic.200990003
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