NacNac
Image:Chem structure of Hnacnac.png (M = metal, L = other ligand)]]
NacNac is a class of anionic bidentate ligands. 1,3-Diketimines are often referred to as "HNacNac", a modification of the abbreviation Hacac used for 1,3-diketones. These species can exist as a mixture of tautomers.{{cite journal|first1=D. J.|last1=Mindiola |first2=P. L.|last2=Holland|first3=T. H. |last3=Warren |title=Complexes of Bulky β-Diketiminate Ligands |journal=Inorganic Syntheses |date=2010 |volume=35 |pages=1–55 |DOI=10.1002/9780470651568.ch1}}
Preparation of ligands and complexes
Acetylacetone and related 1,3-diketones condense with primary alkyl- or arylamines 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. 2,6-Diisopropylaniline is a common bulky building block.
Deprotonation of HNacNac compounds affords anionic bidentate ligands that form a variety of coordination complexes.{{cite journal |last1=Bourget-Merle |first1=L. |last2=Lappert|first2=M. F. |last3=Severn |first3=J. R. |title= The Chemistry of Diketiminatometal Complexes |journal= Chemical Reviews |year= 2002 |volume= 102 |pages= 3031–3066 |doi= 10.1021/cr010424r}} Some derivatives with large R groups can be used to stabilize low valent main group and transition metal complexes.{{cite journal |last1= Qian|first1= B.|last2= Ward|first2= D. L.|last3= Smith|first3= M.R. |title= Synthesis, Structure, and Reactivity of β-Diketiminato Aluminum Complexes |journal= Organometallics |year= 1998 |volume= 17 |pages= 3070–3076 |doi= 10.1021/om970886o }} 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 lithium chloride. 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.{{cite journal|first=Birgit |last=Weber |first2=Ernst-G. |last2=Jäger |title=Structure and Magnetic Properties of Iron(II/III) Complexes with {{chem|N|2|O|2|2–}}-Coordinating Schiff Base-Like Ligands|journal= Eur. J. Inorg. Chem. |date=2009| page= 455 |DOI=10.1002/ejic.200990003 |volume=2009}}{{cite journal|first1=Dennis P. |last1=Riley |first2=Daryle H. |last2=Busch |title=Macrocyclic Tetraazatetraenato Ligands and their Metal Complexes |journal=Inorg. Synth. |date=1978 |volume=18 |page=36 |DOI=10.1002/9780470132494.ch7}} The first Dipp-NacNac ligand was synthesized by Dr. Francis S. Mair in 1998.{{cite journal|last1= Mair|first1=Frank S.|last2=Cope|first2=Elaine K.|last3=Clegg|first3=William|last4=Edwards|first4= Andrew J.|title=Structural Characterization of [(2,6-Pri2C6H3)NC(Me)C(H)C(Me)N(2,6-Pri2C6H3)K·PhCH3]∞: A Heavy Alkali Metal Diazapentadienyl Complex|journal=Inorg. Chem.|volume=37|year=1998|doi=10.1021/ic970956j}}