Synthesis and characterization of iron and cobalt complexes with an asymmetric N-alkyl,N′-aryl-β-diketiminate ligand

An asymmetric N-alkyl,N′-aryl-β-diketiminate ligand L (L = 2-((S)-(-)-1-phenylethylimino)-4-(2,6-diisopropylphenylimido)pentane) was prepared. Synthesis of solvent-free chloro-bridged dimers, [LFe(μ-Cl)]2 and [LCo(μ-Cl)]2 are presented. Upon reduction in the presence of cis-cyclooctadiene, rare examples of low-valent complexes LFe(cod) and LCo(cod) were obtained. All metal complexes were fully characterized by 1H NMR spectroscopy, elemental analysis, and X-ray crystallography. Crystallographic and spectroscopic results indicate that the N-alkyl,N′-aryl-β-diketiminate ligand L is sterically smaller but a better electron donor than the N,N′-diaryl-substituted β-diketiminate ligand LMe,Dipp (LMe,Dipp = 2,4-bis(2,6-diisopropylphenylimido)pentane).