Synthesis and structure of novel strontium complexes of unsymmetrically functionalized β-diketimine ligands

A series of tridentate β-diketiminate ligands, (2Z,4E)-4-{[2-(dimethylamino)ethyl]imino}-N-(propan-2-yl)pent-2-en-2-amine (L1H), (2Z,4E)-4-{[3-(dimethylamino)propyl]imino}-N-(tert-butyl)pent-2-en-2-amine (L2H), and (2Z,4E)-4-{[3-(dimethyl-amino)propyl]imino}-N-(propan-2-yl)pent-2-en-2-amine (L3H), and their strontium complexes, SrL21 (1), SrL22 (2), and SrL23 (3) were synthesized as potential strontium precursors, by the reaction of Sr[N(SiMe3)2]2 and two equivalents of L1H, L2H, and L3H, respectively. Compounds 1–3 were characterized by spectroscopic (IR, MS, 1H and 13C NMR), microanalytical methods, and single crystal X-ray diffractometry. The X-ray crystal structure reveals that complex 1 has a monoclinic space group, C2/c. The structure shows the bonding of two β-diketiminate ligands to the strontium metal through six nitrogen atoms. Additionally, the isopropyl groups on the ligands force 1 to attain a highly distorted octahedron. Thermogravimetric analyses of the compounds 1–3 exhibit a primary mass loss on 130–300 °C region.

Unsymmetrically functionalized β-diketiminate ligands (L1H, L2H, L3H) were synthesized and strontium complexes (1–3) were prepared using these ligands and characterized. The crystal structure of 1 describes the bonding nature of the ligand to the metal, in which bulky groups present in β-diketiminate ligands force the metal center to attain a highly distorted octahedral structure.Figure optionsDownload as PowerPoint slideHighlights
► Synthesis of new tridentate β-diketimine ligands and strontium bis(tridentate β-diketiminate) complexes.
► The coordination environments of complex 1 was confirmed by X-ray crystallography.
► Studies for thermal properties of strontium bis(tridentate β-diketiminate) complexes by TGA.