New Complexes of Antimony(III) with Tridentate O,E,O-Ligands (E = O, S, Se, Te, NH, NMe) Derived from N-Methyldiethanolamine

Abstract

We synthesized a series of new antimony(III) compounds by reaction of Sb(OEt)3 with organic ligands of the type E(CH2-CH2-OH)2, with E = NH, NMe, O, S, Se, and Te. The synthesized compounds have the general composition [E(CH2-CH2-O)2]Sb(OEt). For comparison, the compound (O-CH2-CH2-S)Sb(OEt) was prepared. All compounds are characterized using NMR, IR, and Raman spectroscopy. The molecular structures of the products reveal the formation of chelate complexes, wherein the ligand molecules coordinate as tridentate O,E,O-ligands to the antimony atom. Dimer formation in the solid state allows the antimony atoms to reach pentacoordination. Quantum chemical calculations including topological analysis of electron density reveal that there are polar shared bonds between antimony and the oxygen atoms bound to antimony. The interactions between the donor atom E and the Sb atom and the interactions in the dimers can be characterized as Van der Waals interactions. The reactivity of [MeN(CH2-CH2-O)2]Sb(OEt) was investigated as an example. For this purpose, the compound reacted with a range of organic compounds such as carboxylic acids and carboxylic anhydrides and small molecules like CO2 and NH3. This study establishes a new and easy accessible class of antimony(III) compounds, provides new insights into the chemistry of antimony compounds and opens up new opportunities for further research in this field.

Coordinative Unsaturation in an Antimony(III)-Complex with the 2-Salicylidenaminophenolato Ligand: Synthesis, Crystal Structure, Spectroscopic Analysis, and DFT Studies

“…The single crystal structure analysis reveals the molecular structure of LSb. In the solid state, the antimony atom is coordinatively saturated by the oxygen atoms of the neighboring complexes, similar to what was described in [53]. The molecular structure shows the elongation of the Sb-O bonds between the antimony center and the oxygen atoms of the tridentate ligand.…”

“…Furthermore, at the complex more aliphatic CH vibrations are evident for the complex than for the free ligand, indicating the presence of an additional aliphatic component. The bands at about 600 cm −1 indicate the Sb-O bonds, because they cannot be seen in the free ligand and are in a similar range as Sb-O bonds known in literature [53]. The bands just below 800 cm −1 , which can be seen in both spectra, indicate the presence of 1,2-disubstituated benzene derivatives.…”

“…The investigated complex consists of a Schiff-base ligand derived from salicylaldehyde and o-aminophenol. This ligand (H 2 L) was reacted with triethoxyantimony (Sb(OEt) 3 ) [53] to form the complex (LSb) under the release of two equivalents of ethanol (see Scheme 1).…”