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

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.