Salicylaldehyde-(2-hydroxyethyl)imine – A flexible ligand for group 13 and 14 elements

• One and the same Schiff-base ligand delivers different complex types.
• Tetra-, penta-, and hexacoordinated complexes were prepared.
• Factors determining the kind of complex were identified empirically.
• The electron density distribution around the central atoms has been analysed.

The reaction of salicylaldehyde-(2-hydroxyethyl)imine (H2L), 1, with organoelement halides from group 13 and 14 leads to a variety of coordination compounds. Depending on the size of the central atom and the organic substituents, tetra-, penta- or hexacoordinated complexes emerge. When the central atom of the complex has a small atom radius and small substituents, like methyl groups, coordination number four is preferred. Thereby macrocyclic compounds of the composition L2(SiMeR)2 (R = Me, cyclohexyl) are formed. With phenyl substituted element halides Ph2ECl2 pentacoordinated complexes LEPh2 (E = Si, Ge, Sn) were isolated. Hexacoordinated complexes of the composition L2E (E = Si, Sn) were obtained from ECl4 and 1. A surprising result was obtained from the reaction of 1 with InCl3. The resulting complex is a monoanionic trimer, obeying the composition [HNEt3][L3In3Cl3(μ3-OH)]·(DME)2(THF) in the solid state structure. The prepared compounds were characterised by NMR and IR spectroscopy, elemental and X-ray structure analysis. Furthermore solid state NMR measurements and chemical shift tensor analysis with the help of quantum chemical methods were used to analyse the electron density distribution around the central atoms of several products. The results of this study demonstrate the structural variety that can be created with a single O,N,O′ chelating ligand.

One and the same Schiff-base ligand delivers tetra-, penta-, and hexacoordinated complexes with organoelement halides from group 13 and 14.Figure optionsDownload as PowerPoint slide