Structural Diversity in Divalent Group 14 Triflate Complexes Involving Endocyclic Thia-Macrocyclic Coordination

Area of Science:

• Coordination Chemistry
• Organometallic Chemistry
• Macrocyclic Chemistry

Background:

• Thioether macrocycles are versatile ligands in coordination chemistry.
• Group 14 elements (Ge, Sn, Pb) offer unique electronic properties for complex formation.

Purpose of the Study:

• To synthesize and characterize novel M(II) complexes with endocyclic thioether macrocyclic ligands.
• To investigate the influence of metal ion, macrocycle size, and donor atoms on coordination behavior.

Main Methods:

• Reaction of macrocycles ([9]aneS3, [12]aneS4, [24]aneS8) with M(II) precursors (M = Ge, Sn, Pb).
• Characterization using NMR (1H, 13C, 19F, 119Sn), IR spectroscopy, high-resolution ESI+ MS, and microanalysis.
• X-ray crystallography for structural determination.
• Density Functional Theory (DFT) calculations.

Main Results:

• Successfully synthesized M(II) complexes with coordination numbers from 3 to 9.
• Crystal structures reveal endocyclic ligand binding, with coordination geometry dependent on metal and macrocycle.
• Solution NMR indicates stable metal-macrocycle coordination with dissociated triflate anions.
• DFT calculations show a directional lone pair on the group 14 atom in the HOMO.

Conclusions:

• The study demonstrates the formation of unusual M(II) complexes with thioether macrocycles.
• Coordination environment is highly tunable by varying the metal and macrocycle.
• The electronic structure of the group 14 metal is influenced by the macrocyclic ligand.