Tris(bis(trimethylsilyl)amido)samarium: X-ray structure and DFT study

Area of Science:

• Organometallic Chemistry
• Lanthanide Chemistry
• Computational Chemistry

Background:

• Tris[bis(trimethylsilyl)amido]lanthanides exhibit unique structural features.
• Agostic interactions, weak bonds between metal centers and C-H bonds, are increasingly recognized in organometallic compounds.

Purpose of the Study:

• To investigate the structure and bonding of Sm[N(SiMe3)2]3.
• To elucidate the nature and significance of agostic interactions in this lanthanide complex.

Main Methods:

• X-ray crystallography for experimental structural determination.
• Density Functional Theory (DFT) calculations for computational modeling and bonding analysis.
• Mulliken and NBO (Natural Bond Orbital) methods for detailed bonding insights.

Main Results:

• Experimental and computational studies confirm a trigonal pyramidal structure for Sm[N(SiMe3)2]3, with positional disorder of the samarium atom.
• The presence of beta-Si-C agostic interactions was identified, involving methyl groups of the amido ligands and the samarium center.
• DFT calculations demonstrated the crucial role of samarium and silicon d orbitals in establishing the pyramidal geometry, Sm-N bond lengths, and Sm-(beta-Si-C) bond lengths.

Conclusions:

• Beta-Si-C agostic interactions are significant in tris[bis(trimethylsilyl)amido]lanthanide complexes.
• Metal d orbitals play a vital role in both the Sm-N and Sm-(beta-Si-C) bonding.
• Electrostatic contributions are important for the agostic interaction, while pi bonding has a lesser role in defining the observed geometries.