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The Study of the Steric and Electronic Effects on n → π* Interactions in a Series of New Rhenium (I)Tricarbonyl Complexes

Taghavi, Tahereh | 2024

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 57060 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Kia, Reza
  7. Abstract:
  8. In this research, synthesis, structural and theoretical studies of new rhenium (I) tricarbonyl complexes with general formula, [Re(CO)3(NN)X] in which NN´ is chelating bidentate diimine ligand and X = Perrhenate, NO2 and ONO ligands were studied. The synthesized complexes were characterized by 1H-NMR, FT-IR and ESI-mass spectroscopic methods and their solid state structures were determined by X-ray diffraction analysis. Crystal structure determination by single-crystal X-ray diffraction allows us to fully examine the intramolecular and intermolecular interactions. The energy of different n → π* interactions also was investigated. Since three carbonyl groups are present in these complexes, we are expecting the n → π* interactions. It was shown that such interactions contribute to the molecular geometry and crystal packing of the metal carbonyl complexes and are assisted by the presence of the coordinated peroxo anion in the complexes. It is worth mentioning that compounds [Re(CO)3(Ph4TAP)(ReO4)] and [Re(dafone)(CO)3(ReO4)] are the first report of superoxidation of rhenium (I) to rhenium (VII) in rhenium complexes (Dafone: 4,5-diazafluoren-9-one and Ph4TAP: 2,3,6,7-tetraphenyl-1,4,5,8-tetraazaphenanthrene.). Also, the dominant effects of the intra- and intermolecular n → π* interactions in the intramolecular geometry and supramolecular assembly of these complexes have been confirmed computationally by natural bond orbitals (NBOs) and non-covalent interaction index (NCI) methods. In the second part, the obtained results showed that the methyl substitution only in positions 2 and 6 of the benzene rings of the diimine ligand is effective on the coordination of the NO2 ligand as nitrito, which causes the nitrito to rotate into the complex and create Intramolecular n → π* interaction with carbonyl groups which indicates the supporting of electronic effects by steric effects. Also, in the NBO calculation section, it was shown that the reason for rotating the nitrito ligand was to reach more stability and NCI calculations confirmed these interactions
  9. Keywords:
  10. Diimine Ligand ; X Ray Diffraction ; Rhenium (I)Tricarbonyl ; Intramolecular Interactions ; Intermolecular Interactions

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