Characterization of the molecular-level structures of heterogeneous catalysts is important for understanding how they work. There are many chlorine-containing transition-metal organometallic and inorganic catalysts in use today in a wide range of organic reactions and polymerization processes. Robert W. Schurko and his team, University of Windsor, Canada, in collaboration with groups from the Université Lille Nord de France, France, the Steacie Institute for Molecular Sciences, Canada, and ESCPE Lyon, France, have combined ³⁵Cl solid-state NMR (SSNMR) and ³⁵Cl nuclear quadrupole resonance (NQR) spectroscopies and DFT calculations of NMR interaction tensors for the structural characterization of chlorine-containing complexes.

The use of a special pulse sequence allows for the quick acquisition of ³⁵Cl SSNMR spectra at both moderate and high magnetic fields and can distinguish between bridging and terminal chlorine environments on the basis of the quadrupolar parameters. ³⁵Cl SSNMR and NQR spectroscopies are themselves complementary techniques: the former provides approximate values of quadrupolar coupling constants (C_Q) and asymmetry parameters (η_Q), whereas NQR can be used to identify multiple sites with similar quadrupolar parameters and to refine values of C_Q. First-principles ³⁵Cl DFT calculations provide important information on the relationship between the ³⁵Cl electric field gradient (EFG) tensors and molecular structure. Additionally, for the first time, ³⁵Cl SSNMR is used to observe TiCl₄ supported on mesoporous silica.

This combination of techniques is a promising and simple method for the characterization of all manner of chlorine-containing transition-metal complexes, in both bulk and supported forms.

• A Study of Transition-Metal Organometallic Complexes Combining ³⁵Cl Solid-State NMR and ³⁵Cl NQR Spectroscopy and First-Principles DFT Calculations,
  K. E. Johnston, C. A. O’Keefe, R. M. Gauvin, J. Trébosc, L. Delevoye, J.-P. Amoureux, N. Popoff, M. Taoufik, K. Oudatchin, R. W. Schurko,
  Chem. Eur. J. 2013.
  DOI: 10.1002/chem.201301268