Implementing 3D electron diffraction at York to determine structures of challenging small molecule organometallic compounds

The elucidation of accurate 3D structures is of vital importance in chemistry and is fundamental to understanding the chemical and physical properties of a material. Thus far, X-ray crystallography has stood as the gold standard method for structure determination. However, obtaining sufficiently large crystals of quality suitable for single-crystal X-ray diffraction (SCXRD) experiments can prove prohibitively difficult. Three-dimensional electron diffraction (3DED) provides an alternative means for structure determination, enabling data collection from crystals of sub-micrometre size, which are too small to study by SCXRD. As such, 3DED is emerging as a valuable technique to explore a wide range of materials and is of particular interest to synthetic chemists studying small molecule organometallic compounds.

3D electron diffraction was implemented at the University of York and a data collection and processing workflow were established. 3DED was then utilised to determine the structures of a range of challenging small molecule organometallic complexes, exploring the possibilities and limitations of the technique. Specifically, 3DED was used to determine the structures of: (i) a beam and air sensitive σ-alkane species that was difficult to study via SCXRD (Chapter 4), (ii) bulky planar porphyrin complexes that could not be studied by SCXRD (Chapter 5), (iii) a series of manganese complexes and their precursor ligand where only a scarce quantity of material was available (Chapter 6), and (iv) palladium complexes derived directly from reaction mixtures, where further purification and recrystallisation had not been attempted (Chapter 7). Finally, this thesis also describes the identification and characterisation of a rare and previously undiscovered crystal form of a palladium complex (Chapter 7).