Structure/reactivity relationships and mechanism from X-ray data and spectroscopic kinetic analysis

The development in crystallography is nothing short of phenomenal, showing an ever increasing trend towards applications, such as in molecular biology. ‘Traditional’ small molecule chemical crystallography tends to, in many aspects, be considered as trivial due to the exponential growth in computing power and the parallel expansion in software. However, many dynamic processes (still) occur at the molecular level. Thus, the fundamental understanding of subtle nuances in structural behaviour, and the associated influence on other (kinetic) properties, is often trivialized when conclusions are simply made based on thermodynamic observations alone. This review aims to emphasize the importance of crystallography in small molecule chemistry by presenting detailed evaluations of two extended ‘case studies’, i.e. the first on structure and dynamics of the middle transition metal cyanide-oxido complexes, and the second on rhodium model homogeneous catalyst precursors. Both underline the fact of understanding the overarching principles of dynamics, i.e. time-resolved behaviour of processes, but considered from a structural perspective. The reference point is to focus on an integrated and overarching mechanistic approach, utilizing structural data, but in particular reaction kinetics, to obtain a more complete picture of processes or systems being evaluated.