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Cohesion in Coordination Chemistry

Subject Area Theoretical Chemistry: Molecules, Materials, Surfaces
Inorganic Molecular Chemistry - Synthesis and Characterisation
Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
Term from 2014 to 2018
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 258769765
 
Final Report Year 2019

Final Report Abstract

The main intention of this project was to study the issue of cohesion in transition metal coordination chemistry. The development of a generally valid, easy applicable and computational feasible protocol for computing thermochemical properties of closed-shell transition metal compounds in solution was a primary objective of the project. A specific aspect focused on the application of WFT and DFT methods to the investigation of the concept of hemichelation, the evaluation of its energetics and the fine analysis of the noncovalent bonding scheme in order to determine the dominating factors of their stability. As a result of this project an in-depth investigation of the “trans–cis C–Pd–C rearrangement in hemichelates” is presented, revealing new insights of the mechanism of isomerization unique to this class of molecules. This study combined with the results of the MOR41 benchmark study and the research performed during the cooperation led to the proposal of a revised, generally applicable and accurate scheme for the calculation of transition metal thermochemistry. Additional focus was put on the accurate description of the thermochemistry of model reactions and its reproduction by theoretical methods which constitute an essential effort to provide physically correct pictures of the energetics of transition metal chemistry reactions. We introduced the MOR41 benchmark set consisting of 41 closed-shell organometallic reactions resembling many important chemical transformations commonly used in transition metal chemistry and catalysis. It includes significantly larger molecules than presented in other transition metal test sets and covers a broad range of bonding motifs. The utilized DLPNO-CCSD(T) protocol turned out to be a viable reference method for this purpose, since the estimated uncertainty of the respective reaction energies is only approximately 2 kcal/mol. The MOR41 benchmark features a benchmark study assessing many state-of-the art density functional methods, and is already used and referenced by other researchers among the field. The results of this study could also significantly influence the development of the improved D4 dispersion correction, which in turn has found its way back into our revised protocol. Further work will continue to expand this protocol in order to be able to calculate transition states and thus reaction kinetics in solution accurately and with reasonable effort in the future. The publication of another benchmark set related to single-reference open-shell systems called ROST is also in progress.

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