Computational Methodology: The tmQM data set was generated by extracting structures from the 2020 release of the Cambridge Structural Database (CSD) using seven filters: 1) inclusion of only mononuclear transition metal (TM) compounds, 2) containing at least one carbon and one hydrogen, 3) excluding non-metal components, 4) omitting polymeric structures, 5) ensuring 3D coordinates, 6) excluding disordered atoms, and 7) removing highly charged species (charge outside -1 to +1). From the filtered CSD data, 116,332 structures were selected. After geometry optimization using the GFN2-xTB method, additional filters for convergence, geometry quality, and electron count reduced the dataset to 86,699 structures. Ultimately, quantum mechanical properties were computed using DFT with the hybrid meta-GGA TPSSh functional and the def2-SVP basis set through Gaussian 16.