We have developed conceptually novel titanium- and zirconium-catalyzed reductive transformations for the construction and cleavage of carbon-carbon and carbon-heteroatom bonds in organic molecules. Within this project, we will investigate the mechanism of these transformations using state-of-the-art DFT-calculations. This will comprise the computation of reaction pathways including relevant intermediates and transition states based on low-valent titanium and zirconium hydride species. Reaction examples that will be investigated are titanium(III) catalyzed decyanations and desulfonylations as well as zirconium hydride catalyzed ring-openings, silylations, and carbon-heteroatom cleavages.