ИСТИНА

The design of well-defined Mn(I) catalysts for (de)hydrogenation-type processes became one of the most popular directions in homogeneous catalysis using Earth abundant transition metals. Despite the Mn-based catalytic systems with pincer-type ligands are the most studied, the octahedral complexes with less structurally elaborated bidentate ligands could be competitive in terms of catalytic activity and/or substrate scope. It is admitted that hydride species fac-[(L−L')Mn(CO)3H] are important intermediates in hydrogenation processes and the occurrence of a direct hydride attack across the polar C=X bonds with a prior formation of non-covalent adducts was confirmed by DFT calculations. In this work we report about the first experimental evidence that the hydride transfer process for such catalytically relevant facial Mn(I) complexes could be facilitated by their transient isomerization into the elusive meridional species mer-[(L−L')Mn(CO)3H].