Metal-Ligand-Cooperativity has been a key concept for the development of homogeneous catalyst for novel atom economic and sustainable reactions with molecular substrates in the last two decades. Recent advancements of such metal-ligand-cooperative catalysis particularly involve hydrogenation, dehydrogenation and dehydrogenative coupling reactions as well as hydrogen borrowing-type reactions. These important developments were also applied for the synthesis of polyesters and -amides by dehydrogenative coupling, as well as for alternative strategies for the recycling of polyester, -amides and -urethanes by hydrogenation (Fig. ), but the huge number of catalytic hydrogen borrowing type protocols in organic synthesis have never been applied to polymers (Fig. ), although this can potentially provide access to new types of polymeric materials and can be also used to tune the chemo-physical properties of the material.