Base metal catalysis is an emerging field in organometallic chemistry to replace precious metals by earth abundant metals. To achieve so, a suited ligand backbone to support the non-precious metals is needed, in order to get catalytic activity. The influence of well designed ligands on base metal chemistry is exampled on a series of iron(II) and manganese(II) compounds. The research bases on tridentate “pincer” ligands with a pyridine backbone connected with two phosphine donors (PNP-ligands). The ligands vary in the set-up of linkers (CH2, NH, NMe, O) and phosphine moiety PR2. A new class of iron(II) PNP pincer complexes, made up of two pincer ligands in different bonding modes (tridentate and bidentate) is described. The complexes of general formula 3,2-[Fe(PNP)2X]+ are only observed when small phosphines (PR2; R = Me, Et, nPr, nBu, Ph) and a NH linker is apparent in the PNP ligands. In solution, the formation is inevitable, even when altering the stoichiometry. The 31P The results suggest that bifunctionality of the ligand along with ligand-metal cooperation is essential for the mechanism. Turnover numbers (TON) of up to 10.000 could be achieved. The hydrogenation proceeds at room temperature, without additives in protic media. Analogue rhenium(I) PNP pincer complexes [Re(PNP)(CO)2H] had inferior performance below 100 TONs. Additionally, the hydrido complexes [Mn(PNP)(CO)2H] and [Re(PNP)(CO)2H] activate carbon dioxide (CO2) at ambient conditions. The 1,2-addition of CO2 leads to a series of formate complexes of the types [Mn(PNP)(CO)2(OCHO)] and [Re(PNP)(CO)2(OCHO)]. In summary, these results offer a guide for Mn(I) and Fe(II) pincer chemistry allowing to alter the chemical properties in a modular fashion.