A set of bioinspired carbamoyl CNP pincer complexes are reported that are relevant to [Fe]-hydrogenase (Hmd). The dicarbonyl species [((CNPR2)-N-NH-P-NH)Fe(CO)(2)I] [R = Ph, 1; R = Pr-i, 2] undergoes ligand deprotonation, resulting in the dearomatized complexes of formulas [((CNPR2)-N-NH-P-N=)Fe(CO)(2)] (5 and 6). The crystal structure and H-1{P-31} NMR spectroscopy of the iodide-bound dearomatized species [Na(18-crown-6)]- [((CNPPh2)-N-NH-P-N=)Fe(CO)(2)I] (7) showed that the deprotonated moiety was the phosphoramine N(H) linkage. Separately, the monocarbonyl complexes [((CNPR2)-N-NH-P-NH)Fe(CO)(MeCN)(2)] (BF4) (8 and 9) synthesized, as well as deprotonated and dearomatized in similar fashion. Reactivity studies revealed that the parent dicarbonyl complexes require more forceful conditions for H-2 activation, compared with the monocarbonyl complexes. The ligand backbone was not found to participate in H-2 activation and H-2 -> hydride transfer to an organic substrate was not observed in either case. Density functional theory calculations revealed that the higher reactivity of the monocarbonyl complex in H-2 splitting could be attributed to its higher affinity for H-2. This behavior is attributed to two key points related to the requisite d(pi) (Fe) -> sigma*(H-2) back-bonding interaction in a conventional M-H, Kubas interaction: (i) generally, the weaker pi donor capacity of the dicarbonyls, and (ii) specifically, the detrimental effect of a strongly pi acidic CO ligand (versus weakly pi acidic MeCN ligand) trans to the H-2 activation site. The higher reactivity of the monocarbonyl complex is also evidenced by the catalytic transfer hydrogenation by monocarbonyl 8, whereas dicarbonyl 1 was ineffective. Overall, the results suggest that Nature uses the dicarbonyl motif in [Fe]-hydrogenase to diminish the interaction between the Fe center and dihydrogen, thereby preventing premature H-2 activation prior to substrate (H4MPT+) binding and any resulting nonspecific hydride transfer reactivity.