Reactions of carbon dioxide with a set of planar complexes [NiII(pyN2R2)(OH)]1- derived from N,N'-(2,6-C6H3R2)2-2,6-pyridinedicarboxamidate(2-) pincer ligands are described. Reactions are characterized by second-order kinetics (rate = k2[NiII][CO2]) with k2 = 104-106 M-1s-1 (DMF. 298 K), small decreses in k2 with increasing substituent R size, negative activation entropies, and afford product bicarbonate complexes [NiII(pyN2R2)(HCO3)]1- with ?1-OCO2H ligation. A reaction pathway is proposed based on DFT computations of the enthalpic reaction profiles for systems with R = Me and Pri. To approximate the reactive site in Ni-Fe carbon monoxide dehydrogenase, binucleating macrocycles have been prepared that bind NiII in a pincer ligand Ni3 environment and FeII in a triamine N3 or triamine-thioether N3S site. The syntheses of the macrocycles and their complexes will be presented together with reactivity properties involving CO2 and other relevant substrates.

Rapid carbon dioxide fixation reactions modulated by mononuclear nickel(II) and related reactions by approximations of the binuclear nickel(II)-iron(II) center of carbon monoxide dehydrogenase

243rd National Meeting (2012)

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