Carbon dioxide (CO 2 ,acommon combustion pollutant) releasing continuously into the atmosphere is primarily responsible for the rising atmospheric temperature. Therefore, CO 2 sequestration has been an indispensable area of research for the past severald ecades. On the other hand, the concept of aromaticity is often employed in designing chemical reactions and metal-free frustratedL ewis pairs (FLPs) have proved ideal reagents to achieveC O 2 reduction. However,c onsidering FLP and aromaticity together is less developed in CO 2 capture. Here we report theoretical investigationsonthe aromaticity-promoted CO 2 activation,involving heterocyclopentadiene-bridged P/N-FLPs. The calculations revealt hat furan-and pyrrole-bridged P/N-FLPs can make CO 2 capture both thermodynamically and kinetically favorable (with activation energies of 5.4-7.7 kcal mol À1 )d ue to the aromatic stabilization of the transition states and products.O ur findings could open an avenue to the design of novel FLPs for CO 2 capture.

Theoretical calculations reveal significant substituent and aromaticity effects on Fe(iii)-catalyzed carbonyl–olefin metatheses of hexadienals.

Treatment of [Ir(PPh 3 ) 3 Cl] with 2-[5-(pyridin-2-yl)-1H-pyrrol-2-yl]pyridine (Hdpp) in refluxing toluene affords an unexpected pyrrole-metalated iridium(III) hydride complex, [Ir(K 2 C,N -dpp)(H)(Cl)(PPh 3 ) 2 ] (1), via C pyrrole −H activation, while the presence of the base KO t Bu as the deprotonation reagent produces a pyridine-metalated iridium(III) hydride complex, [Treatment of [Ir(PPh 3 ) 3 Cl] prepared by a convenient method with Hdpp in the presence of KO t Bu under the refluxing mixture solvent toluene/methanol (2:1, v/v) generates the N,N-chelating complex [Ir(K 2 N,N -dpp)(H)(Cl)(PPh 3 ) 2 ] (3) together with 1 and the N,N-chelating dihydride complex [Ir(K 2 N,N -dpp)(H) 2 (PPh 3 ) 2 ] (4). Complex 4 is also readily produced by the reaction of [Ir(PPh 3 ) 3 Cl] and Hdpp in the presence of KO t Bu under refluxing methanol or by the reaction of IrCl 3 and PPh 3 in refluxing 2-ethoxyethanol. Complexes 1−4 are fully characterized by NMR, IR, and UV−vis spectroscopy and X-ray diffraction analysis. The dpp − /dpp 2− ligand shows rich coordination capability, of which pyridine-and pyrrole-cyclometalated coordination modes are first reported. The formation of structural isomers 1 and 3 involved the selective activation of the C−H and N−H bonds of Hdpp is rationalized by theoretical calculations.