The recombination of CHF2 and C2D5 radicals was used to produce CD3CD2CHF2* molecules with 96 kcal mol(-1) of vibrational energy in a room temperature bath gas. The formation of CD3CD═CHF and CD3CD═CDF was used to identify the 1,2-DF and 1,1-HF unimolecular elimination channels; CD3CD═CDF is formed by isomerization of the singlet-state CD3CD2CF carbene. The total unimolecular rate constant is 1.6 × 10(6) s(-1), and the branching ratio for 1,1-HF elimination is 0.25. Threshold energies of 64 ± 2 and 73 ± 2 kcal mol(-1) were assigned to the 1,2-DF and 1,1-HF reaction channels. The E and Z isomers of 1-fluoropropene were observed for each reaction; approximately 30% of the CD3CD═CDF molecules derived from 1,1-HF elimination retained enough energy to undergo cis-trans isomerization. Electronic structure calculations with density-functional theory were used to characterize the transition-state structures and the H atom migration barrier for CD3CD2CF. Adjustment of the rate constants to account for kinetic-isotope effects suggest that the branching ratio would be 0.20 for 1,1-HF elimination from C2H5CHF2. The results from an earlier study of CD3CHF2 and CH3CHF2 are also reinterpreted to assign a threshold energy of 74 kcal mol(-1) for the 1,1-HF elimination reaction. Because CHF2CHF2* is generated in the photolysis system, the 1,1-and 1,2-HF-elimination reactions of CHF2CHF2* are discussed. The 1,1-HF channel was identified by trapping the CF2HCF carbene with cis-butene-2.

Metal–organic frameworks (MOFs) have received a great deal of attention for their potential in atmospheric filtering, and recent work has shown that catecholate linkers can bind metals, creating MOFs with monocatecholate metal centers and abundant open coordination sites. In this study, M–catecholate systems (with M = Mg2+, Sc2+, Ti2+, V2+, Cr2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+) were used as computational models of metalated catecholate linkers in MOFs. Nitric oxide (NO) is a radical molecule that is considered an environmental pollutant and is toxic if inhaled in large quantities. Binding NO is of interest in creating atmospheric filters, at both the industrial and personal scale. The binding energies of NO to the metal–catecholate systems were calculated using density functional theory (DFT) and complete active space self-consistent field (CASSCF) followed by second-order perturbation theory (CASPT2). Selectivity was studied by calculating the binding energies of additional guests (CO, NH3, H2O, N2, and CO2). The toxic guests have stronger binding than the benign guests for all metals studied, and NO has significantly stronger binding than other guests for most of the metals studied, suggesting that metal–catecholates are worthy of further study for NO filtration. Certain metal–catecholates also show potential for separation of N2 and CO2 via N2 activation, which could be relevant for carbon capture or ammonia synthesis.

The affinities and selectivities of lanthanide complexes with open coordination sites for anions vary considerably with the chelate. In order to determine the effect of the stability of a lanthanide complex on its affinity for anions, five different complexes featuring different bidentate chelating moieties were synthesized, and their affinity for anions in water at neutral pH were evaluated by longitudinal relaxometry measurements. The chelates comprise both oxygen and nitrogen donors including maltol, 1,2-hydroxypyridinone, hydroxamic acid, pyridin-2-ylmethanol, and carbamoylmethylphosphonate diester. They were chosen to span a range of basicities all the while maintaining a similar tripodal tris-bidentate architecture, thereby allowing for a direct study of the role of the coordinating motif on the supramolecular recognition of anions by the corresponding Gd III complex. Overall, for ligands containing the same number of protonation steps, and therefore the same charge at neutral pH, the lower the acidity of the chelate (higher ∑pK a 's), the less stable the corresponding Gd III complex, and the higher its affinity for anions. Regardless of the number of protonation steps, the more stable Gd III complexes form ternary or quaternary assemblies with coordinating anions. In contrast, the same anions readily displace the chelate of the least stable complexes, resulting instead in the formation of Gd III •anion precipitates. Irrespective of the chelate, in the absence of steric hindrance at the open coordination site, the affinity of Gd III complexes for anions follows the order phosphate > arsenate > bicarbonate > fluoride. Hence, the selectivity and affinity of Gd III complexes of tripodal tris-bidentate chelates for anions is a function of the stability of the Gd III complex and the basicity of the anion.

Simple Ti imido halide complexes such as [Br2Ti­(N t Bu)­py2]2 are competent catalysts for the synthesis of unsymmetrical carbodiimides via Ti-catalyzed nitrene transfer from diazenes or azides to isocyanides. Both alkyl and aryl isocyanides are compatible with the reaction conditions, although product inhibition with sterically unencumbered substrates sometimes limits the yield when diazenes are employed as the oxidant. The reaction mechanism has been investigated both experimentally and computationally, wherein a key feature is that the product release is triggered by electron transfer from an η2-carbodiimide to a Ti-bound azobenzene. This ligand-to-ligand redox buffering obviates the need for high-energy formally TiII intermediates and provides further evidence that substrate and product “redox noninnocence” can promote unusual Ti redox catalytic transformations.

Cp 2 Ti(κ 2t BuNCN t Bu): a Complex With an Unusual κ 2