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A study of the reversible CO2 fixation by a series of macrocyclic dicopper complexes is described. The dicopper macrocyclic complexes [Cu2(OH)2(Me2p)](CF3SO3)2, 1(CF3SO3)2, and [Cu2(μ-OH)2(Me2m)](CF3SO3)2, 2(CF3SO3)2, (Scheme 1) containing terminally bound and bridging hydroxide ligands, respectively, promote reversible inter- and intramolecular CO2 fixation that results in the formation of the carbonate complexes [{Cu2(Me2p)}2(μ-CO3)2](CF3- SO3)4, 4(CF3SO3)4, and [Cu2(μ-CO3)(Me2m)](CF3SO3)2, 5(CF3SO3)2. Under a N2 atmosphere the complexes evolve CO2 and revert to the starting hydroxo complexes 1 (CF3SO3)2 and 2(CF3SO3)2, a reaction the rate of which linearly depends on [H2O]. In the presence of water, attempts to crystallize 5(CF3SO3)2 afford [{Cu2(Me2m)(H2O)}2(μ-CO3)2}(CF3SO3)4, 6(CF3SO3)4, which appears to rapidly convert to 5(CF3SO3)2 in acetonitrile solution. [Cu2(OH)2-(H3m)]2+, 7, which contains a larger macrocyclic ligand, irreversibly reacts with atmospheric CO2 to generate cagelike [{Cu2(H3m)}2(μ-CO3)2](ClO4)4, 8(ClO4)4. However, addition of 1 equiv of HClO4 per Cu generates [Cu2(H3m)(CH3-CN)4]4+ (3), and subsequent addition of Et3N under air reassembles 8. The carbonate complexes 4(CF3SO3)4, 5(CF3SO3)2, 6(CF3SO3)4, and 8(ClO4)4 have been characterized in the solid state by X-ray crystallography. This analysis reveals that 4(CF3SO3)4, 6(CF3SO3)4, and 8(ClO4)4 consist of self-assembled molecular boxes containing two macrocyclic dicopper complexes, bridged by CO32- ligands. The bridging mode of the carbonate ligand is anti-anti-μ-η±:η± in 4(CF3SO3)4, anti-anti-μ-η²:η± in 6(CF3SO3)4 and ant-anti-μ-η²:η² in 5(CF3SO3)2 and 8(ClO4)4. Magnetic susceptibility measurements on 4(CF3SO3)4, 6(CF3SO3)4, and 8(ClO4)4 indicate that the carbonate Iigands mediate antiferromagnetic coupling between each pair of bridged CuII ions (J = -23.1, -108.3, and -163.4 cm-1, respectively, H = -JS1S2). Detailed kinetic analyses of the reaction between carbon dioxide and the macrocyclic complexes 1 (CF3SO3)2 and 2(CF3SO3)2 suggest that it is actually hydrogen carbonate formed in aqueous solution on dissolving CO2 that is responsible for the observed formation of the different carbonate complexes controlled by the binding mode of the hydroxy ligands.… [ABSTRACT FROM AUTHOR]

Two isomeric Ru(ll) complexes containing the dinucleating Hbpp (3,5-bis(2-pyridyl)pyrazole) ligand together with CI and dmso ligands have been prepared and their structural, spectroscopic, electrochemical, photochemical, and catalytic properties studied. The crystal structures of trans, cis-[Ru[sup II]CI[sub 2](Hbpp)(dmso)[sub 2]], 2a, and cis(out),cis-[Ru[sup II]Cl[sub 2](Hbpp)(dmso)[sub 2]], 2b, have been solved by means of single-crystal X-ray diffraction analysis showing a distorted octahedral geometry for the metal center where the dmso ligands coordinate through their S atom. 1D and 2D NMR spectroscopy corroborates a similar structure in solution for both isomers. Exposure of either 2a or 2b in acetonitrile solution under UV light produces a substitution of one dmso ligand by a solvent molecule generating the same product namely, cis(out)-[Ru[sup II[CI[sub 2](Hbpp)(MeCN)(dmso)], 4. While the 1 e[sup -] oxidation of 2b or cis(out),cis-[Ru[sup II]Cl[sub 2](bpp)(dmso)[sub 2]][sup +], 3b, generates a stable product, the same process for 2a or trans, cis-[R[sup II]Cl[sub 2](bpp)(dmso)[sub 2]][sup +], 3a, produces the interesting linkage isomerization phenomenon where the dmso ligand switches its bond from Ru-S to Ru-O (K[sup III, sub O→S] = 0.25 ± 0.025, k[sup III, sub O → S] = 0.017 s[sup -1], and k[sup III, sub S → O] = 0.065 s[sup -1] k[sup II, sub O → S] = 6.45 × 10[sup 9]. k[sup II, sub O → S] = 0.132 s[sup -1], k[sup II, sub S → O] = 2.1 × 10[sup -11] s[sup -1]). Finally complex 3a presents a relatively high activity as hydrogen transfer catalyst, with regard to its ability to transform acetophenone into 2-phenylethyl alcohol using 2-propanol as the source of hydrogen atoms. [ABSTRACT FROM AUTHOR]

The article discusses the ligand design discovered by T.J. Meyer which has oxidative properties and its redox potentials that contributes to its reactivity with substrates. It also reports on the disproportionation of its oxidation states which can provide a design for oxidation of organic substrates and energy conversion schemes.