We introduce a new family of complexes of general formula [

We have prepared three new dinuclear ruthenium complexes having the formulas [Ru2II(bpp)(trpy)2(mu-L)]2+ (L = Cl, 1; L = AcO, 2) and [Ru2II(bpp)(trpy)2(H2O)2]3+ (3). The three complexes have been characterized through the usual spectroscopic and electrochemical techniques and, in the cases of 1 and 2, the X-ray crystal structures have been solved. In aqueous acidic solution, the acetato bridge of 2 is replaced by aqua ligands, generating the bis(aqua) complex 3 which, upon oxidation to its RuIVRuIV state, has been shown to catalytically oxidize water to molecular oxygen. The measured pseudo-first-order rate constant for the O2-evolving process is 1.4 x 10-2 s-1, more than 3 times larger than the higher one previously reported for Ru-O-Ru type catalysts. This new water-splitting catalyst also has improved stability with regard to any previously described, achieving a total of 18.6 metal cycles.

A new family of tetra-anionic tetradentate amidate ligands, N1,N1'-(1,2-phenylene)bis(N2-methyloxalamide) (H4L1), and its derivatives containing electron-donating groups at the aromatic ring have been prepared and characterized, together with their corresponding anionic Cu(II) complexes, [(LY)Cu](2-). At pH 11.5, the latter undergoes a reversible metal-based III/II oxidation process at 0.56 V and a ligand-based pH-dependent electron-transfer process at 1.25 V, associated with a large electrocatalytic water oxidation wave (overpotential of 700 mV). Foot-of-the-wave analysis gives a catalytic rate constant of 3.6 s(-1) at pH 11.5 and 12 s(-1) at pH 12.5. As the electron-donating capacity at the aromatic ring increases, the overpotential is drastically reduced down to a record low of 170 mV. In addition, DFT calculations allow us to propose a complete catalytic cycle that uncovers an unprecedented pathway in which crucial O-O bond formation occurs in a two-step, one-electron process where the peroxo intermediate generated has no formal M-O bond but is strongly hydrogen bonded to the auxiliary ligand.

We have found the first reaction of direct cupration of fluoroform, the most attractive CF(3) source for the introduction of the trifluoromethyl group into organic molecules. Treatment of CuX (X = Cl, Br, I) with 2 equiv of MOR (M = K, Na) in DMF or NMP produces novel alkoxycuprates that readily react with CF(3)H at room temperature and atmospheric pressure to give CuCF(3) derivatives. The CuCl and t-BuOK (1:2) combination provides best results, furnishing the CuCF(3) product within seconds in nearly quantitative yield. As demonstrated, neither CF(3)(-) nor CF(2) mediate the Cu-CF(3) bond formation, which accounts for its remarkably high selectivity. The fluoroform-derived CuCF(3) solutions can be efficiently stabilized with TREAT HF to produce CuCF(3) reagents that readily trifluoromethylate organic and inorganic electrophiles in the absence of additional ligands such as phenanthroline. A series of novel Cu(I) complexes have been structurally characterized, including K(DMF)[Cu(OBu-t)(2)] (1), Na(DMF)(2)[Cu(OBu-t)(2)] (2), [K(8)Cu(6)(OBu-t)(12)(DMF)(8)(I)](+) I(-) (3), and [Cu(4)(CF(3))(2)(C(OBu-t)(2))(2)(μ(3)-OBu-t)(2)] (7).

A thorough characterization of the Ru-Hbpp (in,in-{[Ru(II)(trpy)(H(2)O)](2)(mu-bpp)}(3+) (trpy is 2,2':6',2''-terpyridine, bpp is bis(2-pyridyl)-3,5-pyrazolate)) water oxidation catalyst has been carried out employing structural (single crystal X-ray), spectroscopic (UV-vis and NMR), kinetic, and electrochemical (cyclic voltammetry) analyses. The latter reveals the existence of five different oxidation states generated by sequential oxidation of an initial II,II state to an ultimate, formal IV,IV oxidation state. Each of these oxidation states has been characterized by UV-vis spectroscopy, and their relative stabilities are reported. The electron transfer kinetics for individual one-electron oxidation steps have been measured by means of stopped flow techniques at temperatures ranging from 10 to 40 degrees C and associated second-order rate constants and activation parameters (DeltaH() and DeltaS()) have been determined. Room-temperature rate constants for substitution of aqua ligands by MeCN as a function of oxidation state have been determined using UV-vis spectroscopy. Complete kinetic analysis has been carried out for the addition of 4 equiv of oxidant (Ce(IV)) to the initial Ru-Hbpp catalyst in its II,II oxidation state. Subsequent to reaching the formal oxidation state IV,IV, an intermediate species is formed prior to oxygen evolution. Intermediate formation and oxygen evolution are both much slower than the preceding ET processes, and both are first order with regard to the catalyst; rate constants and activation parameters are reported for these steps. Theoretical modeling at density functional and multireference second-order perturbation theory levels provides a microscopic mechanism for key steps in intermediate formation and oxygen evolution that are consistent with experimental kinetic data and also oxygen labeling experiments, monitored via mass spectrometry (MS), that unambiguously establish that oxygen-oxygen bond formation proceeds intramolecularly. Finally, the Ru-Hbpp complex has also been studied under catalytic conditions as a function of time by means of manometric measurements and MS, and potential deactivation pathways are discussed.

The preparation of three series of [(NHC)CuX] complexes (NHC = N-heterocyclic carbene, X = Cl, Br, or I) is reported. These syntheses are high yielding and only use readily available starting materials. The prepared complexes were spectroscopically and structurally characterized. Notably, two of them present a bridging NHC ligand between two copper centers in the solid state, an extremely rare coordination mode for these ligands. These complexes were then applied to two distinct organic reactions: the hydrosilylation of ketones and the 1,3-dipolar cycloaddition of azides and alkynes. In both transformations, outstanding catalytic systems were found for preparing the corresponding products in excellent yields and short reaction times. Most remarkably, the screening of well-defined systems in the hydrosilylation reaction allowed for the identification of a pre-catalyst previously overlooked since, originally, catalytic species were in situ generated. Under such conditions, major formation of [(NHC)(2)Cu](+) species, inactive in this reduction reaction, occurred instead of the expected copper hydride. These results highlight one of the most important advantages of employing well-defined complexes in catalysis: gaining an improved control of the nature of the catalytically relevant species in the reaction media.

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An iron(III) amine triphenolate complex, [FeTPhOA]2, able to efficiently catalyze the cycloaddition of carbon dioxide to a range of terminal epoxides under mild conditions, is described. In addition, it has also been found that the complex is able to catalyze the conversion with more sterically congested oxiranes and oxetanes which are generally considered challenging substrates to activate. Variation of the co‐catalyst, required for ring‐opening of the substrates, has also been examined. The results show that terminal epoxide substrates are converted more efficiently with an iodide co‐catalyst, whereas more bulky oxirane substrates give better product yields in the presence of a bromide co‐catalyst. The combined results demonstrate the broad applicability of these iron(III) complexes in this type of carbon dioxide fixation chemistry.