Coordination of N,N' bidentate ligands aryl-pyridin-2-ylmethyl-amine ArNH-CH2-2-C5H4N 1 (Ar = 4-CH3-C6H4, 1a; 4-CH3O-C6H4, 1b; 2,6-(CH3)2-C6H3, 1c; 4-CF3-C6H4, 1d) to the moieties [Ru(bipy)2]2+, [Ru(eta5-C5H5)L]+ (L = CH3CN, CO), or [Ru(eta6-arene)Cl]2+ (arene = benzene, p-cymene) occurs under diastereoselective or diastereospecific conditions. Detailed stereochemical analysis of the new complexes is included. The coordination of these secondary amine ligands activates their oxidation to imines by molecular oxygen in a base-catalyzed reaction and hydrogen peroxide was detected as byproduct. The amine-to-imine oxidation was also observed under the experimental conditions of cyclic voltammetry measurements. Deprotonation of the coordinated amine ligands afforded isolatable amido complexes only for the ligand (1-methyl-1-pyridin-2-yl-ethyl)-p-tolyl-amine, 1e, which doesn't contain hydrogen atoms in a beta position relative to the N-H bond. The structures of [Ru(2,2'-bipyridine)2(1b)](PF6)2, 2b; [Ru(2,2'-bipyridine)(2)(1c)](PF6)2, 2c; trans-[RuCl2(COD)(1a)], 3; and [RuCl2(eta6-C6H6)(1a)]PF6, 4a, have been confirmed by X-ray diffraction studies.

The complexes [MCl(2)(kappa2-N approximately N')] (N approximately N' = 2-C(5)H(4)N-CH2-NHAr; Ar = 4-MeC(6)H(4), a; 2,6-Me(2)C(6)H(3), b; 4-MeOC(6)H(4), c; 4-CF(3)C(6)H(4), d; M = Pd, 1a-d; Pt, 2a-d) have been prepared and fully stereochemically characterized both in the solid state and in solution. Their behavior in DMSO-d6 solution is dependent on the substituents of the aryl group and on the metal. Complexes of palladium with substituents at the para position (1a, 1c, 1d) display a dynamic 1H NMR pattern when the solutions are heated. An enantiomeric exchange Slambda/Rdelta is suggested to explain such behavior. On the basis of the calculated negative DeltaS values, an associative mechanism involving the solvent is proposed. Under the same conditions, analogous complexes of platinum (2a, 2c, 2d) proved to be unstable, and release of the N approximately N' ligand was observed. Complexes 1b and 2b show temperature-variable 1H NMR spectra without any evidence accounting for enantiomeric exchange or decoordination. DFT calculations on models of 1a and 1b show that diastereomeric exchange Sdelta/Slambda is a process where the complex with the higher sterical hindrance, 1b, has a lower energy barrier.

Silica nanomaterials generate a permanent and strongly fluorescent response in a vapour flow of the improvised explosive triacetone triperoxide (TATP).

The reaction of the complex [Pd(κ3‐NN′O)CH3] [NN′O = 2‐Py‐CH=N‐(o‐C6H4)O–] (1a) with nitromethane affords a mixture of 2a and 2b. In this reaction methylation of the ligand takes place. These complexes display exchange equilibrium in solution. The methylation reaction is proposed to occur through nucleophilic attack of the nitronate anion on the iminic carbon atom. DFT calculations are presented in order to support a part of the mechanism and these calculations show that the participation of water in the migration of a proton is important. The crystal structure of the derivative productafter spontaneous release of methane (3) is presented as well. Attempts to extend the reaction to other nitroalkanes resulted in a mixture of complexes that was not easy to characterize. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

New cis-(1,2-azole)-aquo bis­(2,2′-bipyridyl)­ruthenium­(II) (1,2-azole (az*H) = pzH (pyrazole), dmpzH (3,5-dimethylpyrazole), and indzH (indazole)) complexes are synthesized via chlorido abstraction from cis-[Ru­(bipy)2Cl­(az*H)]­OTf. The latter are obtained from cis-[Ru­(bipy)2Cl2] after the subsequent coordination of the 1,2-azole. All the compounds are characterized by 1H, 13C, 15N NMR spectroscopy as well as IR spectroscopy. Two chlorido complexes (pzH and indzH) and two aquo complexes (indzH and dmpzH) are also characterized by X-ray diffraction. Photophysical and electrochemical studies were carried out on all the complexes. The photophysical data support the phosphorescence of the complexes. The electrochemical behavior of all the complexes in an Ar atmosphere indicate that the oxidation processes assigned to Ru­(II) → Ru­(III) occurs at higher potentials in the aquo complexes. The reduction processes under Ar lead to several waves, indicating that the complexes undergo successive electron-transfer reductions that are centered in the bipy ligands. The first electron reduction is reversible. The electrochemical behavior in CO2 media is consistent with CO2 electrocatalyzed reduction, where the values of the catalytic activity [i cat(CO2)/i p(Ar)] ranged from 2.9 to 10.8. Controlled potential electrolysis of the chlorido and aquo complexes affords CO and formic acid, with the latter as the major product after 2 h. Photocatalytic experiments in MeCN with [Ru­(bipy)3]­Cl2 as the photosensitizer and TEOA as the electron donor, which were irradiated with >300 nm light for 24 h, led to CO and HCOOH as the main reduction products, achieving a combined turnover number (TONCO+HCOO– ) as high as 107 for 2c after 24 h of irradiation.

Considering the interest in processes related to hydrogen storage such as CO2 hydrogenation and formic acid (FA) decomposition, we have synthesized a set of Ir, Rh, or Ru complexes to be tested as versatile precatalysts in these reactions. In relation with the formation of H2 from FA, the possible applicability of these complexes in the transfer hydrogenation (TH) of challenging substrates as quinoline derivatives using FA/formate as hydrogen donor has also been addressed. Bearing in mind the importance of secondary coordination sphere interactions, N,N′ ligands containing NH2 groups, coordinated or not to the metal center, were used. The general formula of the new complexes are [(p-cymene)­RuCl­(N,N′)]­X, X = Cl–, BF4 – and [Cp*MCl­(N,N′)]­Cl, M = Rh, Ir, where the N,N′ ligands are 8-aminoquinoline (HL1), 6-pyridyl-2,4-diamine-1,3,5-triazine (L2) and 5-amino-1,10-phenanthroline (L3). Some complexes are not active or catalyze only one process. However, the complexes [Cp*MCl­(HL1)]Cl with M = Rh, Ir are versatile catalysts that are active in hydrogenation of quinolines, FA decomposition, and also in CO2 hydrogenation with the iridium derivative being more active and robust. The CO2 hydrogenation takes place in mild conditions using only 5 bar of pressure of each gas (CO2 and H2). The behavior of some precatalysts in D2O and after the addition of 9 equiv of HCO2Na (pseudocatalytic conditions) has been studied in detail and mechanisms for the FA decomposition and the hydrogenation of CO2 have been proposed. For the Ru, Ir, or Rh complexes with ligand HL1, the amido species with the deprotonated ligand are observed. In the case of ruthenium, the formate complex is also detected. For the iridium derivative, both the amido intermediate and the hydrido species have been observed. This hydrido complex undergoes a process of umpolung D+↔ Ir–D. All in all, the results of this work reflect the active role of −NH2 in the transfer of H+.

Speciation of Hg2+ and MeHg+ has been achieved by in vitro approaches with fluorogenic probes supported in cultured cells.

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