El conocimiento de los electrones determina la interacción molecular

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In honour of the 70th birthday of Professor Luis A. Oro

EssayWhen Professor Luis Oro turns over the middle of June, he will be 70 years old, and he will be completing a cycle of almost half a century (48 years) dedicated to chemical research in the field of organometallics and homogeneous catalysis, and in general to the development of chemistry. In this aim, he has assumed different and complementary responsibilities, from leading innovative research projects, to the formation of professional scientists for academia or the chemical industry, from the direction of the Spanish Royal Society of Chemistry, to that of diverse editorial management consortia or even having taken the responsibility of guiding the overall Spanish scientific policy. It has been a long trek done with tons of enthusiasm, excellent companions and plenty of generosity. It is our pleasure and privilege to walk around the main steps of Professor Oro’s life; a life dedicated to investigate and to work to situate chemical research, and science in general, in the proper place it should be in our modern society.Peer Reviewe

Asymmetric 1, 3-dipolar cycloaddition reactions between methacrylonitrile and nitrones catalysed by well-defined M(diphosphane) (M=Rh, Ir) complexes

The cationic half-sandwich aqua-complexes (¿ 5-C5Me5)M(PP*)(H2O)]SbF6]2 M=Rh, Ir; PP* =(R)-Benphos, (R)-Cyphos, (2R, 4R)-Norphos] catalyse the 1, 3-dipolar cycloaddition reaction of nitrones with methacrylonitrile with perfect regioselectivity, low-to-perfect endo-selectivity and low-to-moderate enantioselectivity. The active species involved in the catalytic process, (¿ 5-C5Me5)M(PP*)(methacrylonitrile)]SbF6]2, have been isolated and characterised as mixtures of the (S)- and (R)-at-metal epimers. NMR measurements of these mixtures indicated that the (R M)-isomers epimerise to the corresponding (S M) counterparts. The molecular structure of the rhodium complex (S Rh, R C)-(¿ 5-C5Me5)Rh((R)-Benphos)(methacrylonitrile)]SbF6]2 has been determined by X-ray diffraction methods. Diastereomerically pure (S Rh, R C)-(¿ 5-C5Me5)Rh(PP*)(methacrylonitrile)]SbF6]2 compounds catalyse stoichiometrically the above mentioned dipolar cycloaddition reaction with up to 90% enantiomeric excess, thus indicating the influence of the metal handedness on the catalytic stereochemical outcome. Catalysts can be recycled up to three times without a significant loss of either activity or selectivity

Synthesis and catalytic activity of well-defined Co(i) complexes based on NHC–phosphane pincer ligands

A new methodology for the preparation of Co(I)–NHC (NHC = N-heterocyclic carbene) complexes, namely, [Co(PCNHCP)(CO)2][Co(CO)4] (1) and [Co(PCNHCP)(CO)2]BF4 (2), has been developed (PCNHCP = 1,3-bis(2-(diphenylphosphanyl)ethyl)-imidazol-2-ylidene). Both complexes can be straightforwardly prepared by direct reaction of their parent imidazolium salts with the Co(0) complex Co2(CO)8. Complex 1 efficiently catalyses the reductive amination of furfural and levulinic acid employing silanes as reducing agents under mild conditions. Furfural has been converted into a variety of secondary and tertiary amines employing dimethyl carbonate as the solvent, while levulinic acid has been converted into pyrrolidines under solventless conditions. Dehydrocoupling of the silane to give polysilanes has been observed to occur as a side reaction of the hydrosilylation process

The C form of n-hexadecanoic acid

3 pages, 2 tables, 2 figures.In the crystal structure of the title compound, C16H32O2, the molecules are arranged into dimers through O-HO hydrogen bonds. These dimers are packed in bilayers with terminal methyl groups at both external faces, and these layers are parallel to the crystallographic (100) plane. All C-C bonds of the alkyl chain show an antiperiplanar (trans) conformation, with slight deviations from the ideal value in the C-C bonds close to the intermolecular hydrogen bonds. The similarity between the carboxyl C-O bond distances is consistent with the existence of cis-trans tautomerism.This research was supported through CICYT grant No. MAT2001±3352 and DGICYT grant No. BQU2002±1729.Peer reviewe

Cyclopentadienyl iron dicarbonyl styrene chalcogenosulfonates: synthesis and structure of CpFe(CO)(2)SeSO2CH=CHPh

In this contribution, we report the preparation of iron thiosulfonato complex CpFe(CO)(2)SSO2CH=CHPh (1) and its selenosulfonato analogue CpFe(CO)(2)SeSO2CH=CHPh (2) featuring styrene moiety. 1 and 2 are obtained by electrophilic attack of (mu-E-x)CpFe(CO)(2)](2) (E = S; x = 2-4, E = Se; x = 1) on the sulfur atom of styrene sulfonyl chloride ClSO2CH=CHPh. The new compounds, 1 and 2 have been characterized by elemental analyses, IR, H-1-, C-13{H-1}-NMR, UV-Vis spectroscopy and the structure of 2 is determined by X-ray crystallography

Tetranuclear [Rh4(μ-PyS2) 2(diolefin)4] complexes as building blocks for new inorganic architectures: Synthesis of coordination polymers and heteropolynuclear complexes with electrophilic d8 and d10 metal fragments

The reaction of [Rh4(μ-PyS2)2(cod) 4] (PYS2 = 2,6-pyridinedithiolate, cod = 1,5-cyclooctadiene) with CF3SO3Me gave the cationic complex [Rh4(μ-PyS2Me)2(cod) 4][CF3SO3]2 (1) with two 6-(thiomethyl)pyridine-2-thiolate bridging ligands from the attack of Me+ at the terminal sulfur atoms of the starting material. Under identical conditions [Rh4(μ-PyS2)2(tfbb)4] (tfbb = tetrafluorobenzobarrelene) reacted with CF3SO3Me to give the mixed-ligand complex [Rh4(μ-PyS2)(μ-PyS 2Me)(tfbb)4][CF3SO3] (2). The nucleophilicity of the bridging ligands in the complexes [Rh4(μ -PyS2)2(diolefin)4] was exploited to prepare heteropolynuclear species. Reactions with [Au(PPh3)(Me 2CO)][ClO4] gave the hexanuclear complexes [(PPh 3)2Au2Rh4(μ-PyS2) 2(diolefin)4][ClO4]2 (diolefin = cod (3), tfbb (4)). The structure of 4, solved by X-ray diffraction methods, showed the coordination of the [Au(PPh3)]+ fragments to the peripheral sulfur atoms in [Rh4(μ-PyS2) 2(diolefin)4 along with their interaction with the neighbor rhodium atoms. Neutral coordination polymers of formula [CIMRh 4(μ-PyS2)2(diolefin)4] n (M = Cu (5, 6), Au (7)) result from the self-assembly of alternating [Rh4(μ-PyS2)2(diolefin) 4] ([Rh4]) blocks and MCI linkers. The formation of the infinite polymetallic chains was found to be chiroselective for M = Cu; one particular chain contains exclusively homochiral [Rh4] complexes. Cationic heterometallic coordination polymers of formula [MRh 4(μ-PyS2)2(diolefin)4] n (M = Ag (8, 9), Cu (10, 11)) and [Rh5(μ-PyS 2)2(diolefin)5]n[BF 4]n (12, 13) result from the reactions of [Rh 4] with [Cu(CH3CN)4]BF4, AgBF 4, and [Rh(diolefin)(Me2CO)2]BF4, respectively. The heterometallic coordination polymers exhibit a weak electric conductivity in the solid state in the range (1.2-2.8) × 10-7 S cm-1.The financial support from Ministerio de Ciencia y Tecnología (MCyT(DGI)/FEDER, Projects BQU2002-00074 and BQU2000-1170) is gratefully acknowledged.Peer Reviewe

Rhodium(I) complexes with hemilabile phosphines: Rational design for efficient oxidative amination catalysts

13 páginas, 10 figuras, 6 tablas, 4 esquemas.A series of cationic square-planar rhodium(I) complexes of type [Rh(cod){Ar2P(CH2)nZ}]+, [Rh(cod){Ar2P(CH2)nZ}2]+, and [Rh{Ar2P(CH2)nZ}2]+, which contained diverse functionalized hemilabile phosphine ligands of type Ar2P(CH2)nZ (n=1–3; Z=OMe, OEt, OnBu, NMe2, SMe), were synthesized and spectroscopically characterized. The crystal structures of representative compounds were determined by X-ray diffraction. Most complexes were active catalysts for the anti-Markovnikov oxidative amination of styrene with piperidine to produce (E)-1-styrylpiperidine. Catalyst screening showed a remarkable relationship between the hemilabile ligand, the precatalyst structure, and the catalytic activity. The more-efficient catalysts were those that had arylphosphine ligands with a 2-alkoxyethyl- or 3-alkoxypropyl hemilabile moiety, Ar2P(CH2)nOR (n=2, 3; R=Me, Et, nBu). This study has revealed the outstanding catalytic activity of bis-phosphine complexes [Rh{(4-R-C6H4)2P(CH2)3OEt}2][PF6] (R=H, Me, OMe), with unprecedented turnover frequencies of up to 80 h−1 (R=Me) and excellent enamine selectivity (96 %).Financial support from the Ministerio de Ciencia e Innovación (MICINN/FEDER): CTQ2010-15221, MULTICAT (CSD2009-00050), and Factoría de Cristalización (CSD2006-0015) is gratefully acknowledged. M.I.B. thanks the Spanish MICINN and the IUCH (Instituto Universitario de Catálisis Homogénea) for a predoctoral fellowship.Peer reviewe

Heterolytic H2 activation on a carbene-ligated rhodathiaborane promoted by isonido-nido cage opening

A new mechanism of H2 activation is reported to occur on a carbene-ligated rhodathiaborane that features metal-thiaborane bifunctional synergistic effects. The key is the creation of vacant coordination sites by an isonido-nido structural transformation leading to the heterolytic H-H bond splitting. © 2013 The Royal Society of Chemistry.We gratefully acknowledge the Spanish Ministry of Science and Innovation (CTQ2009-10132, CSD2009-00050, and CSD2006-0015, CTQ2012-35665) for financial support. B.C. thanks the ‘‘Diputación General de Aragón’’ for a pre-doctoral scholarship.Peer Reviewe

Synthesis of tetranuclear rhodium and iridium complexes directed by 6-mercaptopyridin-2-ol: Electrochemical behavior, chemical oxidation, and coordination chemistry

The new ligand 6-mercapto-2(1 H)-pyridone (H2PySO) has been prepared in good yield by reaction of 6-chloro-pyridin-2-ol with NaSH. Reaction of the salt K2PySO, generated in situ, with the appropriate complex [M(μ-C1)(diolefin)]2affords the tetranuclear complexes [M 4(μ-PySO)2(diolefin)4] [M = Rh, diolefin = 1,5-cyclooctadiene (cod) (1), tetrafluorobenzobarralene (tfbb) (2); M = lr, diolefin = cod (3)]. The molecular structure of complex 1 has been determined by X-ray diffraction methods. The tetranuclear structure is supported by two S, N, Otridentate ligands exhibiting a 1κO, 2κN, 3:4κ2 S coordination mode. Carbonylation of the rhodium diolefin complexes at atmospheric pressure gives [Rh4(μ-PyS0)2(C0)8] (4). The carbonylation of 1 is partially reversible, and the mixed-ligand complex [Rh4(μ-PySO)2(cod)2(CO)4] (5) has been obtained as a single isomer. The reaction of 4 with triphenylphosphine gives the compound [Rh4(μ-PySO)2(CO)4(PPh 3)4] (6) which also exists as a single isomer of C 2 symmetry. The diolefin complexes are redox active and exhibit two one-electron oxidations at a platinum disk electrode in dichloromethane separated by approximately 0.5 V at potentials accessible by chemical oxidants. The tetranuclear complexes were selectively oxidized to the 63-electron mixed-valence cationic complexes [M4(μ-PySO)2(diolefin) 4]+(1a+, 2+, and 3+) by using AgCF3SO3 as oxidant and isolated as the triflate salts. Alternatively, the oxidation with [Cp2Fe]PF6 gives [Rh4(μ-PySO)2(cod)4][PF6] (1b+). The parameters obtained from the simulation of the electron paramagnetic resonance spectra of the oxidized species strongly suggest that the unpaired electron is delocalized over only two metal atoms in the complexes.The financial support from Ministerio de Educación y Ciencia (MEC/FEDER) Project CTQ2006-03973/BQU and Grant CSD2006-0015 Consolider Ingenio 2010 is gratefully acknowledged.Peer Reviewe