Simulación de procesos con controladores lógico-programables (PLC’s)

La realización de prácticas en el laboratorio de control de procesos presenta como mayor dificultad el coste asociado al funcionamiento del proceso, debido al consumo de reactivos, de energía o a la generación de residuos. Por tanto se propone trabajar con un proceso simulado en un controlador lógico- programable o PLC, con lo que se realiza una práctica de bajo coste y más cercana a la realidad que la pura simulación numérica

An insight into transfer hydrogenation reactions catalysed by iridium(iii) bis-n-heterocyclic carbenes

A variety of [M(L)2(L')2{kC,C'-bis(NHC)}]BF4 complexes (M = Rh or Ir; L = CH3CN or wingtip group; L' = I– or CF3COO–; NHC=N-heterocyclic carbene) have been tested as pre-catalysts for the transfer hydrogenation of ketones and imines. The conversions and TOF's obtained are closely related to the nature of the ligand system and metal centre, more strongly coordinating wingtip groups yielding more active and recyclable catalysts. Theoretical calculations at the DFT level support a classic stepwise metal-hydride pathway against the concerted Meerwein–Ponndorf–Verley (MPV) mechanism. The calculated catalytic cycle involves a series of ligand rearrangements due to the high trans effect of the carbene and hydrido ligands, which are more stable when situated in mutual cis positions. The reaction profiles obtained for the complexes featuring an iodide or a trifluoroacetate in one of the apical positions agree well with the relative activity observed for both catalysts

An insight into transfer hydrogenation reactions catalysed by iridium(III) bis-N-heterocyclic carbenes

A variety of [M(L)2(L′)2{κC,C′-bis(NHC)}]BF4 complexes (M = Rh or Ir; L = CH3CN or wingtip group; L′ = I– or CF3COO–; NHC=N-heterocyclic carbene) have been tested as pre-catalysts for the transfer hydrogenation of ketones and imines. The conversions and TOF's obtained are closely related to the nature of the ligand system and metal centre, more strongly coordinating wingtip groups yielding more active and recyclable catalysts. Theoretical calculations at the DFT level support a classic stepwise metal-hydride pathway against the concerted Meerwein–Ponndorf–Verley (MPV) mechanism. The calculated catalytic cycle involves a series of ligand rearrangements due to the high trans effect of the carbene and hydrido ligands, which are more stable when situated in mutual cis positions. The reaction profiles obtained for the complexes featuring an iodide or a trifluoroacetate in one of the apical positions agree well with the relative activity observed for both catalysts.The authors would like to acknowledge the support by the Ministry of Higher Education, Saudi Arabia, in establishment of the Centre of Research Excellence in Petroleum Refining & Petrochemicals at KFUPM (KACST-funded project ART-32-68). The support under the KFUPM–University of Zaragoza research agreement is also highly appreciated. This work was further supported by the Spanish Ministry of Economy and Competitiveness (MINECO/FEDER) (CONSOLIDER INGENIO CSD2009-0050, CTQ2011-27593 and CTQ2012-35665 projects) and the Diputación General de Aragón (DGA/FSE-E07).Peer Reviewe

Hydrolysis and methanolysis of silanes catalyzed by iridium(III) bis-N-heterocyclic carbene complexes: Influence of the wingtip groups

New [Ir(CH3CN)2(I)2{κC,C′-bis(NHC)}]BF4 complexes featuring bis-NHC ligands with a methylene bridge and different N substitution (−CH2CH2CH2CH3 and −CH2CH2OPh) were synthesized. NMR studies and X-ray diffraction structures evidenced that the wingtip group −CH2CH2OPh presents a hemilabile behavior in solution, with the oxygen atom coordinating and dissociating at room temperature, which contrasts with the strong coordination of the ether functions in the complex [Ir(I)2{κC,C′,O,O′-bis(NHCOMe)}]BF4 (bis(NHCOMe) = methylenebis(N,N′-bis(2-methoxyethyl)imidazol-2-ylidene)), previously reported by us. These complexes proved to be efficient catalysts for the hydrolysis and methanolysis of silanes, affording molecular hydrogen and silyl alcohols or silyl ethers as the main reaction products in excellent yields. The hydrogen generation rates were very much dependent on the nature of the hydrosilane and the coordination ability of the wingtip group. The latter also played a key role in the recyclability of the catalytic system.This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO/FEDER) (CONSOLIDER INGENIO CSD2009-0050, CTQ2011-27593 projects, and “Juan de la Cierva” (M.I.) and Ramón y Cajal (P.J.S.M.) programs) and the DGA/FSE-E07. The authors express their appreciation to the support from the Ministry of Higher Education, Saudi Arabia, in establishment of the Center of Research Excellence in Petroleum Refining & Petrochemicals at King Fahd University of Petroleum & Minerals (KFUPM) and the support from KFUPM-University of Zaragoza research agreement.Peer Reviewe

Dinuclear pyridine-4-thiolate-bridged rhodium and iridium complexes as ditopic building blocks in molecular architecture

A series of dinuclear pyridine-4-thiolate (4-Spy)-bridged rhodium and iridium compounds [M(μ-4-Spy)(diolef)]2 [diolef = 1,5-cyclooctadiene (cod), M = Rh (1), Ir (2); diolef = 2,5-norbornadiene (nbd), M = Rh (3)] were prepared by the reaction of Li(4-Spy) with the appropriate compound [M(μ-Cl)(diolef)]2 (M = Rh, Ir). The dinuclear compound [Rh(μ-4-Spy)(CO)(PPh3)]2 (4) was obtained by the reaction of [Rh(acac)(CO)(PPh3)] (acac = acetylacetonate) with 4-pySH. Compounds 1-4 were assessed as metalloligands in self-assembly reactions with the cis-blocked acceptors [M(cod)(NCCH3)2](BF 4) [M = Rh (a), Ir (b)] and [M(H2O)2(dppp)] (OTf)2 [M = Pd (c), Pt (d); dppp = 1,3-bis(diphenylphosphino)propane] . The homometallic hexanuclear metallomacrocycles [{M2(μ-4-Spy) 2(cod)2}2{M(cod)}2](BF 4)2 (M = Rh [(1a)2], Ir [(2b)2]) and the heterometallic hexanuclear metallomacrocycles [{Rh2(μ-4-Spy) 2(cod)2}2{Ir(cod)}2](BF 4)2 [(1b)2], [{Rh2(μ-4-Spy) 2(cod)2}2{M′(dppp)}2](OTf) 4 (M′ = Pd [(1c)2], Pt [(1d)2]), and [{Ir2(μ-4-Spy)2(cod)2}2{M′ (dppp)}2](OTf)4 (M′ = Pd [(2c)2], Pt [(2d)2]) were obtained. NMR spectroscopy in combination with electrospray ionization mass spectrometry was used to elucidate the nature of the metalloligands and their respective supramolecular assemblies. Most of the synthesized species were found to be nonrigid in solution, and their fluxional behavior was studied by variable-temperature 1H NMR spectroscopy. An X-ray diffraction study of the assemblies (1a)2 and (1d)2 revealed the formation of rectangular (9.6 Å × 6.6 Å) hexanuclear metallomacrocycles with alternating dinuclear (Rh2) and mononuclear (Rh or Pt) corners. The hexanuclear core is supported by four pyridine-4-thiolate linkers, which are bonded through the thiolate moieties to the dinuclear rhodium units, exhibiting a bent-anti arrangement, and through the peripheral pyridinic nitrogen atoms to the mononuclear corners.Financial support for this work was provided by the Ministerio de Economía y Competitividad (MINECO/FEDER) of Spain (Projects CTQ2010-15221 and CTQ2012-31335), Diputación General de Aragón (Group E07), and Fondo Social Europeo.Peer Reviewe

Dinuclear Pyridine-4-thiolate-bridged rhodium and iridium complexes as ditopic building blocks in molecular architecture

A series of dinuclear pyridine-4-thiolate rhodium and iridium compounds [M(μ-4-Spy)(diolef)]2 (diolef = 1,5-cyclooctadiene, cod; M = Rh (1), Ir (2); 2,5-norbornadiene, nbd; M = Rh (3)) have been prepared by reaction of Li(4-Spy) with the appropriate compound [M(μ-Cl)(diolef)]2 (M = Rh, Ir). The dinuclear compound [Rh(μ-4-Spy)(CO)(PPh3)]2 (4) has been obtained by reaction of [Rh(acac)(CO)(PPh3] with 4-pySH. Compounds 1-4 have been assessed as metalloligands in self-assembly reactions with the cis-blocked [M(cod)(NCCH3)2](BF4) (M = Rh (a) and M = Ir (b)) and [M(H2O)2(dppp)](OTf)2 (M = Pd (c), Pt (d)) (dppp = 1,3-bis(diphenylphosphino)propane) acceptors. Homo [{M2(μ-4-Spy)2(cod)2}2{M(cod)}2](BF4)2 (M = Rh (1a)2, and M = Ir (2b)2), and hetero [{Rh2(μ-4-Spy)2(cod)2}2{Ir(cod)}2](BF4)2 (1b)2, [{Rh2(μ-4-Spy)2(cod)2}2{M'(dppp)}2](OTf)4 ( M' = Pd (1c)2 and M'= Pt (1d)2) and [{Ir2(μ-4-Spy)2(cod)2}2{M'(dppp)}2](OTf)4 ( M' = Pd (2c)2 and M'= Pt (2d)2) hexanuclear metallomacrocycles have been obtained. NMR spectroscopy, in combination with ESI mass spectrometry has been used to elucidate the nature of the metalloligands and their respective supramolecular assemblies. Most of synthesized species have shown to be non-rigid in solution and their fluxional behavior has been studied by VT 1H NMR spectroscopy. An X-ray diffraction study on the assemblies (1a)2 and (1d)2 revealed the formation of rectangular (9.6 x 6.6 Å) hexanuclear metallomacrocycles with alternating dinuclear (Rh2) and mononuclear (Rh or Pt) corners. The hexanuclear core is supported by four pyridine-4-thiolate linkers, which are bonded through the thiolate moiety to the dinuclear rhodium units, exhibiting a bent-anti arrangement, and through the peripheral pyridinic nitrogen atoms to the mononuclear corners

Novel homogeneous Ir-catalysts: Ligand design, applications and mechanisms

Resumen del trabajo presentado a la 2nd World Chemistry Conference and Exhibition (WCCE), celebrada en Valencia (España) del 9 al 11 de julio de 2018.This presentation will deal with two main subjects: (i) the preparation ofthe frrst PCP-type ligand based on an N-heterocyclic olefm (NHO) scaffold, accompanied by an evaluation of the impact of this type of ligand in the activity of iridium complexes in several relevant catalytic processes; and (ii) the development of well- defined Ir-NHC complexes as catalysts for the dehydrogenative silylation of aromatic C-H bonds. (i) A great variety of pincer complexes has been reported in the literature. In particular, transition metal complexes containing PCP pincer ligands have shown remarkable activities in relevant catalytic processes. Recent work by us on this subject has resulted in the preparation of an ewPCP-type ligand based on an N- heterocyclic olefin (NHO) scaffold. The flexibille coordination of this NHO-based PCP-ligand can be attributed to the dual nature (ylide-olefm) oftbe NHO. Iridium(I) complexes featuring this ligand show excellent activities in transfer hydrogenation reactions. The active species ([Ir(KP,C,P'-NHO-PPh2)(iPrO)]), formed via COD dissociation and subsequent isopropoxide coordination, features an NHO moiety that behaves as a hemilabile ligand, which allows the catalyst to adopt stabJe square planar geometries in the transition states, thus reducing the energetic barrier of the process. More recently, we have tested the activity ofthese complexes in the dehydrogenation of formic acid, showing outstanding activities in water and in neat formicacid. (ii) The preparation of fine chernicals by the catalytic functionalization of C-H bonds has seen an outstanding development in recent years, with borylation and silylation reactions being prominent examples of this chemistry. In this regard, the versatility of oganosilicon compounds can be attributed to the low cost and non-toxic nature of silicon reagents, together with their straight forward functionalization by various reactions. Moreover, conjugated organosilicon materials are attractive targets per se owing to their unique properties, which permit a widespread applicability in the field of organic electronics and photonics. Most of the catalysts employed so far for this reaction are generated >in situ> from commercial metal precursors and ligands. Hence, we have focused on the development of well-defined organometallic catalysts bearing appropriate ligands in order to improve the efficiency of current silylation catalysts. In particular, the use of NHC-Ir (III) complex [Ir(H)2(IPr)(py)3][BF4] (IPr = 1 ,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) as a catalyst has allowed for the preparation of a wide range of aryl- and heteroarylsilanes. The directed and non-directed functionalization of C-H bonds has been accomplisbed successfully using the areneas tbe limiting reagent and a variety of hydrosilanes, including Et3SiH, Ph2MeSiH, PhMe2SiH, Ph3SiH and(Et0)3SiH.Peer Reviewe

Pyridinethiolate titanocene metalloligands and their self-assembly reactions to yield early-late metallamacrocycles

New titanocene pyridinethiolate compounds [(RCp)(2)Ti(4-Spy)(2)] (R = H (1), Me (2); Cp = cyclo-pentadienyl; 4-Spy = pyridine-4-thiolate) and [Cp2Ti(2-Spy)(2)] (3; 2-Spy = pyridine-2-thiolate) have been prepared by reaction of the corresponding Li(Spy) salt with the appropriate compound [(RCp)(2)TiCl2]. Compounds 1 and 2 have been used as metalloligands in self-assembly reactions with the acceptor late-transition-metal compounds [M(H2O)(2)(dppp)]-(OTf)(2) (M = Pd (a) Pt (b); dppp = 1,3-bis-(diphenylphosphino)propane), and the series of early-late tetranuclear metallamacrocycles [{(RCp)(2)Ti(4-Spy)(2)}{M-(dppp)}](2)(OTf)(4) (R = H, M = Pd (1(2)a(2)); R = H, M = Pt (1(2)b(2)); R = Me, M = Pd (2(2)a(2)); R = Me, M = Pt (2(2)b(2))) arising from the anti isomer of the titanocene metalloligands have been obtained. Only ligand transfer reactions from Ti to either Pd or Pt atoms have been observed when the pyridine-2-thiolate derivative 3 has been assayed in self-assembly processes. The obtained species have been characterized by NMR spectroscopy and ESI(+) mass spectrometry. The supramolecular assemblies have shown to be nonrigid in solution, and their fluxional behavior has been studied by VT H-1 NMR spectroscopy. A DFT study including ab initio molecular dynamics in order to elucidate the structures and the relative stability of the isomers has been performed

Gaia Data Release 3: Exploring and mapping the diffuse interstellar band at 862 nm

Context. Diffuse interstellar bands (DIBs) are common interstellar absorption features in spectroscopic observations but their origins remain unclear. DIBs play an important role in the life cycle of the interstellar medium (ISM) and can also be used to trace Galactic structure. Aims. Here, we demonstrate the capacity of the Gaia-Radial Velocity Spectrometer (RVS) in Gaia DR3 to reveal the spatial distribution of the unknown molecular species responsible for the most prominent DIB at 862 nm in the RVS passband, exploring the Galactic ISM within a few kiloparsecs from the Sun. Methods. The DIBs are measured within the GSP-Spec module using a Gaussian profile fit for cool stars and a Gaussian process for hot stars. In addition to the equivalent widths and their uncertainties, Gaia DR3 provides their characteristic central wavelength, width, and quality flags. Results. We present an extensive sample of 476 117 individual DIB measurements obtained in a homogeneous way covering the entire sky. We compare spatial distributions of the DIB carrier with interstellar reddening and find evidence that DIB carriers are present in a local bubble around the Sun which contains nearly no dust. We characterised the DIB equivalent width with a local density of 0.19 ± 0.04 kpc1 and a scale height of 98.60 8.46+11.10 pc. The latter is smaller than the dust scale height, indicating that DIBs are more concentrated towards the Galactic plane. We determine the rest-frame wavelength with unprecedented precision (?0 = 8620.86 ± 0.019 in air) and reveal a remarkable correspondence between the DIB velocities and the CO gas velocities, suggesting that the 862 nm DIB carrier is related to macro-molecules. Conclusions. We demonstrate the unique capacity of Gaia to trace the spatial structure of the Galactic ISM using the 862 nm DIB

Gaia Data Release 3: The Galaxy in your preferred colours: Synthetic photometry from Gaia low-resolution spectra

Gaia Data Release 3 provides novel flux-calibrated low-resolution spectrophotometry for '220 million sources in the wavelength range 330 nm ≤ λ ≤ 1050 nm (XP spectra). Synthetic photometry directly tied to a flux in physical units can be obtained from these spectra for any passband fully enclosed in this wavelength range. We describe how synthetic photometry can be obtained from XP spectra, illustrating the performance that can be achieved under a range of different conditions - for example passband width and wavelength range - as well as the limits and the problems affecting it. Existing top-quality photometry can be reproduced within a few per cent over a wide range of magnitudes and colour, for wide and medium bands, and with up to millimag accuracy when synthetic photometry is standardised with respect to these external sources. Some examples of potential scientific application are presented, including the detection of multiple populations in globular clusters, the estimation of metallicity extended to the very metal-poor regime, and the classification of white dwarfs. A catalogue providing standardised photometry for 2.2×108sources in several wide bands of widely used photometric systems is provided (Gaia Synthetic Photometry Catalogue; GSPC) as well as a catalogue of '105 white dwarfs with DA/non-DA classification obtained with a Random Forest algorithm (Gaia Synthetic Photometry Catalogue for White Dwarfs; GSPC-WD)