Enhancing the catalytic properties of well-defined electrophilic platinum complexes

Platinum complexes have been often considered as the least reactive of the group 10 triad metals. Slow kinetics are behind this lack of reactivity but, still, some industrially relevant catalytic process are dominated by platinum compounds and sometimes different selectivities can be found in comparison to Ni or Pd. Nevertheless, during the last years, it has been reported that the catalytic behaviour of well-defined platinum derivatives can be improved through a judicious choice of their electronic and steric properties, leading to highly electrophilic or low-electron count platinum systems. In this feature article, we highlight some catalytic processes in which well-defined electrophilic platinum complexes or coordinatively unsaturated systems play an important role in their catalytic activity

True and masked three-coordinate T-shaped platinum(II) intermediates

Although four-coordinate square-planar geometries, with a formally 16-electron counting, are absolutely dominant in isolated Pt(II) complexes, three-coordinate, 14-electron Pt(II) complexes are believed to be key intermediates in a number of platinum-mediated organometallic transformations. Although very few authenticated three-coordinate Pt(II) complexes have been characterized, a much larger number of complexes can be described as operationally three-coordinate in a kinetic sense. In these compounds, which we have called masked T-shaped complexes, the fourth position is occupied by a very weak ligand (agostic bond, solvent molecule or counteranion), which can be easily displaced. This review summarizes the structural features of the true and masked T-shaped Pt(II) complexes reported so far and describes synthetic strategies employed for their formation. Moreover, recent experimental and theoretical reports are analyzed, which suggest the involvement of such intermediates in reaction mechanisms, particularly C–H bond-activation processes

Catalytic dehydrocoupling of amine-boranes and amines into diaminoboranes: isolation of a Pt(II), Shimoi-type, η1-BH complex

The platinum complex [Pt(IBu′)(IBu)][BAr] is a very efficient catalyst in the synthesis of diaminoboranes through dehydrocoupling of amine-boranes and amines. Shimoi-type, η-BH complexes are key intermediates in the process.Financial support (FEDER contribution) from the MINECO (Projects CTQ2013-45011-P and CTQ2014-51912-REDC) and the Junta de Andalucía (Project FQM-2126) is gratefully acknowledged.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).Peer Reviewe

Different coordination modes of an aryl-substituted hydrotris(pyrazolyl) borate ligand in rhodium and iridium complexes

Complexes TptolRh(C2H4)2 (1a) and TptolRh(CH2C(Me)C(Me)CH2) (1b) have been prepared by reaction of KTptol with the appropriate [RhCl(olefin)2]2 dimer (Tptol means hydrotris(3-p-tolylpyrazol-1-yl)borate). The two complexes show a dynamic behaviour that involves exchange between κ2 and κ3 coordination modes of the Tptol ligand. The iridium analogue, TptolIr(CH2C(Me)CHCH2) (2) has also been synthesized, and has been converted into the Ir(III) dinitrogen complex [(κ4-N,N',N'',C-Tptol)Ir(Ph)(N2) (3) by irradiation with UV light under a dinitrogen atmosphere. Compound 3 constitutes a rare example of Ir(III)-N2 complex structurally characterized by X-ray crystallography. Its N2 ligand can be easily substituted by acetonitrile or ethylene upon heating and denticity changes in the Tptol ligand, from κ4-N,N',N'',C (monometallated Tptol, from now on represented as Tptol′) to κ5-N,N′,N″,C,C″ (dimetallated Tp tol ligand, represented as Tptol″) have been observed. When complex 3 is heated in the presence of acetylene, dimerization of the alkyne takes place to yield the enyne complex [(κ5-N,N′,N′′,C,C′-Tp tol)Ir(CH2CHCCH), 7̧ in which the unsaturated organic moiety is bonded to iridium through the carbon-carbon double bond.Ministerio de Educación y Ciencia CTQ2007-62814Consolider-Ingenio 2010 CSD2007-00006Junta de Andalucía FQM-3151, FQM-672CONACYT 22934

Bonding Situation of σ‐E−H Complexes in Transition Metal and Main Group Compounds

The ambiguous bonding situation of σ-E−H (E=Si, B) complexes in transition metal compounds has been rationalized by means of Density Functional Theory calculations. To this end, the combination of the Energy Decomposition Analysis (EDA) method and its Natural Orbital for Chemical Valance (NOCV) extension has been applied to representative complexes described in the literature where the possible η1 versus η2 coordination mode is not unambiguously defined. Our quantitative analyses, which complement previous data based on the application of the Quantum Theory of Atoms in Molecules (QTAIM) approach, indicate that there exists a continuum between genuine η1 and η2 modes depending mainly on the strength of the backdonation. Finally, we also applied this EDA-NOCV approach to related main-group species where the backdonation is minimal

The high-resolution NMR structure of the R21A Spc-SH3:P41 complex: Understanding the determinants of binding affinity by comparison with Abl-SH3

BACKGROUND: SH3 domains are small protein modules of 60–85 amino acids that bind to short proline-rich sequences with moderate-to-low affinity and specificity. Interactions with SH3 domains play a crucial role in regulation of many cellular processes (some are related to cancer and AIDS) and have thus been interesting targets in drug design. The decapeptide APSYSPPPPP (p41) binds with relatively high affinity to the SH3 domain of the Abl tyrosine kinase (Abl-SH3), while it has a 100 times lower affinity for the α-spectrin SH3 domain (Spc-SH3). RESULTS: Here we present the high-resolution structure of the complex between the R21A mutant of Spc-SH3 and p41 derived from NMR data. Thermodynamic parameters of binding of p41 to both WT and R21A Spc-SH3 were measured by a combination of isothermal titration and differential scanning calorimetry. Mutation of arginine 21 to alanine in Spc-SH3 increases 3- to 4-fold the binding affinity for p41 due to elimination at the binding-site interface of the steric clash produced by the longer arginine side chain. Amide hydrogen-deuterium experiments on the free and p41-bound R21A Spc-SH3 domain indicate that binding elicits a strong reduction in the conformational flexibility of the domain. Despite the great differences in the thermodynamic magnitudes of binding, the structure of the R21A Spc-SH3:P41 complex is remarkably similar to that of the Abl-SH3:P41 complex, with only few differences in protein-ligand contacts at the specificity pocket. Using empirical methods for the prediction of binding energetics based on solvent-accessible surface area calculations, the differences in experimental energetics of binding between the two complexes could not be properly explained only on the basis of the structural differences observed between the complexes. We suggest that the experimental differences in binding energetics can be at least partially ascribed to the absence in the R21A Spc-SH3:P41 complex of several buried water molecules, which have been proposed previously to contribute largely to the highly negative enthalpy and entropy of binding in the Abl-SH3:P41 complex. CONCLUSION: Based on a deep structural and thermodynamic analysis of a low and high affinity complex of two different SH3 domains with the same ligand p41, we underline the importance of taking into account in any effective strategy of rational design of ligands, factors different from the direct protein-ligand interactions, such as the mediation of interactions by water molecules or the existence of cooperative conformational effects induced by binding

Platinum nanoparticles stabilized by N-heterocyclic thiones. Synthesis and catalytic activity in mono- and di-hydroboration of alkynes

N-Heterocyclic Thiones (NHT) proved to be efficient ligands for the stabilization of small platinum nanoparticles (1.3-1.7 nm), synthesized by decomposition of [Pt(dba)2], under a H2 atmosphere, in the presence of variable sub-stoichiometric amounts of the NHT. Full characterization by means of TEM, HR-TEM, NMR, ICP, TGA and XPS have been carried out, providing information about the nature of the metal nanoparticles and the interaction of the NHT ligands to the metal surface. Importantly, DFT calculations indicate that some NHT ligands interact with the metal through the C[double bond, length as m-dash]C double bond of the imidazole fragment in addition to the sulfur atom, thus providing additional stabilization to the nanoparticles. According to XPS, TGA and ICP techniques, the surface coverage by the ligand increases by decreasing the size of the substituents on the nitrogen atom. The platinum nanoparticles have been used as catalyst in the hydroboration of alkynes. The most active system is that with a less covered surface area lacking an interaction of the ligand by means of the C[double bond, length as m-dash]C double bond. This catalyst hydroborates alkynes with excellent selectivities towards the monoborylated anti-Markovnikov product (vinyl-boronate) when one equiv. of borane is used. Very interestingly, aliphatic alkynes undergo a second hydroborylation process leading to the corresponding 1,1- and 1,2-diboroylated species with good selectivities towards the former.España MINECO (Projects CTQ2016-76267-P, CTQ2016-80814-R and CTQ2016- 81797-REDC)España Junta de Andalucía Project FQM-212

Formation of C−X Bonds Through Stable Low-Electron Count Cationic Pt(IV) Alkyl Complexes Stabilized by N-Heterocyclic Carbenes

Cationic five-coordinate Pt(IV) alkyl complexes stabilized by bulky N-heterocyclic carbenes have been isolated and fully characterized. Related species have been postulated as key intermediates in carbon–heteroatom coupling reactions and most particularly in Shilov-type chemistry. The alkyl groups exhibit a pronounced electrophilic character and can undergo nucleophilic addition of pyridine, bromide, or iodide to form new carbon–heteroatom bonds. Nevertheless, direct reductive coupling to form C–X bonds can be operative in the absence of an external nucleophile source.Ministerio de Ciencia, Innovación y Universidades CTQ2013-45011Junta de Andalucía FQM-212

Synthesis, properties, and some rhodium, iridium, and platinum complexes of a series of bulky m-terphenylphosphine ligands

A series of sterically demanding aryl phosphine ligands (L) bearing terphenyl substituents, PR2Ar′ (R = hydrocarbyl, Ar′ = 2,6-diarylphenyl radical) has been prepared and characterized. The stability of these ligands towards oxidation in the air has been tested, and theoretical and experimental studies aimed to provide information on their electronic and steric properties have been performed. Treatment of the metal dimers [MCl(COD)]2(M = Rh, Ir; COD = 1,5-cyclooctadiene) with ligands PMe2ArXyl2(L1) and PMe2ArDipp2(L5), in a 1:1 metal:ligand ratio, afforded the expected square-planar 16-electron complexes [MCl(COD)(PMe2ArXyl2)] and [MCl(COD)(PMe2ArDipp2)], respectively. These compounds were readily converted into the corresponding dicarbonyl derivatives, [MCl(CO)2(PMe2ArXyl2)] and [MCl(CO)2(PMe2ArDipp2)], respectively. While the expected κ1-P coordination mode of the PR2Ar′ ligands is found for these rhodium and iridium species, the mononuclear Pt(II) derivative obtained by reaction of PtCl2with PMe2ArDipp2has composition [PtCl2(PMe2ArDipp2)], and exhibits a bidentate κ1-P, η1-arene coordination mode involving one of the ipso carbon atoms of a flanking terphenyl aryl ring. The corresponding carbonyl compound [PtCl2(CO)(PMe2ArDipp2)], was generated under a CO atmosphere and exhibits κ1-P coordination mode.Ministerio de Ciencia CTQ2013-42501-P, CTQ2014-51912-REDC, CTQ-2014-52769-C3-3-RJunta de Andalucía FQM-119 P09-FQM-4832, FQM-2126European Union 26722

Temporal variability analysis reveals biases in electronic health records due to hospital process reengineering interventions over seven years

[EN] Objective To evaluate the effects of Process-Reengineering interventions on the Electronic Health Records (EHR) of a hospital over 7 years. Materials and methods Temporal Variability Assessment (TVA) based on probabilistic data quality assessment was applied to the historic monthly-batched admission data of Hospital La Fe Valencia, Spain from 2010 to 2016. Routine healthcare data with a complete EHR was expanded by processed variables such as the Charlson Comorbidity Index. Results Four Process-Reengineering interventions were detected by quantifiable effects on the EHR: (1) the hospital relocation in 2011 involved progressive reduction of admissions during the next four months, (2) the hospital services re-configuration incremented the number of inter-services transfers, (3) the care-services re-distribution led to transfers between facilities (4) the assignment to the hospital of a new area with 80,000 patients in 2015 inspired the discharge to home for follow up and the update of the pre-surgery planned admissions protocol that produced a significant decrease of the patient length of stay. Discussion TVA provides an indicator of the effect of process re-engineering interventions on healthcare practice. Evaluating the effect of facilities¿ relocation and increment of citizens (findings 1, 3¿4), the impact of strategies (findings 2¿3), and gradual changes in protocols (finding 4) may help on the hospital management by optimizing interventions based on their effect on EHRs or on data reuse. Conclusions The effects on hospitals EHR due to process re-engineering interventions can be evaluated using the TVA methodology. Being aware of conditioned variations in EHR is of the utmost importance for the reliable reuse of routine hospitalization data.F.J.P.B, C.S., J.M.G.G. and J.A.C. were funded Universitat Politecnica de Valencia, project "ANALISIS DE LA CALIDAD Y VARIABILIDAD DE DATOS MEDICOS". www.upv.es. J.M.G.G.is also partially supported by: Ministerio de Economia y Competitividad of Spain through MTS4up project (National Plan for Scientific and Technical Research and Innovation 2013-2016, No. DPI2016-80054-R); and European Commission projects H2020-SC1-2016-CNECT Project (No. 727560) and H2020-SC1-BHC-2018-2020 (No. 825750). The funders did not play any role in the study design, data collection and analysis, decision to publish, nor preparation of the manuscript.Perez-Benito, FJ.; Sáez Silvestre, C.; Conejero, JA.; Tortajada, S.; Valdivieso, B.; Garcia-Gomez, JM. (2019). Temporal variability analysis reveals biases in electronic health records due to hospital process reengineering interventions over seven years. PLoS ONE. 14(8):1-19. https://doi.org/10.1371/journal.pone.0220369S119148Aguilar-Savén, R. S. (2004). Business process modelling: Review and framework. International Journal of Production Economics, 90(2), 129-149. doi:10.1016/s0925-5273(03)00102-6Poulymenopoulou, M. 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