Tuning the Inorganic Core of a reduced Ni2Ge2 Cluster.

Tetranuclear cores (M-E)2 of transition metals (M) and tetrylenes (EII=Si, Ge, Sn) are key motifs in homogeneous and heterogeneous catalysis. They exhibit a continuum of M-M and E-E bonding within the inorganic core that leads to a variety of structures for which there are no specific synthetic methods. Herein, we report a series of highly reduced [Ni0GeII]2 squares solely stabilized by bulky terphenyl (C6H3-2,6-Ar2) ligands, for which we provide complementary and high-yielding syntheses. Reactivity studies with common Lewis bases (carbene and CO) evince that the structure of the (M-E)2 core can be transformed. We have investigated this core modification by computational means, offering a rationale to better understand the continuum of bonding across these clusters.

Catalytic Nitrous Oxide Reduction with H2 Mediated by Pincer Ir Complexes.

Reduction of nitrous oxide (N2O) with H2 to N2 and water is an attractive process for the decomposition of this greenhouse gas to environmentally benign species. Herein, a series of iridium complexes based on proton-responsive pincer ligands (1-4) are shown to catalyze the hydrogenation of N2O under mild conditions (2 bar H2/N2O (1:1), 30 °C). Among the tested catalysts, the Ir complex 4, based on a lutidine-derived CNP pincer ligand having nonequivalent phosphine and N-heterocyclic carbene (NHC) side donors, gave rise to the highest catalytic activity (turnover frequency (TOF) = 11.9 h-1 at 30 °C, and 16.4 h-1 at 55 °C). Insights into the reaction mechanism with 4 have been obtained through NMR spectroscopy. Thus, reaction of 4 with N2O in tetrahydrofuran-d8 (THF-d8) initially produces deprotonated (at the NHC arm) species 5NHC, which readily reacts with H2 to regenerate the trihydride complex 4. However, prolonged exposure of 4 to N2O for 6 h yields the dinitrogen Ir(I) complex 7P, having a deprotonated (at the P-arm) pincer ligand. Complex 7P is a poor catalytic precursor in the N2O hydrogenation, pointing out to the formation of 7P as a catalyst deactivation pathway. Moreover, when the reaction of 4 with N2O is carried out in wet THF-d8, formation of a new species, which has been assigned to the hydroxo species 8, is observed. Finally, taking into account the experimental results, density functional theory (DFT) calculations were performed to get information on the catalytic cycle steps. Calculations are in agreement with 4 as the TOF-determining intermediate (TDI) and the transfer of an apical hydrido ligand to the terminal nitrogen atom of N2O as the TOF-determining transition state (TDTS), with very similar reaction rates for the mechanisms involving either the NHC- or the P-CH2 pincer methylene linkers.

Smoking in hospitalized patients. A great opportunity. / Tabaquismo en pacientes hospitalizados. Una gran oportunidad.

The objective of this study is to describe the characteristics of smokers admitted to different medical and surgical services in a university hospital and the perception of patients regarding the need for a specialized intervention. The sample comprises a total of 307 patients (mean age of 59.4 years), being 40% (n = 123) non-smokers, 42.7% (n = 131) ex-smokers, and 17.3% (n = 53) smokers. The average consumption of smokers was 22.2 cigarettes / day and the severity of nicotine dependence evaluated with the Fagerström test exceeded 5 points in more than half of the sample. On the other hand, 77.7% had made at least one previous attempt to quit tobacco use. Almost the entire sample (89.9%) of smokers and ex-smokers considered it necessary to develop tobacco treatment programs during hospitalization. Finally, the importance of the hospital context is argued as an opportunity to address the cessation of smoking. The data obtained in this study will allow focusing more appropriately on the management of these patients and optimizing resources.

El objetivo de este estudio es conocer las características de los fumadores ingresados en diferentes servicios médicos y quirúrgicos en un hospital universitario y la percepción de los pacientes respecto a la necesidad de una intervención especializada. La muestra comprende un total de 307 pacientes (edad media de 59,4 años), siendo un 40% (n = 123) no fumadores, 42,7% (n = 131) exfumadores, y un 17,3% (n = 53) fumadores. El consumo medio de los fumadores era de 22,2 cigarrillos/día y la gravedad de la dependencia a la nicotina evaluado con el test de Fagerström sobrepasaba los 5 puntos en más de la mitad de la muestra. Por otra parte, el 77,7% había realizado al menos un intento previo de abandono del consumo de tabaco. Casi la totalidad de la muestra (89,9%) de los fumadores y ex fumadores consideraba necesario desarrollar programas de tratamiento del tabaquismo en la hospitalización. Finalmente se argumenta la importancia del contexto hospitalario como oportunidad para abordar la cesación del hábito tabáquico. Los datos obtenidos en el presente estudio permitirán enfocar más adecuadamente el manejo de estos pacientes y optimizar los recursos.

Dehydrogenative Double C-H Bond Activation in a Germylene-Rhodium Complex*.

Transition metal tetrylene complexes offer great opportunities for molecular cooperation due to the ambiphilic character of the group 14 element. Here we focus on the coordination of germylene [(ArMes2 )2 Ge :] (ArMes =C6 H3 -2,6-(C6 H2 -2,4,6-Me3 )2 ) to [RhCl(COD)]2 (COD=1,5-cyclooctadiene), which yields a neutral germyl complex in which the rhodium center exhibits both η6 - and η2 -coordination to two mesityl rings in an unusual pincer-type structure. Chloride abstraction from this species triggers a singular dehydrogenative double C-H bond activation across the Ge/Rh motif. We have isolated and fully characterized three rhodium-germyl species associated to three C-H cleavage events along this process. The reaction mechanism has been further investigated by computational means, supporting the key cooperative action of rhodium and germanium centers.

Ammonia-Borane Dehydrogenation Catalyzed by Dual-Mode Proton-Responsive Ir-CNNH Complexes.

Metal complexes incorporating proton-responsive ligands have been proved to be superior catalysts in reactions involving the H2 molecule. In this contribution, a series of IrIII complexes based on lutidine-derived CNNH pincers containing N-heterocyclic carbene and secondary amino NHR [R = Ph (4a), tBu (4b), benzyl (4c)] donors as flanking groups have been synthesized and tested in the dehydrogenation of ammonia-borane (NH3BH3, AB) in the presence of substoichiometric amounts (2.5 equiv) of tBuOK. These preactivated derivatives are efficient catalysts in AB dehydrogenation in THF at room temperature, albeit significantly different reaction rates were observed. Thus, by using 0.4 mol % of 4a, 1.0 equiv of H2 per mole of AB was released in 8.5 min (turnover frequency (TOF50%) = 1875 h-1), while complexes 4b and 4c (0.8 mol %) exhibited lower catalytic activities (TOF50% = 55-60 h-1). 4a is currently the best performing IrIII homogeneous catalyst for AB dehydrogenation. Kinetic rate measurements show a zero-order dependence with respect to AB, and first order with the catalyst in the dehydrogenation with 4a (-d[AB]/dt = k[4a]). Conversely, the reaction with 4b is second order in AB and first order in the catalyst (-d[AB]/dt = k[4b][AB]2). Moreover, the reactions of the derivatives 4a and 4b with an excess of tBuOK (2.5 equiv) have been analyzed through NMR spectroscopy. For the former precursor, formation of the iridate 5 was observed as a result of a double deprotonation at the amine and the NHC pincer arm. In marked contrast, in the case of 4b, a monodeprotonated (at the pincer NHC-arm) species 6 is observed upon reaction with tBuOK. Complex 6 is capable of activating H2 reversibly to yield the trihydride derivative 7. Finally, DFT calculations of the first AB dehydrogenation step catalyzed by 5 has been performed at the DFT//MN15 level of theory in order to get information on the predominant metal-ligand cooperation mode.

Sphincter damage during fistulotomy for perianal fistulae and its relationship with faecal incontinence.

BACKGROUND: The length of sphincter which can be divided during fistulotomy for perianal fistula is unclear. The aim was to quantify sphincter damage during fistulotomy and determine the relationship between such damage with symptoms and severity of faecal incontinence and long-term quality of life (QOL). METHODS: A prospective cohort study was performed over a 2-year period. Patients with intersphincteric and mid to low transsphincteric perianal fistulas without risk factors for faecal incontinence were scheduled for fistulotomy. All patients underwent 3D endoanal ultrasound (3D-EAUS) pre-operatively and 8 weeks postoperatively. Measurements were taken of pre- and postoperative anal sphincter involvement and division. Anal continence was assessed using the Jorge-Wexner scale and QOL scores pre, 6 and 12 months postoperatively. RESULTS: Forty-nine patients were selected. A strong correlation between pre- and postoperative measurements was found p < 0.001. A median length of 41% of the external anal sphincter and 32% of the internal anal sphincter was divided during fistulotomy. Significant differences in mild symptoms of anal continence were found with increasing length of external anal sphincter division. But there was no significant deterioration in continence, soiling, or quality of life scores at the 1-year follow-up. Division of over two-thirds of the external anal sphincter was associated with the highest incontinence rates. CONCLUSIONS: 3D-EAUS is a valuable tool for quantifying the extent of sphincter involvement pre- and postoperatively. Post-fistulotomy faecal incontinence is mild and increases with increasing length of sphincter division but does not affect long-term quality of life.

Ir-Catalyzed Atroposelective Desymmetrization of Heterobiaryls: Hydroarylation of Vinyl Ethers and Bicycloalkenes.

A highly regio-, diastereo-, and enantioselective, scalable Ir-catalyzed hydroarylation of electron-rich acyclic and tensioned cyclic olefins with heterobiaryls is described. The reaction of acyclic vinyl ethers, dihydrofuran, and norbornenes with a variety of aryl isoquinoline, quinazoline, and picoline derivatives takes place with simultaneous installation of central and axial chirality, reaching complete branched/linear or exo/endo ratios and excellent diastereo- and enantiomeric excesses when in situ formed [IrI/Tol-SDP] or [IrI/Tol-BINAP] complexes are used as the catalysts. Deuterium labeling experiments and a comprehensive computational study suggest that, despite fast double bond migratory insertion into Ir-H, the reaction proceeds through a modified Chalk-Harrod mechanism, starting with selectivity-determining insertion into Ir-CAryl. The regioselectivity is controlled by the electron-donating alkoxy group, whereas diastereo- and enantioselectivity have a complex origin, which depend on the relative orientation of the alkoxy group and the establishment of adequate π-π interactions between the biaryl and the phosphine.

Structural Snapshots of π-Arene Bonding in a Gold Germylene Cation.

Heavier group 14 element cations exhibit a remarkable reactivity that has typically hampered their isolation. For the few available examples, the role of π-arene interactions is crucial to provide kinetic stabilization, but dynamic and structural information on those contacts is yet limited. In this study we have accessed the metalogermylenium cation [(PMe2 ArDipp2 )AuGe(ArDipp2 )Cl]+ (4+ ) (ArDipp2 =C6 H3 -2,6-(C6 H3 -2,6-iPr2 )2 ) that has been structurally characterized with three different non-coordinating counter anions. These studies provide for the first time dynamic information about the conformational rearrangement that characterizes π-arene bonding thorough a series of X-ray diffraction structural snapshots. Computational studies reveal the weak character of the π-arene bonding (ca. 2 kcal mol-1 ) that can be described as the donation from a πC=C bond toward the empty p valence orbital of germanium.

Evidence for Genuine Bimetallic Frustrated Lewis Pair Activation of Dihydrogen with Gold(I)/Platinum(0) Systems.

A joint experimental/computational effort to elucidate the mechanism of dihydrogen activation by a gold(I)/platinum(0) metal-only frustrated Lewis pair (FLP) is described herein. The drastic effects on H2 activation derived from subtle ligand modifications have also been investigated. The importance of the balance between bimetallic adduct formation and complete frustration has been interrogated, providing for the first time evidence for genuine metal-only FLP reactivity in solution. The origin of a strong inverse kinetic isotopic effect has also been clarified, offering further support for the proposed bimetallic FLP-type cleavage of dihydrogen.

Evidence for Genuine Bimetallic Frustrated Lewis Pair Activation of Dihydrogen with Gold(I)/Platinum(0) Systems.

Invited for the cover of this issue is the group of Joaquín López-Serrano and Jesús Campos at the Consejo Superior de Investigaciones Científicas and the University of Sevilla. The image depicts the importance of balancing the degree of frustration/interaction in the splitting of H2 by AuI /Pt0 . Read the full text of the article at 10.1002/chem.201905793.

Metal-only Lewis Pairs of Rhodium with s, p and d-Block Metals.

Metal-only Lewis pairs (MOLPs) in which the two metal fragments are solely connected by a dative M→M bond represent privileged architectures to acquire fundamental understanding of bimetallic bonding. This has important implications in many catalytic processes or supramolecular systems that rely on synergistic effects between two metals. However, a systematic experimental/computational approach on a well-defined class of compounds is lacking. Here we report a family of MOLPs constructed around the RhI precursor [(η5 -C5 Me5 )Rh(PMe3 )2 ] (1) with a series of s, p and d-block metals, mostly from the main group elements, and investigate their bonding by computational means. Among the new MOLPs, we have structurally characterized those formed by dative bonding between 1 and MgMeBr, AlMe3 , GeCl2 , SnCl2 , ZnMe2 and Zn(C6 F5 )2, as well as spectroscopically identified the ones resulting from coordination to MBArF (M=Na, Li; BArF - =[B(C6 H2 -3,5-(CF3 )2 )4 ]- ) and CuCl. Some of these compounds represent unique examples of bimetallic structures, such as the first unambiguous cases of Rh→Mg dative bonding or base-free rhodium bound germylene and stannylene species. Multinuclear NMR spectroscopy, including 103 Rh NMR, is used to probe the formation of Rh→M bonds. A comprehensive theoretical analysis of those provides clear trends. As anticipated, greater bond covalency is found for the more electronegative acids, whereas ionic character dominates for the least electronegative nuclei, though some degree of electron sharing is identified in all cases.

Locking Y Lateral Canthopexy as a Treatment for Dry Eye Disease Caused by Eyelid Malposition.

PURPOSE: The signs and symptoms of dry eye disease (DED) can affect the quality of life of patients. This study analyzes whether locking Y lateral canthopexy improves patients' quality of life and in what way it does so (based on the ocular surface disease index questionnaire) and DED signs (measured by the fluorescein breakup time, tear osmolarity, Schirmer test, and corneal staining) in patients with DED caused by a eyelid malposition or impaired blink dynamics. METHODS: This was a case-control study. Forty eyes of 20 patients with DED and lateral canthal disinsertion examined at the University Hospital La Ribera during a 1-year period from November 2016 to November 2017. The 40 eyes were divided into 2 groups: Group 1 eyes that underwent locking Y lateral canthopexy (i.e., a plication of the superficial lateral canthal tendon to the lateral orbital rim periosteum); and group 2 eyes that underwent observational treatment, without surgery. Symptoms and signs in OU were recorded separately at baseline and 1 month after surgery. RESULTS: One month after surgery, the ocular surface disease index reduced in group 1 eyes when compared with those of group 2 (p = 0.001), fluorescein breakup time showed an improvement in the operated eyes (group 1) (p < 0.001) and corneal staining was reduced in group 1 after surgery (p = 0.012). The osmolarity results did not change when compared with eyes from group 2 (p < 0.001). CONCLUSIONS: Locking Y lateral canthopexy is an effective surgical technique for treating patients with evaporative dry eye caused by a lateral canthal tendón disinsertion by restoring proper eyelid closure and improving blinking dynamics. It improves DED signs and symptoms, thereby enhancing the quality of life of patients.

Base-Promoted, Remote C-H Activation at a Cationic (η5-C5Me5)Ir(III) Center Involving Reversible C-C Bond Formation of Bound C5Me5.

C-H bond activation at cationic [(η5-C5Me5)Ir(PMe2Ar')] centers is described, where PMe2Ar' are the terphenyl phosphine ligands PMe2ArXyl2 and PMe2ArDipp2. Different pathways are defined for the conversion of the five-coordinate complexes [(η5-C5Me5)IrCl(PMe2Ar')]+, 2(Xyl)+ and 2(Dipp)+, into the corresponding pseudoallyls 3(Xyl)+ and 3(Dipp)+. In the absence of an external Brønsted base, electrophilic, remote ζ C-H activation takes place, for which the participation of dicationic species, [(η5-C5Me5)Ir(PMe2Ar')]2+, is proposed. When NEt3 is present, the PMe2ArDipp2 system is shown to proceed via 4(Dipp)+ as an intermediate en route to the thermodynamic, isomeric product 3(Dipp)+. This complex interconversion involves a non-innocent C5Me5 ligand, which participates in C-H and C-C bond formation and cleavage. Remarkably, the conversion of 4(Dipp)+ to 3(Dipp)+ also proceeds in the solid state.

Correction to: Quantifying the extent of fistulotomy. How much sphincter can we safely divide? A three-dimensional endosonographic study.

In the Fig. 1 of the original published version of this article the numbers were switched as well as in the text of Results section, lines 5 and 6. The revised figure and the corrected text are now presented correctly in this article.

Activation of Small Molecules by the Metal-Amido Bond of Rhodium(III) and Iridium(III) (η5-C5Me5)M-Aminopyridinate Complexes.

We report the synthesis and structural characterization of five-coordinate complexes of rhodium and iridium of the type [(η5-C5Me5)M(N^N)]+ (3-M+), where N^N represents the aminopyridinate ligand derived from 2-NH(Ph)-6-(Xyl)C5H3N (Xyl = 2,6-Me2C6H3). The two complexes were isolated as salts of the BArF anion (BArF = B[3,5-(CF3)2C6H3]4). The M-Namido bond of complexes 3-M+ readily activated CO, C2H4, and H2. Thus, compounds 3-M+ reacted with CO under ambient conditions, but whereas for 3-Rh+, CO migratory insertion was fast, yielding a carbamoyl carbonyl species, 4-Rh+, the stronger Ir-Namido bond of complex 3-Ir+ caused the reaction to stop at the CO coordination stage. In contrast, 3-Ir+ reacted reversibly with C2H4, forming adduct 5-Ir+, which subsequently rearranged irreversibly to [Ir](H)(═C(Me)N(Ph)-) complex 6-Ir+, which contains an N-stabilized carbene ligand. Computational studies supported a migratory insertion mechanism, giving first a ß-stabilized linear alkyl unit, [Ir]CH2CH2N(Ph)-, followed by a multistep rearrangement that led to the final product 6-Ir+. Both ß- and α-H eliminations, as well as their microscopic reverse migratory insertion reactions, were implicated in the alkyl-to-hydride-carbene reorganization. The analogous reaction of 3-Rh+ with C2H4 originated a complex mixture of products from which only a branched alkyl [Rh]C(H)(Me)N(Ph)- (5-Rh+) could be isolated, featuring a ß-agostic methyl interaction. Reactions of 3-M+ with H2 promoted a catalytic isomerization of the Ap ligand from classical κ2-N,N' binding to κ-N plus η3-pseudoallyl coordination mode.

Dynamic Kinetic Resolution of Heterobiaryl Ketones by Zinc-Catalyzed Asymmetric Hydrosilylation.

A diastereo- and highly enantioselective dynamic kinetic resolution (DKR) of configurationally labile heterobiaryl ketones is described. The DKR proceeds by zinc-catalyzed hydrosilylation of the carbonyl group, thus leading to secondary alcohols bearing axial and central chirality. The strategy relies on the labilization of the stereogenic axis that takes place thanks to a Lewis acid-base interaction between a nitrogen atom in the heterocycle and the ketone carbonyl group. The synthetic utility of the methodology is demonstrated through stereospecific transformations into either N,N-ligands or appealing axially chiral, bifunctional thiourea organocatalysts.

Controlled and Reversible Stepwise Growth of Linear Copper(I) Chains Enabled by Dynamic Ligand Scaffolds.

Reversible stepwise chain growth in linear CuI assemblies can be achieved by using the dynamic, unsymmetric naphthyridinone-based ligand scaffolds L1 and L2. With the same ligand scaffolds, the length of the linear copper chain can be varied from two to three and four copper atoms, and the nuclearity of the complex is easily controlled by the stepwise addition of a CuI precursor to gradually increase the chain length, or by the reductive removal of Cu atoms to decrease the chain length. This represents a rare example of a stepwise controlled chain growth in extended metal atom chains (EMACs). All complexes are formed with excellent selectivity, and the mutual transformations of the complexes of different nuclearity were found to be fast and reversible. These unusual rearrangements of metal chains of different nuclearities were achieved by a stepwise "sliding" movement of the naphthyridinone bridging fragment along the metal chain.

A Cationic Unsaturated Platinum(II) Complex that Promotes the Tautomerization of Acetylene to Vinylidene.

Complex [PtMe2 (PMe2 ArDipp2 )] (1), which contains a tethered terphenyl phosphine (ArDipp2 =2,6-(2,6-i Pr2 C6 H3 )2 C6 H3 ), reacts with [H(Et2 O)2 ]BArF (BArF- =B[3,5-(CF3 )2 C6 H3 ]4- ) to give the solvent (S) complex [PtMe(S)(PMe2 ArDipp2 )]+ (2⋅S). Although the solvent molecule is easily displaced by a Lewis base (e.g., CO or C2 H4 ) to afford the corresponding adducts, treatment of 2⋅S with C2 H2 yielded instead the allyl complex [Pt(η3 -C3 H5 )(PMe2 ArDipp2 )]+ (6) via the alkyne intermediate [PtMe(η2 -C2 H2 )(PMe2 ArDipp2 )]+ (5). Deuteration experiments with C2 D2 , and kinetic and theoretical investigations demonstrated that the conversion of 5 into 6 involves a PtII -promoted HC≡CH to :C=CH2 tautomerization in preference over acetylene migratory insertion into the Pt-Me bond.