Trans Position Research Articles

Systematic Approach Revealed SERPING1 Splicing-Affecting Variants to be Highly Represented in the Czech National HAE Cohort

Hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE) is a rare and life-threatening condition characterized by recurrent localized edema. We conducted a systematic screening of SERPING1 defects in a cohort of 207 Czech patients from 85 families with C1-INH-HAE. Our workflow involved a combined strategy of sequencing extended to UTR and deep intronic regions, advanced in silico prediction tools, and mRNA-based functional assays. This approach allowed us to detect a causal variant in all families except one and to identify a total of 56 different variants, including 5 novel variants that are likely to be causal. We further investigated the functional impact of two splicing variants, namely c.550 + 3A > C and c.686-7C > G using minigene assays and RT-PCR mRNA analysis. Notably, our cohort showed a considerably higher proportion of detected splicing variants compared to other central European populations and the LOVD database. Moreover, our findings revealed a significant association between HAE type 1 missense variants and a delayed HAE onset when compared to null variants. We also observed a significant correlation between the presence of the SERPING1 variant c.-21 T > C in the trans position to causal variants and the frequency of attacks per year, disease onset, as well as Clinical severity score. Overall, our study provides new insights into the genetic landscape of C1-INH-HAE in the Czech population, including the identification of novel variants and a better understanding of genotype–phenotype correlations. Our findings also highlight the importance of comprehensive screening strategies and functional analyses in improving the C1-INH-HAE diagnosis and management.

Synthesis, characterization, DFT studies and biological assessment of palladium(II) complexes with imidazole derivatives

Six palladium(II) complexes (1–6) with 2-phenylimidazole (L1) and 1,2-dimethylimidazole (L2), were synthesized and characterized by elemental analyses, IR and NMR spectroscopy. The crystal structure of one of them ([Pd(2-phenylimidazole)2Br2], 1) was determined by X-ray crystallography. The palladium(II) ion in complex 1 is coordinated by two nitrogen atoms of 2-phenylimidazole and two bromide ions at trans positions, adopting a nearly regular square planar geometry. The structures of PdBr2 complexes {[Pd(2-phenylimidazole)2Br2] (1) and [Pd(1,2-dimethylimidazole)2Br2] (4)} as well as their chloride analogues, {[Pd(2-phenylimidazole)2Cl2] (1a) and [Pd(1,2-dimethylimidazole)2Cl2] (4a)} were predicted by DFT calculations. Complexes 1 and 1a appeared to be stabilized by a weak agostic interaction between palladium and hydrogen atoms. The energy of Pd⋯H bond was estimated to be 1.6 kcal/mol for both complexes that was comparable to the strength of Cl⋯H hydrogen bond in 1a (1.7 kcal/mol). The complexes were examined for various biological activities including; antimicrobial, antioxidant and anti-diabetic assays. The complexes exhibited moderate antimicrobial activities but they were not good as antioxidants. However, the alpha amylase inhibition assay showed the excellent anti-diabetic effect of the complexes.

Theoretical Measurements of Quantitative Effects Caused by Spectator Ligands on Palladium-catalyzed C–H Activation

Ligands can definitely influence C–H activation at the metal center. A ligand not directly participating in the reaction is called a spectator ligand. We attempt to quantitatively characterize the effects of diverse spectator ligands on C-H activation at palladium. We designed a model palladium catalyst and selected an array of spectator ligands, such as methoxyl, amide, methyl, phenyl, cyanide, fluorine, chlorine, and several neutral ligands, and performed density functional theory calculations on the mechanism and energetics of C–H activation reactions of benzene with different catalysts. Univalent ligands have substantially larger effects than neutral ligands, and strongly σ-donating ligands (e.g., methyl and phenyl) severely hinder the C-H activation in progress. A ligand trans to the reaction site influences C–H activation more than that cis to the reaction site, indicating electronic effects to be at work. For example, the existence of a methyl ligand raises the barrier height of C-H activation by 6.4 or 14.4 kcal/mol when it is placed at the position cis or trans to the C–H activation site. The effects of poorly σ-donating ligands are not significant and similar to those of the κ1-acetate ligand. Some σ-donating and π-accepting ligands, such as cyanide and isonitrile, hinder the C–H activation trans to them but appear to facilitate the C–H activation cis to them. On the basis of molecular orbital analyses, a chemical model is proposed to understand the observed ligand effects. Lastly, the conclusions are applied to explain the plausible mechanism of the dehydrogenative Heck coupling.

Band Gap Engineering in Two-Dimensional Materials by Functionalization: Methylation of Graphene and Graphene Bilayers.

Graphene is well-known for its unique combination of electrical and mechanical properties. However, its vanishing band gap limits the use of graphene in microelectronics. Covalent functionalization of graphene has been a common approach to address this critical issue and introduce a band gap. In this Article, we systematically analyze the functionalization of single-layer graphene (SLG) and bilayer graphene (BLG) with methyl (CH3) using periodic density functional theory (DFT) at the PBE+D3 level of theory. We also include a comparison of methylated single-layer and bilayer graphene, as well as a discussion of different methylation options (radicalic, cationic, and anionic). For SLG, methyl coverages ranging from 1/8 to 1/1, (i.e., the fully methylated analogue of graphane) are considered. We find that up to a coverage θ of 1/2, graphene readily accepts CH3, with neighbor CH3 groups preferring trans positions. Above θ = 1/2, the tendency to accept further CH3 weakens and the lattice constant increases. The band gap behaves less regularly, but overall it increases with increasing methyl coverage. Thus, methylated graphene shows potential for developing band gap-tuned microelectronics devices and may offer further functionalization options. To guide in the interpretation of methylation experiments, vibrational signatures of various species are characterized by normal-mode analysis (NMA), their vibrational density of states (VDOS), and infrared (IR) spectra, the latter two are obtained from ab initio molecular dynamics (AIMD) in combination with a velocity-velocity autocorrelation function (VVAF) approach.

Synthesis, NMR, IR, Raman spectra and DFT calculations of 1‐octyl‐1,4‐diazabicyclo [2.2.2] octan‐1‐ium bis(trifluoromethylsulfonyl)imide

In this study, a novel [C8DABCO+] [(CF3SO2)2N−] ionic liquid (IL) was prepared by an alkylation reaction and then characterized it by experimental 1H-, 13C-, and 19F-NMR, IR and Raman spectroscopies together with B3LYP/6-311G** calculations in gas phase and aqueous solution to confirm its structure. DSC and TGA measurements show that it can be classified as a thermally stable ionic liquid. Three different structures (I), (II) and (III) were proposed for the IL with Cis and Trans positions of CF3 groups of anion evidencing better correlations among experimental and predicted spectra for structure (III). Strong S-O···H interactions were predicted in the gas phase while in solution the C-F···H distance is shorter (2.654 Å) than the S-O···H ones (2.827 Å). The analysis of MK charges reveals the presence of positive charges on quaternary N23 atoms both in vaccum and in solution; conversely positive Mulliken charges reside on O49 and O50 in the gas phase, while negative ones are found in solution. Molecular Electrostatic potential (MEP) surfaces support the electrophilic sites on quaternary N23 while the nucleophilic sites are observed on O, N and F atoms of the anion. NBO and AIM calculations reveal the characteristics of cation-anion interactions in the two media, as supported by the different f(νN-C), f(νSO2), f(δSO2) and f(δCH2) force constants values. Gap values suggest that [C8DABCO+] [(CF3SO2)2N−] is less reactive than [C8DABCO+] [Br−] while the characteristics of frontier orbitals justify the cation-anion interactions and support the important role of 1,4-diazabicyclo [2.2.2] octane (DABCO) in the properties of [C8DABCO+] [(CF3SO2)2N−] IL in both media. The complete assignments of 174 vibration modes expected for [C8DABCO+] [(CF3SO2)2N−] IL are reported together with the scaled force constants.

Two new JK silencing alleles identified by single molecule sequencing with 20-Kb long-reads.

The Kidd blood group gene SLC14A1 (JK) accounts for approximately 20 Kb from initiation codon to stop codon in the genome. In genomic DNA analysis using Sanger sequencing or short-read-based next generation sequencing, it is difficult to determine the cis or trans positions of single nucleotide variations (SNVs), which are occasionally more than 1 Kb away from each other. We aimed to determine the complete nucleotide sequence of a 20-Kb genomic DNA amplicon to characterize the JK allelic variants associated with Kidd antigen silencing in a blood donor. The Jk(a-b-) phenotype was identified in this donor by standard serological typing. A DNA sample obtained from whole blood was amplified by long-range PCR to obtain a 20-Kb fragment of the SLC14A1 gene, including the initiation and stop codons. The fragment was then analyzed by Sanger sequencing and single-molecule sequencing. Transfection and expression studies were performed in CHO cells using the expression vector construct of JK alleles. Sanger sequencing and single-molecule sequencing revealed that the donor was heterozygous with JK*01 having c.276G>A (rs763262711, p.Trp92Ter) and JK*02 having c.499A>G (rs2298719, p.Met167Val), c.588A>G (rs2298718, p.Pro196Pro), and c.743C>A (p.Ala248Asp). The two JK alleles identified have not been previously described. Transfection and expression studies indicated that the CHO cells transfected with JK*02 having c.743C>A did not express the Jkb and Jk3 antigens. We identified new JK silencing alleles and their critical SNVs by single-molecule sequencing and the findings were confirmed by transfection and expression studies.

Molybdenum(VI) complexes with a chiral l-alanine bisphenol [O,N,O,O’] ligand. Synthesis, structure, spectroscopic properties and catalytic activity

Dioxidomolybdenum(VI) compound [MoO2Cl2(dmso)2] reacts with a chiral tetradentate O3N-type l-alanine bisphenol ligand precursor (Et3NH)H2Lala to form an oxidochloridomolybdenum(VI) complex [MoOCl(Lala)] (1) as two separable geometric isomers with phenolate groups in cis or trans positions. The single crystal X-ray and NMR analyses of cis- and trans-1 reveal that the complexes are formed of monomeric molecules, in which the ligand has a tetradentate coordination through three oxygen donors and one nitrogen donor. The reaction of Na2MoO4·2H2O with the same ligand precursor in an acidic methanol solution leads to the formation of an anionic dioxido complex (Et3NH)[MoO2(Lala)] (2) with a trans coordination of the tetradentate ligand. Trans-1 and 2 were studied as active catalysts for olefin epoxidation: i.e. styrene, cyclohexene, S(–)-limonene and (–)-α-pinene using H2O2 and tBuOOH as oxidants.

Cobalt(II), nickel(II), palladium(II) and zinc(II) metallothiosemicarbazones: Synthesis, characterization, X-ray structures and biological activity

Metal(II) complexes of the type [Co(S-HL)2Cl2] and [Ni(N,S-L)2], [Pd(N,S-L)2], [Zn(N,S-L)2], were synthesized from the reaction of HL with metal(II) chlorides. All complexes were characterized by spectroscopic methods, such as elemental analysis, FT-IR, 1H NMR, and single crystal X-ray diffraction. In the [Co(S-HL)2Cl2] complex, the cobalt atom adopts a distorted tetrahedral geometry around the cobalt(II) ion, with two neutral monodentate S-thiosemicarbazone ligands coordinating via one of the thiocarbonyl sulfur atom and two chlorides. In the [Ni(N,S-L)2] and [Pd(N,S-L)2] complexes, HL ligand is coordinated with the metal center, as a mono anionic bidentate N,S donors which are in trans position and that metal(II) ions adopt square planar coordination. [Zn(N,S-L)2] indicates that the anionic thiosemicarbazone ligands bind to the metal in a distorted tetrahedral arrangement with N,S donor atoms. The antimicrobial activity of the ligand and metal(II) complexes were studied against bacterial strains and fungal stain. It was observed that the ligand showed weaker activity than the metal complexes. The Zn(II) complex had the best antibacterial activity against E. faecalis, while the Co(II) complex showed the best activity against S. aureus bacteria. Co(II) and Pd(II) complexes were relatively more effective against Gram-negative bacteria. It was determined that metal complexes were less effective against gram negative bacteria compared to gram positive bacteria. A little antifungal activity was observed in Zn(II) and Co(II) complexes.

CRYSTAL AND MOLECULAR STRUCTURE OF THE ISLAND TETRANUCLEAR DIOXOMOLYBDENUM(VI) COMPLEX [MoO<sub>2</sub>(<i>L</i><sup>1</sup>)]<sub>4</sub> (H<sub>2</sub><i>L</i><sup>1</sup> IS ACETYLACETONE ISONICOTINOYLHYDRAZONE) WITH LARGE INTRA- AND INTERMOLECULAR CHANNELS

The solvated complex [МоО2(L1)]4dimethylformamide (I) was synthesized. Its structure wasdetermined by X-ray diffraction analysis. The crystal structure is composed of the tetranuclear complexes [МоО2(L1)]4 (Ia) as the structural units lying on crystallographic twofold axes. Both crystallographically independent molybdenum atoms are in a distorted octahedral coordination environment formed by two cis-О(oxo) ligands, two N(L1) atoms of two molecules Ia in trans positions to the О(oxo) ligands, and two О(L1) atoms of one complex molecule in cis positions to О(oxo) and trans to each other. Each (L1)2– ligand is coordinated to two Мо atoms in a tetradentate tridentate-chelating (2О, N) bridging (N) mode. The average bond lengths in complex Iа are as follows: Мо–О(oxo), 1.701 Å; Мо–N(L1), 2.460 (b) and 2.214 Å (c); Мо–О(L1), 1.980 Å. The О(oxo)–МоО–(oxo) bond angle is 105.6°. The ordered dimethylformamide molecule is located in a narrow channel in the structure. The strongly disordered (non-located) solvent molecules (methanol/dimethylformamide/water) occupy wide channels in the structure of I.

Novel hybrid composites based on double-decker silsesquioxanes functionalized by methacrylate derivatives and polyvinyl alcohol as potential materials utilized in biomedical applications

The use of diverse biomaterials for regenerative medicine is constantly evolving. Therefore, looking for easy-to-scale-up materials in terms of preparation, less complex composition, and featuring structural and chemical stability seems justified. In this work, we report the preparation of double-decker silsesquioxane-based (DDSQ-based) composites, which, according to our best knowledge, have never been used as biomaterials. A family of methacrylate-substituted DDSQs was obtained starting from the previously reported hydroxyalkyl double-decker silsesquioxanes. In the resulting hybrids, methacrylate groups are attached to each other's lateral silicon atoms of DDSQ in trans positions, providing an excellent geometry for forming thin layers. In contrast to pure organic methacrylates, the covalent bonding of methacrylate derivatives to inorganic silsesquioxane core improves mechanics, cell adhesion, and migration properties. Furthermore, to increase the hydrophilicity of the resulting DDSQ-based hybrids, polyvinyl alcohol (PVA) was added. The entire system forms an easy-to-obtain two-component (DDSQ-PVA) composite, which was subjected without any upgrading additives to biological tests later in the research. The resulting biomaterials fulfill the requirements for potential medical applications. Human fibroblasts growing on prepared hybrid composites are characterized by proper spindle-shaped morphology, proliferation, and activation status similar to control conditions (cells cultured on PVA), as well as increased adhesion and migration abilities. The obtained results suggest that the prepared biomaterials may be used in regenerative medicine in the future.

Identification of over ten thousand candidate structured RNAs in viruses and phages

Structured RNAs play crucial roles in viruses, exerting influence over both viral and host gene expression. However, the extensive diversity of structured RNAs and their ability to act in cis or trans positions pose challenges for predicting and assigning their functions. While comparative genomics approaches have successfully predicted candidate structured RNAs in microbes on a large scale, similar efforts for viruses have been lacking. In this study, we screened over 5 million DNA and RNA viral sequences, resulting in the prediction of 10,006 novel candidate structured RNAs. These predictions are widely distributed across taxonomy and ecosystem. We found transcriptional evidence for 206 of these candidate structured RNAs in the human fecal microbiome. These candidate RNAs exhibited evidence of nucleotide covariation, indicative of selective pressure maintaining the predicted secondary structures. Our analysis revealed a diverse repertoire of candidate structured RNAs, encompassing a substantial number of putative tRNAs or tRNA-like structures, Rho-independent transcription terminators, and potentially cis-regulatory structures consistently positioned upstream of genes. In summary, our findings shed light on the extensive diversity of structured RNAs in viruses, offering a valuable resource for further investigations into their functional roles and implications in viral gene expression and pave the way for a deeper understanding of the intricate interplay between viruses and their hosts at the molecular level.

The influence of hydroxide to fluoride substitution in the trans-position to NO on the photochemistry of ruthenium nitrosyl complexes in the solid state and in solution

The substitution of the OH ligand in the trans position to NO in [RuNOPy2Cl2X] (X = F, OH) results in an increase of thermal stability of RuNO linkage isomers in the solid state, but decreases the quantum yield of the NO release in solution.

Challenging Ciscentric Feminist Margins: A South African Study on Gender-Based Violence in the Lives of Black Trans Women

Feminist discourses around the scourge of gender-based violence (GBV) have historically prioritized the voices and contextualities of cisgender heterosexual women, often to the exclusion of trans persons. In light of the continual invisibility of black trans persons and in particular black trans women in anti-GBV activism, this paper explores black trans women’s experiences of violence in post-apartheid South Africa. The study was undertaken from a transfeminist framework that asserts that the stories and histories of trans persons are central to the development of trans epistemologies within an inclusive gender liberation framework. The study followed a narrative methodological approach. Unstructured individual interviews were conducted with eight black trans women living in South Africa. Narratives of gender policing and punitive sexual violence in addition to narratives of cissexism as well as of the paradoxical hypervisibility and invisibility of black trans positions revealed violence meted against black trans women in South Africa as structural, grounded on a patriarchal matrix of cisgender power representing trans women as devalued others. Apartheid legacies of racialised economic marginalisation manifest as bearing a strong mediating role in shaping black trans women’s sustained vulnerability to violence. By addressing anti-trans violence as a feminist concern, this paper disrupts the ciscentricism of feminism, enabling more nuanced and inclusive constructions of GBV.

Anion Influence on Supramolecular Interactions in Exo-Coordinated Silver(I) Complexes with N2O2 Schiff Base Macrocycle

Silver(I) complexes with aza-oxa macrocyclic Schiff bases L (L = 1,5-diaza-2,4:7,8:16,17-tribenzo-9,15-dioxa-cyclooctadeca-1,5-dien) were prepared by the reaction of the corresponding macrocycle with four different silver salts (AgX; X = ClO4, PF6, SbF6 and BF4). In all four compounds, silver ions are exo-coordinated by two neighboring ligand molecules in linear and T-shaped geometries. Such a coordination mode results in the formation of infinite 1D polymeric chains. Compounds AgLClO4 and AgLBF4 are isostructural, and polymeric chains display 1D zigzag topology. In AgLPF6 there are three symmetrically unique Ag ions in the asymmetric unit of the compound. Two silver ions are linearly coordinated with two neighboring ligand molecules and are part of a discrete polymer chain. The third silver ion is coordinated with two ligand molecules and a methanol molecule in a T-shaped geometry. Such coordination geometry results in the formation of two discrete infinite polymer chains in the crystal structure. In the AgLSbF6 compound, the chain topology is a linear zigzag chain, but in this compound, there is a difference in the orientation of the Ag-N bond. The Ag-N-Ag bonds are in the trans position relative to the plane calculated through the ligand molecule, while the Ag-N bonds are in the cis position in all other compounds. Due to the presence of a bulky SbF6 anion, the ligand molecule is planar compared to other compounds. Considering intermolecular interactions, there is a huge variety of different interactions, mostly depending on the type of anion. A general supramolecular motif in all compounds is best described as 2D sheets of ligand–metal polymers with anions and solvent molecules sandwiched between them. In addition, the obtained compounds were characterized by IR spectroscopy and thermal analysis. The TG analysis indicates a rather surprising and considerable thermal stability of the prepared compounds, with some compounds thermally stable over 300 °C.

Magnetic and Dielectric Switchings Actuated by the Rotation of the Picoline Ligand in an Iron-Based Dinuclear Phase-Transition Complex.

Multifunctional materials with switchable magnetic and dielectric properties are crucial for the development of memory and sensor devices. Herein, we report a methoxy-bridged dinuclear iron-pyridyl complex [Fe2(4-picoline)4(NCS)4(μ-OCH3)2] (1), which shows simultaneous thermal-induced magnetic and dielectric switchings. Within the phase-transition temperature range, both magnetic switching and the dielectric anomaly were detected, in which the thermal hysteresis loops were 23 and 21 K, respectively. Detailed structural analyses revealed that these simultaneous switchings were rooted in the flexible rotatable ligands, which were actuated by readjusting the π-π intermolecular interactions between the pyridine ligands in the trans positions of the metal centers. These results were comprehensively investigated both experimentally and theoretically. This study presents a new guideline to control both the magnetic and dielectric properties of molecular complexes by external stimuli.

Coumarin-Ensembled Vanadium(V) Compounds and Their Affinity Studies Toward Biological Thiols Probed by Fluorescence Spectroscopy.

Fluorescence spectroscopic studies of a pair of new oxido-vanadium(V) compounds with biological thiols, such as homocysteine (Hcy), cysteine (Cys), and glutathione (GSH), have been investigated in this article. Despite notable progress in vanadium-thiol chemistry, no attention has been paid to exploring vanadium-based optical probes to study their interaction with biothiols. For this purpose, two oxido-vanadium(V) compounds, 1 and 2, have been prepared involving a tridentate ONO donor-based luminescent coumarin-derived ligand. Single crystal X-ray diffraction analysis, NMR (1 H, 13 C, and 51 V) spectroscopy, XPS, and DFT calculations have been used to establish their identities. The vanadium center in these compounds has a distorted octahedral environment. In compound 2, a methanol molecule is coordinated to the vanadium(V) center in the trans position of the terminal oxido moiety. The latter exerts a strong trans-labilizing influence on the coordinating methanol. Both 1 and 2 are weakly fluorescent. Photophysical investigations of the vanadium complexes in aqueous media at physiological pH (7.4) in the presence of various biothiols and amino acids showed significant fluorescence enhancement (83-fold) of the vanadium complexes, specifically with Hcy. The specific affinity of the complexes for Hcy remained unchanged even in the presence of other biothiols and amino acids. Kinetic investigation reveals pseudo-first order behavior of the compound with Hcy. Mechanistic studies have manifested that Hcy-induced reduction triggers the decomplexation of the vanadium compound, followed by hydrolysis and subsequent cyclization. Time-correlated single photon counting suggested that the radiative rate constant (kr ) of 1 and 2 in the presence of Hcy serves as the prime factor for the fluorescence enhancement of the medium. Compound 1 has been tested efficiently for Hcy measurement in blood plasma rendering it suitable for practical applications.

Cyclometalated platinum(II) complexes bearing natural arylolefin and quinolines ligands: Synthesis, characterizations, and in vitro cytotoxicity

Nine new cyclometalated platinum(II) complexes of the formula [PtCl(arylolefin)(Q)] (2, 3) and [Pt(arylolefin)(N,O)] (4–10) (arylolefinH: eugenoxyacetic acid, isopropyl eugenoxyacetate; Q: quinoline; (N,OH): quinolin-8-ol, 2-methylquinolin-8-ol, 5,7-dichloroquinloin-8-ol and quinoline-2-carboxylic acid] were synthesized and fully characterized by EA, ESI mass spectrometry, IR and NMR spectroscopy and single-crystal X-ray diffraction for 3, 7 and 10. The results show that the arylolefin binds with PtIIvia the C5 atom of the phenyl ring and the CC allyl in all the synthesized complexes. Quinoline coordinates with PtIIvia its N atom in 2, 3, while deprotonated (N,OH) coordinates with PtIIvia both the N and O atoms in 4–10. The N atom of Q and (N,O) in all complexes are at the cis position with respect to the allyl group of the arylolefin. The XRD confirms the square-planar coordination of PtII and trans position of the arylolefin and quinoline ligands. The results of in vitro cytotoxicity tests against human cancer cell lines KB and Lu of 2, 4–8 indicate that 4 and 5 exhibit the highest activities against Lu and KB cell lines with the IC50 values of 7.1 and 4.1 µM, respectively, which are approximately 6 and 4 times lower than cisplatin.

X-ray structure and magnetic properties of a mononuclear complex and a 1D coordination polymer assembled by cobalt(II) ions and a flexible oxamate ligand

This work describes the synthesis, crystal structures and direct current (dc) magnetic properties of two air-stable oxamato-containing cobalt(II) complexes, [Co(H2edpba)(dmso)2]·dmso·H2O (1) and [Co(H2edpba)(H2O)2] n ·n(dmso) (2) [H4edpba = N,N′-2,2′-ethylenediphenylenebis(oxamic acid); dmso = dimethylsulfoxide]. 1 is a mononuclear compound, whereas 2 is a neutral chain. Cobalt(II) ions in both compounds are six-coordinate by six oxygen atoms, four of them from two monodeprotonated oxamate groups and the other two from dmso (1)/water (2) molecules in cis (1) and trans (2) positions. Hydrogen bonds between monodeprotonated oxamate fragments of adjacent mononuclear units in 1 lead to a supramolecular chain growing along the crystallographic c axis. Hydrogen bonds involving coordinated water molecules and monodeprotonated oxamate fragments from adjacent chains in 2 result in a supramolecular 2D network. Cryomagnetic measurements reveal the occurrence of magnetically isolated high-spin cobalt(II) ions in agreement with the large values of the shortest intramolecular (1)/intrachain (2) metal···metal separation [ca. 10.3 (1) and 10.4 Å (2)]. Simultaneous simulation of the χ M T versus T and M against H data through the Griffith–Figgis Hamiltonian led to the best-fit parameters: λ = −141.1 (1)/–174.8 cm−1 (2), σ = −1.45 (1)/–1.25 (2) and ν = −121.42 (1)/−247.29 cm−1 (2).

Sterically and Electronically Flexible Pyridylidene Amine Dinitrogen Ligands at Palladium: Hemilabile cis/trans Coordination and Application in Dehydrogenation Catalysis.

Ligand design is crucial for the development of new catalysts and materials with new properties. Herein, the synthesis and unique hemilabile coordination properties of new bis-pyridylidene amine (bis-PYE) ligands to palladium, and preliminary catalytic activity of these complexes in formic acid dehydrogenation are described. The synthetic pathway to form cationic complexes [Pd(bis-PYE)Cl(L)]X with a cis-coordinated N,N-bidentate bis-PYE ligand is flexible and provides access to a diversity of PdII complexes with different ancillary ligands (L=pyridine, DMAP, PPh3 , Cl, P(OMe)3 ). The 1 H NMR chemical shift of the trans-positioned PYE N-CH3 unit is identified as a convenient and diagnostic handle to probe the donor properties of these ancillary ligands and demonstrates the electronic flexibility of the PYE ligand sites. In the presence of a base, the originally cis-coordinated bis-PYE ligand adopts a N,N,N-tridentate coordination mode with the two PYE units in mutual trans position. This cis-trans isomerization is reverted in presence of an acid, demonstrating a unique structural and steric flexibility of the bis-PYE ligand at palladium in addition to its electronic adaptability. The palladium complexes are active in formic acid dehydrogenation to H2 and CO2 . The catalytic performance is directly dependent on the ligand bonding mode, the nature of the ancillary ligand, the counteranion, and additives. The most active system features a bidentate bis-PYE ligand, PPh3 as ancillary ligand and accomplishes turnover frequencies up to 525 h-1 in the first hour and turnover numbers of nearly 1000, which is the highest activity reported for palladium-based catalysts to date.

Mechanistic Versatility at Ir(PSiP) Pincer Catalysts: Triflate Proton Shuttling from 2-Butyne to Diene and [3]Dendralene Motifs.

The five-coordinate hydrido complex [IrH(OTf)(PSiP)] (1) catalytically transforms 2-butyne into a mixture of its isomer 1,3-butadiene, and [3]dendralene and linear hexatriene dimerization products: (E)-4-methyl-3-methylene-1,4-hexadiene and (3Z)-3,4-dimethyl-1,3,5-hexatriene, respectively. Under the conditions of the catalytic reaction, benzene, and 363 K, the hexatriene further undergoes thermal electrocyclization into 2,3-dimethyl-1,3-cyclohexadiene. The reactions between 1 and the alkyne substrate allow isolation or nuclear magnetic resonance (NMR) observation of catalyst resting states and possible reaction intermediates, including complexes with the former PSiP pincer ligands disassembled into PSi and PC chelates, and species coordinating allyl or carbene fragments en route to products. The density functional theory (DFT) calculations guided by these experimental observations disclose competing mechanisms for C–H bond elaboration that move H atoms either classically, as hydrides, or as protons transported by the triflate. This latter role of triflate, previously recognized only for more basic anions such as carboxylates, is discussed to result from combining the unfavorable charge separation in the nonpolar solvent and the low electronic demand from the metal to the anion at coordination positions trans to silicon. Triflate deprotonation of methyl groups is key to release highly coordinating diene products from stable allyl intermediates, thus enabling catalytic cycling.