Synthetically Reversible, Proton-Mediated Nitrite N-O Bond Cleavage at a Dicopper Site.

A monocationic dicopper(I,I) nitrite complex [Cu(μ-κ:κ-ON)DPFN][NTf] () (DPFN = 2,7-bis(fluoro-di(2-pyridyl)methyl)-1,8-naphthyridine, NTf = N(SOCF)), was synthesized by treatment of a dicopper acetonitrile complex, [Cu(μ-MeCN)DPFN][NTf] (), with tetrabutylammonium nitrite ([BuN][NO]). DFT calculations indicate that is one of three linkage isomers that are close in energy and presumably accessible in solution. Reaction of the μ-κ:κ-ON complex with -TolSH produces nitrous acid (HONO) and the corresponding dicopper thiolate species via an acid-base exchange reaction.

Direct ladderization of cyclooctatetraene-containing, processable conjugated ladder polymers from annulated bis-zirconacyclopentadienes.

Conjugated ladder polymers (CLPs) are difficult yet captivating synthetic targets due to their fully unsaturated fused backbones. Inherent challenges associated with their synthesis often lead to low yields, structural defects, and insoluble products. Here a new method to form CLPs is demonstrated, utilizing a high-yielding dimerization of annulated zirconacyclopentadienes to form cyclooctatetraene (COT) monomer units.

Iron homo- and heterobimetallic complexes supported by a symmetrical dinucleating ligand.

The selective synthesis of biomimetic Fe/Mn complexes able to mimic the geometry and catalytic activity of enzymes possessing this cofactor is still a challenge. Herein, we discuss the stepwise synthesis, characterization, and magnetic properties of a Fe(II)/Mn(II) species and related Fe(II)/Fe(II) complexes.

Metal-Metal Redox Exchange to Produce Heterometallic Manganese-Cobalt Oxo Cubanes via a "Dangler" Intermediate.

Pendent metals bound to heterocubanes are components of well-known active sites in enzymes that mediate difficult chemical transformations. Investigations into the specific role of these metal ions, sometimes referred to as "danglers", have been hindered by a paucity of rational synthetic routes to appropriate model structures. To generate pendent metal ions bonded to an oxo cubane through a carboxylate bridge, the cubane Co(μ-O)(OAc)(-Bupy) (OAc = acetate, -Bupy = 4--butylpyridine) was exposed to various metal acetate complexes.

Diborane Reductions of CO and CS Mediated by Dicopper μ-Boryl Complexes of a Robust Bis(phosphino)-1,8-naphthyridine Ligand.

A dinucleating 1,8-naphthyridine ligand featuring fluorene-9,9-diyl-linked phosphino side arms (PNNP) was synthesized and used to obtain the cationic dicopper complexes , [(PNNP)Cu(μ-Ph)][NTf]; [NTf] = bis(trifluoromethane)sulfonimide, , [(PNNP)Cu(μ-CCPh)][NTf], and , [(PNNP)Cu(μ-OBu)][NTf]. Complex reacted with diboranes to afford dicopper μ-boryl species (, with μ-Bcat; cat = catecholate and , with μ-Bpin; pin = pinacolate) that are more reactive in C(sp)-H bond activations and toward activations of CO and CS, compared to dicopper μ-boryl complexes supported by a 1,8-naphthyridine-based ligand with di(pyridyl) side arms. The solid-state structures and DFT analysis indicate that the higher reactivities of and relate to changes in the coordination sphere of copper, rather than to perturbations on the Cu-B bonding interactions.

M-Ge-Si thermolytic molecular precursors and models for germanium-doped transition metal sites on silica.

The synthesis, thermolysis, and surface organometallic chemistry of thermolytic molecular precursors based on a new germanosilicate ligand platform, -OGe[OSi(OBu)], is described. Use of this ligand is demonstrated with preparation of complexes containing the first-row transition metals Cr, Mn, and Fe. The thermolysis and grafting behavior of the synthesized complexes, Fe{OGe[OSi(OBu)]} (FeGe), Mn{OGe[OSi(OBu)]}(THF) (MnGe) and Cr{OGe[OSi(OBu)]}(THF) (CrGe), was evaluated using a combination of thermogravimetric analysis; nuclear magnetic resonance (NMR), ultraviolet-visible (UV-Vis), and electron paramagnetic resonance (EPR) spectroscopies; and single-crystal X-ray diffraction (XRD).

A reference genome for the Andean cavefish Trichomycterus rosablanca (Siluriformes, Trichomycteridae): Building genomic resources to study evolution in cave environments.

Animals living in caves are of broad relevance to evolutionary biologists interested in understanding the mechanisms underpinning convergent evolution. In the Eastern Andes of Colombia, populations from at least two distinct clades of Trichomycterus catfishes (Siluriformes) independently colonized cave environments and converged in phenotype by losing their eyes and pigmentation. We are pursuing several research questions using genomics to understand the evolutionary forces and molecular mechanisms responsible for repeated morphological changes in this system.

A Ruthenophosphanorcaradiene as a Synthon for an Ambiphilic Metallophosphinidene.

Reaction of the ruthenium carbene complex Cp*(IPr)RuCl () (IPr = 1,3-bis(Dipp)imidazol-2-ylidene; Dipp = 2,6-diisopropylphenyl) with sodium phosphaethynolate (NaOCP) led to intramolecular dearomatization of one of the Dipp substituents on the Ru-bound carbene to afford a Ru-bound phosphanorcaradiene, . Computations by DFT reveal a transition state characterized by a concerted process whereby CO migrates to the Ru center as the P atom adds to the π system of the aryl group. The phosphanorcaradiene possesses ambiphilic properties and reacts with both nucleophilic and electrophilic substrates, resulting in rearomatization of the ligand aryl group with net P atom transfer to give several unusual metal-bound, P-containing main-group moieties.

A [CoSiH] Silylene Synthon Provides Modular Access to Homo- and Heterobimetallic [Co═Si═M] (M = Co, Fe) Silicide Complexes.

Base-stabilized [BP](H)CoSiH(DMAP) (, [BP] = PhB(CHPPr); DMAP = 4-dimethylaminopyridine) is a rare instance of a synthon for the simplest "parent" silylene complex (LM═SiH). Complex was accessed in high yields via double Si-H bond activation in SiH by [BP]Co(DMAP), and in solution, it undergoes rapid exchange between bound and free DMAP by an associative mechanism (as determined by variable-temperature H NMR dynamic studies). The DMAP ligand of is readily displaced by metal-based fragments that bind silicon and cleave the Si-H bonds of the SiH moiety to produce bimetallic [Co═Si═M] (M = Co, Fe) molecular silicides.

Prioritizing Endangered Species in Genome Sequencing: Conservation Genomics in Action with the First Platinum-Standard Reference-Quality Genome of the Critically Endangered European Mink L., 1761.

The European mink (Mustelidae) ranks among the most endangered mammalian species globally, experiencing a rapid and severe decline in population size, density, and distribution. Given the critical need for effective conservation strategies, understanding its genomic characteristics becomes paramount. To address this challenge, the platinum-quality, chromosome-level reference genome assembly for the European mink was successfully generated under the project of the European Mink Centre consortium.

A Chromosome-Level Reference Genome for the Black-Legged Kittiwake (Rissa tridactyla), a Declining Circumpolar Seabird.

Amidst the current biodiversity crisis, the availability of genomic resources for declining species can provide important insights into the factors driving population decline. In the early 1990s, the black-legged kittiwake (Rissa tridactyla), a pelagic gull widely distributed across the arctic, subarctic, and temperate zones, suffered a steep population decline following an abrupt warming of sea surface temperature across its distribution range and is currently listed as Vulnerable by the International Union for the Conservation of Nature. Kittiwakes have long been the focus for field studies of physiology, ecology, and ecotoxicology and are primary indicators of fluctuating ecological conditions in arctic and subarctic marine ecosystems.

Dimetalloylene (M-E-M) Complexes of Heavier Main Group Elements Ge, Sn, Pb, Bi via Cleavage of E-X Bonds (X=N(SiMe ) , OtBu) with an Iridium Hydride.

Reactions of the Ir hydride [ BDI ]IrH {BDI=(Dipp)NC(Me)CH(Me)CN(Dipp); Dipp=2,6-iPr C H } with E[N(SiMe ) ] (E=Sn, Pb) afforded the unusual dimeric dimetallotetrylenes ([ BDI ]IrH) (μ -E) in good yields. Moreover, ([ BDI ]IrH) (μ -Ge) was formed in situ from thermal decomposition of [ BDI ]Ir(H) Ge[N(SiMe ) ] . These reactions are accompanied by liberation of HN(SiMe ) and H through the apparent cleavage of an E-N(SiMe ) bond by Ir-H.

Scalable, accessible, and reproducible reference genome assembly and evaluation in Galaxy.

Improvements in genome sequencing and assembly are enabling high-quality reference genomes for all species. However, the assembly process is still laborious, computationally and technically demanding, lacks standards for reproducibility, and is not readily scalable. Here we present the latest Vertebrate Genomes Project assembly pipeline and demonstrate that it delivers high-quality reference genomes at scale across a set of vertebrate species arising over the last ~500 million years.

MHC class II genes mediate susceptibility and resistance to coronavirus infections in bats.

Understanding the immunogenetic basis of coronavirus (CoV) susceptibility in major pathogen reservoirs, such as bats, is central to inferring their zoonotic potential. Members of the cryptic Hipposideros bat species complex differ in CoV susceptibility, but the underlying mechanisms remain unclear. The genes of the major histocompatibility complex (MHC) are the best understood genetic basis of pathogen resistance, and differences in MHC diversity are one possible reason for asymmetrical infection patterns among closely related species.

Direct Transformation of SiH to a Molecular L(H)Co═Si═Co(H)L Silicide Complex.

The synthesis of bimetallic molecular silicide complexes is reported, based on the use of multiple Si-H bond activations in SiH at the metal centers of 14-electron LCo fragments (L = Tp″, HB(3,5-diisopropylpyrazolyl); [BPPz], PhB(CHPBu)(pyrazolyl)). Upon exposure of (Tp″Co)(μ-N) () to SiH, a mixture of (Tp″Co)(μ-H) () and (Tp″Co)(μ-H) () was formed and no evidence for Si-H oxidative addition products was observed. In contrast, [BPPz]-supported Co complexes led to Si-H oxidative additions with the generation of silylene and silicide complexes as products.

Controlled monodefluorination and alkylation of C(sp)-F bonds by lanthanide photocatalysts: importance of metal-ligand cooperativity.

The controlled functionalization of a single fluorine in a CF group is difficult and rare. Photochemical C-F bond functionalization of the sp-C-H bond in trifluorotoluene, PhCF, is achieved using catalysts made from earth-abundant lanthanides, (Cp)Ln(2--3,5- Bu-CH)(1-C{N(CH)N(Pr)}) (Ln = La, Ce, Nd and Sm, Cp = CMeH). The Ce complex is the most effective at mediating hydrodefluorination and defluoroalkylative coupling of PhCF with alkenes; addition of magnesium dialkyls enables catalytic C-F bond cleavage and C-C bond formation by all the complexes.

Expanded [23]-Helicene with Exceptional Chiroptical Properties via an Iterative Ring-Fusion Strategy.

Expanded helicenes are an emerging class of helical nanocarbons composed of alternating linear and angularly fused rings, which give rise to an internal cavity and a large diameter. The latter is expected to impart exceptional chiroptical properties, but low enantiomerization free energy barriers (Δ) have largely precluded experimental interrogation of this prediction. Here, we report the syntheses of expanded helicenes containing 15, 19, and 23 rings on the inner helical circuit, using two iterations of an Ir-catalyzed, site-selective [2 + 2 + 2] reaction.

Robust dicopper(i) μ-boryl complexes supported by a dinucleating naphthyridine-based ligand.

Copper boryl species have been widely invoked as reactive intermediates in Cu-catalysed C-H borylation reactions, but their isolation and study have been challenging. Use of the robust dinucleating ligand DPFN (2,7-bis(fluoro-di(2-pyridyl)methyl)-1,8-naphthyridine) allowed for the isolation of two very thermally stable dicopper(i) boryl complexes, [(DPFN)Cu(μ-Bpin)][NTf] (2) and [(DPFN)Cu(μ-Bcat)][NTf] (4) (pin = 2,3-dimethylbutane-2,3-diol; cat = benzene-1,2-diol). These complexes were prepared by cleavage of the corresponding diborane reaction with the alkoxide [(DPFN)Cu(μ-O Bu)][NTf] (3).

A sequential cyclization/π-extension strategy for modular construction of nanographenes enabled by stannole cycloadditions.

The synthesis of polycyclic aromatic hydrocarbons (PAHs) and related nanographenes requires the selective and efficient fusion of multiple aromatic rings. For this purpose, the Diels-Alder cycloaddition has proven especially useful; however, this approach currently faces significant limitations, including the lack of versatile strategies to access annulated dienes, the instability of the most commonly used dienes, and difficulties with aromatization of the [4 + 2] adduct. In this report we address these limitations the marriage of two powerful cycloaddition strategies.

Copper(III) Metallacyclopentadienes via Zirconocene Transfer and Reductive Elimination to an Isolable Phenanthrocyclobutadiene.

Despite the widespread use of copper catalysis for the formation of C-C bonds, debate about the mechanism persists. Reductive elimination from Cu(III) is often invoked as a key step, yet examples of its direct observation from isolable complexes remain limited to only a few examples. Here, we demonstrate that incorporation of bulky mesityl (Mes) groups into the α-positions of a phenanthrene-appended zirconacyclopentadiene, CpZr(2,5-Mes-phenanthro[9,10]C), enables efficient oxidative transmetalation to the corresponding, formal Cu(III) metallacyclopentadiene dimer.

Mechanistic Aspects of Cobalt-Oxo Cubane Clusters in Oxidation Chemistry.

Cobalt oxides are recognized as one of the most efficient earth-abundant catalysts for challenging oxidation chemistry, with substrates ranging from water to organic compounds. In these oxidations, cobalt-oxo species with formal oxidation states greater than 3 are commonly invoked as reactive intermediates. However, there is a dearth of mechanistic information regarding how these high-valent cobalt catalysts operate.

Versatile Fe-Sn Bonding Interactions in a Metallostannylene System: Multiple Bonding and C-H Bond Activation.

The metallostannylene Cp*(PrMeP)(H)Fe-SnDMP (; Cp* = η-CMe; DMP = 2,6-dimesitylphenyl), formed by hydrogen migration in a putative Cp*(PrMeP)HFe[Sn(H)DMP] intermediate, serves as a robust platform for exploration of transition-metal main-group element bonding and reactivity. Upon one-electron oxidation, expels H to generate the coordinatively unsaturated [Cp*(PrMeP)Fe═SnDMP][B(CF)] (), which possesses a highly polarized Fe-Sn multiple bond that involves interaction of the tin lone pair with iron. Evidence from EPR and Fe Mössbauer spectroscopy, along with DFT studies, shows that is primarily an iron-based radical with charge localization at tin.

C-H Activation by RuCoO Oxo Cubanes: Effects of Oxyl Radical Character and Metal-Metal Cooperativity.

High-valent multimetallic-oxo/oxyl species have been implicated as intermediates in oxidative catalysis involving proton-coupled electron transfer (PCET) reactions, but the reactive nature of these oxo species has hindered the development of an in-depth understanding of their mechanisms and multimetallic character. The mechanism of C-H oxidation by previously reported RuCoO cubane complexes bearing a terminal Ru-oxo ligand, with significant oxyl radical character, was investigated. The rate-determining step involves H atom abstraction (HAA) from an organic substrate to generate a Ru-OH species and a carbon-centered radical.

Scalable, Divergent Synthesis of a High Aspect Ratio Carbon Nanobelt.

Carbon nanobelts are molecules of high fundamental and technological interest due to their structural similarity to carbon nanotubes, of which they are molecular cutouts. Despite this attention, synthetic accessibility is a major obstacle, such that the few known strategies offer limited structural diversity, functionality, and scalability. To address this bottleneck, we have developed a new strategy that utilizes highly fused monomer units constructed via a site-selective [2 + 2 + 2] cycloaddition and a high-yielding zirconocene-mediated macrocyclization to achieve the synthesis of a new carbon nanobelt on large scale with the introduction of functional handles in the penultimate step.