Monomeric Two-coordinate Beryllium Imido and Boryloxide Complexes Featuring Be-N and Be-O Triple Bonds

The 2p elements possess a unique propensity to participate in multiple bonding. Realization of multiple bonding involving the 2s elements, however, is challenging and remains exceedingly rare. In this contribution, we present the syntheses, detailed characterization, and molecular structures of heteroleptic beryllium imido and boryloxide complexes of the type [(HCNDip)2YXBeAr(OEt2)n]m (Y,X = C,N or B,O; n = 0, 1; m = 1, 2; Dip = 2,6-iPr2C6H3) by salt metathesis and arene elimination approaches. Systematic adjustment of the steric demand of the aryl substituent resulted in the isolation of monomeric, two-coordinate beryllium imido and boryloxide complexes, (HCNDip)2CNBeTip (9, Tip = 2,4,6-iPr3C6H2) and (HCNDip)2BOBeArDip (12, ArDip = 2,6-Dip2C6H3), containing virtually linear C-N-Be-C and B-O-Be-C arrangements and extremely short Be-N (1.434(2) Å, 1.437(3) Å) and Be-O (1.4035(14) Å) bonds, respectively. These were shown by in-depth computational electronic structure and bonding analyses to possess unprecedented triple bond character. The Be-O bond in 12 constitutes the first s-block metal-oxygen multiple bond.

METTL3 Mediates Wnt/β-Catenin Pathway in Epithelial-Mesenchymal Transition of 16HBE Cells Induced by Beryllium Sulphate

Beryllium (Be) is a recognised environmental toxicant associated with pulmonary fibrosis. Epithelial-mesenchymal transition (EMT), a critical process in cell phenotype conversion, plays a key role in its pathophysiology. Methyltransferase-like 3 (METTL3), a major N6-methyladenosine methyltransferase, regulates gene expression and cellular functions. However, its role in Be-induced EMT remains unclear. In this study, human bronchial epithelial cell line (16HBE cells) were exposed to varying concentrations of beryllium sulphate (BeSO4) to assess changes in METTL3 expression. METTL3 overexpression vectors were constructed, and quantitative reverse transcription-polymerase chain reaction, western blotting and immunofluorescence were used to detect METTL3, EMT markers and Wingless/Integrated (Wnt)/β-catenin pathway proteins. The Wnt/β-catenin pathway inhibitor ICG-001 was also employed to explore the role of the Wnt/β-catenin pathway in BeSO4-induced EMT. The study demonstrated that BeSO4 suppressed METTL3 expression, induced EMT and activated the Wnt/β-catenin pathway in 16HBE cells. Both METTL3 overexpression and ICG-001 pretreatment mitigated BeSO4-induced EMT and Wnt/β-catenin pathway activation. These findings suggest that METTL3 inhibits BeSO4-induced EMT by suppressing the Wnt/β-catenin pathway, offering novel mechanistic insights into beryllium toxicity and a potential therapeutic target for Be-related pulmonary fibrosis.

Transmetalation From Boron to Beryllium in Phosphorus-Based Scorpionate Complexes

Investigation of tris(di-iso-propylphosphanylmethyl)phenylborate ([TP(iPr)]-) organo-beryllium complexes [TP(iPr)]BeR with R = Ph, nBu, Cp, Cp* revealed transmetalation of [CH2P(iPr)2]- groups from boron onto beryllium. This reaction is caused by partial dissociation of the scorpionate, which can be triggered through steric overcrowding of the beryllium atom or reducing the ligand beryllium bond strength through oxidation of the phosphorus atoms with selenium. Oxidation with oxygen or sulfur results in the formation of stable phosphine oxide and sulfide scorpionates.

Neutral Phosphorus-Based Beryllium Scorpionate Complexes as Spectroscopic Probes for Base Strength and Electron Donation

The synthesis and properties of tris(diisopropylphosphanylmethyl)phenylborate ([TP(iPr)]-) beryllium complexes [TP(iPr)]BeL with L = Cl, Br, I, CN, SCN, OCN, N3, and CF3SO3 are described. In these compounds, the 1JPBe NMR coupling constant can be used as a sensitive probe for the basicity and electron-donating properties of the L- anions in solution.

Challenges and Applications of Supramolecular Metalate Chemistry

While the supramolecular chemistry of simple anions is ubiquitous, the targeting and exploitation of their metal-containing relatives, the metalates, is less well understood. This mini review highlights the latest advances in this emergent area by discussing the supramolecular chemistry of metalates thematically, with a focus on the exploitation of metalates in a diversity of applications, including medical imaging and therapy, environmental remediation, molecular magnetism, catalysis, perovskite materials, and metal separations. The unifying features of these systems are identified with a view to allow the supramolecular chemist to target the unique material properties of the metalates, even in areas that are currently relatively immature.

Multinuclear beryllium amide and imide complexes: structure, properties and bonding

The beryllium amide and imide complexes [Be(HNMes)2]3, [(py)2Be(HNMes)2], [Be(HNDipp)2]2, [Be(NPh2)(μ2-HNDipp)]2 and [Be(NCPh2)2]3 have been prepared and characterised with NMR and IR spectroscopy as well as single crystal X-ray diffraction. Analysis of the localised molecular orbitals (LMOs) and intrinsic atomic orbital (IAO) atomic charges in the framework of the intrinsic bond orbital (IBO) localization method revealed a covalent bonding network consisting of 2-electron-2-centre and 2-electron-3-centre σ bonds, in which one electron pair of the anionic N-donor ligands is involved. The electron deficiency at the beryllium atoms is partially compensated through additional electron donation from the lone pair at the nitrogen atoms.

Multinuclear Beryllium Chloro Carboxylates

Reaction of 1 equiv of BeCl2 with mesityl (Mes) or o-tolyl (o-Tol) carboxylic acid in benzene gives hexanuclear heterocyles [BeCl(MesCO2)]6 and [BeCl(o-TolCO2)]6, respectively. Small amounts of the oxocarboxylates [Be4O(MesCO2)6] and [Be4O(o-TolCO2)6] are also formed. If chloroform is used as the solvent, a mixture of these complexes together with the unprecedented tertranuclear cage compounds [Be4Cl2(MesCO2)6] and [Be4Cl2(o-TolCO2)6] is obtained.

On the nature and limits of alkaline earth-triel bonding

The synthesis of a series of isostructural organometallic complexes featuring Ae-Tr bonds (Ae = Be, Mg; Tr = Al, Ga, In) has been investigated, and their electronic structures probed by quantum chemical calculations. This systematic study allows for comparison, not only of the metal-metal bonding chemistries of the two lightest alkaline earth (Ae) elements, beryllium and magnesium, but also of the three triel (Tr) elements, aluminium, gallium, and indium. Computational analyses (NBO, QTAIM, EDA-NOCV) reveal that Be-Tr bonding is more covalent than Mg-Tr bonding. More strikingly, these calculations predict that the beryllium-indyl complex - featuring the first structurally characterised Be-In bond - should act as a source of nucleophilic beryllium. This has been confirmed experimentally by its reactivity towards methyl iodide, which yields the Be-Me functionality. By extension, the electrophilic character of the beryllium centre in the beryllium-gallyl complex contrasts with the umpoled, nucleophilic behaviour of the beryllium centre in both the -indyl and -aluminyl complexes.

Formation, Structure and Reactivity of a Beryllium(0) Complex with Mgδ+-Beδ- Bond Polarization

Attempts to create a novel Mg-Be bond by reaction of [(DIPePBDI*)MgNa]2 with Be[N(SiMe3)2]2 failed; DIPePBDI*=HC[(tBu)C=N(DIPeP)]2, DIPeP=2,6-Et2C-phenyl. Even at elevated temperatures, no conversion was observed. This is likely caused by strong steric shielding of the Be center. A similar reaction with the more open Cp*BeCl gave in quantitative yield (DIPePBDI*)MgBeCp* (1). The crystal structure shows a Mg-Be bond of 2.469(4) Å. Homolytic cleavage of the Mg-Be bond requires ΔH=69.6 kcal mol-1 (cf. CpBe-BeCp 69.0 kcal mol-1 and (DIPPBDI)Mg-Mg(DIPPBDI) 55.8 kcal mol-1). Natural-Population-Analysis (NPA) shows fragment charges: (DIPePBDI*)Mg +0.27/BeCp* -0.27. The very low NPA charge on Be (+0.62) compared to Mg (+1.21) and the strongly upfield 9Be NMR signal at -23.7 ppm are in line with considerable electron density on Be and the formal oxidation state assignment of MgII-Be0. Despite this Mgδ+-Beδ- polarity, 1 is extremely thermally stable and unreactive towards H2, CO, N2, cyclohexene and carbodiimide. It reacted with benzophenone, azobenzene, phenyl acetylene, CO2 and CS2. Reaction with 1-adamantyl azide led to reductive coupling and formation of an N6-chain. The azide reagent also inserted in the Cp*-Be bond. The inertness of 1 is likely due to bulky ligands protecting the Mg-Be unit.

A nucleophilic beryllyl complex via metathesis at [Be-Be]2

Owing to its high toxicity, the chemistry of element number four, beryllium, is poorly understood. However, as the lightest elements provide the basis for fundamental models of chemical bonding, there is a need for greater insight into the properties of beryllium. In this context, the chemistry of the homo-elemental Be-Be bond is of fundamental interest. Here the ligand metathesis chemistry of diberyllocene (1; CpBeBeCp)-a stable complex with a Be-Be bond-has been investigated. These studies yield two complexes with Be-Be bonds: Cp*BeBeCp (2) and [K{(HCDippN)2BO}2]BeBeCp (3; Dipp = 2,6-diisopropylphenyl). Quantum chemical calculations indicate that the Be-Be bond in 3 is polarized to such an extent that the complex could be formulated as a mixed-oxidation state Be0/BeII complex. Correspondingly, it is demonstrated that 3 can transfer the 'beryllyl' anion, [BeCp]-, to an organic substrate, by analogy with the reactivity of sp2-sp3 diboranes. Indeed, this work reveals striking similarities between the homo-elemental bonding linkages of beryllium and boron, despite the respective metallic and non-metallic natures of these elements.

Mono-Ortho-Beryllated Carbodiphosphoranes: Synthesis, Structure, Bonding and Reactivity

The reaction of organoberyllium compounds with hexaphenylcarbodiphosphorane yields mono-ortho-beryllated complexes, which feature a double dative Be=C bond. The bonding situation in these compounds together with a simple carbodiphosphorane and an N-heterocyclic carbene adduct was analysed with energy decomposition analysis in combination with natural orbital for chemical valence as well as with quantum theory of atoms-in-molecules. Furthermore, the driving forces accountable for mono-ortho-beryllation were elucidated along with the reactivity of the Be=C bond.

Synthesis and Derivatives of Beryllium Triflate

Various pathways for the synthesis of beryllium triflate were investigated. The reaction of triflic acid or trimethylsilyl triflate with beryllium metal in liquid ammonia led to the formation of mono-, di-, and tetra-nuclear beryllium ammine complexes. Utilization of SMe2 as a solvent gave homoleptic Be(OTf)2. Various beryllium triflate complexes with N- and O-donor ligands as well as the complex anions [Be(OTf)4]2- and [Be2(OTf)6]2- were synthesized to evaluate the reactivity and solution properties of beryllium triflate. This showed that OTf- is not a weakly coordinating anion for Be2+ cations and that it exhibits good bridging properties.

Cesium Reduction of a Lithium Diamidochloroberyllate

Room temperature reaction of elemental cesium with the dimeric lithium chloroberyllate [{SiNDipp}BeClLi]2 [{SiNDipp} = {CH2SiMe2N(Dipp)}2, where Dipp = 2,6-di-isopropylphenyl, in C6D6 results in activation of the arene solvent. Although, in contrast to earlier observations of lithium and sodium metal reduction, the generation of a mooted cesium phenylberyllate could not be confirmed, this process corroborates a previous hypothesis that such beryllium-centered solvent activation also necessitates the formation of hydridoberyllium species. These observations are further borne out by the study of an analogous reaction performed in toluene, in which case the proposed generation of formally low oxidation state beryllium radical anion intermediates induces activation of a toluene sp3 C-H bond and the isolation of the polymeric cesium benzylberyllate, [Cs({SiNDipp}BeCH2C6H5)]∞.

Recent progress in beryllium organometallic chemistry

Beryllium possesses a unique amalgamation of characteristics, its electronegativity included, that not only make it a vital component in a wide range of technical sectors and consumer industries, but also make it an interesting candidate for forming covalently bonded compounds. However, the extremely toxic nature of beryllium, which can cause chronic beryllium disease, has limited the exploration of its chemistry, making beryllium one of the least studied (non-radioactive) elements. The development of selective chelating ligands, sterically encumbered substituents and, moreover, the boom of N-heterocyclic carbenes in organometallic chemistry and main group chemistry has revived the interest in beryllium chemistry. Therefore, some quite remarkable progress in the coordination and organometallic chemistry of beryllium has been made in the last two decades. For example, low oxidation state beryllium compounds, antiaromatic/aromatic beryllium compounds, where beryllium is involved in π-electron delocalization, and the isolation of beryllium-beryllium bonded species have all been achieved. This article provides an oversight over the recent developments in the organometallic chemistry of beryllium.

Alkaline earth metals: homometallic bonding

The study of alkaline earth metal complexes is undergoing a renaissance. Stable molecular species featuring Mg-Mg bonds were reported in 2007 and their reactivity has since been intensively investigated. Motivated by this work, efforts have also been devoted to the synthesis of complexes featuring Be-Be and Ca-Ca bonds. These collective endeavours have revealed that the chemistry of the group 2 metals is richer and more complex than had previously been appreciated. Here, a discussion of the nature of homometallic alkaline earth bonding is presented, recent synthetic advances are described, and future directions are considered.

Beryllium-Mediated Halide and Aryl Transfer onto Silicon

The reactivity of hexamethylcyclotrisiloxane (D3 ) towards BeCl2 , BeBr2 , BeI2 and [Be3 Ph6 ]3 was investigated. While BeCl2 only showed unselective reactivity, BeBr2 , BeI2 and [Be3 Ph6 ] cleanly react to the trinuclear complexes [Be3 Br2 (OSiMe2 Br)4 ], [Be3 I2 (OSiMe2 I)4 ] and [Be3 Ph2 (OSiMe2 Ph)4 ]. These unprecedented bromide, iodide and phenyl transfer reactions from a group II metal onto silicon offer a versatile access to previously unknown diorgano bromo and iodo silanolates.

Schlenk-Type Equilibria of Grignard-Analogous Arylberyllium Complexes: Steric Effects

The presence of complex Schlenk equilibria is a central property of synthetically invaluable Grignard reagents substantially affecting their reactivity and selectivity in chemical transformations. In this work, the steric effects of aryl substituents on the Schlenk-type equilibria of their lighter congeners, arylberyllium bromides, are systematically studied. Combination of diarylberyllium complexes Ar2 Be(OEt2 ) (1Ar, Ar=Tip, Tcpp; Tip=2,4,6-iPr3 C6 H3 , Tcpp=2,4,6-Cyp3 C6 H3 , Cyp=c-C5 H9 ), containing sterically demanding aryl groups, and BeBr2 (OEt2 )2 (2) affords the Grignard-analogous arylberyllium bromides ArBeBr(OEt2 ) (3Ar, Ar=Tip, Tcpp). In contrast, Mes2 Be(OEt2 ) (1Mes, Mes=2,4,6-Me3 C6 H3 ) and 2 exist in a temperature-dependent equilibrium with MesBeBr(OEt2 ) (3Mes) and free OEt2 . Ph2 Be(OEt2 ) (1Ph) reacts with 2 to afford dimeric [PhBeBr(OEt2 )]2 ([3Ph]2 ). Moreover, the influence of replacing the OEt2 donor by an N-heterocyclic carbene, IPr2 Me2 (IPr2 Me2 =C(iPrNCMe)2 ), on the redistribution reactions was investigated. The solution- and solid-state structures of the diarylberyllium and arylberyllium bromide complexes were comprehensively characterized using multinuclear (1 H, 9 Be, 13 C) NMR spectroscopic methods and single-crystal X-ray diffraction, while DFT calculations were employed to support the experimental findings.

A Preference for Heterolepticity - Schlenk Type Equilibria in Organometallic Beryllium Systems

The reaction of homoleptic beryllium halide with diphenyl beryllium complexes leads to the clean formation of heteroleptic beryllium Grignard compounds [(L)1-2 BePhX]1-2 (X=Cl, Br, I; L=C-, N-, O-donor ligand). The influence of ligands and solvent on these compounds, their formation and exchange equilibria in solution were investigated, together with the factors determining the complex constitution.

Gauging ambiphilicity of pseudo-halides via beryllium-trispyrazolylborato compounds

The ambiphilicity of pseudo-halides has been the object of extensive debate. Herein, we use a series of trispyrazolylborato beryllium pseudo-halido complexes [TpBe(X')] with X' = CN-, N3-, NCO- and NCS- to explore the origins of the preferred isomers. Thus, we have synthesised and characterised through NMR and IR spectroscopy as well as single crystal X-ray diffraction these complexes. A combination with quantum chemical calculations within the DFT framework enabled an in-depth understanding of the bonding modes and preferences of the investigated pseudo-halido ligands.

Diberyllocene, a stable compound of Be(I) with a Be-Be bond

The complex diberyllocene, CpBeBeCp (Cp, cyclopentadienyl anion), has been the subject of numerous chemical investigations over the past five decades yet has eluded experimental characterization. We report the preparation and isolation of the compound by the reduction of beryllocene (BeCp₂) with a dimeric magnesium(I) complex and determination of its structure in the solid state by means of x-ray crystallography. Diberyllocene acts as a reductant in reactions that form beryllium-aluminum and beryllium-zinc bonds. Quantum chemical calculations indicate parallels between the electronic structure of diberyllocene and the simple homodiatomic species diberyllium (Be₂).

Ligand exchange at tetra-coordinated beryllium centres

Mono and dinuclear phosphine complexes of beryllium halides [(PMe₃)₂BeX₂], [(PMe₃)BeX₂]₂ and [(PCy₃)BeX₂]₂ (X = Cl, Br, I) were synthesised and characterised via NMR and IR spectroscopy as well as single crystal X-ray diffraction experiments. Dissociation and ligand exchange processes at these complexes were investigated through variable temperature NMR experiments in combination with line shape analysis and complemented by quantum chemical calculations. The PMe₃ dissociation energy is smallest in [(PMe₃)₂BeCl₂], while PMe₃ exchange is similar in energy in all mononuclear [(PMe₃)₂BeX₂] complexes and follows an interchange mechanism. While [(PMe₃)BeX₂]₂ dissociates homolytically, [(PCy₃)BeX₂]₂ cleaves one phosphine ligand. These distinctive dissociation processes account for the different chemical behaviour of these complexes.

Structure and spectroscopic properties of etherates of the beryllium halides

The synthesis of beryllium halide etherates and the solution behavior in benzene, dichloromethane, and chloroform was studied by NMR, IR, and Raman spectroscopy. Mononuclear units of [BeX 2(L)2] (X = Cl, Br, I; L = Et2O, thf) were identified as the favorably formed species in solution. Treatment of the mononuclear diethyl ether beryllium halide adduct with one equivalent beryllium halide formed the dinuclear compounds [BeX 2(OEt2)]2 (X = Cl, Br, I). The solid-state structures of [BeCl2(thf)2] and [BeBr2(thf)2] have been determined by single crystal X-ray diffraction analysis. [BeI2(thf)2] decomposed in all solvents. In CD2Cl2 the salt [Be(thf)4]I2 was formed, whereas in C6D6 and CDCl3, BeI2 precipitated and [BeI(thf)3]+, [Be(thf)4]2+ together with the thf ring-opening product [Be(μ 2-O(CH2)4I)I(thf)]2 were observed in solution.

The dubious origin of beryllium toxicity

Four mechanisms have been proposed in the literature to explain beryllium toxicity; they can be divided in two groups of two mechanisms: (i) replacement type: models 1 and 2; (ii) addition type: models 3 and 4. At this moment is not possible to select the best model not even to establish if one of these models will be the ultimate mechanism of beryllium toxicity. However, it is important to know the still open discussion about something so important associated with one of the simplest elements of the periodic table.

Inducing Nucleophilic Reactivity at Beryllium with an Aluminyl Ligand

The reactions of anionic aluminium or gallium nucleophiles {K[E(NON)]}₂ (E = Al, 1; Ga, 2; NON = 4,5-bis(2,6-diisopropylanilido)-2,7-ditert-butyl-9,9-dimethylxanthene) with beryllocene (BeCp₂) led to the displacement of one cyclopentadienyl ligand at beryllium and the formation of compounds containing Be-Al or Be-Ga bonds (NON)EBeCp (E = Al, 3; Ga, 4). The Be-Al bond in the beryllium-aluminyl complex [2.310(4) Å] is much shorter than that found in the small number of previous examples [2.368(2) to 2.432(6) Å], and quantum chemical calculations suggest the existence of a non-nuclear attractor (NNA) for the Be-Al interaction. This represents the first example of a NNA for a heteroatomic interaction in an isolated molecular complex. As a result of this unusual electronic structure and the similarity in the Pauling electronegativities of beryllium and aluminium, the charge at the beryllium center (+1.39) in 3 is calculated to be less positive than that of the aluminium center (+1.88). This calculated charge distribution suggests the possibility for nucleophilic behavior at beryllium and correlates with the observed reactivity of the beryllium-aluminyl complex with N,N'-diisopropylcarbodiimide─the electrophilic carbon center of the carbodiimide undergoes nucleophilic attack by beryllium, thereby yielding a beryllium-diaminocarbene complex.

Beryllium-centred C-H activation of benzene

Reaction of BeCl₂ with the dilithium diamide, [{SiN^Dipp}Li₂] ({SiN^Dipp} = {CH₂SiMe₂NDipp}₂), provides the dimeric chloroberyllate, [{SiN^DippBeCl}Li]₂, en route to the 2-coordinate beryllium amide, [SiN^DippBe]. Lithium or sodium reduction of [SiN^DippBe] in benzene, provides the relevant organoberyllate products, [{SiN^DippBePh}M] (M = Li or Na), via the presumed intermediacy of transient Be(I) radicals.

Bonding situations in tricoordinated beryllium phenyl complexes

The bonding situation in the tricoordinated beryllium phenyl complexes [BePh₃ ]^- , [(pyridine)BePh₂ ] and [(trimethylsilyl-N-heterocyclic imine)BePh₂ ] is investigated experimentally and computationally. Comparison of the NMR spectroscopic properties of these complexes and of their structural parameters, which were determined by single crystal X-ray diffraction experiments, indicates the presence of π-interactions. Topology analysis of the electron density reveals elliptical electron density distributions at the bond critical points and the double bond character of the beryllium-element bonds is verified by energy decomposition analysis with the combination of natural orbital for chemical valence. The present beryllium-element bonds are highly polarized and the ligands around the central atom have a strong influence on the degree of π-delocalization. These results are compared to related triarylboranes.

Reactivity of Diphenylberyllium as a Brønsted Base and Its Synthetic Application

Diphenylberyllium [Be₃Ph₆] is shown here to react cleanly as a Brønsted base with a vast variety of protic compounds. Through the addition of the simple molecules tBuOH, HNPh₂ and HPPh₂, as well as the more complex 1,3‐bis‐(2,6‐diisopropylphenyl)imidazolinium chloride, one or two phenyl groups in diphenylberyllium were protonated. As a result, the long‐postulated structures of [Be₃(OtBu)₆] and [Be(μ‐NPh₂)Ph]₂ have finally been verified and shown to be static in solution. Additionally [Be(μ‐PPh₂)(HPPh₂)Ph]₂ was generated, which is only the second beryllium‐phospanide to be prepared; the stark differences between its behaviour and that of the analogous amide were also examined. The first crystalline example of a beryllium Grignard reagent with a non‐bulky aryl group has also been prepared; it is stabilised with an N‐heterocyclic carbene.

Supramolecular Incarceration and Extraction of Tetrafluoroberyllate from Water by Nanojars

The previously unexplored noncovalent binding of the highly toxic tetrafluoroberyllate anion (BeF₄^2-) and its extraction from water into organic solvents are presented. Nanojars resemble anion-binding proteins in that they also possess an inner anion binding pocket lined by a multitude of H-bond donors (OH groups), which wrap around the incarcerated anion and completely isolate it from the surrounding medium. The BeF₄-binding propensity of [BeF₄⊂{Cu^II(OH)(pz)}_n]^2- (pz = pyrazolate; n = 27-32) nanojars of different sizes is investigated using an array of techniques including mass spectrometry, paramagnetic ¹H, ⁹Be, and ¹⁹F NMR spectroscopy, and X-ray crystallography, along with thermal stability studies in solution and chemical stability studies toward acidity and Ba²⁺ ions. The latter is found to be unable to precipitate the insoluble BaBeF₄ from nanojar solutions, indicating a very strong binding of the BeF₄^2- anion by nanojars. ⁹Be and ¹⁹F NMR spectroscopy allows for the unprecedented direct probing of the incarcerated anion in a nanojar and, along with ¹H NMR studies, reveals the fluxional structure of nanojars and their inner anion-binding pockets. Single-crystal X-ray diffraction provides the crystal and molecular structures of (Bu₄N)₂[BeF₄⊂{Cu(OH)(pz)}₃₂], which contains a novel Cu_x-ring combination (x = 9 + 14 + 9), (Bu₄N)₂[BeF₄⊂{Cu(OH)(pz)}₈₊₁₄₊₉], and (Bu₄N)₂[BeF₄⊂{Cu(OH)(pz)}_6+12+10] and offers detailed structural parameters related to the supramolecular binding of BeF₄^2- in these nanojars. The extraction of BeF₄^2- from water into organic solvents, including the highly hydrophobic solvent n-heptane, demonstrates that nanojars are efficient binding and extracting agents not only for oxoanions but also for fluoroanions.

Hydrolysis and oxidation products of phosphine adducts to beryllium chloride

The synthesis of bis(diphenylphosphino)ethane (dppe) and PMe3 mono-adducts [(dppe)BeCl2]n and [(PMe3)BeCl2]2 is described and their spectroscopic properties discussed. Hydrolysis of these two compounds and of the bis(diphenylphosphino)propane (dppp) adduct to BeCl2 gave [dppeH2][BeCl4], [Me3PH]n[Be4Cl9]n and [dpppH2][Be2Cl6], which have been isolated and structurally characterized by single crystal X-ray diffraction. The reactions of [(PMe3)BeCl2]2 with p-cresole gave [Me3PH]2[Be2Cl4(OC7H7)2]. This phenoxide together with [(Me3PO)2Be2Cl4], the oxidation product of [(PMe3)BeCl2]2, have also been structurally characterized.

π Back-Donation from a Beryllium Dibromide Fragment at the Expense of Its σ Strength

It is common knowledge that metal-to-ligand π back-donation requires filled atomic orbitals at the metal center. However, we show through a combined experimental and theoretical approach that Be(II)→N-heterocyclic carbene (NHC) π back-donation is present in the two carbene adducts [(iPr)BeBr₂] (1) and [(iPr)₂BeBr₂] (2) (iPr = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene). These complexes were characterized with NMR, IR, and Raman spectroscopy as well as with single-crystal X-ray diffractometry. The unusual bonding situation is understood from the results of energy decomposition analysis in combination with natural orbital for chemical valence and quantum theory of atoms-in-molecules analysis. The obtained findings shed light on the unusually high Be-C bond strength in carbene adducts to beryllium compounds and rationalize their geometry and reactivity.

Quinolino[7,8-h]quinoline: a 'just right' ligand for beryllium(II) coordination

We report the synthesis and crystal structure of the first quinolino[7,8-h]quinoline beryllium(II) complex of the general formula [BeL2(MeCN)Br]Br·MeCN, containing the ligand 4,9-dihydroxyquinolino[7,8-h]quinoline (L2). The Be(II) cation is a great size match for the dinitrogen binding pocket of the quinolino[7,8-h]quinoline ligand as indicated by minimal out-of-plane displacement and ligand distortion parameters.

s-Block chemistry in weakly coordinating solvents

Alkaline earth metal catalysis has been a growing field in recent years. To enhance reactivity and to understand the metal-substrate interactions in more detail, reactions are increasingly carried out in weakly coordinating solvents. This article gives an overview over the two main approaches to facilitate this, which are either through the employment of highly dipolar haloaryls as solvents, or by increasing the solubility of the ligand systems. The resulting coordination modes and reactivities are presented together with the synthetic strategies. Additionally, the latest results of group 1 complex chemistry in aliphatic solvents are illustrated and future challenges are highlighted.

Ligand Influence on Structural and Spectroscopic Properties of Beryllium Oxocarboxylates

Aluminum-based adjuvants for vaccines and beryllium ions interact with the same immune receptor. The Be₄O core, which is also found in beryllium oxocarboxylates, has been proposed to be the binding species in the latter case. However, this is not proven due to a lack of suitable probes for the Be₄O moiety. Therefore, a versatile synthetic route to beryllium oxocarboxylates has been developed to investigate the steric and electronic influence of the ligands onto their molecular and spectroscopic properties. The oxocarboxylates exhibit extremely narrow line widths in ⁹Be NMR spectroscopy, and the chemical shift is only influenced by the sterics of the ligands. The mean variation of the atomic distances in the central Be₄O building block is extremely small over all investigated compounds, and even the C-C distances are only little perturbed by the properties of the ligands. Vibrational spectroscopy showed Be-O bands; however, further distinctions could not be drawn.

An approach towards the synthesis of lithium and beryllium diphenylphosphinites

The diphenylphosphinites [(THF)Li(OPPh2)]4 and [(THF)2Be(OPPh2)2] have been synthesized via direct deprotonation of diphenylphosphine oxide with n BuLi and BePh2, respectively, as well as via salt metathesis. These compounds were characterized by multinuclear NMR spectroscopy, and the side-products of the reactions obtained under various reaction conditions have been identified. The beryllium derivative could not be isolated and decomposed into diphosphine oxide Ph2PP(O)Ph2. The solid-state structure of this final product together with that of [(THF)Li(OPPh2)]4 have been determined by single-crystal X-ray diffraction.

A Neutral Beryllium(I) Radical

The reduction of a cyclic alkyl(amino)carbene (CAAC)-stabilized organoberyllium chloride yields the first neutral beryllium radical, which was characterized by EPR, IR, and UV/Vis spectroscopy, X-ray crystallography, and DFT calculations.

Identification of beryllium fluoride complexes in mechanically distorted gels using quadrupolar split 9Be NMR spectra resolved with solution-state selective cross-polarization

The uniformly anisotropic media afforded by hydrogels are being increasingly exploited in analytical (structure elucidation) nuclear magnetic resonance (NMR) spectroscopy, and in studies of mechanosensitive biophysical and biochemical properties of living cells. The 9Be NMR parameters of beryllium fluoride complexes formed in aqueous solutions are sensitive markers of the anisotropic molecular environments produced by gelatin gels. The electric quadrupole moment of the 9Be nucleus (spin I = 3/2) interacts with the electric field gradient tensor in a stretched (or compressed) gel, giving rise to the splitting of peaks in 9Be NMR spectra. These are in addition to those produced by scalar coupling to the 19F nuclei. Thus, an equilibrium mixture of beryllofluoride complexes (BeF2, BeF3-, and BeF42-) in mechanically distorted gels generates an envelope of overlapping 9Be NMR multiplets. In the present work, the multiplets were dissected apart by using selective excitation of 9Be-19F cross-polarization; and the spectral components were quantified with multi-parameter line-shape decomposition, coupled with SpinDynamica simulations. The effects of gel density and Bloom number (a measure of gelatin-gel rigidity under standard conditions of sample preparation) on residual quadrupolar splittings were examined. Cross-polarization experiments revealed a bimodal distribution of  residual quadrupolar coupling constants (RQC) of the BeF3- complexes. The average RQC of the dominant BeF3- population was ∼3 times larger than that of BeF42-. The secondary BeF3- population existed in a tetrahedral configuration. It was attributed to BeF3- complexes associated with negatively charged -COO- groups of the denatured collagen matrix.

N-Heterocyclic carbene, carbodiphosphorane and diphosphine adducts of beryllium dihalides: synthesis, characterisation and reduction studies

Reaction of several N-heterocyclic carbenes, a carbodiphosphorane, and bis(diphenylphosphino)ethane (DPPE) with [BeX2(OEt2)2] (X = Br or I) have yielded a variety of beryllium dihalide adduct complexes, all of which were crystallographically characterised. Attempts to reduce the compounds to low oxidation state beryllium complexes using a variety of reducing agents have been carried out, but were of limited success. However, reaction of [(IPr)BeBr2] (IPr = :C{(DipNCH)2}; Dip = 2,6-diisopropylphenyl) with the aluminium(i) heterocycle, [:Al(DipNacnac)] (DipNacnac = [HC(MeCNDip)2]-) afforded the adduct complex, [{(IPr)(Br)Be(μ-H)}2], while reduction of [(IPr)BeBr2] with potassium naphthalenide gave the beryllium naphthalenediyl complex, [(IPr)Be(C10H8)]. Furthermore, reaction of [{(DPPE)BeI2}∞], with [:Al(DipNacnac)] led to insertion of the Al centre of the heterocycle into a Be-I bond, and formation of a rare example of an Al-Be bonded complex, [(DPPE)(i)Be-Al(i)(DipNacnac)].

Ethylenediamine complexes of the beryllium halides and pseudo-halides

The suitability of ethylenediamine (en) as an alternative solvent to liquid ammonia in beryllium chemistry was evaluated. Therefore, BeF2, BeCl2, BeBr2, BeI2, [Be(NH3)4](N3)2, [Be(NH3)4](CN)2 and [Be(NH3)4](SCN)2 were reacted with ethylenediamine and analysed via NMR and IR spectroscopy. Additionally single crystal structures of [BeF2(en)]n, [Be(en)3]Cl2, [Be(en)3]Br2, [Be(en)2]I2·en, [Be(en)2](N3)2·en, [Be(en)2]4(SCN)7Cl and [Be3(OH)3(en)3][C2H9N2](SCN)4 were obtained. The anions were found to have a distinct influence on the solubility as well as on the species present in solution and the solid state, while ethylenediamine can act as mono- and bidentate ligand or as a crystal solvent.

CAl4Mg0/−: Global Minima with a Planar Tetracoordinate Carbon Atom

Isomers of CAl4Mg and CAl4Mg− have been theoretically characterized for the first time. The most stable isomer for both the neutral and anion contain a planar tetracoordinate carbon (ptC) atom. Unlike the isovalent CAl4Be case, which contains a planar pentacoordinate carbon atom as the global minimum geometry, replacing beryllium with magnesium makes the ptC isomer the global minimum due to increased ionic radii of magnesium. However, it is relatively easier to conduct experimental studies for CAl4Mg0/− as beryllium is toxic. While the neutral molecule containing the ptC atom follows the 18 valence electron rule, the anion breaks the rule with 19 valence electrons. The electron affinity of CAl4Mg is in the range of 1.96–2.05 eV. Both the global minima exhibit π/σ double aromaticity. Ab initio molecular dynamics simulations were carried out for both the global minima at 298 K for 10 ps to confirm their kinetic stability.

Behavior of beryllium halides and triflate in acetonitrile solutions

The solution behavior of beryllium halides and triflate in acetonitrile was studied by NMR, IR and Raman spectroscopy. Thereby mononuclear units [(MeCN)2BeX 2] (X = Cl, Br, I, OTf) were identified as dominant species in these solutions. The solid state structure of [(MeCN)2Be(OTf)2] has been determined by X-ray diffraction. If only one equivalent of MeCN is used the dinuclear compounds [(MeCN)BeX 2]2 (X = Cl, Br, I) are formed. Partial halide and triflate dissociation into the monomeric complexes as well as the formation of hetero-halide complexes [(MeCN)2BeClBr], [(MeCN)2BeClI] and [(MeCN)2BeBrI] was observed.