Spectroscopic Characterization, Computational Investigation, and Comparisons of ECX– (E = As, P, and N; X = S and O) Anions

Softer Is Better for Titanium: Molecular Titanium Arsenido Anions Featuring Ti≡As Bonding and a Terminal Parent Arsinidene

We introduce the arsenido ligand onto the TiIV ion, yielding a remarkably covalent Ti≡As bond and the parent arsinidene Ti═AsH moiety. An anionic arsenido ligand is assembled via reductive decarbonylation involving the discrete TiII salt [K(cryptand)][(PN)2TiCl] (1) (cryptand = 222-Kryptofix) and Na(OCAs)(dioxane)1.5 in thf/toluene to produce the mixed alkali ate-complex [(PN)2Ti(As)]2(μ2-KNa(thf)2) (2) and the discrete salt [K(cryptand)][(PN)2Ti≡As] (3) featuring a terminal Ti≡As ligand. Protonation of 2 or 3 with various weak acids cleanly forms the parent arsinidene [(PN)2Ti═AsH] (4), which upon deprotonation with KCH2Ph in thf generates the more symmetric anionic arsenido [(PN)2Ti(As){μ2-K(thf)2}]2 (5). Experimental and computational studies suggest the pKa of 4 to be ∼23, and the bond orders in 2, 3, and 5 are all in the range of a Ti≡As triple bond, with decreasing bond order in 4.

Understanding the Mechanism of Diels-Alder Reactions with Anionic Dienophiles: A Systematic Comparison of [ECX]- (E = P, As; X = O, S, Se) Anions

While Diels–Alder (DA) reactions involving neutral or cationic dienophiles are well-known, the characteristics of the analogous reactions with anionic dienophiles are practically unexplored. Herein we present the first comparative computational investigations on the characteristics of DA cycloadditions with anionic dienophiles on the basis of the reactions of [ECX]⁻ anions (E = P, As; X = O, S, Se) with 2H-pyran-2-one. All of these reactions were found to be both kinetically and thermodynamically feasible, enabling synthetic access toward 2-phosphaphenolate and arsaphenolate derivatives in the future. This study also reveals that the [ECO]⁻ anions show clear regioselectivity, while for [ECS]⁻ and [ECSe]⁻ anions, the two possible reaction channels have very similar energetics. Additionally, the activation barriers for the [ECO]⁻ anions are lower than those of the heavier analogues. The observed differences can be traced back to the starkly differing nucleophilic character of the pnictogen center in the anions, leading to a barrier-lowering effect in the case of the [ECO]⁻ anions. Furthermore, analysis of the geometries and electron distributions of the corresponding transition states revealed structure–property relationships, and thus a direct comparison of the cycloaddition reactivity of these anions was achieved. Along one of the two pathways, a good correlation was found between the activation barriers and suitable nucleophilicity descriptors (nucleophilic Parr function and global nucleophilicity). Additionally, the tendency of the reaction energies can be explained by the changing aromaticity of the products.

In contrast to the phosphaethynolate [PCO]⁻ anion, the cycloaddition reactivity of the heavier congeners ([ECX]⁻, where E = P, As and X = O, S, Se) is unexplored. In this computational study, the Diels−Alder reaction between the known [ECX]⁻ anions and 2-pyrone was employed to compare the reactivity patterns. The first activation barrier of these reactions correlates with the nucleophilicity of the anions, indicating a barrier-lowering effect. The feasibility of the studied reactions, leading to P and As heterocycles, was also explored.

Recent advances in the chemistry of the phosphaethynolate and arsaethynolate anions

Over the past decade, the reactivity of 2-phosphaethynolate (OCP^-), a heavier analogue of the cyanate anion, has been the subject of momentous interest in the field of modern organometallic chemistry. It is used as a precursor to novel phosphorus-containing heterocycles and as a ligand in decarbonylative processes, serving as a synthetic equivalent of a phosphinidene derivative. This perspective aims to describe advances in the reactivities of phosphaethynolate and arsaethynolate anions (OCE^-; E = P, As) with main-group element, transition metal, and f-block metal scaffolds. Further, the unique structures and bonding properties are discussed based on spectroscopic and theoretical studies.

π- delocalization in phosphaphthalimide and its ambident reactivity (O/P) toward main-group electrophiles

The report on phosphaphthalimide (1), the phosphorus analogue of the phthalimide anion, dates back to forty years ago. However, the presence of π-delocalization between two-coordinated phosphorus centre and neighbouring carbonyl...

Phosphorus-Atom Transfer from Phosphaethynolate to an Alkylidyne

A low-spin and mononuclear vanadium complex, (Me nacnac)V(CO)(η2 -P≡Ct Bu) (2) (Me nacnac- =[ArNC(CH3 )]2 CH, Ar=2,6-i Pr2 C6 H3 ), was prepared upon treatment of the vanadium neopentylidyne complex (Me nacnac)V≡Ct Bu(OTf) (1) with Na(OCP)(diox)2.5 (diox=1,4-dioxane), while the isoelectronic ate-complex [Na(15-crown-5)]{([ArNC(CH2 )]CH[C(CH3 )NAr])V(CO)(η2 -P≡Ct Bu)} (4), was obtained via the reaction of Na(OCP)(diox)2.5 and ([ArNC(CH2 )]CH[C(CH3 )NAr])V≡Ct Bu(OEt2 ) (3) in the presence of crown-ether. Computational studies suggest that the P-atom transfer proceeds by [2+2]-cycloaddition of the P≡C bond across the V≡Ct Bu moiety, followed by a reductive decarbonylation to form the V-C≡O linkage. The nature of the electronic ground state in diamagnetic complexes, 2 and 4, was further investigated both theoretically and experimentally, using a combination of density functional theory (DFT) calculations, UV/Vis and NMR spectroscopies, cyclic voltammetry, X-ray absorption spectroscopy (XAS) measurements, and comparison of salient bond metrics derived from X-ray single-crystal structural characterization. In combination, these data are consistent with a low-valent vanadium ion in complexes 2 and 4. This study represents the first example of a metathesis reaction between the P-atom of [PCO]- and an alkylidyne ligand.

Vibrational spectrum and photochemistry of phosphaketene HPCO

The vibrational spectra of the simplest phosphaketene HPCO and its isotopologue DPCO in solid Ar-matrices at 12.0 K have been analyzed with the aid of the computations at the CCSD(T)-F12a/cc-pVTZ-F12 level using configuration-selective vibrational configuration interaction (VCI). In addition to the four IR fundamentals, four overtone and ten combination bands have been unambiguously identified. Furthermore, the photochemistry of HPCO in the matrix has been investigated for the first time. Upon UV-light irradiation (365 or 266 nm), CO-elimination occurs by forming the parent phosphinidene HP that can be trapped by ˙NO to yield the elusive phosphinimine-N-oxyl radical HPNO˙. In contrast, an excimer laser (193 nm) irradiation of HPCO causes additional decomposition to H˙ and ˙PCO with concomitant formation of the long-sought phosphaethyne HOCP.

A Thermally Stable Magnesium Phosphaethynolate Grignard Complex

The 2-phosphaethynolate (OCP) anion has found versatile applications across the periodic table but remains underexplored in group 2 chemistry due to challenges in isolating thermally stable complexes. By rationally modifying their coordination environments using 1,3-dialkyl-substituted N-heterocyclic carbenes (NHCs), we have now isolated and characterized thermally stable, structurally diverse, and hydrocarbon soluble magnesium phosphaethynolate complexes (2, 4^Me, and 8-10), including the novel phosphaethynolate Grignard reagent (2^iPr). The methylmagnesium phosphaethynolate and magnesium diphosphaethynolate complexes readily activate dioxane with subsequent H-atom abstraction to form [(NHC)MgX(μ-OEt)]₂ [X = Me (3) or OCP (8 and 9)] complexes. Their reactivities increased with the Lewis acidity of the Mg²⁺ cation and may be attenuated by Lewis base saturation or a slight increase in carbene sterics. Solvent effects were also investigated and led to the surreptitious isolation of an ether-free sodium phosphaethynolate (NHC)₃Na(OCP) (6), which is soluble in aromatic hydrocarbons and can be independently prepared by the reaction of NHC and [Na(dioxane)₂][OCP] in toluene. Under forcing conditions (105 °C, 3 days), the magnesium diphosphaethynolate complex (NHC)₃Mg(OCP)₂ (10) decomposes to a mixture of organophosphorus complexes, among which a thermal decarbonylation product [(NHC)₂P^I][OCP] (11) was isolated.

Electronic Structure and Donor Ability of an Unsaturated Triphosphorus-Bridged Dimolybdenum Complex

The triphosphorus complex [Mo₂Cp₂(μ-η³:η³-P₃)(μ-P^tBu₂)] was prepared in 83% yield by reacting the methyl complex [Mo₂Cp₂(μ-κ¹:η²-CH₃)(μ-P^tBu₂)(μ-CO)] with P₄ at 333 K, a process also giving small amounts of the methyldiphosphenyl complex [Mo₂Cp₂(μ-η²:η²-P₂Me)(μ-P^tBu₂)(CO)₂]. The latter could be better prepared by first reacting the anionic complex Na[Mo₂Cp₂(μ-P^tBu₂)(μ-CO)₂] with P₄ to give the diphosphorus derivative Na[Mo₂Cp₂(μ-η²:η²-P₂)(μ-P^tBu₂)(CO)₂] and further reaction of the latter with MeI. Density functional theory calculations on the title complex revealed that its triphosphorus group can be viewed as an allylic-like P₃^- ligand acting as a six-electron donor via the external P atoms, while coordination of the internal P atom involves donation from the π orbital of the ligand and back-donation to its π* orbital, both interactions having a weakening effect on the Mo-Mo and P-P connections. The reactivity of the title compound is dominated by the electron-donor ability associated with the lone pairs located at the P atoms. Its reaction with CF₃SO₃Me gave [Mo₂Cp₂(μ-η³:η³-P₃Me)(μ-P^tBu₂)](CF₃SO₃) as a result of methylation at an external atom of the P₃ ligand, while its reaction with [Fe₂(CO)₉] enabled the addition of one, two, or three Fe(CO)₄ fragments at these P atoms, but only the diiron derivative [Mo₂Fe₂Cp₂(μ-η³:η³:κ¹:κ¹-P₃)(μ-P^tBu₂)(CO)₈] could be isolated. This complex bears a Fe(CO)₄ fragment at each of the external atoms of the P₃ ligand, and the central P atom of the latter displays the lowest ³¹P chemical shift reported to date (δ_P -721.8 ppm). The related complexes [Mo₂M₂Cp₂(μ-η³:η³:κ¹:κ¹-P₃)(μ-P^tBu₂)(CO)₁₀] (M = Mo, W) were prepared by reacting the title compound with the corresponding [M(CO)₅(THF)] complexes in toluene, while reaction with [Mo(CO)₄(THF)₂] also enabled the formation of the heptanuclear derivative [Mo₇Cp₄(μ-η³:η³:κ¹:κ¹-P₃)₂(μ-P^tBu₂)₂(CO)₁₄]. The interatomic distances in the above compounds indicate that the central Mo₂P₃ skeleton of these molecules is little modified by the attachment of 16-electron M(CO)_n fragments at the external atoms of the P₃ ligand.

Photoelectron Spectroscopy and Theoretical Study on Monosolvated Cyanate Analogue Clusters ECX-·Sol (ECX- = NCSe-, AsCSe-, and AsCS-; Sol = H2O, CH3CN)

Six monosolvated cyanate analogue clusters ECX^-·Sol (ECX^- = NCSe^-, AsCSe^-, and AsCS^-; Sol = H₂O and CH₃CN) were investigated using negative ion photoelectron spectroscopy (NIPES). NIPES experiments show that these clusters possess similar spectra overall compared to their respective isolated ECX^- anions but shift to higher electron binding energy with CH₃CN solvent, stabilizing the excess electrons slightly more than H₂O. For the ECX^-·H₂O series, vertical detachment energies and their increments relative to the bare species are measured to be 3.700/0.370, 3.085/0.415, and 3.085/0.430 eV for NCSe^-, AsCSe^- and AsCS^-, respectively, while the corresponding values in the ECX^-·CH₃CN series are 3.835/0.505, 3.145/0.475, and 3.135/0.480 eV. Ab initio electronic structure calculations indicate that the excess charges were located at the terminal N and Se atoms in NCSe^- and migrated to the central C atom in AsCSe^- and AsCS^-. For NCSe^-, the solvation is driven by the interactions with the two negatively charged terminal ends, while for AsCSe^- and AsCS^-, the solvation revolves around the interactions with the central C atom, where all the excess negative charge is concentrated. Two nearly degenerate isomers for NCSe^-·H₂O are identified, one forming a single strong N···H-O hydrogen bond (HB) and the other featuring a bidentate HB with two hydroxyl H atoms pointing to N and Se ends. In contrast, the negative central C atom in AsCSe^-/AsCS^- allows the formation of a bifurcated HB with H₂O. Similar effects are observed for the acetonitrile case, in which the three H atoms of the methyl group interact with the two negatively charged terminal ends in NCSe^-, while preferring to bind to the central negative carbon atom in AsCSe^-/AsCS^-. The different binding motifs derived in this work may suggest different solvation properties in NCSe^- versus AsCSe^-/AsCS^- with the former anion leading to asymmetric solvation at the N end of the solute, while the latter species creates more "isotropic" solvation around the central C equatorial plane.

η3 -Coordination and Functionalization of the 2-Phosphaethynthiolate Anion at Lanthanum(III)*

We present the η3 -coordination of the 2-phosphaethynthiolate anion in the complex (PN)2 La(SCP) (2) [PN=N-(2-(diisopropylphosphanyl)-4-methylphenyl)-2,4,6-trimethylanilide)]. Structural comparison with dinuclear thiocyanate-bridged (PN)2 La(μ-1,3-SCN)2 La(PN)2 (3) and azide-bridged (PN)2 La(μ-1,3-N3 )2 La(PN)2 (4) complexes indicates that the [SCP]- coordination mode is mainly governed by electronic, rather than steric factors. Quantum mechanical investigations reveal large contributions of the antibonding π*-orbital of the [SCP]- ligand to the LUMO of complex 2, rendering it the ideal precursor for the first functionalization of the [SCP]- anion. Complex 2 was therefore reacted with CAACs which induced a selective rearrangement of the [SCP]- ligand to form the first CAAC stabilized group 15-group 16 fulminate-type complexes (PN)2 La{SPC(R CAAC)} (5 a,b, R=Ad, Me). A detailed reaction mechanism for the SCP-to-SPC isomerization is proposed based on DFT calculations.

Indirect Access to Carbene Adducts of Bismuth- and Antimony-Substituted Phosphaketene and Their Unusual Thermal Transformation to Dipnictines and [(NHC)2OCP][OCP]

The synthesis and thermal redox chemistry of the first antimony (Sb)– and bismuth (Bi)–phosphaketene adducts are described. When diphenylpnictogen chloride [Ph₂PnCl (Pn = Sb or Bi)] is reacted with sodium 2-phosphaethynolate [Na[OCP]·(dioxane)_x], tetraphenyldipnictogen (Ph₂Pn–PnPh₂) compounds are produced, and an insoluble precipitate forms from solution. In contrast, when the N-heterocyclic carbene adduct (NHC)–PnPh₂Cl is combined with [Na[OCP]·(dioxane)_x], Sb– and Bi–phosphaketene complexes are isolated. Thus, NHC serves as an essential mediator for the reaction. Immediately after the formation of an intermediary pnictogen–phosphaketene NHC adduct [NHC–PnPh₂(PCO)], the NHC ligand transfers from the Pn center to the phosphaketene carbon atom, forming NHC–C(O)P-PnPh₂ [Pn = Sb (3) or Bi (4)]. In the solid state, 3 and 4 are dimeric with short intermolecular Pn–Pn interactions. When compounds 3 and 4 are heated in THF at 90 and 70 °C, respectively, the pnictogen center Pn^III is thermally reduced to Pn^II to form tetraphenyldipnictines (Ph₂Pn–PnPh₂) and an unusual bis-carbene-supported OCP salt, [(NHC)₂OCP][OCP] (5). The formation of compound 5 and Ph₂Pn–PnPh₂ from 3 or 4 is unique in comparison to the known thermal reactivity for group 14 carbene–phosphaketene complexes, further highlighting the diverse reactivity of [OCP]⁻ with main-group elements. All new compounds have been fully characterized by single-crystal X-ray diffraction, multinuclear NMR spectroscopy (¹H, ¹³C, and ³¹P), infrared spectroscopy, and elemental analysis (1, 2, and 5). The electronic structure of 5 and the mechanism of formation were investigated using density functional theory (DFT).

An N-heterocyclic carbene (NHC) was used to support the otherwise unstable Ph₂Sb—P=C=O and Ph₂Bi—P=C=O moieties. Exploration of the thermal chemistry of these NHC−phosphaketene adducts reveals the formation of the salt [NHC₂OCP][OCP]. This present work demonstrates the thermal chemistry of the 2-phospaethynolate anion with heavier pnictogens (Sb and Bi).

The "Hidden" Reductive [2+2+1]-Cycloaddition Chemistry of 2-Phosphaethynolate Revealed by Reduction of a Th-OCP Linkage

The reduction chemistry of the newly emerging 2‐phosphaethynolate (OCP)⁻ is not well explored, and many unanswered questions remain about this ligand in this context. We report that reduction of [Th(Tren^TIPS)(OCP)] (2, Tren^TIPS=[N(CH₂CH₂NSiPrⁱ₃)]³⁻), with RbC₈ via [2+2+1] cycloaddition, produces an unprecedented hexathorium complex [{Th(Tren^TIPS)}₆(μ‐OC₂P₃)₂(μ‐OC₂P₃H)₂Rb₄] (5) featuring four five‐membered [C₂P₃] phosphorus heterocycles, which can be converted to a rare oxo complex [{Th(Tren^TIPS)(μ‐ORb)}₂] (6) and the known cyclometallated complex [Th{N(CH₂CH₂NSiPrⁱ₃)₂(CH₂CH₂SiPrⁱ₂CHMeCH₂)}] (4) by thermolysis; thereby, providing an unprecedented example of reductive cycloaddition reactivity in the chemistry of 2‐phosphaethynolate. This has permitted us to isolate intermediates that might normally remain unseen. We have debunked an erroneous assumption of a concerted fragmentation process for (OCP)⁻, rather than cycloaddition products that then decompose with [Th(Tren^TIPS)O]⁻ essentially acting as a protecting then leaving group. In contrast, when KC₈ or CsC₈ were used the phosphinidiide C−H bond activation product [{Th(Tren^TIPS)}Th{N(CH₂CH₂NSiPrⁱ₃)₂[CH₂CH₂SiPrⁱ₂CH(Me)CH₂C(O)μ‐P]}] (3) and the oxo complex [{Th(Tren^TIPS)(μ‐OCs)}₂] (7) were isolated.

Designing stable closo-B12 dianions in silico for Li- and Mg-ion battery applications

The electronic structures and key factors controlling the stability of [B12(ECX)12]2− were revealed. Their good stability and weak binding property towards Li+ and Mg2+ suggest their potential application in Li- and Mg-ion batteries.

Velocity-Map Imaging and Magnetic-Bottle Photoelectron Spectroscopy of [SeCCH]-: Electronic Properties and Spin-Orbit Splitting

The recently synthesized acetylide compound KSeCCH containing the main group element selenium within the novel and in crystalline form unprecedented [SeCCH]^- anion was successfully investigated in the gas phase by high-resolution velocity-map imaging (VMI) and magnetic-bottle (MB) photoelectron spectroscopy coupled with an electrospray ionization source. Both VMI and MB spectra exhibited identical electron affinities (EA, 2.517 ± 0.002 eV), spin-orbit coupling (SOC) splittings (1492 ± 20 cm^-1), and Se-C stretching frequencies (573 ± 20 cm^-1) of the corresponding neutral tetra-atomic radical [SeCCH]^• with the VMI spectrum possessing six times higher spectral resolution compared with the MB spectrum. These experimental values were well reproduced by calculations at the CCSD(T) level, in which both the isolated [SeCCH]^- anion and the [SeCCH]^• radical adopted linear geometries. The simulated spectra based on the calculated Franck-Condon factors, the SOC splitting, and the experimental line width matched well with the measured spectra. Furthermore, comparisons of the EA and SOC splitting values with the previously reported isolobal species [SeCN]^• are also made and discussed. The decrease in the EA and SOC splitting of [SeCCH]^• is ascribed to the differences in the electronegativities between C and N atoms as well as the electron density on the Se atom in its singly occupied molecular orbital (SOMO).

Finding a soft spot for vanadium: a P-bound OCP ligand

Transmetallation studies with the phosphaethynolate ion, [OCP]^-, have largely resulted in coordination according to classical Lewis acid-base theory. That is, for harder early transition metal ions, O-bound coordination has been observed, whereas in the case of softer late transition metal ions, P-bound coordination predominates. Herein, we report the use of a V(iii) complex, namely [(nacnac)VCl(OAr)] (1) (nacnac^- = [ArNC(CH₃)]₂CH; Ar = 2,6-ⁱPr₂C₆H₃), to transmetallate [OCP]^- and bind via the P-atom as [(nacnac)V(OAr)(PCO)] (2), the first example of a 3d early transition metal that binds [OCP]^-via the P-atom. Full characterization studies of this molecule including HFEPR spectroscopy, SQuID measurements, and theoretical studies are presented.

Heavier pnictogens - treasures for optical electronic and reactivity tuning

We highlight recent advances in organopnictogen chemistry contrasting the properties of lighter and heavier pnictogens. Exploring new bonding situations, discovering unprecedented reactivities and producing fascinating opto-electronic materials are some of the most prominent directions of current organopnicogen research. Expanding the chemical toolbox towards the heavier group 15 elements will continue to create new opportunities to tailor molecular properties for small molecule activation/reactivity and materials applications alike. This frontier article illustrates the elemental substitution approach in selected literature examples.

Cyaarside (CAs- ) and 1,3-Diarsaallendiide (AsCAs2- ) Ligands Coordinated to Uranium and Generated via Activation of the Arsaethynolate Ligand (OCAs- )

Reaction of the trivalent uranium complex [((^Ad,Me ArO)₃ N)U(DME)] with one molar equiv [Na(OCAs)(dioxane)₃ ], in the presence of 2.2.2-crypt, yields [Na(2.2.2-crypt)][{((^Ad,Me ArO)₃ N)U^IV (THF)}(μ-O){((^Ad,Me ArO)₃ N)U^IV (CAs)}] (1), the first example of a coordinated η¹ -cyaarside ligand (CAs^- ). Formation of the terminal CAs^- is promoted by the highly reducing, oxophilic U^III precursor [((^Ad,Me ArO)₃ N)U(DME)] and proceeds through reductive C-O bond cleavage of the bound arsaethynolate anion, OCAs^- . If two equiv of OCAs^- react with the U^III precursor, the binuclear, μ-oxo-bridged U₂ ^IV/IV complex [Na(2.2.2-crypt)]₂ [{((^Ad,Me ArO)₃ N)U^IV }₂ (μ-O)(μ-AsCAs)] (2), comprising the hitherto unknown μ:η¹ ,η¹ -coordinated (AsCAs)^2- ligand, is isolated. The mechanistic pathway to 2 involves the decarbonylation of a dimeric intermediate formed in the reaction of 1 with OCAs^- . An alternative pathway to complex 2 is by conversion of 1 via addition of one further equiv of OCAs^- .

MELEXIR: maximum entropy Legendre expanded image reconstruction. A fast and efficient method for the analysis of velocity map imaging or photoelectron imaging data

The MELEXIR program obtains a Legendre expansion of the 3D velocity distribution from 2D images of ions or photoelectrons. The maximum entropy algorithm avoids inverse Abel transforms, is fast and applicable to low-intensity images.

The Chemistry of the 2-Phosphaethynolate Anion

In all likelihood the first synthesis of the phosphaethynolate anion, PCO^- , was performed in 1894 when NaPH₂ was reacted with CO in an attempt to make Na(CP) accompanied by elimination of water. This reaction was repeated 117 years later when it was discovered that Na(OCP) and H₂ are the products of this remarkable transformation. Li(OCP) was synthesized and fully characterized in 1992 but this salt proved to be too unstable to allow for a detailed investigation of its chemistry. It was not until the heavier analogues of this lithium salt were isolated, Na(OCP) and K(OCP) (both of which are remarkably stable and can be even dissolved in water), that the chemistry of this new functional group could be explored. Here we review the chemistry of the 2-phosphaethynolate anion, a heavier phosphorus-containing analogue of the cyanate anion, and describe the wide breadth of chemical transformations for which it has been thus far employed. Its use as a ligand, in decarbonylative and deoxygenative processes, and as a building block for novel heterocycles is described. In the mere twenty-six years since Becker first reported the isolation of this remarkable anion, it has become a fascinating reagent for the synthesis of a vast library of, often unprecedented, molecules and compounds.

New Insights into the Configurations of Lead(II)-Benzohydroxamic Acid Coordination Compounds in Aqueous Solution: A Combined Experimental and Computational Study

Novel collector lead(II)-benzohydroxamic acid (Pb(II)–BHA) complexes in aqueous solution were characterized by using experimental approaches, including Ultraviolet-visible (UV-Vis) spectroscopy and electrospray ionization-mass spectrometry (ESI-MS), as well as first-principle density functional theory (DFT) calculations with consideration for solvation effects. The Job plot delineated that a single coordinated Pb(BHA)+ should be formed first, and that the higher coordination number complexes can be formed subsequently. Moreover, the Pb(II)–BHA species can aggregate with each other to form complicated structures, such as Pb(BHA)2 or highly complicated complexes. ESI-MS results validated the existence of Pb-(BHA)n=1,2 under different solution pH values. Further, the first-principles calculations suggested that Pb(BHA)+ should be the most stable structure, and the Pb atom in Pb(BHA)+ will act as an active site to attack nucleophiles. These findings are meaningful to further illustrate the adsorption mechanism of Pb(II)–BHA complexes, and are helpful for developing new reagents in mineral processing.

Reactivity studies of an imine-functionalised phosphaalkene; unusual electrostatic and supramolecular stabilisation of a σ2λ3-phosphorus motif via hydrogen bonding

Protonation with strong acids at an imine over addition to a phosphaalkene; resulting adducts display hydrogen bonding.

Terminal tungsten pnictide complex formation through pnictaethynolate decarbonylation

Treatment of a four-coordinate tungsten(iv) complex with pnictaethynolate ions installs terminal tungsten–nitrogen, –phosphorus, and –arsenic triple bondsviadecarbonylation.