Dianionic Complexes Research Articles

Tantalum in hydrothermal fluids

Understanding the behaviour of tantalum (Ta) in hydrothermal systems is pivotal for understanding its geochemical enrichment processes and economic extraction via hydrometallurgy. Yet, its behaviour in hydrothermal systems remains poorly characterised. This study investigates the coordination chemistry, speciation, and solubility of pentavalent Ta(V) in fluoride (F) − and chloride (Cl) −rich hydrothermal solutions up to 413 °C and 800 bar, utilising in-situ High Energy Resolution Fluorescence Detected X-ray Absorption Spectroscopy (HERFD-XAS). The results reveal the stability of high order fluoridotantalate complexes in fluoride-rich fluids solutions up to the highest investigated temperature, highlighting fluoride’s paramount role in enhancing Ta solubility through the formation of stable fluoridotantalate complexes in aqueous solutions. A transition from nonafluoridotantalate tetraanion (TaF94−) to heptafluoridotantalate dianion (TaF72−) complexes was observed as a function of temperature in solutions containing ≥1 m fluoride. Conversely, our findings indicate a negligible role for chloride in Ta complexation even in high Cl (∼6 m) aqueous solutions, suggesting that Ta chloride complexes do not contribute significantly to Ta transport in hydrothermal systems. Existing solubility data were reinterpreted based on an updated speciation model that integrates the in-situ XAS results. This confirms that Ta(OH)5(aq) predominates in solutions containing <0.02 m fluoride; oxyfluoridotantalate anions such as [TaF3(OH)3−] dominate in solutions containing intermediate fluoride concentrations (0.02–1 m), and the fluoridotantalate anions [TaF94− to TaF72−] occur in more concentrated fluoride solutions (>1 m) at hydrothermal conditions (∼100–400 °C). Derived thermodynamic data for these species enable better understanding and geochemical modelling of Ta transport in hydrothermal fluids, highlighting the potential of F-rich fluids to transport significant amounts of Ta.

Assessing the Character of the C6F5 Ligand from the Electrochemical and Photophysical Properties of [Ni(C6F5)2(N∧N)] Complexes.

Organonickel complexes containing α-diimine ligands [Ni(C6F5)2(N∧N)] (N∧N = 2,2'-bipyridine (bpy), 2,9-dimethyl-1,10-phenanthroline (dmphen), 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen), dipyrido[3,2-a:2',3'-c]phenazine (dppz), 1,4-bis(isopropyl)-1,4-diazabutadiene (iPr-DAB), and 1,4-bis(2,6-dimethylphenyl)-1,4-diazabutadiene (Xyl-DAB) were prepared and studied structurally, spectroscopically, and electrochemically. Their molecular structures from single-crystal X-ray diffraction show near-perfect square planar Ni(II) coordination except in the case of dmphen. Primary reversible electrochemical reductions in the range from -1 to -2 V vs ferrocene/ferrocenium couple lead to mainly diimine-localized radical anion complexes, while secondary reductions in the range from -2 to -2.5 V lead to dianion complexes, as shown through spectroelectrochemistry. Irreversible metal-centered oxidations at around 0.7 V result in rapid aryl-aryl reductive elimination and formation of decafluorobiphenyl. No photoluminescence was detected for the complexes containing chromophoric α-diimine ligands at room temperature. At 77 K in frozen glassy 2-Me-THF matrices, weak photoluminescence was detected for the dmphen and tmphen derivatives, with broad emission bands peaking around 570 nm. All results are rationalized with the support of (TD-)DFT calculations, highlighting the role of the C6F5 ligand in different systems.

Crystal structure of a water oxidation catalyst solvate with composition (NH4)2[FeIV(L-6H)]·3CH3COOH (L = clathrochelate ligand).

The synthetic availability of mol-ecular water oxidation catalysts containing high-valent ions of 3d metals in the active site is a prerequisite to enabling photo- and electrochemical water splitting on a large scale. Herein, the synthesis and crystal structure of di-ammonium {μ-1,3,4,7,8,10,12,13,16,17,19,22-dodeca-aza-tetra-cyclo-[8.8.4.13,17.18,12]tetra-cosane-5,6,14,15,20,21-hexa-onato}ferrate(IV) acetic acid tris-olvate, (NH4)2[FeIV(C12H12N12O6)]·3CH3COOH or (NH4)2[FeIV(L-6H)]·3CH3COOH is reported. The FeIV ion is encapsulated by the macropolycyclic ligand, which can be described as a dodeca-aza-quadricyclic cage with two capping tri-aza-cyclo-hexane fragments making three five- and six six-membered alternating chelate rings with the central FeIV ion. The local coord-ination environment of FeIV is formed by six deprotonated hydrazide nitro-gen atoms, which stabilize the unusual oxidation state. The FeIV ion lies on a twofold rotation axis (multiplicity 4, Wyckoff letter e) of the space group C2/c. Its coordination geometry is inter-mediate between a trigonal prism (distortion angle φ = 0°) and an anti-prism (φ = 60°) with φ = 31.1°. The Fe-N bond lengths lie in the range 1.9376 (13)-1.9617 (13) Å, as expected for tetra-valent iron. Structure analysis revealed that three acetic acid mol-ecules additionally co-crystallize per one iron(IV) complex, and one of them is positionally disordered over four positions. In the crystal structure, the ammonium cations, complex dianions and acetic acid mol-ecules are inter-connected by an intricate system of hydrogen bonds, mainly via the oxamide oxygen atoms acting as acceptors.

Reductive Metallation of Dendralenes and Myrcene Using Dimagnesium(I) Compounds: A Facile Route to Unsaturated Organomagnesium Compounds.

The two-electron reduction of 2,3-dimethylbuta-1,3-diene (DMB) with β-diketiminate and guanidinate substituted dimagnesium(I) compounds has given complexes in which two bidentate amido-magnesium fragments are bridged through the π-system of the DMB dianion, viz. [(LMg)2 (μ-DMB)] (L=Xyl Nacnac, [HC(MeCNXyl)2 ]- , Xyl=2,6-xylyl; or Priso=[(DipN)2 CNPri 2 ]- , Dip=2,6-diisopropylphenyl). Similar double reductions of [4]dendralene (4dend) have afforded the complexes, [(LMg)2 (μ-4dend)] (L=Ar Nacnac, Ar=Xyl or mesityl (Mes); or Priso) in which the 4dend dianion is π-coordinated to the bidentate amido-magnesium fragments. Treatment of several such complexes with THF leads to Z- to E-isomerization of the dendralene fragment, and formation of purely σ-bonded Mg-C interactions in the THF coordinated products [{(Ar Nacnac)(THF)Mg}2 (μ-4dend)] (Ar=Xyl, Mes or Dip). Reaction of myrcene (Myr) with [{(Xyl Nacnac)Mg}2 ] proceeds via reductive coupling of Myr to give a previously unknown acyclic, branched C20 tetra-olefin dianion complex [{(Xyl Nacnac)(THF)Mg}2 (μ-Myr)2 ]. Preliminary reactions of [(LMg)2 (μ-DMB)] with H2 and/or CO yielded a series of products, including novel magnesium hydride compounds, products derived from couplings of CO with the reduced DMB fragment (viz. magnesium dimethylcyclohexadienediolates), and one magnesium cyclopropanetriolate complex from the magnesium(I) induced coupling of DMB with H2 and CO.

Geometric control of Cu, Ni and Pd complexes in the solid state via intramolecular H-bonding interactions

In this article, we describe the synthesis and characterization of a family of copper, nickel and palladium complexes bound by bidentate ligands derived from ortho-phenylenediamine that contain tunable H-bond donors. The crystal structures of the reduced dianionic metal complexes (formulated as [MII(L2-)2]2-) depict intramolecular H-bonding interaction between the two ligand scaffolds. Variations on the primary (Cu, Ni, Pd), secondary (H-bonding donor) and tertiary coordination sphere (solvent of crystallization and countercation), led to the isolation of the metal complexes in square-planar (SP) and/or twisted pseudo-tetrahedral geometry (TW). A detailed structural analysis of the complexes in the solid state revealed that the intramolecular H-bonding interactions can be altered by disrupting the bonds between the countercation, solvent of crystallization and the ligand scaffold, which leads to changes in the geometry of the complexes (SP or TW). DFT calculations are in agreement with our experimental observations, in which the Cu complexes were found to favor twisted geometries while the Ni and Pd complexes favored square-planar geometries.

Beyond Duality: Rationalizing Repulsive Coulomb Barriers in Host-Guest Cyclodextrin-Dodecaborate Complexes.

The repulsive Coulomb barrier (RCB), an intrinsic potential energy barrier along electron detachment or charge-separation coordinates in multiply charged anions (MCAs), provides dynamic stability to MCAs whose electronic and thermodynamic stabilities are largely dictated by strong internal Coulomb repulsions. Spectroscopic and theoretical characterizations of the RCB have been focused on isolated MCAs. In this work, we extend the RCB investigation beyond the previous scope by including noncovalent host-guest cyclodextrin-closo-dodecaborate dianionic complexes χCD·B12X122- (χ = α, β, γ; X = H, F-I). Photodechment photoelectron spectroscopy reveals the existence of two distinctly different RCBs, derived from detaching electrons from the guest dianions (RCB1) or ionizing the host neutrals (RCB2), respectively, with the latter being substantially smaller than the former. Theoretical calculations support the duality of RCBs in these complexes and further exhibit highly anisotropic nature of the RCBs.

Platinum(II) complexes containing pyridyl-substituted thiourea dianion and monoanion ligands: Synthesis, structural chemistry, and theoretical investigations

Reactions of cis-[PtCl2(PPh3)2] with the 2-pyridyl-substituted thioureas py(CH2)nNHC(S)NHC6H4R (R = H, OMe or NO2; n = 0, 1 or 2) in methanol with Et3N base, followed by precipitation with water gave good yields of the complexes [Pt{SC(NC6H4R)(N(CH2)npy)}(PPh3)2]. The compounds were characterised 1H NMR, 31P{1H} NMR, FTIR and single crystal X-ray crystallography. The initial NMR investigation indicated the possibility of isomerism in the complexes. 31P{1H} NMR investigations revealed the presence of an initial distal isomer for the dianion complexes, which underwent solution phase isomerization into the proximal isomeric forms of the complexes and/or a mixture of the proximal and distal isomers. The opposite trend was recorded for the monoanionic complex with the formation of an initial proximal isomer and subsequent isomerisation into 1:3 mixture of the distal and proximal isomeric forms of the complex. The degree of isomerization was observed to be related to the difference in energy between the two isomeric forms of the complex and the nature and size of the R substituents in the complex. The molecular geometries of a number of the compounds showed a distorted square-planar geometry defined by a NP2S donor set. The thiourea ligand acts as (N,S)-chelating dianionic ligand so that each donor atom is opposite a phosphane-P atom; a trans-influence is evident on the Pt-P bonds. In each complex, the pyridyl-substituted nitrogen is coordinated to platinum. The cationic complex [Pt{SC(NPh)(NHCH2py)}(PPh3)2]+ was also isolated as its BF4- salt by addition of excess NaBF4 to the reaction mixture. In this complex, the thiourea monoanion coordinates in a distal manner, with the NHCH2py group remote from the platinum centre. Charge-assisted ammonium-NH…N(pyridyl) bonding leads to dimeric aggregates. These, along with the neutral molecules [Pt{SC(Np-C6H4R2)(N(CH2)npy)}(PPh3)2] are assembled into the three-dimensional crystal via weak non-covalent interactions. Characterisation by 31P{1H} NMR spectroscopy showed the presence of several isomeric species in solution.

Ether/Thioether-Functionalized Dianionic α-Iminopyridine Rare-Earth Metal Amido Complexes and Their Catalytic Activity toward Hydrophosphination of Alkenes

The double deprotonation of 2-aminomethyl pyridine by rare-earth metal triamido complexes was found to be an alternative strategy to anchor dianionic iminopyridine on rare-earth metal centers with the morpholinyl group previously. To verify the generality of the protocol with different appendant donor groups, reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with ether/thiotether-substituted 2-aminomethyl pyridine 2-(CH3DCH2CH2NHCH2)-6-R-C5H3N (D = O, R = H (1), Ph (2); D = S, R = H (3)) were performed, leading to the formation of ether/thioether-functionalized dianionic α-iminopyridine rare-earth metal amido complexes {μ-η2:σ1:κ1:κ1-2-[CH3ECH2CH2NCH]-6-R-C5H3N}2RE2[N(SiMe3)2]2 (D = O, R = H, RE = Dy (4a), Y (4b), Er (4c), Yb (4d), Lu (4e), R = Ph, RE = Dy (5a), Y (5b), Er (5c), Lu (5d); D = S, R = H, RE = Y (6a), Er (6b), Lu (6c)). These results supported the ability of oxygen or sulfur coordination in promoting the double deprotonation of 2-aminomethyl pyridine to construct new iminopyridine rare-earth metal complexes in the dianionic form. Further examination of these rare-earth metal amido complexes displayed good catalytic activity for hydrophosphination of alkenes, affording anti-Markovnikov addition products under solvent-free conditions.

K([2.2.2]‐crypt)]K[Pt3(μ2‐CO)3(PPh3)3] ⋅ 3NH3 – A New Chini‐Type Platinum Carbonyl Complex

AbstractThe titular compound [K([2.2.2]‐crypt)]K[Pt3(μ2‐CO)3(PPh3)3] ⋅ 3NH3 (1) ([2.2.2]‐crypt=4,7,13,16,21,24‐Hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane) contains a triangular platinum complex, the approximate D3 symmetry of which is only broken by the phenyl substituents of the PPh3 ligands.. The dianionic complex represents only the second triangular carbonyl platinate characterized via single crystal X‐ray diffraction in monomeric form. The compound crystallizes in the space group P with the unit cell parameters a=13.8826 Å, b=14.2899 Å and c=21.3254 Å. For the formation of the platinate, liquid ammonia seems to play a crucial role as a solvent for the polygermanide used for the reduction as well as for the stabilization of the dianion.

Synthesis, characterization, and x-ray crystallography of unexpected chloro-substitution on 1-(4-chlorophenyl)-3-phenylthiourea platinum(II) complex with tertiary phosphine ligand

The reaction of 1-(4-chlorophenyl)-3-phenylthiourea (CPTH2) with [PtCl2(PPh3)2] moiety in a 1:1 molar ratio in a basic solution afforded unexpected Pt(II) thiourea dianion complex. The crystal structure revealed that the second phenyl ring of the parent ligand was substituted with a chlorine atom. Chlorine substitution on the phenyl ring might have been aided by the solvent CH2Cl2. The crystal structure revealed a platinum(II)-centered four-membered ring structure. FT-IR, 1H-NMR, and 31P-NMR spectroscopy were also utilized to study the complex. The crystal packing environment is explored by Hirshfeld surface analysis, enrichment ratio calculations and void analysis. Various quantum calculations were performed on both the ligand and its complex, and the calculated values were compared to the experimental ones. The energies of the two resonance structures of the CPTH2 ligand are very close. However, the stability of the thione form was slightly greater than that of the thiol form. The bond lengths and bond angles calculated by Orca for the Pt(II) complex were nearly identical to the experimental values. The biological assessment of the Pt(II) complex was evaluated against four pathogenic bacteria: Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, and Salmonella typhi (S. typhi). The Pt(II) complex exhibited moderate inhibition values against all bacterial species, with the exception of Pseudomonas aeruginosa (P. aeruginosa), which exhibited the greatest activity.

Tb4(OH)4]-Cuboid Complex Dianion Stabilized with Six Carboxylate Bridges and Four Diketonate Caps

A cubane-like complex dianion [Tb4(OH)4(tfa)6(hfac)4]2− was synthesized, accompanied by two counter cations of [Ni(hfac)(2pyIN)2]+, where Htfa, Hhfac, and 2pyIN stand for trifluoroacetic acid, 1,1,1,5,5,5-hexafluoropentane-2,4-dione, and 4,4,5,5-tetramethyl-2-pyridylimidazolin-1-oxyl, respectively. In the complex anion, each Tb ion was capped with hfac, and each Tb···Tb diagonal was bridged with tfa, thus forming an approximate Td symmetry, though the whole molecular formula was crystallographically independent in an orthorhombic Pbca space group. The ionic charge was −2 in total. The magnetic study revealed that the complex ions were magnetically isolated from each other. Practically no 4f–4f superexchange interaction was operative, while the 2p–3d ferromagnetic coupling seemed to be appreciable, as anticipated from the proposed magnetostructural relationship.

Encapsulation of halocadmate anion via hydrogen bonding: synthesis and characterization of bis(diethylenetriamine)cobalt(III) complex containing hexabromocadmate anion.

In this work, the encapsulation of [CdBr6]4- by six cations, [Co(dien)2]3+ has been described with the help of single crystal X-ray structural study in the complex, mer-[Co(dien)2]2[CdBr6]Br2. The complex anion, [CdBr6]4- has been obtained through solution method while attempting to synthesize complex dianion, [CdBr4]2-. This newly synthesized complex has been initially characterized by elemental analyses and spectroscopic studies (IR, NMR and UV-Visible). IR and NMR studies have been used for the isomeric identification of [Co(dien)2]3+. Single crystal X-ray structure determination has revealed the presence of two complex cations, [Co(dien)2]3+, one complex anion, [CdBr6]4-, and two Br- anions. The complex has crystallized in monoclinic crystal system with space group, P21/n. The study of intermolecular interactions has confirmed the stability of crystal structure through N-H type H-bonding interactions besides electrostatic forces of attraction.

Estimations of Fe–N2 Intrinsic Interaction Energies of Iron–Sulfur/Nitrogen–Carbon Sites: A Deeper Bonding Insight by EDA-NOCV Analysis of a Model Complex of the Nitrogenase Cofactor

The MoFe7S9C1– unit of the nitrogenase cofactor (FeMoco) attracts chemists and biochemists due to its unusual ability to bind aerial dinitrogen (N2) at ambient condition and catalytically convert it into ammonia (NH3). The mode of N2 binding and its reaction pathways are yet not clear. An important conclusion has been made based on the very recent synthesis and isolation of model Fe(I/0)-complexes with sulfur-donor ligands under the cleavage of one Fe–S bond followed by binding of N2 at the Fe(0) center. These complexes are structurally relevant to the nitrogenase cofactor (MoFe7S9C1–). Herein, we report the EDA-NOCV analyses and NICS calculations of the dinitrogen-bonded dianionic complex Fe0–N2 (1) (having a CAr ← Fe π-bond) and monoanionic complex FeI–N2 (2) (having a CAr–Fe σ-bond) to provide a deeper insight into the Fe–N2 interacting orbitals and corresponding pairwise interaction energies (EDA-NOCV = energy decomposition analysis coupled with natural orbital for chemical valence; NICS = nucleus-independent chemical shifts). The orbital interaction in the Fe–N2 bond is significantly larger than Coulombic interactions, with major pairwise contributions coming from d(Fe) orbitals to the empty π* orbitals of N2 (three Fe → N2). ΔEint values are in the range of −61 to −77 kcal mol–1. Very interestingly, NICS calculations have been carried out for the fragments before and after binding of the N2 molecule. The computed σ- and π-aromaticity values are attributed to the position of the Fe atoms, oxidation states of Fe centers, and Fe–C bond lengths of these two complexes.

Antibacterial, spectroscopic and X-ray crystallography of newly prepared heterocyclic thiourea dianion platinum(II) complexes with tertiary phosphine ligands

Treatment of one molar equivalent of [PtCl2(diphos)] (diphos = dppe, dppp, dppb or dppf) or [PtCl2(PPh3)2] with one molar equivalent of (H2CPPT) in the presence of Et3N afforded the new heterocyclic thiourea dianion complexes [Pt(κ2-CPPT)(diphos)] and [Pt(κ2-CPPT)(PPh3)2] (1–5). The synthesized complexes were characterized by FT-IR, 1H NMR and 31P-{1H} NMR spectroscopy. Moreover, X-ray single crystal structure determination for complexes [Pt(κ2-CPPT)(dppe)] (1) and [Pt(κ2-CPPT)(dppb)] (3) showed a four membered ring structure with the Pt(II) ion being central and adopting a slightly distorted square planar geometry. Furthermore, the X-ray structures showed that the sulfur atom is trans to the phosphine ligand with the shortest Pt-P bond, compared to the nitrogen atom that is trans to the other Pt-P bond. Interestingly, the obtained complexes, apart from previously synthesized ones, showed one isomer formation only. This behavior is probably due to the inductive effect for both of the heteroatoms and the chlorine atom on the pyridyl group. Generally, the prepared complexes showed similar behavior to their analogous non-substituted thiourea dianion complexes, with no observable effect of the heteroatom on the overall structure. Furthermore, antibacterial activities were tested against three pathogenic bacterial species; among the four tested complexes, complexes 4 and 2 showed high activity values.

Novel base-free dianion complexes of Pt(II) and Pd(II) derived from heterocyclic thiourea and tertiary phosphine ligands

Treatment of one molar equivalent of [M(HCPPT)2] (M=Pd, Pt; H2CPPT = 1-(5-chloropyridin-2-yl)-3-phenylthiourea) with one molar equivalent of κ2-diphos (diphos = dppe, dppp, dppb, and dppf) or two molar equivalent of κ1-phos afforded eight heterocyclic thiourea dianion complexes (1–8). The spectroscopic data analysis showed clear AX splitting pattern, which indicates that the two coordinated phosphorus atoms are non-equivalent. Meaning that, the metal's center is attached to both S,N donor atoms in a chelating fashion. In addition, the splitting system show a good resemblance to the previously synthesized thiourea dianion complexes. Furthermore, the reaction is believed to undergo a square planar substitution mechanism at which five coordinate intermediate is formed. Generally, the reported complexes (1–8) are believed to resemble their analogues thiourea dianion complexes at which a four membered ring structure is formed with Pt(II) or Pd(II) being centered, adopting a square planar geometry. Four of the synthesized complexes (1–4) were tested against Salmonella typhimurium and Bacillus subtilis bacteria at which complexes 4 and 2 showed highest activity values.

Dianion complexes of pyrrole-based anion receptors: [2+1]-Type complexes that form ion-pairing assemblies

[2+1]-Type receptor–dianion complexes were formed in the solid state by the interaction between dipyrrolyldiketone boron complexes and sulfate, forming different binding modes as sandwiched- and interlocked-types depending on the substituents of the anion receptors. The dianionic [2+1]-type complexes provided ion-pairing assemblies in combination with countercations.

The Coordination Chemistry of Imidomethanedithiolate Di-anions: A Structural Comparison with Their Dithiocarbamate Analogs

A review of the coordination chemistry along with the structural features of heavy element complexes of dithiocarbimate di-anions in the form of [(R)C=NCS2]2− for R = CN, alkyl, and aryl are described. This class of compound is far less studied compared with the well-explored dithiocarbamate mono-anions formulated as [R(R’)NCS2]− for R/R’ = H, alkyl, and aryl. The coordination chemistry of dithiocarbimate di-anions is dominated by a S,S-chelating mode; rare examples of alternative modes of coordination are evident. When comparisons are available, the structural motifs adopted by metal dithiocarbimate complexes match those found for their dithiocarbamate analogs, with only small, non-systematic variations in the M–S bond lengths.

Ligand-Centered Triplet Diradical Supported by a Binuclear Palladium(II) Dipyrrindione.

Oligopyrroles form a versatile class of redox-active ligands and electron reservoirs. Although the stabilization of radicals within oligopyrrolic π systems is more common for macrocyclic ligands, bidentate dipyrrindiones are emerging as compact platforms for one-electron redox chemistry in transition-metal complexes. We report the synthesis of a bis(aqua) palladium(II) dipyrrindione complex and its deprotonation-driven dimerization to form a hydroxo-bridged binuclear complex in the presence of water or triethylamine. Electrochemical, spectroelectrochemical, and computational analyses of the binuclear complex indicate the accessibility of two quasi-reversible ligand-centered reduction processes. The product of a two-electron chemical reduction by cobaltocene was isolated and characterized. In the solid state, this cobaltocenium salt features a folded dianionic complex that maintains the hydroxo bridges between the divalent palladium centers. X-band and Q-band EPR spectroscopic experiments and DFT computational analysis allow assignment of the dianionic species as a diradical with spin density almost entirely located on the two dipyrrindione ligands. As established from the EPR temperature dependence, the associated exchange coupling is weak and antiferromagnetic (J ≈ −2.5 K), which results in a predominantly triplet state at the temperatures at which the measurements have been performed.

1,3‐Bis(tricyanoborane)imidazoline‐2‐ylidenate Anion—A Ditopic Dianionic N‐Heterocyclic Carbene Ligand

The 1,3‐bis(tricyanoborane)imidazolate anion 1 was obtained in high yield from lithium imidazolate and B(CN)3−pyridine adduct. Anion 1 is chemically very robust and thus allowed the isolation of the corresponding H5O2 + salt. Furthermore, monoanion 1 served as starting species for the novel dianionic N‐heterocyclic carbene (NHC), 1,3‐bis(tricyanoborane)imidazoline‐2‐ylidenate anion 3 that acts as ditopic ligand via the carbene center and the cyano groups at boron. First reactions of this new NHC 3 with methyl iodide, elemental selenium, and [Ni(CO)4] led to the methylated imidazolate ion 4, the dianionic selenium adduct 5, and the dianionic nickel tricarbonyl complex 6. These NHC derivatives provide a first insight into the electronic and steric properties of the dianionic NHC 3. Especially the combination of properties, such as double negative charge, different coordination sites, large buried volume and good σ‐donor and π‐acceptor ability, make NHC 3 a unique and promising ligand and building block.

Changes in the proportions of an active pharmaceutical through cocrystals.

In this study, the modulation of amounts sulfathiazolium cations in different 2,6-pyridinedicarboxylates is demonstrated. An uncommon monoionic sulfathiazolium zinc 2,6-pyridinedicarboxylate (1:1 electrolyte) complex was characterized. Conventional sulfathiazolium zinc-bis-2,6-pyridinedicarboxylate dianionic complexes (2:1 electrolyte) were formed when hydroxyaromatic compounds such as 1,3-dihydroxybenzene or 3-nitrophenol were used as guest components. Thus, with the aid of the hydroxyaromatic molecules the zinc-bis-2,6-pyridinedicarboxylate complexes were stabilized with the relatively large sized sulfathiazolium cations. It was a consequence of domain expansion by the phenolic compounds. Sandwiched aromatic guests between the 2,6-pyridinedicarboxylates provided appropriate packing to accommodate the two large cations in the self-assemblies, which helped to modulate the amounts of sulfathiazole in different formulations. Antibacterial activities with E. coli DH5α have shown that the salt and the complexes have lower g/ml antibacterial activity than the parent drug.