Cyanide Ligands Research Articles

Hexacyanometalate-Based Redox Couple for High-Efficiency Iron-Chromium Flow Battery

As increasing the importance of electrical grids and utilizing renewable energy sources, large-scale energy storage systems that can effectively store and supply electrical energy have attracted great research attention in recent times. Aqueous based redox flow batteries (RFBs) are promising candidates for large-scale energy storage due to their long cycle life, high safety, and high solubility of a catholyte and anolyte. Also, unlike other battery systems such as lithium-ion batteries, the energy density and power capabilities of RFBs can be decoupled, enabling flexibility for controlling capacity and power, and scalability as an industrial perspective. Iron-chromium (Fe-Cr) RFB is a good candidate for cost-effective systems comparing to all-vanadium RFB, which is well-known as the most developed RFB. However, sluggish Cr3+/2+ redox kinetics and hydrolysis of ferrous ion have become formidable obstacles to achieving high efficiency and stability. In particular, the poor kinetics of chromium ions make the hydrogen evolution reaction more dominant and cause the state of charge of the positive and negative side to being imbalanced.Herein, we have demonstrated a new RFB system based on hexacyanometalate materials ([M(CN)6]3-/4-, M = transition metal). The cyanide ligands linked through transition metal ions play a role in mitigating the hydrolysis in the aqueous environment and enhance the electrochemical kinetics. We have investigated the stability and electrochemical kinetic information of our redox couples comparing to conventional active materials. The superior kinetics of hexacyanometalate based-redox couples contributed to improving voltage efficiency. Besides, by use of a transition metal oxide type-catalyst on a carbon-felt current collector, this RFB system can achieve higher energy efficiency than that of the pristine carbon-felt electrode, suggesting that the employing catalyst can enhance the electrochemical kinetics of the active materials.

Cationic Group VI Metal Imido Alkylidene N-Heterocyclic Carbene Nitrile Complexes: Bench-Stable, Functional-Group-Tolerant Olefin Metathesis Catalysts.

Despite their excellent selectivities and activities, Mo‐and W‐based catalysts for olefin metathesis have not gained the same widespread use as Ru‐based systems, mainly due to their inherent air sensitivity. Herein, we describe the synthesis of air‐stable cationic‐at‐metal molybdenum and tungsten imido alkylidene NHC nitrile complexes. They catalyze olefin metathesis reactions of substrates containing functional groups such as (thio‐) esters, (thio‐) ethers and alcohols without the need for prior activation, for example, by a Lewis acid. The presence of a nitrile ligand was found to be essential for their stability towards air, while no decrease in activity and productivity could be observed upon coordination of a nitrile. Variations of the imido and anionic ligand revealed that alkoxide complexes with electron‐withdrawing imido ligands offer the highest reactivities and excellent stability compared to analogous triflate and halide complexes.

Temperature Dependence of Structural Dynamics at the Catalytic Cofactor of [FeFe]-hydrogenase.

[FeFe]-hydrogenases are nature's blueprint for efficient hydrogen turnover. Understanding their enzymatic mechanism may improve technological H2 fuel generation. The active-site cofactor (H-cluster) consists of a [4Fe-4S] cluster ([4Fe]H), cysteine-linked to a diiron site ([2Fe]H) carrying an azadithiolate (adt) group, terminal cyanide and carbon monoxide ligands, and a bridging carbon monoxide (μCO) in the oxidized protein (Hox). Recently, the debate on the structure of reduced H-cluster states was intensified by the assignment of new species under cryogenic conditions. We investigated temperature effects (4-280 K) in infrared (IR) and X-ray absorption spectroscopy (XAS) data of [FeFe]-hydrogenases using fit analyses and quantum-chemical calculations. IR data from our laboratory and literature sources were evaluated. At ambient temperatures, reduced H-cluster states with a bridging hydride (μH-, in Hred and Hsred) or with an additional proton at [4Fe]H (Hred') or at the distal iron of [2Fe]H (Hhyd) prevail. At cryogenic temperatures, these species are largely replaced by states that hold a μCO, lack [4Fe]H protonation, and bind an additional proton at the adt nitrogen (HredH+ and HsredH+). XAS revealed the atomic coordinate dispersion (i.e., the Debye-Waller parameter, 2σ2) of the iron-ligand bonds and Fe-Fe distances in the oxidized and reduced H-cluster. 2σ2 showed a temperature dependence typical for the so-called protein-glass transition, with small changes below ∼200 K and a pronounced increase above this "breakpoint". This behavior is attributed to the freezing-out of larger-scale anharmonic motions of amino acid side chains and water species. We propose that protonation at [4Fe]H as well as ligand rearrangement and μH- binding at [2Fe]H are impaired because of restricted molecular mobility at cryogenic temperatures so that protonation can be biased toward adt. We conclude that a H-cluster with a μCO, selective [4Fe]H or [2Fe]H protonation, and catalytic proton transfer via adt facilitates efficient H2 conversion in [FeFe]-hydrogenase.

Nitrile Oxidation at a Ruthenium Complex leading to Intermolecular Imido Group Transfer.

The oxidation of an acetonitrile ligand coordinated to ruthenium is explored in deuterated dimethylsulfoxide by 1H NMR spectroscopy. When oxidized with an iodosoarene oxygen atom transfer (OAT) reagent, kinetic studies demonstrate that the nitrile ligand does not dissociate before reacting. Instead, OAT to the central nitrile carbon is implicated (nitrile oxidation), and is further supported by the product of the reaction, N-acyl-dimethylsulfoximine. The N-acyl-dimethylsulfoximine likely formed by an imido group transfer reaction from ruthenium to the NMR solvent, and the product was synthesized independently to verify its identity in the reaction. This reaction represents the first time that a nitrile oxidation reaction has resulted in intermolecular imido group transfer to a substrate, presumably through a reactive ruthenium(IV)imido intermediate. This suggests that nitrile oxidation is a plausible route into reactive metal-imido intermediates for amination and aziridination reactions.

One-dimensional heteronuclear complexes with cyanide and 2-ethylimidazole ligands

Two tetracyanonickelate(II) complexes with 2-ethylimidazole ligand have been synthesized as single crystal form and characterized by spectroscopic (infrared and Raman) and single crystal X-ray diffraction techniques. Crystallographic investigation shows that heterometallic complexes have one-dimensional coordination polymers. Vibrational assignments are given for all the observed bands and the spectral features also supported to the crystal structures of the polynuclear complexes. The decomposition reaction takes places in the temperature range 30–700 °C in the dry air atmosphere.

Crystal structure of Leishmania mexicana cysteine protease B in complex with a high-affinity azadipeptide nitrile inhibitor

Leishmania mexicana is an obligate intracellular protozoan parasite that causes the cutaneous form of leishmaniasis affecting South America and Mexico. The cysteine protease LmCPB is essential for the virulence of the parasite and therefore, it is an appealing target for antiparasitic therapy. A library of nitrile-based cysteine protease inhibitors was screened against LmCPB to develop a treatment of cutaneous leishmaniasis. Several compounds are sufficiently high-affinity LmCPB inhibitors to serve both as starting points for drug discovery projects and as probes for target validation. A 1.4 Å X ray crystal structure, the first to be reported for LmCPB, was determined for the complex of this enzyme covalently bound to an azadipeptide nitrile ligand. Mapping the structure-activity relationships for LmCPB inhibition revealed superadditive effects for two pairs of structural transformations. Therefore, this work advances our understanding of azadipeptidyl and dipeptidyl nitrile structure-activity relationships for LmCPB structure-based inhibitor design. We also tested the same series of inhibitors on related cysteine proteases cathepsin L and Trypanosoma cruzi cruzain. The modulation of these mammalian and protozoan proteases represents a new framework for targeting papain-like cysteine proteases.

Two-Dimensional Heteronuclear Coordination Polymers Constructed by Cyanide and 3-(2-Aminoethyl)pyridine Ligands

Two new heteronuclear (Ni/Cd and Pd/Cd) 2D coordination polymers formulated as namely {[Cd(μ-3aepy)2Ni(μ-CN)2(CN)2]⋅2H2O}n (1) and [Cd(3aepy)Pd(μ4-CN)4]n (2) (3aepy = 3-(2-aminoethyl)pyridine) were obtained and determined using different techniques (FT-IR and Raman spectroscopies, single crystal X-ray diffraction, elemental, SEM–EDX and thermal analyses). Single crystal X-ray study of the complexes revealed that the Ni(II) and Pd(II) ions are coordinated with four cyanide-carbon atoms in square planar geometries. The Cd(II) ions are bridged by 3aepy ligands to generate [Cd2(3aepy)2]2+ cation and adjacent cations are further linked to cyanide ligands from [Ni(μ-CN)4]2− anion, generating corrugated rectangular grid-like 2D sheets in 1. Whereas, the Cd(II) and Pd(II) ions are bridged by cyanide ligands, generating corrugated rectangular grid-like 2D sheets in 2. The Cd1 is possessed the distorted octahedral coordination geometry with six nitrogen atoms from two 3aepy and four cyanide ligands. The Cd2 is coordinated by four nitrogen atoms from cyanide ligands to form a square-planar geometry. Furthermore, the most remarkable properties of the complexes are the existence of the intermolecular C–H⋯M interactions between M(II) and hydrogen atoms of the 3aepy ligands (M(II) = Ni and Pd).

Reactivity of Coordinated 2-Pyridyl Oximes: Synthesis, Structure, Spectroscopic Characterization and Theoretical Studies of Dichlorodi{(2-Pyridyl)Furoxan}Zinc(II) Obtained from the Reaction between Zinc(II) Nitrate and Pyridine-2-Chloroxime

This work reports our first results in the area of the reactivity of coordinated chloroximes. The 1:2:2:2 Zn(NO3)2∙6H2O/Eu(NO3)3∙6H2O/ClpaoH/Et3N reaction mixture in MeOH, where ClpaoH is pyridine-2-chloroxime, resulted in complex [ZnCl2(L)] (1); L is the di(2-pyridyl)furoxan [3,4-di(2-pyridyl)-1,2,5-oxadiazole-2-oxide] ligand. The same complex can be isolated in the absence of the lanthanoid. The direct reaction of ZnCl2 and pre-synthesized L in MeOH also provides access to 1. In the tetrahedral complex, L behaves as a Npyridyl,N′pyridyl-bidentate ligand, forming an unusual seven-membered chelating ring. The Hirshfeld Surface analysis of the crystal structure reveals a multitude of intermolecular interactions, which generate an interesting 3D architecture. The complex has been characterized by FTIR and Raman spectroscopies. The structure of 1 is not retained in DMSO (dimethylsulfoxide) solution, as proven by NMR (1H, 13C, 15N) spectroscopy and its molar conductivity value. Upon excitation at 375 nm, solid 1 emits blue light with a maximum at 452 nm; the emission is of an intraligand character. The geometric and energetic profiles of possible pathways involved in the reaction of ClpaoH and Zn(NO3)2∙6H2O in MeOH in the presence of Et3N has been investigated by DFT (Density Functional Theory) computational methodologies at the PBE0/Def2-TZVP(Cr)∪6-31G(d,p)(E)/Polarizable Continuum Model (PCM) level of theory. This study reveals an unprecedented cross-coupling reaction between two coordinated 2-pyridyl nitrile oxide ligands.

Intense Red-Blue Luminescence Based on Superfine Control of Metal-Metal Interactions for Self-Assembled Platinum(II) Complexes.

A series of assembled PtII complexes comprising N-heterocyclic carbene and cyanide ligands was constructed using different substituent groups, [Pt(CN)2 (R-impy)] (R-impyH+ =1-alkyl-3-(2-pyridyl)-1H-imidazolium, R=Me (Pt-Me), Et (Pt-Et), i Pr (Pt-i Pr), and t Bu (Pt-t Bu)). All the complexes exhibited highly efficient photoluminescence with an emission quantum yield of 0.51-0.81 in the solid state at room temperature, originating from the triplet metal-metal-to-ligand charge transfer (3 MMLCT) state. Their emission colors cover the entire visible region from red for Pt-Me to blue for Pt-t Bu. Importantly, Pt-t Bu is the first example that exhibits blue 3 MMLCT emission. The 3 MMLCT emission was proved and characterized based on the temperature dependences of the crystal structures and emission properties. The wide-range color tuning of luminescence using the 3 MMLCT emission presents a new strategy of superfine control of the emission color.

Intense Red‐Blue Luminescence Based on Superfine Control of Metal–Metal Interactions for Self‐Assembled Platinum(II) Complexes

AbstractA series of assembled PtII complexes comprising N‐heterocyclic carbene and cyanide ligands was constructed using different substituent groups, [Pt(CN)2(R‐impy)] (R‐impyH+=1‐alkyl‐3‐(2‐pyridyl)‐1H‐imidazolium, R=Me (Pt‐Me), Et (Pt‐Et), iPr (Pt‐iPr), and tBu (Pt‐tBu)). All the complexes exhibited highly efficient photoluminescence with an emission quantum yield of 0.51–0.81 in the solid state at room temperature, originating from the triplet metal‐metal‐to‐ligand charge transfer (3MMLCT) state. Their emission colors cover the entire visible region from red for Pt‐Me to blue for Pt‐tBu. Importantly, Pt‐tBu is the first example that exhibits blue 3MMLCT emission. The 3MMLCT emission was proved and characterized based on the temperature dependences of the crystal structures and emission properties. The wide‐range color tuning of luminescence using the 3MMLCT emission presents a new strategy of superfine control of the emission color.

Unique bi-directional coordinative interaction of 2D inorganic nanosheet with Prussian blue nanocrystal for optimizing its functionality

Abstract An interfacial electronic coupling, a crucial factor in optimizing the functionality of hybrid material, can be enhanced by unique bi-directional coordinative bonding of 2D metal oxide nanosheet with Prussian blue (PB) nanocrystal. A strong mutual interfacial bonding between monolayered 2D MnO2 nanosheet and PB nanocrystal can be achieved by remarkable coordination abilities of the surface-exposed oxide ions of MnO2 and the cyanide ligand of PB. Due to the enhanced interfacial electronic coupling, the PB−layered MnO2 nanohybrid shows excellent supercapacitor electrode performance with huge specific capacitance of 623 F g−1 at 5 mV s−1, i.e. the largest value among ever-reported PB-based electrodes, which is much superior to those of the pristine PB and PB−graphene homologue. In-situ micro-Raman analysis highlights the enhancement of the Faradaic redox process of PB lattice by strong interfacial coupling with MnO2 nanosheet. The present study underscores that the introduction of bi-directional coordinative bonding with 2D inorganic nanosheets allows to provide novel synthetic strategy to explore highly efficient energy-functional coordination-compound-based materials.

FeFe]-hydrogenase maturation: H-cluster assembly intermediates tracked by electron paramagnetic resonance, infrared, and X-ray absorption spectroscopy

[FeFe]-hydrogenase enzymes employ a unique organometallic cofactor for efficient and reversible hydrogen conversion. This so-called H-cluster consists of a [4Fe–4S] cubane cysteine linked to a diiron complex coordinated by carbon monoxide and cyanide ligands and an azadithiolate ligand (adt = NH(CH2S)2)·[FeFe]-hydrogenase apo-protein binding only the [4Fe–4S] sub-complex can be fully activated in vitro by the addition of a synthetic diiron site precursor complex ([2Fe]adt). Elucidation of the mechanism of cofactor assembly will aid in the design of improved hydrogen processing synthetic catalysts. We combined electron paramagnetic resonance, Fourier-transform infrared, and X-ray absorption spectroscopy to characterize intermediates of H-cluster assembly as initiated by mixing of the apo-protein (HydA1) from the green alga Chlamydomonas reinhardtii with [2Fe]adt. The three methods consistently show rapid formation of a complete H-cluster in the oxidized, CO-inhibited state (Hox-CO) already within seconds after the mixing. Moreover, FTIR spectroscopy support a model in which Hox-CO formation is preceded by a short-lived Hred′-CO-like intermediate. Accumulation of Hox-CO was followed by CO release resulting in the slower conversion to the catalytically active state (Hox) as well as formation of reduced states of the H-cluster.Graphic abstract

Cyano-ambivalence: Spectroscopy and photophysics of [Ru(diimine)(CN-BR3)4]2− complexes

The UV–visible absorption and luminescence spectra of [Ru(diimine)(CN)4]2− derivatives have been tuned over wide ranges through variations in solvent, substituents on the diimine ligand, and boronation of the cyanide ligands. Trifluoromethyl substitution at the 4 and 4′ positions of the diimine induces red shifts in metal-to-ligand charge-transfer (MLCT) absorption and luminescence bands. Boronation of the cyanide ligands produces substantial blue shifts in MLCT energies. The combination of diimine trifluoromethylation and cyanide boronation produces MLCT blue shifts that are about 75% as large as those produced by boronation alone.

Micro-level Estimation of Mercaptoacetic Acid Using its Inhibitory Effect to Mercury Catalyzed Ligand Exchange Reaction of Hexacyanoruthenate(II)

The sulfur-containing bioactive molecules (soft base) tends to bind strongly with Hg(II) (soft acid), thereby inhibiting the mercury (II) catalyzed exchange rate of cyanide ligand from [Ru(CN)6]4- by pyrazine. This inhibitory effect of Mercaptoacetic acid (MAA) encourages us to establish a new kinetic method for its micro-level estimation. Optimized reaction condition viz. 6.25×10-5 M [Ru(CN)64-], pH = 4.0, 7.5×10-4 M [Pyrazine], 0.05 M KCl, 8.5 ×10-5 M [Hg+2] and 45 (±0.1) oC temperature were utilized for the kinetic spectrophotometric investigation at 370nm (λmax of [Ru(CN)5 Pz]3- complex). The modified mechanistic scheme for inhibition caused by sulfur donor ligand, MAA has been proposed. The proposed analytical method provides the detection of MAA up to 2.0 × 10-6 M, indicates that the methodology can be effectively and economically employed to analyze the biological samples having MAA. This method can also be convincingly adopted for the quality check of MAA containing industrial products.

Synthesis and structural analysis of heteronuclear hexacyanochromate(III) complex with tris(2-aminoethyl)amine), [Cd(tren)(Htren)][Cr(CN)6]⋅2H2O

The synthesis and structural investigation of a new heteronuclear hexacyanochromate(III) complex based on amine containing tetradentate ligand tris(2-aminoethyl)amine ligand (tren) are reported. The complex was characterized by spectral (FT-IR and Raman), elemental, thermal analysis (TG, DTG and DTA) as well as single crystal X-ray diffraction (SC-XRD) techniques. From elemental and spectral data, the formulae, [Cd(tren)(Htren)][Cr(CN)6]⋅2H2O (1), for the metal complex has been proposed. Single crystal X-ray diffraction (SC-XRD) measurement showed that the asymmetric unit of 1 consists of one Cd(II) ion, one Cr(III) ion, six cyanide ligands, one tren and one Htren ligands and two crystal water molecules. The structure of 1 presents one of tren ligands was protonated and the coordinated to Cd(II) ion as a monodentate ligand. Other tren ligand was also bonded to Cd(II) ion as a tetradentate ligand to form a distorted trigonal-bipyramidal geometry. In the crystal structure, Cr(III) ion is coordinated by six carbon atoms from six different cyanide ligands, thus showing a distorted octahedral coordination geometry. In 1, The FT-IR and Raman spectral data of the complex compared with the crystallographic data, the results appear to be consistent with each other. Thermal properties of the title complex were investigated by thermogravimetric analysis (TG/DTG/DTA) in the temperature range of 30–700 °C in air atmosphere.

Reaction Chemistry of the syn-[Mo2O2(μ-S)2(S2)(DMF)3] Complex with Cyanide and Catalytic Thiocyanate Formation.

Removal of cyanide as nontoxic thiocyanate under physiological conditions may serve as a catalytic detoxification route in vivo. Aqueous catalytic reaction conditions were explored where at the conditions employed the reaction proceeded to exhaustion in 1 h. The complex, syn-[Mo2O2(μ-S)2(S2)(DMF)3] 1, participates in a ligand exchange reaction of the dimethylformamide ligands and cyanide. Simultaneous sulfur abstraction reaction from the terminal disulfide group forms thiocyanate and terminal sulfido ligand. Respective reaction rates for the two reactions appear competitive where different products were isolated solely based on change of reaction temperature. The approach to determine the number of cyanide ligands participating in the ligand exchange reaction by varying the stoichiometry and reaction temperature led to identification and isolation of tetranuclear complexes 2 and 5 and dinuclear complexes 3, 4, and 6. A synthesized and fully characterized thiocyanate analog of 6 (7) supports spectroscopic characterization of 6. The tetranuclear anion, [Mo4O4(μ-S)6(CN)4]4-, 2, was crystallized from a reaction at ambient temperature. The dinuclear anion, [Mo2O2(μ-S)2(S)(CN)3]3-, 3, was crystallized from similar reaction conditions at lower temperature. The reaction yield of thiocyanate obtained at pH of 7.4 and at 9.2 as a function of time, for several ratios of cyanide, favors the sulfur abstraction reaction at elevated pH. The sulfur abstraction reaction is the first step in a proposed mechanism of the reaction of cyanide and thiosulfate to form thiocyanate and sulfite by 1.

Access to Heteroleptic Fluorido‐Cyanido Complexes with a Large Magnetic Anisotropy by Fluoride Abstraction

AbstractSilicon‐mediated fluoride abstraction is demonstrated as a means of generating the first fluorido‐cyanido transition metal complexes. This new synthetic approach is exemplified by the synthesis and characterization of the heteroleptic complexes, trans‐[MIVF4(CN)2]2− (M=Re, Os), obtained from their homoleptic [MIVF6]2− parents. As shown by combined high‐field electron paramagnetic resonance spectroscopy and magnetization measurements, the partial substitution of fluoride by cyanide ligands leads to a marked increase in the magnetic anisotropy of trans‐[ReF4(CN)2]2− as compared to [ReF6]2−, reflecting the severe departure from an ideal octahedral (Oh point group) ligand field. This methodology paves the way toward the realization of new heteroleptic transition metal complexes that may be used as highly anisotropic building‐blocks for the design of high‐performance molecule‐based magnetic materials.

Water dispersible supramolecular assemblies built from luminescent hexarhenium clusters and silver(I) complex with pyridine-2-ylphospholane for sensorics

Abstract The work introduces regularities and driving forces of self-assembly of hexarhenium clusters [{Re6S8}L6]n− (L = SO32−, CN−, OH−) with [AgL′]+ (L′ = pyridine-2-ylphospholane) produced by dissociation of [Ag2L′2]2+ in aqueous solutions. The formation of nano-sized Re6 Ag assemblies is detected by the spectral measurements in the solutions and by the solid-state analysis of the separated colloids. The nature of L is highlighted as the main factor affecting the assembly. The poor affinity of the SO32− ligands to Ag+ restricts the assembly of [{Re6S8}(SO3)6]10− with the silver(I) complexes. [{Re6S8}(OH)6]4− is more promising candidate for the heterometallic assembly contributed by both counter-ion binding and coordination bonds, while the efficient coordination of Ag+ via the nitrogen of the cyanide ligands of [{Re6S8}(CN)6]4− is the main driving force for the Re6 Ag assembly. The stronger impact of [Ag2L′2]2+ relative to Ag+ cations on the formation of Re6 Ag assemblies in aqueous solutions, as well as the presence of L′ in the separated colloidal phase, indicate the important role of the L′ ligand in the studied supramolecular systems. The cluster-centered luminescence serves as signaling system at the binding of glutathione, cysteine and dithiothreitol with Ag+ ions of the heterometallic assemblies. The assemblies based on [{Re6S8}(CN)6]4− are able to discriminate glutathione versus cysteine, while the assemblies formed by [{Re6S8}(OH)6]4− give the unselective luminescence response on the both biothiols at the concentration level of 2 μM.

Cation-anion pairs of niobium clusters of the type [Nb6Cl12(RCN)6][Nb6Cl18] (R=Et,nPr,iPr) with nitrile ligandsRCN forming stabilizing inter-ionic contacts

AbstractThree new niobium cluster compounds with edge bridged, octahedral hexanuclear metal cores have been synthesised. They consist of cluster pairs with [Nb6Cl12(RCN)6]2+cations, [Nb6Cl18]2−anions, and co-crystallised nitrile molecules, withR = C2H5(propionitrile),nC3H7(butyronitrile),iC3H7(isobutyronitrile). The synthesis is based on the dehydration of [Nb6Cl14(H2O)4] · 4(H2O) with carboxylic acid anhydrides in the presences of an excess of the respective nitrile. An interesting aspect of these compounds is that the metal atoms of the cluster cation have an average oxidation state different from that of the cluster anion, the former being oxidized losing two electrons. In crystals of all three compounds layers of cluster cations are separated by layers of cluster anions. Perpendicular to these layers of the same cluster types, every cation is surrounded by four anions and vice versa. Between the cations and anions short distances are found between the halogenido ligands and the positively charged C atoms of the nitrile ligands (N–C · · · Cl angles of ~90°). These contacts indicate relatively strong dipole-dipole interactions, which presumably contribute to the arrangement of the cluster ions in the crystals.

The versatility of lithium cation coordination modes in salts with [W(CN)6(bpy)]2− anions

Effect of the cation size (compared to Cs+) in Li2[W(CN)6(bpy)] salts on the nature of the interaction with cyanide ligands and on the crystal structure is discussed, unusual decrease of the W–W distance and increase of cell volume are observed.