Cyanide Complexes Research Articles

HCAII-inspired catalysts for making carbon dioxide-based copolymers: The role of metal-hydroxide bond

The general characteristics of the active center of the catalysts (including zinc-cobalt(III) double metal cyanide complex [Zn-Co(III) DMCC]) for the copolymerization reaction of carbon dioxide (CO2) with epoxide are summarized. By comparing the active center, catalytic performance of the Zn-Co(III) DMCC (and other catalysts) with HCAII enzyme in the organism for activating CO2 (COS and CS2), we proposed that the metal-hydroxide bond (M-OH), which is the real catalytic center of human carbonic anhydride II (HCAII), is also the catalytic (initiating) center for the copolymerization. It accelerates the copolymerization and forms a closed catalytic cycle through the chain transfer reaction to water (and thus strictly meets the definition of the catalyst). In addition, the metal-hydroxide bond catalysis could well explain the oxygen/sulfur exchange reaction (O/S ER) in metal (Zn, Cr)-catalyzed copolymerization of COS (and CS2) with epoxides. Therefore, it is very promising to learn from HCAII enzyme to develop biomimetic catalyst for highly active CO2/epoxide copolymerization in a well-controlled manner under mild conditions.

Matrix Infrared Spectra of Manganese and Iron Isocyanide Complexes.

Mono and diisocyanide complexes of manganese and iron were prepared via the reactions of laser-ablated manganese and iron atoms with (CN)2 in an argon matrix. Product identifications were performed based on the characteristic infrared absorptions from isotopically labeled (CN)2 experiments as compared with computed values for both cyanides and isocyanides. Manganese atoms reacted with (CN)2 to produce Mn(NC)2 upon λ > 220 nm irradiation, during which MnNC was formed mainly as a result of the photoinduced decomposition of Mn(NC)2. Similar reaction products FeNC and Fe(NC)2 were formed during the reactions of Fe and (CN)2. All the product molecules together with the unobserved cyanide isomers were predicted to have linear geometries at the B3LYP level of theory. The cyanide complexes of manganese and iron were computed to be more stable than the isocyanide isomers with energy differences between 0.4 and 4 kcal/mol at the CCSD(T) level. Although manganese and iron cyanide molecules are slightly more stable according to the theory, no absorption can be assigned to these isomers in the region above the isocyanides possibly due to their low infrared intensities.

Preparation of 15N-labeled Potassium Ferrocyanide for Tracer Studies

Isotopic labels are widely used to trace the fate and cycling of common environmental contaminants. Many of the labeled materials are not available commercially and, depending on the complexity of the substance, the label and the enrichment level, custom syntheses are costly. A simple, straightforward, and cost effective method for the preparation of a highly enriched, 15N-labeled potassium ferrocyanide (K4[Fe(C15N)6]*3H2O) has been developed to meet the requirements of related tracer experiments and minimize their costs. In this case, the 15N label was used to quantify iron cyanide detoxification (biodegradation and/or transformation) within soil-plant-systems. 15N-labeled potassium cyanide (KC15N) and a ferrous iron salt have been used for the synthesis. Extensive qualitative and quantitative analyses showed a product, entirely identical in its functional and elemental components to commercial non-labeled K4[Fe(CN)6]*3H2O and in its 15N enrichment to the KC15N used for its synthesis. To investigate their behavior and fate in various environmental compartments, other labeled iron or metal cyanide complexes might be synthesized in analogous manner.

Enhancing destruction of copper (I) cyanide and subsequent recovery of Cu(I) by a novel electrochemical system combining activated carbon fiber and stainless steel cathodes

Metal recovery is an attractive strategy for treatment of heavy metal wastewater. Heavy metal cyanide complexes are common pollutants in electroplating or mine industry wastewater, which usually hinder metal recovery due to the high stability of these complexes. A novel electrochemical system with activated carbon fiber and stainless steel combined cathodes was constructed for copper (I) cyanide (Cu(CN)32−) destruction and Cu(I) recovery. The destruction of cyanide was significantly improved by combining the stainless steel and activated carbon fiber cathodes due to the enhancement of electro-generated H2O2, which was promoted due to catalysis by copper deposited at the cathodes. Both the destruction of Cu(CN)32− and recovery of Cu(I) at 75min attained 95.0±3.0%, which were higher than values obtained using stainless steel or activated carbon fiber as individual cathodes. The rate of Cu(CN)32 destruction and Cu(I) recovery increased with increasing pH. The optimal current density was 50A/m2, and higher current density caused more side reactions. Cu(CN)32− was successively transformed into Cu(CN)2−, CNO− and Cu(I), and the liberated Cu(I) was recovered as Cu(0) on the stainless steel and activated carbon fiber electrodes.

Development of a mixed microbial culture for thiocyanate and metal cyanide degradation.

The degradation capacity of a mixed culture of Agrobacterium tumefaciens SUTS 1 and Pseudomonas monteilii SUTS 2 for thiocyanate and metal cyanide, in the form of zinc and cadmium, has been determined. The growth of a mixed culture of SUTS 1 and SUTS 2 in cyanide complexes and the cyanide removal efficiency of a fixed-film bio-column system were studied. The results showed that the mixed culture of bacteria can survive and grow in broth media containing thiocyanate and metal cyanide complexes with a maximum cell of 1.03×108CFU/mL on day 3. In addition, the optimal conditions of the fixed-film bio-column system were continuously tested for 24h, and it was found that this system had the highest removal efficiency at a flow rate of 10mL/min and 21min of empty bed retention time, with decreasing thiocyanate, zinc, and cadmium from 85, 0.44, and 0.044 to 65, 0.21, and 0.038mg/L, respectively; this is in contrast to cyanide, which was not found within 12h. Next, the conditions were maintained for 30days, and it was found that the system had removed more than 50% of cyanide complexes, except cadmium. The complex residues were 29.96, 0.16, 0.204, and 0.085mg/L of thiocyanate, cyanide, zinc, and cadmium, respectively. In addition, the growth of the SUTS 1 and SUTS 2 mixed culture increased. The by-product compounds sulfate and nitrate were found throughout the experiment, whereas bicarbonate and ammonia were found only on certain days.

Recovery of [Au(CN) 2 ] − from gold cyanidation with graphene oxide as adsorbent

Abstract The recovery of gold cyanide complex Au(CN) 2 − from gold cyanidation with graphene oxide (GO) and GO hydrogel have been studied to explore the possibility of the application of GO or GO hydrogel in gold cyanidation process for extracting gold. The study was performed on the adsorption of artificial Au(CN) 2 − aqueous solution on GO and GO hydrogel. The adsorption results, as well as the SEM-EDS, AFM and XPS, demonstrated that GO was a better adsorbent for the recovery of Au(CN) 2 − from aqueous solution than conventional activated carbon because of its higher adsorption capacity and adsorption rate. It has been also found that the adsorption of Au(CN) 2 − on GO followed the Langmuir isotherm and fitted well with both the pseudo-first-order and pseudo-second-order kinetics models. The recovery of Au(CN) 2 − with GO might be attributed to the interaction between Au(CN) 2 − and oxygenous function groups on GO surface. GO hydrogel exhibited excellent Au(CN) 2 − adsorption property and easy separation, which enabled it a potential adsorbent in gold cyanidation.

Preparation and Characterization of Group 13 Cyanides

AbstractInvited for the cover of this issue is the group of Ralf Haiges at the University of Southern California. The image depicts characters from the popular web comic “Cyanide & Happiness” alongside some of the cyanide complexes synthesized. Read the full text of the article at 10.1002/chem.201700611.

H2O2 Assisted Photoelectrocatalytic Oxidation of Ag-Cyanide Complexes at Metal-free g-C3N4 Photoanode with Simultaneous Ag Recovery

A g-C3N4 thin film was synthesized by a liquid-based reaction onto ITO substrate via the calcination treatment. The resultant electrode was used as photoanode for photoelectrocatalytic (PEC) oxidation of Ag cyanide complexes with simultaneous Ag recovery, which was enhanced with the addition of H2O2. Surface variation of the g-C3N4 photoanode and titanium cathode was analyzed using SEM, XRD, and XPS techniques. It was observed that, with the cyanide oxidation, Ag oxides and metal Ag were deposited onto the g-C3N4 photoanode and titanium cathode, respectively. The photoelectrochemical response of the g-C3N4 photoanode was obviously increased after the AgO deposition. ESR and trapping experiments confirmed the existence and roles of •O2– and •OH in the PEC oxidation process. The photogenerated electrons from g-C3N4 could be captured by •O2– and H2O2, generating •OH radicals for oxidizing the Ag cyanide complexes. Meanwhile, the deposition of AgO species onto the g-C3N4 surface increased its electrical condu...

Darmstadtium, roentgenium, and copernicium form strong bonds with cyanide

AbstractWe report the structures and properties of the cyanide complexes of three superheavy elements (darmstadtium, roentgenium, and copernicium) studied using two‐ and four‐component relativistic methodologies. The electronic and structural properties of these complexes are compared to the corresponding complexes of platinum, gold, and mercury. The results indicate that these superheavy elements form strong bonds with cyanide. Moreover, the calculated absorption spectra of these superheavy‐element cyanides show similar trends to those of the corresponding heavy‐atom cyanides. The calculated vibrational frequencies of the heavy‐metal cyanides are in good agreement with available experimental results lending support to the quality of our calculated vibrational frequencies for the superheavy‐atom cyanides.

Selective Complexation of Cyanide and Fluoride Ions with Ammonium Boranes: A Theoretical Study on Sensing Mechanism Involving Intramolecular Charge Transfer and Configurational Changes.

The anion binding selectivity and the recognition mechanism of two isomeric boranes, namely, 4-[bis(2,4,6-trimethylphenyl)boranyl]-N,N,N-trimethylaniline ([p-(Mes2B)C6H4(NMe3)]+, 1, where "Mes" represents mesitylene and "Me" represents methyl) and 2-[bis(2,4,6-trimethylphenyl)boranyl]-N,N,N-trimethylaniline ([o-(Mes2B)C6H4(NMe3)]+, 2) has been investigated using density functional theory (DFT) and time dependent-density functional theory (TD-DFT) methods. Natural population analysis indicates that the central boron atoms in 1 and 2 are the most active centers for nucleophilic addition of anions. The negative magnitude of free energy changes (ΔG) reveals that out of CN-, F-, Cl-, Br-, NO3-, and HSO4- only the binding of CN- and F- with 1 and 2 is thermodynamically feasible and spontaneous. In addition, the calculated binding energies reveal that the CN- is showing lesser binding affinity than F- both with 1 and 2, while other ions, viz. NO3-, HSO4-, Br-, and Cl-, either do not bind at all or show very insignificant binding energy. The first excited states (S1) of 1 and 2 are shown to be the local excited states with π → σ* transition by frontier molecular orbital analysis, whereas fourth excited states (S4) of 4-[bis(2,4,6-trimethylphenyl)boranyl]-N,N,N-trimethylaniline cyanide ([p-(Mes2B)C6H4(NMe3)] CN, 1CN, the cyano form of 1) and 4-[bis(2,4,6-trimethylphenyl)boranyl]-N,N,N-trimethylaniline fluoride ([p-(Mes2B)C6H4(NMe3)] F, 1F, the fluoro form of 1) and fifth excited state (S5) of 2-[bis(2,4,6-trimethylphenyl)boranyl]-N,N,N-trimethylaniline fluoride ([o-(Mes2B)C6H4(NMe3)] F, 2F, the fluoro form of 2) are charge separation states that are found to be responsible for the intramolecular charge transfer (ICT) process. The synergistic effect of ICT and partial configuration changes induce fluorescence quenching in 1CN, 1F, and 2F after a significant internal conversion (IC) from S4 and S5 to S1.

Synthesis, characterization, DFT calculations and antibacterial activity of palladium(II) cyanide complexes with thioamides

Palladium(II) cyanide complexes of thioamides (or thiones) having the general formula PdL2(CN)2, where L = Thiourea (Tu), Methylthiourea (Metu), N,N′-Dimethylthiourea (Dmtu), Tetramethylthiourea (Tmtu), 2-Mercaptopyridine (Mpy) and 2-Mercaptopyrimidine (Mpm) were prepared by reacting K2[PdCl4] with potassium cyanide and thioamides in the molar ratio of 1:2:2. The complexes were characterized by elemental analysis, thermal and spectroscopic methods (IR, 1H and 13C NMR). The structures of three of the complexes were predicted by DFT calculations. The appearance of a band around 2100 cm−1 in IR and resonances around 120–130 ppm in the 13C NMR spectra indicated the coordination of cyanide to palladium(II). More than one resonances were observed for CN− carbon atoms in 13C NMR indicating the existence of equilibrium between different species in solution. DFT calculations revealed that in the case of the palladium(II) complex of Tmtu, the ionic dinuclear [Pd(Tmtu)4][Pd(CN)4] form was more stable than the dimer of mononuclear complex [Pd(Tmtu)2(CN)2] by 0.91 kcal mol−1, while for the complexes of Tu or Mpy ligands, the nonionic [Pd(L)2(CN)2] forms were more stable than the corresponding [Pd(L)4][Pd(CN)4] complexes by 1.26 and 6.49 kcal mol−1 for L = Tu and Mpy, respectively. The complexes were screened for antibacterial effects and some of them showed significant activities against both gram positive as well as gram negative bacteria.

Low Voltage Charge/Discharge Behavior of Manganese Hexacyanoferrate

Recently, Prussian blue analogues (PBAs) have been reported to exhibit a low voltage charge/discharge behavior with high capacity (300–545 mAh/g) in lithium-ion secondary batteries (LIBs) [...]

Cyanide linkage isomerism in cerium(III) and uranium(III) complexes. A relativistic DFT study

The chemistry of cyanide complexes of the f-elements has witnessed significant recent advances, showing in particular the remarkable ability of the cyanide ligand to stabilize uranium compounds in their +3 to +6 oxidation states and its capacity to adopt two distinct ligation modes, namely cyanide M−CN or isocyanide M−NC, towards trivalent f-ions. Here, we have theoretically investigated the tris(cyanide) complexes [ML2X3]2– (M = Ce3+, U3+; L = C5H4Me, N(SiMe3)2; X = CN, NC), using relativistic DFT computations, focusing on cyanide (CN−) and isocyanide (NC−) coordination competition and differences between their electronic structures. X-ray crystal data reveal distinct coordination modes of the CN ligand towards uranium and cerium metal centers. Interestingly, in the case of the cerium complexes, and contrarily to the uranium ones, the coordination mode of the cyanide ligand depends on the co-ligand L attached to the metal. The observed coordination in these tris(cyanide) complexes is driven by the binding energies of the CN−/NC− ligands to the metals. The solvent is shown to play a determining role for the chosen coordination. The developed methodology can help to confirm the cyanide or isocyanide coordination mode when X-ray crystal data are not conclusive or to predict the configuration of a complex to be synthesized. Another application is in the field of lanthanide (III)/actinide (III) differentiation.

Quantitative proteomic analysis of Pseudomonas pseudoalcaligenes CECT5344 in response to industrial cyanide-containing wastewaters using Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS).

Biological treatments to degrade cyanide are a powerful technology for cyanide removal from industrial wastewaters. It has been previously demonstrated that the alkaliphilic bacterium Pseudomonas pseudoalcaligenes CECT5344 is able to use free cyanide and several metal−cyanide complexes as the sole nitrogen source. In this work, the strain CECT5344 has been used for detoxification of the different chemical forms of cyanide that are present in alkaline wastewaters from the jewelry industry. This liquid residue also contains large concentrations of metals like iron, copper and zinc, making this wastewater even more toxic. To elucidate the molecular mechanisms involved in the bioremediation process, a quantitative proteomic analysis by LC-MS/MS has been carried out in P. pseudoalcaligenes CECT5344 cells grown with the jewelry residue as sole nitrogen source. Different proteins related to cyanide and cyanate assimilation, as well as other proteins involved in transport and resistance to metals were induced by the cyanide-containing jewelry residue. GntR-like regulatory proteins were also induced by this industrial residue and mutational analysis revealed that GntR-like regulatory proteins may play a role in the regulation of cyanide assimilation in P. pseudoalcaligenes CECT5344. The strain CECT5344 has been used in a batch reactor to remove at pH 9 the different forms of cyanide present in industrial wastewaters from the jewelry industry (0.3 g/L, ca. 12 mM total cyanide, including both free cyanide and metal−cyanide complexes). This is the first report describing the biological removal at alkaline pH of such as elevated concentration of cyanide present in a heterogeneous mixture from an industrial source.

Enantioselective Copper-Catalyzed Intermolecular Amino- and Azidocyanation of Alkenes in a Radical Process.

Asymmetric copper-catalyzed intermolecular amino- and azidocyanation reactions of alkenes have been developed that proceed via a radical process in which a key benzylic radical intermediate is enantioselectively trapped by a chiral Box/CuII cyanide complex. A variety of enantiomerically enriched β-amino/azido alkylnitriles were efficiently synthesized. The β-azido alkylnitriles could be converted into a series of highly valuable optically active amine-based building blocks and bioactive compounds.

Enantioselective Copper‐Catalyzed Intermolecular Amino‐ and Azidocyanation of Alkenes in a Radical Process

AbstractAsymmetric copper‐catalyzed intermolecular amino‐ and azidocyanation reactions of alkenes have been developed that proceed via a radical process in which a key benzylic radical intermediate is enantioselectively trapped by a chiral Box/CuII cyanide complex. A variety of enantiomerically enriched β‐amino/azido alkylnitriles were efficiently synthesized. The β‐azido alkylnitriles could be converted into a series of highly valuable optically active amine‐based building blocks and bioactive compounds.

Crystal structures of two mixed-valence copper cyanide complexes with N-methyl-ethylenedi-amine.

The crystal structures of two mixed-valence copper cyanide compounds involving N-methyl-ethylenedi-amine (meen), are described. In compound (I), poly[bis(μ3-cyanido-κ3C:C:N)tris(μ2-cyanido-κ2C:N)bis(N-methylethane-1,2-di-amine-κ2N,N')tricopper(I)copper(II)], [Cu4(CN)5(C3H10N2)2] or Cu4(CN)5meen2, cyanide groups link CuI atoms into a three-dimensional network containing open channels parallel to the b axis. In the network, two tetra-hedrally bound CuI atoms are bonded by the C atoms of two end-on bridging CN groups to form Cu2(CN)6 moieties with the Cu atoms in close contact at 2.560 (1) Å. Other trigonally bound CuI atoms link these units together to form the network. The CuII atoms, coordinated by two meen units, are covalently linked to the network via a cyanide bridge, and project into the open network channels. In the mol-ecular compound (II), [(N-methylethylenediamine-κ2N,N')copper(II)]-μ2-cyanido-κ2C:N-[bis(cyanido-κC)copper(I)] monohydrate, [Cu2(CN)3(C3H10N2)2]·H2O or Cu2(CN)3meen2·H2O, a CN group connects a CuII atom coordinated by two meen groups with a trigonal-planar CuI atom coordinated by CN groups. The mol-ecules are linked into centrosymmetric dimers via hydrogen bonds to two water mol-ecules. In both compounds, the bridging cyanide between the CuII and CuI atoms has the N atom bonded to CuII and the C atom bonded to CuI, and the CuII atoms are in a square-pyramidal coordination.

Effect of the solvation state of electron in dissociative electron attachment reaction in aqueous solutions.

It is generally considered that the pre-solvated electron and the solvated electron reacting with a solute yield the same product. Silver cyanide complex, Ag(CN)2-, is used as a simple probe to demonstrate unambiguously the existence of a different reduction mechanism for pre-hydrated electrons. Using systematic multichannel transient absorption measurements at different solute concentrations from millimolar to decimolar, global data analysis and theoretical calculations, we present the dissociative electron attachment on Ag(CN)2-. The short-lived silver complex, Ag0(CN)22-, formed by hydrated electron with nanosecond pulse radiolysis, can be observed at room temperature. However, at higher temperatures only the free silver atom, Ag0, is detected, suggesting that Ag0(CN)22- dissociation is fast. Surprisingly, pulse radiolysis measurements on Ag(CN)2- reduction, performed by a 7 ps electron pulse at room temperature, show clearly that a new reduced form of silver complex, AgCN-, is produced within the pulse. This species, absorbing at 560 nm, is not formed by the hydrated electron but exclusively by its precursor. DFT calculations show that the different reactivity of the hydrated and pre-hydrated electrons can be due to the formation of different electronic states of Ag0(CN)22-: the prehydrated electron can form an excited state of this complex, which mainly dissociates into Ag0CN- + CN-.

Photocatalytic water oxidation by persulphate with a Ca2+ ion-incorporated polymeric cobalt cyanide complex affording O2 with 200% quantum efficiency.

Incorporation of a small amount of Ca2+ ions into a polymeric cobalt cyanide complex to form Cax[CoII(H2O)2]1.5-x[CoIII(CN)6] resulted in a significant enhancement of activity for photocatalytic water oxidation in a buffer solution (pH 7.0) containing [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine) as a photocatalyst and Na2S2O8 as an electron acceptor to achieve a quantum efficiency of 200%.

Efficient adsorption of Au(CN)2− from gold cyanidation with graphene oxide-polyethylenimine hydrogel as adsorbent

Abstract The adsorption of gold cyanide complex ion (Au(CN)2−) on graphene oxide-polyethylenimine hydrogel (GO/PEI hydrogel) from gold cyanidation has been studied to explore the possibility of the application of GO/PEI hydrogel in gold cyanidation process for extracting gold from ores. The adsorption was carried out in artificial Au(CN)2− aqueous solution with GO/PEI hydrogel as adsorbent. The experimental results, as well as IR, XPS and SEM−EDS, have shown that GO/PEI hydrogel exhibited a high adsorption capacity and a fast adsorption rate of Au(CN)2−, suggesting that GO/PEI hydrogel might be a good adsorbent for the recovery of Au(CN)2−. The adsorption of Au(CN)2− on GO/PEI hydrogel obeyed the Langmuir isotherm model and fitted well with the pseudo second order model. The good recovery of Au(CN)2− was largely related to the porous structure, large specific surface area, as well as the oxygenous functional groups on the surface of GO/PEI hydrogel.