A Cyclometalated NHC Iridium Complex Bearing a Cationic (η5-Cyclopentadienyl)(η6-phenyl)iron Backbone**

Nucleophilic substitution of [(η⁵-cyclopentadienyl)(η⁶-chlorobenzene)iron(II)] hexafluorophosphate with sodium imidazolate resulted in the formation of [(η⁵-cyclopentadienyl)(η⁶-phenyl)iron(II)]imidazole hexafluorophosphate. The corresponding dicationic imidazolium salt, which was obtained by treating this imidazole precursor with methyl iodide, underwent cyclometallation with bis[dichlorido(η⁵-1,2,3,4,5-pentamethylcyclopentadienyl]iridium(III) in the presence of triethyl amine. The resulting bimetallic iridium(III) complex is the first example of an NHC complex bearing a cationic and cyclometallated [(η⁵-cyclopentadienyl)(η⁶-phenyl)iron(II)]⁺ substituent. As its iron(II) precursors, the bimetallic iridium(III) complex was fully characterized by means of spectroscopy, elemental analysis and single crystal X-ray diffraction. In addition, it was investigated in a catalytic study, wherein it showed high activity in transfer hydrogenation compared to its neutral analogue having a simple phenyl instead of a cationic [(η⁵-cyclopentadienyl)(η⁶-phenyl)iron(II)]⁺ unit at the NHC ligand.     

Solvation and reactivity of a helical binuclear iron(II) complex with a tetradentate Schiff-base ligand

Reaction of 2-acetylpyridine, hydrazine, and an iron(II) salt gives a low-spin binuclear iron(II) complex, [Fe₂(pmk)₃]⁴⁺, in which three tetradentate Schiff base ligands span the two metal centres to give a complex of helical geometry. We report solubilities of the iodide and perchlorate salts, in H₂O, in aqueous MeOH, and in aqueous DMSO (perchlorate only), up to 60% by vol of organic cosolvent. Transfer chemical potentials for the complex cation from H₂O into the respective mixed solvents have been derived from these solubilities, to give a picture of solvation of this complex in the media studied. Kinetics of base hydrolysis of [Fe₂(pmk)₃]⁴⁺ have been established, in H₂O and in 40% MeOH, 20 and 40% i -PrOH, and 20 and 40% DMSO, at 298.2 K. The reactivity of [Fe₂(pmk)₃]⁴⁺ is discussed in relation to reactivities of a selection of iron(II)-diimine complexes, ranging from [Fe(bipy)₃]²⁺ and [Fe(phen)₃]²⁺ to ligand-encapsulated cage complexes.     

Micellar electrokinetic chromatography of tri aza aromatic ligand compounds of iron (II): influence of bile salt type on enantiomeric separation.

Micellar electrokinetic chromatography is used with a variety of bile salt micelles to separate the enantiomers of bis(8-((pyridine-2-methylene)amino)quinoline)iron(II) hexafluorophosphate, Fe(PMAQ)2(PF6)2; bis(8-((pyridine-2-methylene)amino)lepidine iron(II) hexafluorophosphate, Fe(PMAL)2(PF6)2; and bis(1-(2-pyridinyl)ethylidine)-8-aminoquinoline iron(II) hexafluorophosphate, Fe(PEAQ)2(PF6)2. The influence of ten different bile salts on the resolution of each pair of enantiomers is investigated. Significant changes in resolution are seen depending upon the bile salt used. The dihydroxy bile salts are superior to the trihydroxy bile salts in terms of resolution, and the taurine or glycine conjugated bile salts yield better results than the unconjugated bile salts. Resolution for most enantiomers is maximized in a buffer solution containing 10-15% acetone and employing either taurochenodeoxycholic or glycochenodeoxycholic acid as the bile salt. Evidence for the separation of the corresponding Fe(III) complexes is presented.     

Isomeric forms of tris-Schiff base complexes of iron(II): structure of the complex derived from 2-acetyl pyridine and methylamine

Summary The structure of the tetrahydrate of the nitroprusside salt of the tris-ligand-Fe^II complex of the Schiff base derived from 2-acetyl pyridine and methylamine has been established by x-ray diffraction methods. The cation has themer-configuration in this salt in the solid phase. Kinetic and spectroscopic, particularly¹H n.m.r., results indicate that bothmer-andfac-isomers of this, and of related complexes, have to be considered in solution. Kinetics of base hydrolysis of the title cation, and its solvation, in MeOH-H₂O mixtures are described and compared with those for other low-spin Fe^II-diimine complexes.     

Kinetics of reactions of the tris-(4-methyl-1,10-phenanthroline)iron(II) cation

Summary Kinetic parameters are reported for aquation of the tris-(4-methyl-1,10-phenanthroline) iron(II) [Fe(4-Mephen)₃]²⁺, cation and for its reactions with hydroxide, cyanide, and peroxodisulphate. Activation volumes have been determined for the two last-named reactions; they reflect the importance of solvation changes in transition state formation.     

The rhodium-catalysed methanolysis of aryl acetates and of the hexafluorophosphate anion

Summary In nitromethane, the methanolysis of aryl acetates is catalysed by the tetrafluoroborate and hexafluorophosphate salts of the ( ⁵-ethyltetramethylcyclopentadienyl) ( ⁶-benzen)rhodium(III) cation. Under the conditions of the methanolysis, the anion of the latter salt reacts with methanol to give dimethyl phosphorofluoridate. The hydrogen fluoride formed also in this reaction is thought to be responsible for the greater efficiency of the hexafluorophosphate salt as a catalyst for the methanolysis.     

EPR Spectra of complexes of 3,5-di-tert-butyl-o-benzoquinone with lead diethyldithiocarbamate,ethylxanthate, and o,o-diethyldithiophosphate and reaction with bases

We have observed the solvent dependence of the hyperfine coupling constant for hyperfine coupling with the metal nucleus in ortho-semiquinone complexes of lead(II) diethyldithiocarbamate, ethylxanthate, and O,O-diethyldithiophosphate. This is connected with the process of solvation of the metal cation with the solvent molecules. We observe a correlation between the hyperfine coupling constant (due to the²⁰⁷Pb isotope) and the basicity factor of the solvent. Using the EPR method, we have studied the dynamics of solvation of the 3,5-di-tert-butyl-o-semiquinone complex of lead diethyldithiocarbamate by amines. We have obtained the thermodynamic and kinetic parameters of the solvation process. We observe a compensation effect for the kinetics of the forward and backward solvation reactions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 52–58, January, 1990.     

Spectrophotometric study on the reactions of iron(II) with bromopyrogallol red and pyrogallol red in the presence of quaternary ammonium salt

Iron(II) in the presence of quaternary ammonium salt reacts with bromopyrogallol red (BPR) and pyrogallol red (PR) to form a ternary complex. The ternary complex Fe(II)-BPR-TDTA is suitable for the determination of trace amounts of iron. The complex has an absorbance maximum at 635 nm with molar absorptivity 5.6 × 10⁴ liters mol^?1 cm^?1, in which the molar ratio of iron(II) to BPR is 1:3. Beer's law is obeyed over the range 0.08–0.5 μg/ml of iron. Masking agents allow most interferences to be suppressed.     

Binding of fluorine containing anions by new cationic Co(III) complex: Competitive interaction of chloride and hexafluorophosphate with [Co(phen)(H2biim)2]

A new mixed ligand cobalt(III) complex salt [Co(phen)(H₂biim)₂]Cl₃ (1) (where phen = 1,10-phenanthroline, H₂biim = 2,2′-biimidazole) has been synthesized for the first time. In an effort to explore this new cationic complex [Co(phen)(H₂biim)₂]³⁺ as binding agent for fluoroanions, complex salt [Co(phen)(H₂biim)₂](PF₆)₂Cl·2H₂O(2) has been synthesized and characterized. Single crystal X-ray structure determination has revealed that complex salt 2 crystallizes in monoclinic crystal system with space group P2₁/c and consist of one complex cation, one chloride, two hexafluorophosphate anions and two water molecules of crystallization. The packing analyses revealed that the complex cations are arranged in such a way that N-H groups of biimidazole moiety are involved in N-H?Cl interaction with chloride ion while C-H groups of phen/H₂biim are involved in C-H?F interaction with hexafluorophosphate to keep these groups in close proximity. A strong network of hydrogen bond interactions C-H?F, N-H?O, N-H?Cl, C-H?O (water) and O-H?O (water) are responsible for the stabilization of 3D supramolecular architecture. To the best of our knowledge, this is the first crystal structure of any salt containing the cation [Co(phen)(H₂biim)₂]³⁺.     

Mercuration with Mercury(II) Trifluoroacetate of (η6-Aniline)- or (N,N-dimethylaniline)(η5-cyclopentadienyl)iron(II)

The reaction of mercury(II) trifluoroacetate with the hexafluorophosphate of the ⁶-aniline-⁵cyclopentadienyliron(II) cation under reflux in dry ethanol gives rise to N-mono- and N,N-disubstituted mercury-containing salts of this cation. The same mercury-containing salts have been synthesized by the action of mercury(II) trifluoroacetate on the deprotonation product of the (⁶-aniline)(⁵-cyclopentadienyl)iron(II) cation. Direct mercuration of the [⁶-(N,N-dimethylaniline)](⁵-cyclopentadienyl)iron(II) cation into the para position of the benzene ring of the arene ligand has been performed. The reactivity of the compounds obtained has been studied.     

Complexes organometalliques conducteurs derives de metallocenes et du tetracyanoquinodimethane

Organometallic conductors have been obtained from the reaction of substituted ferrocenic,arene-CpFe^II and bis-areneiron(II) salts with TCNQ⁰ and/or TCNQ⁻. The ionic complex of the bis(trimethylbenzene)iron(II) cation and TCNQ⁻ shows a reverse electron transfer from TCNQ⁻ to the cation, after thermal activation, yielding a semi-conductor species.     

Readily prepared metallo-supramolecular triple helicates designed to exhibit spin-crossover behaviour

New dinuclear supramolecular cylinders have been designed to exhibit spin-crossover behaviour, a form of molecular bistability. This has been achieved within the framework of our imine-based approach to supramolecular architecture by switching from pyridylimine systems to imidazolimines. Spin-crossover behaviour is achieved while retaining the simplicity and ease-of-synthesis of our molecular design. The imidazole groups used also introduce additional NH groups that engage in hydrogen-bonding to anions and solvents. In the case of the iron(II) tetrafluoroborate complex this hydrogen bonding links supramolecular cylinders into an extended two-dimensional array. Consistent with this, a sharper spin-crossover transition is observed for this compound than for the corresponding hexafluorophosphate salt. More subtle anion effects are indicated in the perchlorate salt which gives a two-step spin conversion, thereby displaying tristability.     

Multilayered iron complexes of metacyclophanes. 1H NMR behavior

Syntheses are described for a series of (η⁶-cyclophane)(η⁵cyclopentadienyl)iron(II) complexes, where the cyclophane moiety is anti-[2.2]metacyclophane, anti-4,12-dimethyl[2.2]metacyclophane, anti-4,12-dimethyl-7,15-dimethoxy[2.2]metacyclophane, and [2.2](2,5)thiophenophane. The triple-layered complexes η⁶,η⁶-anti-[2.2]metacyclophane)bis[(η⁵-cyclopentadienyl)iron(II)] bis(hexafluorophosphate) and (η⁶,η⁶-anti-4,12-dimethyl[2.2]metacyclophane)bis[(η⁵-cyclopentadienyl)iron(II)] bis(hexafluorophosphate) were also prepared. The NMR spectra of these compounds provide a useful insight into the nature of the iron-cyclophane bonding.     

Role of ionic strength in the kinetics of formation of the monochelate of nickel(II) with heptane-3,5-dione

The kinetics and mechanism of the reaction of Ni(II) with heptane-,5-dione (Hhptd) have been investigated in concentrated sodium perchlorate aqueous solutions at 298 K. The kinetic data in the different media are consistent with a mechanism in which Ni(II) reacts with the enol form of the ligand. The observed positive salt effect on the rate of the reaction of formation of the complex Nihptd⁺ is rationalized taking into account the increase of the rate of water exchange from the first solvation sphere of the metal ion to the bulk solvent when increasing salt concentration.     

Extraction—spectrophotometric determination of trace amounts of iron in waters with pyrogallol red and zephiramine

The simple removal of excess of co-extracted reagent in the solvent extraction of metal complex anions with a quaternary ammonium salt greatly improves the determination of iron(II) with pyrogallol red and zephiramine. The method with pyrogallol red is suitable for the determination of trace amounts of iron in natural waters. The apparent molar absorptivities of the iron(II) complex in chloroform are 7.5×10⁴ and 10.3×10⁴ 1 mol^-1 cm^-1 at 560 and 298 nm, respectively. A large excess of reagent can be added, and the ternary complex can be completely extracted over the pH range 8.5–10. Masking agents allow most interferences to be suppressed. The method is suitable for the analysis of potable, river and sea waters.     

Kinetic and mechanistic studies on the oxidation of hydroxylamine, semicarbazide, and thiosemicarbazide by iron(III) in the presence of triazines

In the presence of 3-(2-pyridyl)-5,6-bis(4-phenyl-sulphonicacid)-1,2,4-triazine disodium salt (PDTS), 3-(4-(4-phenylsulphonic-acid)-2-pyridyl)-5,6-bis(4-phenylsulphonic-acid)-1,2,4-triazine trisodium salt (PPDTS), or 2,4-bis(5,6-bis(4-phenylsulphonic-acid)-1,2,4-triazin-3-yl)pyridine tetra sodium salt (BDTPS), iron(III) oxidizes hydroxylamine to nitrogen gas, semicarbazide to CO₂ and NH₃ and thiosemicarbazide to a disulfide. The corresponding iron product is the 1:3 complex of iron(II) and PDTS, PPDTS, or BDTPS. The kinetics of these reactions was studied by monitoring the iron(II) product by conventional spectrophotometry. The reaction is first order in iron(III). Kinetic evidence was obtained for the formation of 1:1:2 ternary complexes of iron(III), substrate, and sulfonated triazine. Evidence for the ternary intermediate complexes was obtained by ion-exchange studies using ⁵⁹Fe-labeled iron(III) solutions. The dissociation of the ternary complex is identified as the rate-determining step.     

Metallomacrocycles with a Difference: Macrocyclic Complexes with Exocyclic Ruthenium(II)‐Containing Domains

The templated synthesis of organic macrocycles containing rings of up to 96 atoms and three 2,2′‐bipyridine (bpy) units is described. Starting with the bpy‐centred ligands 5,5′‐bis[3‐(1,4‐dioxahept‐6‐enylphenyl)]‐2,2′‐bipyridine and 5,5′‐bis[3‐(1,4,7‐trioxadec‐9‐enylphenyl)]‐2,2′‐bipyridine, we have applied Grubbs’ methodology to couple the terminal alkene units of the coordinated ligands in [FeL₃]²⁺ complexes. Hydrogenation and demetallation of the iron(II)‐containing macrocyclic complexes results in the isolation of large organic macrocycles. The latter bind {Ru(bpy)₂} units to give macrocyclic complexes with exocyclic ruthenium(II)‐containing domains. The complex [Ru(bpy)₂(L)]²⁺ (isolated as the hexafluorophosphate salt), in which L=5,5′‐bis[3‐(1,4,7,10‐tetraoxatridec‐12‐enylphenyl)]‐2,2′‐bipyridine, undergoes intramolecular ring‐closing metathesis to yield a macrocycle which retains the exocyclic {Ru(bpy)₂} unit. The poly(ethyleneoxy) domains in the latter macrocycle readily scavenge sodium ions, as proven by single‐crystal X‐ray diffraction and atomic absorption spectroscopy data for the bulk sample. In addition to the new compounds, a series of model complexes have been fully characterized, and representative single‐crystal X‐ray structural data are presented for iron(II) and ruthenium(II) acyclic and macrocyclic species.     

A new tridentate fluorescent-colorimetric chemosensor for copper(II) ion

A new tri-imidazolium salt, tris(4-(3-(2-((8-hydroxy-9,10-dioxo-9′,10′-dihydroanthracen-1-yl)oxy)ethyl)-1H-imidazole-3′-ium-1′-yl)phenyl)amine hexafluorophosphate was prepared and characterized. Particularly, the recognition performance of the tri-imidazolium salt for cations was investigated through fluorescence and ultraviolet titrations, MS, IR spectra and ¹H NMR titrations. The results indicated that the tri-imidazolium salt can distinguish effectively copper(II) ion from other cations by the changes of spectroscopy and colour (from yellow to orange under sunlight). Furthermore, the tri-imidazolium salt was also used in detecting Cu²⁺ through employing smartphone with the computed detection limit down to 0.51 μM.     

Kinetics of Dissociation of tris-{3-(2-pyridyl)-5,6-bis(2-furyl)-1,2,4-triazine}iron(II)

The kinetics of base hydrolysis of the low-spin iron(II)-diimine complex [Fe(fertri)₃]²⁺, where fertri=3-(2-pyridyl)-5,6-bis(2-furyl)-1,2,4-triazine, as a function of hydroxide concentration, solvent composition (water; aqueous MeOH), and pressure are reported. Rate constants are also reported for dissociation of the [Fe(fertri)₃]²⁺ cation in 50–64% MeOH, determined from replacement of the fertri ligands by 1,10-phenanthroline. The reactivity of this fertri complex is compared with reactivities of a selection of other iron(II)-diimine complexes and, where possible, their ligand-sulfonated derivatives. The activation volume for base hydrolysis of [Fe(fertri)₃]²⁺ is +10.7 cm³ mol⁻¹, in 40% MeOH.     

Thermodynamic Parameters of Solvation and Complexing of Copper(II) Nitrate and Nickel(II) Nitrate in Water + Acetamide Mixtures at 298.15 K

The heats of mixing of aqueous solutions of copper(II) or nickel(II) nitrate in water + acetamide (AA) mixtures in the existing range of amide concentrations have been studied. A rise in the amide concentration enhances solvation more strongly in copper(II) salt solutions. Data are analyzed with reference to previous results on the enthalpies of transfer of the salts studied in water + formamide (FA) and water + N,N-dimethylformamide (DMF) mixtures. Electronic absorbance spectra have been recorded at a fixed electrolyte concentration for all thermochemically studied systems, and a linear correlation has been found between the enthalpy of transfer of Cu(NO₃)₂ and the optical density of the solution. The enhanced solvation of copper(II) nitrate in aqueous acetamide is due to inner-sphere interactions between the cation and acetamide; that of nickel(II) nitrate is more due to outer-sphere interactions.