Formation Of Cationic Complexes Research Articles

The Interpretation of Thermodynamic Data for the Complex Formation of Cations with Crown Ethers and Cryptands. Part I: The Reaction Entropy

The complex formation between cationsand crown ethers or cryptands is influenced byenthalpic and entropic contributions. The solvation ofcations and ligands plays an important role andinfluences both thermodynamic parameters. Changes insolvation and their influence upon the reactionentropy is discussed in detail for some selectedreactions in different solvents. Other contributionse.g., from the deformation of the ligands areeliminated. Thus, the results obtained are valid forall complexation reactions between cations andmacrocyclic and macrobicyclic ligands.

Synthesis of Configurationally Stable, Optically Active Organocobalt Compounds

The transmetalation reaction between a series of ortho-lithiated tertiary amine derivatives (N∧C−Li) and [(η5-C5H5)CoI2]2 affords a series of cobaltacyclic compounds of the general form (η5-C5H5)Co(C∧N)I, in which the cobalt center is in a pseudotetrahedral environment. With optically active lithiated compounds, such as those obtained from (R)- or (S)-1-(dimethylamino)-1-phenylethane, the reaction forms a mixture of two diastereoisomers (RC,RCo)-12a, (RC,SCo)-12a‘ and (SC,RCo)-12b, (SC,SCo)-12b‘, respectively, of which the isomers 12a and 12b‘ are predominant, as they are formed with a de of 90%. 1H NMR studies indicate that the compounds are configurationally stable at the cobalt center. Reaction of these species with neutral ligands such as phosphines, phosphites, or isocyanides led to the formation of cationic complexes via substitution of the iodide ligand, this reaction occurring mainly with retention of configuration for the optically active species.

Synthesis, Structure, and Ion Selective Complexation of Trans and Cis Isomers of Photochromic Dithia-18-crown-6 Ethers

Photochromic styryl dyes containing benzodithia-18-crown-6 and N-substituted benzothiazolium moieties are synthesized and characterized spectroscopically and, for a specific case, by X-ray crystallography. The effects of the N-substituent and of sulfur atom substitution in the crown ether cavity on metal cation complex formation and on photochromism due to reversible trans−cis photoisomerization are evaluated. High selectivities for heavy metal ions, such as Ag+ and Hg2+, are observed, in contrast to the benzo-18-crown-6 dyes which selectively bind alkali and alkali earth cations. Relative complex formation stability constants, determined spectrophotometrically, are converted to absolute values by polarographic measurements. The stability constant for Hg2+ complex formation by the trans dye is enhanced 47-fold upon substitution of the 4-butylsulfonate group for methyl at the nitrogen of the benzothiazolium moiety. Photoisomerization to the cis dye is accompanied by a further 11-fold stability constant increase and by spectral changes that are consistent with formation of an ion-“capped” complex, involving intramolecular coordination of the sulfonate anion to Hg2+. Addition of a large excess of Mg2+ ions disrupts this intramolecular coordination bond without displacing the Hg2+ ion from the dithiacrown ether cavity.

Synthesis and characterization of Cp ∗Rh (III) and Ir (III) polypyridyl complexes: : fluxional behaviour of Rh (III) complexes and molecular structure of [Cp∗Rh (Ph-terpy)Cl]BF4 complex (Cp∗=η 5− (C5Me5))

Reaction of [Cp ∗M( μ-Cl)Cl] 2 (Cp ∗= η 5- (C 5Me 5), MRh, Ir) with 4′-phenyl-2,2′: 6′, 2″ terpyridine (Ph-terpy), L 1 and 1,4-bis (2,2′: 6′, 2″-terpyridin-4′-yl)benzene (diterpy), L 2 results in the formation of cationic complexes by the cleavage of halide bridge. These complexes, [Cp ∗RhL 1Cl]BF 4, (1), [ (Cp ∗RhCl) 2L 2] (BF 4) 2, (2), [Cp ∗IrL 1Cl]BF 4, (3) and [ (Cp ∗IrCl) 2L 2] (BF 4) 2, (4) are characterised by various spectral methods. Ph-terpy coordinates the metal ion in a bidentate fashion to form mononuclear complexes while diterpy bridges two metal ions to form dinuclear complexes. Complex (1) is crystallographically characterised. In solution Rh (III) complexes show fluxional behavior.

Synthesis and characterization of novel dinuclear and cationic cyclobutadiene platinum complexes

Reactions of the cyclobutadiene platinum complexes [PtCl2(C4R4)] (R=Me 1a, R=Et 1b) with diphosphines Ph2P⋂PPh2 (⋂=–CC– (dppa), –CH2– (dppm), –(CH2)2– (dppe), –(CH2)3– (dppp), –(CH2)4– (dppb)) in a 2:1 molar ratio result in formation of novel binuclear cyclobutadiene platinum complexes [{PtCl2(C4R4)}2(μ-Ph2P⋂PPh2)] (R=Me 2, Et 3). In contrast, reactions in equimolar ratio lead to formation of cationic complexes with dppe, dppp and dppb [PtCl(C4R4){Ph2P(CH2)nPPh2}]Cl (n=2–4, R=Me 5, Et 6). Complexes 2, 3 and 5, 6 were fully characterized by microanalysis and by NMR and IR spectroscopies. Structural characterization of [{PtCl2(C4Me4)}2(μ-Ph2PCH2PPh2)] (2b) reveals a piano-stool coordination at each platinum center defined by the η4-C4Me4 ligand, two Cl atoms and one P atom. The P–C–P angle of 131.0(4)° is larger than that expected for tetrahedral geometry. The X-ray structure of [PtCl(C4Me4){Ph2P(CH2)3PPh2}]Cl·CH2Cl2 (5b·CH2Cl2) reveals a Pt atom coordinated by the η4-C4Me4 ligand, chloride and the two phosphorus donors in a piano-stool conformation. In the solid state, these cations are arranged to form channels with a diameter of 13.8 Å in which solvent molecules (CH2Cl2) are embedded.

Thermochemical investigations of the systems useful for lithium battery construction

Abstract Solution enthalpies of LiClO 4 in 1,2-dimethoxyethane + γ-butyrolactone (1,2-DME + γBL) mixtures and of LiClO 4 , NaI and N,N-dimethylacetamide in 1,2-DME + propylene carbonate (PC) mixtures have been measured. The molar enthalpies of solution, Δ sol H m of the examined electrolytes as a function of the mixed solvent composition exhibit a distinct minimum within the range of high 1,2-DME content, similar to those observed earlier for LiBF 4 and LiPF 6 solutions in 1,2-DME + γ-BL mixtures while the dissolution enthalpy of DMA runs monotonously within the same range of the mixed solvent compositions. The presence of the Δ sol H m minimum of the salts is explained as a resultant of energetic effects of interactions in the solution, connected with the ionic association of the salt, the 1,2-DME + cation complex formation and changes in a composition of the ionic solvation shells

Isolation of dimeric nonactic acid from the nonactin‐producing Streptomyces spec. JA 5909‐1

AbstractThe formation of possible intermediates of nonactin (I) biosynthesis by Streptomyces spec. JA 5909‐1 was investigated. In addition to monomer nonactic acid (II), the dimeric nonactic acid (III) was isolated suggesting that III could be an intermediate of nonactin biosynthesis. The structure of III was settled by electrospray mass‐spectrometry and high‐field FT‐NMR methods. III displays no antibacterial and antifungal activities supporting the view that cation complex formation by nactin‐type antibiotics requires the entire macrotetrolide ring.

Cation-complexation-induced aggregation and specific ion conduction of lipophilic crowned azobenzenes

Lipophilic azobenzene derivatives incorporating a monoazacrown or oligooxyethylene moiety were employed as a component of ion-conducting composite films containing a polyester elastomer and an alkali metal (Li+, Na+, K−) perchlorate. Composite films of monoaza-15-crown-5-containing azobenzene1 exhibited ionic conductivities following the order of Na > Li > K, reflecting the cation-binding selectivity of the 15-crown-5 ring. The ion-conducting behavior of composite films of1 is quite different from that of composite films containing a 1 : 1 mixture of an azobenzene derivative without any crown moiety andN-phenyl-monoaza-15-crown-5 (ionic conductivity order of Li > Na > K >). It was suggested that cation and anion migration is predominant in the LiClO4 and NaClO4 systems, respectively. The specific ion conduction can be attributed to ordered aggregation of1 induced by cation complex formation of its crown moiety. Azobenzene derivatives incorporating a monoaza-12-crown-4, monaza-18-crown-6, or oligooxyethylene moiety cannot afford such aggregate formation and specific ion-conduction as is seen in the1 system.

Cationic lead(II) halide complexes in molten alkali-metal nitrate. Part 2.—A thermodynamic investigation of the chloride, bromide and iodide systems

The complex formation between lead (II) ions and chloride, bromide and iodide ions in molten equimolar (K, Na) NO3 has been studied. The systems were investigated at four temperatures between 240 and 300 °C. The iodide system was only studied at one temperature, since I– is oxidized to I2 in melts rich in Pb(NO3)2. Halide-ion activities were measured in the systems (K+, Na+, Pb2+)–(NO–3, X–), X–= Cl–, Br– and I–, by means of Ag/AgX electrodes. The formation of PbX2, PbX+ and Pb2X3+ was observed. Special interest was focused on the formation of cationic complexes with anions as coordination centres. The thermodynamic parameters ΔH°mn and ΔS°mn have been evaluated for the chloride and bromide systems. The results are : ΔH°11=– 7.9 kJ mol–1, ΔS°11= 26.3 J K–1mol–1 for Pb2++ Cl –→ PbCl+; ΔH°11=–4.6 kJ mol–1, ΔS°11= 35.2 J K–1 mol–1 for Pb2++ Br–→ PbBr+; ΔH°21= 1.5 kJ mol–1, ΔS°21= 16.1 J K–1 mol–1 for PbCl++ Pb2+→ Pb2Cl3+; ΔH°21=–7.1 kJ mol–1, ΔS°21= 1.9 J K–1 mol–1 for PbBr++ Pb2+→ Pb2Br3+. The parameters are compared with previous literature data and recent results obtained from the lead (II) fluoride system in (K, Na)NO3(l).

Cyclopentadienyliron complexes with PS ligands; Synthesis and electrochemical behaviour

Reactions of [η-C 5H 5Fe(CO) 2THF] +PF 6 − with the PS neutral ligands L = SPMe 3, SPPh 3, SP(OEt) 3, SP(OPh) 3 and (S)PEt 2P(S)Et 2, lead to the formation of cationic complexes [η-C 5H 5Fe(CO) 2L] +PF 6 −, which were characterized by IR and NMR spectra. The electrochemical behaviour of these complexes has been studied in THF solution, using cyclic voltammetry and coulometry. According to the results obtained, the products of the one-electron reduction are labile and the reduced species lose the ligand L. The oxidation of the dimer [η-C 5H 5Fe(CO) 2] 2 in the presence of the ligands, indicates that electrochemical synthesis of the complexes [η-C 5H 5Fe(CO) 2L] +PF 6 − is possible.

Synthesis of cationic molybdenum and cobalt diene complexes from neutral allyl compounds by ligand exchange in a strong protic acid

The allyl ligand in neutral molybdenum and cobalt complexes is readily exchanged by dienes in the presence of a strong protic acid with the formation of cationic complexes. This exchange is facilitated by an increase in the basicity of the starting compounds.

Platinum group metal complexes of bis(2-(diphenylphosphino)ethyl benzylamine and bis(2-(diphenylarsino)ethyl)benzylamine

Rh(I), Ir(I), Pd(II) and Pt(II) metal complexes of bis(2-diphenylphosphino)ethyl)benzylamine(DPBA) and bis(2-diphenylarsino)ethyl)benzylamine (DABA) have been synthesized using various starting materials. Reaction of RhCl(CO)(AsPh 3) 2 with DPBA or DABA in methanol resulted in the formation of cationic complexes of the composition, [Rh(CO)(L)]Cl (L = DPBA or DABA). Interaction of [IrCl(COD)] 2 with DPBA in benzene resulted in the formation of a neutral complex [IrCl(DPBA)]. Reaction of [PdCl 2(COD)] with the ligand DPBA in benzene resulted in a cationic complex of the composition [PdCl(DPBA)]Cl. Interaction of [PdCl(DPBA)]BPh 4 with SnCl 2 gave the complex [Pd(SnCl 3)(DPBA)]BPh 4. The ligands DPBA and DABA react with PtCl 2(COD) in acetone to give neutral, Pt(II) complexes of the type, [PtCl 2L] (L = DPBA or DABA). All the complexes were fully characterized by elemental analysis, conductivity measurements, IR and far-IR and 31P{ 1H} NMR spectral data.

Mass-spectrometric study of the formation of cationic complexes of Fe, Co, Ni, Cr, Mn, Rh, Pd, Nd, Pr, Ga, In, and Tl with phenol-containing crown compounds in the gas phase

1. It has been shown by mass spectrometry that 21-methoxy-19-methyl-3,6,9,12,15-pentaoxabicyclo[15.3.1]heneicosa-1(21),17,19-triene and its 21-hydroxylate react in the gas phase with cations containing atoms of Fe, Co, Ni, Cr, Mn, Rh, Nd, Pr, Ga, In, and Tl with the formation of ions havig new metal-macrocycle bonds. A characteristic feature of the 21-hydroxy derivative is the formation of σ-bonded complexes between the metal and the oxygen of the macrocycle. 2. The reactivity of the ions (acac)2M+ with respect to the macrocycles varies in the order M=Co > Fe > Cr > Pr, Ga, the relative yield of metal-containing ions with new metalmacrocycle bonds being higher for the methoxy-derivative than for the hydroxy analog.

Mass spectrometric study of 4,4-disubstituted 1-alkylidene-2,5-cyclohexadienes and their ion-molecule reactions with transition metal ions in the gas phase

1. The most general pathway for the decomposition of the molecular ions of 4,4-disubstituted 1-alkylidene-2,5-cyclohexadienes is the loss of the substituent at the geminal unit. The facility of this process is a function of the stability of the group eliminated. 2. The formation of cationic rhodium complexes containing alkylidenecyclohexadiene and alkylidenecyclohexadienyl ligands is possible in the gas phase as a result of intramolecular dissociation and ion-molecule reactions. The formation of cationic complexes also occurs as a result of the reaction of benzene derivatives with acacRh(CO)+n ions. 3. The donor capacity of 4,4-disubstituted 1-alkylidene-2,5-cyclohexadienes in reactions with acacRh(CO)+n ions is comparable with the donor capacity of their aromatic isomers.

Theoretical study on the nature of the interaction between crown ethers and alkali cations : Relation of interaction energy and ion selectivity

Interaction energies between crown ethers and cations are discussed on the basis of ab-initio MO calculations of 12-crown-4, 18-crown-6, and their cation complexes. The field in cavities of these cyclic ethers are qualitatively discussed by use of the electrostatic potential calculated. The potential suggests that the relation between a hole size of crown ether and an ion radius does not always decide the selective complex formation with the special ion. The electrostatic interaction between Ione pair orbitals of crown ether and cation does not occupy the dominant part of the stabilization energy in complex formation. The charge transfer interaction from crown ether to cation also contributes to the formation of cation complex of crown ether.

Soil Adsorption of Cadmium From Solutions Containing Organic Ligands

AbstractThe adsorption of cadmium (Cd) from aqueous solutions containing acetate (Ac), oxalate (Ox), nitrilotriacetate (NTA) and ethylenediaminetetraacetate (EDTA) onto three soils from the northeastern United States was investigated. Experimental parameters were adjusted so that, under typical field pH conditions, roughly half of the soluble Cd was present as Cd2+ while the other half, depending on the system, existed as Cd2+, CdAc+, CdOx0, CdNTA−, or CdEDTA2−, Organic complexation reduced, or had little perceptible effect on, Cd adsorption when compared to the unbound Cd system. In general, the ability to reduce Cd retention followed the trend: EDTA > NTA > Ox ≈ Ac. Since the strength of the Cd‐ligand stability constants follows the same order, it suggests that competition for the metal ion between the soil exchange sites and the added organic ligands is important in explaining the observed behavior. Despite the formation of cationic complexes (CdAc+), the presence of Ac interfered with Cd uptake under acidic conditions. This was apparently due to competitive adsorption of the free un‐ionized acetate species on the soil surface. The ability of organic complexants to influence Cd adsorption decreased with increasing suspension acidity because of preferential binding of the ligands to metals (Fe3+ and Al3+) released by the acid‐catalyzed dissolution of soil components. The coexistence of soluble metal chelators with heavy metals in a land‐applied waste may increase the mobility of the metals in the soil, the effect being more pronounced in neutral or alkaline soils and for ligands that form stable, nonadsorbing complexes with the metals.

Gold(I) complexes of unidentate and bidentate phosphorus-, arsenic-, antimony-, and sulphur-donor ligands

Complexes of gold(I) with a variety of unidentate and potentially chelating P-, As-, Sb-, and S-donor ligands have been characterised by analysis, 1H n.m.r., i.r., and u.v.–visible spectroscopy, and electrical conductivity. In the majority of cases, the gold atom is two co-ordinate, [AuX(L)] or [XAu(L′–L′)AuX](L = unidentate ligand, L′–L′= bidentate ligand, X = Cl, Br, or SCN), but a few examples of probable three-co-ordination have been found, [AuXL2] or [AuX(L′–L′)]. With bidentate ligands, inflexibility of the backbone seems to be the key factor in promoting chelation. The ease of formation of cationic complexes [AuL2]+ is shown to depend on the polarity of the solvent.

Dissimilarity between hypertensives: VA study vs. general population: Michael H. Alderman, Cornell University Medical College, New York, New York, U.S.A.; Kathryn F. Miller

Reactions of 2-thiosemicarbazido-1,4-naphthoquinone (NQTSC) with iron (II), iron (III), cobalt (II) and copper (II) chloride yield different complexes depending on the synthetic conditions. Under acidic medium, thionato coordination is favored with the formation of cationic complexes (A-1 to A-4) while neutral (B-1, B-3 and B-4) and cationic (B-2) complexes are isolated with thiolato binding under basic conditions. IR spectral data indicates that NQTSC acts as both a neutral and a mono-anionic tridentate ligand, bonding through thione, thiol or both as observed in the case of iron (III) and cobalt (III) complexes. The magnetic and Mössbauer measurements of iron (II) complexes reveal the presence of an unusual (S = 1) spin state possessing small zero-field splitting (ZFS). Reaction of NQTSC with iron (III) chloride results in the stabilization of the spin-triplet state (S = 3/2) with negligible contribution from ZFS components while cobalt complexes exhibit different magnetic properties displaying diamagnetic (A-3) cobalt (III) and low-spin cobalt (II) states (B-3). Evaluation of ESR covalency parameters for A-4 and B-4 indicates considerable delocalization of the unpaired electron present in the dx2-y2 ground state of the tetragonally distorted octahedral geometry over the entire chelate rings formed by the NQTSC ligands. Electrochemical behavior of the complexes exhibit mostly metal-centered redox changes with the iron (III) complexes having a reversible Fe(III)/Fe(II) couple at relatively positive potentials while the copper (II) compounds display quasi-reversible Cu(II)/Cu(I) as well as Cu(III)/Cu(II) redox processes. Thiolato binding probably exerts a pronounced effect on the oxidation processes while thionato coordination seems to influence reduction steps in these complexes.

Studies of exchange equilibria of palladium(II) tertiary phosphine complexes

The reactions of tertiary phosphine complexes of Pd(II) with phosphine !igand: have been investigated by NMR and conductivity measurements. Depending on the nature of the phosphine ligand either ligand exchange or the formation of cationic complexes can occur. Relative equilibrium constants for these reactions have been obtained. NMR line broadening experiments have enabled the relative rates of ligand exchange between the neutral and cationic complexes and between the cationic complex and free ligand to be obtained. A mechanism for the former process is suggested. The equilibrium constant data suggest that optimum stability for the complexes is achieved with ligands of intermediate donor ability. The significance of this observation is discusssed.

Syntheses et isomerisation de complexes de la serie des derives halocarbonyle due fer: [FeX(CO) 5− nL n] +, FeX 2(CO) 4− nL n et [FeX 3(CO) 3] - (L = PMe 3; n = 1, 2, 3; X = Cl, Br, I)

The synthesis of a number of neutral, cationic and anionic halocarbonyl complexes of iron having the formula [FeX m (CO) 6− m− n L n ] 2− m is described. The determination of their molecular configuration by infrared, NMR and dipole moment measurements allowed the study of several of their photochemical isomerization reactions, the mechanism of these reactions is explained in some cases by the intermediary formation of cationic complexes.