Br Anions Research Articles

Capillary electrophoresis/mass spectrometry determination of inorganic ions using an ion spray-sheath flow interface.

The determination of inorganic cations and anions by capillary electrophoresis/mass spectrometry (CE/MS) is reported using an ion spray-sheath flow interface coupling. A twelve-component synthetic mixture of cations which included the positive ions of K, Ba, Ca, Mn, Cd, Co, Pb, Cr, Ni, Zn, Ag, and Cu was loaded into the capillary column at levels ranging from 30 to 300 pg, separated by CE, and detected by indirect UV and in the full-scan (m/z 35-450) positive ion CE/MS mode using an aqueous buffer containing 30 mM creatinine and 8 mM alpha-hydroxyisobutyric acid, pH 4.8. Creatinine forms adducts with the cations which are observed in the gas phase and requires rather high (120 electron volts) declustering energy to dissociate. This produces a reduction in charge state to form the free, singly charged, inorganic cations which are observed in the mass spectra. CE/MS analysis of an aqueous acidic extract of used aircraft engine oil revealed high levels of lead as well as lower levels of chromium and nickel. CE-indirect UV analysis of a synthetic mixture containing 300 pg each of 11 inorganic ions, which included the anions of Br, Cl, NO2, NO3, S2O3, N3, SCN, SO4, SeO4, oxalate, and MoO4, is shown. The running buffer which affected this separation contained 5 mM ammonium dichromate, 10 mM ammonium acetate, and 20 mM diethylenetriamine at pH 9.3. Although indirect UV detection revealed good separation of these anions, CE/MS analysis of this mixture was complicated by interfering ion current signals from the cluster ions formed by the interaction between the additives and the analytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Gamete development in Plasmodium berghei regulated by ionic exchange mechanisms.

Ionic regulation in the induction of exflagellation of Plasmodium berghei was investigated by culturing the parasites in various isotonic media. Of the salts tested, NaHCO3 exhibited the highest activity in inducing exflagellation, whereas KHCO3 showed no activity. In the absence of HCO3-, media containing monovalent cation (Na+, K+, Cs+, Rd+, choline+, lysine+, arginine+) and Cl- also induced exflagellation, but their activities were lower than that of NaHCO3. Anions of Br- or NO3- could be substituted with Cl-, whereas other anions such as I-, NO2-, SO4(2-), SCN-, H2PO4-, or HPO4(2-) failed to induce exflagellation, as did tetramethylammonium-Cl, CaCl2, MgSO4, MgCl2 and sucrose as well. These results suggest that the induction of exflagellation requires the presence of Na+ and HCO3- or monovalent, membrane-permeable cation and Cl- in the medium. Measurements of the efflux of H[14C]O3- or Cl- indicated that these anions were released from the cells into the NaCl or the NaHCO3 medium, respectively, probably by exchange in HCO3-/Cl-. Determination of intracellular ionic concentrations by electron microscopic X-ray microanalysis of cryopreserved specimens revealed that in the NaHCO3 medium, external Na+ (and probably HCO3-) enters the gametocytes by exchange with internal Cl- (and probably H+), whereas in Cl(-)-containing media, external unspecified cation and Cl- influx by exchange, probably with H+ and HCO3-. It is therefore suggested that two separate ion exchangers, i.e., Na(+)-dependent HCO3-(in)/Cl-(out) and nonspecific monovalent-cation-dependent Cl-(in)/HCO3-(out) exchangers, are involved in the induction of gametogenesis in P. berghei.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of alkyl substituents on initiator activity in cationic polymerization of styrene with p‐methoxybenzyldialkylsulfonium salts as initiators

AbstractThe effect of alkyl substituents on cationic polymerization of styrene with p‐methoxybenzyldialkysulfonium salts was studied. p‐Methoxybenzyl tetramethylene (1), dimethyl (2), diethyl (3), dibuty (4), and diisopropylsulfonium salts (5) were synthesized by the reaction of p‐methoxybenzyl bromide with the corresponding sulfides, followed by exchange of the counter anion Br− with SbF−6. These sulfonium salts served as potent cationic thermal initiators of which activity was estimated by the bulk and solution polymerizations of styrene. The bulk polymerizations with 1–4 (0.1 mol %) for 30 min gradually proceeded at 30–50°C, but the exothermic polymerization occurred vigorously at 40–60°C. The Polymerization with 5 took place exothermically even at room temperature. Temperature‐conversion curves of the polymerizations for 30 and 5 min revealed that the activity of the sulfonium salts was in the following order: 5 > 4 > 3 > 2 ≈ 1. This order was explained by the order of the bulkiness of the alkyl substituents on the sulfur atom. Number‐average molecular weight (M̄n) of polystyrene obtained by the polymerization undergoing no exothermic process was in a range of 6600–16000, which depended on the structure of the alkyl substituents: the more bulky the substituent was, the higher M̄n was.

Magnetic interactions between electron spins on organic molecules and halogenometalate ions in TTF- and BEDT-TTF-MX4 complexes (M = Mn, Co, Cu)

The cation radical salts of TTF and BEDT-TTF with tetrahalogenometalate MX4 (M = Mn, Co, Cu; X = Cl, Br) anions having magnetic moment are prepared to study magnetic interaction between the conduction-electron spins on organic molecules and localized magnetic moments on inorganic counter anions. Magnetization and static susceptibility are measured between 2 and 300 K and electron paramagnetic resonance (EPR) spectra are observed between 4 and 300 K. A large shift of the resonance field of BEDT-TTF+ radical is found out in BEDT-TTF-MnCl4 and BEDT-TTF-CoCl4. EPR spectra characteristic of low-dimensional diffusive spin system are observed in TTF-MnCl4.

Diffusion in Saturated Soil. II: Results for Compacted Clay

The effective diffusion coefficients, D*, of three anions (Br-,Cl-, and I-) three cations Cd2+,K+, and Zn2+ diffusing in two compacted clay soils, kaolinite and Lufkin clay, are measured. The ions are contained in a simulated waste leachate. The effects of molding water content and method of compaction on the measured D* values are evaluated for kaolinite. The calculated D* values varied between 4×10-10m2/s and 2×10-9m2/s and, based on the results for chloride diffusion in kaolinite, are relatively insensitive to molding water content and compaction method. The measured D* values for Cl- and Br- in kaolinite are in excellent agreement with previous studies, but the D* values for the cations are relatively high. High D* values for the cations are attributed to nonlinear adsorption behavior at relatively high concentrations and to the possibility of chemical precipitation of the heavy metal species (Cd2+ and Zn2+). Also, D* values determined from reservoir concentrations typically are higher than D* values determined from soil concentration profiles.

Crystallographic disorder of the Re 2 unit in complexes of the type A 2Re 2X 8 (A=HP-n-Pr 3, PMePh 3; XCl or Br)

The preparation and structural characterization of three complexes containing the [Re 2X 8] 2− (X=Cl or Br) anion are described. Crystallographic parameters are as follows: for [HPnPr 3] 2Re 2Cl 8 ( 1) a=33.831(9), b=11.274(6), c=18.286(5) Å, β=91.11(1)°, V=6955(7) Å 3, Z=8, space group C2/ c; for [PMePh 3] 2Re 2Cl 8 ( 2) a=10.861(2), b=11.964(3), c=16.235(4) Å, β=93.40(2)°, V=2106(1), Z=2, space group P2 1/ n; for [PMePh 3] 2Re 2Br 8 ( 3) a=10.964(2), b=12.198(2), c=16.421(2) Å, β=93.83(1)°, V=2191(1) Å 3, Z=2, space group P2 1/ n. These complexes exhibit an unusual form of crystallographic disorder which has been previously observed in other derivatives that contain the [Re 2X 8] 2− anion. It is suggested that while this type of disorder must correlate with the positions of the cations relative to the anions in the crystal packing, and other factors, no simple analysis is likely to be adequate.

Synthesis, structure, vibrational spectra and chemical properties of the triangular molybdenum and tungsten complexes M 3(μ 3-S)(μ 2-SSe) 3X 62− (M = Mo, W; X = Cl, Br)

Salts containing M 3(μ 3-S)(μ 2-S 2) 3X 6 2− (M = Mo, W; X = Cl, Br) anions interact with SePPh 3 upon heating in acetonitrile to form SPPh 3 and M 3(μ 3-S)(μ 2-SSe) 3X 6 2−. The stereochemisty of this reaction has been studied. In the reaction of SePPh 3 with Mo 3(μ 3- 34S)(μ 2- 34S a 32S e) 3X 6 2− replacement of the equatorial sulfur atoms takes place, and 32SPPh 3 and Mo 3(μ 3- 34S)(μ 2- 34S aSe e) 3X 6 2− are produced. The structure of (PPh 3Et) 2Mo 3(μ 3-S)(μ 2-SSe) 3Cl 6 ( I) was established by X-ray diffraction analysis. The crystals of I are triclinic, space group P 1 ( a = 13.547(2), b = 13.755(2), c = 15.736(3) Å; α = 101.79(1), β = 97.71(1), γ = 110.49(1)°, Z = 2). A total of 5721 independent reflections has been collected on an automated diffractometer, and the structure was solved to R = 0.051 ( R w = 0.062). The selenium atoms are essentially in the plane of the Mo 3 triangle. The SSe distances are 2.157(5)–2.163(4) Å. Complex I is the first compound containing a SSe ligand that has been structurally characterized. IR and Raman spectra of M 3S 4Se 3X 6 2− have been studied. For Mo 3S 4Se 3Cl 6 2− an analysis of the normal vibrations has been performed. The force constant of the SSe bond in complex I is 2.3 mdyn/ Å. Heating of (Et 4N) 2Mo 3S 4Se 3Br 6 under vacuum at 450 °C gave rise to MoSSe.

A new approach to measuring pH in brines and other concentrated electrolytes

We propose an operational and theoretical approach to dealing with pH in brines and other concentrated aqueous solutions. The operational method is analogous to the standard procedure for measuring pH in dilute solutions, but uses a liquid-junction-free cell consisting of an ion specific electrode (ISE) for H + and another for a different ion, such as Cl −. The latter ISE replaces the standard reference electrode used in the usual procedure. The potential measured is proportional to pHCl = pH + pCl, or any corresponding quantity, such as pH/Na = pH − pNa, depending on the type of second ISE. The procedure also requires the separate measurement of the total concentration of the ion to which the second ISE responds, and input of these and other solution data to a geochemical modeling code (EQ3NR), which uses the Pitzer equations (Pitzer, 1973) to compute a thermodynamic model of the solution. High ionic strength standard solutions, whose compositions are calculated using the same code, are used to calibrate the liquid-junction-free cell. A pH scale convention is then used to decouple pH from pCl, pNa, pBr, etc. We investigated ISE couples pairing cations (K + and Na +) as well as anions (Br −) against H + to demonstrate the general applicability of this approach to measuring pH. The effects of these and other potentially interfering ions (Ca 2+, Mg 2+, BO 3− 3, SO 2− 4, and HCO − 3) on the various ISE couples were studied. By making a HCl measurements in sample solutions equilibrated with calcite we have used the solubility of calcite in high ionic strength solutions (determined using the Harvie et al., 1984, derived thermodynamic data consistent with the Pitzer formulation) as an independent verification of the method.

ChemInform Abstract: Lewis‐Base Adducts of Group 11 Metal(I) Compounds. Part 58. Syntheses, X‐Ray Structures, and Far IR Spectra of the Novel (CuX2(bidentate ligand))‐ (X: Cl or Br) Anion Salts of the (Cu(dpa)2)+ Cation and the Dimeric Iodide ((dpa)CuI2Cu(dpa)) (dpa: di(2‐pyridyl)amine).

AbstractReactions of Cu(I) halides in acetonitrile with di(2‐pyridyl)amine yield the ionic 1:2 adduct (I) (space group P21/c, Z=4), the ionic 1:1.5 adducts (II) (for both P21/n, Z=4), and the iodo‐bridged dimer (III) (Pcab, Z = 8) in dependence on molar ratios and the halide.

Metal voltammetry at dioleoyl lecithin (di-O-PC) coated mercury electrodes: Cd, Cu, Eu, Pb, V and Zn and the effect of electrolyte composition

The electrochemistry of Cd, Cu, Eu, Pb, Zn and V has been investigated at a dioleoyl lecithin (di-O-PC) coated mercury electrode. Techniques used were cyclic voltammetry and normal pulse voltammetry. In the capacitance minimum potential region, all electrode processes are inhibited. The initiation of the reduction of the metal ion always precedes the first reorientation peak. For these metals, the rate limiting step for reduction appears to be associated with the transport of the metal ion across the monolayer. It was found that the onset of the reduction is shifted to negative potentials by reagents which stabilise the metal ion in solution. In addition, the initiation of the reduction is rendered sharper by ions which compete for the monolayer surface (Mg 2+, NH 4 +), and is shifted to positive potentials by ions which stabilise the metal ion in the monolayer, e.g. I −. Logarithmic analysis of the normal pulse voltammetric wave shows increasing slope with increasing negative potential for the reduction of Cd(II), Eu(III), Pb(II) and V(III). The initial slope corresponds to electrostatic penetration of the ion into the monolayer whereas the increases in current at more negative potentials represent a rather sudden increase in permeability of the monolayer associated with the reorientation process. From the initial slope an apparent transfer coefficient, α a, can be estimated which corresponds to a trapezoid energy barrier for the ion transfer into the layer of the more permeable ions. The permeabilities of Cd(II) in the monolayer in different electrolytes follow the order of electrolytes; 0.01 mol dm −3 KI+0.1 mol dm −3 KC1 > 0.5 mol dm −3 KNO 3 > 0.1 mol dm −3 KCl > 0.5 mol dm −3 KBr > 0.5 mol dm −3 KCl > 0.5 mol dm −3 K 2SO 4. It is proposed that Cd(II) as the hydrated ion crosses the monolayer except in the presence of the hydrophobic anions Br − and I − which facilitate its transport. For Pb, Cd and Zn, the oxidation step is different to the reduction.

Preparation of Cu + ion-conducting glasses and mixed-anion effect in conductivity of the glasses

Cu + ion-conducting glasses were obtained in the systems CuI-Cu 2O-MoO 3 and CuI-CuBr-Cu 2MoO 4. These glasses had high ionic conductivities in the range of 10 −1–10 0 Sm −1 at room temperature. The conductivities of these glasses were increased with an increase of the cuprous halide content. The enhancement of conductivity with mixing of two anion species, I − and Br −, was observed in the system CuI-CuBr-Cu 2MoO 4. This enhancement was dominantly governed by the decrease in the activation energy with mixing of two kinds of halide anions.

Lewis-base adducts of Group 11 metal(I) compounds. Part 58. Syntheses, X-ray structures, and far-infrared spectra of the novel [CuX2(bidentate ligand)]–(X = Cl or Br) anion salts of the [Cu(dpa)2]+cation and the dimeric iodide [(dpa)Cul2Cu(dpa)][dpa = di(2-pyridyl)amine

Reaction of copper(I) halides (CuX, X = Cl, Br, or I) in acetonitrile solution with di(2 pyridyl)amine(dpa) yields 1 : 1.5 adducts with the chloride and bromide, a 1 : 1 adduct with the iodide, and a 1 : 2 adduct with the chloride. The compounds have been characterized by spectroscopic and single-crystal X-ray methods. The 1 : 1 iodide is a dimer, [(dpa)Cul2Cu(dpa)], of a type familiar with other bidentate nitrogen base ligands, but the l : 1.5 complexes are ionic, formulated as [Cu(dpa)2]+[Cu(dpa)X2]–, containing the first structurally characterized [Cu(dpa)2]+ cations and [CuX2(bidentate ligand)]– anions, while the 1 : 2 chloride is [Cu(dpa)2]+Cl–. In the [Cu(dpa)2]+ cation mean Cu–N is ca. 2.00 A, while in the [Cu(dpa)X2]– anions Cu–N is ca. 2.05 A and Cu–Cl and Cu–Br 2.369(2), 2.302(2) and 2.490(6), 2.439(6)A respectively. The dpa ligand in all cases is essentially planar. The far i.r. spectra of the anions show bands at 214 cm–1(chloride) and 160 cm–1(bromide) which can be assigned to the asymmetric stretching mode of the CuX2 unit.

Characterization of nonheme iron and reaction mechanism of bromoperoxidase in Corallina pilulifera.

The properties of the nonheme iron of bromoperoxidase from Corallina pilulifera were studied. The enzyme lost its activity when reduced with formamidine-sulfinic acid and recovered it when oxidized by air. Incubation of the enzyme with ferric or ferrous ion-chelating agents indicated that its nonheme iron was ferric. Analyses of circular dichroism and proton NMR spectra suggested that the ferric ion tightly bound to cysteine, histidine, or tyrosine residues of the enzyme. The enzyme catalyzed Br--dependent catalase reactions to yield 1 mol of O2 from 2 mol of H2O2. No O2 evolution was observed when bromination reaction of monochlorodimedone occurred. From these results, together with previous knowledge of this enzyme, it was concluded that it activated bromide anion (Br-) to bromonium cation (Br+) using one molecule of H2O2, and this Br+OH- formed at the active site then decomposed another H2O2 to yield O2 in the absence of halogen acceptors (substrate). When substrate was present in the reaction mixture, it and H2O2 competitively reacted with the reaction intermediate (Br+OH-) to give brominated products.

Brominated and brominated/chlorinated dibenzodioxins and dibenzofurans: potential environmental contaminants

Brominated and brominated/chlorinated compounds including dibenzodioxins and dibenzofurans are expected in combustion processes with bromine and chlorine sources both present. The analysis of these compounds is rather complicated because of the many congeners and the vast numbers of isomers involved. Negative chemical ionization mass spectrometry (NCI-MS) allows the selective and sensitive detection of these compounds by monitoring bromide anions (Br −, m/z 79 and 81) formed under NCI conditions. The reanalysis of strategic environmental, industrial and biological samples, previously prepared for analysis of the chlorinated analogues, should reveal whether or not the new compounds are of any environmental significance.

Synthesis, X-ray crystal structure, and reactivity of ternary complexes of crown ethers, organic π-acceptors, and salts

Benzo- and dibenzo-18-crown-6 (1) and (2) form charge-transfer complexes with tetracyanoethylene (TCNE) in chloroform with association constants of 2.6 ± 0.2 and 4.5 ± 0.4 l mol–1. In the presence of 1 equiv. of t-butylammonium perchlorate (ButNH3ClO4) a solid ternary complex of (2), TCNE, and ButNH3ClO4 is formed. Single-crystal X-ray analysis of a similar ternary complex of (2), ButNH3ClO4 and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) revealed the close proximity of the perchlorate anion and DDQ. Ternary complexes of TCNE, crown ethers (1)–(3), and salts with nucleophilic anions (Br–, Cl–, and F–) react to give the TCNE–· radical anion as proven by e.s.r. spectroscopy. In the presence of water and/or oxygen 18-crown-6 (3), TCNE, and ButNH3Br react to yield the 18-crown-6·ButNH3(NC)2CC(CN)O complex.

Solid-phase ligand substitution processes by outer-sphere anions in isomeric mixed-ligand hexamine chromium(III) complexes

The mixed-ligand complex compoundscis- andtrans-[Cr(en)2(NH2CH3)2]Br(B10H10) were synthetized. It was demonstrated by IR spectroscopy that the hydrogen atoms of the anions B10H 10 2− carrying the negative charge interact with the proton of the amino group in the coordinated amine, forming the bond system N-H-H-B. The complex salts obtained have high densities (d 20=1.55 g/cm3 and 1.47 g/cm3 for thecis andtrans isomer, respectively) and high thermal stability 230–250 °C. At 250–270 °C both thecis and thetrans compound dissociate, with simultaneous substitution of two methylamine molecules in the coordination sphere of the chromium(III) ion by the anions Br− and B10H 10 2− . The process is described by the topochemical equationf(α)=(1−α)2/3 (reaction on the interface of the phases), and is characterized by high values of the kinetic parameters: Ea=510–524 kJ/mol, logA=49.9–50.2. We found that the value ofE a for the amine substitution process in thecis compound, determined by evolved gas analysis under non-isothermal conditions, decreases by 220 kJ/mol when the heating rate is increased from 5.0 to 7.5 deg/min. This finding can be explained in that when the heating rate is increased, the intervals in which thecis- trans isomerization and ligand substitution reactions proceed come closer to one another, and finally overlap; the activation energy of the isomerization process then compensates part of the energy required for activation of the ligand substitution process.

Synthesis and crystal structure of (pipzH 2) 2Mo 2Cl 8·4H 2O (pipz = piperazine)

The title compound (pipzH 2) 2Mo 2Cl 8·4H 2O (pipz = piperazine),was isolated from the solution of (morphH) 2Mo 2Cl 6(H 2O) 2 in HCl 1:1 by addition of (pipzH 2)Cl 2. This reaction indicates the reversibility of the substitution of chloride ions in Mo 2Cl 8 4− by water molecules. (pipzH 2) 2Mo 2Cl 8·4H 2O crystallizes in the Pbca space group, with a = 15.154(2), b = 13.170(2), c = 12.208(2) Å and Z = 4. The structure was solved by the Patterson method and refined to the unweighted and weighted residuals of 0.050 and 0.048. The crystal structure is built form Mo 2Cl 8 4−, (pipzH 2) 2+ and H 2O. The MoMo distance of 2.129(3) Å is the shortest one found in all structurally-characterised Mo 2X 8 4− (X = Cl, Br) anions. Four independent MoCl distances are 2.456(3), 2.445(3), 2.463(4) and 2.455(4) Å. The (pipzH 2 2+ exists in a usual chair conformation. There is a network of hydrogen bonds of the type NH⋯Cl, NH⋯O, OH⋯Cl and OH⋯O between the ions and water molecules.

Release of aspartate and glutamate caused by chloride reduction in synaptosomal incubation media.

Release of the amino acid neurotransmitter candidates aspartate and glutamate from synaptosomes can be stimulated by reduction of [Cl-] in the incubation medium by replacement with the impermeant anions propionate and isethionate. Replacement by the permeant anion Br- is without effect on amino acid release. This release offers a biochemical method of studying the Cl-ion channel in CNS membrane.

MgATP-stimulated release of luteinizing hormone releasing hormone from isolated hypothalamic granules: evidence for a selective requirement for monovalent cations.

The purpose of this study was to characterize the kinetics and monovalent ion requirements of the MgATP-stimulated release of luteinizing hormone releasing hormone (LHRH) from isolated hypothalamic granules. LHRH granules were obtained from homogenates of hypothalami of adult male rats by differential centrifugation and then incubated in buffered media containing KCl. Under these conditions, the pH optimum for the MgATP-stimulated release of LHRH was between 7.5 and 8.0; the rate of release was linear for the first 5 min of incubation; and the magnitude of the release was a saturable function of KCl concentration. When the potassium in the incubation mixture was replaced with various monovalent cations (Li+, Na+, Cs+, choline, or tetraethylammonium), the magnitude of the MgATP-stimulated release of LHRH was inversely related to the size of the cation; release in the presence of Li+ was 12%, whereas release in the presence of tetraethylammonium was 0% of the total LHRH. When the chloride in the incubation mixture was replaced with various monovalent anions (Br-, I-, or isethionate), the magnitude of the MgATP-stimulated release of LHRH was not related to the size of the anion. Moreover, inclusion of anion transport inhibitors in the incubation mixture did not affect LHRH release, suggesting that anion transport is not required for the MgATP-stimulated release of LHRH. In summary, we suggest that the MgATP-stimulated release of LHRH from isolated hypothalamic granules involves an enzymatic event and that this release process does not have a selective requirement for monovalent anions, but has a selective requirement for monovalent cations.

The kinetics and stereochemistry of spontaneous aquation of trans-[Co(en) 2N 3(Me 2SO)] 2+, [Co(en) 2N 3(DMF)] 2+,[Co(en) 2N 3Br] + and [Co(en) 2N 3Cl] +

The syntheses of the new trans-solvento complexes trans-[Co(en) 2(sol)N 3](ClO 4) 2(sol = Me 2SO,Me 2N·CHO (DMF)) are described. Also given a reliable preparative procedures for the known trans-[Co(en) 2N 3X]ClO 4 (X = Br, Cl). The kinetics and steric course of spontaneous aquation at 25°C have been determined for the four trans-azido ions: X = Me 2SO, k s = (6.0 ± 0.3) 10 −3 s −1, 92 ± 1% trans product; X = DMF, k s = (2.96 ± 0.16) 10 −4 s −1, 92±2% trans; X = Br, k s = (9.2 ± 0.2) 10 −4 s 1̄, 91 ± 1% trans; X = Cl, k s = (2.48 ± 0.05) 10 −4 s −1, 91 ± 2% trans. The reactions are not retentive as reported previously (X = Br, Cl). A common stereochemistry (92% trans[Co(en) 2N 3(OH 2) 2+ pertains for both anionic (Br −, Cl −) and neutral (Me 2SO, DMF) leaving groups. The aquation mechanism is discussed.