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Anticyan is a highly effective antidote of cyanic acid and cyanide-containing compounds. It was created at the Institute of Pharmacology and Toxicology of AMS of Ukraine. Anticyan differs from other existing cyanide antidotes in that it possesses a tready methemoglobin-formation activity, has no hypotensive effect and is capable of direct stimulation of cyanide-inhibited tissue respiration.
UNLABELLED: The aim of the work was to assess te effect of chronic occupational exposure to organic solvents, hydrogen cyanide, and harmful physical factors (noise, vibration and electromagnetic fields) on intra- and extracellular concentration of magnesium, zinc, copper and calcium. The study converted 83 persons (25 males and 57 females), aged 20-58 years (median: 37.8 +/- 8.64), employed in the MERA PAFAL SA Factory of Measuring Equipment, Swidnica, for 0.42 +/- 34 years (median: 11.84 +/- 9.28). The subjects were divided into four groups: Group A-25 persons exposed to organic solvents; Group B-24 persons exposed to hydrogen cyanide; Group C-19 persons exposed to noise and vibration; and Group D-8 persons exposed to electromagnetic fields. Blood samples (10 ml) were collected from each person. Intra- and extracellular concentrations of magnesium, zinc, copper and calcium were estimated. CONCLUSIONS: exposure to 1) organic solvents induces depletion of calcium and zinc from the body and intracellular cumulation of magnesium; 2) to hydrogen cyanide induces depletion of intracellular zinc and intracellular cumulation of magnesium and zinc; 3) to noise and vibration induces depletion of calcium, zinc and copper and intracellular cumulation of magnesium; and 4) electromagnetic fields does not induce any significant changes in ionic concentrations.
Conditions causing cyanide-resistant respiration were studied in the yeast Candida lipolytica. This type of respiration was found when the culture growing on glucose, glycerol, hexadecane, or acetate exhuasted the substrate and passed from the logarithmic to stationary growth phase; the same phenomenon can be induced by exhaustion of phosphorus or nitrogen in the glucose medium. The yeast culture growing on lactate, ethanol, pyruvate, alpha-ketoglutarate, malate, or succinate is characterized by cyanide-resistant respiration even at the beginning of the logarithmic growth phase. The values of pH in the incubation medium have no effect on the time of manifestation of cyanide-resistant respiration.
In cerebellar granule cells, potassium cyanide (KCN) activates the NMDA receptor resulting in generation of nitric oxide and reactive oxygen species (ROS). To study the mechanism by which KCN stimulates ROS generation, the action of cyanide on the enzymatic pathways known to generate ROS were studied. The oxidant-sensitive fluorescent dye, 2,7-dichlorofluorescin was used to measure intracellular levels of nitric oxide and ROS in cerebellar granule cells. Using selective enzyme inhibitors, it was shown that both protein kinase C and phospholipase A2 are involved in KCN-stimulated generation of NO and ROS. In cells treated with indomethacin or nordihydroguairetic acid, inhibitors of cyclooxygenase (COX) and lipoxygenase (LOX) respectively, attenuated (approximately 35%) KCN-induced generation of oxidant species. When L-NAME (LG-nitro-L-arginine methyl ester) (nitric oxide synthase inhibitor, NOS) was combined with either indomethacin or nordihydroguairetic acid, generation of oxidant species was blocked by more than 80%. Pretreatment with NS398 (COX-2 inhibitor) significantly decreased ROS generation indicating the involvement of COX-2 in KCN-induced oxidant generation. Treatment with L-NAME + NS398 blocked oxidant species generation, reflecting involvement of NOS. The participation of cytochrome P450 was not evident because SKF525A did not significantly reduce KCN-induced ROS generation. Furthermore, a correlation was observed between oxidant generation and lipid peroxidation of cellular membranes (as determined by thiobarbituric acid levels). Pretreatment with inhibitors of protein kinase C, phospholipase A2 or COX, LOX, COX-2 partially blocked KCN-induced formation of thiobarbituric acid reactive substance, whereas coincubation of L-NAME with the inhibitors decreased lipid peroxidation by 60 to 90%. In cytotoxicity studies, KCN-induced cell death was partially blocked by the inhibitors and significant protection was observed when L-NAME was combined with these compounds. These findings show that activation of phospholipase A2 and subsequent metabolism of arachidonic acid by the COX-2 and LOX pathways and NOS contribute to cyanide-induced ROS production.
The preparation, X-ray crystallography and magnetic investigation of the compounds PPh4[Cr(bipy)(CN)4].2 CH3CN.H2O (1) (mononuclear), [[Cr(bipy)(CN)4]2Mn-(H2O)4].4H2O (2) (trinuclear), [[Cr(bipy)(CN)4]2Mn(H2O)2] (3) (chain) and [[Cr(bipy)(CN)4]2Mn(H2O)].H2O.CH3CN (4) (double chain) [bipy=2,2'-bipyridine; PPh4 (+)=tetraphenylphosphonium] are described herein. The [Cr(bipy)(CN)4]- unit act either as a monodentate (2) or bis-monodentate (3) ligand toward the manganese atom through one (2) or two (3) of its four cyanide groups. The manganese atom is six-coordinate with two (2) or four (3) cyanide nitrogens and four (2) or two (3) water molecules building a distorted octahedral environment. In 4, two chains of 3 are pillared through interchain Mn-N-C-Cr links which replace one of the two trans-coordinated water molecules at the manganese atom to afford a double chain structure where bis- and tris-monodenate coordination modes of [Cr(bipy)(CN)4]- coexist. The magnetic properties of 1-4 were investigated in the temperature range 1.9-300 K. A Curie law behaviour for a magnetically isolated spin quartet is observed for 1. A significant antiferromagnetic interaction between CrIII and MnII through the single cyanide bridge [J=-6.2 cm(-1), the Hamiltonian being defined as H=-J(SCr1.SMn+SCr2.SMn] occurs in 2 leading to a low-lying spin doublet which is fully populated at T <5 K. A metamagnetic behaviour is observed for 3 and 4 [the values of the critical field Hc being ca. 3000 (3) and 1500 Oe (4)] which is associated to the occurrence of weak interchain antiferromagnetic interactions between ferrimagnetic Cr2III MnII chains. The analysis of the exchange pathways in 2-4 through DFT type calculations together with the magnetic bevaviour simulation using the quantum Monte Carlo methodology provided a good understanding of their magnetic properties.
Concentrations of Na, Cl and total cyanide (simple+complex forms of cyanide) in surface waters adjacent to uncovered, outdoor sand-salt storage facilities were monitored for the calendar year 1988. Runoff of deicing salt from these unprotected sand-salt piles resulted in Cl concentrations up to 13,500 mg liter(-1) in surrounding surface waters indicating substantial leaching of road salt from sand-salt storage lots. The use of sodium hexacyanoferrate (II) as an anti-caking agent in road salt resulted in up to 200 microg liter(-1) total cyanide (CN) in surface waters adjacent to sand-salt piles. Concentrations of Na and Cl were highest during the summer months whereas the concentrations of total CN were highest during the autumn months. The observed concentrations of total CN were less than the calculated maximum concentrations based on total CN content of pure road salt indicating that sodium hexacyanoferrate(II) was being adsorbed during overland flow onto soils and/or sediments of the wetlands. A laboratory adsorption study using five soils and a road salt solution showed that the soils adsorbed from 25 to 83% of the sodium hexacyanoferrate(II) present in the soil-road salt suspensions. The percentage of sodium hexacyanoferrate(II) adsorbed on soils increased with decreasing soil pH.
Barley (Hordeum vulgare L.), oat (Avena sativa L.), and wild cane (Sorghum bicolor L.), were exposed to 15N-labeled ferrocyanide to determine whether these plant species can transport this iron cyanide complex. Plants were treated with ferrocyanide in a nutrient solution that simulated iron cyanide contaminated groundwater and soil solutions. This nutrient solution has been shown to maintain ferrocyanide speciation with minimal dissociation to free cyanide. Following treatment, all three plants showed dramatic enrichments in roots (delta 15N per thousand =1000-1500) and shoots (delta 15N per thousand =500). Barley and oat showed enrichment primarily in roots while wild cane showed a near equal enrichment in root and shoot tissues. Nitrogen-deficient barley plants treated with ferrocyanide showed a significantly greater 15N enrichment as compared to nitrogen-sufficient plants. While the results are suggestive of ferrocyanide transport by these plant species, additional study will be required to verify these results.
The mechanism of the spontaneous decomposition of sodium cyanide in aqueous solution and in the solid state was studied by ion chromatography (IC), FT-Raman spectroscopy, gas chromatography/mass spectrometry (GC/MS), and carbon-13 nuclear magnetic resonance spectroscopy (13C NMR). In the aqueous solution, gradual decomposition of the cyanide to carbonate by a displacement reaction was observed. In the solid state, sodium cyanide was found to be stable when kept in dry air, however, it decomposed by the same mechanism as that in aqueous solution under non-dry conditions.
Adsorption of both copper and cyanide ions in the absence and in the presence of their complexes at TiO2-solution interfaces was investigated. The objective of this study was to demonstrate the possibility of removing heavy metal ions, exemplified by Cu(II), from aqueous solution in the presence of a ligand, e.g., CN-. Several parameters such as pH and Cu(II) and CH- ion concentration that may affect the magnitude of copper and cyanide adsorption were studied. The equilibrium of Cu-CN speciation distribution in solution and stability constant calculations have been investigated to determine the adsorption behavior of Cu(II). Results revealed that free Cu(II) ions (in the absence of CN-) were completely separated at pH8, while the adsorption of free cyanide ions, in the absence of Cu(II), reached a maximum value of 48% at pH 7. For Cu-CN complexes, the presence of CN- in excessive amount with respect to Cu(II) retarded the adsorption of Cu(II). This is attributed to the formation of multivalent anionic cyano-copper complexes such as Cu(CN)2-(3) and Cu(CN)(3-)4.
Noncovalent complexes of cyanide-ligated cytochrome c peroxidase with horse ferricytochrome c and yeast isozyme-1 ferricytochrome c have been formed in 10 mM potassium nitrate salt solutions and studied by proton NMR spectroscopy. The chemical shifts in the ferricytochrome c spectrum induced by complex formation with low-spin, cyanide-ligated cytochrome c peroxidase are similar to the corresponding shifts induced by complex formation with resting-state cytochrome c peroxidase, found previously. As with the resting-state enzyme, the complex between yeast cytochrome c and cytochrome c peroxidase-cyanide exhibits the larger set of complex-induced shifts. Two-dimensional proton NMR spectroscopy has been used to make resonance assignments. This was necessitated due to the extensive resonance overlap between the two proteins in the hyperfine shift region, since both heme proteins in this complex are low-spin paramagnetic species. These results expand preliminary work that revealed for the first time that cytochrome c binding affected the resonances of protons in the peroxidase heme pocket [Yi, Q., Erman, J. E., & Satterlee, J. D. (1992) J. Am. Chem. Soc. 114, 7907-7909]. The pattern of cytochrome c peroxidase complex-induced shifts is largely consistent with the X-ray crystal structures of these two complexes that have recently been published.
Reaction pathways for the one- and two-electron reductions of [Fe(CN)(5)NO](2)(-) have been investigated by means of a density functional theory (DFT) approach combined with the polarized continuum model (PCM) of solvation. In addition, UV-vis spectroscopic data were obtained using ZINDO/S calculations including a point-charge model simulation of solvent effects. DFT methodologies have been used to assess the thermodynamical feasibility of protonation and cyanide-release processes for the reduced species. We conclude that [Fe(CN)(5)NO](3)(-) is a stable species in aqueous solution but may release cyanide yielding [Fe(CN)(4)NO](2)(-), consistent with experimental results. On the other hand, the [Fe(CN)(5)NO](4)(-) complex turns out to be unstable in solution, yielding the product of cyanide release, [Fe(CN)(4)NO](3)(-), and/or the protonated HNO complex. All the structural and spectroscopic (IR, UV-vis) predictions for the [Fe(CN)(5)HNO](3)(-) ion are consistent with the scarce but significant experimental evidence of its presence as an intermediate in nitrogen redox interconversion chemistry. Our computed data support an Fe(II)(LS) + NO(+) assignment for [Fe(CN)(5)NO](2)(-), an Fe(II)(LS) + NO assignment for the one-electron reduction product, but an Fe(I)(LS) + NO(+) for the one-electron product after dissociation of an axial cianide, and an Fe(II) + singlet NO(-) for the two-electron reduction species.
Cyanide-bridged molecular squares of [Fe(II)(2)Cu(II)(2)(mu-CN)(4)(dmbpy)(4)(impy)(2)](ClO(4))(4).4CH(3)OH.C(6)H(6) (1) and of [Fe(III)(2)Cu(II)(2)(mu-CN)(4)(dmbpy)(4)(impy)(2)](ClO(4))(6).4CH(3)OH.4H(2)O (2) (dmbpy = 4,4'-dimethyl-2,2'-bipyridine; impy = 2-(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxy) were prepared. In the squares of 1 and 2, the Fe(II/III) (low spin) and Cu(II) ions are alternately bridged by the cyanide groups, in which the cyanide carbon atoms coordinated to the Fe(II) ions and Cu(II) ions are coordinated by imino nitroxide. Magnetic susceptibility measurements for 1 and 2 revealed that the Cu(II) ion and imino nitroxide are ferromagnetically coupled with a fairly strong coupling constant (J(Cu-radical) > 300 K) and act as triplet species. In 1 the Cu(II)-radical moieties are magnetically separated by the Fe(II) ions. In the square of 2, dpi (Fe(III)), dsigma (Cu(II)), and ppi (imino nitroxide) spins are alternately assembled, and this situation allowed the square to have an S = 3 spin ground state. The exchange coupling constant of Fe(III) and the Cu(II)-radical moiety in 2 was estimated to be J = 4.9 cm(-1) (H = -2JSigmaS(Fe).S(Cu-radical)).
The use of 1,3,5-triaminocyclohexane (tach) as a capping ligand in generating metal-cyanide cage clusters with accessible cavities is demonstrated. The precursor complexes [(tach)M(CN)(3)] (M = Cr, Fe, Co) are synthesized by methods similar to those employed in preparing the analogous 1,4,7-triazacyclononane (tacn) complexes. Along with [(tach)Fe(CN)(3)](1)(-), the latter two species are found to adopt low-spin electron configurations. Assembly reactions between [(tach)M(CN)(3)] (M = Fe, Co) and [M'(H(2)O)(6)](2+) (M' = Ni, Co) in aqueous solution afford the clusters [(tach)(4)(H(2)O)(12)Ni(4)Co(4)(CN)(12)](8+), [(tach)(4)(H(2)O)(12)Co(8)(CN)(12)](8+), and [(tach)(4)(H(2)O)(12)Ni(4)Fe(4)(CN)(12)](8+), each possessing a cubic arrangement of eight metal ions linked through edge-spanning cyanide bridges. This geometry is stabilized by hydrogen-bonding interactions between tach and water ligands through an intervening solvate water molecule or bromide counteranion. The magnetic behavior of the Ni(4)Fe(4) cluster indicates weak ferromagnetic coupling (J = 5.5 cm(-)(1)) between the Ni(II) and Fe(III) centers, leading to an S = 6 ground state. Solutions containing [(tach)Fe(CN)(3)] and a large excess of [Ni(H(2)O)(6)](2+) instead yield a trigonal pyramidal [(tach)(H(2)O)(15)Ni(3)Fe(CN)(3)](6+) cluster, in which even weaker ferromagnetic coupling (J = 1.2 cm(-)(1)) gives rise to an S = (7)/(2) ground state. Paralleling reactions previously performed with [(Me(3)tacn)Cr(CN)(3)], [(tach)Cr(CN)(3)] reacts with [Ni(H(2)O)(6)](2+) in aqueous solution to produce [(tach)(8)Cr(8)Ni(6)(CN)(24)](12+), featuring a structure based on a cube of Cr(III) ions with each face centered by a square planar [Ni(CN)(4)](2)(-) unit. The metal-cyanide cage differs somewhat from that of the analogous Me(3)tacn-ligated cluster, however, in that it is distorted via compression along a body diagonal of the cube. Additionally, the compact tach capping ligands do not hinder access to the sizable interior cavity of the molecule, permitting host-guest chemistry. Mass spectrometry experiments indicate a 1:1 association of the intact cluster with tetrahydrofuran (THF) in aqueous solution, and a crystal structure shows the THF molecule to be suspended in the middle of the cluster cavity. Addition of THF to an aqueous solution containing [(tach)Co(CN)(3)] and [Cu(H(2)O)(6)](2+) templates the formation of a closely related cluster, [(tach)(8)(H(2)O)(6)Cu(6)Co(8)(CN)(24) superset THF](12+), in which paramagnetic Cu(II) ions with square pyramidal coordination are situated on the face-centering sites. Reactions intended to produce the cubic [(tach)(4)(H(2)O)(12)Co(8)(CN)(12)](8+) cluster frequently led to an isomeric two-dimensional framework, [(tach)(H(2)O)(3)Co(2)(CN)(3)](2+), exhibiting mer rather than fac stereochemistry at the [Co(H(2)O)(3)](2+) subunits. Attempts to assemble larger edge-bridged cubic clusters by reacting [(tach)Cr(CN)(3)] with [Ni(cyclam)](2+) (cyclam = 1,4,8,11-tetraazacyclotetradecane) complexes instead generated extended one- or two-dimensional solids. The magnetic properties of one of these solids, two-dimensional [(tach)(2)(cyclam)(3)Ni(3)Cr(2)(CN)(6)]I(2), suggest metamagnetic behavior, with ferromagnetic intralayer coupling and weak antiferromagnetic interactions between layers.
We report on quantum chemical calculations at the DFT (BP86/TZP) and ab initio (CCSD(T)/III+) levels of the title compounds. The geometries, vibrational spectra, heats of formation, and homolytic and heterolytic bond dissociation energies are given. The calculated bond length of Cu-CN is in reasonable agreement with experiment. The theoretical geometries for CuNC and the other group 11 cyanides and isocyanides which have not been measured as isolated species provide a good estimate for the exact values. The theoretical bond dissociation energies and heats of formation should be accurate with an error limit of +/-5 kcal/mol. The calculation of the vibrational spectra shows that the C-N stretching mode of the cyanides, which lies between 2170 and 2180 cm(-)(1), is IR inactive. The omega(1)(C-N) vibrations of the isocyanides are shifted by approximately 100 cm(-)(1) to lower wavenumbers. They are predicted to have a very large IR intensity. The nature of the metal-ligand interactions was investigated with the help of an energy partitioning analysis in two different ways using the charged fragments TM(+) + CN(-) (TM = transition metal) and the neutral fragments TM(*) + CN(*) as bonding partners. The calculations suggest that covalent interactions are the driving force for the formation of the TM-CN and TM-NC bonds, but the finally formed bonds are better described in terms of interactions between TM(+) and CN(-), which have between 73% and 80% electrostatic character. The contribution of the pi bonding is rather small. The lower energy of the metal cyanides than that of the isocyanides comes from the stronger electrostatic interaction between the more diffuse electron density at the carbon atom of the cyano ligand and the positively charged nucleus of the metal.
The tightly cross-linked Mo(3n)Se(3n+2) (n = 2, 3,... infinity) cluster compounds react with alkali metal cyanide or cyanide salt mixtures at temperatures of 450-675 degrees C to yield cyanide-terminated molybdenum chalcogenide clusters, [Mo6Se8(CN)6]n- (1n-) (n = 6, 7) and [Mo4Se4(CN)12](8-) (2(8-)). The process by which discrete 1(n-) clusters are excised from a CN-linked intermediate chain compound, K6Mo6Se8(CN)5 (3), was investigated, and the cubane cluster 2(7-) plays an essential role. An efficient one-step synthesis for Na8[2(8-)] is presented. These clusters are stable in basic aqueous solutions. Cyclic voltammetric (CV) measurements in basic aqueous media show multiple reversible redox waves corresponding to 1(6-/7-), 1(7-/8-), and 1(8-/9-) redox couples with half-wave potentials of E(1/2) = -0.442, -0.876, and -1.369 V, respectively, versus SHE. Half-wave potentials (E(1/2)) for the [Mo4Se4)(CN)12](6-/7-) and [Mo4Se4(CN)12](7-/8-) couples are 0.233 and -0.422 V, respectively, versus SHE. The 2(8-) compounds are K7Na[2(8-)].5H2O.MeOH, Cs7Na4[2(8-)]Cl3, Na8[2(8-)], and K4Na4[2(8-)].12H2O. The products were characterized by X-ray crystallography, cyclic voltammetry, and UV-vis spectroscopy. Reduction potentials measured by voltammetry are consistent with conditions needed for isolating reduced species on a preparative scale but are much more negative than previously reported values. Na8[1(8-)].20H(2)O was isolated by reduction of 1(7-) with Zn in aqueous NaCN solution. Reduction potentials measured in basic NaCN solutions of 2(8-) also differ widely from previous reported values.
The reaction of coenzyme B(12) (adenosylcobalamin) with cyanide has been reinvestigated in detail using spectroscopic and kinetic techniques. It has been shown that this reaction proceeds in one kinetically observable step, contradicting previous findings, with rate-determining attack of the first cyanide (k = (7.4 +/- 0.1) x 10(-3) M(-1) s(-1), 25.0 degrees C, I = 1.0 M (NaClO(4))). The activation parameters were found to be DeltaH() = 53.0 +/- 0.6 kJ mol(-1), DeltaS() = -127 +/- 3 J mol(-1) K(-1) and DeltaV() = -10.0 +/- 0.4 cm(3) mol(-1), suggesting an associative displacement mechanism. It is postulated that attack of the first cyanide occurs at the beta-(5'-deoxy-5'-adenosyl) site rather than at the alpha-dimethylbenzimidazole site.
Low-spin complexes of iron(III) chiroporphyrin, obtained from (1R)-cis-caronaldehyde acid methyl ester and pyrrole as the atropisomer, with R-imidazoles and cyanide have been studied by means of 1D and 2D (1)H NMR spectroscopy. A complete spectral assignment of resonances has been done on the basis of observed scalar, NOE, and EXSY correlations in 2D COSY and NOESY experiments. The chemical shift of beta-H pyrrole resonances have been used as a sensitive probe of electronic state of iron(III) metal ion. Cyanide anion coordination both in methanol and methylene dichloride results in formation of bis(cyanide) low-spin complexes with the rare (d(xz)(),d(yz)())(4) (d(xy)())(1) electronic ground state, revealed by pyrrole beta-H resonances at 11.12 and 10.56 ppm at 293 K, whereas imidazole and 1-methylimidazole produce the bis-ligated complexes with the (d(xy)())(2)(d(xz)(),d(yz)())(3) ground state. In case of sterically hindered imidazole derivatives, i.e., 2-methylimidazole and 1,2-dimethylimidazole, two rotational isomers have been observed at 293 K. Both electronic configurations contribute to the ground state of metal ion for the latter. The steric bulkiness of 2-methylimidazole (or 1,2-dimethylimidazole) is required to freeze a favorable configuration, even at room temperature, providing the perpendicular orientation of two imidazole planes which seems to be instrumental in the stabilization of the rare (d(xz)()d(yz)())(4)(d(xy)())(1) electronic state.
A range of complexes with general formula [MO(X)(CN)(4)](n)()(-) of W(IV), Mo(IV), Re(V), Tc(V), and Os(VI) were prepared and characterized by (13)C, (15)N, (17)O, and (99)Tc NMR, utilizing (13)C- and (15)N-enriched cyano complexes. A correlation between M-O and M-CN bond strength from X-ray crystallographic data and |(1)J((183)W-(13)C)| coupling is reported. The cyanide (HCN/CN(-)) exchange kinetics on the trans-dioxotetracyanometalate complexes and protonated/substituted ([MO(X)(CN)(4)](n)()(-)) forms thereof were studied in aqueous medium. The dioxotetracyano complexes show a trend of reactivity M(IV) > M(V) >M(VI), which is in agreement with the increase in M-L bond strength (L = O(2)(-) or CN(-)) and a dissociative activation for the cyanide and the oxygen exchange in these complexes. Rate constants (X, k(Xc)) in s(-)(1) at 298 K for the [MO(X)(CN)(4)](n)()(-) complexes are as follows for Mo(IV): O(2)(-), >0.4; OH(-), (1.7 +/- 0.1) x 10(-)(2); H(2)O, (1.5 +/- 0.1) x 10(-)(2); CN(-), (9.6 +/- 0.8) x 10(-)(3). For W(IV): O(2)(-), (4.4 +/- 0.4) x 10(-)(3); OH(-), (9.6 +/- 0.9) x 10(-)(5); H(2)O, (1.1 +/- 0.1) x 10(-)(4); CN(-), (1.1 +/- 0.1) x 10(-)(2); N(3)(-), (3.1 +/- 0.2) x 10(-)(4); F(-), (4.8 +/- 0.1) x 10(-)(5). For Tc(V): O(2)(-), (4.8 +/- 0.4) x 10(-)(3); H(2)O, <4 x 10(-)(5); NCS(-), <4 x 10(-)(5). For Re(V): O(2)(-), (3.6 +/- 0.3) x 10(-)(6) and (1.2 +/- 0.1) x 10(-)(4) for CN(-) and HCN, respectively; OH(2), <4 x 10(-)(8). For Os(VI): O(2)(-), <4 x 10(-)(9) and (1.2 +/- 0.1) x 10(-)(4) for CN(-) and HCN, respectively. The cyanide exchange kinetics were correlated with previously determined proton and oxygen exchange, spanning a kinetic domain of more than 12 orders of magnitude for the five metal centers studied.