Reactions of carbonate radical with cobalt(II) aminopolycarboxylates

Reactions of carbonate (CO ₃ ^–· ) and bicarbonate (HCO ₃ ^· ) radicals generated by photolysis of a carbonate or bicarbonate solution at pH 11.2 and 8.5, respectively, with Co(II) complexes of iminodiacetic acid (IDA) and ethylenediaminetetraacetic acid (EDTA) have been studied. The rate constants for the reactions were in the order of 10⁶–10⁷ dm³mol^–1s^–1. From the time-resolved spectroscopy of the products formed after reaction of CO _3· ^–· or HCO ₃ ^· , it is observed that CO ₃ ^–· or HCO ₃ ^· oxidize the metal center to its higher oxidation state.     

Schnelle coulometrische Mikrobestimmung einzelner Polythionate

Zusammenfassung Das neue Mikrobestimmungsverfahren beruht auf der coulometrischen Titration von S₂O₃ ^2– nach vorheriger Abbaureaktion der Polythionate mit Sulfit bzw. Cyanid. Es werden 10 ml Probelösung (S₄O₆ ^2–: 5 · 10^–5 bis 1 · 10^–3 M; S₅O₆ ^2–; 2,5 · 10^–5 bis 1· 10^–3 M; S₆O₆ ^2–: 1,66 · 10^–5 bis 1 · 10^–3 M) benötigt. Die Titrationskurve wird von einem Schreiber registriert. Die Reproduzierbarkeit der jeweiligen Einzelbestimmung liegt bei VK _p±0,1 bis ± 1,6%.

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Rapid coulometric microdetermination of individual polythionates

The method described is based on the coulometric titration of S₂O₃ ^2– after a preceding degradation of the polythionates with sulphite or cyanide. 10 ml of sample solution are required (S₄O₆ ^2–: 5× 10^–5 to 1×10^–3 M; S₅O₆ ^2– : 2.5×10^–5 to 1×10^–3 M; S₆O₆ ^2–: 1.66×10^–5 to 1×10^–3 M). The titration curve is recorded. The reproducibility of a single determination is VK _p±0.1 to ± 1.6%.

     

Spectrophotometric determination of trace amounts of cadmium and lead with iodide and Rhodamine B

Summary Highly sensitive spectrophotometric methods have been developed for determination of cadmium and lead, based on the CdI₄ ^2– or PbI₄ ^–2 anionic complexes with Rhodamine B in the presence of polyvinyl alcohol to form ion-association complexes. The molar absorptivity is 4.2×10⁵l·mole^–1·cm^–1 at 600 nm for cadmium and 5.7×10⁵l·mole^–1·cm^–1 at 610 nm for lead. The complexes have the composition [CdI₄ ^2–]·[RhB⁺]₂ and [PbI₄ ^2–]·[RhB⁺]₂ as established by Job's method of continuous variations and the molarratio method. The colour reaction selectivity is fairly good and the method can be applied for direct spectrophotometric determination of cadmium or lead in some pure metals. A species [PbI₃ ^–]·[RhB⁺] can also be formed, and extracted into toluene or a toluene/diethyl ether mixture.

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Spektrophotometriscbe Bestimmung von Spuren Cadmium und Blei mit Jodid und Rhodamin B

Zusammenfassung Hochempfindliche spektrophotometrische Methoden für die Bestimmung von Cadmium und Blei wurden entwickelt; sie beruhen auf der Reaktion von CdJ₄ ^2– bzw. PbJ₄ ^2– mit Rhodamin B in Gegenwart von Polyvinylalkohol unter Bildung von Ionenassoziat-Komplexen. Die molare Absorptivität für Cadmium beträgt 4,2×10⁵l·mol^–1·cm^–1 bei 600 nm und für Blei 5,7×10⁵l·mol^–1·cm^–1 bei 610 nm. Wie nach der Methode der kontinuierlichen Variation nach Job bzw. mittels Molarverhältnis ermittelt wurde, lautet die Formel [CdJ₄] [RhB]₂ bzw. [PbJ₄] [RhB]₂. Die Selektivität der Farbreaktion ist gut. Das Verfahren kann zur direkten spektrophotometrischen Bestimmung von Cadmium bzw. Blei in verschiedenen reinen Metallen verwendet werden. Auch eine Verbindung [PbJ₃ ^–] [RhB⁺] kann hergestellt werden, die sich mit Toluol oder mit einem Gemisch aus Toluol und Diethylether extrahieren läßt.

     

Solubility Properties of the Systems Chromium Salts–Amino Acids–Water

Solubility properties of the ternary systems of Cr(NO₃)₃–His–H₂O, Cr(NO₃)₃–Met–H₂O, and CrCl₃–His–H₂O (His—histidine, Met—methionine) have been investigated in the whole concentration range by the phase equilibrium semimicromethod, and the corresponding phase diagrams have been constructed. It was shown that the new complexes Cr(His)(NO₃)₃ · 3H₂O, Cr(His)₂(NO₃)₃ · 3H₂O, Cr(His)₃(NO₃)₃ · 3H₂O, Cr(His)Cl₃ · H₂O, Cr(His)₂Cl₃ · H₂O, and Cr(His)₃Cl₃ · H₂O are formed in the Cr(NO₃)₃/CrCl₃–His–H₂O system, while Cr(Met)(NO₃)₃ · H₂O and Cr(Met)₂(NO₃)₃ · H₂O complexes are formed in the system Cr(NO₃)₃–Met–H₂O. Under the guidance of the phase diagrams, the complexes were prepared and characterized by chemical and elemental analysis, IR spectroscopy, and thermogravimetry data. The influences of metal cations, anions and the structures of amino acids on the formation of complexes were discussed.     

Potentiometrische Cyanidbestimmung in Gegenwart von Hexacyanochromat(III)

Zusammenfassung Im Konzentrationsbereich 2 · 10^–4–3 · 10^–3 Mol/l lassen sich Cyanidionen in Gegenwart von 0,01 Mol/l [Cr(CN)₆]^3– potentiometrisch bestimmen. Als Indicatorelektrode diente eine Silberjodidmembranelektrode oder eine jodierte Silberelektrode. Zusatz von festem AgJ erhöht die Reproduzierbarkeit.

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Potentiometric determination of cyanide in presence of hexacyanochromate(III)

2×10^–4–3×10^–3 Mol/l of cyanide can be determined in presence of 0.01 Mol/l of [Cr(CN)₆]^3–. Indicator electrode is a silver iodide membrane or an iodized silver electrode. Solid AgI is added for improved reproducibility.

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Herrn Prof. H. L. Schläfer danke ich sehr für sein Interesse an dieser Arbeit.Der Deutschen Forschungsgemeinschaft danke ich für finanzielle Unterstützung.     

Oxidative homolysis of organochromium(III) macrocyclic complexes

Summary Organochromium complexes, [CrRL(H₂O)]²⁺] (L = 1,4,8,12-tetraazacyclopentadecane; R = 1°- or 2°-alkyl, or para-substituted benzyl), are oxidized to [CrRL(H₂O)]³⁺, which rapidly decomposes (k ₃ > 10² s^–1) by homolysis of the Cr-C bond. Rate constants of the oxidation of these complexes by [IrCl₆]^2– range from 2.20 × 10^–1 (R = Me) to 4.60 × 10⁵ (R = 4-MeC₆H₄CH₂)dm³ mol^–1 s^–1. A very negative reaction constant (–4.3) is found for the oxidation of para-substituted benzlchromium(III) complexes which, in conjunction with the results of product analysis, indicates a [Cr^III/R^.] type transition state.     

Chemistry of μ-hydridobis[pentacarbonylchromium(0)] species. Part III. Redox reactions with mercury(II) compounds and iodine

Summary [Cr₂(CO)₁₀(-H)]^– undergoes ready hydride substitution on reaction with HgX₂ (X = Cl, Br, I or SCN) or with iodine in acetone, yielding [Cr₂(CO)₁₀(-X)]^– complex species which can be converted quantitatively into [Cr(CO)₅X]^– anions by reactions conducted in the presence of an excess of X^–.LCr(CO)₅ and (L-L)Cr(CO)₄ complexes (L = pyridine; L-L = 1,10-phenanthroline or 2,2-bipyridine) are easily prepared by reactions performed in the presence of the L or L-L ligand, respectively.     

Kinetic Investigation of the Reaction of Octacarbonyl Dicobalt with 2,2,6,6-Tetramethylpiperidin-1-oxyl

The initial rate of carbon monoxide evolution in the reaction of Octacarbonyl dicobalt with 2,2,6,6-tetramethylpiperidin-1-oxyl free radical (TEMPO) at 15°C in n-octane solution leading to the 16e complex (TEMPO)Co(CO)₂ was found to be first order with respect to the TEMPO concentration, 0.5 order with respect to the Co₂(CO)₈ concentration, and negative 0.5 order with respect to the CO concentration. Scavenging ·Co(CO)₄ and ·Co(CO)₃ by the free radical TEMPO in the rate-determining steps are in accord with the kinetic observation. The observed rate constant is k _obs = 6.4 × 10^–5 s^–1.     

Solvent and catalyst effects on the complexation of toluene with Cr(CO)6

Summary The effect of 8 solvents on the rate as well as the yields of complexation of toluene with Cr(CO)₆ has been studied. It has been found that the intensity of boiling has a profound effect on the rate of complexation in some cases (whenn-hexanol, cyclohexanone or diglyme is used as solvent). The rates of complexation are highest in these cases, but a considerable extent of decomposition results in lower yields. Butyl acetate, dibutyl ether and decalin have been found to be the most feasible solvents. Additionally, 27 different catalysts have been tested for the complexation of toluene in decalin solution, their effect being quantified by rate constants and the isolated yields of the reaction. The rate constants have been obtained from the rate of CO evolution and vary from 6.6·10^–5 s^–1 for formic acid to 6.5·10^–4 s^–1 for ethyl acetamidomalonate. Cycloalkanones proved to be more efficient catalysts than acyclic ketones with a close boiling point. Lactones are more efficient than esters, both cyclic and acyclic ketones, and diesters, all having a similar boiling point.

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Lösungsmittel- und katalytische Effekte bei der Komplexierung von Toluol mit Cr(CO)₆

Zusammenfassung Es wurde der Effekt von 8 Lösungsmitteln auf Komplexierungsgeschwindigkeit und Ausbeute der Komplexbildung von Toluol mit Cr(CO)₆ untersucht. Dabei wurde festgestellt, daß die Intensität der Erhitzung beim Sieden in einigen Fällen einen wesentlichen Effekt auf die Komplexierungsgeschwindigkeit hat (bein-Hexanol, Cyclohexanon und Diglyme). Die Komplexierungsgeschwindigkeit ist in diesen Fällen die größte, die bereits beträchtlich einsetzende Zersetzung ergibt aber geringere Ausbeuten. Butylacetat, Dibutylether und Decalin erwiesen sich als die günstigsten Lösungsmittel. Außerdem wurden 27 verschiedene Katalysatoren für die Komplexierungsreaktion in Decalin als Lösungsmittel getestet und ihre Effizienz durch Geschwindigkeitskonstanten und isolierbare Ausbeute charakterisiert. Die Geschwindigkeitskonstanten wurden aus der Entwicklung von CO berechnet; sie liegen zwischen 6.5·10^–5 s^–1 für Ameisensäure bis zu 6.5·10^–4 s^–1 für Ethylacetamidomalonat. Cycloalkanone erwiesen sich als die besseren Katalysatoren gegenüber acyclischen Ketonen vergleichbaren Siedepunkts. Lactone sind effektvoller als Ester, cyclische sowohl als auch acyclische Ketone und Diester mit ähnlichen Siedepunkten.

     

Ruthenium-catalyzed reduction of racemic tricarbonyl(η-aryl ketone)chromium complexes using transfer hydrogenation: A simple alternative to the resolution of planar chiral organometallics

Racemic planar chiral (η⁶-aryl ketone)Cr(CO)₃ complexes (aryl ketone = 1-indanone, 1-tetralone, 4-chromanone and thiochroman-4-one) were prepared by refluxing the aryl ketone with Cr(CO)₆ in a 10:1 mixture of dibutyl ether and THF. The reductions of the organometallic ketones by transfer hydrogenation in 2-propanol containing KOH and the catalyst precursor, generated from [RuCl₂(η⁶-benzene)]₂ and (−)-ephedrine, resulted in optically active syn-(R,S)-(η⁶-aryl alcohol)Cr(CO)₃ and (R)-(η⁶-aryl ketone)Cr(CO)₃ compounds in 31-97% ee. Reduction of racemic (η⁶-thiochroman-4-one)Cr(CO)₃ with the catalyst precursor generated from (+)-norephedrine, instead of (−)-ephedrine, inverted the configuration of the products obtained. Syn-(S,R)-(η⁶-thiochroman-4-ol)Cr(CO)₃ and (S)-(η⁶-thiochroman-4-one)-Cr(CO)₃ were isolated in 49% and >95% ee, respectively. The free aryl ketones were reduced using the same conditions as their respective chromium complexes, giving aryl alcohols in high ee (>95%). Reactions of non-rigid acetophenone, propriophenone and their tricarbonylchromium complexes resulted in moderate to low ee.     

Triplettlöschung durch Chrom(III)-Komplexe

Zusammenfassung Die Löschung der Triplett-Triplett-Absorption von aromatischen Kohlenwasserstoffen und von Eosin wurde blitzlichtspektroskopisch untersucht. Für die Löschkonstanten von Chromkomplexen wurden Werte von 5,7·10⁶ bis 1,3·10⁹ lMol^–1 sec^–1 gefunden. Sie hängen von der Ionenladung des Chromkomplexes ab. Die Triplett-Triplett-Absorption von Naphthazen wird von K₃[Cr(CN)₆] nicht beeinflußt. Als Löschmechanismus wird Dipol-Quadrupol-Resonanz-Energieübertragung angenommen.

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Quenching of triplet-triplet-absorption by chromium(III) complexes

The quenching of triplet-triplet-absorption of aromatic hydrocarbons and cosine was studied by means of flash spectroscopy. Second order quenching constants of chromium complexes were found to range from 5.7·10⁶ to 1.3·10⁹mol^–1 sec^–1. The values depend on the charge of the chromium complex. Naphthacene triplet-triplet-absorption is not quenched by K₃[Cr(CN)₆]. The quenching mechanism is supposed to be a dipole-quadrupole-energy transfer.

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Résumé L'extinction de l'absorption triplet-triplet des hydrocarbures aromatiques et de l'éosine a été étudiée au moyen de la spectroscopie de flash. Les constantes d'extinction du second ordre des complexes du chrome ont été trouvées entre 5.7 10⁶ à 1.3·10⁹ l mol^–1 sec^–1. Les valeurs dépendent de la charge du complexe. L'absorption triplet-triplet du nephtacène n'est pas éteinte par K₃[Cr(CN)₆]. Le mécanisme d'extinction est sans doute un transfert d'énergie dipole-quadrupole.

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Dem Andenken von Herrn Professor Hans-Ludwig Schläfer gewidmet.

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Wir danken der Max-Kade-Stiftung für finanzielle Unterstützung.     

On the characteristics and mechanism of the radiation-induced chain reaction between sulfur dioxide and molecular oxygen in acid solutions

Characteristics of the -induced chain reaction between sulfur dioxide and molecular oxygen in perchloric and sulfuric acid media in the presence of Ce(III) ions have been studied. The concentration effects of dissolved oxygen (0.2·10^–3–9.4·10^–3 mol/dm³, sulfur dioxide (0.3·10^–1–2.0·10^–1 mol/dm³ and Ce(III) (0.2·10^–3–4.8·10^–3 mol/dm³) and dose rate (0.26·10¹⁹–1.0·10¹⁹ eV/dm³·s) on the radiation — chemical yield of oxygen consumption G(–O₂) and accumulation of sulfate G(HSO ₄ ^– ), have been investigated. The reaction proceeds with G(–O₂) reaching 10²–10³ molecule/100eV in a catalytic regime. The reaction rate in perchloric acid medium is 3–4 times lower than that in the sulfuric acid medium and depends on the SO₂, O₂ and Ce(III) concentrations, the reaction order varying from 1.0 to 0 and/or in the reverse direction. The mechanism of the process involves chain propagation with 3 stages and 3 intermediates: SO₃H, HSO₅ and Ce(IV). The catalytic effect is caused by the interaction of HSO₄ with Ce(IV) ions followed by their reduction when interacting with SO₂, yielding SO₃H radicals. Chain termination may be due to one or two of the three intermediates or due to all three particles, the kinetics depending on this. Kinetic equations describing the experimental data have been obtained.     

Spectrophotometric determination of nitrite and nitrate in doped potassium chloride crystals

Summary KCl crystals, doped in the melt with KNO₂ or KNO₃, contain both NO₂ ^– and NO₃ ^– ions. Spectrophotometric methods are described for the determination of the admixture concentration after dissolving the crystals. Nitrite is determined by colorimetry of an azo dye formed in methanol-water-HCl medium from p-nitroaniline and -naphthylamine. The absorption is proportional to the nitrite concentration in the range of 5 · 10^–6 to 5 · 10^–5 M NO₂ ^– UV absorption measurement is employed for the spectrophotometric determination of nitrate, Beer's law being obeyed between 3 · 10^–5 and 3 · 10^–4 M NO₃ ^– at 220 nm. Here, nitrite is removed by adding sulfamic acid, and correction is made for chloride. Some results on nitrite- and nitrate-doped crystals are given.

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Zusammenfassung KCl-Kristalle mit zur Schmelze zugesetztem KNO₂ oder KNO₃ enthalten sowohl NO₂ ^–- wie NO₃ ^–-Ionen. Spektrophotometrische Methoden werden beschrieben zur Bestimmung des Gehaltes dieser Zusätze nach Lösen der Kristalle. Nitrit wird bestimmt durch Colorimetrieren einer Azoverbindung aus p-Nitranilin und -Naphthylamin in einem Methylalkohol-Wasser-Salzsäure-Gemisch. Die Absorption ist dem Nitritgehalt von 5 · 10^–6 bis 5 · 10^–5 m NO₂ ^– proportional. Die UV-Absorption wird zur spektrophotometrischen Bestimmung des Nitrats verwendet. Das Beersche Gesetz ist hier zwischen 3 · 10^–5 und 3 · 10^–4 m NO₃ ^– gÜltig (bei 220 nm). Nitrit wird dabei durch Zusatz von Sulfaminsäure entfernt, und es wird fÜr Chloride korrigiert. Einige Ergebnisse an Kristallen mit Nitrit- bzw. Nitratzusatz werden angefÜhrt.

     

Synergistic extraction of cobalt(II) with oxine/decanoic acid solution mixtures in benzene and chloroform

Synergistic extraction of Co(II) with 8-hydroxyquinoline (Hq)/decanoic acid [(HR)₂] solution mixtures in benzene and chloroform was carried out at 25°C. The aqueous ionic strength and the total concentration of cobalt(II) were 0.1 (NaCl) and 1·10^–5–1·10^–3M, respectively. The synergistic effect is interpreted by the formation of the mixed ligand ion-pair complexes: [(Coq(Hq)₂(HR))⁺, R^–] and [(Coq(Hq)₂(HR)₃)⁺, R^–] in benzene and chloroform, respectively.     

The aggregation in dodecyltrimethylammonium hydroxide aqueous solutions

The aggregation of dodecyltrimethylammonium hydroxide (DTAOH) aqueous solutions has been studied by several methods. It is stepwise and four critical points were found. AtC _T=(2.51±0.10)×10^–4 mol · dm^–3 the surface excess becomes zero, atC _T=(1.300±0.041)×10^–3 mol · dm^–3 small aggregates from, which grow with concentration. AtC _T=(1.108±0.010)×10^–2 mol · dm^–3 true micelles form (CMC) and at (3.02±0.28)×10^–2 mol · dm^–3 the structure of micelles probably changes affecting their properties. The DTAOH micelles are highly ionized (=0.8) at the CMC, and decreases to reach very small values when the total concentration increases.     

Der Einfluß großer Salzkonzentrationen auf die Oxydationsreaktion von Fe(phen) 3 2+ mit Ce(IV) in Schwefelsäure

The influence of NaClO₄, NaCl and Na₂SO₄ on the oxidation of Fe(phen) ₃ ²⁺ by Ce(IV) was investigated by means of the stopped-flow method. At the concentrations range of NaClO₄ and NaCl 0.1–1.0M the rate constant values decrease from 1.03·10⁵ to 0.56·10⁵M^–1s^–1 and from 1.08·10⁵ to 0.81·10⁵M^–1s^–1 respectively.In varying concentrations of Na₂SO₄ solutions (0.05–0.35M) the rate constant values decrease from 1.05·10⁵M^–1s^–1 to 0.45·10⁵M^–1s^–1.Taking into account the negative salt effect the mechanism of the reaction progress is proposed.

     

Lewis-base properties of the HFe3(CO)9S− and Fe3(CO)9S2− cluster anions

Summary The HFe₃(CO)₉S^– and Fe₃(CO)₉S^2– anions [prepared from H₂Fe₃(CO)₉S by deprotonation] react with M(CO)₅(THF) (M=Cr or W) to form the anionic capped clusters, HFe₃(CO)₉SM(CO) ₅ ^– and Fe₃(CO)₉SM(CO) ₅ ^2– , which can be isolated as their Et₄N salts. The M-S bonds of these complexes are cleaved by ligands such as PPh₃ or MeCN. The dianionic clusters are more stable than their monoanionic analogues. Alkylation of Fe₃(CO)₉S^2– with alkyl halides followed by protonation yields HFe₃(CO)₉SR complexes, among them the first member of the series with R=Me.     

Pulse radiolysis investigations on the reactions of primary radiolytic species of water with atropine

On pulse radiolysis of N₂O saturated aqueous solutions of atropine, an optical absorption band (_max at 320 nm,e=2.81·10³ dm³·mol^–1·cm^–1) was observed, which is assigned to the product of reaction of OH radicals with the solute. This absorption decayed following second order kinetics with a rate constant of 4.5·10⁸ dm³·mol^–1·s^–1. The rate constant for the reaction of OH radicals with atropine as estimated by following the build-up kinetics is 2.7·10⁹ dm³·mol^–1·s^–1. The H atoms also reacted with this compound to produce a transient absorption band behaving similarly to the one observed in the case of reaction with OH radicals. The transient species formed in both cases is assigned to a radical derived by H atom abstraction by H/OH radicals from the parent compound. This radical was unreactive towards 2-mercaptoethanol. e _aq ^– was found to react with atropine forming a transient band with _max at 310 nm (=3.55·10³ dm³·mol^–1). Its decay was also second order with a rate constant of 1.64·10⁹ dm³·mol^–1·s^–1. The bimolecular rate constant for the reaction of e _aq ^– with atropine as estimated from the decay of e _aq ^– absorption at 720 nm is 3.9·10⁹ dm³·mol^–1·s^–1. Specific one-electron oxidizing and reducing agents (such as Cl ₂ ^– , Tl²⁺, SO ₄ ^– and (CH₃)₂COH, CO ₂ ^– , respectively) failed to oxidize or reduce this compound in aqoues solutions. The radical anion of atropine formed by its reaction with e _aq ^– was found to reduce thionine and methyl viologen with bimolecular rate constant of 3.8·10⁹ and 3.2·10⁹ dm³·mol^–1·s^–1, respectively.     

On the decrease in the ring π-current upon η6-coordination with a transition metal atom

A synthesis of [10]paracyclophane (Pc) and its organometallic complexes, Pc·Cr(CO)₃, [PcMn(CO)₃]⁺BF₄ ^–, (PcRuC₅Me₅)⁺·PF₆ ^–, (PcRhC₅Me₅)²⁺(BF₄ ^–)₂, and PcCo₄(CO)₉ has been carried out. The¹H NMR spectra of mononuclear complexes of neutral Cr and monocationic derivatives of Mn and Ru have been examined. ⁶-Coordination with a transition metal atom causes a decrease in the ring -current which is exhibited as a downfield displacement of the resonance signals from the protons of the --CH₂ groups in relation to those of free Pc. In the monocationic complexes the deshielding action of the positive charge is also added to this effect. In the¹H NMR spectrum of the cluster PcCo₄(CO)₉ the resonance signals from the --CH₂ protons are shifted upfield in relation to the Pc signals. Consequently, the concept of the ring -current decrease needs more detailed investigation for cluster systems.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1467–1470, August, 1993.     

2,5-Diphenyloxazole chromium(III) complexes

Summary Complexes of chromium(III) with 2,5-diphenyloxazole (PPO) of general formula Cr(PPO)_nX₃·m H₂O, where X=Cl^–, Br^–, I^– or NO ₃ ^su– ; n=1–3 and m=0–6, have been prepared and studied by spectroscopic and magnetic methods and by molar conductivity measurements. All the complexes seem to be hexacoordinated, generally with monodentate N-bonded ligand.