Zum Mechanismus des thermischen Abbaus von Ammonium- und Ammin-Chlorokomplexen des Rutheniums,Rhodiums, Palladiums und Platins

On the Mechanism of the Thermal Decomposition of Ammonium and Ammin Chloro Complexes of Ruthenium, Rhodium, Palladium and Platinum The thermolysis of noble metal compounds was investigated by a combination of independent physical (DTA/TG, high-temperature Guinier-Simon-technique) and preparative methods, characterization of the educts, intermediats and products by Guinier X-ray patterns and IR spectroscopy:

• (a) (NH₄)₂[PtCl₆], (NH₄)₂[PtCl₄], [Pt(NH₃)₄][PtCl₄], [Pt(NH₃)₄]Cl₂, and trans-[Pt(NH₃)₂Cl₂];
• (b) (NH₄)₂[PdCl₄], [Pd(NH₃)₄]Cl₂, trans-[Pd(NH₃)₂Cl₂], and [Pd(NH₃)₄][PdCl₄];
• (c) (NH₄)₂[RhCl₅(H₂O)], (NH₄)₃[Rh₂Cl₉], K₂[RhCl₅(H₂O)], and K₂[RhCl₅(NH₃)];
• (d) (NH₄)₂[RuCl₅(NH₃)] and (NH₄)₄[Ru₂Cl₁₀O]

. The most important step of the mechanism of the thermal decomposition is the ?internal”? redox reaction between the noble metal cation and the nitrogen atom of the ammine ligand.     

Thermal studies on oxalate complexes. III. Complexes of cobalt(III) and cobalt(II)

The decomposition of K₂[Co(C₂O₄)₂] and K₃[Co(C₂O₄)₃] has been studied using TG. In the case of the latter compound, the first step involves the rupture of all the oxalates and one of the resultant carbonates to liberate CO₂ and three molecules of CO. Subsequent steps involve the loss of CO₂. In the case of K₂[Co(C₂O₄)₂], four decomposition reactions are observed. The first involves the loss of only CO. Subsequent steps involve loss of CO₂, CO₂ and CO, and CO₂, respectively. Basic carbonates appear to be the intermediate products. Kinetic parameters are presented for most of the reactions.     

Strukturchemische Verwandtschaft von Kaliumhexahydroxoscandat(III), K3[Sc(OH)6] mit den isotypen Hydroxometallaten Rb3[Sc(OH)6], K3[Cr(OH)6] und Rb3[Cr(OH)6]

Structural Relationship of Potassium Hexahydroxoscandate(III), K₃[Sc(OH)₆] with the Isotypic Hydroxometallates Rb₃[Sc(OH)₆], K₃[Cr(OH)₆], and Rb₃[Cr(OH)₆] Ternary hydroxides M}M^III(OH)₆{ with M^I ? K, Rb and M^III ? Sc, Cr were obtained in the same way as K₃[Cr(OH)₆] [1] from alkali metal amides and d-metal nitrates by a comproportionation reaction of amide and nitrate ions in supercritical ammonia to elementary nitrogen and hydroxide ions at 523 K and 3 ≤ p(NH₃) ≤ 6 kbar within 1 to 3 months. Their structures were determined by single crystal x-ray methods inclusive the positions of the hydrogen atoms. The ratio of size of r(M^I)/r(M^III) is related to the symmetry of these hydroxometallates. Structural relationships between K₃[Sc(OH)₆] and Rb₃[Sc(OH)₆], K₃(Cr(OH)₆], Rb₃[Cr(OH)₆]) and K₄[CdCl₆] [4] are discussed.     

Synthesis of nanosize Co-Rh systems and study of their properties

Precursor compounds [Co(NH₃)₆][Rh(NO₂)₆] and [Co(NH₃)₆][Co(NO₂)₆], solid solutions [Co(NH₃)₆] [Rh(NO₂)₆]_1−x [Co(NO₂)₆] _x , and solid solutions Na₃[Rh_1−x Co _x (NO₂)₆] were synthesized and studied by IR spectroscopy and elemental, X-ray phase, X-ray diffraction, and thermogravimetric analyses. X-ray phase analysis was employed to examine products of thermal decomposition of precursors in the atmospheres of hydrogen and helium. Catalysts with a Co-Rh active system, supported by ZrO₂, were prepared and tested in the reaction of steam conversion of ethanol.     

Cyclohexylethynyl complexes of CoII and FeII

This paper deals with the synthesis of six σ-cyclohexylethynyl complexes of Co^II and Fe^II and their characterization by chemical analysis, infrared and ¹H NMR spectra, and magnetic measurements. Four of them are six-coordinate complexes, unsubstituted or substituted, namely K₄[M(C≡C—C₆H₁₁)₆] nNH₃(M = Co, n = 2; M = Fe, n = 0), K₂[Co(C≡C₆H₁₁)₄(NH₃)₂] and K₄[Fe(CN)₄-(C≡C—C₆H₁₁)₂]. Two are four-coordinate complexes of formula [(Ph₃P)₂M-(C≡C₆H₁₁)₂] (M = Co, Fe). All are low-spin complexes, the magnetic moment for the six-coordinate Co(II) complexes, measured at various temperatures, being intermediate between low- and high-spin values.     

Tetraazidodiammincobaltate(III): Cis-[Co(N3)4(NH3)2]− und [Co(N3)4en]−

Tetra-azidodiamminecobaltates(III): cis-[Co(N₃)₄(NH₃)₂]^? and [Co(N₃)₄en]^? The preparation and the properties of complexes containing the anions cis-[Co(N₃)₄(NH₃)₂]^? and [Co(N₃)₄en]^? are described. The compounds [Co(NH₃)₆][Co(N₃)₄(NH₃)₂ · H₂O], [Co(N₃)₂(NH₃)₄][Co(N₃)₄(NH₃)₂], [As(C₆H₅)₄][Co(N₃)₄en], cis- and trans-[Co(N₃)₂en₂][Co(N₃)₄en] have been isolated.     

Rubidiumhexaamidolanthanat und -neodymat,Rb3[La(NH2)6] und Rb3[Nd(NH2)6]; Strukturverwandtschaft zu K3[Cr(OH6)] und K4CdCl6

Rubidium Hexaamidolanthanate and -neodymate, Rb₃[La(NH₂)₆] and Rb₃[Nd(NH₂)₆]; Compounds. Structurally Related to K₃[Cr(OH)₆] and K₄CdCl₆ Colourless Rb₃[La(NH₂)₆] (a = 12.298(4) Å, c = 13.759(2) Å, N = 6, R3 c) and pale blue Rb₃[Nd(NH₂)₆] (a = 12.199(6) Å, c = 13.626(4) Å, N = 6, R32) have been prepared by the reaction of the corresponding metals (Rb: La resp. Nd = 3:1) with NH₃(P(NH₃) = 4–4.5 kbar) at 300°C. Single crystal x-ray methods gave their structures. It is shown by space group relations that these compounds are structurally related to one another and to further ternary amides as well as to K₃[Cr(OH)₆] and K₄CdCl₆.     

Determination of the structural formula of sodium tris-carbonatocobaltate(III), Na<Subscript>3</Subscript>[Co(CO<Subscript>3</Subscript>)<Subscript>3</Subscript>]·3H<Subscript>2</Subscript>O by thermogravimetry

The existence of an inner sphere water in sodium tris-carbonatocobaltate(III) prepared by the Bauer and Drinkard method was confirmed by thermogravimetry, which led to its formulation as sodium aquo-tris-carbonatocobaltate(III) dihydrate, Na₃[Co(H₂O)(CO₃)₃]·2H₂O. Hydrolytic study on 4-nitrophenylphosphate promoted by [Co(tn)₃]³⁺ afforded corborating evidence for the existence of inner sphere water in the complex leading to its formulation as [Co(tn)₃(H₂O)]³⁺. Another variety of the tris-carbonato anion, [Co(NH₃)₆][Co(CO₃)₃], was prepared and subjected to thermogravimetric analysis, and the absence of inner sphere water in the compound was confirmed. The plausible existence of inner sphere water for the compounds that emanate from the synthetic routes utilizing the Bauer and Drinkard method in the crystalline phase is proposed.     

Reactivity of Ammonium Halides: Action of Ammonium Chloride and Bromide on Iron and Iron(III) Chloride and Bromide

Ammonium chloride and bromide, (NH₄)Cl and (NH₄)Br, act on elemental iron producing divalent iron in [Fe(NH₃)₂]Cl₂ and [Fe(NH₃)₂]Br₂, respectively, as single crystals at temperatures around 450 °C. Iron(III) chloride and bromide, FeCl₃ and FeBr₃, react with (NH₄)Cl and (NH₄)Br producing the erythrosiderites (NH₄)₂[Fe(NH₃)Cl₅] and (NH₄)₂[Fe(NH₃)Br₅], respectively, at fairly low temperatures (350 °C). At higher temperatures, 400 °C, iron(III) in (NH₄)₂[Fe(NH₃)Cl₅] is reduced to iron(II) forming (NH₄)FeCl₃ and, further, [Fe(NH₃)₂]Cl₂ in an ammonia atmosphere. The reaction (NH₄)Br + Fe (4:1) leads at 500 °C to the unexpected hitherto unknown [Fe(NH₃)₆]₃[Fe₈Br₁₄], a mixed‐valent Fe^II/Fe^I compound. Thermal analysis under ammonia and the conditions of DTA/TG and powder X‐ray diffractometry shows that, for example, FeCl₂ reacts with ammonia yielding in a strongly exothermic reaction [Fe(NH₃)₆]Cl₂ that at higher temperatures produces [Fe(NH₃)]Cl₂, FeCl₂ and, finally, Fe₃N.     

Über die Kristallstrukturen der Cyanokomplexe [Co(NH3)6][Fe(CN)6], [Co(NH3)6]2[Ni(CN)4]3 · 2 H2O und [Cu(en)2][Ni(CN)4]

On the Crystal Structures of the Cyano Complexes [Co(NH₃)₆][Fe(CN)₆], [Co(NH₃)₆]₂[Ni(CN)₄]₃ · 2 H₂O, and [Cu(en)₂][Ni(CN)₄] Of the three title compounds X‐ray structure determinations were performed with single crystals. [Co(NH₃)₆][Fe(CN)₆] (a = 1098.6(6), c = 1084.6(6) pm, R3, Z = 3) crystallizes with the CsCl‐like [Co(NH₃)₆][Co(CN)₆] type structure. [Co(NH₃)₆]₂[Ni(CN)₄]₃ · 2 H₂O (a = 805.7(5), b = 855.7(5), c = 1205.3(7) pm, α = 86.32(3), β = 100.13(3), γ = 90.54(3)°, P1, Z = 1) exhibits a related cation lattice, the one cavity of which is occupied by one anion and 2 H₂O, whereas the other contains two anions parallel to each other with distance Ni…Ni: 423,3 pm. For [Cu(en)₂][Ni(CN)₄] (a = 650.5(3), b = 729.0(3), c = 796.5(4) pm, α = 106.67(2), β = 91.46(3), γ = 106.96(2)°, P1, Z = 1) the results of a structure determination published earlier have been confirmed. The compound is weakly paramagnetic and obeys the Curie‐Weiss law in the range T < 100 K. The distances within the complex ions of the compounds investigated (Co–N: 195.7 and 196.4 pm, Ni–C: 186.4 and 186.9 pm, resp.) and their hydrogen bridge relations are discussed.     

Untersuchung von Hydrolysereaktionen zum Aufbau von Eisen(III)‐Oxo‐Aggregaten

Investigation of the Hydrolytic Build‐up of Iron(III)‐Oxo‐Aggregates The synthesis and structures of five new iron/hpdta complexes [{Fe^III₄(μ‐O)(μ‐OH)(hpdta)₂(H₂O)₄}₂Fe^II(H₂O)₄]·21H₂O ( 2 ), (pipH₂)₂[Fe₂(hpdta)₂]·8H₂O ( 4 ), (NH₄)₄[Fe₆(μ‐O)(μ‐OH)₅(hpdta)₃]·20.5H₂O ( 5 ), (pipH₂)_1.5[Fe₄(μ‐O)(μ‐OH)₃(hpdta)₂]·6H₂O ( 7 ), [{Fe₆(μ₃‐O)₂(μ‐OH)₂(hpdta)₂(H₄hpdta)₂}₂]·py·50H₂O ( 9 ) are described and the formation of these is discussed in the context of other previously published hpdta‐complexes (H₅hpdta = 2‐Hydroxypropane‐1, 3‐diamine‐N, N, N′, N′‐tetraacetic acid). Terminal water ligands are important for the successive build‐up of higher nuclearity oxy/hydroxy bridged aggregates as well as for the activation of substrates such as DMA and CO₂. The formation of the compounds under hydrolytic conditions formally results from condensation reactions. The magnetic behaviour can be quantified analogously up to the hexanuclear aggregate 5 . The iron(III) atoms in 1 ‐ 7 are antiferromagnetically coupled giving rise to S = 0 spin ground states. In the dodecanuclear iron(III) aggregate 9 we observe the encapsulation of inorganic ionic fragments by dimeric{M₂hpdta}‐units as we recently reported for Al^III/hpdta‐system.     

Kaliumhexahydroxochromat(III), K3[Cr(OH)6]: Beispiel eines neuen Syntheseweges für Metallhydroxide und Hydroxometallate

Potassium Hexaydroxochromate(III), K₃[Cr(OH)₆]: An Example for a New Synthetic Way to Metal Hydroxides and Hydroxometallates The comproportionation of nitrate with amide ions in supercritical ammonia leads to the formation of hydroxide ions and elementary nitrogen: [Cr(NH₃)₆](NO₃)₃ reacts with KNH₂ at 250°C and 6 kbar NH₃-pressure to K₃[Cr(OH)₆], K(H₂O)OH and an unknown yellow microcrystalline phase. The bluegreen hydroxochromate is well crystallized. The x-ray structure determination on K₃[Cr(OH)₆] gave the atomic arrangement inclusive the hydrogen position. The unit cell with a = 10.672(4) Å and c = 11.083(3) Å contains six formular units; the space group is R3 c. The chemical bonding in this compound is discussed.     

Reactivity,Syntheses, and Crystal Structures of Na5[MO2][X] with M = Co+, Ni+, Cu+; X = CO32—, SO42—, SO32—, S2—, and Na25[CuO2]5[SO4]4[S]

Na₅[CuO₂][CO₃], Na₅[CuO₂][SO₃], Na₅[CuO₂][S], and Na₅[CuO₂][SO₄] were obtained as single crystals and powders from reactions of Na₂O, Cu₂O, and Na₂X with X = CO₃^2—, SO₃^2—, S^2—, and SO₄^2—, respectively. A redox reaction between CdO and Co metal occurs in the presence of Na₂O and Na₂X, yielding Na₅[CoO₂][X] with X = CO₃^2— and S^2—. From a mixture of Na₂SO₄, CdO and Na₂O in Ni‐containers we observed the formation of Na₅[NiO₂][S] single crystals. Single crystals of Na₂₅[CuO₂]₅[SO₄]₄[S] can be grown by annealing Na₅[CuO₂][SO₃] at 600 °C, leading to the decomposition of SO₃^2—, yielding SO₄^2— and S^2— at 550 °C. The structures have been determined from single crystal data and powder data. All structures contain the isolated complex [MO₂]^3— in a dumb‐bell like arrangement. The main feature of these compounds is that the anions SO₄^2—, SO₃^2—, CO₃^2— and S^2— are not connected to the transition metal. The formation of Na₅[CuO₂][X] (X = S^2—, SO₄^2—, SO₃^2—, CO₃^2—) has been studied by thermal analysis and in situ X‐ray diffraction techniques. Infrared spectra confirm the presence of SO₄^2—, SO₃^2—, and CO₃^2—, respectively, in the structures.     

Synthesen und NMR‐Untersuchungen von Salzen mit den neuen Anionen [PtXn(CF3)6‐n]2— (n = 0 ‐ 5, X = F,OH, Cl,CN) und die Kristallstrukturanalyse von K2[(CF3)2F2Pt(μ‐OH)2PtF2(CF3)2]·2H2O

Syntheses and NMR Spectroscopic Ivestigations of Salts containing the Novel Anions [PtX_n(CF₃)_6‐n]^2— (n = 0 ‐ 5, X = F, OH, Cl, CN) and Crystal Structure of K₂[(CF₃)₂F₂Pt(μ‐OH)₂PtF₂(CF₃)₂]·2H₂O The first syntheses of trifluoromethyl‐complexes of platinum through fluorination of cyanoplatinates are reported. The fluorination of tetracyanoplatinates(II), K₂[Pt(CN)₄], and hexacyanoplatinates(IV), K₂[Pt(CN)₆], with ClF in anhydrous HF leads after working up of the products to K₂[(CF₃)₂F₂Pt(μ‐OH)₂PtF₂(CF₃)₂]·2H₂O. The structure of the salt is determined by a X‐ray structure analysis, P2₁/c (Nr. 14), a = 11.391(2), b = 11.565(2), c = 13.391(3)Å, β = 90.32(3)°, Z = 4, R₁ = 0.0326 (I > 2σ(I)). The reaction of [Bu₄N]₂[Pt(CN)₄] with ClF in CH₂Cl₂ generates mainly cis‐[Bu₄N]₂[PtCl₂(CF₃)₄] and fac‐[Bu₄N]₂[PtCl₃(CF₃)₃], but in contrast that of [Bu₄N]₂[Pt(CN)₆] with ClF in CH₂Cl₂ results cis‐[Bu₄N]₂[PtX₂(CF₃)₄], [Bu₄N]₂[PtX(CF₃)₅] (X = F, Cl) and [Bu₄N]₂[Pt(CF₃)₆]. In the products [Bu₄N]₂[PtX_n(CF₃)_6‐n] (X = F, Cl, n = 0—3) it is possibel to exchange the fluoro‐ligands into chloro‐ and cyano‐ligands by treatment with (CH₃)₃SiCl und (CH₃)₃SiCN at 50 °C. With continuing warming the trifluoromethyl‐ligands are exchanged by chloro‐ and cyano‐ligands, while as intermediates CF₂Cl and CF₂CN ligands are formed. The identity of the new trifluoromethyl‐platinates is proved by ¹⁹⁵Pt‐ and ¹⁹F‐NMR‐spectroscopy.     

Polyol-Metall-Komplexe. 27. Bis-diolato-antimonate(III) mit Guanosin als Diol

Polyol Metal Complexes. 27. Bis-Diolato Antimonates(III ) with Guanosine as the Diol The complex anions of K₃[Sb^III(Guo1,2′,3′H_?3)₂] · 10 H₂O ( 1 ) and [Co(NH₃)₆][Sb^III(Guo1,2′,3′H_?3)₂] · 9 H₂O ( 2 ) are four-coordinate homoleptic bis(diolato)antimonate(III ) species. The guanosine trianions act as carbohydrate ligands through their cis-furanoidic ribosyl moiety, thus forming no nucleobase–metal bonds.     

Derivate des Flußspat-Typs: [Fe(NH3)6][TaF6]2 und [Ni(NH3)6][TaF6]2

Derivatives of the Fluorite Type: [Fe(NH₃)₆][TaF₆]₂ and [Ni(NH₃)₆][TaF₆]₂ Light blue single crystals of [Fe(NH₃)₆][TaF₆]₂ and [Ni(NH₃)₆][TaF₆]₂ are obtained from 36 : 1 : 6 molar mixtures of (NH₄)F, iron/nickel and tantalum powders, respectively, in sealed Monel metal ampoules at 400 °C. They both crystallize isotypic with [Co(NH₃)₆][PF₆]₂ (cubic, Fm-3m, Z = 4, a = 1259.0(2)/1260.4(2) pm) in a structure that can be derived from the basic fluorite-type of structure according to [Ca][F]₂≡[Fe(NH₃)₆][TaF₆]₂, for example.     

Zur solvensfreien Darstellung von Tetramethylammoniumsalzen: Synthese und Charakterisierung von [N(CH3)4]2[C2O4], [N(CH3)4][CO3(CH3)], [N(CH3)4][NO2], [N(CH3)4][CO2H] und [N(CH3)4][O2C(CH2)2CO2(CH3)]

Solvent-free Synthesis of Tetramethylammonium Salts: Synthesis and Characterization of [N(CH₃)₄]₂[C₂O₄], [N(CH₃)₄][CO₃CH₃], [N(CH₃)₄][NO₂], [N(CH₃)₄][CO₂H], and [N(CH₃)₄][O₂C(CH₂)₂CO₂CH₃] A general procedure to synthesize tetramethylammonium salts is presented. Several tetramethylammonium salts were prepared in a crystalline state by solvent-free reaction of trimethylamine and different methyl compounds at mild conditions: [N(CH₃)₄]₂[C₂O₄] (cubic; a = 1 114.8(3) pm), [N(CH₃)₄][CO₃CH₃] (P2₁/n; a = 813.64(3), b = 953.36(3), c = 1 131.3(4) pm, β = 90.03(1)°), [N(CH₃)₄][NO₂] (Pmmn; a = 821.2(4), b = 746.5(3), c = 551.5(2) pm), [N(CH₃)₄][CO₂H] (Pmmn; a = 792.8(7), b = 791.7(3), c = 563.3(4) pm) and [N(CH₃)₄][O₂C(CH₂)₂CO₂CH₃] (P2₁; a = 731.1(2), b = 826.4(3), c = 1 025.2(3) pm, β = 110.1(1)°). The tetramethylammonium salts were characterized by IR-spectroscopy and X-ray diffraction. The crystal structures of the methylcarbonate and the nitrite are described.     

Neues über Zweikernige Oxoferrate(II)

News about Binuclear Oxoferrates(II) [1] . By “reaction with the wall” of the Fe-cylinders used here we synthesized the new oxoferrates(II) Cs₆[Fe₂O₅], Cs_3.5Rb_2.5[Fe₂O₅] and Rb₄K₂[Fe₂O₅] in the form of red single crystals. The structure elucidation via four-circle-diffractometer data shows that the new oxoferrates(II) are isotypic with Cs₂(Cs_0.35K_1.65)K₂ [Fe₂O₅]. In the structure we have isolated binuclear groups [(O1)₂Fe—O(2)—Fe(O1)₂]^6?. Structure refinements is possible in the centrosymmetrial space group C2/m as well as in the space groups C2 and Cm without centre of symmetry. The existence of two further oxoferrates(II) Cs_6?xRb_x[Fe₂O₅] and Cs_6?xK_x[Fe₂O₅] which can be described as solid solutions was confirmed by power-data.     

Gradual transformation of Ca(OH)<Subscript>2</Subscript> into CaCO<Subscript>3</Subscript> on cement hydration

The low temperature of decomposition of some calcium carbonates and the bending of the TG curves of hydrated cement between 500 and 800°C suggested the presence of some complex compound(s), which needed complementary investigation (XRD, TG). Stepwise transformation of portlandite (and/or lime) into calcium carbonate, with intermediate steps of calcium carbonate hydroxide hydrates (CCH-1 to CCH-5), was indicated by the previous study of two OPC. This was checked here on four cements ground for t _g=15, 20, 25 and 30 min and hydrated either in water vapour, successively at RH=1.0, 0.95 and 0.5 for 2 weeks each (WR1, WR2 and WR3, respectively) or as mortars in liquid water (1m), followed by WR as above. The d[001] spacing of portlandite was confirmed to vary: here between the lowest and the highest standard values. The diffractograms of n=32 different samples were analyzed for presence of standard CCH peaks, generally slightly displaced. These were: CCH-1 [Ca₃(CO₃)₂(OH)₂]: N=11 peaks, of three different d[hkl] spacings, CCH-2 [Ca₆(CO_2.65)₂(OH₆₅₇)₇(H₂O)₂]: N=10 for two d[hkl], CCH-3 [Ca₃(CO₃)₂(OH)₂·1.5H₂O]: N=14 for five d[hkl], CCH-4, ikaite [CaCO₃(H₂O)₆]: N=13 for six d[hkl], CCH-5[CaCO₃(H₂O)]: N=15 for five d[hkl]. Thus the most probable is the presence of the last three. The stepwise transformation of Ca(OH)₂ into CaCO₃ was confirmed:     

Computer-aided measurement of kinetic parameters of electrode reactions of cobalt(III)—ammine complexes at mercury electrodes

A computer-aided technique based on Tast polarography is examined for the determination of kinetic parameters of electrode reactions. It is particularly useful for the investigation of unstable species because of the simple and rapid processing of data. Kinetic parameters of cobalt(III)—ammine complexes at mercury electrodes are given for [Co(NH₃)₆]Cl₃, [Co(H₂O)(NH₃)₅](ClO₄)₃, [Co(NO₃)(NH₃)₅](NO₃)₂ [CoF(NH₃)₅](Cl0₄)₂, [Co(C0₃)(NH₃)₅] NO₃ ,cis-[Co(H₂O)₂(NH₃)₄] (Cl0₄)₃ [Co(CO₃)(NH₃)₄] NO₃ · 0.5H₂0, [Co(ox)(NH₃)₄]Cl · H₂0, and NH₄[Co(ox)₂(NH₃)₂] · H₂O, which are obtained in solutions containing 0.1 M acetate buffer and 0.005% gelatin at 25°C.