Abstract Generated abstract
This communication reports the synthesis of cobalt(III) dimethylglyoxime complexes containing one coordinated water molecule and one molecule of ammonia or an organic amine, with the general cationic form [Co(DH)2(H2O)A]+. The compounds were prepared by adding calculated amounts of amines, including aniline, toluidines, p-anisidine, pyridine, beta-picoline, or ammonium acetate, to cooled aqueous solutions of trans-bis-dimethylglyoximatodiaquocobalt nitrate, and were characterized by elemental analyses, solubility, conductivity, pH measurements, and absorption spectra. Reactions of the aquoanilino complex with excess aniline and with hydrohalic acids gave known trans dianilino and halide derivatives, supporting retention of the trans configuration during substitution of one coordinated water molecule.
Full Text
Chemistry
Academician of the Academy of Sciences of the Moldavian SSR A. V. Ablov, B. A. Bobylkin, N. M. Samus’
Co(III) Dioximes Containing in the Inner Sphere a Molecule of Water and a Molecule of Ammonia or an Organic Amine
Complex Co(III) cations with dimethylglyoxime and ammonia or organic amines of the type \([\mathrm{Co}(\mathrm{DH})_2\mathrm{A}_2]^+\) were described by L. A. Chugaev as early as 1905 \((^1)\). As has now been shown, they have a trans configuration \((^{2,3})\). Comparatively recently A. V. Ablov, M. P. Filippov, and N. M. Samus’ synthesized salts of trans-bis-dimethylglyoximatodiaquocobalt
\([\mathrm{Co}(\mathrm{DH})_2\cdot(\mathrm{H_2O})_2]X\) \((^4)\).
In the present communication we describe cobalt(III) dioximes containing in the inner sphere one molecule of water and one molecule of ammonia or an organic amine, of the general formula \([\mathrm{Co}(\mathrm{DH})_2(\mathrm{H_2O})\mathrm{A}]\mathrm{NO}_3\). To obtain them, an exactly calculated amount of amine is added to a cooled aqueous solution of trans-bis-dimethylglyoximatodiaquocobalt nitrate. In the case of aniline, for example, brown crystals of
\([\mathrm{Co}(\mathrm{DH})_2(\mathrm{H_2O})(\mathrm{H_2NC_6H_5})]\mathrm{NO}_3\cdot2\mathrm{H_2O}\) separated. In aqueous solution this salt behaves as a binary electrolyte and shows an acidic reaction, but it is a weaker acid than the salts of trans-bis-dimethylglyoximatodiaquocobalt. The absorption curve of a dilute aqueous solution has two absorption bands (Fig. 1). The first band in the region of 350 nm is due to the coordinated aromatic amine; the second band at \(\lambda = 250\) nm is characteristic of the planar \(\mathrm{Co}(\mathrm{DH})_2\) grouping \((^5)\).
Fig. 1. Light-absorption curves: \(a\)—1,6-\([\mathrm{Co}(\mathrm{DH})_2(\mathrm{H_2O})(\mathrm{H_2NC_6H_5})]\mathrm{NO}_3\cdot2\mathrm{H_2O}\) (\(C = 0.001\) mol); \(b\)—1,6-\([\mathrm{Co}(\mathrm{DH})_2(\mathrm{H_2NC_6H_5})_2]\mathrm{NO}_3\cdot2\mathrm{H_2O}\), from \((^6)\).
When an excess of aniline acts on the nitrate obtained by us, a substance is formed which, in crystal form and color, resembles bis-dimethylglyoximatodianilinecobalt nitrate
\([\mathrm{Co}(\mathrm{DH})_2(\mathrm{H_2NC_6H_5})_2]\mathrm{NO}_3\cdot2\mathrm{H_2O}\) \((^6)\).
The nature of this compound was confirmed by recording the light-absorption curve \((^5)\) and by converting it, under the action of alkali, into the characteristic base
\([\mathrm{Co}(\mathrm{D_2H})(\mathrm{H_2NC_6H_5})_2]\cdot3\mathrm{H_2O}\) \((^7)\).
On addition of one mole of hydrochloric acid to a concentrated aqueous solution of the salt obtained by us, a microcrystalline brown precipitate, sparingly soluble in water, immediately separates. In all its properties this compound is the nonelectrolyte
\([\mathrm{CoCl}(\mathrm{DH})(\mathrm{H_2NC_6H_5})]\cdot2\mathrm{H_2O}\) \((^8)\). Similarly, on addition of one mole of hydrobromic or hydroiodic acid, the nonelectrolytes
\([\mathrm{CoBr}(\mathrm{DH})_2(\mathrm{H_2NC_6H_5})]\cdot2\mathrm{H_2O}\) and \([\mathrm{CoI}(\mathrm{DH})_2(\mathrm{H_2NC_6H_5})]\cdot\frac{1}{2}\mathrm{H_2O}\) precipitated \((^8)\).
Since the dianilino and monoanilino dioximes \([\mathrm{Co}(\mathrm{DH})_2(\mathrm{H_2NC_6H_5})_2]^+\) and \([\mathrm{CoHal}(\mathrm{DH})_2(\mathrm{H_2NC_6H_5})]\), into which the aquoanilino complex is readily converted, have a trans configuration \((^9)\), the original cation must have the same structure. Therefore the reaction
trans-\([ \mathrm{Co}(\mathrm{DH})_2(\mathrm{H_2O})_2]^+ + \mathrm{H_2NC_6H_5} = [\mathrm{Co}(\mathrm{DH})_2(\mathrm{H_2NC_6H_5})(\mathrm{H_2O})]^+ + \mathrm{H_2O}\) is not accompanied by a change in spatial configuration.
By the method described above, cations of the type \([\mathrm{Co}(\mathrm{DH})_2(\mathrm{H_2O})A]^+\) were synthesized with amines: aniline, o-, m-, and p-toluidines, p-anisidine, pyridine, and β-picoline.
To obtain the aquoammine dioxime, to a solution of trans-\([\mathrm{Co}(\mathrm{DH})_2(\mathrm{H_2O})_2]\mathrm{NO_3}\cdot \mathrm{H_2O}\) a calculated amount of ammonium acetate was added. Under these conditions there is no excess ammonia in the solution, and therefore the cation \([\mathrm{Co}(\mathrm{DH})_2(\mathrm{NH_3})_2]^+\) is not formed.
Experimental Part
Nitrate of trans-bis-dimethylglyoximatoaquoanilinecobalt(III). \((\mathrm{Co}\cdot(\mathrm{DH})_2(\mathrm{H_2O})(\mathrm{H_2NC_6H_5}))\mathrm{NO_3}\cdot 2\mathrm{H_2O}\).
To 2.0 g of trans-\([\mathrm{Co}(\mathrm{DH})_2(\mathrm{H_2O})_2]\mathrm{NO_3}\cdot \mathrm{H_2O}\) \(^{(4)}\) 30 ml of water were added, the mixture was cooled to \(5\text{–}10^\circ\), and a solution of 0.4 ml (5 mmoles) of aniline in 20 ml of alcohol was carefully poured in. From the filtered solution, after some time, a brown precipitate separates, which under the microscope has the appearance of rectangular plates. The substance is readily soluble in water and in alcohol, less readily in ether. Yield 70% of theory. The nitrate obtained was dissolved in water at \(10^\circ\) and precipitated with sodium nitrate. For analysis, the air-dried substance was taken.
Found, %: Co 11.86; 11.88; N 16.63; 16.70; C 33.61; 33.54;
H 5.23; 5.31; H₂O 7.30
\(\mathrm{CoC_{14}H_{23}N_6O_8\cdot 2H_2O}\). Calculated, %: Co 11.82; N 16.87; C 33.73; H 5.46; H₂O 7.23
The substance may also be obtained in the following manner. 1.7 g (5 mmoles) of trans-hydroxo-bis-dimethylglyoximatoaquocobalt \([\mathrm{Co}(\mathrm{OH})(\mathrm{DH})_2\cdot(\mathrm{H_2O})]\) \(^{(4,10)}\) was covered with 30 ml of water cooled to \(5\text{–}10^\circ\), and 0.4 ml (5 mmoles) of aniline dissolved in 20 ml of ethanol was added, after which the hydroxoaquo compound rapidly dissolves. To the filtered solution, a calculated amount of concentrated nitric acid was added dropwise. A brown precipitate separated, which was transferred to a filter and washed with cold water, a small amount of alcohol, and finally with ether.
Found, %: Co 11.90; N 16.65
\(\mathrm{CoC_{14}H_{23}N_6O_8\cdot 2H_2O}\). Calculated, %: Co 11.82; N 16.87
Below are given the electrical conductivity and pH of solutions of nitrate of bis-dimethylglyoximatoaquoanilinecobalt:
| \(V\), l·mole\(^{-1}\) | \(\mu\), ohm\(^{-1}\)·l·cm\(^{-2}\) | pH |
|---|---|---|
| 250 | 100.1 | 5.00 |
| 500 | 102.2 | 5.10 |
| 1000 | 106.4 | 5.22 |
Nitrate of bis-dimethylglyoximatoaquo (p-toluidine)cobalt(III) \([\mathrm{Co}(\mathrm{DH})_2(\mathrm{H_2O})(\mathrm{H_2NC_6H_4(CH_3)})]\mathrm{NO_3}\).
The substance was obtained analogously to the preceding one, with a yield of 80% of theory. Under the microscope it has the appearance of yellow plates.
Found, %: Co 12.37; 12.39; N 17.34; 17.40
\(\mathrm{CoC_{15}H_{25}N_6O_8}\). Calculated, %: Co 12.36; N 17.65
Nitrate of bis-dimethylglyoximatoaquo (m-toluidine)cobalt(III) \([\mathrm{Co}(\mathrm{DH})_2(\mathrm{H_2O})(\mathrm{H_2NC_6H_4(CH_3)})]\mathrm{NO_3}\).
Under the microscope it has the appearance of long thin needles.
Found, %: Co 12.24; 12.30; N 17.66; 17.58
\(\mathrm{CoC_{15}H_{25}N_6O_8}\). Calculated, %: Co 12.36; N 17.65
Bis-dimethylglyoximatoaquo(o-toluidine)cobalt(III) nitrate
\([ \mathrm{Co(DH)_2(H_2O)(H_2NC_6H_4CH_3)} ]\mathrm{NO_3}\).
A light-yellow substance; under the microscope it has the appearance of long rectangular plates.
\[ \mathrm{CoC_{15}H_{25}N_6O_8}. \quad \begin{aligned} &\text{Found, \%: } && \mathrm{Co}\ 12.33;\ 12.30;\quad \mathrm{N}\ 17.55;\ 17.48\\ &\text{Calculated, \%: } && \mathrm{Co}\ 12.36;\quad \mathrm{N}\ 17.65 \end{aligned} \]
Bis-dimethylglyoximatoaquo(\(p\)-anisidine)cobalt(III) nitrate
\([ \mathrm{Co(DH)_2(H_2O)(H_2NC_6H_4OCH_3)} ]\mathrm{NO_3}\cdot 2\mathrm{H_2O}\).
A reddish substance. Under the microscope it has the appearance of square plates.
\[ \mathrm{CoC_{15}H_{25}N_6O_9}\cdot 2\mathrm{H_2O}. \quad \begin{aligned} &\text{Found, \%: } && \mathrm{Co}\ 11.27;\ 11.20;\quad \mathrm{N}\ 15.78;\ 15.75;\quad \mathrm{H_2O}\ 6.95\\ &\text{Calculated, \%: } && \mathrm{Co}\ 11.16;\quad \mathrm{N}\ 16.92;\quad \mathrm{H_2O}\ 6.82 \end{aligned} \]
Bis-dimethylglyoximatoaquopyridinecobalt(III) nitrate
\([ \mathrm{Co(DH)_2(H_2O)Py} ]\mathrm{NO_3}\).
A light-brown substance, which under the microscope has the appearance of long prisms.
\[ \mathrm{CoC_{13}H_{21}N_6O_8}. \quad \begin{aligned} &\text{Found, \%: } && \mathrm{Co}\ 13.02;\ 13.10;\quad \mathrm{N}\ 18.88;\ 18.90;\quad \mathrm{C}\ 34.96;\ 35.00\\ &&& \mathrm{H}\ 4.79;\ 4.79\\ &\text{Calculated, \%: } && \mathrm{Co}\ 13.14;\quad \mathrm{N}\ 18.75;\quad \mathrm{C}\ 34.81;\\ &&& \mathrm{H}\ 4.72 \end{aligned} \]
Bis-dimethylglyoximatoaquo(β-picoline)cobalt(III) nitrate
\([ \mathrm{Co(DH)_2(H_2O)(C_5H_4NCH_3)} ]\mathrm{NO_3}\).
Under the microscope it has the appearance of yellow long prisms.
\[ \mathrm{CoC_{14}H_{23}N_6O_8}. \quad \begin{aligned} &\text{Found, \%: } && \mathrm{Co}\ 12.74;\ 12.78;\quad \mathrm{N}\ 18.06;\ 17.75\\ &\text{Calculated, \%: } && \mathrm{Co}\ 12.75;\quad \mathrm{N}\ 18.19 \end{aligned} \]
Bis-dimethylglyoximatoaquoamminecobalt(III) nitrate
\([ \mathrm{Co(DH)_2(H_2O)(NH_3)} ]\mathrm{NO_3}\).
2.0 g (5 mmoles) of \([ \mathrm{Co(DH)_2(H_2O)_2} ]\mathrm{NO_3}\cdot \mathrm{H_2O}\) was dissolved in 30 ml of water cooled to \(5\text{–}10^\circ\); to the filtered solution, 0.35 g (5 mmoles) of ammonium acetate was added. On standing, and more rapidly upon addition of alcohol, brown crystals separated from the solution; under the microscope they have the appearance of squares. The substance is readily soluble in water, somewhat less so in alcohol and ether.
\[ \mathrm{CoC_8H_{19}N_6O_8}. \quad \begin{aligned} &\text{Found, \%: } && \mathrm{Co}\ 15.30;\ 15.31;\quad \mathrm{N}\ 21.80;\ 21.78\\ &\text{Calculated, \%: } && \mathrm{Co}\ 15.26;\quad \mathrm{N}\ 21.77; \end{aligned} \]
Kishinev State
University
Received
1 II 1965
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