Full Text
Chemistry
Academician A. N. Nesmeyanov, V. N. Drozd, V. A. Sazonova,
V. N. Postnov
Some Properties of Diazo Compounds of Ferrocene
In the present work we investigated the chemical properties and reactivity of ferrocenyl diazonium, obtained by us in the acidolysis of benzoldiazoaminoferrocene. As we showed earlier (^1), the ferrocenyl diazonium cation readily reacts according to the type of substitution reactions with evolution of nitrogen with \(X^-\) \((X = \mathrm{Cl}, \mathrm{Br}, \mathrm{J}, \mathrm{OH})\), giving \(\mathrm{C_5H_5FeC_5H_4X}\) at temperatures of \(-15\)—\(0^\circ\). The ferrocenyl diazonium cation also enters into the azo-coupling reaction, forming with \(\beta\)-naphthol a dark-green 1-ferrocenazo-2-naphthol. It was to be expected that, owing to the greater nucleophilicity of the ferrocene nucleus in comparison, for example, with benzene, ferrocenyl diazonium salts would enter into the azo-coupling reaction less energetically than phenyldiazonium salts. Indeed, phenol in the form of the phenolate ion, in contrast to the more reactive \(\beta\)-naphthol, which reacts almost instantaneously, reacts slowly with a ferrocenyl diazonium salt over several hours at \(-50^\circ\)—\(-15^\circ\), forming dark-red \(n\)-ferrocenazophenol, which, unlike the chelate 1-ferrocenazo-2-naphthol, is readily soluble in alkalis. Still more slowly and in lower yield, in the presence of pyridine as catalyst (^2), dimethylaniline reacts under these conditions, with formation of red-brown \(n\)-ferrocenazodimethylaniline:
\[ \mathrm{C_5H_5FeC_5H_4N_2^+;} + \mathrm{C_6H_5R} \rightarrow n\text{-}\mathrm{RC_6H_4 - N = N - C_5H_4FeC_5H_5} \]
\[ \mathrm{R = -OH,\ -N(CH_3)_2.} \]
Conversely, the free electron pair of the nitrogen atom in primary and secondary amines is fairly readily attacked by the ferrocenyl diazonium cation, with subsequent formation of the corresponding triazenes:
\[ \mathrm{C_5H_5FeC_5H_4 - N = N - NHC_6H_5} \ \underset{-\mathrm{H^+}}{\stackrel{\mathrm{H^+}}{\rightleftarrows}}\ \mathrm{C_5H_5FeC_5H_4N_2^+ + C_6H_5NH_2} \]
\[ \begin{array}{ccc} & \mathrm{HNRR'} & \\ \swarrow & & \searrow\ \beta\text{-}\mathrm{C_{10}H_7NH_2} \\ \mathrm{C_5H_5FeC_5H_4N = N - NRR'} & & \beta\text{-}\mathrm{C_{10}H_7N = N - NHC_5H_4FeC_5H_5.} \end{array} \]
\[ \mathrm{R = R' = C_2H_5} \]
\[ \mathrm{R = CH_3;\quad R' = C_6H_5} \]
We established that the acidolysis of benzoldiazoaminoferrocene is a reversible reaction: on treatment of the reaction mixture with pyridine the initial triazene was isolated again. On addition of diethylamine, yellow 3,3-diethyl-1-ferrocenyltriazene is formed, and from a mixture of methylaniline and pyridine—red 3-methyl-3-phenyl-1-ferrocenyltriazene. The triazene formed in the interaction of ferrocenyl diazonium with \(\beta\)-naphthylamine in the presence of pyridine, in all probability, has the structure \(\beta\)-\(\mathrm{C_{10}H_7 - N = N - NHC_5H_4FeC_5H_5}\), in contrast to \(\mathrm{C_5H_5FeC_5H_4N = N - NHC_6H_5}\), evidently owing to the greater nucleophilicity of \(\beta\)-naphthyl as compared with phenyl. Indeed, \(\beta\)-naphthalinediazoaminoferrocene, on treatment with conc. HCl at low temperatures, does not form the violet solution of ferrocenyl diazonium. It should be noted that the position of the absorption bands of the \(\mathrm{N-H}\) bonds in the IR spectra of benzoldiazoaminoferrocene and \(\beta\)-naphthalinediazoaminoferrocene differs greatly: \(3280\ \mathrm{cm^{-1}}\) for the former and \(3435\ \mathrm{cm^{-1}}\) for the latter.
\(\beta\)-Naphthol, as well as compounds with active methylene groups—acetylacetone and acetoacetic ester—on heating to \(100^\circ\) react
with benzoyldiazoaminoferrocene, forming the corresponding dyes: 1-ferrocenazo-2-naphthol, 3-ferrocenylhydrazonoacetylacetone (I), and ethyl α-ferrocenylhydrazonoacetoacetate (II):
\[ \mathrm{C_5H_5FeC_5H_4N{=}N{-}NHC_6H_5 + CH_2 \begin{matrix} \diagup \mathrm{COR}\\[-2pt] \diagdown \mathrm{COCH_3} \end{matrix} \ \xrightarrow{100^\circ}\ \mathrm{C_5H_5FeC_5H_4NHN{=}C \begin{matrix} \diagup \mathrm{COR}\\[-2pt] \diagdown \mathrm{COCH_3} \end{matrix} + C_6H_5NH_2} \]
\[ \mathrm{R=-OC_2H_5,\ -CH_3.} \]
The reaction with β-naphthol and acetylacetone proceeds rather rapidly, whereas with acetoacetic ester it is somewhat slower and is accompanied by the side formation of the anilide of α-ferrocenylhydrazonoacetoacetic acid, \(\mathrm{CH_3COC(=N{-}NHC_5H_4FeC_5H_5)CONHC_6H_5}\) (III). To prove the structure of the latter, a reciprocal synthesis was undertaken from acetoacetic acid anilide by heating with benzoyldiazoaminoferrocene; in this case, as a by-product, the β-anil of the anilide of α-ferrocenylhydrazonoacetoacetic acid, \(\mathrm{CH_3C(=NC_6H_5)C(=NNHC_5H_4FeC_5H_5)CONHC_6H_5}\) (IV), was isolated. Evidently, in both cases simultaneous attack occurs at the α-carbon atom and at one of the carbonyl groups of the acetoacetic ester or acetoacetic acid anilide by one molecule of the triazene, since on heating II and III with aniline or benzoyldiazoaminoferrocene under the same conditions, formation of III and IV, respectively, is not observed. Heating the triazene with less active azo components—phenol and dimethylaniline—is accompanied mainly by decomposition of the triazene.
We also succeeded in obtaining an aqueous solution of potassium ferrocenyl diazotate. If a solution of ferrocenyl diazonium chloride is alkalized with KOH at a temperature below \(-30^\circ\) and rapidly warmed to room temperature, resinous decomposition products are formed. With prolonged (several hours) stirring at \(-30 \div -20^\circ\) and slow warming, a dark-brown solution of potassium ferrocenyl diazotate is formed:
\[ \mathrm{C_5H_5FeC_5H_4N_2^+ \ \xrightleftharpoons[\mathrm{H^+}]{\mathrm{OH^-}}\ C_5H_5FeC_5H_4{-}N{=}N{-}O^- .} \]
If a solution of ferrocenyl diazotate cooled below \(-20^\circ\) is acidified, the violet color of ferrocenyl diazonium appears immediately. Ferrocenyl diazotate is thermally more stable than ferrocenyl diazonium; its aqueous solution can even be heated to boiling. It reacts very rapidly with acetylacetone, somewhat more slowly with acetoacetic ester, but does not react with β-naphthol or phenol. It was not possible to introduce ferrocenyl diazotate into the Gomberg reaction.
On the basis of the foregoing it follows that the ferrocenyl diazonium cation is less active in the azo-coupling reaction than, for example, the phenyldiazonium cation.
Experimental Part
1. p-Ferrocenazophenol. To a solution of 0.30 g of benzoyldiazoaminoferrocene in 25 ml of acetone, cooled to \(-65^\circ\), 2 ml of conc. HCl was added. The resulting violet solution of the ferrocenyl diazonium salt was poured, with stirring, into a solution, cooled to \(-15^\circ\), of 5 g of phenol in 30 ml of 20% KOH.* The reaction mixture was stirred vigorously at \(-50^\circ\) for one hour, then gradually over 3 h warmed to room temperature, diluted with water, and extracted with ether. The aqueous layer was acidified with 10% HCl, extracted with ether, the ether layer washed with water, dried over \(\mathrm{MgSO_4}\), the ether evaporated, and the excess phenol distilled off in vacuum. The residue
* When the concentration of phenol is decreased, the yield decreases.
chromatographed on Al₂O₃: a petroleum ether—ether mixture (3:1) elutes the phenol residues, and then the red band of p-ferrocenazophenol; yield 0.17 g (57% of theory), mp 220–221° (from ether); $\lambda_{\max}$ 240 mμ, lg $\varepsilon$ 4.02; $\lambda_{\max}$ 345 mμ, lg $\varepsilon$ 4.20; $\lambda_{\max}$ 530 mμ, lg $\varepsilon$ 3.32 (in methanol).
Found, %: C 62.78; 62.69; H 4.94; 4.85; Fe 18.38; 18.20; N 9.25; 9.25.
C₁₆H₁₄FeN₂O. Calculated, %: C 62.77; H 4.61; Fe 18.24; N 9.15.
2. p-Ferrocenazodimethylaniline. To a solution of 0.50 g of benzenediazoaminoferrocene in 30 ml of acetone, cooled to −50°, 3 ml of conc. HCl was added, and then, to the violet solution of the ferrocenediazonium salt, 10 ml of pyridine and 3 ml of dimethylaniline were added at such a rate that the temperature did not rise above −30°. The reaction mixture was thoroughly stirred and gradually heated to room temperature over 3 h, then diluted with water and extracted with ether; the ether layer was washed with water, the ether was evaporated, and then the pyridine and dimethylaniline were steam-distilled. p-Ferrocenazodimethylaniline was extracted with ether; the ether extract was dried over MgSO₄, the ether was distilled off, and the dye was purified by chromatography on Al₂O₃: a petroleum ether—benzene mixture (1:2) eluted 0.05 g (9% of theory) of p-ferrocenazodimethylaniline, mp 193–195° (with decomp.) (from hexane), reddish-brown crystals.
Found, %: C 64.98; 65.07; H 5.81; 5.87; Fe 16.52; 16.54; N 12.65; 12.77.
C₁₈H₁₉FeN₃. Calculated, %: C 64.88; H 5.75; Fe 16.76; N 12.61.
3. 3-Methyl-3-phenyl-1-ferrocenyltriazene. To a solution of 0.50 g of benzenediazoaminoferrocene in 15 ml of acetone, cooled to −50°, 3 ml of conc. HCl was added, and then, to the violet solution of the ferrocenediazonium salt, 2 ml of methylaniline and 20 ml of pyridine in 10 ml of acetone were added; the reaction mixture, with stirring, was gradually warmed to room temperature, diluted with water, and extracted with ether; the ether was washed with water and dried over MgSO₄, the ether was evaporated, and the residue was chromatographed on Al₂O₃. Heptane eluted 0.47 g (92% of theory) of 3-methyl-3-phenyl-1-ferrocenyltriazene, mp 103–104° (from hexane), red crystals.
Found, %: C 63.63; 63.88; H 5.51; 5.30; Fe 17.10; 17.30; N 13.36; 13.35.
C₁₇H₁₇FeN₃. Calculated, %: C 63.97; H 5.37; Fe 17.50; N 13.16.
4. 3,3-Diethyl-1-ferrocenyltriazene. Obtained from 0.50 g of benzenediazoaminoferrocene and 10 ml of diethylamine without the addition of pyridine under the conditions of experiment 3. Yield 0.42 g (90% of theory), mp 42.5–43.5° (from methanol), yellow crystals.
Found, %: C 59.03; 59.19; H 6.70; 6.74; Fe 19.67; 19.70; N 15.03; 14.97.
C₁₄H₁₉FeN₃. Calculated, %: C 58.96; H 6.72; Fe 19.58; N 14.74.
5. β-Naphthylindiazoaminoferrocene. Obtained from 0.50 g of benzenediazoaminoferrocene and 0.50 g of β-naphthylamine under the conditions of experiment 3. Chromatography with a benzene—heptane mixture; yield 0.52 g (91% of theory), mp 155–158° (with decomp.) (from methanol), brown crystals.
Found, %: C 67.37; 67.41; H 4.88; 4.87; Fe 15.50; 15.69; N 11.76; 11.94.
C₂₀H₁₇FeN₃. Calculated, %: C 67.63; H 4.82; Fe 15.72; N 11.83.
6. 1-Ferrocenazo-2-naphthol. A mixture of 0.30 g of benzenediazoaminoferrocene and 0.14 g of β-naphthol was heated to 100° for 40 min, and then heating was continued at this temperature for another 15 min. After cooling, the reaction mixture was dissolved in ether; the ether solution was washed with 10% KOH, water, 10% H₂SO₄, and water, dried over MgSO₄, the ether was evaporated, and the residue was chromatographed on Al₂O₃. Petroleum ether eluted a little ferrocene, and benzene eluted 0.21 g (60% of theory) of green 1-ferrocenazo-2-naphthol, mp 151–152° (from ether); $\lambda_{\max}$ 350 mμ, lg $\varepsilon$ 3.96; $\lambda_{\max}$ 405 mμ, lg $\varepsilon$ 4.20; $\lambda_{\max}$ 562 mμ, lg $\varepsilon$ 3.71 (in CCl₄). Lit.: mp 151–152° (¹).
- 3-Ferrocenylhydrazonoacetylacetone (I).
a) A mixture of 0.50 g of benzenediazoaminoferrocene and 2 ml of acetylacetone was heated at 100° for 1 hour. After cooling, the reaction mixture was dissolved in ether; the ethereal solution was shaken with an ammoniacal solution of copper acetate, filtered from copper acetylacetonate, washed with water, dried over MgSO₄, the ether was evaporated, and the residue was chromatographed on Al₂O₃. Heptane eluted a small amount of ferrocene, and a benzene—heptane mixture (1 : 1) eluted the red band I; yield 0.43 g (84% of theory), mp 121.5—122° (from hexane), ruby crystals, $\lambda_{\max}$ 350 mμ, $\lg \varepsilon$ 4.28; $\lambda_{\max}$ 510 mμ, $\lg \varepsilon$ 3.50 (in methanol).
Found, %: C 57.62; 57.44; H 5.28; 5.23; Fe 18.08; 18.03; N 8.91; 8.79.
C₁₅H₁₆FeN₂O₂. Calculated, %: C 57.72; H 5.17; Fe 17.89; N 8.97.
b) To a solution of 0.30 g of benzenediazoaminoferrocene in 20 ml of acetone, cooled to −50°, 2 ml of conc. HCl was added, and then to the violet solution of the ferrocenediazonium salt 10 ml of 20% KOH solution was added at such a rate that the temperature did not rise above −30°. The brown solution was stirred for 3 hours at −30°, then warmed to room temperature, diluted with 20 ml of water, and extracted with ether. The aqueous layer was a dark-brown solution of potassium ferrocenediazotate. This solution was stirred for 2 hours with 1 ml of acetylacetone and then extracted with ether. After the treatment described above, 0.11 g (37% of theory) of (I) was obtained.
- α-Ferrocenylhydrazonoacetoacetic ester (II).
a) A mixture of 0.50 g of benzenediazoaminoferrocene and 2 ml of acetoacetic ester was heated at 100° for 6 hours. After cooling, the reaction mixture was dissolved in ether, washed with 5% KOH, water, dried over MgSO₄, the ether was evaporated, and the residue was chromatographed on Al₂O₃. Petroleum ether first eluted a little ferrocene, then benzene eluted III, yield 0.24 g (38% of theory), and then 0.27 g (49% of theory) of II, mp 85—87° (from hexane), ruby crystals.
Found, %: C 56.25; 56.18; H 5.36; 5.49; Fe 16.41; 16.31; N 8.18; 8.06.
C₁₆H₁₈FeN₂O₂. Calculated, %: C 56.15; H 5.31; Fe 16.32; N 8.19.
b) To a solution of potassium ferrocenediazotate from 0.30 g of benzenediazoaminoferrocene, 1 ml of acetoacetic ester was added and the reaction mixture was stirred for 5 hours, and then II was extracted with ether. After the treatment described above, 0.17 g (58% of theory) of (II) was obtained.
- Anilide of α-ferrocenylhydrazonoacetoacetic acid (III) and β-anil anilide of α-ferrocenylhydrazonoacetoacetic acid (IV).
A mixture of 0.26 g of benzenediazoaminoferrocene and 0.15 g of acetoacetic acid anilide was heated at 100° for 8 hours. On chromatography on Al₂O₃, petroleum ether eluted a little ferrocene, and a benzene—petroleum ether mixture (1 : 1) eluted first IV, mp 139—140° (with decomp.) (from hexane), bright-red crystals.
Found, %: C 67.09; 67.09; H 5.36; 5.46; Fe 12.22; 12.09; N 12.21; 12.22.
C₂₆H₂₄FeN₄O. Calculated, %: C 66.96; H 5.62; Fe 11.98; N 12.01.
Then the same mixture eluted III, 0.20 g (70% of theory), mp 171—173° (from methanol), reddish-brown crystals, $\lambda_{\max}$ 265 mμ, $\lg \varepsilon$ 4.13; $\lambda_{\max}$ 365 mμ, $\lg \varepsilon$ 4.42; $\lambda_{\max}$ 500 mμ, $\lg \varepsilon$ 3.76 (in CCl₄).
Found, %: C 61.96; 61.86; H 5.01; 5.00; Fe 14.01; 14.19; N 10.92; 11.04.
C₂₀H₂₉FeN₃O₂. Calculated, %: C 61.71; H 4.92; Fe 14.35; N 10.80.
Moscow State University
named after M. V. Lomonosov
Received
8 VI 1964
REFERENCES
- A. N. Nesmeyanov, V. N. Drozd, V. A. Sazonova, DAN, 150, 102 (1963).
- G. Zollinger, Chemistry of Azo Dyes, 1960, p. 187.