COMPLEX COMPOUNDS OF ETHYLENEPYRIDINIUM CHLORIDE WITH MINERAL SALTS

I. I. Molodykh

Ethylenepyridinium chloride was described by I. Davidson [2] in 1862. He also obtained the corresponding chloroplatinate.

To prepare the starting product, freshly distilled pyridine was mixed with ethylene chloride in a molar ratio of 2:1 and with a small amount of ethyl alcohol.

The mixture in a closed flask was immersed in a water bath and heated to 100° for many hours. Ethylenepyridinium chloride separated in two forms: 1) as white, shiny leaflets; 2) as thin, long, transparent needles containing 2 moles of water of crystallization. The melting point is above 251°. On heating, beginning at 150°, the substance darkens; at 251° it blackens, but does not melt. It dissolves readily in water, less readily in alcohol.

Analysis of the complex

Sample 0.1933 g; AgCl 0.2150 g; Cl 0.05318 g;
found Cl 27.51%, calculated Cl 27.58%.

On the basis of the Lewis–Sidgwick representations [3, 1], the structural formula of the compound obtained may be represented as follows:

\[ \begin{array}{cc} \hexagon & \hexagon \\ \mathrm{Cl{:}N{:}C_2H_4{:}N{:}Cl} \end{array} \]

With ethylenepyridinium chloride and metal halides, the following complexes were obtained (Table 1):

Table 1

Complexes with Chlorides of Divalent Metals

1. Complex \([(C_5H_5N)_2C_2H_4]\cdot [CuCl_4]^{\prime\prime}\)

obtained by mixing concentrated aqueous solutions of the components in a ratio of 1:1, followed by evaporation on a water bath until crystallization began.

On cooling this solution, shiny, lemon-yellow plates separated out, readily soluble in water and acetone, and only slightly soluble in alcohol.

Analysis of the Complex

Determination of copper

Copper sulfide was precipitated and converted by ignition into the oxide.
Sample 0.2812 g; copper oxide 0.0570 g; copper 0.04554 g;
found Cu 16.19%; calculated Cu 16.24%.

Determination of chlorine

Sample 0.1177 g; AgCl 0.1716 g; Cl 0.0424 g;
found Cl 35.99%; calculated Cl 36.21%.

2. Complex \([(C_5H_5N)_2C_2H_4]\cdot [CuBr_2Cl_2]^{\prime\prime}\)

was obtained by adding finely powdered copper bromide, with thorough stirring, to an alcoholic solution of ethylenepyridinium chloride, in the form of a crystalline precipitate of reddish-brown color. Melting point 210°. Readily soluble in water and slightly soluble in alcohol.

Analysis of the Complex

Determination of copper

Copper sulfide was precipitated. It was converted by ignition into copper oxide.
Sample 0.3603 g; copper oxide 0.0599 g; copper 0.04785 g;
found Cu 13.28%; calculated Cu 13.23%.

Determination of chlorine and bromine

Sample 0.1171 g; AgCl + AgBr 0.1577 g; converted to AgCl 0.1365 g;
AgBr 0.0896 g; Br 0.03814 g;
AgCl 0.0682 g; Cl 0.01685 g;

found Cl 14.38%; calculated Cl 14.76%;
Br 32.57%; Br 33.28%.

3. Complex \([(C_5H_5N)_2C_2H_4]\cdot [ZnCl_4]^{\prime\prime}\)

obtained by adding finely powdered zinc chloride to a saturated aqueous solution of ethylenepyridinium chloride, followed by evaporation of the mixture until crystallization began.

Small, well-formed, shiny crystals with a pink tint separated out when the water had almost completely evaporated.

The complex is highly soluble in water, less so in alcohol.

Analysis of the complex

Determination of zinc

Sample 0.2950 g; ZnS 0.0734 g; Zn 0.04923 g;
found Zn 16.69%; calculated Zn 16.62%.

Determination of chlorine

Sample 0.0938 g; AgNO₃ 0.1629 g; Cl 0.03401 g;
found Cl 36.25%; calculated Cl 36.06%.

4. Complex \([(C_5H_5N)_2C_2H_4]\cdot[CdCl_3]_2\)

It separated on mixing concentrated aqueous solutions of the components in the form of white, lustrous flakes. It does not melt at 250°. Soluble in water. On prolonged storage it turns slightly yellow.

Analysis of the complex

Determination of cadmium

Sample 0.1568 g; CdSO₄ 0.1046 g; Cd 0.05637 g;
found Cd 35.95%; calculated Cd 36.03%.

Determination of chlorine

Sample 0.1039 g; AgCl 0.1428 g; Cl 0.03532 g;
found Cl 34%; calculated Cl 34.1%.

5. Complex \([(C_5H_5N)_2C_2H_4]\cdot[CdBr_2Cl_2]\)

It was obtained by mixing concentrated aqueous solutions of the components, in the form of lustrous, small, well-formed white crystals with a pink tint. On long storage in a desiccator the surface becomes matte. It does not melt at 250°. Soluble in boiling water; sparingly soluble in alcohol.

Analysis of the complex

Determination of cadmium

Sample 0.2131 g; CdSO₄ 0.0837 g; Cd 0.0449 g;
found Cd 21.07%; calculated Cd 21.17%.

Determination of chlorine and bromine

Sample 0.1322 g; AgCl + AgBr 0.1649 g; converted to AgCl 0.1420 g;
AgBr 0.0939 g; Br 0.03996 g;
AgCl 0.0710 g; Cl 0.01756 g;
found Cl 13.28%; calculated Cl 13.40%.
Br 30.23%; Br 30.20%.

6. Complex \([(C_5H_5N)_2C_2H_4Cl_2]\cdot3HgCl_2\)

obtained by combining aqueous or alcoholic solutions of the components in the ratio 1:3. A white crystalline precipitate falls out, consisting of lustrous small flakes. Sparingly soluble in water and alcohol.

Analysis of the complex

Determination of mercury

Sample 0.1320 g; HgS 0.0886 g; Hg 0.07432 g;
found Hg 56.30%; calculated Hg 56.15%.

Determination of chlorine

Sample 0.2545 g; AgCl 0.2714 g; Cl 0.06713 g;
found Cl 26.37%; calculated Cl 26.46%.

When the complex is dissolved in dilute nitric acid, 13.31% chlorine is determined. Therefore it was necessary first to precipitate the mercury with hydrogen sulfide. The excess hydrogen sulfide was removed with copper sulfate, after which the chlorine was precipitated with silver nitrate.

7. Complex \([(C_5H_5N)_2 C_2H_4]\cdot[MnCl_4]''\)

It was obtained as a finely crystalline precipitate upon adding finely powdered manganese chloride to an alcoholic solution of ethylenepyridinium chloride. The complex is slightly yellowish, does not melt at 240°. It is readily soluble in water and sparingly soluble in alcohol.

Analysis of the complex

Determination of manganese

Sample 0.1944 g; MnSO₄ 0.0755 g; Mn 0.02747 g;
found Mn 14.13%; calculated Mn 14.08%.

Determination of chlorine by Volhard’s method

Sample 0.0654 g; AgNO₃ 0.1343 g; Cl 0.0239;
found Cl 36.67%; calculated Cl 37.03%.

From aqueous solutions of the components, after evaporation, the complex crystallized with 6 molecules of water in transparent long needles. The crystals readily lost water even on standing in a desiccator, becoming cloudy.

Determination of water of crystallization

Sample 2.8 g; weight of the dried complex 2.180 g; loss on drying 0.620 g;

\[ \frac{2.180\ \text{g} - 0.620}{382.95 \qquad X} \qquad X = 108.9\ \text{g},\ \text{i.e., 6 moles.} \]

Found H₂O 22.14%; calculated 22%.

8. Complex \([(C_5H_5N)_2 C_2H_4]\cdot[CoCl_4]''\)

Obtained by mixing aqueous solutions of the components, followed by evaporation of the mixture on a water bath until crystallization began. Small, well-formed blue crystals separated. The complex is somewhat hygroscopic. It is readily soluble in water and slightly soluble in alcohol.

Analysis of the complex

Determination of cobalt

Sample 0.1264 g; CoSO₄ 0.0505 g; Co 0.01921 g;
found Co 15.19%; calculated Co 15.23%.

Determination of chlorine

Sample 0.1185 g; AgCl 0.1747 g; Cl 0.0432 g;
found Cl 36.47%; calculated Cl 36.65%.

Complexes with chlorides of trivalent metals

These complexes were obtained in two types: \( \mathrm{R}\cdot[(\mathrm{MeOH})\mathrm{Cl}_4]'' \) and \( \mathrm{R}\cdot[\mathrm{MeCl}_5]'' \).

9. Complex \([( \mathrm{C}_5\mathrm{H}_5\mathrm{N})_2\mathrm{C}_2\mathrm{H}_4]\;[(\mathrm{BiOH})\mathrm{Cl}_4]\)

obtained by mixing an alcoholic solution of ethylenepyridinium chloride with an acidified solution of bismuth chloride, in the form of a white powdery precipitate. Heated to 169° it begins to darken and soften; then bubbles form in the softened mass and, finally, at 200° the substance blackens. It is sparingly soluble in water and alcohol. It dissolves in dilute hydrochloric and nitric acids. It contains no water of crystallization.

Analysis of the complex

Determination of bismuth

Sample 0.1450 g; Bi\(_2\)S\(_3\) 0.0675 g; Bi 0.05487 g;
found Bi 37.87%; calculated Bi 37.72%.

Determination of chlorine

Sample 0.1874 g; AgCl 0.1950 g; Cl 0.04822 g;
found Cl 25.74%; calculated Cl 25.61%.

10. Complex \([( \mathrm{C}_5\mathrm{H}_5\mathrm{N})_2\mathrm{C}_2\mathrm{H}_4]\;[\mathrm{BiCl}_5]\)

If the preceding complex is recrystallized from concentrated hydrochloric acid, thin, delicate white needles separate. Under the action of water the substance shows no noticeable hydrolysis. It is soluble in dilute hydrochloric and nitric acids.

Analysis of the complex

Determination of bismuth

Sample 0.1844 g; Bi\(_2\)S\(_3\) 0.0824 g; Bi 0.06698 g;
found Bi 36.33%; calculated Bi 36.51%.

Determination of chlorine by Volhard

Sample 0.0980 g; AgNO\(_3\) 0.14616 g; Cl 0.0305 g;
found Cl 31.06%; calculated Cl 30.96%.

11. Complex \([( \mathrm{C}_5\mathrm{H}_5\mathrm{N})_2\mathrm{C}_2\mathrm{H}_4]\;[(\mathrm{CrOH})\mathrm{Cl}_4]\cdot 2\mathrm{H}_2\mathrm{O}\)

Finely powdered chromium chloride was added, with stirring, to an alcoholic solution of ethylenepyridinium chloride, and the mixture was heated on a water bath until complete dissolution. The solution was evaporated strongly. The violet complex formed, after separation from the mother liquor, was pressed through filter paper and dried in a desiccator over sulfuric acid.

Analysis of the complex

Determination of water of crystallization

Sample, 1.5163 g; loss of water on heating, 0.1263 g; per mole of anhydrous salt there are 36.08 g of water, which corresponds to two moles.

Determination of chromium

Sample, 0.1202 g; Cr₂O₃, 0.0240 g; Cr, 0.01642 g;
found Cr, 13.66%; calculated Cr, 13.1%.

Determination of chlorine by Volhard

Sample, 0.1036 g; AgNO₃, 0.1730 g; Cl, 0.03611 g;
found Cl, 34.85%; calculated Cl, 35.73%.

12. Complex \([(C_5H_5N)_2C_2H_4]\,[CrCl_5]\cdot 2H_2O\)

obtained from the preceding one by recrystallizing it from concentrated hydrochloric acid. Dried in a desiccator over sulfuric acid. Contains two moles of water of crystallization. It was not possible to determine the melting temperature in capillaries. Both chromium complexes are readily soluble in water.

Analysis of the complex

Determination of water of crystallization

Sample, 1.4728 g; loss on heating, 0.1152 g;
found H₂O, 7.82%; calculated H₂O, 7.97%, which corresponds to two moles of water of crystallization.

Determination of chromium

Sample, 0.1272 g; Cr₂O₃, 0.0241 g; Cr, 0.01649 g;
found Cr, 12.96%; calculated Cr, 12.52%.

Determination of chlorine

Sample, 0.1056 g; AgCl, 0.1769 g; Cl, 0.04443 g;
found Cl, 42.16%; calculated Cl, 42.68%.

13. Complex \([(C_5H_5N)_2C_2H_4]\,[(FeOH)Cl_4]\)

is formed when finely ground ferric chloride is introduced into an acidified alcoholic solution of ethylenepyridinium chloride with careful stirring. A bright-orange powder with a melting temperature of 216.5° is obtained.

Analysis of the complex

Determination of iron

Sample, 0.6034 g; Fe₂O₃, 0.1209 g; Fe, 0.0845 g;
found Fe, 14.01%; calculated Fe, 13.94%.

Determination of chlorine

Sample 0.2582 g; AgCl 0.3698 g; Cl 0.0915 g;
found Cl 35.44%; calculated 35.39%.

14. Complex \([(C_5H_5N)_2C_2H_4][FeCl_5]\).

On recrystallization of the preceding compound from concentrated hydrochloric acid, the complex separated as a yellow crystalline precipitate, readily soluble in water.

Analysis of the yellow complex

Determination of iron

Sample 0.4143 g; Fe₂O₃ 0.0804 g; Fe 0.05622 g;
found Fe 13.57%; calculated Fe 13.31%.

Determination of chlorine

Sample 0.0888 g; AgCl 0.1508 g; Cl 0.3729 g;
found Cl 42.0%; calculated Cl 42.29%.

Conclusions

1. Complexes of the halides of certain metals with pyridine derivatives have been obtained and studied. The coordination number of most of them is 4. The general formula of their type \(R \cdot MeCl_4''\) may be represented structurally as follows:

\[ \begin{array}{c} \begin{array}{cc} \raisebox{0.5em}{\hexagon} & \raisebox{0.5em}{\hexagon} \end{array}\\[-0.2em] \mathrm{Cl{:}N{:}C_2H_4{:}N{:}Cl}\\ \diagdown\!\!\!\!\!\!\!\!\diagup\quad\diagdown\!\!\!\!\!\!\!\!\diagup\\[-0.4em] \mathrm{Me}\\ /\quad \backslash\\ \mathrm{Cl}\quad\mathrm{Cl} \end{array} \]

On the basis of analytical data, for some complexes it is necessary to assume a coordination number of 5.

1. The complexes of ethylenepyridinium chloride have a rather varied composition. Thus, cadmium chloride is added in the amount of two, and mercuric chloride in the amount of three moles per mole of organic substance. If the structure of the cadmium complex is taken as the following:

\[ \begin{array}{cc} \hexagon & \hexagon \\[-0.4em] \mathrm{Cl:N:C_2H_4:N:Cl} \\ \vdots \qquad\qquad \vdots \\ \mathrm{Cd} \quad \begin{matrix}\mathrm{Cl}\\[-0.2em]\diagdown\quad\diagup\\[-0.2em]\mathrm{C}\end{matrix} \quad \mathrm{Cd}\\ \vert \qquad\qquad \vert\\ \mathrm{Cl}\qquad\qquad \mathrm{Cl} \end{array} \]

and that of mercury by the structural formula:

\[ \begin{array}{c} \begin{array}{cc} \hexagon & \hexagon \end{array}\\[-0.4em] \mathrm{Cl:N:C_2H_4:N:Cl}\\ \vdots \qquad\qquad \vdots\\ (1)\ \mathrm{Cl{-}Hg{-}Cl{-}Hg{-}Cl{-}Hg{-}Cl}\ (4)\\ \phantom{(1)\ \mathrm{Cl{-}}\ } \vert \qquad\qquad\quad \vert\\ \phantom{(1)\ \mathrm{Cl{-}}\ }\mathrm{Cl}\qquad\qquad\quad \mathrm{Cl}\\ \phantom{(1)\ \mathrm{Cl{-}}\ }(2)\qquad\qquad\quad (3) \end{array} \]

then the coordination numbers of cadmium and mercury remain equal to four, and the fact is readily explained that, in determining chlorine in the mercury complex without its preliminary decomposition, only half the amount is precipitated; that is, only chlorines 1, 2, 3, and 4, located in the outer part, are ionogenic.

1. Compounds of ethylenepyridinium chloride with chlorides of trivalent metals have coordination number 5, and their structure may be represented as follows:

\[ \begin{array}{c} \begin{array}{cc} \hexagon & \hexagon \end{array}\\[-0.4em] \mathrm{Cl:N:C_2H_4:N:Cl}\\ \diagdown \qquad \diagup\\ \mathrm{Me}\\ /\quad |\quad \backslash\\ \mathrm{Cl}\quad \mathrm{Cl}\quad \mathrm{Cl} \end{array} \]

1. All complexes of this group possess a high melting point.

1. Almost all of the obtained compounds of metal halides with chloroethylpyridinium crystallize well.

2. The complexes with the halides of bismuth and mercury are sparingly soluble in water; the complexes with cadmium bromide and chloride are also poorly soluble. In absolute alcohol all the complexes are slightly soluble or almost insoluble, with the exception of the complex with copper bromide, which colors the alcohol yellow. The slight solubility of some complexes in commercial alcohol is explained by the presence of water in it.

Owing to the low solubility of the complexes described in absolute alcohol, it was not possible to determine the molecular weight by the ebullioscopic method or to measure the electrical conductivity with sufficient accuracy.

In acetone, the complexes with manganese and chromium chlorides dissolve well; considerably less well those with zinc chloride, iron chloride, and copper halides; the others are slightly soluble or almost insoluble.

It is necessary to note the fact that, when colored cobalt and copper complexes are dissolved in cold acetone, the former have a pale-pink color, which on boiling becomes blue; in the case of the copper complexes the cold solution in acetone is greenish and the hot one yellow.

On cooling, the original color reappears. This indicates that cold acetone, like water, splits the molecules of the complexes into their constituent components, which may be expressed by the following equations:

a) in hot acetone

\[ [(C_5H_5N)_2C_2H_4][CoCl_4] \rightleftarrows [(C_5H_5N)_2C_2H_4]^{\bullet\bullet} + [CoCl_4]^{\prime\prime} \]

blue ion,

b) in cold acetone

\[ [(C_5H_5N)_2C_2H_4][CoCl_4 \rightleftarrows [(C_5H_5N)_2C_2H_4Cl_2 + CoCl_2 \]

\[ CoCl_2 \rightleftarrows Co^{\bullet\bullet} + 2Cl^{\prime} \]

pink ion.

It is very possible that certain differences between ethylenepyridinium compounds and analogous complexes of other pyridine derivatives may be explained by the cyclic grouping arising around the chain —CH₂—CH₂—.

The great importance of cyclic groupings was noted by S. M. Jørgensen, A. Werner [1], and their role is substantiated in especially great detail by L. A. Chugaev in his work Investigations in the Field of Complex Compounds [4].

LITERATURE

1. Werner A. New Views in the Field of Inorganic Chemistry, ONTI, 1936; article by A. A. Grinberg, On the Nature of the Forces of Complex Formation, ONTI, pp. 385—386.
2. Davidsohn J. Ann. d. Chem. u. Pharm., 1862, 121, p. 255.
3. Sidgwick N. V. The Nature of the Bonds in Chemical Compounds, ONTI, 1936.
4. Chugaev L. A. Investigations in the Field of Complex Compounds, 1906, pp. 123—126.