Complex Compounds of Dinitrophenylpyridinium Chloride and Bromide with Mineral Salts

I. I. Molodykh

A survey of the literature showed that there are no descriptions of ternary complexes of metal halides with derivatives of tertiary heterocyclic amines complicated by nitro compounds of the benzene series.

In order to determine the possibility of the existence of compounds of this kind, dinitrophenylpyridinium chloride and bromide were prepared—substances sufficiently stable that they could be recrystallized from alcohol.

It was not possible to obtain analogous compounds with quinoline, since upon recrystallization they decomposed into their constituent components.

Dinitrophenylpyridinium chloride and bromide were prepared in the following way: chlorinated (brominated) dinitrobenzene was added in small portions, with stirring, to heated, freshly distilled pyridine, the components being taken in equimolecular amounts.

After complete dissolution, the cooling mixture crystallized upon vigorous shaking. The substances were recrystallized from alcohol.

The crystals of dinitrophenylpyridinium chloride, which separated in the form of fine needles, were separated from the mother liquor, pressed through filter paper, and dried in a desiccator over sulfuric acid. Their melting point was 178–180°.

The complex dissolves readily in water and acetone, and somewhat less readily in alcohol.

Determination of chlorine gave:

Sample 0.4263 g; AgCl 0.2155 g; Cl 0.0532 g.

Found Cl 12.48%; calculated Cl 12.51%, which indicates a compound of the components taken in a 1:1 molar ratio.

The structural formula of the compound obtained, according to the views of Lewis–Sidgwick, may be represented as follows:

\[ \begin{array}{c} \mathrm{NO_2}\\[-0.2em] \begin{array}{cc} \begin{array}{c} \large\text{pyridinium ring}\\[-0.2em] \mathrm{X:N} \end{array} \;:\; \begin{array}{c} \large\text{dinitrophenyl ring}\\[-0.2em] \mathrm{C}\\[-0.2em] \mathrm{NO_2} \end{array} \end{array} \end{array} \]

Complex compounds of dinitrophenylpyridinium chloride with metal halides

Dinitrophenylpyridinium chloride forms complex compounds with halides of various metals. The less soluble of these separate in the form of a viscous mass, which winds around a glass rod. Pro-

washed with water or alcohol, it solidifies, crystallizing in the form of needles or plates, while adhering tightly to the bottom of the crystallizer. With dinitrophenylpyridinium chloride the following complexes were obtained (Table 1).

Table 1

1. Complex \([C_5H_5NC_6H_3(NO_2)_2]_2CuCl_4\)

was obtained by mixing aqueous solutions of the components, calculated as two moles of dinitrophenylpyridinium chloride to one mole of copper chloride. Upon evaporation of the mixture to a small volume, a thick syrup was formed, from which, in a desiccator over sulfuric acid, a solid substance separated. The latter was suction-filtered, washed with cold alcohol, and, after drying, was subjected to analysis. The complex is amber-yellow in color, with a melting point of \(52^\circ\); it is readily soluble in water and acetone, and less so in alcohol.

Analysis of the complex

Determination of copper

Sample 0.1506 g; CuO 0.0174 g; Cu 0.0139 g;
found Cu 9.23%; calculated Cu 9.11%.

Determination of chlorine by Volhard

Sample 0.1032 g; AgNO\(_3\) 0.1008 g; Cl 0.2104 g;
found Cl 20.38%; calculated Cl 20.32%.

2. Complex \([C_5H_5NC_6H_3(NO_2)_2]AuCl_4\)

Separated in the form of a pale-yellow precipitate when aqueous solutions of the components, taken in a mole-to-mole ratio, were mixed. Melting point \(156^\circ\). Readily soluble in acetone, considerably less so in alcohol, and sparingly in water.

Analysis of the complex

Determination of gold

Sample 0.2934 g; Au 0.0981 g;
found Au 33.60%; calculated Au 33.67%.

Determination of chlorine by Volhard’s method

Sample 0.0736 g; AgNO₃ 0.0852 g; Cl 0.01778 g;
found Cl 24.16%; calculated Cl 24.23%.

3. Complex \([C_5H_5NC_6H_3(NO_2)_2]_2ZnCl_4\)

When concentrated aqueous solutions of dinitrophenylpyridinium chloride (2 moles) and zinc chloride (1 mole) were mixed, a film of a lemon-yellow substance formed. The solution was decanted into another crystallizer. On standing, a white transparent substance separated, with a melting point of 82°. The complex is readily soluble in acetone, water, and alcohol.

Analysis of the complex

Determination of zinc

Sample 0.4208 g; ZnO 0.0496 g; Zn 0.0398 g;
found Zn 9.45%; calculated Zn 9.35%.

Determination of chlorine by Volhard’s method

Sample 0.0920 g; AgNO₃ 0.0890 g; Cl 0.0186 g;
found Cl 20.19%; calculated Cl 20.23%.

4. Complex \([C_5H_5NC_6H_3(NO_2)_2]_2CdCl_4\)

When concentrated alcoholic solutions of the components were mixed in the ratio of 2 moles of dinitrophenylpyridinium to 1 mole of cadmium chloride, a thick, viscous, yellowish mass separated, which wound around a glass rod.

On washing with water, a small fraction of the complex dissolved. The resulting substance adhered firmly to the bottom and walls of the crystallizer. Dried in a desiccator over sulfuric acid, it partially crystallized. On melting, it first softens (45°), then melts at 65°. On further heating it bubbles and boils at 105°. It is sparingly soluble in water, readily soluble in acetone, and less readily in alcohol.

Analysis of the complex

Determination of cadmium

Sample 0.2280 g; CdSO₄ 0.0640 g; Cd 0.0346 g;
found Cd 15.17%; calculated Cd 15.06%.

Determination of chlorine by Volhard’s method

Sample 0.1336 g; AgNO₃ 0.12096 g; Cl 0.02524 g;
found Cl 18.86%; calculated Cl 19.0%.

5. Complex \([C_5H_5NC_6H_3(NO_2)_2]_2HgCl_4\)

When concentrated alcoholic solutions of the components were mixed, at first a small amount of a viscous substance separated. With time, on standing in a desiccator, a white substance formed with a melting point of \(60^\circ\), sparingly soluble in hot water, more readily in alcohol, and readily in acetone.

Analysis of the complex

Determination of mercury

Sample \(0.2016\) g; \(HgS\) \(0.0546\) g; \(Hg\) \(0.04864\) g;
found \(Hg\) \(24.12\%\); calculated \(Hg\) \(24.02\%\).

Determination of chlorine

Sample \(0.1158\) g; \(AgCl\) \(0.0798\) g; \(Cl\) \(0.01973\) g;
found \(Cl\) \(17.03\%\); calculated \(Cl\) \(16.99\%\).

6. Complex \([C_5H_5NC_6H_3[(NO_2)_2]]AlCl_4 \cdot 2H_2O\)

was obtained by mixing concentrated solutions of the components in the ratio of 1 mole of the organic component to 1 mole of aluminum chloride, as a white, transparent, soft substance. Melting point \(179^\circ\). On heating in a thermostat at \(110^\circ\) it became canary-yellow. Readily soluble in water, acetone, and alcohol.

Analysis of the complex

Determination of water of crystallization

Sample \(4.1145\) g; after drying—\(3.7865\) g; loss of water \(0.3280\) g.
For \(414.9\) g there are \(35.94\) g of water, which corresponds to 2 molecules of water of crystallization.

Determination of aluminum

Sample \(0.2535\) g; \(Al_2O_3\) \(0.0315\) g; \(Al\) \(0.01678\) g;
found \(Al\) \(6.59\%\); calculated \(Al\) \(6.5\%\).

Determination of chlorine

Sample \(0.1245\) g; \(AgCl\) \(0.1722\) g; \(Cl\) \(0.0426\) g;
found \(Cl\) \(34.22\%\); calculated \(Cl\) \(34.18\%\).

7. Complex \([C_5H_5NC_6H_3(NO_2)_2]BiCl_4\)

separated as a white powdery substance with a pinkish tint when an alcoholic solution of dinitrophenylpyridinium chloride was poured together with a hydrochloric-acid solution of bismuth chloride. It was washed with acidified water and alcohol. It was calcined through filter paper. Dried in a desiccator over sulfuric acid. Its melting point is \(196^\circ\). On further heating it bubbles. It is almost insoluble in water, dissolves in hydrochloric and nitric acids, and also in acetone.

Analysis of the complex

Determination of bismuth

Sample 0.3064 g; Bi₂O₃ 0.1192 g; Bi 0.1069 g;
found Bi 34.89%; calculated Bi 35.01%.

Determination of chlorine

Owing to the low solubility of the complex in water, for the determination of chlorine the soda extract obtained by prolonged boiling of it with sodium carbonate was taken.

Sample 0.1602 g; AgCl 0.1548 g; Cl 0.0383 g;
found Cl 23.9%; calculated Cl 23.75%.

8. Complex \([ \mathrm{C_5H_5NC_6H_3(NO_2)_2} ]\mathrm{SbCl_4}\)

It was obtained by mixing a hydrochloric-acid solution of antimony chloride with an alcoholic solution of dinitrophenylpyridinium chloride, in the form of a white substance. It was washed with an alcoholic solution of hydrogen chloride and then with alcohol. Melting point 126°. It is almost insoluble in water, but undergoes hydrolysis. It is soluble in acetone and in hydrochloric acid, and considerably less so in nitric acid.

Analysis of the complex

Determination of antimony

Sample 0.2039 g; Sb₂S₃ 0.0682 g, Sb 0.0489 g;
found Sb 23.98%; calculated Sb 23.89%.

Determination of chlorine by Volhard

Sample 0.1280 g; AgNO₃ 0.1479 g; Cl 0.0309 g;
found Cl 24.14%; calculated Cl 27.83%.

The lowered percentage of chlorine is explained by the fact that, when the complex is washed with alcohol for sale, hydrolysis occurs, although to a slight extent, going as far as transformation of the complex into \([\mathrm{C_5H_5NC_6H_3(NO_2)_2}]\mathrm{ClSbOCl}\), as indicated by the determination of chlorine (11%) in the product obtained as a result of washing. On heating the latter above 200° it darkens, but even at 300° it does not melt. It can be melted only by introducing a capillary containing the substance directly into the flame of a Bunsen burner.

9. Complex \([ \mathrm{C_5H_5NC_6H_3(NO_2)_2} ]\mathrm{CrCl_4}\cdot 2\mathrm{H_2O}\)

It was obtained after the mixture of concentrated solutions of the components, taken in the ratio of 1 mole of dinitrophenylpyridinium chloride to one mole of chromium chloride, had stood for many days in a desiccator, in the form of violet plates. It is very hygroscopic. Absorbing moisture from the air, it turns into a green viscous mass. The melting point of the substance dried at 110° is about 181°. It is readily soluble in water, acetone, and alcohol.

Analysis of the complex

Determination of water of crystallization

Sample 2.3678 g; loss of water 0.1930 g;

\[ \begin{array}{cc} 2.3678 & 0.1930 \\ 439.95 & X \end{array} \qquad X = 35.87,\ \text{i.e., two molecules.} \]

Determination of chromium

Sample 0.2763 g; Cr₂O₃ 0.0480 g; Cr 0.03285 g; found Cr 11.9%; calculated Cr 11.82%.

Determination of chlorine by Volhard

Sample 0.1096 g; AgNO₃ 0.1688 g; Cl 0.0352 g; found Cl 32.11%; calculated Cl 32.23%.

10. Complex \([C_5H_5NC_6H_3(NO_2)_2]_2 MnCl_4\)

To a heated concentrated aqueous solution of dinitrophenylpyridinium chloride, finely ground manganese chloride was added with stirring. After brief heating on a water bath, the solution was placed in a desiccator over sulfuric acid. A light-yellow substance with a melting point of 50° formed. Above 50° the substance decomposes, evolving gas bubbles, and the molten complex rises up the capillary. It is readily soluble in water, less so in alcohol and acetone.

Analysis of the complex

Determination of manganese

Sample 0.3124 g; Mn₂P₂O₇ 0.0658 g; Mn 0.02544 g; found Mn 8.14%; calculated Mn 7.97%.

Determination of chlorine by Volhard

Sample 0.1088 g; AgNO₃ 0.1075 g; Cl 0.0224 g; found Cl 20.53%; calculated Cl 20.58%.

11. Complex \([C_5H_5N_6CH_3(NO_2)_2] FeCl_4\)

Finely divided iron chloride was introduced, in small portions and with stirring, into a concentrated alcoholic solution of dinitrophenylpyridinium chloride. At the bottom of the crystallizer, plates of a yellow substance formed, which, when rubbed with a glass rod, turned into a powder. Rubbing caused abundant crystallization. The substance dried in a desiccator over sulfuric acid had a melting point of 115° and was readily soluble in alcohol, acetone, and water.

Analysis of the complex

Determination of iron

Sample 0.3018 g; Fe₂O₃ 0.055 g; Fe 0.0385 g; found Fe 12.76%; calculated Fe 12.58%.

Determination of chlorine by Volhard

Sample 0.1452 g; AgNO₃ 0.2258 g; Cl 0.0471 g; found Cl 32.43%; calculated Cl 31.96%.

12. Complex \([C_5H_5NC_6H_3(NO_2)_2]_2\ CoCl_4\)

Concentrated aqueous solutions of the components in a ratio of 2 moles of the organic substance to 1 mole of cobalt chloride were mixed and evaporated on a water bath until a green color appeared.

After cooling, a dark-green substance separated. Dried in a desiccator over sulfuric acid, it had a melting point of 48°. It is readily soluble in alcohol and acetone, with a blue coloration; in water—with a pink coloration, which indicated decomposition of the complex. On treatment of the complex with KCNS, a bulky bright-green precipitate was obtained.

Analysis of the complex

Determination of cobalt

Sample 0,3115 g; \(CoSO_4\) 0,0694 g; Co 0,0264 g;
found Co 8,47%; calculated Co 8,41%.

Determination of chlorine by Volhard

Sample 0,1023 g; \(AgNO_3\) 0,1008 g; Cl 0,02103 g;
found Cl 20,56%; calculated Cl 20,46%.

Complex Compounds of Dinitrophenylpyridinium Bromide with Mineral Salts

Dinitrophenylpyridinium bromide was obtained analogously to the preceding compound, i.e., bromodinitrobenzene was added in small portions, with stirring, to heated freshly distilled pyridine, calculated as 1 mole of the former to 1 mole of the latter.

After cooling, pale-yellow crystals separated in the form of needles. The substance recrystallized from alcohol melted at 215°. It is soluble in alcohol, acetone, and water.

Determination of bromine

Sample 0,1080 g; \(AgNO_3\) 0,0566 g; Br 0,0266 g;
found Br 24,62%; calculated Br 24,52%.

The structural formula for the above compound is analogous to that given for dinitrophenylpyridinium chloride.

Complexes with Metal Halides

With dinitrophenylpyridinium bromide and halides of certain metals, the following complexes were obtained (see Table 2).

1. Complex \([C_5H_5NC_6H_3(NO_2)_2]_2[CuCl_2Br_2]\)

was obtained by mixing concentrated solutions of the components, followed by evaporation on a water bath until a black-brown film of the complex formed. After separation from the mother liquor, the substance was pressed through filter paper and dried in a desiccator over sulfuric acid. Melting point 67°. Readily soluble in acetone, water, and alcohol.

Analysis of the complex

Determination of copper

Sample 0.1383 g; CuO 0.0142 g; Cu 0.01134 g;
found Cu 8.2%; calculated Cu 8.08%.

Determination of chlorine and bromine

Sample 0.1580 g; AgCl + AgBr 0.1324 g; converted to AgCl 0.1146 g;
AgBr 0.0751 g; Br 0.03196 g; AgCl 0.0573 g; Cl 0.01418 g;
found Cl 8.97%; calculated Cl 9.02%;
found Br 20.23%; calculated Br 20.32%.

Table 2

2. Complex \([C_5H_5NC_6H_3(NO_2)_2]_2CuBr_4\).

To a concentrated aqueous solution of dinitrophenylpyridinium bromide, with stirring, copper bromide was added in the proportion of 2 moles of the former to 1 mole of the latter substance. The solution was evaporated on a water bath until a black film of the complex with a violet tint appeared on the surface. After cooling and separation from the mother liquor, the complex was pressed through filter paper and dried in a desiccator.

Analysis of the complex

Determination of copper

Sample 0.1772 g; Cu₂S 0.0158 g; Cu 0.01263 g;
found Cu 7.12%; calculated Cu 7.26%.

Determination of bromine by Folgard

Sample 0.1237 g; AgNO₃ 0.09576 g; Br 0.04504 g;
found Br 36.41%; calculated Br 36.52%.

3. Complex \([C_5H_5NC_6H_3(NO_2)_2]_2 CdJ_2Br_2\)

Separated in the form of a light-yellow, lustrous, viscous substance when saturated solutions of the components were mixed. On prolonged exposure to air it yellows at the surface. Washed with water and dried in a desiccator over sulfuric acid. Melting point 63°. Sparingly soluble in water.

Analysis of the complex

Determination of cadmium

Sample 0.2260 g; CdSO₄ 0.0468 g; Cd 0.02522 g;
found Cd 11.15%; calculated Cd 11.04%.

Determination of bromine and iodine

Sample 0.1052 g; AgBr 0.0390 g; Br 0.018275 g;
found Br 15.78%; calculated Br 15.75%.

Sample 0.0960 g; AgJ + AgBr 0.0428 g; AgJ 0.0532 g; J 0.02876 g;
found J 24.87%; calculated J 24.94%.

4. Complex \([C_5H_5NC_6H_3(NO_2)_2]_2 HgCl_2Br_2\)

Separated in the form of a slightly yellowish precipitate. Melting point 85°. Sparingly soluble in cold water, readily soluble in acetone, considerably less so in alcohol.

Analysis of the complex

Determination of mercury

Sample 0.1186 g; Hg₂Cl₂ 0.0300 g; Hg 0.0255 g;
found Hg 21.50%; calculated Hg 21.72%.

Determination of bromine and chlorine

Sample 0.1837 g; AgCl + AgBr 0.1325 g; converted to AgCl 0.1147 g;
AgBr 0.0751 g; Br 0.03196 g; AgCl 0.0574 g; Cl 0.0142 g;
found Cl 7.73%; calculated Cl 7.68%;
found Br 17.40%, calculated Br 17.31%.

5. Complex \([C_5H_5NC_6H_3(NO_2)_2]\ AlCl_3Br \cdot 2H_2O\)

Finely powdered aluminum chloride was introduced into a concentrated solution of dinitrophenylpyridinium bromide with continuous stirring; the solution was heated until thickened and placed in a desiccator over sulfuric acid.

After prolonged standing, a light-yellow complex separated. It is very hygroscopic. Readily soluble in water and alcohol, considerably less readily in acetone. At 185° it softens; at 260° it turns white, becomes powdery, and when the capillary is tapped it shakes down to the bottom. If the sulfuric acid is first heated to 110°, and the thermometer with the capillary is then lowered into it, the complex melts at 156°, with vigorous decomposition and evolution of gas.

Analysis of the complex

Determination of water of crystallization

Sample 1.3710 g; weight of dried substance 1.2710 g; loss of water 0.1000 g;

For 1 mole, 36.14 g of water, i.e., 2 molecules.

Determination of aluminum

Sample 0.0950 g; Al₂O₃ 0.0104 g; Al 0.00549 g;
found Al 5.78%; calculated Al 5.87%.

Determination of bromine and chlorine

Sample 0.0914 g; AgCl + AgBr 0.1236 g; AgCl 0.1147 g; AgBr 0.0376 g;
Br 0.0161 g; AgCl 0.0860 g; Cl 0.0212 g;
found Br 17.56%; calculated Br 17.40%;
Cl 23.19%; Cl 23.15%.

6. Complex \([ \mathrm{C_5H_5NC_6H_3(NO_2)_2} ] \mathrm{BiCl_3Br}\)

It separated in the form of a white precipitate upon addition of a hydrochloric-acid solution of bismuth chloride to an alcoholic solution of dinitrophenylpyridinium bromide. It was washed with alcohol through which hydrogen chloride had been passed, and with pure alcohol. It was dried in a desiccator. Melting point 122°.

Analysis of the complex

Determination of bismuth

Sample 0.0974 g; Bi₂O₃ 0.0356 g; Bi 0.03193 g;
found Bi 32.78%; calculated Bi 32.58%.

Determination of chlorine and bromine

Sample 0.2974 g; AgCl + AgBr 0.2848 g; converted to AgCl 0.2632 g;
AgBr 0.0867 g; Br 0.0369 g; AgCl 0.1981 g; Cl 0.0490 g;
found Br 12.41%; calculated Br 12.46%;
Cl 16.47%; Cl 16.58%.

7. Complex \([ \mathrm{C_5H_5NC_6H_3(NO_2)_2} ] \mathrm{SbCl_3Br}\)

It separated in the form of a white precipitate when a concentrated alcoholic solution of the organic component was mixed with a hydrochloric-acid solution of antimony chloride. After suction filtration and washing with alcohol saturated with hydrogen chloride and with pure alcohol, it was dried in a desiccator. Melting point 112°.

Analysis of the complex

Determination of antimony

Sample 0.1057 g; Sb₂S₃ 0.0326 g; Sb 0.02337 g;
found Sb 22.11%; calculated Sb 21.97%.

Determination of bromine and chlorine

Sample 0,1132 g; AgCl + AgBr 0,1260 g; converted to AgCl 0,1171 g;
AgBr 0,03851 g; Br 0,01637 g; AgCl 0,0875 g; Cl 0,02164 g;
found Br 14,47%; calculated Br 14,42%;
Cl 19,12%; Cl 19,20%.

8. Complex \([C_5H_5NC_6H_3(NO_2)_2]_2 MnCl_2Br_2\)

To a heated saturated solution of dinitrophenylpyridinium bromide, finely powdered manganese chloride was added in small portions with stirring. After prolonged standing in a desiccator over sulfuric acid, a yellow substance separated, with a melting point of 48°. The complex is readily soluble in acetone and water, and somewhat less readily in alcohol.

Analysis of the complex

Determination of manganese

Sample 0,3024 g; MnSO₄ 0,0580 g; Mn 0,0211 g;
found Mn 8,98%; calculated Mn 7,06%.

Determination of chlorine and bromine

Sample 0,2314 g; AgCl + AgBr 0,1987 g; converted to AgCl 0,1720 g;
AgBr 0,1147 g; Br 0,04795 g; AgCl 0,0860 g; Cl 0,02127 g;
found Br 20,72%; calculated Br 20,55%;
Cl 9,19%; Cl 9,11%.

9. Complex \([C_5H_5NC_6H_3(NO_2)_2]FeCl_3Br\)

It was obtained by mixing saturated solutions of the components in a 1:1 ratio and subsequently heating on a water bath until crystals appeared. A brownish-red substance separated, having a melting point of 135°. It is readily soluble in acetone, water, and alcohol.

Analysis of the complex

Determination of iron

Sample 0,2988 g; Fe₂O₃ 0,0494 g; Fe 0,03952 g;
found Fe 11,55%; calculated Fe 11,44%.

Determination of chlorine and bromine

Sample 0,1516 g; AgCl + AgBr 0,1915 g; converted to AgCl 0,1776 g;
AgBr 0,05856 g; Br 0,02492 g; AgCl 0,1329 g; Cl 0,03287 g;
found Br 16,44%; calculated Br 16,37%;
Cl 21,68%; Cl 21,79%.

10. Complex \([C_5H_5NC_6H_3(NO_2)_2]_2 CoCl_2Br_2\)

To a heated saturated solution of dinitrophenylpyridinium bromide, finely powdered cobalt chloride was added in small portions with stirring. After standing in a desiccator over sulfuric acid, a green complex formed, with a melting point of 60°. It dissolves well in acetone, water, and alcohol.

Analysis of the complex

Determination of cobalt

Sample 0.3147 g; CoSO₄ 0.0620 g; Co 0.0235 g;
found Co 7.46%; calculated Co 7.54%.

Determination of bromine and chlorine

Sample 0.1968 g; AgCl + AgBr 0.1656 g; converted to AgCl 0.1434 g;
AgBr 0.0937; Br 0.03987 g; AgCl 0.0719 g; Cl 0.0178 g;
found Br 20.26%; calculated Br 20.44%;
Cl 9.04%; Cl 9.07%.

11. Complex \([C_5H_5NC_6H_3(NO_2)_2]_2NiCl_2Br_2\)

When saturated solutions of the components are mixed and heated in a water bath, a syrup-like mass is formed which, after prolonged standing in a desiccator over sulfuric acid, yields green crystals. The substance is hygroscopic. Melting point 56°. Readily soluble in water and alcohol, somewhat less readily in acetone.

Analysis of the complex

Determination of nickel

Before the determination, the complex was decomposed and the nickel was converted into sulfate.

Sample 0.2396 g; NiO 0.0224 g; Ni 0.0176 g;
found Ni 7.34%; calculated Ni 7.50%.

Determination of bromine and chlorine

Sample 0.1595 g; AgCl + AgBr 0.1327 g; converted to AgCl 0.1152 g;
AgBr 0.0752 g; Br 0.0320 g; AgCl 0.0575 g; Cl 0.01422 g;
found Br 20.06%; calculated Br 20.45%;
Cl 8.91%; Cl 9.07%.

Conclusions

1. Complex compounds of the halides of certain metals with chloro- and bromodinitrophenylpyridinium have been obtained and studied, of the composition \(R_2 \cdot MeX'_4\) and \(R' \cdot MX'_4\).

2. The coordination number of the substances obtained is 4. Therefore, on the basis of the views of Lewis–Sidgwick (1, 2, 5), for complexes with halides of divalent metals one may adopt a structural formula of the following type:

\[ \begin{array}{ccc} \begin{array}{c} \mathrm{NO_2}\\[-2pt] /\!\!\backslash\\[-2pt] \text{dinitrophenyl ring}\\[-2pt] \mathrm{NO_2}\quad C : N \end{array} & :\!X\!:\!Me\!:\!X\!: \atop :\!X\!: & \begin{array}{c} \mathrm{NO_2}\\[-2pt] /\!\!\backslash\\[-2pt] \text{dinitrophenyl ring}\\[-2pt] N : C\quad \mathrm{NO_2} \end{array} \end{array} \]

For complexes with halides of trivalent metals, the structure of their molecules may be represented as follows:

\[ \begin{array}{c} \mathrm{NO_2}\\[-0.2em] \begin{array}{cc} \mathrm{NO_2} & \\ \text{benzene ring} & \text{pyridine ring} \end{array} \quad \mathrm{C:N{:}\ \ :X{:}Me{:}X:}\\[-0.2em] \hspace{8.5em}\mathrm{:X:} \end{array} \]

1. In the preparation of the above-described compounds, a resinous viscous mass is first obtained, which adheres firmly to the glass. Crystallization takes place after a more or less prolonged standing in a desiccator over sulfuric acid.

2. Most of the complexes of this group are readily fusible. Some are hygroscopic.

The viscosity and ready fusibility may be explained by the presence of two nitro groups in the organic part of the molecule, since, in the absence of nitro groups in the benzene ring, analogous compounds crystallize well and have considerably higher melting points [2, 3].

1. The complexes with bismuth and mercury chlorides, as well as with cadmium iodide, are sparingly soluble in water.

LITERATURE

1. Werner A. New Views in the Field of Inorganic Chemistry. Article by A. A. Grinberg, “On the Nature of the Forces of Complex Formation,” ONTI, Leningrad, pp. 385–386, 1936.

2. Mikhailenko Ya. I. (Molodykh I. I., Zvorykina N. A., et al.). ZhRFKhO, vol. 61, pp. 257–267, 1929.

3. Molodykh I. I. Proceedings of the Tomsk Industrial Institute, vol. 55, pp. 305–308, 1936.

4. Nekrasov B. N. Course of General Chemistry, vol. 1, p. 313, ONTI, 1935.

5. Sidgwick N. V. The Nature of the Bonds in Chemical Compounds, ONTI, p. 141, 1936.