Conversions of coordinated ligands by reducing thermolysis of some double complex compounds

Article abstract of DOI:10.1134/S0036023610050128

Thermal decomposition of binary complexes [M(NH₃) _k]_x[M'L_n]_y (M = Ni, Co; M' = Fe, Cr, Cu; L = CN-, SCN^-, C₂O₄^{2 -}) in a hydrogen atmosphere showed conversion of coordinated CN-groups into ammonia and hydrocarbons; SCN-into ammonia, hydrogen sulfide, and hydrocarbons; and C ₂O₄^{2 -} into hydrocarbons and CO₂. In all cases, methane prevails in the resulting hydrocarbons; ethylene is the second in relative yield, which however strongly depends on the temperature and combination of the central ions of double complex salts. The yield of ethylene is especially high from the reduction of Co-Fe complexes at 350°C, Co ₄-Fe₃ complexes at 500°C, Ni₃-Fe ₂ and Ni₃-Cr₂ complexes at 350°C. The observed conversions of coordinated groups can be interpreted as arising from the catalytic effect caused by the reduced forms of the central atoms in the binary complexes to the interaction of ligands with hydrogen. Pleiades Publishing, Ltd., 2010.

Full text of DOI:10.1134/S0036023610050128

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2010, Vol. 55, No. 5, pp. 734–738. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © S.I. Pechenyuk, D.P. Domonov, A.A. Avedisyan, S.V. Ikorskii, 2010, published in Zhurnal Neorganicheskoi Khimii, 2010, Vol. 55, No. 5, pp. 788–792.
COORDINATION COMPOUNDS
Conversions of Coordinated Ligands by Reducing Thermolysis
of Some Double Complex Compounds
a
a
b
b
S. I. Pechenyuk , D. P. Domonov , A. A. Avedisyan , and S. V. Ikorskii
a
Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, Kola Research Center,
Russian Academy of Sciences, Apatity, Murmansk oblast, Russia
Institute of Geology, Kola Research Center, Russian Academy of Sciences, Apatity, Murmansk oblast, Russia
b
Received October 30, 2008
Abstract—Thermal decomposition of binary complexes [M(NH ) ] [M'L ] (M = Ni, Co; M' = Fe, Cr, Cu;
3
k x
n y
2
4
–
L = CN , SCN , C O ) in a hydrogen atmosphere showed conversion of coordinated CN– groups into
–
–
2
2
–
ammonia and hydrocarbons; SCN– into ammonia, hydrogen sulfide, and hydrocarbons; and C O into
2
4
hydrocarbons and CO2. In all cases, methane prevails in the resulting hydrocarbons; ethylene is the second
in relative yield, which however strongly depends on the temperature and combination of the central ions of
double complex salts. The yield of ethylene is especially high from the reduction of Co–Fe complexes at
350
°
C, Co –Fe complexes at 500
°
C, Ni –Fe2 and Ni –Cr2 complexes at 350 C. The observed conversions
°
4
3
3
3
of coordinated groups can be interpreted as arising from the catalytic effect caused by the reduced forms of
the central atoms in the binary complexes to the interaction of ligands with hydrogen.
DOI: 10.1134/S0036023610050128
We have earlier synthesized a series of double comꢀ was purified by passing consequtively through concenꢀ
plex salts (DCS) of 3d metals [1, 2] and studied their trated sodium hydroxide and concentrated sulfuric
thermal decomposition in oxidizing (air) and reducing acid solutions. The reactor with a weighed portion of
(
hydrogen) atmospheres [3–7]. We found that therꢀ DCS placed in a corundum boat was purged with
molysis in hydrogen atmosphere converted the DCS hydrogen before the start of heating, in the course of
central ions, depending on their nature and the nature heating to the given temperature, and during exposure
of coordinated ligands, into CoFe intermetallic comꢀ at the this temperature. The furnace heating rate was
pounds [3], Co + Cu heterogeneous mixture [4], NiFe 10 K/min, and the hydrogen flow rate was 10 to
[
5], Co + Cr O mixture [6], or metal and sulfide [5, 15 L/h. We used the temperatures of 200, 350, 500,
2 3
7
]. We noted that coordinated ligands were also conꢀ 700, and 900
°С
. The duration of exposure at the conꢀ
and 1 h at other
sphere conversions of coordinated ligands making our temperatures. The solid products of thermolysis were
verted. There are virtually no references to the innerꢀ stant temperature was 2 h at 200°С
data especially interesting.
cooled also in a hydrogen flow.
This work contains the results of our experimental
The gas products of DCS thermal reduction were
studies on conversions of coordinated ligands by therꢀ trapped by three seriesꢀconnected vessels passed by the
mal reduction (hydrogenation) of DCS having the flow of gases leaving the reactor. The first vessel was a
composition of [M(NH ) ] [M'L ] (M = Ni, Co; Drexel bottle filled with 1 M HCl solution and served
3
k x
n y
2
–
to trap volatile basic products. The second vessel was a
Drexel bottle to trap acid products; it contained 1 M
NaOH solution for cyanide and oxalate complexes
–
–
M' = Fe, Cr, Cu; L = CN , SCN , C O4 ).
2
and 0.05 M Zn(CH COO)2 solution for thiocyanates.
The third vessel was a bottle with concentrated NaCl
solution to trap neutral gas products.
3
EXPERIMENTAL
We have earlier described the synthesis and properꢀ
ties of the relevant DCS [1–7]. Thermal decomposiꢀ
We found that the only nitrogenꢀcontaining gas
tion of DCS was carried out with a setup [8] consisting product in all cases was ammonia, which was comꢀ
of a flowꢀthrough reactor in the form of a quartz tube pletely absorbed with hydrochloric acid solutions,
inserted into a SNOL 0.2/1250 electric furnace with a where it was determined in the form of ammonium
regulated heating rate. Hydrogen was produced by the cations by the Kjeldahl method. Table 1 gives examꢀ
reaction of hydrochloric acid with zinc metal, which plary of quantitative data. In the case of thiocyanate
was carried out in two vessels interconnected like the complexes, zinc acetate solution precipitated sulfide
Kipp apparatus. Before feeding the reactor, hydrogen ZnS, which was filtered off, washed, annealed at
734

CONVERSIONS OF COORDINATED LIGANDS
735
Table 1. Quantities of nitrogen released in the form of ammonia by thermal decomposition of DCS
Found
NH +4 quanꢀ
tity, g*
Reduction temꢀ Calculated N DCSweighed
DCS composition
Found N
quantity, wt %
perature, °C contents, wt % portion, g
3
50
00
0.450
0.449
0.248
0.260
42.9
45.1
[
Co(NH ) ][Fe(CN) ]
45.1
39.6
3
6
6
5
3
50
00
0.346
0.427
0.168
0.218
37.8
39.7
[Co(NH ) ] [Fe(CN) ] · 11.5H O
3
6 4
6 3
2
5
5
00
1.072
0.989
0.939
0.324
0.356
0.338
23.5
28.0
28.0
[
Co(NH ) ][Cr(NCS) ] · 2H O
700
28.1
3
6
6
2
900
3
50
00
1.344
1.982
0.269
0.403
15.6
15.8
[
Co(NH ) ][Cr(C O ) ] · 3H O
15.8
18.9
3
6
2
4 3
2
5
3
50
00
0.473
1.028
0.112
0.244
18.4
18.5
2
[Co(NH ) ] [Cu(C O ) ] · [Co(NH ) ] (C O )
3 6 2 2 4 2 3 3 6 2 2 4 3
5
3
50
1.227
1.457
1.295
0.582
0.614
0.580
36.9
32.8
34.8
[
Ni(NH ) ] [Fe(CN) ]
500
46.4
32.8
3
6 3
6 2
7
00
50
3
0.749
0.706
0.751
0.136
0.266
0.322
14.1
29.3
33.3
[
Ni(NH ) ] [Cr(NCS) ]
500
00
3
6 3
6 2
7
*
N/NH recalculation factor is 0.778.
4
Table 2. Quantities of sulfur released in the form of hydrogen sulfide by thermal decomposition of DCS
Reduction
temperature, °C contents, wt %
Calculated S
DCS weighed
portion, g
Found S
quantity, g
Found S
quantity, wt %
DCS composition
5
00
1.072
0.989
0.939
0.125
0.190
0.181
11.6
19.2
19.3
[
Co(NH ) ][Cr(NCS) ] · 2H O
700
32.2
32.8
3
6
6
2
900
350
500
700
900
0.749
0.706
0.751
0.661
0.038
0.044
0.067
0.065
5.1
6.3
8.9
9.8
[
Ni(NH ) ] [Cr(NCS) ]
6 2
3
6 3
900°С, and weighed in the form of ZnO to calculate
RESULTS AND DISCUSSION
the quantity of precipitated sulfur according to [9]
Table 2). The alkaline solution resulting from reducꢀ
tion of oxalate DCS with excess BaCl2 solution preꢀ
cipitated BaCO3, which was also filtered off, washed
Tables 1 and 5 show that, if the solid products of
DCS reduction are metal phases (intermetallics, with
exception of NiFe, or metals), sulfides, or oxides, then
nitrogen is released from compounds in the form of
ammonia (coordinated ammonia + nitrogen of acido
ligands). The lack of releasing nitrogen observed in the
case of FeNi should be explained by formation of
nitrides in the intermetallic phase [10], because the
weight of the residue after annealing always signifiꢀ
cantly exceeds the weight of the residue corresponding
(
with water, annealed at 700°С, and use to calculate the
quantity of released СО2 (Table 3). The gas mixture
containing hydrogen as the major component, which
was collected over NaCl solution, was analyzed with a
Tsvet 102 chromatograph. Table 4 displays analytical
results for these gas mixtures. The solid reduction
products were identified earlier [3–7]. Table 5 conꢀ to the pure intermetallic [5]. Such incomplete release
tains the characteristics of these solid reduction prodꢀ of nitrogen for almost all of the DCS studied at 350
ucts for convenience of discussion. seems to be due to an incomplete decomposition of
°С
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 5 2010

736
PECHENYUK et al.
Table 3. Quantities of CO released in the form of hydrogen sulfide by thermal decomposition of DCS
2
Reduction temꢀ Calculated CO DCSweighed Found CO Released
2
2
DCS composition
perature, °C contents, wt % portion, g quantity, g CO , wt %
2
3
5
7
9
50
00
00
00
1.344
1.982
1.809
2.421
0.273
0.654
0.605
0.813
20.3
33.0
33.4
33.6
[
Co(NH ) ][Cr(C O ) ] · 3H O
49.7
49.5
3
6
2
4 3
2
350
00
0.473
1.028
0.127
0.315
26.8
30.6
2
[Co(NH ) ] [Cu(C O ) ] · [Co(NH ) ] (C O )
3 6 2 2 4 2 3 3 6 2 2 4 3
5
Table 4. Analysis of the hydrocarbon mixture released by thermal decomposition of DCS
Reduction temꢀ
perature, °C
DCS composition
Ratio of hydrocarbon components in gas mixture
CH : C H : C H : C H : C H : ꢀC H = 40 : 17 : 3 : 18 : 1 : 3
3
50
00
n
8
4
2
4
2
6
3
6
3
4
10
[
Co(NH ) ][Fe(CN) ]
3
6
6
5
CH : C H = 43 : 1
4
2
4
350
CH : C H : C H : C H : C H :
i
ꢀC H :
α
ꢀC H :
n
ꢀC H :
β
ꢀC H =
4
2
4
2
6
3
6
3
8
4
10
4
8
4
10
4
8
1763 : 84 : 222 : 119 : 47 : 1 : 11 : 8 : 11
[
1
Co(NH ) ] [Fe(CN) ] ·
3 6 4 6 3
1.5H O
2
500
CH : C H : C H : C H : C H :
i
ꢀC H :
α
ꢀC H =
4
2
4
2
6
3
6
3
8
4
10
4
8
7677 : 4108 : 74 : 53 : 19 : 1 : 10
500
CH : C H : C H : C H = 34 : 4 : 1 : 1
[
Co(NH ) ][Cr(SCN) ] ·
4
2
4
2
6
3
6
3
6
6
2
H O
2
700
CH : C H : C H : C H = 78 : 7 : 2 : 1
4 2 4 2 6 3 6
3
5
7
50
00
00
CH : C H = 35 : 1
4 2 4
[
3
Co(NH ) ][Cr(C O ) ] ·
3 6 2 4 3
CH : C H : C H : C H :
α
α
ꢀC H :
n
ꢀC H = 3443 : 11 : 10 : 12 : 2 : 2
4
2
6
3
6
3
8
4
8
4
10
H O
2
CH4
350
CH : C H : C H : C H :
ꢀC H = 14306 : 135 : 5 : 11 : 1
2
[Co(NH ) ] [Cu(C O ) ] ·
4
2
6
3
6
3
8
4
8
3
6 2
2 4 2 3
[
Co(NH ) ] (C O )
3 6 2 2 4 3
500
CH : C H : C H : C H = 1190 : 17 : 1 : 6
4 2 6 3 6 3 8
350
CH : C H : C H : C H : C H :
i
ꢀC H :
α
ꢀC H :
n
ꢀC H : βꢀC H :
4
2
4
2
6
3
6
3
8
4
10
4
8
4
10
4 8
i
ꢀC H : nꢀC H = 7368 : 595 : 145 : 473 : 26 : 1 : 75 : 7 : 18 : 6 : 2
5 12 5 12
[
Ni(NH ) ] [Fe(CN) ]
6 2
3
6 3
5
00
00
CH : C H : C H : C H : C H = 5990 : 6 : 6 : 4 : 1
4 2 4 2 6 3 6 3 8
7
CH : C H = 4909 : 1
4
2
4
350
CH : C H : C H : C H : C H = 151 : 74 : 16 : 11 : 1
4 2 4 2 6 3 6 3 8
[
Ni(NH ) ] [Cr(NCS) ]
500
00
CH : C H : C H : C H = 28 : 5 : 1 : 1
4 2 4 2 6 3 6
3
6 3
6 2
7
CH : C H : C H = 54 : 1 : 1
4 2 4 2 6
DCS at this temperature in 1 h. Therefore, if nitrogen [Со(NH ) ][Cr(NСS) ] · 2H O complex, hydrogen
3
6
6
2
in coordinated cyano and thiocyano groups does not sulfide is released also because of its probable formaꢀ
remain in the solid reduction products, it is completely tion by the conversion of CoCr2S4 into cobalt metal
converted into ammonia as in the catalytic reduction
of nitriles with hydrogen to secondary amines [11].
and chromium sulfide [7]. As a result, up to 19% of
sulfur is released from the complex in the form of H2S
In the case of [Ni(NH ) ] [Cr(NСS) ] complex [5],
.
Under the said conditions, sulfur contained in
thiocyano groups (Table 2) is converted into sulfide
ions, which are partially consumed in the formation of
metal sulfides and partially released in the form of
3 6 3
6 2
two sulfides (Ni3S and NiCr2S4) were detected in the
2
products of reduction at 500 to 900°C (Table 5) along
with a lot of an amorphous phase, which also prevents
hydrogen sulfide. It is rather difficult to make up the us from making up the balance. The sulfur content in
balance of sulfur because several sulfides of various the solid residue from the reducing thermolysis of
compositions are formed. In the case of [Ni(NH ) ] [Cr(NСS) ] gradually decreases with
3
6 3
6 2
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 5 2010

CONVERSIONS OF COORDINATED LIGANDS
Table 5. Composition of solid products from reducing thermolysis of DCS
737
Decomposition
temperature, °C
DCS composition
Co(NH ) ][Fe(CN) ]
Solid phase composition
[
350, 500
350, 500
CoFe
3
6
6
[
Co(NH ) ] [Fe(CN) ] · 11.5H O
The same
Co, Cu
3
6 4
6 3
2
2
[Co(NH ) ] [Cu(C O ) ] · [Co(NH ) ] (C O ) 350, 500
3 6 2 2 4 2 3 3 6 2 2 4 3
5
00
700
00
CoCr S , Cr S , Cr S
2 4 2 5 2 3
[
Co(NH ) ][Cr(NCS) ] · 2H O
CoCr S , Cr S , Cr S , Co(cub.)
2 4 2 5 2 3
3
6
6
2
9
CoCr S , Cr S , Cr S , Co(cub.), Co(hex.), Cr(cub.)
2 4 2 5 2 3
[
Co(NH ) ][Cr(C O ) ] · 3H O
700, 900
Co, Cr O
3
6
2
4 3
2
2
3
[
Ni(NH ) ] [Fe(CN) ]
350, 500, 700
NiFe
3
6 3
6 2
3
50
Ni(NH ) (NCS) , NiSO + amorphous phase
3 2 2 4
[
Ni(NH ) ] [Cr(N
С
S) ]
3
6 3
6 2
500, 700, 900
Ni S , NiCr S
3 2 2 4
increasing temperature from 32.2% at 700
at 900
[5]. Both values are smaller than the sulfur enhance relative yields of methane.
content in a 2Ni S + 3NiCr S stoichiometric mixture
°С to 27.7% containing copper. Higher thermolysis temperatures
°С
3
2
2 4
The above results agree well with those of [12],
(
[
37.9%), which should be formed by reduction of
Ni(NH ) ] [Cr(NСS)6]2. Apparently, the amorphous
phase consists of nonstoiciometric nickel and chroꢀ
where [Со(NH ) ][Fe(CN)6] complex was used for
3
6
3
6 3
the preparation of mixed (aluminaꢀbased) CoFe
bimetal Fischer–Tropsch catalyst, which was therꢀ
mally reduced with hydrogen at 350°С before use.
mium sulfides.
This catalyst was found to shift essentially the course
of the Fischer–Tropsch reaction to the preferential
formation of unsaturated hydrocarbons (mainly, proꢀ
pylene). Because thermal decomposition of this BSC
yields CoFe intermetallic, it seems to be able even in
the course of its formation to catalyze the hydrogeꢀ
nation of coordinated ligands also with a significant
yield of lower unsaturated hydrocarbons. A similar
effect is produced by CoFe intermetallic with a
slight excess of Co, which is formed by reduction of
The thermal reduction of oxalate complexes results
in simultaneous release of carbon dioxide and hydroꢀ
carbons (Tables 3, 4), and the yield of СО2 is higher at
a higher thermolysis temperature. Like in some other
cases, at 350°С we still observe an incomplete decomꢀ
position of oxalate complexes. But at higher temperaꢀ
tures we see that coordinated oxalate ions are partially
(
~2/3) decomposed into СО2 and partially reduced to
methane and insignificant quantities of other hydroꢀ
carbons (Table 4).
[
Со(NH ) ] [Fe(CN) ] · 11.5H O. It is interesting that
3 6 4 6 3 2
Our analysis of the hydrocarbon (HC) gas mixture almost the same mixture of hydrocarbon products is
produced in all the cases by reducing thermolysis of formed by the reduction of [Ni(NH [Cr(NCS)
)
]
] ,
6 2
3
6
3
the studied DCS showed that methane is the major though the solid product of this reduction contains a
mixture of chromium and nickel sulfides.
product from the reduction (hydrogenation) of the
coordinated ligands. In some cases, however, methane
is accompanied with noticeable quantities of other
hydrocarbons. For example, reduction of
CONCLUSIONS
[
Со(NH ) ][Fe(CN)6] at 350
°
С
yields approximately
the same total amounts of ethylene and propylene
methane : unsaturated HC = 40 : 35), while in reducꢀ
tion of [Со(NH ) ] [Fe(CN) ] · 11.5H O at 500
3
6
Thermal reduction of [M(NH ) ] [M'L ] DCS
3
k x
n y
–
–
(
M = Ni, Co; M' = Fe, Cr, Cu; L = CN , SCN ,
(
2
–
°С,
C O4 ) with hydrogen results in the innerꢀsphere
3
6 4
6 3
2
2
the total yield of ethylene and propylene exceeds oneꢀ
half of the methane yield (methane : unsaturated HC =
hydrogenation of the coordinated ligands virtually to
the maximum possible content of hydrogen and in the
1
.84 : 1). A close ratio of 151 : 85 is observed for the reduction of the central ions of these DCS or in the
products from reduction of [Ni(NH ) ] [Cr(NСS) ] at formation of their sulfides or oxides. This innerꢀsphere
3
6 3
6 2
3 °С. Finally, significant amounts of hydrocarbons are hydrogenation of ligands can be explained as arising
50
also observed in reduction of [Ni(NH ) ] [Fe(CN) ] at from the catalytic effect of the solid products of reducꢀ
3
6 3
6 2
350°С (methane : unsaturated HC ~ 7 : 1). In all other ing thermolysis, while the reduction of the central ions
cases, the total yield of nonꢀmethane hydrocarbons do and the hydrogenation of ligands take place simultaꢀ
not exceed 15% of the methane yield. The relative neously because the gas products are continuously
yield of methane is especially high in the case of DCS removed with the gas flow.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 5 2010

7
38
PECHENYUK et al.
7. S. I. Pechenyuk, D. P. Domonov, and A. T. Belyaevskii,
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RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 5 2010