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Metal perchlorate ammines: thermal and infrared studies
Thermochimicn
Acra, 15 (Z976) 257-260
cc:; Elscvier Scientific Publishing Company, Amsterdam - Printed in Be.Igium
Note
Metal
perchlorate
IL C PATIL
AND
ammines:
thermal
and infrared
studies
V. R. PAI VERNEKER
Departmennr qf Inorganic and PhysicaI Chemisfry, Bangalore(India)
in&n
Instirure of Science.
S. R. JAIN Departmenf
of Aeronaufics,
Indian Institute of Science, BangaIore-560012
(Irzdia)
(Rezeived C September :975)
While studying the ca*Mytic effect of transition metal perchlorate ammines on the therma1 decomposition of ammonium perchlorate’, the ignition characteristics of pure metal perchlorate ammines gave interesting results. On looking through the literature it was found that, whereas preparation and explosive properties of the metal perchlorate ammines have been described2-6, no detailed account of the nature of intermediates and products of decomposition of these meta perchlorate ammines are reported. In the present study we report, the preparation, infrared spectra and the thermal decomposition characteristics of some of the transition metal perchlorate ammines and their intermediates. EXPERIMENTAL
The metal perchlorate hexahydrates were prepared by the reaction of metal carbonates, oxides or hydroxides with 60% perchloric acid and the perchlorate salts were crystallised from water and washed with chloroform. The metal perchlorate ammines were prepared as reported earIier2*‘, by &king -2 g of the freshIy prepared hexahydrate with -25 ml of anhydrous liquid ammonia. The detaik of the experimental set-up are described elsewhere’. DifZerential thermal analysis (DTA) and thermogravimetry (TG) units employed were similar to those described earlier’. Al1 experiments were done in air_ Heating rates employed were 12 “C n-k-’ for DTA and 5°C min- ’ in the case of TG. PIatinum cups were used as sample holders in DTA experiments. Since the metal perchIorate ammines are highly explosive the amount of the sample used was restricted to t30 mg. Infrared spectra were recorded on a Carl-Zeiss Jena U-R-10 double beam infrared spectrophotometer using KBr pellets as well as Nujol mulls. RESULTS
AND
DISCUSSION
The results of thermal analyses of metal perchlorate ammines are presented in TabIe I. Ail the compiexes decompose in two steps as observed by Sherrif and
258 TABLE
1
THERMAL
DECOMPOSITION
DATA
OF
MFTAL
PERCHmUTE
DTA peak remp.
Thermogracimeiry
(“c)
% ua-ghr loss Obsd
Cal.
93 (Endo) 234 (Exe)
19-o -
19.1 I -
co
I22 (Endo) 222 Fo)
15.78 -
18.89 -
Ni
I IO (Endo) 210 Fo)
18.55 -
18.9 -
CU
122 (Endo) 222 (Exe)
-
zn
80 (Endo) 330 @x0)
-
Cd
90 (Endo) 307 (Exe)
16.45 -
MIl
9.30 9.25
AMMINES Reaction
Eqn
en
(~0.d~
2
0)
Eqn (2)
933
Eqn (1) Eqn (2)
9.2s
Eqn (1) Eqn (2)
16.45 -
Eqn (1)
-
Eqn (2)
GaIway’ for nickel perchIorate hexaammine. The formation moniated metal per&orate was not observed in any case.
tMW,),I
to
Eqn (2) Eqn (1) Eqn m
[M(NH,)J
&IO,),
of completely
+ (6 -x) NH,
deam-
(0
x = 2, for M = Mn, Co, Ni and Cd ; x=4,forM=CuandZn,
_mf(NH,)xl(~04)2 -
> 220.C
expIodes
The intermediate decomposition product is the di-ammine in most cases and tetraammine in the case of copper and zinc. The composition of the intermediate ammines was fixed by the observed w-eight-loss in TG (Table 1). These intermediate ammines decompose expfosively to their respective metaI oxides and not to metal chiorides as reported earIier4. On!y cadmium perchlorate di-ammine decomposes to give cadmium chloride. The formation of the metal oxide was indicated by the insolubility of the residue, its color and negative test for CI- ions. No TG estimation of the residue was possibIe because of the explosive reaction. Wendlandt and co-workers have aIso observed the formation of oxide rather than chIoride in the study of thermaI decomposition of the cobalt and copper nitrate amminesg* IO_ The observed infrared absorption frequencies of metal perchiorate hexaammines and the intermediate ammines are presented in Table 2. The assignments of
259 TABLE
2
INFRARED OF METAL
ABSORPTION FREQUENCIES PERCHLORATE AMMINES (cm-‘)
M = Mn, Co, Ni, Cu, Zn and Cd, x = 2 For Mn, Co, Ni and Cd and x = 4 for Cu and Zn.
Amnwnia
bands
Y WHX).-.
v(NH~,_ &(NH3 &,(NH3) ~rOlJH31
VW-N
3400 3300 1620 1240-1270 750 420-450
3300 1620 14OO-I4!0 750 42a-so
Perchloraie bands v3
1100
Vl V*
940 530
1210, r150.1100 (1150.1125. 1095)’ 940 635.630
s Bands observed in the case of M = Cu and Zn_
the characteristic absorption frequencies of the coordinated ammonia are similar to those of Nakamoto * I. The observed absorption bands - 1100 (us), 940 (vr) and 630 (I;) cm- ’ in the case of hexa-ammines indicate the presence of simple perchlorate ion having T, symmetry in these complexes_ The infrared absorption frequencies of the intermediate ammines, however, show a marked difference. The infrared frequencies of these ammines shcw appreciable splitting in the vj and v* region of the perchlorate group. The splitting can be expIained to be due to the presence of monoor bi-dentate perchlorate group coordinating to the metal ion, changing the r, symmetry of the perchIorate group to C,, or CZv similar to those observed in the case of metal perchlorate dihydrates 12*’ 3_ The difference in the infrared spectra of the hexa- and the intermediate ammines could be visualized to be due to the migration of the CIO, groups in the vacancies created by the loss of ammonia molecules. A close inspection of the infrared data of the intermediate ammines appears to indicate the presence of H-bonding in these molecules. As can be seen from Table 2, the N-H stretching frequency of these intermediate am;nines appears as a single broad band -3300 cm- I. Further, the NH3 deformation band which appears - 1250 cm- ’ in the hexa-ammines appears to be shifted to - 1400 cm- ’ in the intermediate ammines. Both these observations may be attributed to the presence of H-bonding’ ’ between the N-H proton and oxygen atom of the C104 group. The H-bonding appears to be responsible for holding the ammonia moIecules in the intermediate ammines. This probabIy expIains why it is not possible to deammoniate completeIy these intermediate ammines to yield pure metal perchlorates, prior to decomposition.
260 REFERENCES 1 K. C Pat& V. R. Pai Ycrnekcr, and S. R. Jain, Combrrsfionand F&me, (1975) in press_ 2 F_ Ephraim, Ba.. 46 (1913) 3103: 48 (1915) 638. 3 F_ Ephraim and C. Zapata. Heio. Chim. Ado, 17 (1934) 296. 4 W. Frienderich and P. Vcrvoost, C_ A., 21 (1927) 1184. 5 W. R Tomlinso~ Id G. Ottoson and L_ F_ Audrieth, J. Am. C&m_ Sue_, 71 (1949) 375. 6 R. A_ F_ Sherrif and A. K. Galway, J. Chem. Sot., (I 967) I705 7 XC_C. Patil and E. A. Sccco, Con. I. Ckrrr., 49 (1971) 3531. 8 S. R_ Jti and P. R. Nambiar, Indian J_ Chcm., 12 (1974) 1087. 9 W. W_ Weudkndt and J. P. Smith, J. Znorg. Xucl. Chem., 25 (1963) 955. 10 T_ M. Southern and W_ W. WendIandt, J. fnorg. IVucZ. Chent.. 32 (1970) 3783?1 K- Nakamoto, Infrared Specrro of I.rgunfc and Coordination Compounds, Wiley and Sons., New York, 1962, p. 163s 12 B. J. Hathaway and A. E Underhill, J. Ckmz. Sac., (1961) 3091. 13 A. Ha& and S_ D. ROSS, Spccrrochiim.Ada, 22 (1966) 1949.
Acra, 15 (Z976) 257-260
cc:; Elscvier Scientific Publishing Company, Amsterdam - Printed in Be.Igium
Note
Metal
perchlorate
IL C PATIL
AND
ammines:
thermal
and infrared
studies
V. R. PAI VERNEKER
Departmennr qf Inorganic and PhysicaI Chemisfry, Bangalore(India)
in&n
Instirure of Science.
S. R. JAIN Departmenf
of Aeronaufics,
Indian Institute of Science, BangaIore-560012
(Irzdia)
(Rezeived C September :975)
While studying the ca*Mytic effect of transition metal perchlorate ammines on the therma1 decomposition of ammonium perchlorate’, the ignition characteristics of pure metal perchlorate ammines gave interesting results. On looking through the literature it was found that, whereas preparation and explosive properties of the metal perchlorate ammines have been described2-6, no detailed account of the nature of intermediates and products of decomposition of these meta perchlorate ammines are reported. In the present study we report, the preparation, infrared spectra and the thermal decomposition characteristics of some of the transition metal perchlorate ammines and their intermediates. EXPERIMENTAL
The metal perchlorate hexahydrates were prepared by the reaction of metal carbonates, oxides or hydroxides with 60% perchloric acid and the perchlorate salts were crystallised from water and washed with chloroform. The metal perchlorate ammines were prepared as reported earIier2*‘, by &king -2 g of the freshIy prepared hexahydrate with -25 ml of anhydrous liquid ammonia. The detaik of the experimental set-up are described elsewhere’. DifZerential thermal analysis (DTA) and thermogravimetry (TG) units employed were similar to those described earlier’. Al1 experiments were done in air_ Heating rates employed were 12 “C n-k-’ for DTA and 5°C min- ’ in the case of TG. PIatinum cups were used as sample holders in DTA experiments. Since the metal perchIorate ammines are highly explosive the amount of the sample used was restricted to t30 mg. Infrared spectra were recorded on a Carl-Zeiss Jena U-R-10 double beam infrared spectrophotometer using KBr pellets as well as Nujol mulls. RESULTS
AND
DISCUSSION
The results of thermal analyses of metal perchlorate ammines are presented in TabIe I. Ail the compiexes decompose in two steps as observed by Sherrif and
258 TABLE
1
THERMAL
DECOMPOSITION
DATA
OF
MFTAL
PERCHmUTE
DTA peak remp.
Thermogracimeiry
(“c)
% ua-ghr loss Obsd
Cal.
93 (Endo) 234 (Exe)
19-o -
19.1 I -
co
I22 (Endo) 222 Fo)
15.78 -
18.89 -
Ni
I IO (Endo) 210 Fo)
18.55 -
18.9 -
CU
122 (Endo) 222 (Exe)
-
zn
80 (Endo) 330 @x0)
-
Cd
90 (Endo) 307 (Exe)
16.45 -
MIl
9.30 9.25
AMMINES Reaction
Eqn
en
(~0.d~
2
0)
Eqn (2)
933
Eqn (1) Eqn (2)
9.2s
Eqn (1) Eqn (2)
16.45 -
Eqn (1)
-
Eqn (2)
GaIway’ for nickel perchIorate hexaammine. The formation moniated metal per&orate was not observed in any case.
tMW,),I
to
Eqn (2) Eqn (1) Eqn m
[M(NH,)J
&IO,),
of completely
+ (6 -x) NH,
deam-
(0
x = 2, for M = Mn, Co, Ni and Cd ; x=4,forM=CuandZn,
_mf(NH,)xl(~04)2 -
> 220.C
expIodes
The intermediate decomposition product is the di-ammine in most cases and tetraammine in the case of copper and zinc. The composition of the intermediate ammines was fixed by the observed w-eight-loss in TG (Table 1). These intermediate ammines decompose expfosively to their respective metaI oxides and not to metal chiorides as reported earIier4. On!y cadmium perchlorate di-ammine decomposes to give cadmium chloride. The formation of the metal oxide was indicated by the insolubility of the residue, its color and negative test for CI- ions. No TG estimation of the residue was possibIe because of the explosive reaction. Wendlandt and co-workers have aIso observed the formation of oxide rather than chIoride in the study of thermaI decomposition of the cobalt and copper nitrate amminesg* IO_ The observed infrared absorption frequencies of metal perchiorate hexaammines and the intermediate ammines are presented in Table 2. The assignments of
259 TABLE
2
INFRARED OF METAL
ABSORPTION FREQUENCIES PERCHLORATE AMMINES (cm-‘)
M = Mn, Co, Ni, Cu, Zn and Cd, x = 2 For Mn, Co, Ni and Cd and x = 4 for Cu and Zn.
Amnwnia
bands
Y WHX).-.
v(NH~,_ &(NH3 &,(NH3) ~rOlJH31
VW-N
3400 3300 1620 1240-1270 750 420-450
3300 1620 14OO-I4!0 750 42a-so
Perchloraie bands v3
1100
Vl V*
940 530
1210, r150.1100 (1150.1125. 1095)’ 940 635.630
s Bands observed in the case of M = Cu and Zn_
the characteristic absorption frequencies of the coordinated ammonia are similar to those of Nakamoto * I. The observed absorption bands - 1100 (us), 940 (vr) and 630 (I;) cm- ’ in the case of hexa-ammines indicate the presence of simple perchlorate ion having T, symmetry in these complexes_ The infrared absorption frequencies of the intermediate ammines, however, show a marked difference. The infrared frequencies of these ammines shcw appreciable splitting in the vj and v* region of the perchlorate group. The splitting can be expIained to be due to the presence of monoor bi-dentate perchlorate group coordinating to the metal ion, changing the r, symmetry of the perchIorate group to C,, or CZv similar to those observed in the case of metal perchlorate dihydrates 12*’ 3_ The difference in the infrared spectra of the hexa- and the intermediate ammines could be visualized to be due to the migration of the CIO, groups in the vacancies created by the loss of ammonia molecules. A close inspection of the infrared data of the intermediate ammines appears to indicate the presence of H-bonding in these molecules. As can be seen from Table 2, the N-H stretching frequency of these intermediate am;nines appears as a single broad band -3300 cm- I. Further, the NH3 deformation band which appears - 1250 cm- ’ in the hexa-ammines appears to be shifted to - 1400 cm- ’ in the intermediate ammines. Both these observations may be attributed to the presence of H-bonding’ ’ between the N-H proton and oxygen atom of the C104 group. The H-bonding appears to be responsible for holding the ammonia moIecules in the intermediate ammines. This probabIy expIains why it is not possible to deammoniate completeIy these intermediate ammines to yield pure metal perchlorates, prior to decomposition.
260 REFERENCES 1 K. C Pat& V. R. Pai Ycrnekcr, and S. R. Jain, Combrrsfionand F&me, (1975) in press_ 2 F_ Ephraim, Ba.. 46 (1913) 3103: 48 (1915) 638. 3 F_ Ephraim and C. Zapata. Heio. Chim. Ado, 17 (1934) 296. 4 W. Frienderich and P. Vcrvoost, C_ A., 21 (1927) 1184. 5 W. R Tomlinso~ Id G. Ottoson and L_ F_ Audrieth, J. Am. C&m_ Sue_, 71 (1949) 375. 6 R. A_ F_ Sherrif and A. K. Galway, J. Chem. Sot., (I 967) I705 7 XC_C. Patil and E. A. Sccco, Con. I. Ckrrr., 49 (1971) 3531. 8 S. R_ Jti and P. R. Nambiar, Indian J_ Chcm., 12 (1974) 1087. 9 W. W_ Weudkndt and J. P. Smith, J. Znorg. Xucl. Chem., 25 (1963) 955. 10 T_ M. Southern and W_ W. WendIandt, J. fnorg. IVucZ. Chent.. 32 (1970) 3783?1 K- Nakamoto, Infrared Specrro of I.rgunfc and Coordination Compounds, Wiley and Sons., New York, 1962, p. 163s 12 B. J. Hathaway and A. E Underhill, J. Ckmz. Sac., (1961) 3091. 13 A. Ha& and S_ D. ROSS, Spccrrochiim.Ada, 22 (1966) 1949.