- Email: [email protected]
Photolysis of nitrosylruthernium chloro complexes
INORG.
NUCL.
CHEM.
LETTERS
Vol. 7, pp.
1191-1194,
1971.
Perpmon Press.
Printed in Great Britain.
PHOTOLYSIS OF NITROSYLRUTHENIURCHLORO COMPLEXES~ by A. Barry Cox** and Richard M. Wallace Savannah River Laboratory E. I. du Pont de Nemours and Co. Aiken, South Carolina 29801 ~ e c e i v e d 13 August 19"/1)
During our i n v e s t i g a t i o n s o f the aqueous c h e m i s t r y of p o t a s s i u m pen~achloronitrosylruthenate(III),
1'2 t h e f o l l o w i n g phenomena were o b s e r v e d :
S o l u t i o n s o f t h i s compound i n c o n c e n t r a t e d h y d r o c h l o r i c a c i d t u r n e d brown when s t o r e d i n t h e p r e s e n c e o f l i g h t . sition
However, s o l u t i o n s o f i d e n t i c a l
compo-
in the absence of light showed no such effect.
For an initial investigation into this effect, solutions I x 10"2M in K2RuNOCIs and 8M in HCI were irradiated with a high intensity mercury arc lamp.
The results were as follows:
Solutions exposed to the atmosphere
during irradiation became dark brown.
Solutions irradiated in closed con-
tainers changed from the characteristic pink of the original solution to a pale yellow-orange.
When the stopper was removed from the cell, these
solutions became much darker until colored similarly to the solutions irradiated in the presence of air.
Solutions that were purged with air,
oxygen, or nitrogen during irradiation were also pale yellow-orange; however, were almost unaffected by exposure to the atmosphere.
* The i n f o r m a t i o n c o n t a i n e d i n t h i s a r t i c l e was developed course o f work u n d e r C o n t r a c t AT(07-2)-1 with t h e U. S. Energy Commission. ** This work was done while the author was an ORAU Faculty Participant. Present address: Department of Chemistry, Jacksonville University, Jacksonville, Alabama. 1191
during the Atomic Research State
these,
1192
PHOTOLYSIS OF NITROSYLRUTHENIUM CHLORO COMPLEXES
Vol. 7, No. 12
The ultraviolet and visible spectra of the irradiated solutions were compared to spectra obtained from known ruthenium compounds dissolved in the same media (aM HCI).
In all cases, some of the original complex was
still present after irradiation.
Solutions purged during irradiation or
protected from the atmosphere had ultraviolet and visible spectra'consistent with a mixture of K2RuNOCIs and K2Ru(III)CIsH20 dissolved in 8M HCl. 3
The
maximum amount of ruthenium(III) obtained was approximately 70%. Samples irradiated in open cells or in closed cells and then exposed to the atmosphere had a visible spectra consistent with monomeric ruthenium(IV) chloro complexes. 4's
The ultraviolet spectra indicated also the presence
of ruthenium(III) chloro complexes (characteristic peak at 347 m~).
A typical
20-hour irradiation sample was estimated from known absorbance coefficients to yield 30% ruthenium(III), 30% ruthenium(IV), and 40% nitrosylruthcnium. However, quantitative comparisons are difficult, because monomeric ruthenium(IV] chloro complexes react at a significant rate to form ruthenium(III) and dimeric ruthenium(IV]. The following reaction scheme is consistent with our observations: I.
RuNOCI
hv
2.
*RuNOCI
3.
NO + ½ 02 ~
4.
Ru(III)CI
x
*RuNOCl ~
x
x
x
Ru(lll)Cl
x
+ NO
NO2
+ NO2 ~
Ru(IV)CI x + NO
The exact number of chlorides per species is in doubt, but the species are probably mixtures of the higher chloro complexes. When samples are open to the atmosphere, all four steps take place. When samples are stoppered, only the first two steps can occur until the cell is opened to the atmosphere,
frith purged samples, it is believed that
Vol. 7, No. 12
PHOTOLYSIS OF NITROSYLRUTHENIUM CItLORO COMPLEXES
1193
the oxides of nitrogen are removed from solution before a reaction with the ruthenium(III) species can occur. During one irradiation, oxygen gas that had been bubbled through the reaction media was trapped in another acidic solution.
The solution gave
a positive test for the presence of nitrous acid, s which was produced by the acid hydrolysis of nitrogen dioxide. To test step four of the reaction scheme, a solution 1 x 10-3M in K2RuCIsH20 and 8M in HCI was prepared. chiometric amount of sodium nitrite.
To this solution was added a stoiThe ultraviolet and visible spectra
of the resulting solution was recorded after the solution was allowed to stand for 10 minutes.
Calculations using known molar absorbance coefficients 2-W
indicated that more than 90% of the ruthenium(III) had been converted to ruthenium(IV).
The results of this experiment were somewhat surprising,
since the reaction of ruthenium(III) chloro complexes and ruthenium(IV) chloro complexes with KNO2 in water followed by acidifying with HCI is a standard method of preparing K2RuNOCIs. Further studies are planned.
Preliminary work indicates that nitrosyl-
ruthenium combined with other ligands is also decomposed by ultraviolet irradiation.
REFERENCES I.
E. E. Mercer, W. M. Campbell, J r . , and R. M. Wallace, Imorg. C/~em. 3, 1018 [1964).
2.
A. B. Cox, "The Rates of Hydrolysis of Chloro Complexes of Nitrosylruthenium and Studies of the Chloro Complexes of Ruthenium IV," Ph.D. Thesis, University of South Carolina, 1967.
3.
D. A. Fine, "Chloride Complexes of Ruthenium(III)'~ Ph.D. Thesis, University of California, 1960.
1194
PHOTOLYSIS OF NITROSYLRUTHENIUM CHLORO COMPLEXES
4.. C. K. Jorgenson, ~l. Phys. 2j 509 (1959). 5.
6.
E. E. Mercer and A. B. Cox, unpubl/shed results.
F. D. Snell and C. T. Snell.
ColoPimetr~e Method~ of Ar~ysis,
3rd ed., Vol. If, p. 803, D. Van Nostrand, New York, 1954.
Vol. 7, No. 12
NUCL.
CHEM.
LETTERS
Vol. 7, pp.
1191-1194,
1971.
Perpmon Press.
Printed in Great Britain.
PHOTOLYSIS OF NITROSYLRUTHENIURCHLORO COMPLEXES~ by A. Barry Cox** and Richard M. Wallace Savannah River Laboratory E. I. du Pont de Nemours and Co. Aiken, South Carolina 29801 ~ e c e i v e d 13 August 19"/1)
During our i n v e s t i g a t i o n s o f the aqueous c h e m i s t r y of p o t a s s i u m pen~achloronitrosylruthenate(III),
1'2 t h e f o l l o w i n g phenomena were o b s e r v e d :
S o l u t i o n s o f t h i s compound i n c o n c e n t r a t e d h y d r o c h l o r i c a c i d t u r n e d brown when s t o r e d i n t h e p r e s e n c e o f l i g h t . sition
However, s o l u t i o n s o f i d e n t i c a l
compo-
in the absence of light showed no such effect.
For an initial investigation into this effect, solutions I x 10"2M in K2RuNOCIs and 8M in HCI were irradiated with a high intensity mercury arc lamp.
The results were as follows:
Solutions exposed to the atmosphere
during irradiation became dark brown.
Solutions irradiated in closed con-
tainers changed from the characteristic pink of the original solution to a pale yellow-orange.
When the stopper was removed from the cell, these
solutions became much darker until colored similarly to the solutions irradiated in the presence of air.
Solutions that were purged with air,
oxygen, or nitrogen during irradiation were also pale yellow-orange; however, were almost unaffected by exposure to the atmosphere.
* The i n f o r m a t i o n c o n t a i n e d i n t h i s a r t i c l e was developed course o f work u n d e r C o n t r a c t AT(07-2)-1 with t h e U. S. Energy Commission. ** This work was done while the author was an ORAU Faculty Participant. Present address: Department of Chemistry, Jacksonville University, Jacksonville, Alabama. 1191
during the Atomic Research State
these,
1192
PHOTOLYSIS OF NITROSYLRUTHENIUM CHLORO COMPLEXES
Vol. 7, No. 12
The ultraviolet and visible spectra of the irradiated solutions were compared to spectra obtained from known ruthenium compounds dissolved in the same media (aM HCI).
In all cases, some of the original complex was
still present after irradiation.
Solutions purged during irradiation or
protected from the atmosphere had ultraviolet and visible spectra'consistent with a mixture of K2RuNOCIs and K2Ru(III)CIsH20 dissolved in 8M HCl. 3
The
maximum amount of ruthenium(III) obtained was approximately 70%. Samples irradiated in open cells or in closed cells and then exposed to the atmosphere had a visible spectra consistent with monomeric ruthenium(IV) chloro complexes. 4's
The ultraviolet spectra indicated also the presence
of ruthenium(III) chloro complexes (characteristic peak at 347 m~).
A typical
20-hour irradiation sample was estimated from known absorbance coefficients to yield 30% ruthenium(III), 30% ruthenium(IV), and 40% nitrosylruthcnium. However, quantitative comparisons are difficult, because monomeric ruthenium(IV] chloro complexes react at a significant rate to form ruthenium(III) and dimeric ruthenium(IV]. The following reaction scheme is consistent with our observations: I.
RuNOCI
hv
2.
*RuNOCI
3.
NO + ½ 02 ~
4.
Ru(III)CI
x
*RuNOCl ~
x
x
x
Ru(lll)Cl
x
+ NO
NO2
+ NO2 ~
Ru(IV)CI x + NO
The exact number of chlorides per species is in doubt, but the species are probably mixtures of the higher chloro complexes. When samples are open to the atmosphere, all four steps take place. When samples are stoppered, only the first two steps can occur until the cell is opened to the atmosphere,
frith purged samples, it is believed that
Vol. 7, No. 12
PHOTOLYSIS OF NITROSYLRUTHENIUM CItLORO COMPLEXES
1193
the oxides of nitrogen are removed from solution before a reaction with the ruthenium(III) species can occur. During one irradiation, oxygen gas that had been bubbled through the reaction media was trapped in another acidic solution.
The solution gave
a positive test for the presence of nitrous acid, s which was produced by the acid hydrolysis of nitrogen dioxide. To test step four of the reaction scheme, a solution 1 x 10-3M in K2RuCIsH20 and 8M in HCI was prepared. chiometric amount of sodium nitrite.
To this solution was added a stoiThe ultraviolet and visible spectra
of the resulting solution was recorded after the solution was allowed to stand for 10 minutes.
Calculations using known molar absorbance coefficients 2-W
indicated that more than 90% of the ruthenium(III) had been converted to ruthenium(IV).
The results of this experiment were somewhat surprising,
since the reaction of ruthenium(III) chloro complexes and ruthenium(IV) chloro complexes with KNO2 in water followed by acidifying with HCI is a standard method of preparing K2RuNOCIs. Further studies are planned.
Preliminary work indicates that nitrosyl-
ruthenium combined with other ligands is also decomposed by ultraviolet irradiation.
REFERENCES I.
E. E. Mercer, W. M. Campbell, J r . , and R. M. Wallace, Imorg. C/~em. 3, 1018 [1964).
2.
A. B. Cox, "The Rates of Hydrolysis of Chloro Complexes of Nitrosylruthenium and Studies of the Chloro Complexes of Ruthenium IV," Ph.D. Thesis, University of South Carolina, 1967.
3.
D. A. Fine, "Chloride Complexes of Ruthenium(III)'~ Ph.D. Thesis, University of California, 1960.
1194
PHOTOLYSIS OF NITROSYLRUTHENIUM CHLORO COMPLEXES
4.. C. K. Jorgenson, ~l. Phys. 2j 509 (1959). 5.
6.
E. E. Mercer and A. B. Cox, unpubl/shed results.
F. D. Snell and C. T. Snell.
ColoPimetr~e Method~ of Ar~ysis,
3rd ed., Vol. If, p. 803, D. Van Nostrand, New York, 1954.
Vol. 7, No. 12