On the hydrolysis of manganous chloride

150

Notes

relation to the ratio So/S. of its solubility both for solvent and an aqueous solution, the relative solubility in the solvent can be directly related to the relative values of the distribution coefficients for the mixed solvent and a given aqueous solution. As the solubility of the copper acetylacetonate is small in an aqueous solution[7], its molarity is converted to the mole fraction. The relation between observed value of log Pc°~^2 and of log So/$2 is shown in Fig. 2, where the points fall on the straight line with a

The solubility and the distribution coefficient of copper acetylacetonate in n-heptane--benzene mixed solvent are determined, and these results are explained very quantitatively based on the regular solution theory.

Acknowledgements--The author is very grateful to Dr. Totaro Goto and Mr. Teiji Okubo, of National Chemical Laboratory for Industry of Tokyo, for invaluable discussions and helpful suggestions.

2.0!

~

Tokyo Metropolitan Industrial Technical Institute 3-chome Nishigaoka Kita-ku, Tokyo Japan

1.5

HIDEO KOSHIMURA

~ C K S 0.5

0.0

o.'0

015

1.o

115

log SO~Sw (obs.) Fig. 2. Correlation between the distribution coefficient of copper acetylacetonate and the ratio of its solubility both for organic solvent and an aqueous solution. slope of ca. 1. Consequently, the equation of the straight line is following; log P°uA 2 =

log So/S~ + A

(6)

where A is constant and the value of A is almost zero.

1. N. Suzuki and K. Aldba, L Inorg. Nucl. Chem.33, 1897 (1971); and references therein. 2. K. Aldba, Z Inorg. Nucl. Chem. 35, 2525 (1973); ibid. 35, 3323 (1973). 3. H. A. Mottola and H. Freiser, Talanta 13, 55 (1966); ibid. 14, 864 (1967). 4. M. Taube,/. Inorg. Nucl. Chem. 12, 174 (1959); ibid. 15, 171 (1960). 5. M. Tanbe, Dokland No. 270/V. Warshawa (1961). 6. S. Old, T. Omori, T. Wakahayashi and N. Suzuki, J. Inorg. Nacl. Chem. 27, 1141 (1965). 7. H. Koshimura, L Inorg. Nacl. Chem. 38, 1705 (1976). 8. M. M. Jones, J. Am. Chem. Soc. 81, 3188 (1958). 9. H. Koshimura and T. Okubo, Anal. Chim. Acta 67, 331 (1973). 10. J. H. Hildebrand and R. L. Scott, The Solubility of Nonelectrolytes, 3rd Edn. Dover, New York (1964). I 1. T. Omori, T. Wakahayashi, S. Old and N. Suzuki, J. Inorg. Nucl. Chem. 26, 2265 (1964).

J. inorg, nucl. Chem., 1977, VoL 39, pp. 150-151. Pergamon Press. Printed in Great Britain

On the hydrolysis of manganous chloride? (Received 15 April 1976) There are conflicting reports in the literature on the hydrolysis of manganous chloride by steam at temperatures up to 600°C. Different sources indicate that the product is Mn203 [1], a mature of Mn203 and Mn30412] and MnO[3]. Zvorykina[2] determined hydrolysis rates with steam at 1 atm in the temperature range 400-600°C by measuring the rate of evolution of HC1 and claims to have identified the products as/3-Mn~O3 and/3-Mn3Oa by means of chemical and differential thermal analysis. The reactions were thus interpreted as 3 1 1 MnCI2 + ~ H20 ~ ~ Mn203 + 2HCI + ~ H2

(1)

although no attempts to identify or measure the hydrogen were reported. The above results seem to have prompted Baratali and Abedini[4]$ recently to study the hydrolysis of MnF2. The product obtained was MnO. However, Pechkovsii eta/. in 196413] performed DTA and TGA on the dehydration of MnC12.4H20 and on the subsequent reaction of MnCI2 with, probably, 0.5 atm of steam. In the latter studies, they noticed that HCI appeared at 400"C. The product of the reaction was identified by X-ray diffraction analysis as MnO and the reaction occurring, was assumed to be: MnC12+ H 2 0 ~ MnO + 2HC1.

and 4

1

1

MnCI= + ~H20 ~gMn30, + 2HC1 + ~H=

(2)

?Work sponsored by the U.S. Energy Research and Development Administration under contract with the Union Carbide Corporation. *In quoting Zvorykina[2] a typographical error was introduced indicating the formation of B-Mn204 where it should have been /3 -Mn304.

(3)

In our search for reactions conducive to thermochemical cycles for the production of hydrogen from water [5-6] it became evident from thermoehemical calculations that reaction (3) has the more favorable free-energy change among the possible hydrolysis reactions of MnCI2. The free-energy changes calculated for reactions (1), (2) and (3), using formation free energies from various sources[7--9] are, at 900K: AG~I) = 98.2 kJ, AGac2>= 70.7 IO and AGRo>= 41.5 kJ. In order to confirm that reaction (3) exhibits the more favorable

Notes

Chemistry Division Oak Ridge National Laboratory P.O. Box X, Oak Ridge, TN 37830 U.S.A.

free-energy change among the possible MnCln hydrolysis reactions, it was tested experimentally. Manganous chloride tetrahydrate (RG) contained in a platinum boat was located in a silica tube and heated under a flowing mixture of argon ( - 100 ml/min) and steam at nearly I atm. The temperature was raised continuously up to 600~C. The exiting gases passed through a train consisting of a water-cooled condenser, two caustic scrubbers, a Drierite column and finally, through a thermal conductivity bridge calibrated for hydrogen in argon. Only a small amount of hydrogen was detected, probably from the corrosion of some metallic components of the apparatus by HC1, which was negligible with respect to the amount expected if reaction (1) or (2) had occurred. The HC1 content of the condensate was determined by titration; the amount of HCI found agreed well with that expected; i.e. 2 moles per mole of MnCI2. The green solid product obtained was unambiguously identified as MnO by X-ray powder diffraction analysis. The results obtained confirm that reaction (3) has the lowest free-energy change among reactions (1) to (3) and, furthermore, are consistent with those obtained by Pechkovskii et al. [3] and in the hydrolysis of MnF~[4]. We can offer no explanation for the results obtained by Zvorykina, but speculate that the steam used may have been contaminated with a significant amount of oxygen (air).

151

C. E. BAMBERGER D. M. RICHARDSON

REFERENCES 1. H. Remy, (translated by J. S. Anderson) Treatise on Inorganic Chemistry, Vol. II, p. 218. Elsevier, New York (1965). 2. G. I. Zvorykina, Jr. Appl. Chem. U.S.S.R. (trans, Consultants Bureau) 30, 1582 (1957). 3. V. V. Pechkovskii, S. A. Amirova, N. L. Vorob'ev and T. V. Ostrovskaya, Russ. J. Inorg. Chem. 9(9), lll3 (1964). 4. T. Baratali and M. Abedini, J. Inorg. Nucl. Chem. 38, 604 (1976). 5. C. E. Bamberger and J. Braunstein, American Scientist 63(4), 438 (1975). 6. C. E. Bamberger and D. M. Richardson. Science, 189, 715 (1975). 7. A. D. Mah, U.S. Dept. of the Interior, Bureau of Mines Rept. of Investigations 5600 (1960). 8. Janaf Thermochemieal Tables 2nd Edn, US. Dept. of Commerce Pubn. NSRDS-NBS 37 (1971). 9. J. F. Elliot and M. Gleiser, Thermoehemistry for Steelmaking, Vol. I, Addison-Wesley, New York (1960).

J inorg, nucl. Chem., 1977. Vol. 39, pp. 151-153. Pergamon Press. Printed in Great Britain

Stereochemicai features of some oxovanadium(IV) complexes of Schitt bases derived from salicylaldehyde derivatives, o-hydroxyphenones and 2,2'.aminoethyl pyridine (First received 23 June 1975; in revised form 9 February 1976) Through the hole formalism, the oxovanadium(IV) ion with a d ~ configuration is known to be somewhat similar to copper(II) ion with a d 9 configuration. Copper(lI) complexes with antiferromagnetic exchange are well known and are a source of continuing interest and controversy [1,2]. On the contrary, only a few examples are known with oxovanadium(IV) complexes [3-9]. In previous papers from this laboratory the transition metal complexes of 2,2'-aminoethyl pyridine [10-12] and its Schitt base complexes[13] derived from salicylaldehyde and o-hydroxyphenones were described and their stereochemistry was discussed. The effect of distortion from the regular octahedral structure, produced by ligands of unequal donor strengths, on the electronic spectra of Ni(II) and Co(II) complexes was also shown[ll]. As an extension of these studies, the oxovanadium(IV) complexes of Schiff bases derived from 2,2'-aminoethyl pyridine have been synthesized and their stereochemistry is acertained by analytical magnetic, electronic and IR spectral studies. Since the tegragonal distortion seems to be the dominant feature in the present studies, the radial parameters Ds and Dt have been evaluated. X

Y I

OH

N ~

when Y = H, X = H, 5C1, 5NO2, 5,6 Benzo when X = H, Y = CHs = C2H~ = C3H7

Notation x-Salaep Hapaep Hppaep Hbpaep

EXPERIMENTAL Preparation of the complexes To a solution of oxovanadium(IV) chloride (0.02mole) in ethanol were added salicylaldehyde and its derivatives or o-

hydroxyphenones (0.02mole) and an ethanolic solution of 2,2'-aminoethyl pyridine (0.02 mole). The reaction mixture was stirred on a magnetic stirrer for about 15 rain to one hour. A solution of sodium acetate (0.02 mole) was added and the reaction mixture was stirred again for about 3-10 hr at 60°C and allowed to stand overnight. The precipitate was collected by filtration and washed with hot water, ethanol and ether, dried and analysed. The complexes were obtained as greenish blue or olive green microcrystals. Chlorine was estimated gravimetrically as silver chloride. Vanadium metal in all the complexes was estimated using EDTA and eriochrome black T as indicator and confirmed by igniting the complexes in air and then estimating the metal as pentaoxide. The analytical data are reported in Table 1. The magnetic moment, IR and electronic spectral measurements were made as reported previously[Ill. The electronic spectral bands and the ligand field parameters are given in Table 2. RESULTS AND DISCUSSION Analytical results show a 1: 1 metal to ligand stoichiometry in all cases. All the complexes decompose above 300°C without melting. They are insoluble in water and non-polar organic solvents but are very slightly soluble in polar organic solvents like ethanol, nitrobenzene, nitromethane, pyridine and diethyl sulfoxide. These solutions show very small conductances, indicating that the complexes are not dissociated in the above solvents. The magnetic moment of oxovanadium(IV) complexes, when the orbital angular contribution is almost completely quenched, as it is expected by the low symmetry field, is around 1.73 B.M.[1417]. The moment value for the present complexes has been found to be in the range 1.32-1.58 B.M. at room temperature which is abnormally lower than the spin only value (-1.73 B.M.) for a d 1 configuration. This subnormal value may be due to the presence of exchange coupled antiferromagnetism in these complexes. Zelentsov[3,4] suggested for the magnetic abnormality of oxovanadium(IV) complexes of 5, substituted N-(2hydroxyphenyl)salicylidenimine a dimeric oxygen bridged structure, which provides an appropriate symmetry for the 3d~y orbitals of vanadium(IV) to overlap with each other and form a