NOTES
176
1’01. 65
NOTES INORGANIC COMPLEX COMPOUNDS CONTAINING POLYDENTATE GROUPS. XIX. REACTION OF COMPLEXES OF MANGANESE(I1) AND TETRAETHYLENEPENTAMINE WITH HYDROXIDE IONS1 BY HANSB. JONASSEN AND V. V. RAMANUJAM~ Richardaon Chemiral Laboratories, Tulane Uniuersitg, New Odeana, Louisiana Receiued December 17, 1969
The complex compounds formed between tetraethylenepenta.mine (abbrev. tetren) and manganese (11) ions have been investigated in these laboratories.a The purpose of this study was to determine the types of complexes formed between tetren and manganese(I1) ions in the presence of hydroxide ions. Experimental A Reagents.-Tetren.SHCl was prepared by the method developed in these laboratories. Carbonate-free solutions of sodium hydroxide were prepared and standardized against potassium acid hthalate. Manganese(11) perchlorate was prepared from manganese sulfate and barium perchlorate. The solution was standardized by estimation of this manganese as pyrophosphate. B Apparatm.-The conductometric,potentiometric and magnetic titrations were made with assemblies described in an earlier paper 4.6
8.p.
responded to about two unpaired electrons per manganese(I1) ion. Discussion The break at one equivalent of hydroxide ions in the conductometric and potentiometric titrations has been interpreted to indicate that the first step in the reaction is the neutralization of the first hydrogen of the cation of the pentahydrochloride. The second break is due to the formation of the hydrogen ~ o m p l e x , ~[MnH3 tetrenj5+. Further addition of hydroxide ions leads to khe formation of a new species on the addition of 4.5 equivalents of alkali. By analogy with systems investigated and already reported6.8 this ion seems to be a hydroxobridged binuclear complex. The reaction taking place between the addition of 2 and 4.5 equivalents of hydroxide would then be 2[MnH8 tetren]6+
+ 50H- +
+
[Mn2(Htetren)aOH]6+ 4&0
The sixth octahedral coordination positions unfilled by the amine nitrogens and the bridging OHgroup would be filled by water giving then the ion [Mnz(Htetren)2(HpO)pOH]~+. The structure postulated for this complex ion is given in Fig. 1.
Results 1. Conductometric and Potentiometric Titra-
tions.-When an equimolar mixture of manganese (11) perchlorate and tetren.5HCl is titrated conductometrically against hydroxide ions in the absence of oxygen6breaks are observed at 1,2 and 4.5 equivalents of hydroxide ions. No breaks are observed a t 5 or 5.5 equivalents, but a brown precipitate begins to appear when about 6 equivalents had been added. Similar results were obtained when the change in pH was followed for the above system under. the same conditions. 2. Magnetic Titration.-A plot of the Awls due to change in inagnetic susceptibility of the system when the same titration was followed with a Gouy magnetic balance showed breaks when 2 and 4.5 equivalents of alkali had been added. There is a decrease in the paramagnetic susceptibility of the system and this reaches a minimum a t 4.5 equivalents of alka,li. The moment calculated for this point by the a,pplication of Wiedemann’s law6 cor(1) Abstracted in part from the Ph.D. Dissertation submitted by V. V. Ramanujam to the Tulane Univeraity. 1958. This research was supported in part by a grant from the National Institutes of Health. (2) University of Madras, Guindy, Madras 25, India. (3) L. Weeterman. Dissertation, Tulane University, 1958. (4) H. B. Jonasiaen, J. A. Bertrand, F. R. Groves, Jr., and R. I. Steara, J . A m . Chem. Soc., 79, 4279 (1957). ( 5 ) H. B. Jonasaen and V. V. Ramanujam, THISJOUBNAL, 6S, 411 (1959). (6) P. W. Selwood, “Magnetochemiatry,” Interacienoe Publishers, Ino., New York, N. Y., 1956. D. 107.
Fig. 1.
The absence of breaks in the titration curves when 5 and 5.5 equivalents of base had been added seems to indicate that the hydrogen of the Htetreii has not been neutralized allowing only four of the aminonitrogens of the ligand to coordinate leaving the fifth nitrogen as an ammonium nitrogen. The change of slope at 4.5 equivalents of the base in the potentiometric and conductometric titrations and the minimum at the same point in the magnetic titration seem to support the postulate of a hydroxo bridged binuclear complex ion. Work on the structure of the corresponding iron (11) complex is under way. The corresponding complexes of iron and manganese in oxidation states higher than two seem to be absent in aqueous solutions since only the hydroxides of the metals were (71 G. Schwarzenbach. Helu. Chim. Acta, SS, 947 (1950). ( 8 ) H. B. Jonassen and G. T. Strickland, T H I JOUBNAL, ~ 80, 312 (1958).
Jan., 1961 formed under tsimilar experimental conditions. The Fe(I1) complex shows unusual catalytic activity which is also under investigation in these laboratories.
RADIOLYSIS OF METHANE IN THE PRESENCE OF OXYGEN. THE FORMATION OF METHYL HYDROPEROXIDE BY G. R. h.JOHNSON’ AND G. A. SALMON Unzted Rangdom dtomic E?ergy Authontu, Isotope Research Diutston, Tschnologzcal Irradaatzon Group. Wantage Research Laboratones, Grove, W anlage, Berks. Recezved May 26, 1960
Lind and Bardwel12showed that an over-all pressure change occurred when methane-oxygen mixtures were irradiated with radon a-rays. The endproducts of the reaction were reported to be carbon dioxide and watler, but no attempt was made to identify any intermediate products nor to establish the reaction mechanism. More recently, Mikhailov, et aL3 studied the irradiation of methane-oxygen mixtures using a beam of electrons produced a t 112 kv. The products identified were: hydrogen, carbon monoxide, carbon dioxide, ethane, ethylene, propane, butane and water. The presence of peroxides, aldehydes, acids and alcohols was shown by group reactions, but these products were not characterized. Relatively large total radiation doses (>1019 e.?. ml.-I) were used and, under these conditions, it is unlikely that the observed products would all be primary products of the radiolysis. In the present work, the peroxide formed when methane-oxygen mixtures are irradiated with relatively low radiation doses (
