was calculated to be 23 cm/minute. With shorter columns of larger diameter containing the same amount of resin, the linear flow rate could be decreased and probably the breakthrough capacity improved without adversely affecting other parameters of the combined ion exchange-colorimetric method. Accuracy and Precision. Under the conditions in Table I, no significant bias was observed in the analysis of acid solutions containing hydrolyzable ions as long as the break-
through capacity of the column was not exceeded. The relative standard deviation for the analysis of a 0.2M hydrolyzable acid solution containing 0.2M La3+was 1.1% (Table 11). RECEIVED September 28,1967. Accepted November 20,1967. Information contained in this article was developed during the course of work under Contract AT(07-2)-1 with the U. S. Atomic Energy Commission.
Complexes of Organometallic Compounds. Determination of Phenylthallium Dichloride with Xylenol Oralnge and EDTA Baldassarre Lassandro Pepe, Eleonora Rivarola and Renato Barbieri Istituto di Chimica Generale ed Inorganica, Universitb di Palermo, Italia
W EHAVE RECENTLY prepared and studied several organothallium (111)-halide and -pseudohalide complexes (I). As a subsequent part of our research program, we are now dealing with the determination of stability constants for the above complexes in aqueous solution, which involves a previous measurement of the hydrolysis constants for the investigated organothallium(II1) cations. The latter operation needs a method for the standardization of stock solutions of the cations, and there is no information in the literature on a rapid and nondestructive quantitative analysis of C6HsTl(III) derivatives. This paper describes two methods for the determination of C6HsTIC12in aqueous solutions; they consist of spectrophotometry with xylenol orange and titrimetry with the disodium salt of ethylenediaminetetraacetic acid (EDTA), respectively. The latter method seems to be the first example of a complexometric titration of an organometallic cation with EDTA. EXPERIMENTAL Apparatus. Beckman Instruments Model DK-2A and DU
spectrophotometers, equipped with 10-rnm cells, were used. Reagents. c.~HbTlCl?was prepared and purified as reported elsewhere (2). The others were analytical grade reagents (C. Erba, Milano). Redistilled water was used throughout. Spectrophotometric Determination with Xylenol Orange.
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Xylenol orange, under similar experimental conditions, shows a band with a maximum at 432 mp (E 1.7 X 104) and does not absorb a 576 mp [see also Ref. (31. It follows that a calibration curve may be determined at 576 mp and at the experimental conditions above reported, by using a constant concentration of xylenol orange (e.g., 4 X lO-5M). An aqueous C6HsTIC12sample of unknown concentration could then be quantitatively analyzed for [C&T1C12] ranging to about 3 X (molarities referred from about 6 X to the final solution). Titrimetric Determination with EDTA. Ten to 20 milliliters of a methanol solution of C6HsTlC12 (10-L10-3M) were added to 20 ml of the aqueous buffer solution 0.1M CH3COOH 0.1M CH3COONa (pH = 4.75), and the volume was adjusted to about 100 ml with water. Five to six drops of aqueous 0.1 xylenol orange were then added, and C6H5Tl(III)was titrated with standard aqueous EDTA (10-2 or lO-3M). The end point is revealed by a sudden color change from red to lemon yellow. The stoichiometry corresponds to the formation of a 1 :1 C6HsTl(III)-EDTA complex. This method meets the requirements of precision and accuracy, A series of seven determinations of 10-2M CF,H~T~C~~ with 10-2M EDTA gave =t0.03% as relative standard deviation and 0.9 % as relative error.
+
DISCUSSION
By spectrophotometrically titrating an aqueous-methanolic solution of C6H5T1C12(containing 1W2M CH3COOH f 10-2M CH3COONa)with xylenol orange in the same aqueous buffer, the formation of a 1 :1 complex is observed. This complex shows a strong absorption band in the visible with a maximum at 576 mp, which follows Beer’s law fairly well. In fact its mean molar absorptivity at 576 rnp is E = 3.69 X lo4, i 3 X l o 2as standard deviation, at 25” C in the presence of 1-2% methanol, referred to water as blank. The calculations have been carried out with 15 test results, in the complex concentration range 6 X lop6to 3 X 10-5M, the absorbance ranging from about 0.2 to about 1.0.
The two simple and rapid methods suggested here for the quantitative determination of c&,TlCl~ present several advantages over the destructive methods usually employed (4, which are much more complicated and time-wasting, and cannot be used to standardize C6HsT1(III) salts in aqueous solution. Moreover, the EDTA titration of C6HsTlXz is not influenced by the nature of the anion (X = Cl, NO,, Clod), the presence of a strong electrolyte at high concentration (e.g., 3M NaC104), and (C6H&T1(III) derivatives. The latter compounds, in fact, do not form complexes with either xylenol orange and EDTA. The above method allows the use of
(1) G. Faraglia, L. Roncucci Fiorani, B. Lassandro Pepe, and R. Barbieri,J. Orgunomefal.Chem., 10, 363 (1967), and references
(3) B. Budesinsky, 2.Anal. Chem., 207,247 (1965). (4) A. N. Nesmeyanov and K. A. Kocheshkov, “Methods of Elemento-organic Chemistry,” Vol. 1, North Holland, Amsterdam, 1967.
quoted therein. (2) F. Challenger and B. Parker, J. Chem. SOC.,1931, 1462.
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ANALYTICAL CHEMISTRY
EDTA to check the purity of solid C6H5TI(III) salts, and to standardize their aqueous stock solutions even at a high ionic strength. It is noteworthy that the absorption spectrum of the aqueous 4.7) corresponds to the system Tl(1)-xylenol orange (at pH ligand spectrum, so that no complex formation seems to take place. It follows that only C6HsT1(III)and Tl(III), between the thallium acceptors investigated during this work, form a complex with xylenol orange. This may be explained by ( 5 ) and taking into account the acid character of CBH~TI(III) of Tl(II1) in aqueous solution (6). The reported complex formation between CsHsTI(II1) and both the ligands investigated enlarges the knowledge of the coordination chemistry of organometallic cations. Very little is known about C6H5TI(III),and C6H5T1-(oxinate)lis the only chelate complex hitherto studied (1, 4, 7,8); on the other
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(5) G . Faraglia, L. Roncucci Fiorani, B. L. Pepe, and R. Barbieri, Itiorg. Nucl. Chem. Letters, 2,277 (1966). (6) L. G. Sillen and A. E. Martell, “Stability Constants of Metal Ion Complexes,’’ Special Publ. No. 17, Chem. SOC.,London, 1964.
hand, the only information concerning organometal-EDTA complexes consists of the preparation of some Rz Sn(1V) and R2Pb(IV) derivatives (9, IO). We recently succeeded in the preparation of the solid C6HsTl-EDTA, simply by crystallization from an aqueous solution containing 1 :1 C6H5TIC12and EDTA (2 moles of NaCl per mole of complex remained in the solution phase). We intend to continue our work also on organometal-EDTA complexes, with the aim of investigating the metal atom coordination number and the structure of the complexes. RECEIVED for review September 5 , 1967. Accepted October 26, 1967. Investigation supported by NATO Research Grant No. 301. (7) G. Faraglia, L. Roncucci, and R. Barbieri, Ric. Sci., 35(IIA), 205 (1965). (8) D. Seyferth and R. Bruce King, “Annual Surveys of Organometallic Chemistry,” Vol. 1-2, Elsevier, Amsterdam, 1965-66. (9) H. G . Langer, U. S. Patent 3,117,147, Jan. 7, 1964; Chem. Absrr., 60, 8061d(1964). (10) H. G. Langer, U. S. Patent 3,120,550, Feb. 4, 1964; Chem. Abstr., 60, 120516 (1964).
Spectrophotometric Determination of PaIladium with 2,2’- Dipyridyl ketoxime William J. Holland and John Bozic Depariinent of Chemistry, University of Windsor, Windsor, Ontario, Canada
IN A previous communication ( I ) , the use of pyridine ketoximes in the determination of palladium, gold, rhenium, and iron was summarized. The purpose of the present work was to show that a symmetrical pyridine ketoxime in which no possibility of syn and anti forms exists could be used in the determination of palladium. The fact that such isomers cannot exist for this ligand makes possible a reasonable structural assignment for the resulting complex. The platinum group metals do not interfere and microgram quantities of gold can be tolerated. Interferences due to iron, cobalt, nickel, and copper can be eliminated by the use of ethylenediamine tetraacetic acid disodium salt. Palladium reacts with the reagent to form a water insoluble chelate which is extractable into chloroform. The result of palladium analysis of the chelate showed that the palladium and the reagent combined in the ratio of 1 mole to 2 moles. The palladium chelate in chloroform exhibits an absorption maximum at 410 mp and has a molar absorptivity of 1.2 X 104. EXPERIMENTAL
Instruments. Spectral studies were made with a Hitachi Perkin Elmer Spectrophotometer, a Beckman DB Spectrophotometer, and a Beckman DK-1A Recording Spectrophotometer using 1-cm matched silica cells. Infrared spectra were obtained with the Beckman IR-10 Spectrophotometer. Measurements of pH were made with a Corning Model 12 pH meter. (1) W. J. Holland and J. Bozic, ANAL.CHEM., 39, 109 (1967).
Preparation of Reagent. The procedure of Henze and Knowles (2) may be employed to synthesize 2,2’-dipyridylketone. The starting ketone is also commercially available from The Aldrich Chemical Co., Milwaukee, Wis. The ketone was converted to the oxime with hydroxylamine hydrochloride and after several recrystallizations from water melted at 141-142.5’ C. Anal. calculated for CllH90N3: C, 66.32%; H, 4.55%. Found: C, 66.20%; H, 4.62z. Carbon and hydrogen analyses were done by the Spang Microanalytical Laboratory, Ann Arbor, Mich. Reagent Solution. A 1 % solution of the reagent in 95 ethanol was used. The solution was stable for several months. Standard Solutions. The standard palladium solution was prepared by dissolving anhydrous palladium(I1) chloride in concentrated hydrochloric acid, diluting to 1 liter with distilled water and standardizing by the dimethylglyoxime method according to Vogel (3). Solutions of diverse cations were prepared from their chlorides or nitrates and solutions of diverse anions from their sodium or potassium salts. Procedure. An aliquot of solution containing approximately 20 to 200 pg of palladium(I1) was transferred to a 60-ml separatory funnel. The contents were made slightly acidic by addition of a few drops of dilute hydrochloric acid or potassium hydroxide. To this solution was added 4 ml of a 0.2N sodium acetate-0.2N acetic acid buffer of pH 4.5 and the volume made up to approximately 15-20 ml with distilled water. Two milliliters of reagent solution was added and the contents were shaken briefly. The yellow (2) H. R. Henze and M. B. Knowles, J . Org. Chem., 19, 1127 (1954). (3) A. I. Vogel, “A Textbook of Quantitative Analysis,” 3rd Ed., Longmans Canada Ltd., Toronto, Canada, 1961, p. 512. VOL 40, NO. 2, FEBRUARY 1968
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