Pentamethylene sulfoxide complexes of rare earth perchlorates

930

Notes

preliminary results indicate that [Os(tdth] is oxidized by I2 to [Os(tdt)3]I. However, this compound has not been isolated in a pure state. The osmium-dithiolene complexes reported here and elsewhere[4] are among the heaviest tris complexes of this type of ligand yet synthesized. Unfortunately, it has not been possible to obtain crystals satisfactory for an X-ray study and conclusions about structure, both molecular and electronic, are unwarrented at this time.

West Virginia University Morgantown, WV 26506, U.S.A.

B. JACK McCORMICK," D. S. RINEHART

REFERENCES I. B. J. McCormick, In Methodium Chemicum Houben Weyl (Edited by F. Korte), Vol. 8, Chap. 22. Verlag, Stuttgart (1973); W. P. Grittith, The Chemistry of the Rarer Platinum Metals, Chap. 3. Interscience, New York (1967). 2. G. A. Heath and R. L. Martin, Aust. J. Chem. 23, 1721 (1970). 3. E. Uhlemann and P. Thomas, Z. Naturforsch. 23B, 275 (1968). 4. K. W. Given, S. H. Wheeler, B. S. Jick, L. J. Mahew and U H. Pignolet, lnorg. Chem. lg, 1261 (1979). 5. R. Desimone, J. Am. Chem. Soc. 95, 6239 (1973).

?Author for correspondence.

6. G. N. Schrauzer, V. Mayweg, H. W. Finck, U. MullerWesterhoff and W. Heinrich, Angew. Chem. Int. Ed. 3, 381 (1964); G. N. Schrauzer, H. W. Finck and V. Mayweg, ibid. 3, 639 (1964). 7. F. P. Dwyer and J. W. Hogarth, lnorg. Syn. 5, 204 (1957). 8. W. J. Geary, Coord. Chem. Rev. 7, 87 (1971). 9. At the time that the magnetic measurements were made, constant gradient (Heyding) pole caps were not available locally and conical pole caps were used, The system seemed to give reliable magnetic susceptibility values for materials having magnetic moments of about 2B.M. or higher. However, we feel that the inherent difficulties associated with the measurement of low paramagnetic susceptibilities along with the use of conical pole caps may have made the value of the low paramagnetic moment reported here somewhat inaccurate. 10. The excellent analyses for carbon and hydrogen were somewhat of a surprise since the formation of volatile OsO4 in the combustion process usually interferes with C-H determinations [5, 11]. 11. D. A. Buckingham, F. P. Dwyer, H. A. Goodwin and A. M. Sargenson, Aust. J. Chem. 17, 320 (1964). 12. The chromatogram sheets were spotted with methylene chloride solutions of the complex. 13. A 10-3 M solution at 25°C. 14. J. A. McCleverty, Prog. lnorg. Chem. 10, 49 (1968). 15. E. I. Stiefel, R. Eisenberg, R. C. Rosenberg and H. B. Gray, J. Am. Chem. Soc. 88, 2596 (1966). 16. C. G. Pierpont and R. Bowen, Private communication.

J. inorg,nucl.Chem.Vol.42.pp. 930-932 PergamonPressLtd., 1980. Printedin GreatBritain

Pentamethylene suifoxide complexes of rare earth perchlorates (Received 12 June 1979; received for publication 7 September 1979) In an attempt to prepare the complex La(CIO4)3.9 pmso, where pmso=pentamethylene sulfoxide, described by Edwards et al.[1], we obtained La(C104)3"7 pmso. The corresponding compounds with other lanthanide ions were also prepared and the present paper deals with their isolation and characterization.

EXPERIMENTAL The ligand pmso was prepared by oxidation of the corresponding sulfide (obtained from K and K Laboratories, Inc.) with hydrogen peroxide in acetone solution, ca. 10mmole of pmso was dissolved in methanol-triethyl orthoformate (3:1, v/v) and added to a methanolic solution of I rumple of the hydrated lanthanide perchlorate. Anhydrous diethyl ether was added and the contents were cooled. The fine crystalline product was isolated by filtration, washed with diethyl ether and dried over P4Oio under reduced pressure. In some instances, recrystailization from methanol and diethyl ether was necessary in order to obtain compounds of definite composition. C and H microanalyses were carried out by the Anorg. Chem. Laboratorium, Tech. Universitat, Munchen and by the Microanalytical Laboratory at this Institute. The metal and anion contents determination and the physical measurements were performed as described previously[2]. The compounds were handled in a dry box.

RESULTSAND DISCUSSION The analytical results (Table 1) conform to the formulation of the compounds as Ln(CIO4)3"7pmso, where Ln -- La-Lu and Y. The complexes are slightly hygroscopic, insoluble in non-polar solvents and soluble in polar solvents.

The compound pmso exhibits a rich vibrational spectrum and the assignments in the 4000-100cm -~ region were recently tabulated [3], on the assumption of a Cs chair form. The IR spectra of the complexes Ln(CIO4h'7 pmso in the 4000600cm -~ region are similar in their major aspects and indicate the absence of water or alcohol molecules and the ionic nature of the perchlorate groups (Td symmetry). In the 1050-900cm -~ region, there are three medium to very strong bands at 1015, 980 and 955 cm -~. Only the one at 955 cm -~ has correspondence with a band (at 954cm -t, attributed to PCH2) in the spectrum of the pmso. Probably all these bands have some contribution from us--o, which is coupled with other vibrational modes of the molecule. The S=O stretching vibration of pmso has been assigned at 1032 cm -~, being coupled by Fermi resonance with a band at 993 cm -1, and the C-S stretching vibrations of a' and a" species were assigned at 619 and 604cm -I, respectively[3]. The spectra of the complexes show bands at -640 (very weak) and at 700 cm -~ (medium intensity), which could be assigned to these modes. The foregoing observations indicate that pmso is coordinated as an oxygen-donor ligand and all the sulfoxide molecules are present in the coordination sphere of the metal ion. In the 600-180cm -j region, only two bands show a general tendency to increase from La to Lu, occurring at a higher frequency in the Y compound. These bands are in the ranges 295-300cm -~ and 210-224 cm -~ (306 and 230cm -~, respectively, for Y compound). They have medium intensity and can be assigned to metal-sensitive vibrations (metal-ligand vibration and/or ligand vibrations strongly coupled with metal-ligand vibrations. The IR spectrum of pmso shows intense bands at 283 and 202 cm-I).

931

Notes Table 1. Analytical data(aL melting ranges and molar conductance data tb~ for the compounds of general formula Ln(pmso)7(Cl04)3 Analysis (%) Ln La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y

(a)

Ln

CIO4

10.8 (I0.98) ll.O (II.07) I0.9 (II.12) II.4 (11.36) II.8 (11.78) 11.7 (11.89) 12.1 (12126) 12.2 (12.37) 12.4 (12.61) 12.6 (12.78) 12.9 (12.94) 12.9 (13.05) 13.2 (13.32) 13.3 (13.45) 7.2 (7.32)

23.7 (23.59 23.6 (23.57 23.6 (23.55 23.6 (23.49 23.6 (23.38 23.5 (23.35 23,2 (23.25 23.1 (23.22) 23.3 (23.]6) 23.1 (23.12) 23.2 (23.07) 23.2 (23.04) 23.1 (22.97) 23.1 (22.94) 24.7 (24.56)

Theoretical

Melting

Am(cm2Q-Imole-l)

C

H

Range (°C)

F;eNO2

MeCN

33.2 (33.24) 32.9 (33.21) 32.6 (33.19) 32.3 (33.10) 32.1 (32.94) 32.2 (32.90) 32.1 (32.77) 32.1 (32.72) 32.5 (32.63) 32.3 (32.57) 32.4 (32.51) 32.2 (32.47) 32.2 (32.37) 32.4 (32.32) 34.3

5.6 (5.58) 5.6 (5.57) 5.7 (5.57) 5.6 (5.56) 5.5 (5.53) 5.6 (5.52) 5.5 (5.50) 5.5 (5.49) 5.6 (5.48) 5.5 (5.47) 5.5 (5.46) 5.4 (5.45) 5.4 (5.43) 5.3 (5.42) 5.8

157-176

185

345

164-176

186

348

158-174

191

373

154-178

193

380

168-184

200

381

170-195

205

380

185-197

207

379

187-207

219

373

197-221

221

372

202-218

223

372

202-218

231

362

203-224

238

372

209-232

234

352

226-239

252

390

199-217

227

402

(34.61)

data w i t h i n

(5.81)

parenthesis;

The molar electrolytic conductance data (Table 1) of l mM solutions of the complexes indicate a behavior of l : 3 electrolytes in acetonitrile [4], as it would be expected from IR spectral data. In nitromethane however there is a gradual change from values close to those of 1:2 electrolytes to values typical of h3 electrolyte type, as one goes from La to Lu, indicating a greater tendency to ion-pairing in the beginning of the series. Molar conductances of the Sm compound at various concentrations were measured (Table 2). Onsager's law is not obeyed, evidencing the weak electrolyte behavior of the compound in both solvents. The electronic spectra for Nd and Er complexes in the solid state and in acetonitrile solution were recorded in the hypersensitive transition regions. The observed differences in the curves are suggestive of the presence of species in solution different from those existing in the solid. The occurrence of partial solvolysis is also evidenced by the spectral changes observed when an excess of ligand is added to the solution. X-Ray powder patterns indicate that in spite of showing the

(b)

1.0 mM s o l u t i o n s

at 25.0°C.

same stoichiometry the complexes are not all isomorphous. Three series of isomorphous compounds can be clearly established: the complexes of La and Ce, the complexes of Tb, Dy, Ho, Er and Y, and the complexes of Tm, Yb and Lu. These conclusions are in accordance with the IR spectra which show slight differences in the positions and intensities of some bands in the 700-200cm ~ region. No definite trend concerning isomorphism was shown by the other complexes. Our attempts to reproduce the compound La(CIO4b'9 pmso prepared by Edwards et a/.[l] were unsuccessful, even employing a large excess of pmso. However we prepared the compound Nd(CIO4b'8 pmso (observed analytical data = 10.5% Nd, 34.0% C and 6.0% H; Calc values = 10.39% Nd, 34.61% C and 5.81% H; melting range = 165-183°C) and some non-stoichiometric compounds of Pr and Er, with pmso/Ln ratios between 7/1 and 8/1. Recrystallization of these solids leads to a molar ratio 7/1. There are many other examples of such discrepancies in the literature[5,6]. Even in the case of the smaller ring analog of pmso, i.e. tetramethylene sulfoxide, two series of complexes with

Table 2. Molar conductance data for Sm(pmso)7(CIO4h at (25.0 ~ 0.2)°C MeNO2 Conc.

(mM)

t,!eCN

Am(cmZa'Imole'l)

Conc. (mM)

Am(cm2~'Imole - I )

10,15

154

10.05

245

6.12

165

5.97

267

4.22

166

4.14

291

2.13

189

1.90

335

1.08

208

1.08

377

0.55

223

0.48

430

932

Notes

lanthanide perchlorates have been reported: one with a ligand/metal ratio decreasing from 8ll to 7/117] and another in which this ratio remains constant and equal to 8/1 [8]. Several factors (e.g. the nature of the rare earth--ligand bonding, predominantly ionic and non-directional, the relatively great radius of the metal ion, the existence of conformational equilibrium in the ligand itself) influence the establishement of a compromise in obtaining the maximum shielding for the metal ion and the minimum ligand-ligand repulsion. There may be several possibilities of arrangement for the metal, anions and neutral ligands, with small energy differences between them. Depending on the conditions of precipitation, a particular species separates out. A mixture of species can also be obtained and this is a reasonable explanation for the non-stoichiometric compounds mentioned above.

Acknowledgements--The authors are grateful to A. A. de Andrade for valuable help during the early stages of this research and to the Funda~to de Amparo h Pesquisa do Estado de S,~o Paulo, for a fellowship to A. de O. Thanks are also due to Dr. M. Kawashita Kuya for her comments. V. K. LAKATOS OSORIO A. de OLIVEIRA E. GIESBRECHT

Departamento de Quimica Fundamental lnstituto de Qufmica da Universidade de S~o Paulo C.P. 20780, S(w Paulo 05508 Brasil

REFERENCES 1. J. O. Edwards, R. J. Goetsch and J. A. Stritar, lnorg. Chim. Acta 1, 360 (1967). 2. O. A. Serra, M. Perrier, V. K. Lakatos Osorio and Y. Kawano, lnorg. Chim. Acts 17, 135 (1976). 3. Y. Hase and Y. Kawano, Spectrosc. Lett. 11, 161 (1978). 4. W. J. Geary, Coord. Chem. Rev. 7, 81 (1971). 5. L. C. Thompson, Complexes, in K. A. Gschneider and L. Eyring, Editors, Handbook on the Physics and Chemistry of Rare Earths, North Holland Publ. Co., New York (1978). 6. D. K. Koppikar, P. V. Sivapullaiah, L. Ramakrishnan and S. Soundararajan, Struct. Bonding (Berlin) 34, 135 (1978). 7. L. B. Zinner and G. Vicentini, lnorg. Nucl. Chem. Lett. 7, 967 (1971). 8. K. Nagase, H. Yokobayashi, A. Iwase and K. Sone, Thermochim. Acta 17, 335 (1976).

1.inorg,nucl.Chem.Vol.42,pp. 932-935 PergamonPressLtd.,1950. PrintedinGreatBritain

Oxidation studies--HI. Oxidation of lactic acid by peroxydisulphate catalysed by Cu(lI) ion (Received 8 February 1979; received .for publication 7 September (1979) Cu(II) has been reported as a catalyst in a few peroxydisulphate oxidations[I-7]. Kinetic studies suggest that catalysis occurs where the organic substrate can serve as a ligand (loc. tit). Lactic acid is known to form complexes with copper(II)[8-12]. Therefore, this reaction was selected for a kinetic study to determine the mechanism operative in copper(lI) catalysed S2Os2- oxidations. The uncatalysed and the Ag(I)-catalysed oxidation of lactic acid has already been reported [13, 14].

EXPERIMENTAL All chemicals were either "AnalaR" or E. Merck G.R. Kinetics were followed by estimating residual peroxydisulphate iodometrically, at different intervals of time [13]. The $2032- equivalents of Cu(II) concentration (I>5× 10-4 moles/litre) in an experiment, in terms of titre volume (of 0.04 N), have been substracted from the observed titre volume values to obtain ( a - x). At lower Cu(lI) concentrations it was not necessary. The rate (R) and first order rate constant (k) were evaluated as previously [6]. RESULTS Stoichiometry. The stoichiometry was verified by allowing a solution containing 0.01 M lactic acid, 0.04 M K2S208 and 2.0 × 10-4 M CuSO4 to react for 3 hr at 55°C. The decrease in peroxydisulphate concentration was ascertained and a blank was run simultaneously. The results conform to the equation, CH3CH(OH)COOH + 2K2S208 + H20 = CH3COOH + KHSO4 +CO~. The main reaction product, acetaldehyde, was identified in the reaction mixture by conversion into 2,4-dinitropbenylhydrazine by a spot test[15]. The rate law. The results of the kinetic run at 55°C are given in Table I.

Table 1. First order rate constant in Cu(II)---catalysed oxidation of lactic acid Time sec 0 600 1200 1800 2250 2700 3600 4500 5400 6300 7200 8100 9000 Mean Slope value

Volume of 0.04 N Na2S203 (S'zOs2-) ml moles 1-t 4.95 4.63 4.39 4.00 3.08 2.80 2.11 1.67 !.29 1.10 0.94 0.71 0.62

0.0198 0.0185 0.0176 0.0160 0.0123 0.0112 0.0084 0.0067 0.0052 0.0044 0.0038 0.0028 0.0025

tMean calculated hereafter. (Lactic acid)o = (K2S2Os)o = 0.02 M, Temp. 55°C.

107R moles 1-1 sec -~ -21.3 18.7 21.0 33.2 31.8 31.5 29.2 27.2 24.5 22.3 20.7 19.2 25.0

10Sk sec -~ -ll.I 10.0 I 1.8t 21.2 21.2 23.7 24.3 24.3 23.7 23.2 24.0 23.2 23.2 24.0

(CuSO~)o = 0.0001 M,

It appears that the first order peroxydisulphate decomposition is disturbed initially for a period from 600 to 1800 sec, whereafter a fair constancy in k is obtained. The concentration-time curve is initially S-shaped, typical of autocatalytic reactions. Such kinetic features are reproduced at other concentrations. It is presumed that the reaction starts as an uncatalysed one and after a lapse of time a catalysed reaction starts; after about 1800 sec both the reactions occur simultaneously. This view is supported by the results obtained with an uncatalysed oxidation under