r

In the PMR spectra (chemical shift in a, ppm)for these complexes in CDCla, biphenyl protonsappear as doublet, triplet and doublet between (6.08and 7.67). Methyl group in acetato derivativeappears as a singlet at (2.1); ethyl group in propio-nato derivative appears as a three proton triplet at2.0 and a two-proton quartet at 2.4. In butyrattrderivative CHa appears as a triplet at 0.82, CH2 asa triplet at 2.3 and ,B-CH2 as a multiplet at 1.6. Un-resolvable close multiplets are obtained in pentanoatoand hexanoato derivatives at 7.5 and 1.27 respective-ly. Signal due to phenyl protons of benzoato deri-vative gets mixed up with that of biphenyl protons.The chlorosubstituted methyl groups in mono-chloro and dichloroacetato derivatives show singletat 4.2 and 5.9 respectively. The PMR spectra indi-cate that the complexes are of good purity and labileat ambient temperature (.-30°C). However at lowtemperatures the complexes are expected to be rigid.References

1. INGHAM.R. K .. ROSENBERG.S. D. & GILMAN.H .• Chem.Rev .• 60 (1960). 459.

2. ANDERSON.H. H .• Inorg. Chem .• 3 (1964). 912.3. HENDERSON.A. & HOLLlDAY.A.K .• J. organometal. Chem .•

4 (1965). 377.4. ZYKOVA.S. K. & NAUMOVA.I. Y.• Chem, Abstr .• 77 (1972),

5580.5. Carlisle Chemical Works. Chem. Abstr., 75 (1971). 140984.6. WIBERG. E. & BEHRINGER, H .• Z. anorg. a/lg. Chem .•

329 (1964). 290.7. BABOLI. E. RAJEWSKI, M., MALESNICKI.W.• KOWALSKI,

M. & PAZGAN. A .• Chem, Abstr .• 84 (1976), 5149.8. TALALAEVA,T. Y., ZAITSEVA.N. A. & KOCHESHKOV.K. A .•

J. gen. Chem .• 16 (1946). 901.9. NAKAMOTO.K .• Infrared spectra of inorganic and coordina-

tion compounds (Wiley-Interscience, New York). 1970.222.

10.0KAWARA, R., WEBSTER.D. E. & Rocaow, E. G.,J. Am. chem, Soc. 82 (1960). 3287.

11. SATO. H. & OKAWARA.R .• Int. Symp: Mol. Struct. Spect,Tokyo. Japan, September 1962.

12. MAEDA,Y., DILLARD,C. R. & OKAWARA,R .• Inorg. nucl.chem. ua.. 2 (1966). 197.

13. MAEDA. Y. & OKAWARA.R., J. organometal, Chern.•10 (1967). 247.

Mixed Ligand Cobalt(III) Complexes Obtained by Sub-stitution in Dinitrobis( acetylacetonato )cobaltate(III)

by Sulphur & Nitrogen Donors

L. K. MISHRA & HIMANSHUBHUSHANDepartment of Chemistry. Patna University, Patna 800 005

and

N. K. JHA*Department of Chemistry. lIT. New Delhi 110016

Received 12 May 1980; revised and accepted 14 August 1980

Mixed ligand complexes with the formulation [Co(acac).-(NO.)L].nH.O (n = 0, 1 or 2) have been prepared by the substi-tution of a nitro group in Na[Co(acac).{NO.).] by either a sulphurdonor (thloacetamide, thiobenzamide, thiourea, phenylthiourea,ally Ithiourea, ethylenethiourea or mercaptobenzimidazole) or anitrogen donor (2-aminopyridine, 3-aIninopyridine, 2-amino-4-methylpyridine, 4-cyanopyridine, 2-aIninopyrimidine, 2-aInino-

I

NOTES

4-methylpyriInidine or benzotriazole). The complexes have beencharacterized on the basis of electronic and IR spectra and roomtemperature magnetic measurements. The complexes are lowspin d" (pseudo-octahedral) systems having trans-configurationwith a little residual paramagnetism.

IT has been reported- that a nitro group of sodiumdinitrobistacetylacetonato )cobaltate(UI) can be

substituted by ammonia Or a suitable nitrogencontaining heterocyclic base forming neutral com-plexes of the type [Co(acacMN02)(amine)]. In thepresent investigation we have carried out such substi-tution by some sulphur and nitrogen donor ligands toobtain complexes of the general formula [Co(acach-(N02)L].nH20 where L is a S or N donor and n=O,1 or 2.

Sodium dinitrobistacetylacetonato )cobaltate(III)land benzotriazole" were prepared by reportedmethods, Other ligands were supplied by E. Merckor B D H.

The complexes, [Co(acacMN02)L].nH20 wereprepared by treating an aqueous solution of sodiumdinitrobis(acetylacetonato)cobaltate(UI) (1.25 g in30 ml H20) with an aqueous ethanolic, aqueousmethanolic or methanolic solution of the appro-priate ligand in 1:2 molar ratio. The complexes pre-cipitated out on mixing and stirring at room tem-perature. For some sulphur donor ligands, heatingfor 30 min at 40-50°C was required. The complexeswere washed with aqueous ethanol followed by etherand dried in vacuo over CaClz.

Cobalt in the complexes was estimated as cobaltsulphate after igniting the complex and treating theresidue with cone, HNOa and cone. HzS04.' Nitrogenwas estimated by Duma's semi-micro method. Waterof crystallization was determined by heating thecomplex below 120°C in an oven. The analyticalresults are shown in Table 1.

Magnetic susceptibilities were measured at roomtemperature by the Guoy method using Hg[Co(CNS)4]as the standard. Effective magnetic moments werecalculated after making diamagnetic correction usingPascal's constants". Diffuse reflectance spectrawere recorded on a Hilger and Watts Uvispek spectro-photometer H700 using MgCOa as the reference.Infrared spectra of some of the complexes wererecorded in KBr or Nujol in the range 4000-650em:" on a Perkin Elmer spectrophotometer whilethose of some others were recorded in the range4000-400 cm" at CDRI, Lucknow.

The complexes, [Co(acacMNOJL].nHzO aregenerally insoluble in water but dissolve slightlyin DMF, DMSO and dioxane. They are stable insolid state at room temperature. The hydratedcomplexes lose water molecules below 100°C.

All the complexes are feebly paramagnetic; themagnetic moments vary from 0.60 to 1.20 B.M.Majority of the reported Co(UI) complexes are ofthe low-spin type (t gg) and diamagnetic but in somecases small positive susceptibilities are observed+,In spin-paired octahedral Co(UI) complexes the

415

INDIAN J. CHEM., VOL, 20A. APRIL 1981

TABLE 1 - ANALYTICALRESULTS

Found (Calc.), %Complex

Co N

*X(2-aminopyridine) 14.7 10.5(14.8) (10.6)

X(3-aminopyridine) 14.7 10.5(14.8) (10.6)

X( 4-cyanopy ridine) 14.4 10.2(14.5) (10.3)

X(2-amino-4-methylpyridine) 14.3 10.1(14.3) (10.2)

X(2-aminopyrimidine) 14.7 14.1(14.8) (14.0)

X(2-amino-4-methylpyri- 13.6 13.0midine).H1O (13.7) (13.0)

X(benzotriazole).2H.O 12.8 12.2(12.9) (12.2)

X(thioacetamide) 15.5 7.4(15.6) (7.4)

X(thiobenzamide) 13.3 6.4(13.4) (6.4)

X(tbiourea) 15.4 11.0(15.5) (11.1)

X(phenylthiourea).2H.O 12.0 8.5(12.0) (8.5)

X(mercaptobenzimida- 12.6 8.0zole).2H.o (12.0) (8.6)

X(allyltbiourea).H.O 13.4 9.5(13.5) (9.6)

X(ethylene tbiourea).2H!O 14.0 9.1(13.3) (9.5)

*X = Co(acac).(NO.)

Water

4.2(4.2)7.7

(7.7)

7.3(7.3)7.0

(7.6)4.1

(4.1)8.3

(8.1)

IAH• term is the lowest and the second order Zeemaneffect contributes small paramagnetism (100 X 10-6

c.g.s.jmol) to the complexes" which may account forthe small (.-0.5 B. M.) magnetic moments of thesecomplexes.

Magnetic moments of the complexes containingsulphur donor ligands are found to be higher (0.72to 1.20 B.M.) than those of the complexes contain-ing nitrogen donor Iigands (0.60 to 0.77 B.M.). Inthe case. of complexes containing sulphur donorligands the formation of a little Co(Il) species,Co(acac);:, by decomposition of Na[Co(acach(N00z]during the preparation in hot aqueous methanolicsolution, cannot be ruled out which may accountfor their rather high magnetic moments.

Two reflectance bands are observed in the electro-nic spectra of the complexes, one low intensity bandaround 500nm and another shoulder of high intensityaround 370 nm. The latter band is usually obscuredby the high intensity charge-transfer band, t2u -+1t*(acac)2 reported to occur around 340 nm-. Thebands around 500 nm appear at lower wavelengthsfor complexes containing sulphur donor ligands(465 to 500 nm) than for those containing nitrogendonor Iigands (530 to 545 nm). These bands areassignable to the transition IAIU +- ITIg in octahedralCo~III) complexes=. However, CotHl] is not in aregular octahedral environment in the present comple-xes which are, in fact, cis- or trans-[Co(acac)z(NOJL]

416

I

hence ITIg and IT2U levels are expected to splits>;but no structures are observed on these bands. Ithas been reported that cis- isomers usually show moreintense bands compared to the trans-isomers6c•

Hence, in view of the intensities of these bands beingweak in the present case as in the correspondingpyridine complex [Co(acacMN02)py].2HzO whichhas been assigned trans- configuration on the basisof NMR and IR spectral, the present complexesmay be assumed to have trans-configuration.

Spectra of only six complexes Were recorded up to400 cm" and in these cases the lowering of the"Co-O mode to 420-450 cm" from 466 cm-1 inCotacac), (ref. 7) indicates N or S coordination.One or two more bands observed in the region 405-420 cnr ' may be assigned to "Co-N or "Co-Svibrations.

In the thiourea, phenylthiourea, thioacetamideand thiobenzamide complexes the N-Hfrequenciesremain unchanged compared to those in the freeligands but the "C= S bands are lowered to about710 cm" from ,.....,730 em-I in the free ligands sug-gesting S-coordination8•

The observation that "N-H and "C-N bands ofamino group of the ligands,2-aminopyridine and3-aminopyridine are not affected whereas the "C=Nof tertiary pyridine nitrogen shifts to higher frequen-cies (1610-+ 1625 crrr? and 1605-+1630 cm-I respec-tively) indicates that these Iigands are coordinatedthrough pyridine nitrogen rather than amino nitro-gen9,IO. The situation is reversed in the case of2-aminopyrimidine and 2-amino-4-methy lpyrimidinewhere N-H bands are split on coordination and the"C-N of the amino group shifts to lower frequency(1225 to 1210 em"? and 1215 to 1204 crrr? respec-tively) whereas "C=N of tertiary pyridine nitrogenremains unaffected indicating coordination throughamino nitrogen-'. The "N-H band of free benzo-triazole (,.....,3190 cm") is little affected on co-ordination suggesting coordination through tertiarynitrogen. In cyanopyridine the "C=N (2218 cm")remains unaffected in the complex suggesting co-ordination through the pyridine nitrogen and notthrough N of C=N.

The increase in the asymmetric stretch of freeNO; (1250 to 1380 ± 10em-I) and the near constancyof the symmetric stretch (1335 to 1320±lOcm-l)in the complexes coupled with the absence of the1065 em= band attributed to nitrito group asym-metric vibration suggests N coordination of NO;group-s.

Bailar and Boucher- have concluded from NMRand IR study that [Co(acacMN02ht and [Co(acack(N02)(py)] have trans- configuration. In theabsence of NMR and X-ray crystallographic datain the present investigation, such conclusive infor-mation cannot be drawn about the geometry of thecomplexes. However, the rapid replacement of anitro- group from trans-[Co(acac)iN002]- by aneutral ligand indicates that substitution takes placeby retention of configuration (though, this is notalways true13,14). Further, the similarity of theintensities of the bands in the electronic spectra of

the present complexes with those in the spectrumof trans-[Co(acac)z(N02)(py)] complex also suggestst?ans-configuration.

References1. BOUCHER, L. J. & BAlLAR, re.. J. C., J. inorg. nucl. Chem.,

27 (1965), 1093. •.•.2. NEBER, p. W., HARTUNG, K. & Ruozr, W., Ber. dt chem.

Ges., 58B (1925), 1234.3. WILKINS, R. G. & LEWIS, J.,Modern coordination chemistry

(Interscience, New York), 1964,403.4. FIGGIS, B. N. & LEWIS, J., Progress in inorganic chemistry

Yo!. 6, edited by F. A. Cotton (Interscience, New York),1964, 182.

5. AsMUSSEN, R. W. & BALLHAUSEN, C. J., Acta chem. scand.,11 (1957), 479.

6. LEVER, A. B. P., Inorganic electronic spectroscopy (Elsevier,Amsterdam), 1968, (a) 111 (b) 309 (c) 308.

7. NAKAMOTO, K., FUJITO, J. & MURATO, R., J. Am. chem,Soc., 83 (1961), 1066.

8. NAKAMOTO, K., MORIMOTO, Y. & MARTELL, A. E., J.Am. chem. Soc., 83 (1961), 4533.

9. MCWHlNNIE, W. R., J. chem. Soc., (1964), 2959.10. CHATT, J., DUNCANSON, L. A. & VENANZI, M. L., J.

chem. Soc., (1955), 4461.11. CURRAN, B. C., SEN, B. N., MIZUSHIMA, S. & QUAGLIANO,

J. V., J. Am. chem., Soc., 76 (1956),429.12. NAKAMOTO, K., Infrared and Raman spectra of inorganic

and coordination compounds (Wiley Interscience, NewYork), 1978, 323.

13. ARCHER, R. D. & BAILM, Jr., J. C., J. Am. chem. Soc.,83 (1961), 812.

14. BOUCHER, L. J., KYUNO, E. & BAILER, Jr., J. C., J. Am.chem. ss«, 86 (1964), 3656.

Oxalatooxovanadates(IV)

B. B. BHAUMlK* & R. K. CHATTOPADHYAY

Department of Chemistry, University of Kalyani,Kalyani 741 235

Received 26 May 1980; revised and accepted 18 September 1980

A number of new oxalatooxovanadates{IV) have been isolatedand characterised on the basis of analytical, conductance, mag-netic moment and spectral data. These are of the types MI.[VO(C.O.).]. xH.O [where MI. = Li, Rb, Cs, pyrldiniura, 1/2ethylenediaminium and morphollnium]; M~ [V.O.(C,O.hl.x H.O[where M1 = tetrammethylamonium and ()-picoliniuml;and [Co(NH3).]. [V.O.(C,O.).1.5R20. u, [VO(C.O.).].7H.Ogives the anhydrous compound on heating at 250°C while Rb.-[VO(C,O.).l and Cs.[VO(C20')21 are obtained on drying thehydrates in vacuo over P.O •. Molar conductance values ofderivatives of bisoxalatooxovanadates(IV) and trisoxalatooxova-dates (IV) show the presence of uni-bivalent species in aqueousmedium. In contact with cation exchange resin of H+ form,their aqueous solutions decompose completely. Phase equilibriumstudy of the system K 2C20.-VOC.O.-H.O at 35°C reveals theformation of K,[VO(C.O.).l. 3H,O.

OXALATOOXOV ANADATES(IV) containingV02+ and CP42- in the ratios 1 : 2 and 1 : 1.5

were first reported by Koppel and Goldman- and

I

NOTES

subsequently a number of studies employing IR,TGA DTA and electronic spectral techniques havebeen reported=P. We present here the preparationand characterisation of several more new oxalatoo-xovanadates(lV).

Vanadium, nitrogen, oxalate and alkali metals wereestimated as reported earlier+". Vanadyl oxalatewas prepared by the reaction of vanadium pentoxideand oxalic acid". The IR spectra were recorded on aPerkin-Elmer apparatus in KBr in the region400-4000 cm". TG study was done, using amanually operated apparatus maintaining a rate ofheating of 2°C/ min. Magnetic susceptibility measure-ments were carried out by the Guoy method. Dia-magnetic corrections were applied as described byFiggis and Lewis". The visible spectra were recordedon a spectromom instrument (Hungary, model No.204). The conductances were measured using aPhillips conductivity bridge, type PR 9500, using dip-type platinized platinum electrodes. Ion exchangestudy was done using cation exchange resin(Amberlite IR, 120) of H+ form. The phase equili-briumstudy of the system KzC204-VOC204-H20 wasdone as described earlier" and the results are shownin Fig. 1.

Preparation of the compounds - To requisiteamounts of aqueous vanadyl oxalate, organic bases(vanadyl oxalate : organic base:::::::1 : 2.0) or alkalimetal carbonates (vanadyl oxalate : alkali metalcarbonates:::::::1 : 1) acidified with aqueous oxalicacid or [Co(NHa)6h (C:P4)3 {vanadyl oxalate :[Co(NH3)6]Z (CZ04)3 = 1 : 0.6} were added. Yellowcrystals of hexamminecobalt(III) salt were obtainedon keeping the mixture overnight. In other cases bluecrystals were obtained on evaporating the mixtureson a water-bath. These were filtered, washed withalcohol and dried in air. In case of ethylenedia-minium compound a viscous liquid resulted onconcentration which on treatment with acetone-watermixture (2 : 1) gave blue crystals.All the compounds, except the hexamminecobalt (III)

compound, are highly soluble in water. All are.insoluble in common organic solvents. Dehydrationof hydrated Li, Rb and Cs oxalatooxovanadates(IV)in vacuo over P205 results in the formation of lithiumoxalatooxovanadate tetrahydrate and anhydrousrubidium and cesium compounds respectively. Themolar conductance values of the aqueous solutionsof (PyH)z [VO(Cz04)J·3H20 and [(CH3)4NJa[V20Z-(Cz04h].3.5Hp are 246.9, 223.9 and 243.9 ohm=ern" rnol? indicating the uni-bivalent electrolyticnature of the complexes. When the aqueous solutionsof oxalatooxovanadates(IV) were passed through acation exchange resin of H+ form, the complexesunderwent complete decomposition and oxalic acidwas obtained quantitatively as effluent, Vanadiumremained absorbed probably as precipitated V02 inthe column since it could not be eluted completelywith NaCI or NH4Cl salt solution. The magneticmoments of the monovanadyl oxalato complexes(Table 1) lie within the range 1.91~1.99 B.M.indicating the quadrivalence nature of the vanadiumin these complexes. The subnormal magnetic mo-

417

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