Chaurasia, S. C.

Maurya, R. C.

Sarkar, S.

Sharma, B.

Srivastava, S. K.

English

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Even though most of the IR absorption bandsdue to free ligands are modified in the complexes, afew important bands have been assigned ar:d con-clusion regarding the bonding has been denved onanalvsis of these bands.v(C=S) in dithioureas occurs around 780 crrr-which is shifted in the complexes to --730 cm!indicating a decrease in bond order and providingan indirect evidence for bonding through the sulphuratom. Consequent upon bonding through sulphur,vC-N which appears __ 1100 cm'" in ligands isshifted to 1120 cm". vN-H of the free ligandswhich occurs ,....,3200 em? does not shift in thecomplexes indicating absence of coordination throughnitrogen, except in cases of some chloro-complexeswhere the band broadens possibly due to hydrogenbonding of the anion with the N-H proton. Inaddition to it v(M-S) appears at 320-330 em?providing a direct evidence of bo~di.ng ~hroughsulphur. Though it is possible to distinguish bet-ween octahedral, tetrahedral and planar comple~esby the position of the metal t.hioun~a s~retchlI~gvibrations, metal-sulphur stretching vibratIon~ dIdnot permit the deduction of the stereoChemI?try,as the presence of metal-anion stretches complicatethe vibrational analysis. This has been copfim;edby earlier workss-? on metal sulphur vlb.~atIonfrequencies of thiourea complexes. v(C=N) m thecase of thiocyanato complexes is observed ~round,....,2150 cm- an increase of 70-80 em? relative tofree thiocya~ate, indicating either.a t.ermin~ sulphurbonding or the presence of a bridging thiocyanategroups. .The complexes may have two alternative stereo-chemistries, i.c. (a) tetrahedral or (b) ?ctahedral,depending on the way the anion coordinates. Ifthe thiocyanate group is terminal sulphur bondedand the halogens are not bridging the comp~'::xesmay have a tetrahedral geometry .on the baSIS oftheir composition. But in thc far mh:ared spectra,the metal halogen stretching frequen~les. appear at220-260 crrr", providing a probable indication forthe presence of bridging halogen atoms. Furt~crmost of the complexes arc amorphous, have .hlghmelting points and are either insoluble o~-span~glysoluble in common organic solvents. ThIS providesevidence for polymeric nature of the compounds.Hence, the possibility of an octahedral. str~ctureinvolving a halogen or pscudo-~alog~n bridge IS ~otruled out. This is in conformity WIth some earlierobservations" on thiourea complexes.References1. AHRLAND, S., CHATT, J. & DAVIES, N. R, Quart. Rev.,11 (1958), 265. .2. NARDELLI, M. & CHIERECI, J., Rieerea su.. 29 (1959),1733.3. CASS, R C., COATES, G. E. & HAYTER, R G., J. chem.Soc., (A) (1955), 4007.4. OLIFF, R W., J. chem. Soc., (A), (1965). 2036.5. RATH, P. C. & MOHAPATRA, B. K., J. Indian chem: Soc.,51 (1974), 710. )6. FLINT, C. D. & GOODGAME, M., J. chem, Soc., (A) (1967 ,1718. 1 )7. FLINT, C. D. & GOODGAME, M., J. chem. Soc., (A) ( 966 ,8 T~~~R A. J. chim. Phys., 59 (1962). 232. . 19." MARCOT~IGI~NO, G. & BALTISTUZZI, R, J. inorg, nua,cu«, 36 (1974), xo. 12.NOTESPreparation of a New Oxotetracyano-(pyridine )chromate( IV) AnionS. SARKAR, B. SHARMA-, R C. MAURYA, S. C. CHAURASIA &S. K. SRIVASTAVADepartment of Chemistry, T. D. College, Jaunpur 222002Received 8 October 1976; accepted 21 March 1977A new hexacoordinated Cr(VI) anion, [CrO(CN).Py)·-,Isolated as potassium salt has been prepared andcharacterized on the basis of IR data.C011,1:PLEXES of chromium(IV) are rareH. Inthis note vn: report the isolation and charac-terization of a new hexacoordinated chrornium(IV)anion, [CrO(CN)4Py]2-, as potassium salt.Pyridinium chlorochromatetv l}, PyH[Cr03C!J (5 g)was dissolved in pyridine (5 ml) and to this wasadded ethanol (20 ml] and solution kept overnightto give a brown solution. To this, ethanolic solutionof KCN (6·5 g) was added and heated at 150° for.10min. On keeping the resulting deep red soluho~overnigh t. the complex separated c!.s deep red 011wnich was purified by repeatedly dissolvin g it illlittle water and reprecipitating by adding ethanoltill the Wash liquor was cyanide free, finally addingabsolute ethanol to get a brown powder which wasdried over CaC12 un der reduced pressure; yield 60%{Found: K. 22·70; Cr, 15·31; N, 19·85; H20WlOs drying), 5'20%. Kl[CrO(CN)4Py].H~O requiresK. 22·52; Cr, 14·97; N, 20·16; H20, 5-18%}.The salt is hygroscopic and is highly soluble inwater, being insoluble in common organic solvents.The aqueous solution is red in colour which slowlydecomposes with the expulsion of HeN. In KCNsolution it is stable. Acid decomposes it imme-diately with disproportionation to Cr(III} and Cr(VI)while in alkaline medium it decomposes only onprolo.i g keeping or warmii- g. Its fresh aqueoussolution gives insoluble coloured precipitates withmany metal ions Cu2+ (greenish brown), C02+ (orangebrown), Ni2+ (bright brown), Mn2+ (orange), Ba2+(flesh coloured from concentrated solution), Ag+(reddish brown).The room temperature (24°) magnetic momentof the complex is 3·0 BM consistent with the d2_configuration of Cr(IV). The aqueous electronicspectrum in the presence of traces of free KCNshows bands at 20-41, 26·67, 38·00 and 38·99 kK.The first band appears as a shoulder. The bandsat 38·00 and 38·99 kK are more intense. Its IRspectrum (nujol and KBr) shows important bandsat 3550, 3440, 3130, 1620-25, 905, 625, 525, 450,430 and 335 cm+.The appearance of a sharp band of 2130 due vCNand at 905 crrr! due to vCr = 0 suggests the coordi-nation of pyridine trans to Cr = ° group. All theother bands observed are in conformity with earlierassignments of similar pyridine complexes--".References1. WIEDE, O. F., Chem. e«, 32 (1899), 378.2. ALYEA, E. C., BASI, J. S., BRADLEY, D. C. & CHISHOLM,M. H., J. chem. Soc. (A), (1971), 772.-Department of Chemistry, Gorakhpur University,Gorakhpur.747INDIAN J. CREM., VOL. 15A, AUGUST 19773. BASI, J. S., BRADLEY, D. C. & CHRISHOLM, M. R., J.chem, SOC. (A), (1971), 1433:4. SIEBERT, G. &: HOPPE, W., Naturwissencllaften, 58 (1970),95.5. WIBERG, K. B. & MUKHERJEE, S. K., J. Am. chem. Soc.,96 (1974), 1884, and references therein.6. SARKAR, S., MAURYA, R. C., CHAURASIA, S. c., SRIVASTAVA,S. K., Indian J. Chem., 15A (1977), in press.7. GILL, N. S., NUTTAL, R. R., SEAIFE, D. E. & SHARP,D. W. A., J. inorg, nucl. Chem., 18 (1961), 79.8. JONES, L. H., Inorg. Chem.• 2 (1963). 777; 4 (1965). 1472.Terdentate Llgands: Part 11- OctahedralNi(II), Co(lI) & Cr,III) Complexes ofSchiff Bases Derived from 2-(2'-Amino-ethylj pyr-idineD. K. RASTOGI & P. C. PACHAURIDepartment of Chemistry, Meerut College, Meerut 250001Received 18 December 1975; revised 22 February 1977accepted 1 March 1977Preparation and characterization of a series of newNi(I1) and Co(I1) complexes of the type [ML2],whereL = tridentate Schiff base derived from 2-(2'-amino-ethyl)pyridine and salicylaldehyde, substituted salicyl-aldehyde (X-Sal, X = 5-CI, 5-N02' 5,6-Benzo) (X-Salaep), o-hydroxyacetophenone (Hapaep), o-hydroxy-propiophenone (Hppaep) or o-hydroxybutyrophenone(Hbpaep) have been described. Chromium(III) com-plexes of the composition [CrL2] CI are also reported.Analytical, conductance, magnetic, electronic and IRspectral data show that all the complexes have octa-hedral geometry.EARLIER we have reported the preparationsand characterization of several transition metalcomplexes of 2-(2'-amuloethyl)pyridillel-3. Now wereport here the preparation of Ni(II), Co(II) a.idCr(III) complexes with tridentate Schiff bases(I) derived from 2-(2'-aminoethyl)pyridine and theircharacterization on the basis of analytical, conduc-tivity, magn etic, electronic an d IR spectral studies.Complexes with X-Salaep - Salicylaldehyde andsubstituted salicylaldehyde (0·025 mole) and 2-(2'-aminoethyllpyridin e (0·025 mole) in ethanol weremixed and stirred on a magnetic stirrer for 15 minat 60-70°. After the addition of metal chloride(0'01 mole) in ethanol and an aqueous solution ofsodium acetate (0·02 mole) the reaction mixturewas stirred for 1 hr a-id then refluxed for 3-5 hr.The contents were kept il a silica dish for slow crys-X y©t.6::O:N-CH2I' !I ,'--' OH ©H~_\N' I\._,:rx- Schllpi Y= H, X= H.S-CI,S-N02 Or 5, 6- BenzD~cpc.p; X-H, Y=CH3HPP.'ltp; x= H, Y= C1HSHbpcep; X=H. VaC3H7748tallization and recrystallized from ethanol; yield80-85%.Complexes with Hapaep - A mixture of 2-(2'-aminoethyl) pyridine (0·025 mole) and o-hydroxy-acetophenone (0·025 mole) in absolute ethanol wasstirred and refluxed at 70° for about 3-4 hr. Tothis was added an ethanolic solution of metal chloride(0·01 mole) and the con ten ts refluxed for about anhour. A solution of sodium ethoxide was addeddropwise and the reaction mixture further refluxedfor 8 hr with constant stirring. The contents wereallowed to stand overnight when crystals of thecrude complex: were obtained which were recrys-tallized from ethanol: yield .--.75%.Complexes with Hppaep - They were preparedby a procedure similar to that used for Hapaepcomplexes using o-hydroxypropiophenone (0·025mole) and reaction mixture was refluxed for 12 hrat about 70° and then concentrated in vacuo. Itwas refrigerated for two days when the crystals ofthe crude product were obtained. The compoundwas recrystallized twice from ethanol; yield 55-60%.Complexes with Hbpaep -- These were preparedas above employing o-hydroxybutyrophenone (0·025mole) an d the reaction mixture was refluxed at 70°for 18 hr. Concentration of reaction mixture andsubsequent refrigeration did not produce crystals.The solution was evaporated in vacuo and onrefrigeration for several days solid complexes wereobtained. These were recrystallized from ethanol;yield 45-48%.Analytical, magnetic moment, melting point andconductivity data of the complexes are listed inTable 1.The magnetic moments observed for Ni(II)(2·96-3'42 BM), Co(II) (4.85-5·12 BM) and Cr(III)(3'70-3·82 EM) complexes are consistent withoctahedral symmetry for these complexes. Theincrease in the magnetic moment from that of spin-only value in the case of Ni(II) complexes may bedue to some "mixing in" of upper states via spin-orbit coupling". Higher orbital contribution foroctahedral Co(II) complexes of 2-(2' -arniuoethyl)pyridine and other 2-substituted pyridine ligandshas been observed by Rastogi! and Sutton et al»,The value for Cr(III) complexes is slightly less6than that expected for three unpaired spins in Ohenviron men t.Judging from the greater value of magneticmoment for X-Salaep (where X = H, 5-0, 5-N02and 5,6-benzo) complexes of Ni(II) (3·31-3.42 BM),Co(II) (5·02-5-12 BM), Cr(IIl) (3.80-3.82 BM) ascompared with the value of Hapaep [Ni(II), 3'01;Co(II) 4·95; Cr(III) 3·77 EM], Hppaep [Ni(II), 2'26;Co(II), 4·92; Cr(III), 3·75 EM] and Hbpaep [Ni(II),2·96; Co(II), 4·85; Cr(III), 3·70 EM] complexes; itmay be concluded that the geometry of the lattercompounds is distorted from the regular octahedron.Three bands have been observed in the electronicspectra of Ni(II) complexes in the region (10400-8980 cm+) [VI' 3A2g(F)-+3T2g(F)J. 16785-14000 crrr+)[V2' 3A2g(F}-+3TIg(F)] and (27515-25050 cm') [va.3A2g(F)-+3TJg(P)] indicating Oh geometry for thesecomplexes. In the case of Co(lI) complexes threebands observed in the region 8850-9850, 17000-19800 and 20850-215000 crrr ' may be assigned to

Preparation of a New Oxotetracyano- (pyridine)chromate(IV) Anion

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Preparation of a New Oxotetracyano- (pyridine)chromate(IV) Anion

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