Chaurasia, S. C.

Maurya, R. C.

Sarkar, S.

Srivastava, S. K.

English

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INDIAN J. CHEM., VOL. 15A, AUGUST 1977A perusal of Table 2 reveals that the value ofkl" decreases on increasing the concentration ofTriton X-IOO. From this it follows that irrevers-ible electrode processes tend to become more sowhen Triton X-lOO is added in increasing amounts,The observations on the variation of 'ana' andk/h with increasing concentrations of Triton X-IOOa~e in conformity with the views of Meites->.According to him the most common effect of non-ionic maximum suppressors (such as Triton X-IOO)is to decrease the rate constant klh' and the valueof «n« is also decreased.Triton X-lOO with well known surface activeproperties is likely to be adsorbed on the mercurysurface. This is further confirmed by the decreaseof the interfacial tension, measured by the droptime mcthod-", on the solution-mercury interface.The adsorbed molecules displace ions from theHelmholtz layer, thereby altering the charge distri-bution in the double layer and they may alsodisplace the reaction surface away from the elec-trode. Both these effects alter the potential at thereaction surface. Thus a bridge that may serve toeffect the electron transfer from the electrode to anion at the reaction surface when the maximumsuppressor is absent may become impossible to beconstructed when it is present.Thanks are due to Dr S. N. Dubey, Principal,for providing necessary facilities and to the UGC,New Delhi, for the award of contingency grant toone of them tM.S.).References1. COLtCHMAN,E., J. Am. chem. Soc., 72 (1950), 4036.2. KOUTECKY,J., Chem. Listy, 47 (1953), 323; Colin Czech.chem. Commun., 18 (1953), 597.3. DELAHAY, P., J. Am. chem. Soc., 75 (1953), 1430.4. MATSUDA,H. & AYABE, Y., Z. Elektrochem., 63 (1959),1164.5. KORYTA, J., Electrochim: Acta, 6 (1962), 67.6. GELLINGS, P. J., Z. Elektrochem. Ber. Bunsenges. Phys.cu-«, 66 (1962), 477, 481, 799; 67 (1963), 167.7. GAUR, J. N. & JAIN, D. S., Rev. Potarogr., 14 (1967),206.8. GAUR, J. N., JAIN, D. S. & KUMAR,A., Indian J. Chem.,13 (1975), 165.9. GOTO,R. & TACH!, 1., Proc. intern. Polarogr., 1 (1951),69.10. JHA, S. K. & SRIVASTAVA,S. N., Z. Naturforscli., 30b(1975), 859.11. DELAHAY,P., New instrumental method in electrochemistry(Interscience Publishers, New York), 1954, 33.12. MEITES, L., Polarographic techniques (Iriterscience Pub-lishers, New York), 1965, 324.13. ZUMAN,P. & KaLTHOFF, I. M., Progress in polarograph v,Vol. I (Interscience Publishers, New York), 1962, 88.Dimeric Halo Complexes of Cr(IV)S. SARKAR,R. C. MAURYA,S. C. CHAURASIA&S. K. SRIVASTAVADepartment of Chemistry, T.D. College, j aunpur 222002Received 29 September 1976; accepted 10 January 1977Stable dimeric complexes of Cr(IV) of the type[Cr(OH).X2Py], (X = CI, Br, I) have been prepared bythe alcoholic reduction of halochromatc(VI) in thepresence of pyridinium hydrohalide in pyridinemedium. The complexes have been characterized onthe basis of reflectance, IR and magnetic moment data.744ONLY a few complexes of chromium(IV) areknown'>, In the present investigation wehave observed that the alcoholic reduction ofhalochromate(VI) in the presence of pyridiniumhalide ill pyridine medium leads to the formationof stable dimeric complexes [Cr(OH)2X2PY]2 (X=Cl,Br, I) of chrorniumfl v). An intermediate anionicchloro-cornplex, K2[Cr(OHhCIPyO]2 has also beenisolated using less quantity of chloride.These complexes were prepared by dissolvingpotassium halochromatetv'I) and correspondingpyridinium hydrolralide in excess of pyridine Con-taining a little water. On the addition of excessethanol or methanol, the product started toseparate out as brown insoluble solid within an hourat room temperature. The mixture was kept over-night and then filtered under suction, the precipi-tate washed with water, alcohol, acetone respectivelyand dried in vacuo [yield 80% on the basis ofchromium(VI) used in each case]. The in termediatechloro-complex, K2[Cr(OH)2C1PyO]2 was isolatedwithout adding Py.HCl in the reaction mixture.After standing overnight the deep brown solutionwas treated with excess of acetone to precipitatethe compound. It was dissolved in alcohol andreprecipitated by adding acetone. Addition ofPy.HCI into the alcoholic solution gave an insolubleproduct.The formulation of these complexes is based onsatisfactory elemental analysis, isolation of theintermediate anionic complex, their disproportion a-tion reaction with alkali, their inability to formany AgX on trituration with aqueous AgN03, readyexpulsion of pyridine from these compounds bythe action of NH3 to give corresponding amine com-pounds, no reaction with H202 (iodo compoundshows catalytic decomposition of H202 and onstanding liberates iodine). The compounds areparamagnetic ([LetI = 2·80 BM at 24°). Their re-flectance and IR spectral data are given in Table 1.The assignments of the IR bands in 800-920 regionfor Cr-O-H group is supported by the appearanceof only v(OH) with the absence of any 3(H-O-H).Nevertheless, any oxo-grouping, hydroxo or oxo-bridging is difficult to visualize in these complexeson the basis of other observations, This assign-ment is consistent with the evidence for such a bandin certain Mo(IV) complexes".TABLE 1 - REFLECTANCEAND IR SPECTRALDATA OF THECOMPLEXESComplex Amal< (nm) ImportantIR bands(cm-1)t[Cr(OH).Cl.Pyh 262, 293, 403, 500, 660 3410(s, br),905(5), 800(s)[Cr(OH).Br.Py]. 256,285, 397, 500, 665 3400(s, br),920(s), 830(s)[Cr(OH).I.PY]2 256, 295, 394, 575, 778 3390(s, br),917(5). 815(s)K[Cr(OH).CIPyO].* 262, 388, 488, 690· 3420(s, br},912(s), 825(s),770(s)'Reflectance spectrum taken in water.tCoordinated pyridine bands are excluded.The authors wish to thank Dr P. K. Singh,Principal, for laboratory facilities, Prof. R. P.Rastogi of Gorakhpur University for encourage-ment and to the UP State Council of Science andTechnology for financial assistance.References1. WIEDE, O. F., Chern. Ber., 32 (1899), 378.2. ALYEA, E. C., BASI, J. 5., BRADLEY, D. C. & CHISHOLM,M. H., J. chem. Soc., (A) (1971), 772-3. BASI, J. 5., BRADLEY, D. C. & CHRISHOLM, ;,,1. H., J.chem, Soc., (A) (1971), 1433.4. SIEBERT, G. & HOPPE, W., Z. Naturfir, 58 (1970), 95.S. POEL, J. V. D. & NEUMANN, H. :M., Inorg. Chem, 7 (1968),2086.Reaction of Bis( diethyldithiocarbamato)nickel(I1) with 4-Methyl- &4- Vinyl-pyridinesG. C. PRADHAN & D. V. RAMANA RAoDepartment of Chemistry, Regional Engineering CollegeRourkela 769008Received 15 March 1976; revised 16 February 1977accepted 6 March 1977Bis(diethyl dithiocarbamato)nickel(I1) whcn reactedseparately with 4-methylpyridine and 4-vinylpyridine(L) in ethanolic medium forms compounds having thecomposition [Ni(dtc)..L]. They are dlamagnettc andnon-electrolytes. Infrared spectra indicate the pre-sence of bonded Ii~ands. The complexes are penta-coordinated, as revealed by their electronic absorptionspectra with nickel atom surrounded by four sulphurand one nitrogen donor atoms.I~ Ni(II) complexes tetra- and hexa-coo.j dir:atio,nIS a common feature, and penta-coordination tsrare. The preferred coordination number dependsupon the polarizability of the ligands reacting withthe metal ion. It is, therefore, WOl thwhile to seewhether this less common penta-coordination can bestabilized by providing a hetero-donor atom environ-ment round the nickel ion. With this in viewthe reaction of bis(diethyl dithiocai bamato )nickel(II)with 4-methyl- and 4-vinylpyridines has been studiedand the complexes formed isolated and characterized.Ethanolic solution of nickel chloride was reactedwith ethanolic solution of sodium diethyl dithio-carbamate (Na.dtc) in the ratio 1: 2. The preci-pitated light green compound was suction-filtered,washed with ethanol and dried in vacuo. Thecomposition of this compound was established to beN i(dtc)2 by elemental analysis and infrared spectralstudy. This freshly prepared complex was reactedwith 4-methylpyridine and 4-vinylpyridine separatelyin ethanolic medium in the stoichiometric ratios of1:1 and 1: 2. The reaction mixture was refluxed for6 hr and the resulting products were suction-filtered,washed with ethanol followed by ether and thendried in vacuo. (i) Ni(dtc)2.4-me.py (Found: Ni,13·6; S, 29·0. Calc.: Ni, 13-4; S, 28'6%), m.p.>300; AM 0·5 mhos. Ni(dtc)2.4-vi.py (Found: Ni,12·8; S, 27·8. Calc.: Ni, 12·8; S, 28·2%), m.p.>300; AM 0·6 mhos.51 (1'.174), "/IU.6. FLINT, C. D. & GOODGAME, M., J. chem, Soc., (A) (1967),1718.7. FLINT, C. D. & GOODGAME, M., J. chem. Soc., (A) (1966),745.8. TRAMER, A., J. chsm. Phys., 59 (1962), 232.9. MARCOTRIGIANO, G. & BALTI5TUZZI, R., J. inorg. nucl.Chem., 36 (1974), No. 12.NOTESMcCormick and Roy! have reported that Ni(II)forms stable, planar, diamagnetic and tetracoordinatedcompounds [Ni(cltc)2] with a series of dithiocarba-mates. Nickel(II) ~-c1iket()llates on Icaction withnitrogen" and sulphur" donor ligands were found byus to give hexacoordinated compounds, Ni(~-dik)2L2'Bis(diethyl dithiocarbamato )zinc(II) was reacted" withsome substituted pyridincs and several pentacoordi-nated compounds having the composition Zn(dtc)2Lwere obtained. Dithiocai bamate is a uni-negative,bidentate ligand and so neutral ligands cannotreplace it; they can be simply added on if therequirements are sat isfied. Neutral bidentate nitro-gen donor ligands like (/.,(1.' -dipyridyl and o-phcn-anthroline were reacted with N i(dtc)2 but with noconsequence. So, it is clear that the coordinationnumber cannot be increased to six. In the presentinvestigation when several neutral unidcntate nitro-gen donor ligands were tried, reaction took placeonly with 4-methylpyridine and 4-vinylpyriclineresulting in the addition of only one mole of theligand. Even when excess of ligand in the ratio 1: 2was taken, only one mole of the ligand was added.This explains why there was no reaction when abidentate ligand was used. Very low values ofmolar conductance, AM (0·5 mhos) in nitrobenzene(10-3M solution) indicate the non-electrolytic nature.The compounds are diamagnetic as expected for apentacoordinated nickel(II) compound involving3d4s4p3 hybrid orbitals.In diethyl dithiocarbamate, v(C-N) was reported"at 1480-1550 and v(C-S)6 at 989-1006 cm". Thesample of Ni(dtc)2 prepared by us exhibits bands at1525 and 985 crrr! corresponding to v(C-N) andv(C-S) respectively. In the 4-methylpyridine and4-vinylpyridine adducts, the vC-N and vC-Sfrequencies are observed at 1520, 1518 and 980,995 crrr? respectively. It is, therefore, clear thatdithiocarbamate ligands in the complex remainundisturbed. In addition to the absorption bandsdue to diethyl dithiocarbamate, characteristic bandsdue to 4-mcthylpyridine and 4-vinylpyridine are alsoobserved in the complexes Ni(dtc)2'L. There isno evidence, either analytical or spectral, for thepresence of a coordinated water molecule. Hencethe complexes under report are definite examples ofpenta-coordination of nickel(II) being surrounded byfour sulphur atoms and one nitrogen atom.Pentacoordination of nickel(II) gains further sup-port from electronic spectral data. Sacconi hadshown? that in penta-coordinated configuration, theground state term of the nickel(II) ion splits into arelatively large number of terms on lowering thesymmetry as compared to that of tetrahedral oroctahedral configuration. Bertini reported'' absorp-tion bands at 8000, 10000, 13000 and 16000 em? andpostulated the existence of five-coordinate high spinnickel(II) complexes with mixed salicylaldimineligands. It was also suggested? that four-coordi-nated planar complexes of niekel(II) do not showappreciable absorption below 18000-20000 cm ".In the present investigation, the electronic spec-trum of Ni(dtc)2(4-vi-py) in CHCl3 exhibited maxima(E) at 11420 (57), 12500 (51), 16600 (150), 17540(142) and 21275 (340) ern? while Ni(dtch(4-me-py)745References1. WIEDE, O. F., Chem. Ber., 32 (1899). 378.2. ALVEA, E. C., BASI, J. 5., BRADLEY, D. C. & CHISHOLM,M. R., J. chem. Soc. (A), (1971), 772-*Department of Chemistry, Gorakhpur University,Gorakhpur.747

Dimeric Halo Complexes of Cr(IV)

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Dimeric Halo Complexes of Cr(IV)

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