Indian Journal of ChemistryVol. 23A, March 1984, pp. 258-259

Interaction of Chromium(III), Iron(II &III) & Uranium(VI) with Potassium

Octacyanomolybdate(IV & V) & PotassiumOctacyanotungstate(IV & V)

S I ALl* & ZAK!R MURTAZA

Department of Chemistry, Jamia Millia Islarnia, Jamia Nagar, NewDelhi 110025

Receired 2g May 1983: raised and accepted 2 December 1983

Cr ' ", Fe2 + , Fe' + and UO~ t interact with potassiumoctacyanomolybdate(lV and Y)and potassium octacyanotungstate-(IV and V) to give compounds of the types KMeMCN)8·nH20,(Me')lM(CN)8' nH20, K2Me'M(CN)8' nH20 andKMe"M'(CN)8 .nH20 where Me = Fe(llI) and Cr(III); Me' = UO~":Me"=Fe(II): M=Mo(ly), W(Iy); and M'=Mo(y), W(V). Thecumpounds have been characterised on the basis of analytical.conductance and IR data.

This note describes the characterisation of some mixedmetal cyano compounds obtained by the interaction ofchromium(III), iron(lI), iron(III) and uranium(VI) withpotassium octacyanomolybdate(IV & V) and pot-assium octacyanotungstate (IV and V).

Potassium octacyano-molybdate(lV) and-tungstatet lV) were prepared according to theLeipoldt's method 1 and the corresponding pentava-lent salts were prepared by Goodenow's method",Solutions of chromic chloride, ferric chloride, ferroussulphate and uranyl nitrate were prepared bydissolving AR grade crystals of salts in doubly distilled

water. Their concentrations were determined bystandard analytical methods".

For conductivity measurements, Toshniwal'sDigital conductivity meter (S.N. 052, type CL 01/10)with a dip-type cell (cell constant =0.981) was used.Infrared spectra were recorded in KBr using a PerkinElmer (model No. 221) infrared spectrophotometer.

The compounds were obtained in the solid state bymixing the solutions of the reactants in thestoichiometric ratios at room temperature and keepingthe mixture for a few hours after stirring it. Theprecipitates obtained were washed with water, ethanoland then dried in vacuo over calcium chloride. All thesecompounds were insoluble in water. The complexeswere analysed for metal ions, after fusing them withNa202 and NaOH in a nickel crucible and extractingthe melt with water. Iron and chromium wereestimated spectrophotometrically using KSCN and1,5-diphenylcarbazide as complexing agents.Potassium (as tetraphenyl boron salt), uranium andmolybdenum (as their oxinates) and tungsten (as oxide)were determined by gravimetric methods": nitrogenwas estimated by the modified Kjeldahal method".

The stoichiometries of the reactions betweenpotassium octacyanomolybdate(IV) or potassiumoctacyanotungstate(IV) and metal salts in solutionwere determined by conductometric titration method.The reactions may be represented by the followingequations:

Table I-Analytical Data of the Complexes

Complex Colour Found (Calc.), ~;,

W/Mo Fe/U02/Cr K CN H2O

KCrMo(CNh·6H10 Reddish brown 19.11 11.06 7.51 41.85 21.03shining crystals (19.09) (10.34) (7.75) (41.27) (21.47)

KCrW(CNls·IOH2O Reddish brown 27.88 7.40 6.04 31.57 26.89shining crystals (27.75) (7.84) (5.88) (31.37) (27.14)

KFeIlMu'(C )8·8H20 Greenish blue 17.46 9.89 6.51 37.80 26.68powder (17.68) (10.31) (7.18) (38.31) (27.01)

KFeIlW"(CNh. 7H 20 Light green powder 35.76 11.13 8.63 40.58 20.40(36.44) (11.09) (7.72) (41.19) (20.55)

KFeMo(CN)8·7H20 Dark blue powder 18.77 10.66 6.73 39.07 24.21( 18.29) (10.67) (7.63) (39.62) (24.47)

KFeW(CN)~. 7H2O Bluish green powder 29.97 9.37 6.28 34.06 20.72(30.02) (9.14) (6.36) (34.59) (20.55)

(U02hW(CN) •. 8H2O Dark brown powder 17.24 49.44 19.16 13.50(17.10) (50.19) (19.33) (13.38)

K2U02Mo(CN)8' 8H 20 Brownish red powder 11.97 34.55 10.05 25.07 18.00( 12.06) (33.92) (9.80) (26.13) (18.08)

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MeCI3 + K4M(CN)s --+ KMeM(CN)g + 3KCI ... (1)

where Me =Cr(III), Fe(I1I) and M = Mo(IV), W(lV)

2U °z(NO 3) Z + K4 W(CN)!! --+( UO z) 2 W(CN)s+4KNO, ... (2)

Potassium octacyanomolybdate(V) and potassiumoctacyanotungstate(V) interact with ferrous sulphategiving green co loured precipitates of compositionKFeIlMV(CN)s .nHzO.

Potassium octacyanomolybdate(V) also reacts withuranyl nitrate giving a reddish brown complex ofcomposition K2UOzMo(CN)s .-nH20 as shown by itselemental analyses. All the complexes,KCrMo(CN)8' nH20, KCrW(CN)s. »n ,o.KFeMo(CN)M.nHzO, KFeW(CN)s.nHzO and(U02)zW(CN)8.nH20 were analysed for molyb-denum, tungsten, potassium, chromium, iron,uranium and nitrogen (Table I). Water was estimatedby heating the complex at II0cC for 2-3 hours.

Lippard et al. 5 observed a sharp distinct IR band inthe cyanide stretching frequency region (2050-2140em -I) for K4Mo(CN)s; the band was replaced by abroad envelope centered at 2140 em -I in the redbrown (U02hMo(CN)s adduct. This result isconsistent with Mo - C == N - U02 type of bonding.The IR spectra of the complexes now studied showpeaks in the range 3300-3500 em -I, characteristic ofO- H stretching frequency. Another sharp peak isobtained at 2000-2125 cm:", which is due to C == Nstretching. The lowering of the C == N stretchingfrequency in all these complexes suggests that charge-transfer occurs by the interaction of the cations, FeZ + ,

NOTES

Fe3 + , Cr3 + and UO~ + with CN -ligand. Donation ofthe electron from the cation to the antibonding n*orbitals of CN - would lower the stretching frequencyin the same way as back donation from the transitionmetal ion 1.2. Another peak is obtained at \600-\6\0em - 1 which is characteristic of H - 0 - H bending;peaks are also obtained in the region 400-600 em -I,which are characteristic of M - CN stretching and M- C - N bending frequencies. In addition, uranylcompounds show a sharp peak at - 940 em -I due to 0- U - 0 stretching frequency 1.6. 7.

The simplicity of these spectra indicates adodecahedron (Du) symmetry. Our results areconsistent with the results obtained by Parish et al.s,who interpreted the solid state IR spectra of some saltsof M(CNH- ions on the basis of the dodecahedralstructure of K4Mo(CN)s.2H209.

Financial assistance from the UGC, New Delhi forthe project is thankfully acknowledged.

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(1974) 343; 407 (1974) 250.2 Goodenow E L & Garner C S, J Am chem Soc, 77 (1965) 5268,

5272.3 Vogel A I, A text book of quantitative inorganic analysis

(Longmans, London) 1978, 738,472,486,487, 741.4 Jaselskis R & Lanse J G, Analytical chirn Acta, 23 (1960) 6.5 Allen M & Lippard S J, Inorg Chern, 9 (1970) 991.6 Harbenson-Evans D, Phipps P B P & William R J P, J chem Soc,

(1965) 6170.7 Bullock J I. J chem Soc (A), (1969) 781.8 Kettle S F A & Parish R Y, Spectrochirn Acta, 21 (1965) 1087.9 Hoard J K, Hamor T A & Glick M 0, J Arn chem Soc, 90 (1968)

3177.

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