rirated sulphuric acid at 350, 343 and 371nm where X= H, N02 and OCH3 respec-

+ +tively; (ii) C6HsNH=NC6H4NH(CH3h(-P)9absorbs

+at wavelength lower than that of C6HSNH=NC6H4N(CH3)2(-P) and (iii) the Schiff base and itsmono-acid salt have similar spectrum in concen-trated sulphuric acid, which is probably owing to-cornplete protonation of all the basic centres. (I)and (II) absorb at 342 and 340 nm respectivelywhen X=N02; and both of them absorb at372 nm when X=OCH3 and at 350 nm whenX=H.

In the absence of (CH3)2Ngroup, the Schiff base-doesnot absorb in the region 440-470 nm in glacialacetic acid or in dilute sulphuric acid. In the lattermedium the Schiff base undergoes fast hydrolysisto the corresponding aldehyde and amine13.14. Thepresence of (CH3)2N group in the para positionin the ph, ring stabilizes the mono-protonat edspecies by the resonance structures (III) and (IV).

On the other hand benzylidene-p'-N,N-dimethyl-aminoanilines give a deep-red colouration in dilutemineral acids, these solutions absorb in the region470-500 nm and the colour tends to disappear veryrapidly6.13 (disappearance half-life times are inthe millisecond range6). The existence of the mono-protonated species in these compounds has beeninterpreted in terms of a tautomeric mixturecontaining approximately 70-85% of the ammoniumform. Mono-methylated salts of benzylidene-p'-N,N-dimethylaminoanilines through the azomethinenitrogen have been prepared by the reaction of theseSchiff bases with methyl iodide in benzene solu-tion (Saeed, A. A. H. & Matti, G. Y., unpublisheddata).

The author wishes to acknowlegde helpful com-ments from Dr K. A. K. Ebraheem during therevision of the manuscript.

References

1. BROCKLEHURST, P., Tetrahedron, 18 (1962), 299.2. ASHRAF EL-BAYOUMI, M., EL-AsSER, M. & ABDUL-

HALlM, F., J. Am. chem: ss«, 93 (3) (1971), 586;93 (3) (1971), 590.

3. JAFFE', H. H. l!" ORCHlN, M., Theory ~nd appli-cations of ultraviolet spectroscopy (John Wiley) , 1962,284.

.4. ISMAISKI, V. A. & SMIRNOV, E. A., J. gen. Chem., U.S.S.R.,26 (1956), 3389.

5. MANGINI, A. & PASSERINI, R., Experientia, 12 (1956),49; BRODE, N., Chemical spectroscopy (John Wiley,New York), 1945, 218.

<6. REEVES, R. L. & SMITH, "V. F., J. Am. chem, Soc., 85(6) (1963), 724.

7. SMETS, G. & DELVAUX, A., Bull. Soc. cu«. Belg., 56(1947), 106.

·S. RICKETTS, J. A. & CHO, C. S., J. org, Chem., 26 (1961),2125.

'9. ROGERS, MAX T., CA.MPBELL, TOD W. & MAATMAN,R. W. J. Am. chem, Soc., 73 (11) (1951), 5122.

10. REEVES: R. L., J. Am. chem, Soc., 84 (1962),3332.

11. HANTZSCH, A., Bel'. dt. chem, Ces., 41 (1908), 1171;52 (1919), 509; 63 (1930), 1760.

12. WEINSTEIN, J. & McINNICH, E. M., J. Am. chen«. Soc.,82 (1960), 6064.as. WILLI, A. V. & ROBERTSON, R. E., Can. J. Chem., 31(1953), 361.

14. ARCHILA, J., BULL, H., LAGENAUR, C. & CORDES,E. H., J. org, Chem., 36 (10) (1971), 1345.

(

NOTES,

Fluoroaluminates ofSome Organic Base Cations

A. K. SENGUPTA * & (Miss) K. SEN

Department of Chemistry, Kalyani University, KalyaniWest Bengal

Received 10 July 1978

Ffuoroalumlnates of various organic base cationshaving the compositions [EnH2][AlF.]O·5H.O,[BenzH][AlF5]' [PyH.][AIF.], [QnH][AlF.], [HONH2H]-[AlF.], [a,a' -BipyH.][AIF.]2H.O, [MorphH][AlF.],f2-AmpyHJ[AIF.]O·5H20, [GuHMAIFsJ, [BigH2]-

[AIF5] and [(CH3).NMAIFs] (where En = ethylene-diamine, Benz = benzidine, Py = pyridine, Qn = quino-line, a,a'-Bipy = a,a'-bipyridyl, Morph = morpho-line, 2-Ampy = 2-aminopyridine, Gu = guanidine,Big = biguanide) have been prepared. The guant-dinium and biguanidinium compounds decomposearound 130-140° while the others decompose around40°. All the compounds show sharp IR bands inthe region 450-675 cm-I, due to AI-F stretching fre-quencies.

THOUGH many papers have been published on thefluoro compounds of aluminiumve, literature

survey shows that except the hydrazinium penta-fluoroaluminate no other fluoroaluminate contain-ing organic base cation is known". The presentwork deals with the isolation and study of a num-ber of fluoroaluminates of various organic basecations.

Preparation of jluoroaluminates : Pentafluoro andhexajluoroaluminates - [EnH2] [AlFs]·0·5H20was ob-tained as a crystalline precipitate on adding cal-culated amount (2·7 X 10-2 mole) of ethylenedi-amine (En) acidified with dilute hydrofluoric acid(HF), to a solution of aluminium hydroxide (2·7 X10-2 mole) in 40% HF. After filtration the com-pound was washed with cold water and dried in air.[BenzH2] [AlFs] was obtained through the aboveprocedure by mixing the two components in the hotcondition.

Guanidinium hexafluoroaluminate and the penta-fluoroaluminates of biguanidium and tetramethyl-amine were prepared by evaporating on a water-bath, a mixture of Al(OH)3 dissolved in HF andguanidine, biguanide sulphate or tetramethylam-monium hydroxide respectively acidified with diluteHF. The crystalline compounds obtained werefiltered, washed with cold water and dried in vacuoover P20S'

Tetrajluoroaluminates, BHAlF4 (where B =hydroxylamine, pyridine, quinoline, morpholine,2-aminopyridine and a.,a.'-bipyridyl) - The hydro-xylamine compound was prepared as above fromhydroxylamine hydrochloride and Al(OH)3 acidi-fied with HF. The other compounds were obtainedby evaporating a mixture of Al(OH)3 dissolved in40% HF and corresponding organic base (acidifiedwith HF) on a water-bath to a syrupy mass andthen treating the mixture with minimum amountof acetone. The highly hygroscopic crystals ob-tained were filtered and recrystallized by dissolving

107

INDIAN J. CHEM., VOL. 17A, JANUARY 1979

TABLE 1 - ANALYTICALAND IR DATA OF F'LUOROALUMINATES

Compounds= Found (Calc.), % vAI-F(cm-1)

N Al F

[EnHJ [AIF ~].O·5HzO 14'51 14-17 49'76 535 (m), 620 (5, b)(14'51) (13'99) (49·21)

[BenzH.][AIF~] 9-04 8·8 31'25 450 (5), 510 (s), 540 (s);(9'08) (8,75) (30'82) 610-650 (5, b)

[PyH] [AIF,] 7·54 14'82 42'82 610 (w), 675 (s)(7-64) (14,74) (41'51)

[QnH] [AIF,] 5'9 11'53 32'68 470 (s), 610 (5)(6'00) (11'58) (32-58)

[HONH.H][AIF,] 10'33 19'32 55'89 595 (s)(10'22) (19'71) (55'48)

[1X,IX'-BipYHJ[AIF,]z·HzO 7'59 13'52 38'16 595 (m), 615 (m)(7·30) (14'02) (39-46)

[MorphH] [AIF.] 7'58 13'90 39'18 410 (m), 435 (m), 600 (Sf(7-32) (14-14) (39'70)

[2-AmpyH][AIF.].0·5HzO 13'62 12-87 36'42 595 (m)(13-52) (13-04) (36'69)

[GUH]3[AIFsJ 40'24 8·25 36·35 515 (w), 600 (s)(39'22) (8-40) (35-48)

[BigH s][AIF.J 31'20 11·99 40'82 560 (w), 575 (s), 600 (m}(31-11) (12-00) (42-22)

[(CHs),N]z[AIF,,] 10'44 10'28 36-08 620-640 (s, b)(10'37) (10'00) (35·18)

*En = ethylenediamine, Benz = benzidine, Py = pyridine, ~Qn = quinoline, IX,IX'-Bipy= CI(,CI('-bipyridyl, Morph.= morpholine, 2-Ampy = 2-aminopyridine, Gu = guanidine, Big = biguanide.

in minimum amount of water and then addingminimum amount of acetone.. The hygroscopicmatter thus obtained was filtered, washed withacetone-water (3:1) mixture and dried over P20S'

The tetrafluoroaluminates of organic base cationsare highly hygroscopic solids. The guanidiniumhexafluoroaluminate and the pentafluoroalumi-nates of protonated ethylenediamine, benzidine andbiguanide are sparingly soluble in water. Thecompounds are insoluble in ethanol, acetone, chloro-form, acetonitrile, nitrobenzene, etc.

Analysis- The compound (0·1 g) was fusedwith a mixture of silica (0-3 g), potassium carbonate(0·5 g) and sodium carbonate (0.5 g). The fusedmass was extracted with water. From the extractlead . chlorofluoride was precipitated and thefluorine content determined argentometrically. Theother constituents were estimated using standardmethods,

The analytical results are reported in Table 1.The fluoroaluminates were studied thermogravi-

metrically using a manually operated thermobalanceat a heating rate of 2°lmin. Most of the compoundsdecompose around 40° except the guanidiniumand biguanidinium compounds which decompose

108

(

around 130-140°. Maximum decomposition of the'compounds takes place in the regions 150-300°,and 450-500°. A mixture of aluminium fluorideand oxide is produced on decomposition.

The IR spectra of compounds show sharp bandsin the region 450-675 crrr- due to AI-F stretchingIrequencies-. The sharp and medium bands in theregion 1600-1675 cnr- may be due to N-H and.H-OH deformation modes. N-H and O-Hstretching frequencies may be responsible for thebands in the region 2500-3500 crrr". The bands.due to AI-F stretching frequencies for the differentcompounds are reported in Table 1.

The authors are thankful to the CSIR, New Delhi,for the award of a Junior Research Fellowship to-one of them (K.S.).

References

1. MELLOR, J. W., A comprehensive treatise on inorganicand theoretical chemistry, Vol. V (Long mans, London).1960, 303.

2. SIMONS, J. H., Fluorine chemistry, Vol. V (Academic'Press, New York), 1964, 26.

3. PUGH, W., J. chem, Soc., (1953), 2493.4. BULGAKOV,O. V., UVAROV, A. V. & ANTIPINA, T. V••

Zh. fie. s u«; 43 (4) (1969), 859.