Indian Journal of ChemistryVol. 29A, October 1990, pp. 982-985

Preparation and characterization of par~toluenesulphonato complexes ofarsenicrlll), antimonyilll) and bismuthilll)

Pratibba Kapoor", Foonam Wadbawan & Sunita TuliDepartment of Chemistry, Panjab University, Chandigarh 160014

Received 2 January 1990; revised and accepted 26 March 1990

Antimonylllf] oxide reacts with para-toluenesulphonic acid, ~CH3C6H4S03H(PTS), and its anhy-dride, (~H3C6H4S02hO, to yield SbO(~CH3C6H4S03) while bismuthflll) oxide combines withPTS and its anhydride to give BiO(~CH3C6H4S03) and Bi(p-CH3C6H.S03h, respectively. Arsen-ic(ill) oxide, however, shows no reactivity either towards PTS or its anhydride. Compounds of the.type M(~CH3C6H4S03h (M= As, Sb and Bi) have been prepared by the metathetical reaction be-tween silver para-toluenesulphonate and the appropriate metal chloride. Sodium arsenite and bis-muthate react with PTS to yield Na[AsO(~CH3C6H.S03hl and Na[Bi(~H3C6H4S03)41, respect-ively. The compounds have been characterized by elemental analysis, conductance and IR measure-ment. M(~CH3C6H4S03h (M =As, Sb, and Bi) compounds are capable of functioning both as lewisacids and bases. The para-toluenesulphonate ion in these compounds is easily replaced by Br " ion.

In an earlier paper), we have reported the prepar-ation, properties and characterization of methane-sulphonato complexes of As(III), Sb(III), andBi(III). The analogous M(S03Xh salts [M = Sb(m)and Bi(Ill) and X = F and CF3] have also been re-ported in the hterature/". This paper describesthe preparation and characterisation of MO(p-CH3C6H4S03) [M = Sb(Ill) and Bi(Ill)], M(p-CH3C6H4S03h [M = As(Ill), Sb(Ill), and Bi(III)],Na[AsO(p-CH3C6H4S03h] and Na[Bi(p-CH3C6H4S03)4]'

Materials and MethodsAll the reagents (As203, Sb203, Bi203, BiCI3,

NaAs02, NaBi03) were dried by heating them invacuo at 110°C. AsCI3 (Fluka AG) was used assuch. SbCI3 (E. Merck) was distilled in a currentof dry oxygen-free nitrogen. BiCl3 (Thomas andThomas) was sublimed in vacuo. Silver para-toluenesulphonate was prepared by the reactionof Ag20 (BDH, AnalaR) with an aqueous solutionof PTS. The solution was evaporated on a waterbath. The product was dried in vacuo at 100°Cfor several hours.

Para- toluenesulphonic acid (PT'S)p-CH3C6H4S03H.H20 (BDH) was purified by

removing water as toluene-water azeotrope". Theacid having the minimum specific conductivity of2.40 x 10-5 ohrn-) cm "! at 35°C was obtainedafter repeating the above distillation 3 to 4 times,each time pumping off the residual toluene. Addi-

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tion of acid anhydride, (p-CH3C6H4S02hO to thisacid caused no further decrease in the conductiv-ity even when the two were allowed to equilibratefor several hours. The pure acid is a dark, highlyviscous liquid and has density equal to 1.2605 gcm-3 and surface tension equal to 20.14 dynesem -e I at 35°C.

Paro-toluenesulphonic acid anhydrideIt was prepared by reacting equimolar amounts

of the acid and P4010 at ::::40°C for 3 to 4 h: andextracting the anhydride with diethylether? [Ob-served: S, 19.5; C, 51.42 and H, 4.32%. Required:S, 19.6; C, 51.53 and H, 4.29%]. The molecularion peak was observed at m/z 326. The molecularion [(p-CH3CoH4S02lz0]+ fragmented to give [(p-CH3C6H4)2S0J+ (mlz= 262) and a molecule ofS02' Formation of this fragment (M - S02)+ wassupported by the appropriate metastable ion m",at 210 indicating the loss of S02' If the reactionbetween PTS and P40lO was carried out at highertemperatures (above 60°C), the product obtainedafter extraction with diethylether wasnot (p-CH3C6H4S02lz0 but para-tolyl-para-toluenesulphonate, (p-CH3C6H4S020C6H4CH3)[Observed: S, 12.4; C, 64.33 and H, 5.30%. Re-quired: S, 12.2; C, 64.12 and H, 5.34%].

Trl.9...para-toluenesulphonates) of arsenic, anti-mony, and bismuth, M(p-CH3C6H4SOJ)3

These compounds were prepared by stirring theappropriate metal chloride with silver para-

KAPOOR et al: jrTOLUENESULPHONATO COMPLEXES OF As(I1I), Sb(III) & Bi(III)

Table 1-Analytical data of para-toluenesulphonato complexes of As(III), Sb(III) and Bi(IIl)Compound Found (Calc.), % .

M S C H

As(jrCH3C6H4S03M 1) 12.6 16.1 42.67 3.62(12.7) (16.3) (42.86) (3.57)

Sb(jrCH3C6H.S03 h(2) 18.9 15.0 39.60 3.28(19.2) (15.1) (39.70) (3.31)

Bi(jrCH3C6H4S03h( 3) 28.2 13.0 35.02 3.10(28.9) (13.3) (34.91) (2.91)

SbO(jrCH3C6H4S03X4) 39.4 10.3 27.15 2.36(39.4) (10.4) (27.21) (2.27)

BiO(jrCH3C6H4S03X5) 52.0 8.3 21.14 2.04(52.8) (8.1) (21.22) (1.77)

Na[AsO(jrCH3C6H4S03hX6) 16.1 14.1 36.90 3.21(16.4) (14.0) (36.85) (3.07)

Na[Bi(jrCH3C6H4S03)4 X 7) 22.4 13.8 36.51 3.17(22.8) (14.0) (36.69) (3.06)

toluenesulphonate (mole ratio 1:3) in CH3NOz orCH3CN. Silver chloride formed was removed andthe compounds recovered by distilling off the sol-vent in vacuo. Alternatively, the compounds couldalso be obtained by solvolysis of metal chloridesin pure PTS. The excess acid was washed withdiethylether. Bi(p-CH3C6H4S03h was also ob-tained by the reaction of Biz03 and (p-CH3C6H4SOZ)zO in CH3NOz at room tempera-ture.

Biz03 + 3(p-CH3C6H4SOzlz° ....•

2Bi(p-CH3C6H4S03h

Oxd paro-toluenesulphonatesi of antimony andbismuth, Ma..,p-CH3C6H4S03) (M= Sb or Bi)

These compounds were prepared by heatingthe appropriate metal oxide with PTS (large ex-cess) to about 100°C for 4 to 6 h. Reaction ofBi203 with PTS was completed at room tempera-ture in 2-3 h. Greyish-white solids were recoveredafter stirring the contents with diethylether.SbO(p-CH3C6H4S03) was also prepared by thereaction of Sb203 with (p-CH3C6H4S02}zO.

Sodium oxobis.para- toluenesulphonato )arsenate(III), Na,Asa..,p-CH3C6H4S03lz]

It was prepared by stirring sodium arsenite withPTS for 3 to 4 h and recovering the product withdiethylether.

Sodium tetrakis.para- toluenesulphonato )bismuth-ate (III), Nd,.B~p-CH3C6H4S03)4]

Sodium bismuthate was stirred with PTS for8-10 h and bismuth (III) compound, NafBi(p-CH3C6H4S03)4]' was obtained after treatmentwith diethylether. The compound did not liberate12 from acidified KI solution thereby suggestingthat bismuth was in a lower (+ 3) oxidation state.

Pyridine complexesIn a typical experiment, an excess of pyridine

was added to the suspension of Sb(p-CH3C6H4S03h (mole ratio 4:1) in light petroleumether at about - 10°C. The contents were stirredfor a few hours, vacuum filtered, washed withfresh light petroleum ether, and finally dried invacuo [Observed: S, 11.9; C, 46.80; H, 4.06 andN, 3.42%. Required for Sb(p-CH3C6H4S03h.2CsHsN: S, 12.1; C, 46.92; H, 3.91 and N,3.54%]. Complexes of pyridine with other PTSsalts were prepared and analysed in a similar way.

Boron tribromide complexesIn a typical experiment, As(p-CH3C6H4S03)3

(0.84 g, 1.32 mmol) was taken in CHCl3 (10 mI)and a solution of BBr3 (0.68 g, 2.71 mmol) inCHCI3 (15 mI) was added dropwise. An exother-mic reaction was observed and contents were al-lowed to stir for 3 to 4 h at room temperature.The pale-yellow solid was vacuum-filtered and

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INDIAN J CHEM, SEe A, OcroBER 1990

dried [Observed: C, 29.34 and H, 2.64%. Re-quired for As(p-CH3C6H4S03)3.BBr 3: C, 30.05and H, 2.50%J. Complexes with antimony andbismuth salts were prepared and analysed in a si-milar fashion.

Analytical methods adopted for elemental de-termination were the same as discussed earlier'.Infrared spectra were recorded on a Perkin-Elmer1430 ratio recording spectrophotometer as nujoland hexachlorobutadiene mulls between KBr andpolyethylene plates. Mass spectra were recordedon a VG micromass mm 70170. Density measure-ments were made on a PAAR DMA 602 dens i-tymeter. Conductances of solutions were mea-sured directly using a Toshniwal conductivitybridge (type CL 0l/02A).

Analytical results of the compounds preparedabove are summarized in Table 1.

Results and DiscussionArsenic(III), antimony(III) and bismuth(III) ox-

ides reacted with methanesulphonic acid anhy-dride, (CHJhS20S to yield M(S03CH3h type ofcompounds', but reaction of Sb203 and Bi203with para-toluenesulphonic acid anhydride yieldedSbO[p-CH)C6H4S03l and Bi(p-CH3C6H4S03))with As20) showing no reaction. This change inthe nature of the products may be attributed tothe increased basicity of the metal on movingfrom arsenic to bismuth. The difference in thereactivities of methanesulphonic acid and para-toluenesulphonic acid anhydrides towards theseoxides suggests lower acidity of the latter com-pound.

Tris(para-toluenesulphonates) of arsenic, anti-mony and bismuth could be prepared by the met-athetical reaction:

CHJ"'O,MCl1 + :ip-CH)C6H4SO)Ag

M(p-CH3C6H4S03h + 3AgCI

compounds (1) to (3) (see Table 1 for numbering)were off-white in colour. They were sensitive tomoisture and decomposed when exposed to moistair. They were soluble in polar organic solventssuch as CH)N02' C6HSN02' CHiCN and DMSO.Their millimolar solutions in CH3CN andC6HsNOz were non-conducting thus suggestingthat the (p-CH3C6H4SO; )group is covalentlybonded to metal atom. Behaviour of these com-pounds in terms of their ionization in para-toluenesulphonic acid either as acidic or basic so-lutes could not be ascertained owing to the highlyviscous nature of the acid and their limited solu-bility.

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Earlier, IR spectral studies on sulphonate li-gands have yielded useful information on ionicXSO; groups 7-9, covalently bonded monodentate- OS02X groups'P", and bidentate bridging andtridentate XS03 groups+'-". Band assignmentshave been made assuming that the C3v localsymmetry for CS03 moiety (ionic or tridentateXSO; group), which would be responsible for sixfundamentals, three E1vas (SO)), s, (S03) and ~r

(S03)] and three ~vs (S03)' v(S - C), and ~s(S03)] modes of IR-active vibrations, is loweredto C. (or Cl) on monodentate or bidentate type ofcoordination. With the lowering of symmetry thethree E modes are split to give six bands, and atotal of nine IR-active bands may be expected.

Inspection of Table 2 reveals that the IR spect-ra of these compounds are quite identical, indicat-ing strong structural similarity between them. Thedoubly degenerate SO) asymmetric stretching(v4) and S03 asymmetric bending (vs) modesshow splitting which suggest that the local symme-try of the CS03 moiety is reduced below C)v- Thepara-toluenesulphonate group may be acting as aunidentate ligand which would be consistent withmetal ions acquiring coordination number 3 incompounds (1) to (3). In this mode, one oxygenatom is different from the other two and it is in-volved in bonding to metal ions. In oxo com-plexes, there was no evidence of the existence ofdiscrete M = ° species owing to the absence of asharp intense band in the region 900-1000 em - 1.

Probably, oxygen acts as a bridging atom to givenpolymeric structures.

Pyridine formed 1:2 addition compounds withM(p-CH)C6H4S03)3 (M=As, Sb and Bi) and 1:1complexes with MO(p-CH3C6H4S03) (M = Sb andBi) thereby suggesting that the metal atom inthese compounds retained lewis acid character.Coordination of pyridine in these complexes didnot result in any significant change in the S - 0stretching modes. This observation is consistentwith the fact that PTS group acts as a unidentateligand in these compounds and M(p-CH3C6H4S03h. 2NCsHs and. MO(p-CH3C6H.:SOJ NCsHs may be assigned coordina-tion numbers 5 and 4. respectively. Bands due toC-C and C- N stretching modes, usually observedbetween 1450 and lA15 cm-I, have been ob-served with a slight upwards shift!". M(p-CH3C6H4S03h (M = As, Sb, and Bi) compoundsalso functioned as lewis bases by forming 1:1complexes with BBr 3' It was not possible to char-acterize these adducts by IR because of their ex-tremely reactive nature.

Reactions of M(p-CH3C6H4S03)3 with

KAPOOR et al: p-TOLUENESULPHONATO COMPLEXES OF As(III), Sb(lII) & Bi(III)

Table 2 - Pertinent infrared spectral bands (em - •)of some para-toluenesulpbonates

Assignment Compounds(C)v)

1 2 3 4 5 6 7 8t

v4(E){SO) as. str.] 1270m, 1270m 1260m, 1280m, 1240m, 1240m, 1275m, 1220s,

1040s,br 1045m,br 1040s,br 1040s,br 1040s,br 1190m,br 121Om,br 1190s,

1180s,

v.(AtXSO) sym. str.] 1030s,br 1020s,br 1030s,br 1025s,br 1020s,br 1120m,br 1130m,br 1125s

vz(AtXSC str.] 680m 670m 670m 660m 670m 705m 6905 680s

670s

VS(E)[S03 sym. defn.] 550s, 5405, 550m, 540m, 540m, 595m, 605m, 560m

500sb 510w 520w 500sb 500sb 560m 550m

v3(AtXS03 sym. defn.] 460m 440m 430m 450m 440m 470w 490w 495m

v6(E)[SR defn. & p-CH3C6H4 1380m, 1370m, 1370m, 1380m, 1370m, 138Ow, 1370m, 1380m,

internal vib.] 11205, 11105; 11205, 11205, 1110s, 1170sb, 1l05m, 8105,

8105, 805m, 810m, 800s, 815m, 450w 470w 700w,

700w, 704w, 700w, 700sh, 120m, 380w

400m 380m 410w 400w 360w

• Numbering according to Table 1tNa+(p-CH3C6H4SOi]

(CH3)4N+Br- yielded yellow compounds corre-sponding to composition (CH3)4N+ (MBri)(M =As, Sb and Bi) in which p-CH3C6H4S03"was replaced by more electronegative Be. Thehighly polarizable nature of para-toluenesulphon-ate ion can be used in preparing other derivativesof these elements. IR spectra of these compoundsdid not show any band which might be assignedto sulphur-oxygen stretching modes.

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