Monobromide", Cyanogen Bromide"

NOTE S

K. Jankowski, J. Kirchnerova, G. Perreault and to (lit." m.p. 125°); Ph2SnNp2, m.p. 208° (lit." m.p- J. Belanger for discussions. Grants from the Faculty 209-10°). of Graduate Studies and Research (McGill Iodine monobromide", cyanogen bromide" and Uiversity), CIL, and help from faculty members thiocyanogen" were prepared and purified by litera- McGill University are also acknowledged. ' ture methods. Anhydrous carbon tetrachloride was References used .as the solvent and moisture excluded during the reactions. 1. WERNER, A. E., J. chern. Soc., 101 (1912), 2180. One typical experiment is described below. Others 2. COADE, M. E. & WERNER, A. E., J. chern. Soc. (Transactions) 103 (1913), 1221. ' are given in Table 1. 3. RmD, J. H., Q. Rev., 15 (1961), 418. Reaction of Ph3SnNp with IBr (in I : I ratio) - A 4. H~I.CHINSON, K. & BOLTZ, D. F., Analyt. Chem., 30 (1958), solution of IBr (2.07 g, 0.01 mol) in CCl4 (30 ml) was 5. US Pat., 3 886 010 (27 May, 1975) to Ireco Chemicals slowly added to a stirred solution of triphenylnaph- Company. ( thyltin (4.77 g, 0.01 mol) in CCl4 (100 ml) at room 6. EDMONDS, A., KIRCHNEROVA, J., MATIS, T. C. & PAR~, temperature. The blood red colour of IBr solution J. R. J., CDN Pat. No. 1096172 (1981). 7. Foss, 0., JOHNSEN, J. & TVEDTEN, O. Acta chem scand. gradually disappeared after each addition. After the 12 (1958), 1782. ", addition was over the mixture was stirred and war- 8. PERROT, J. R., STEDMAN, G. & UYSAL, N., J. chern. Soc. med for 30 min. The solvent was removed completely (Dalton), (1976), 2058. and the residue distilled under reduced pressure to 9. COOLlNGS, P., Al-MALLAH, K. & STEDMAN, G., J. chem, 0 Soc. (Perkin II), (1975), 1734. give a-naphthyl iodide (1.7 g, 70 %), b.p. 160 /8mm 10. SAHASRABUDHEY, R. H., J. Indian chern. Soc., 27 (1950) (lit.! b.p. 305°/760 mm), further characterised by 515; 28 (1951), 119. ' CO-IR with an authentic sample. The residue was 11. OAn~E, S., FuKUSHIMA, D. & KIM, Y. H., Chern. Lett., (1978) , recrystallized from cold pet. ether (60-80°) and 12. PERRIN, D. D., Dissociation constants of organic bases in identified as triphenyltin bromide (3.4 g, 80 %), aqueous solutions (Butterworths, London), 1965. m.p. 120 (lit." m.p. 122°). Though it has been established- that the metal- aryl bond is preferentially cleaved over the metal- alkyl bond, however, when two different aryl groups Reactions of Tin-Naphthyl Bond with Halogens & are present as in this system, there is the possibility Pseudohalogens of one undergoing preferential cleavage over the other. In the case of triphenylnaphthyltin or diphenyl- S. N. BHATIACHARYA* & ISHRAT HUSAIN dinaphthyltin, the naphthyl group is found to be Department of Chemistry, University of Lucknow, more reactive and hence it is cleaved before identically Lucknow 226 007 placed tin-phenyl bonds. This is due to the fact that in naphthyl group the ec-carbon atom attached to Received 6 January 1981; revised and accepted 23 February 1981 metal has greater electron density due to greater Reactivity of Sn-phenyl or Sn-naphthyl bond in tetraorga- magnitude of self-polarisability and hence more readily attacked by electrophiles than the phenyl notins, Ph SnNP4_n (Ph = phenyl, Np = ex-naphthyl; n = 2,3) n group in which the self-polarisability at all positions towards halogens (Br2 and 1 ), interhalogens (mr and ICI), 2 is equal", interpseudohalogens (BrCN and leN) and pseudohalogen (SCN)2 Both Br2 and ICI are strong electrophilesv" and has been studied. It is found that the Sn-Np bond is preferen- invariably cleave two organic groups from tially cleaved yielding in most cases phenyltin derivatives along Ph SnNp4_n at lower temperature (-5°) irrespective with the corresponding ex-naphthyl halides. n of the ratio of the electrophile used to give diphenyl- tin dihalide, Ph2SnX2 (X = Cl, Br) along with the REACTIONS of symmetrical (R4M) and unsy- corresponding amount of cx.-naphthyl- and phenyl- mmetrical (RnMR' 4-n) tetraorgano derivatives halides. In the case of Ph2SnNp2 both the naphthyl of Group IV metals (M = Si, Ge, Sn and Pb) with groups are preferentially cleaved (Eq. 1). various electrophilic reagents have been reviewed'. We now report some reactions of tetraorganotin Ph2SnNp2 + 2ICl -+ Ph2SnCl2 + 2NpI .. (1) derivatives, PhnSnNp4_n (n = 2 or 3 and Np = ec-naphthyl) with halogens and psuedohalogens. The Attempts to prepare the monohalide, PhnNp3-n main object of this work was (i) to study the extent snX (X = Cl, Br; n = 2 or 3) by slow addition of and relative ease of the cleavage of Sn-Np or Sn-Ph one mol of Br2 or ICI at _5° have not been success- bond, (ii) to characterise the organotin reaction pro- ful and unreacted Ph"SnNp4-n (n = 2 or 3) (50%) ducts and the corresponding aryl halides, RX (R = is recovered in each case. phenyl or ex-naphthyl; X = Br, I, SCN) and (iii) to Reactions with IBr and 12 are less facile. Thus compare the reactivities of strong (ICl, Br2), medium 1 : 1 molar reactions of IBr and 12 with Ph3SnNp [12, IBr, (SCN)2] and weak (lCN, BrCN) electrophiles afford Ph3SnBr and Ph3SnI respectively at room towards the system in the absence of a Lewis acid temperature (Eq. 2). IBr and 12 cleave one more catalyst. phenyl group from Ph3SnX on further refluxing for Triphenylnaphthyl- and diphenyldinaphthyl-tins 30 min in CCI4• Diphenyldinaphthyltin furnishes were prepared by reacting cx.-naphthylmagnesium bro- diphenylnaphthyltin iodide with one mol of 12 and mide and phenyltin chloride initially in ether follo- with two mol of IBr or 12 it affords diphenyltin- wed by refluxing in toluene: Ph3SnNp, m.p. 125° dihalide at refluxing temperature of CCl4 (Eq. 3).

1119 INDIAN J. CHEM., VOL. 20A, NOVEMBER 1981

TABLE 1 - REACTIONSOF Ph., SnNp4_" (Ph = phenyl, Np = «-naphthyl; n = 2 or 3) WITH X2, IX, XCN AND (SCN). (X = Cl, Br, I)

Electrophile (XY) Molar ratio Reaction time (hr), Productsts) Yield m.p.tlits.m.p.) ------XY/PhnSnNp4_n and temp. (0C) (%) (0C) X Y

REACTIONSWITH Ph3SnNp

Br Br 2:1 1, (-5) Ph2SnBr.(b) 75 35 (38) I I 1:1 I, (25) Ph3SnI 80 121 (121) I I 2:1 1, (70) Ph.SnI2(b) 76 71 (72) I C) 1:1 !, (0 to -5) Ph2SnCI2(c) 78 42 (44) I Cl 2:1 t, (0 to -5) Ph.3nCl.(b) 80 41-42 (44) I Br 2:1 1, (10) Ph2SnBr.(b) 72 36 (38) I CN 1:1 2, (70) Ph3SnCN 80 255 (256) Br CN 1:1 2, (70) Ph3SnCN 80 254 (256) SCN SCN 1:1 1, (0) Ph3SnNCS 58 173 (174-75)

REACTIONSWITH Ph2SnNp2 Br Br 1:1 I, (-5) Ph.SnBr.(c) 68 37 (38) Br Br 2:1 1,(-5) Ph2SnBr2 75 36 (38) I I 1:1 !, (25) Ph2NpSnI

(a) Corresponding amounts of NpX (X = Br, I, NCS) were also obtained, the b.p. of which agree well with those reported in literature'. (b)NpX (X=Br, I) also contained some phenyl halides which were not individually separated. (clUnreacted PhnSnNp4-n (n = 2 or 3) was also isolated. (d)Found : C, 50.06; H, 3.12; Sn, 22.41. C.2H'7SnI requires C, 50.14; H, 3.21; Sn, 22.52 %

Ph3SnNp + IBr --+ Ph3SnBr + NpI .. (2) of AICl3 (ref. 6,8). CICN is ineffective towards Si-C bond even in the presence of AICl (ref. 8). Ph SnNp2 212 --+ Ph SnI 2NpI .. (3) 3 2 + 2 2 + However, in the present investigation it is observed The mechanism of such reactions possibly involves that tin-naphthylbond in Ph3SnNp is prone to attack a four-centered transition state (A) in which nucleo- by cyanogen bromide or iodide producing triphenyl- philic attack on metal atom by incipient halide ion is tin cyanides in the absence of any Lewis acid catalyst. synchronous with electrophilic attack by iodonium When excess of cyanogen halide is employed, no ion on carbon. cleavage of phenyl group is observed due to electron withdrawing nature of CN group introduced in

Ph3SnCN which will have a strong deactivating effect on the remaining Sn-phenyl bonds and will ©Jf) discourage substitution by further cyanogen halide +, ,+ molecule". Ph3Sn<" ,,>1 '.•/... The cleavage of metal-carbon bond by (SCN)2 )( is consistent with its pseudohalogen character but it (X=Cl,Br) seems less reactive than even the interhalogens and ( A) more reactive than inter-pseudohalogens=". Thus,

with Ph3SnNp, tin-naphthyl bond is cleaved by Similar mechanism has earlier been suggested for freshly prepared (SCN)z (1 : 1 ratio or excess) at ice- the cleavage of M-C, M-P and M-As (M = Si, Sn, bath temperature. Further warming or prolong stirr- Pb) bonds by halogens>" amd interhalogens=". ing with excess of (SCN)2 favours polymerization of The fission of second Sn-C bond in these reactions the electrophile precluding the cleavage of phenyl is less facile due to reduced nucleophilic character of group. The formation ofPh3SnNCS may be explained Sn-C bond in triorganotin derivatives (because of on the lines proposed by Bullpit and Kitching". the presence of an electronegative group attached to Financial assistance from State Council of Science tin) as compared to tetraorganotin compounds, and Technology, Lucknow is gratefully acknow- coupled with the less polar nature of IBr and 12 ledged. which behave as weak electrophiles. Reactions of inter-pseudohalogens, XCN (X = References Br, I) with Ph"SnNp4_" lend further support to the 1. EABORN,C, J. organometal. Chern.• 100 (1975), 43. greater reactivity of tin-naphthyl bond. It has been 2. INGHAM,R. K., ROSENBURG,S. D. & GILMAN, H., Chern. reported that cyanogen halides, XCN (X = CI, Rev., 60 (1960), 459. Br, I) are very weak electrophiles and do not cleave 3. BHATTACHARYA,S. N., PREM RAJ & MEENU SINGH, Indian M-arylbond (M = Si, Ge, Sn and Pb) in the absence J. Chern.• 17A (1979), 355.

1120 NOTES

4. LANGE, N. A., Handbook of chemistry (McGraw-Hili, sulphur dioxide giving coloured solutions from which New York), (1967), 608. crystalline compounds of the type PhaM(S02)2 have 5. FINAR, I. L., Organic chemistry (Longmans, London), been isolated. The reaction is non-reversible and the Vol. 1 (1969), 760. 6. BHATTACHARYAS,. N. & PREMRAJ, Indian J. Chem., 15 A compounds decompose on heating to give diphenyl (1917),799. sulphone. Ph3Sb(SOa)2 reacts with HCI giving 7. ABEL,E. W. & ILLINGWORTH,S. M., J. chem. Soc., (1969), Ph3SbCl2 indicating lack of insertion into the meta- 1074. lloidal bond", The insertion of sulphur dioxide into 8. BARTLEn', E. H., EABORN, C. & WALTON, D. R. M., J. organometal Chem., 46 (1972), 267. organoantimony chelates has not attracted any 9. BULLPIT, M. L. & KITCHING,W., J. organometal. Chem., attention. We report herein the behaviour of several 34 (1972), 321. triphenylantimony(V) bis-chelates towards liquid sulphur dioxide at - 20°C. Chelated triphenylantimony(V) compounds were prepared from triphenylantimony dibromide and Sulphur Dioxide Insertion Reactions in Triphenyl- sodio derivative of a bidentate chelating ligand in antimony(V) Bls-chelates+ benzene by methods similar to those reported earlier". The sulphur dioxide insertion reactions were carried A. Y. SONSALEA, . K. CHATTERJEE(Mrs), SARADAGOPINATHAN out under absolutely dry conditions. A long necked & C. GOPINATHAN* flask with a gas inlet and outlet was flame dried and National Chemical Laboratory, Poona 411 008 cooled in a stream of dried sulphur dioxide gas to room temperature. The triphenylantimony chelate Received 1 January 1981; revised and accepted 16 February 1981 ( ,.... 19) was introduced into the flask and cooled in ice-salt mixture while passing a slow stream of sul- Bis-chelated triphenylantimony(V) compounds take up one phur dioxide gas. A sulphuric acid trap was used to molecule of sulphur dioxide in a medium of liquid sulphur dioxide prevent moisture entering into the system. When to form mono-insertion products, Ph.SO.SbL. where L = sali- about 10 ml of liquid sulphur dioxide had collected cylaldehyde, r;-diketones, 2-hydroxybenzophenones, benzoyl- over the sample in the flask, the rate of release of phenyl hydroxylamine, 8-hydroxyquinoline, dehydroacetic acid the gas was reduced to a few bubbles per minute. The etc. Infrared .spectral studies show that the products are 0- contents were allowed to mix by shaking and kept suiphinates, the insertion taking place between antimony and for 2 hr in the refrigerant. The liquid sulphur dioxide one of the phenyl groups. was then allowed to evaporate and the solid dried at room temperature in vacuo (0.5 mm). Samples KITCHING and coworkers=" and Wojcicki a were drawn for analysis within 2 hr of isolation. studied different aspects of the insertion of The sulphur dioxide inserted in the molecule of sulphur dioxide into both transition and non-transi- triphenylantimony(V) chelate appears to be held tion metal-carbon bonds. According to Kitching', tenaciously at room temperature because it is not the insertion of one molecule of sulphur dioxide into given out under reduced pressure. However, on a metal-carbon a-bond is a general reaction taking treatment with dilute HCI, sulphur dioxide is evolved. place by an electrophilic attack. The inference The sulphur dioxide content in the sample has been tha t these insertion products have O-sulphinate struc- estimated by iodimetry. These compounds are found ture (RSOaMR') has been drawn from the formation to contain one molecule of sulphur dioxide per mole- of identical products in the reaction between orga- cule of chelate. Heating destroys the insertion nometallic chlorides and sodium organic sulphinate. compound giving products of indefinite composition. The insertion of sulphur dioxide into metalloid- The insertion products of triphenylantimony chelates carbon bonds of the Group VB seems lacking. are less stable than similar mercury, tin and lead PhaM (M = N,P,As,Sb or Bi) dissolves in liquid compounds.

TABLE 1 - SULPHURDIOXIDEINSERTIONPRODUCTSOFBIS-CHELATEDTRIPHENYLANTIMO;-

No. Ligand, LH Ph.SO.SbL., colour SO.(%) SO. group frequencies and m.p. (0C) Found Calc. vas (S-O) v. (S-O)

1. Salicylaldehyde Yellow, >150 (d) 9.49 9.71 1000 880, 960 2. 8-Hydroxyquinoline Yellow, >250 (d) 8.96 9.07 1020-1100 880 3. Methyl salicylate White, 270 (d) 9.05 8.90 1120 990 4. Benzoy lace tone White, >155 (d) 8.31 8.70 990 840 5. Dibenzoylmethane Yellow, > 160 (d) 8.01 8.38 990, 1140 840 6. Acetoacetanilide Pink, 173 7.86 8.32 1030, 1130 860, 900 7. Acetylacetone White, >200 (d) 10.25 10.40 1170 980 8. Dehydroacetic acid White, 155 8.21 8.52 1125 860, 920 9. 2-Hydroxybenzophenone Yellow, 135 9.24 9.00 1150 990 10. 2-Hydroxyacetophenone Buff, > 175 (d) 9.05 9.31 1020 880 11. Ethylacetoacetate White, >250 (d) 9.63 9.48 1100 975 12. Benzoylphenylhydroxylamine Buff, 102 7.31 7.89 1130 920

tNCL Communication No. 2723

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