Ahuja, I. S.

Singh, Raghuvir

English

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INDIAN J. CHEM., VOL. 15A, NOVEMBER 1977strength increases the rate constant indicatingthat the reaction is between ions of the same chargetype.The reaction is followed at two temperatures,viz. 30° and 46·5°. The energy of activation forthe substitution process is found to be 27·0 kcaljmole.The absorption spectrum of the product in thesestudies is identical with that obtained in the substi-tution studies of tris(malonato) chromate(III)complex by H3P04, with two peaks at 440 (€ =19·0) and 630 nm (€ = 19·0). Ion exchange studieson the product species failed to show the presenceof either cationic or anionic phosphate complexes.Hence the product species may be neutral possiblyof the type Cr(HP04)(H2P04).The following mechanism is suggested to explainthe experimental observations.Acid dependent path:K,Cr(mal)(H20)+ +H30-f ~ Cr(maIH)(H20WK.Cr(malH) (H20n++H20 ~ Cr(H20):-f+Hmal-slowCr(H20)~-f+H3P04 ---+Cr(HZP04) (H20)~++H+k,fastCr(H2P04) (H20)~++H3P04--+productsAcid independent path:slowCr(mal) (H20): +H3P04--+Cr(maIH) (HZP04) (H20)~k,fastCr(maIH) (H2P04) (H20)! +H3P04----+productsThis leads to the rate lawRate = ~lKIKz [complex][H3P04J[H30+][Hmal-]+k2 [complex] [H 3PO 4]{[k1K1K2[H30+] }= - [Hma~ +ll2 [complex] [H3P04]In the substitution of tris(malonato)chromate(III)by H3P04, the first step is observed to be the attackof H30+ on Cr(mal)~- to give a monodentate malonatocomplex, Cr(maIH)(mal)2(H20)2-. This monodentatocomplex enters into reaction with H3P04 to givethe products.Cr(malg-+H30+ ~ Cr(malH)(mal)z(HzO)2-Cr(malH) (mal)2(H20)2- + H++- H2PO;; ~Cr(mal)2(H2P04) (H 20)2-I1 H3P04ProductsIn the present case the monodentate malonatecomplex in the equilibrium step yields hexaaquo-chromium(III) which is attacked by H3P04• Thismay be the cause for the relative slowness ofsubstitution of the monocornplcx.Dr P. V. Subba Rao of this department ISthanked for useful discussions.1022References1. RAo, V. M., ANANTA RAlIfAM, V. & SASTRI, M. N., CurroSci., 45 (1976), 451.2. ANIPINDI, N. R., RAO, V. M. & ANANTA RAMAlIf, V.,I Indian chem. Soc., (communicated).3. ANIPINDI, N. R., RAO, V. M. & ANANTA RAlIfAM, V.,I Indian chem. Soc., (communicated).4. OLSON, M. V. & BEHNKE, c. E., Tnorg, Chem., 13 (1974),1329.5. JAMESON, R. F. & SALMON, J. E., I chem. Soc., (1955),360.2-Methylbenzothiazole Complexes of Hg(I1)Halides & PseudohalidesI. s. AHUJ A & RAGHUVIR SINGHChemistry Department, Banaras Hindu UniversityVaranasi 221005Received 18 March 1977; accepted 10 May 1977Hg(lI) chloride, bromide, cyanide and thiocyanateform I: 1 complexes with l-methylbenzothiazole.The complexes have been characterized by molarconductance, IR and far-IR spectral data. The Hg(II)chloride, bromide and thiocyanate complexes aretentatively suggested to have halogen/pseudohalogen-bridged dirner'lc tetrahedral structures in the solidstate. The Hg(lI) cyanide complex possesses acyano-br+dged polymeric structure.THE ligand, 2-methylbenzothiazole having twobonding sites - sulphur and nitrogen in thethiazole ring - possesses strong anti-bacterial, anti-tubercular and anti-viral activities. Metal com-plexes of biologically important Iigands are some-times more effective than the free ligands. Althoughcomplexes of 2-methylbenzothiazole with somemetal(II) salts are known! its complexes with Hg(II)salts which are likely to have significant biologicaleffects have not been reported. In this note wereport the preparation and characterization of thesolid complexes of 2-methylbenzothiazole (L) withHg(II) halides and pseudohalides.Hg(II) chloride, bromide and cyanide complexeswith 2-methylbenzothiazole Were obtained by add-ing an eXCeSSof the ligand to a hot solution of therespective Hg(II) salt in ethanol. Hg(II) thiocya-nate complex was prepared by boiling a suspen-sion of the metal thiocyanate with an excess of theligand, in ethanol. The solution was filtered hotand the complex which crystallized out on coolingwas suction-filtered, washed with ethanol and dried.Stoichiometry of the complexes isolated was estab-lished by standard analytical methods. Hg(L)CI2, m.p. 2200 (Found: Hg, 48·0; CI, 17·0. Calc.: Hg,47·6; CI, 16·9%); Hg(L)Br2' m.p. 202° (Found:Hg, 39·1; Br, 31·5. Calc.: Hg, 39·3; Br, 31·4%);Hg(L)(CN)2' m.p. 1450 (Found: Hg, 50·0. Calc.: Hg,49·9%); and Hg(L)(SCN)2' m.p. 113° (Found: Hg,43·1; SCN, 25·1. Calc.: Hg, 43·0; SCN, 24·9%).The 1:1 complexes are quite stable and solublein methanol and dirnethylformamide. Molar con-ductance of ,.....10-3M solutions in purified dimethyl-forrnamide (Philips conductivity bridge) indicateNOTESthem to be essentiallynon-electrolytic(AM ",30ohm-I cm2 mole-I). IR spectra (band positionsin em-I) of thesecomplexesaresimilarto thoseof2-methylbenzothiazolecomplexeswith other metalsaltsI, confirmingcoordinationthroughthe nitro-gen atom onlyi. In addition to the absorptionbands due to coordinated2-methylbenzothiazolethe far IR spectra(BeckmanIR-12) of the 1:1Hg(II) chlorideand bromidecomplexeswith thisligand show bandsat 267 in the chloro and at207 in the bromo derivative. The frequenciesofthesebandsare halogen-dependentand are identi-fied as vHg-Cl and Hg-Br modes,respectively,consistentwith terminal Hg-X stretchingmodesin HgLX2 complexesa,whereL=PhaP, pyridine,pyridine-N-oxideor their ring substitutedmethylor dimethylderivatives,which are consirleredtohavehalogen-bridgedimerictetraherlralstructuresin the solid state. Moreover,the Hg(II) chloridecomplexshowsan additionalbandat 202(butnotthe bromocomplex)dueto vHg-Clinvolvingbridg-inghalogens3•ThebridgingHg-Br stretchingmodeexpectedat ",150 couldnot be recordedwith thepresentrangeof the spectrophotometer.The ob-servedfrequenciesof the terminal and bridgingHg-halogenstretchingmodesin the 1:1 Hg(II)chloride and bromidecomplexeswith 2-methyl-benzothiazolelend supportto the halogen-bridgeddimerictetrahedralstructure(I) for the complexesin the solid state.x X L,/, /Hg Hg/ V ,L X XIX=CI, Br or SCNIR spectrumof the 1:1Hg(II) cyanide-2-methyl-benzothiazolecomplexshowsadditionalabsorptionbandsat 2200,455and 360which are identifiedas vCN, vHg-Cand a Hg-C-N modes,respectivelv,dueto coordinatedcyanogroups. Hg(II) cyaniclehasa linearcyanide-bridgedpolymericchainstruc-ture4 iu the solid stateand absorbs5at 2193,442and341dueto vCN,vHg-Cand a Hg C"N modes,respectively.The frequencyof vCN suffersa signi-ficantnegativeshift whenthe cyanobridgesbreakdownand Hg(II) cyanidecomplexeswith terminalcyanogroupsabsorbat lower energies6than puremercurycyanidewhile bridgingcyanogroupsab-sorb at higherenergies7.Complexeshavingbothterminaland bridgingcyano groupsdisplaysplitbands in eachof the vCN,vHg-Cand a Hg CNregions7;the oneappearingat higherwavenumberbeingassignedto the bridgingcyanogroupswhilethe other at lower wavenumberto the terminalcyano groups. The observedfrequenciesof vCN(2200),vHg-C(455)andaHg CN (360)areconsistentwith the presenceof only bridgingcyanogroups.The 1:1Hg(II) cyanide-2-methylbenzothiazolec m-plexmaythusbeassigneda cyanobridgedpolymericstructurein the solid state.In additionto the ligandbandsIR spectrumofthe 1:1 Hg(II) thiocyanate-2-methylbenzothiazolecomplexshows absorptionbands at 2133,2125and 2090due to vCN and two bands (770,690)in the vCSregionsupportingthe presenceof bothbridgingand terminalthiocyanatogroups8in thecomplex. On the basis of the stoichiometryandthe IR spectraldata the 1:1 Hg(II) thiocyanatecomplexwith 2-methylbenzothiazoleis tentativelyassigneda thiocyanato-bridgeddimericstructureinthe solid state with two --SCN- bridgesand atermiI)alSCN group bondedthrough sulphur toeach mercury atom.We thank Prof. O. P. Malhotrafor facilitiesandDr G. C. Percy,Universityof CapeTown, for thefar IR spectra.References1. ARTEMENKO, M. V. & SLYUSARKENKO, K. F., Zh. neorg.Khim., 10(1965),1145;GOODGAME, M. & WEEKS, M. J.,J. chem.Soc.,A (1966),1156;CHAN, N. N. y.,GOODGAME,M. & WEEKS, M. J., J. chem.Soc., A (1968),2499;DUFF, E. J., HUGHES, M. N. & RUTT, K. J., J. chem.Soc., A (1969),2126; HUGHES, M. N. & RUTT, K. J.,SPectrochim.Acta, 27 (1971),924; ARTEMENKO, M. V.,CHISTYAKOV'A, E. A., SUPRUNENKO, P. A. & KALNAJA,G., Zh. neorg.Khim., 16 (1971),1082; ARTEMENKO,M. V., SLYUSARENKO, K. F., SUPRUNENKO, P. A. &KALNAJA, ~., Zh. neorg.Khim., 18 (1973),1033.2. CLARK, R J. H. & WILLIAMS, C. S., Inorg. Chem., 4(1965),350.3. DEACON, G, B" GREEN, J, H, S. & HARRISON, D. J.,Spectrochim,Acta, 24A (1968),1921; AHUJA, I. S. &RASTOGI, P" J. chem,Soc" A (1970),378,2161;AHUJA,I. S., Inorg. nucl, chem,Left" 6 (1970),879,4. HVOSLEF, J., Acta chem.scand.,12 (1958),1568.5. JONES, L. H., J. chem.Phys., 27 (1957),665.6. JAIN, S. C. & RIVEST, R, Inorg. chim. Acta, 4 (1970),291; AHUJA, 1. S. & GARG, A., J. inorg. nucl. Chern.,33 (1971),1515,2074;AHUJA, 1. S. & SINGH, RAGHUV'IR,Inorg. chirn. Acta, 7 (1973),565; Inorg. nucl. chern.Left.,10(1974),421;AHUJA, I. S. & SAMBASIV'ARAO, K..J. inorg. nucl. Chem., 37 (1975), 586.7. AHUJA, I. S. & GARG, A., J. inorg.nucl. Chem.,34 (1972),2681-8. DAVIS, A. R, MURPHY, C. J. & PLANE, R A., Inorg. Chem.,9 (1970),423; AHUJA, I. S. & GARG, A., J. inorg.nucl.Chem.,34 (1972),1929,2074.Complexesof Organotin(IV) Halides withNeutral Schiff Bases of Salicylaldehyde&2-Hydroxy-l-naphthaldehydewith2-AminopyridineT. N. SRIVASTAVA, A. K. S. CHAUHAN & V. K. AWASTHIChemistryDepartment,Lucknow UniversityLucknow 226007Received14 March 1977;accepted25 May 1977Schiffbasecomplexesof the typeRnSnXc-n(SB)2(whereX =CI, Br, I, SB=Schiffbasesderivedfrom2-aminopyridineand salicylaldehydeor 2-hydroxy-I-naphthaldehyde)havebeensynthesizedand charac-terizedby elementalanalysis,infraredand electronicspectroscopyand conductivitymeasurements.Theli~andsbehaveas monodentatecoordinatin~throu~hazomethinenitrogenatom. An octahedralstructureis suggestedfor thecomplexesin solidstate.RECENTLY transitionmetalcomplexesof N-2-(2'-pyridyl)-ethylsalicylidimines(Ia) have beenreported1,in whichthe basesbehaveas monofunc-1023..•

2-Methylbenzothiazole Complexes of Hg(II) Halides & Pseudohalides

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2-Methylbenzothiazole Complexes of Hg(II) Halides & Pseudohalides

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