Geetharani, K.

Sathyanarayana, D. N.

English

NOPR

Indian Journal of ChemistryVol. lfA, December 1976, pp. 925-928Normal Vibrations & Donor Characteristics of Thiazoline-2-thione:Complexes with Cu(II), Cd(II), Ni(II) & Hg(II)K. GEETHARANI & D. N. SATHYANARAYANADepartment of Inorganic & Physical Chemistry, Indian Institute of Science, Bangalore 560012Received 19 ] allllary 1976; accepted 6 11,1arch 1976The complexes of thiazoline-2-thione(Tzt) with Ni(II), Cu(II), Cd(II) and Hg(I1) Chlorideshave been studied. The assignment of infrared bands of the ligand and its metal complexesis made by comparison with related molecules and with the help of normal coordinate treatmentof Tzt and N-deuterated Tzt. The ligand is inferred to coordinate through nitrogen in the Cd(II)complex and through the exocyclic thiocarbonyl sulphur in the other three complexes.A DETAILED IR spectral study of thiazolidine-2-thione (Tzdt ) and its metal complexes withvarious metal chlorides was reported by usearlier". It was found that Tzdt exhibits ambi-dentate nature, coordinating through nitrogen toCd(II) and Zn(II), and through the t hiocarbonylsulphur in Co(II) , Ni(II) and Hg(II) complexes. Astructurally related ligand, but simpler than Tzdtis thiazoline-2-thione (Tzt), whose donor characteris-tics have not been investigated so far.H H"'- /c'=c,I IHN 5,"'-/CIISTztIt was of interest to study its complexes. Thecomplexes formed by this ligand with Ni(II), Cn(II) ,Cd(II) and Hg(II) chlorides are reported in thispaper. Further, the IR spectra of the ligand andcomplexes are assigned by comparison with relatedmolecules and also with the aid of normal coordinatetreatments of Tzt and N-deuterated Tzt-d1.Materials and MethodsThe ligand Tzt was obtained through the courtesyof Prof. M. Chanon and Dr C. Roussel, Laboratoireassocie au CNRS, Marseille, France. The N-deute-rated Tzt-d1 was prepared by repeated exchangereaction of Tzt with D20. Other chemicals were ofhigh purity.Preparation oj the complexes - The complexes ofCu(II), Cd(II) and Hg(II) chlorides precipitated outwhen an alcoholic solution of Tzt (O·02M) was addedto the corresponding metal chloride solution (O·OIM)in ethanol. The precipitate was filtered, washedwith ethanol and dried.The i'Ji(II) complex was prepared by refiuxing asolution of NiCI2.6H20 (O·OIM) in absolute alcoholwith Tzt (O·02M) and an excess of ethyl orthoformatefor over 8 hr. The precipitated yellow complexwas filtered, washed with hot toluene and dried.Analysis - The metals were determined by stan-dard procedures- and the C, Hand N analyses wereperformed microanalytically at the Bhabha AtomicResearch Centre, Bombay. The analytical data ofthe complexes are given in Table 1.Physical measurements - The instruments used andthe methods adopted have been described earlier",Normal coordinate treatment- We assumed themolecule to be planar with molecular symmetry C, andin this model, the 21 fundamental vibrations of Tztare classified into 15A' + 6A" modes. The in-plane(A ') vibrations are considered for the calculationsthe out-of-plane (A") vibrations are assigned em-pirically by comparison with related molecules.The secular equations were set up according tothe GF matrix method", The internal coordinatesTABLE 1 - ANALYTICALDATAOF Tzt CO~IPLEXESComplex Colour Analysis (%)*?II C H NNi(Tzt).Cl2 Yellow 16·28 20'01 1·72 7'88Cu(Tzt)Cl2(16'15) (19'80) (1·65) (7'70)Green 25·11 14·85 1·31 5·46(25,27) (14'32) (1-19) (5'50)Cd(Tzt)Cl2 White 37·02 12·21 1·08 4·73Hg(Tzt)2Cl2(37-43) (11'99) (0'99) (4·66)White 39·77 14·81 1·23 5·48(39-68) (14-24) (1,19) (5'54)*Calculated values are given in parentheses.925INDIAN J. CHEM., VOL. 14A, DECEMBER 1976are shown in Fig. 1 and the internal symmetrycoordinates were written down in the same way asfor a five-membered ring4 and are not given here.The structure parameters were taken from thedata of related thiazole moleculess-", They are:bond lengths, c-s 1'65, C-Sl, 1'823, C1-S 1'80, C'-N1'40, C-N 1·50, C-C 1·34, N-H 1'02, C-H 1·08 A;and bond angles, CNC' 112°, NCS1, SCSI 109°15",NCC, CCS 115°, HNC 124° and HCN, HCS 122°30'.We used a Urey-Bradley force field and the forceconstants were transferred for the HN-C(S)-S-group from our earlier results of Tzt! and those for-HC=CH-group from imidazole", An interactionconstant, f (C=C, C'ClH), was however found neces-sary. Some of the force constants were iteratedwithin the small ranges found in related moleculesto obtain better frequency fits both for Tzt andTzt-d1. The Urey-Bradley force constants werefound to be satisfactorily transferable. The finalTABLE 2 - FORCECONSTANTS(mdynjA) FORTztStretching Bendinu Repulsiontees 3-65 HNes 0·27 FNCS HOxes, 2·65 HSCS 0·20 Fses 0·40KC,s, 3·05 HNCS, 0·35 Fxcs, 0·60KeN 4·65 Hcsc 0·32 Fcs,e 0'55Ke'N 5·35 Hces 0·30 Fccs, 0·44nee 4·45 HNCC 0·35 FNec 0·60KNH 4·70 HCNC 0·25 FCNC 0·42KC'H 4·45 HHCN 0·17 FHCN 0·35KC,H 4·25 HHC'C, 0·26 FHC'C, 0·32jCC,C'C,H 0·25 HHC,C' 0·22 FHC,C' 0·32(mdynjrad.)HHC,S 0·14 FHe,s 0·15HHNC 0·29 FHNC 0·50HHNC' 0·22 FHNC' 0·40force constants are shown in Table 2. The calcu-lated frequencies for Tzt and Tzt-dl are listed inTable 3 together with the observed frequencies andassignments from the potential energy distributions(PED).Results and DiscussionMost of the bands of Tzt arise from mixed vibra-tions as in secondary thioamidess-" and many ringcompoundst-!''. For the assignment of Tzt (Tables 3and 4), the comparison with structurally closelyrelated thiazole'? is extremely satisfactory. ForFig. 1 - Molecular structure and internal coordinates ofthiazoline-2-thione (Tzt)TABLE 3 - INFRARED FREQUENCIES (cm-l) FOR A' MODESOF Tzt AND Tzt-dl ANDTHEIR ASSIGNMENTTzt-d1 Tzt Assignment+] (PED %)§Obs. Calc. ~*(%) Obs. Calc. ~*(%)2250 2253 0·1 3080 3080 0·6 vNH(100)31202983 2983 0·0 2980 2983 0·1 vaCH(52), vsCH(47)2885 2882 0'1 2885 2882 0·1 vsCH(52). vaCH(47)940 941 0·1 1555 1547 0'5 8NH(45), vC'N(28).vCN(14)1480 1502 1·5 1465 1456 0·6 8C'H(31). 8NH(22),vCC(22)1385 1390 0·4 1340 1329 0·8 vCN(57), vC=S(15),8NH(12)1250 1241 0·7 1245 1229 1·3 8C1H(39). vCC(35),vCISI(ll)1175 1189 1·2 1145 1132 1·0 IlC'H(56), vC'N(22)1100 1107 0·6 1070 1085 1·4 8C1H(29), vC=S(17),vC'K(14)1070 1079 0·8 1050 1053 0·3 Ilring(23), vCC(18),vCS1(18)850 851 0·1 850 853 OA Ilring(41), vC1S.(38)690 664 3·8 690 683 1·0 "CSd46), vC=S(15),8ring(17)642 646 0·6 650 646 0·5 8ring(481. VC1S1(14)465 467 0·4 465 470 1-1 8ring(55), vC= S(30)312 318 1'9 320 320 0·6 8C=S(75), "CSI(13)·~(%)=(!vabs-'Jcalcl xl.00)/vabs where v. denotes frequency. .t...=stretching, Il=bendmg, s=symmetnc and a=anhsymmetnc.tThe assignment given here is for Tzt and approximately corresponds as shown with that for Tzt-d1.§PED less than 10% is omitted.926GEETHARANI & SATHYANARAYANA: COMPLEXES OF THIAZOLINE-2-THIONETABLE4 - INFRAREDFREQUENCIES·(cm-1) OF Tzt ANDITS COMPLEXESANDTHEIR ASSIGNMENTTzt Ni(Tzt)2Cl2 Cu(Tzt)CIZ Hg(Tzt)2C12 Cd(Tzt)CIZ Cd(Tzt -d1)C12 Mainassignment+1555 s 1556 s 1555 s 1567 S 1565 s 931 mw 8NH(D), -cx1510 ms1498 mw1465 s 1462 vs 1465 m 1470 s 1460 s 1465 vs 8CH, IICC1445 s1390 w 1388 w 1386 w 1385 w 1382 w 1338 w Cornbn band1340 vs 1350 sh 1358 m 1363 s 1345 ms 1390 ms IICN1340 s 1310 ms1278 vw 1305 vw 1305 vw 1305 vw 1319 mw Combn band1245 vs 1258 m 1266 mw 1275 m 1252 m 1250 w IICC,8CH1235 mw1144 S 1145 m 1155 s 1140 s 1132 s 1130 mw 8CH1130 s 1138 sh1070 vs 1070 vs 1098 m 1070 vs 1070 vs 1100 sh 8CH, ring str.1088 m 1088 vs1050 vs 1053 vs 1052 s 1050 vs 1060 vs 1062 s Ring str.1050 vs 1050 vs850 vs 860 s 880 m 870 vs 855 S 868 s 8ring, IICS862 m 862 m 852 s800 vs 790 m 785 m 818 m 695 vs 505 ms r.NH(D)732 vs 732 vs 745 vs 740 m 740 m 740 sh 1tCH710 vs 717 vs 730 sh 730 s 715 s 732 m 1tCH690 vs 699 vs IICS650 s 650 w 655 mw 655 vw 655 sh 650 vw 8ring, IICS580 m 582 vw 630 ms 585 mw 597 vs rering614 ms491 s 492 ms 517 w 495 ms 490 ms 490 s rering495 m465 s 463 mb 445m 445 ms 461 ms 458 ms aring322s 340 w 343 s 340 vs 322 s nit 8C=S305 s 300 w 300 s 295 w nit rcring290 sh265 wb 275 mw 220 vs 265 mw nit IIM-CI230 w*NH and CH stretching frequencies are not tabulated.t1t=out-of-plane bending; II, 8 same as in Table 3.tni=not investigated.brevity, we shall now discuss only some of themajor assignments of Tzt, which could be useful inthe study of its complexes.NH modes - The NH stretching mode of Tzt iseasily assigned and it occurs as a doublet at 3080,3120 em+ in the solid state. The NH in-planebending band at 1555 em? is coupled withCNstretching and occurs in the same region as insecondary thioamides, but is about 100 em? lowerthan in N-alkyl dithiocarbamates'", On deuterationthis band vanishes and the ND bending mode isobserved near 940 crrr+.CN stretching - The CN, C'N stretching vibra-tions are mixed with other vibrations, mainly NHand CH bending modes. The bands at 1340 and 1555crrr? have major contributions from CN stretchingmodes. In Tzdt, the bands at 1520, 1302 and 1260em? have large contributions from CN stretchingmodel. The CN stretching mode in secondarythioamides is fairly localized and is found near1440 crrr".CS modes - The exocyclic C=S stretching vibra-tion is highly delocalized and the bands at 1340,1070 and 690 crrr! have smaller contributions fromthis mode, and the 465 crrr" band arising mainlyfrom ring deformation has 30% C=S stretching.This situation is similar to that in Tzdt. Theendocyclic C-S stretching bands near 850, 6C;0 and650 em? are comparable with those of simple andn-alkyl dithiocart amates'! which have (asymmetricand symmetric) C-S frequencies near 820 and 620crrr-. A band at 320 cm-I may be attributed tothe exocyclic C=S bending corresponding to the290 cm-I band of Tzdt.Out-of-plane vibrations - A very strong band at800 cm-1is assigned to the NH out-of-plane bending.This band disappears on deuteration and the NDbending mode in Tzt-dl is observed at 548 cm-l asis to be expected. This frequency is about 100cnr"higher than in Tzdt- and secondary thioamidess-v,but is nearly 100 cm! lower than in N-alkyl dithio-carbamatest-, The remaining CH and ring bendingmodes are easily assigned by comparison withthiazole!? (see Table 4).Complex oj Tzt - The Ni(II) complex decomposeson exposure to moisture, while the other complexesare stable. The molar conductances of these com-plexes in nitrobenzene (1O-3M) were nearly zero(AM,....,l to 10) showing the coordination of chlorideions to the metal.Infrared spectra oj the complexes - The infraredfrequencies of the ligand and its complexes togetherwith their main assignments are presented in Table 4.On comparing the spectrum of the ligand with thespectra of the complexes, no striking changes areobserved in the C-N and C-S stretching regions.However, the bands due to the NH group are shiftedconsiderably in the complexes.927INDIAN J. CHEM., VOL. 14A, DECEMBER 1976The NH stretching band is generally observedas a doublet in the complexes as in the ligand. Inthe Cd(II) complex the NH stretching frequency isobserved at a considerably higher frequency, at3220 em"! whereas in the other complexes, it isfound almost in the same region, 3090-3160 em? asin the ligand. This is similar to that of Tzdt+,where the NH stretching band of the ligand isshifted to higher frequencies in Cd(II) and Zn(II)complexes, indicated to have N-coordinated Tzdt.The NH stretching band of Tzdt is not muchaffected in the complexes of Ni(II), Cu(II), etc.containing S-bonded Tzdt. The increase in NHstretching frequency of Tzt in the N-bonded com-plexes is attributed to an increase in the positivecharacter of the ring nitrogen on bonding to a metalion. The results seem to indicate the Tzt is bondedthrough nitrogen in the Cd(II) complex, and throughthe exocyclic sulphur in other complexes. Thisinference is supported by the different behaviour ofNH out-of-plane bending in the Cd(II) complex incontrast to the other complexes. The NH out-of-plane bending of Tzt at 800 crrr ' is found in Ni(II),Cu(II) and Hg(II) complexes almost unaffected butwith slightly reduced intensity. On the other hand,the Cd(II) complex has no band in this region butexhibits a very strong band at 695 cnr ' (absent inthe other complexes). Similar substantial down-ward shifts (60-80 cm-I) of the ligand NH out-of-plane bending are noted in the N-coordinated Cd(II)and Zn(II) complexes of Tzdt, while the S-bondedcomplexes show no or negligible shift.'. That theNH out-of-plane bending band shifts to lower fre-quencies in the Cd(II) complex is further confirmedby preparing the Tzt-d complex of CdCI~ (using theprocedure given for Tzt complex), presumed to beCdCl~,Tzt-dl and studying its IR data (Table 4).The 548 em"! band due to ND out-of-plane bendingof Tzt-d1 is shifted to a lower frequency (505 crrr+)in the complex. Thus the NH out-of-plane bendingband seems to be sensitive to the type of bending.The C=S bending of Tzt at 322 crrr ' is unaffectedin the Cd(II) complex, whereas in the other com-plexes it is shifted to near 340 cm! as expected whenbonding of Tzt is through the exocyclic sulphur.We exclude the bonding of Tzt through ring sul-phur since the exocyclic thiocarbonyl sulphur islikely to be the donor as in secondary thioamidesand more negative charge residing on this atomby resonance. The possibility of Tzt coordinatingas a chelate through both the sulphur atoms seemsunlikely since in such a case substantial changesin the IR bands below 600 cm " on chelation dueto ring deformation modes are expected. Further-more, the electronic spectral band positions of theNi(II) complex (given later) closely resemble thoseof benzothiazole!", ethylenethiourea 13 and Tzdt-!complexes of the type NiCI2.2L containing S-bondeclligands and bridging ci- groups. The M-Cl bandsappear to support the presence of bridging chloridegroups.Metal-chloride and metal-ligand vibrations - In theNi(II) complex, there are two weak bands at 265and 230 crrr", which could be attributed to M-Clstretching. This is in agreement." with that ex~pectecl for polymeric octahedral complexes of com-928position NiL2Cl2, where L = pyridine, toluiclines,etc. A medium weak band at 265 crrr'! in Cd(Tzt)-Cl., and at 275 cm! in Cu(Tzt)Cl2 for bridging M-Clstretching are compatible with the values reportedin polymeric complexes of the type LMCI. contain-ing bridging chloride groups"; Hg(TzthCl~ showsan intense absorption at 220 ern -1 which could beassigned to M-Cl stretching vibration-P-!", Thiscomplex is likely to have a tetrahedral geometryand the other M-Cl stretching mode expected fortetrahedral complexes of composition L~MC12 maybe below 200 cm'.Metal-nitrogen stretching for the Cd(II) complexis expected around 320 cm', and the metal-sulphurfrequencies for the other complexes, around 320-360 cm". But no new bands are found in thisregion, presumably these bands may be too weak,overlapping with the ligand bands.Electronic spectra - The solid state spectra ofCu(II) and Ni(II) complexes were taken in thevisible region. Cu(Tzt)CI~ shows a weak absorptionat 70el nm indicating square planar or octahedralgeometry for this complex. A polymeric Cu(II)complex with bridging chloride ions is likely. Thevisible spectrum of the nickel(II) complex shows afairly strong absorption at 448 nm, as a shoulder toan intense charge-transfer band, a weak broad bandat 770 nm and a still weaker band at 1250 nmtypical of nickel(II) ion in an octahedral geometry.The band positions closely agree with those in octa-hedral NiCI2.2L complexes, where L = Tzdtt-, ethy-lene thiourea-" and benzothiazole".AcknowledgementThe award of a Science Talent Search Fellowshipto K.G.R. bv the National Council of EducationalResearch al{d Training, New Delhi, is gratefullyacknowledged.References1. GEETH_\RA~I, i.e. & SATHYANARAYA~A, D. x., l ndian J.Client. (in press) and references therein.2. VOGEL, A. I., A text book of quantitat iue inorganic analysis(Longmans, Green & Co., London), 1969.3. \VILSO~, E. B., Drccrus, J. c. & CROSS, P. c.. Molecularvibrations (:\IcGraw-Hill, New York), 1955.4. NAKAMOTO, K., in Spectroscopy and structure of metalchelate compounds, edited by K. Nakamoto & P. J.:\lcCarthy (J. Wiley, New York), 1968.5. BAK, B., CHRISTENSEN, D., NYGAARD, L. H. & ANDERSEN,J. R, J. molec. Spectrosc., 9 (1962), 222.6. iVIANGIA, A., NARDELLI, :'.1., PELIZZI, C. & PELIZZI, G.,J. chcm, Soc., Dalton (1972),2015.7. CORDES, iVI. & WALTER, J. L., Spectrochim. Acta, 24A(1968), 237.8. SUZUKI, I .. Bull. chem, Soc. Japan, 35 (1962), 1286;1449; 1456.9. RAO, C. N. R & CHATURVEDI, G. C., Spectrochi m Acta,27A (1971), 520.10. SBRANA, G., CASTELLUCCI, E. & GINANESCHI, :\1., SPec-trochim, Acta, 23A (1967), 750; and references therein.11. KAKAMOTO, K., FUJITO, J., CONDRATE, R. A. & MORI·MOTO, v.. J. chem, Ph),s., 39 (1963), 423.12. DUFF, E. J., HUGHES, M. N. & RUTT, K. J., J. chem,Soc. (A) (1968), 2354.13. HOLT (Jr), E. L. & CARLIN, R L., J. Am. chem, Soc.,86 (1964), 3017.14. FILIPPO, D. DE & PRETI, C., J. chem, Soc. (A) (1970),1904.15. FERRARO, J. R, Low-frequency vibrations of inorganicand coordination compounds (Plenum Press, New York),1971.16. ADAMS, D. 1\1.,Metal ligand and related vibrations (Edward,.London), 1967.

Normal Vibrations & Donor Characteristics of Thiazoline-2-thione: Complexes with Cu(II), Cd(II), Ni(II) & Hg(II)

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Normal Vibrations & Donor Characteristics of Thiazoline-2-thione: Complexes with Cu(II), Cd(II), Ni(II) & Hg(II)

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