Oxazolidine-2-thione as ligand towards cobalt(II) halides

Spectrochimica Acta, Vol. 38A, No. 12, pp. 1303--1305, 1982

0584-8539[821121303-03503.00/0

Printed in Great Britain.

© 1982 Pergamon Press Ltd.

Oxazolidine-2-thione as ligand towards cobalt(l]) halides FRANCO CRISTIANI, FRANCESCO A. DEVILLANOVA,ANGELO DIAZ and GAETANO VERANI Istituto di Chimica Generale ed Inorganica, Via Ospedale 72, 09100 Cagliari, Italy

(Received 17 May 1982) Abstract--Although oxazolidine-2-thione (oxt) is unstable enough to give a ring opening, it reacts with cobalt(II) halides forming Co(oxtz)X2 complexes (X ffi CI, Br, I). The complexes are S-bonded; using i.r. spectroscopy it can be seen that the cobalt-halogen vibrations are in the expected range, while a common vibration at 234 cm-t is tentatively attributed to vCoS, Colour and magnetic studies carried out on the chloro-derivative as well electronic spectra support a tetrahedral stereochemistry around cobalt(II). From the electronic spectra in the solid state, the crystal field parameters have been calculated and the oxt is inserted in the spectrochemical series of cobalt(II), INTRODUCTION

Recently

[1] we

have

reported

reactions

of this stereochemistry. In order to avoid the complex dissociations, the spectra were recorded in

of

g~'~p m ~ . We f ~ ~hm ~ m ~ m ~e~, mercury chloride and bromide react with oxt to give coordination compounds of the general formula MoxhX2 (X = halogen), whereas zinc halides arab mercury "~o~/t~e "m~uce a 6-tlg o oedt~z. ~'d~s property makes the oxazolidine ring very interesting when compared with similar rings, such as imidazolidines, thiazolidines and pyrrolidines, which are much more stable. The stability accounts for the impossibility of Synthesizing the

oxazo?'~diae-2-se?one by the reaction at oxt with methyl iodide ~21 and subsequent nucleophilic have we been able to prepare N-methy~-oxazo~b dine-2-selone; the presence o f a methyl group probably makes the oxazolidine ring more stable. In order to pursue the study on oxt, especially f ~ m the p~int of ~ie~ ~f its d ~ s~bflit~), ~ e ha'ce considered the reaction of oxt with halites of cobalt(II). Continuation of this research is stimulated by the importance of the oxazolidine ring in severa~ com.~ounbs 01 ~3oSo~c~ 3me~vs~ )~). RF_~ULTS AND DISCUSSION

By reacting oxt with cobalt(II) halides in a 2:1 molar ratio, using a mixture of acetone and dimethoxipropane as a solvent, crystalline complexes of the Co(oxh)X2 (X = CI, Br, I) type have been obtained. The elemental analyses, colours and melting points of the complexes are shown in Table 1. The conductivity measurements, carried out in acetone at room temperature, were very low (AM < 10ft -t cm 2 tool-'), thus showing that the halogen was involved in the coordination sphere. "[he colours oi the complexes indicated that, as found for similar ligands [5-7], the cobalt was merry, The electronic spectra of the complexes recorded in acetone solutions were a confirmation

in Table 3, support the tetrahedral stereochemistry. In order to identify the coordinating atom, the ~u~.~o~'~ands oi oat an~ "t~ c o m dtexes are compared in Table 2. From these, it is clear that all the complexes were S-coordinated to the Co(ID. In fact, the band at 1530vs cm-', due to v C N + 8NH, undergoes upward shifts, while the band at 515 c m - ' , which retains the highest contribution of u C ~ [8]', shuts to 49? cm-" in the comp?exes. Oa the other hand, the vadat/ons of the stretching the ~h-o;e~ as coor~ma~,~ng a~om. In agreement with a C2, local symmetry o f CoS2X~, two metal-halogen (Am+B,) and two metal-sulphur (A,+Be) vibrations were to be very probably the uCoI symmetric vibration falls down to 200cm-', for the chloro- and bromocomplexes, two bands, attributable to the uCoX v'fv~,a~ons. ~ e t e ~oca'te6 "m ~g~eeme~'t ~'~'~n ~na~ f o u n d for analogous complexes with similar ligands [5-7]. As far as the uCoS vibrations are concerned, over 200cm -~ only one band at 2 3 4 c m - ' was common to the three complexes, it could have originated from the cobalt-sulphur interaction. Table 1. Elemental analyses, colours and melting points of the Co(ID complexes with oxt Compound

Colou.v

Analysls (calcd%)

m.p.

C

H

N

(oC)

Co oxt 2 C12

cleaz" blue

21.3(21.~)

3.1(3.0)

8.3(8.3)

127

Co ox~,, B~

blue

17.0(16.9)

2.6(2.~)

6.7(6.6)

1~8

Co oxt 2 12

gz.een

13.6(13.9)

l.g(z.g)

5.S(5.~)

1~2

1303

FRANCOCRISTIANIet al.

1304

Table 2. Principal i.r. bands of oxt and its (Co(II) complexes in the 4000-200 cm -t range (solid phase) Compound

vNH

uCN+6NH

ANH

uCS

uCoS

uCoX

oxt

3210s

153Ovs

695sbr

515s

Co oxt 2 C12

330Os

1538vs

577sbr

~97s

233m

328m - 314m

Co oxt 2 Br2

33008

15gOvs

577sbP

497s

234m

259s - 234m

Co oxt 2 I 2

32£08

1533vs

565sb~

497s

234m

216s .- -

Table 3. Electronic spectraa and crystal field parameters for the Co(II) complexes Co ox¢ 2 Cl 2

4TI(F)

Co o x t 2 Br 2

Co oxt 2 12

gA 2

~2Ccm-1)

7400-5650

6900-5q-50

6350-5195

16780-15430-13320 16330(324)-15385(qO6)-14100(321)c

15810-14870-12990 15175(463)-i~750(982)-14035(396)c

1~600(564)-13970(620)-

6310

6110

5760

~3(oa )

15030

i~420

13680

~(cm-1)

364.5

353

333

B,(cm -I)

694

662

630

8d

0.72

0.68

0.65

4Tz(p).

4A2

v3(cm-I )

1~815-14000-12660 13330(519) ¢

--b

-1

v2(cm b

)

-i

~Solid phase. bEvaluated according to ref. [9]. CThe spectra were recorded in acetone at 25°C on solutions containing the complex ( - 3 x 10-3 M) in presence of an excess of oxt ( - 5 x 10-2 M). dB (free ion) 967 cm -~, according to ref. [15].

Although the complexes have a C2~ local symmetry, the v2 and v3 are classified according to a Td point group, as 4TI(F)*--4A2 and 4TI(P)*--4A2, respectively. F r o m the envelopes of these absorptions, ='2 and u3 were visually estimated as suggested by COTTON et al. [9] and used to evaluate the crystal field parameters [10]. As expected, the Dq values were dependent on the halogen and decrease in the order Cl > Br > I. In order to insert oxt in the spectrochemical and nephelauxetic series, the averaged ligand field approximation was used to estimate the electronic parameters of [Co(oxh)] 2+, since it was impossible to prepare it as tetrafluoborate. The calculated Dq, B' and /3 values are shown in Table 4, together with the values previously reported for similar pentaatomic rings. The value of 413 c m - ' , obtained for the Dq of oxt, inserts this ligand immediately below the thiourea in the spectrochemical series

for tetrahedral Co(II) complexes, thus differentiating it from the other pentaatomic rings. This result agrees well with those obtained from XPS measurements on oxt and related pentaatomic rings, i.e. imidazolidine-2-thione (dit), pyrrolidine-2-thione (pit) and thiazolidine-2-thione (ttz) [18]. In fact, the binding energy values of N l s and S2p of oxt are closer to those of dit rather than to those of pit and ttz. This was explained in terms of a different weight of the resonating form (C) (see Scheme 1) which is practically nonexistent for X = CH2 and S.

S (~)

S(b)

S(c)

The //-value is slightly lower than those found for the other similar complexes according to a

Oxazolidine-2-thione as ligand towards cobalt(H) halides

1305

Table 4. Spectral parameters for CoS4 tetrahedron for similar ligands Compound

Dq(cm-I)

Bt(cm -l)

8

Ref.

Cotu~(ClO~) 2

~25

600

0.62

ii

[Co oxt~ 2+

~13a

63~a

0.66 a

this work

Co imme~(Cl04) 2

~02

651

0.57

12

[Co ditet~ 2+

397a

651a

O.67 a

5

[Codi~=e~] 2*

3,2 a

668"

06g ~

5

Co dit(ClOg) 2

378

551

0.67

13

Co diditetw(BF) 2

374

562

0.68

7

Co didltme4(BF4) 2

371

663

0.69

7

Co pitme4(CIOg) 2

338

707

0.73

14

Co pltw(ClOq) 2

325

718

0.7~

14

aCalculated from the averaged lignnd field approximation. Symbols: tu = thiourea, imme -- N - methyl - imidazolidine - 2 - thione, ditet = N - ethyl - imidazoildine - 2 - thione, ditme = N - methyl imidazolidine - 2 - thione, etu = ethylenethiourea, diditet ffi N , N ' diethyl - imidazolidine - 2 - thione, diditme = N,N' - dimethyl imidazolidine - 2 - thione, pitme = N - methyl - pyrrolidine - 2 - thione, pit = pyrrolidine - 2 - thione.

:

l o w e r o r b i t a l o v e r l a p , a n d c o n f i r m s t h e s u l p h u r as coordinating atom. EXPERIMENTAL

Oxazolidine-2-thione was prepared and purified according to literature [16]. All the complexes were obtained as crystals by refluxing oxt and the cobalt halide in a 2:1 molar ratio in a dimethoxipropane-acetone mixture (1:4 vol.). Magnetic measurements at different temperatures were carried out on the chloro derivatives, prepared in the appropriate amount. The molar susceptibility values were corrected for diamagnetism ( - 172 × 10~ ) and T.I.P. (576 × 10-6). From the straight line (correlation coefllcient=0.998) obtained by reporting 1/X~ c°r' vs T, the Curie-Weiss constant (0 = - 13.6) and/~ef (4.79) were evaluated. The value is in good agreement with a high spin tetrahedral complex of Co(H) [17]. The i.r. spectra were recorded on a Peridn-Elmer 325 spectrophotometer as KBr discs (4000--400 cm -~) and as Nujol mulls between CsI pellets (450-200 cm-'). The magnetic susceptibility measurements were carried out by use of the Gouy method at different temperatures (125-260 K) using liquid air. The visible spectra in acetone were recorded with a Perkin-Eimer 402 spectrophotometer. The: electronic spectra in the solid state were recorded with a Shimadzu MPS-50L spectrophotometer in the range 400027000 cm -t . The conductivity measurements were carried out with a WTW, LBR type conductivity bridge on 10-3 M solutions.

Acknowledgement--We thank the C.N.R. of Rome for its financial support. REFERENCES

[1] F. A. DEVILLANOVA and G. VERAm, J. Coord. Chem. 7, 177 (1978).

[2] T. MUKAIYAMA, I. KUWJIMA and K. MIZUl, Y. OrE. Chem. 31, 32 (1966). [3] F. A. DEVILLANOVAand G. VERANI, ]. Heterocyclic Chem. 17, 571 (1980). [4] E. B. ASTWOOD, M. A. GREER and M. G. ETrLINGER, ]. Biol. Chem. 181, 121 (1949). [5] F. A. DEVILLANOVA and G. VERANI, Inorg. Chim. Acta 30, 209 (1978). [6] F. A. DEVILLANOVA and G. VERANI, ]. Inorg. NucL Chem. 42, 623 (1980). [7] F. A. DEVILLANOVA and G. VERANI, Trans. Met. Chem. 5, 42 (1980). [8] F. A. DEVILLANOVA, K. R. GAYATHRI DEVI, D. N. SATHYANARAYANAand G. VERANI, Spectrochim. Acta 36A, 199 (1980). [9] F. A. COTTON, D. M. L. GOOD6AME and M. GOODGAME, ]. Am. Chem. Soc. 83, 4690 (1961). [10] Y. TANABE and S. SUGANO, J. Phys. Soc. Japan 9, 753 (1954). [11] F. A. COTTON, O. D. FAUT and J. T. MAGUE, Inorg. Chem. 3, 17 (1964). [12] E. S. RAPER and J. L. BROOKS, J. lnorg. Nuci. Chem. 39, 2163 (1977). [13] R. L. CARLm and S. L. HOLT, JR, Inorg. Chem. 2, 849 (1963). [14] S. g . MADAN and M. SuucH, Inorg. Chem. 5, 1662 (1966). [15] W. E. SLINKARD and D. W. MEEK, Inorg. Chem. 8, 1911 (1969). [16] M. G. ETTLINGER, ]. Am. Chem. Soc. 72, 4792 (1950). [17] H. L. SCHL~,FER and G. GLIEMANN, Basic Principles of Ligand Field Theory. Wiley-Interscience, Bristol (1969). [18] M. BOSSA, F. A. DEVILLANOVA, C. FURLANI, G. MATTOGNO, G. VERANI and R. ZANONI, X I I Congresso Nazionale di Chimica Inorganica, Trieste, September (1979).