Polyhedron Vol. 2. No. 6, pp. 443-W 1983 Printed in Great Britain.

0277-5367/83/06044~W3,Mt/0

Pewmon Press Ltd.

MULTINUCLEAR MAGNETIC RESONANCE AND RELATED STUDIES ON SOME ORGANOTIN(IV)

COMPLEXES OF DITHIOCARBAZATES

ANIL SAXENAt and J. P. TANDON*

Department of Chemistry, University of Rajasthan, Jaipur 302004, India

(Received 11 May 1982)

Ah&act-Synthesis, characterization and geometrical features of pentacoordinated dibutyltin(IV) dithiocarbazate complexes of the type n-Bu#n L {(where L = dianion of S-methyl-B-N (2-hydroxy-phenyl) methylene and methyl dithiocarbazate} are described. These are obtained as viscous oils from the reactions of a-Bu2SnO with equimolar proportions of the ligands in benzene. On the basis of UV, IR, NMR (‘H, “C, ’ t9Sn) spectra along with the mass spectral fragmentation pattern a trigonal bipyramidal geometry is proposed. The N atom probably occupies the axial site, while the remaining two donor atoms 0 and S and the dibutyl groups rest in an equatorial plane. These complexes are active against P.388 Lymphocyte leukaemia system.

The number and diversity of S N chelating agents used to prepare new coordination and organometallic compounds has increased rapidly during the past few years. The pronounced biological activity’.’ of the metal complexes of ligands derived from dithiocarbazic acids has created considerable interest in their coordination chemistry. Complexes of dithiocarbazates with many different transition metal ion? have been studied extensively over the last years and only limited information on the bonding and structural features is available for the tin(W) complexes.’ Our continuing interest in chelated tin(W) derivatives6 has led us to describe the synthetic and stereochemical features of some dibutyltin(IV) dithiocar- bazate complexes.

EXPERIMENTAL

Materials and methods. Chemicals and solvents used were dried and purified by standard methods, and moisture was excluded from the glass anoaratus using CaCI, drying tubes. The ligands were prepared by-the literature-method.’ The complexes were prepared, purified and analyzed by methods similar to those reported in our earlier publications.’

Spectral tieasuremenfs. The electronic spectra were recorded in methanol on a Pye-Unicam-SP-8-100 spectrophtometer. In- frared spectra were obtained on a Perkin-Elmer 577 grating spectrophotometer an Nujol mulls or in benzene solution. ‘H NMR spectra were recorded on a Perkin-Elmer RB-12 spec- trometer in CDC13 using TMS as an internal standard at 90 MHz. “C NMR spectra were recorded on Bruker HFX-90 spec- trometer in CHCI, using TMS as internal standard at 25.15 MHz. Counline constants were obtained from between 1008 and 12OMt p&s aid the assignments are based on off-resonance decoup- hng and satellite peaks. “‘%n NMR spectra were recorded on a Bruker HFX-90 soectrometer in CHCI, using TMT as external standard at 22.7 MHz. Mass spectra -were-recorded on VG Micromass- F spectrometer at 70 eV with ionization cham- ber at 220°C and calibrated using perfluorokerosene.

RESULTS ANDDISCUSSION The reactions of dibutyl tin oxide with the ligands

proceed smoothly with the elimination of water, which

*Author to whom correspondence should be addressed. tPresent address: School of Molecular Sciences, University of

Sussex, Brighton BNI !3QJ, England.

was removed azeotropically with benzene:

Bu,SnO + H2L + Bu,SnL t H,O. (1)

The derivatives so isolated are highly viscous oils, miscible with most organic solvents and hydrolyzable in nature.

In the electronic spectra of the ligands? a band at cc. 216 nm is observed which may be assigned to ‘B band of the phenyl ring. This shifts to higher wave length on complexation and is observed at cu. 222 nm in the com- plexes. Also the ligand chromophore >C=N, which ab- sorbs at cu. 290 nm, shifts to a higher wavelength and is observed at cu. 298 nm in the complexes. Three sharp bands are observed in the region, 250-270 nm and assigned as change transfer bands, suggesting the formation of u-bondsY and (p + d) bonds”’ between p-orbitals of 0 and S and vacant Sd orbitals of tin.

The IR spectra of the ligands” show a broad and strong band in the region, 3300-2850 cm-’ attributable to v(OH) and v(NH) modes and no band is observed at co. 257Ocm-‘, showing the absence of v(SH). However, it does appear in the solution spectra with the disap- pearance of v(NH) and v(C=S) bands. This suggests the existence of a tautomeric equilibrium’* between the two forms of ligand as shown below:

OH

2 F=N-NH-C

R \

SCH,

tthionr)

a OH

s 0 /SH C=N-N=C

k ‘SCH,

In the IR spectra of the complexes, all vOH or vSH bands are absent, showing the bonding of oxygen and

443

444 A. SAXENA and J. P. TANDON

sulphur to the metal by the loss of thiolic and phenolic protons of the ligands. A band of medium intensity at cu. 1585 cm-’ in the complexes may be assigned to v(C=N) vibration, and which originally appears in the ligand at ca. 1605 cm-’ in both the solution and solid states. The shift of this band to the lower energy indicates the coor- dination of the azomethine nitrogen to the tin aton? Two bands at cu. 600 and 510 cm-’ are also obser- ved and which may be assigned to (Sri-C) asymmetric and symmetric modes respectively and thus indicating the presence of a bent C-Sri--- moiety.14

Besides this, several new bands observed at cu. 565, 425 and 325 cm-’ in the complexes may be assigned to v(Sn-0), v(Sn-0) and v(Sn-S), respectively and thus lending support to the proposed coordination in the complexes.

In the ‘H NMR spectra, a broad signal at 8 7.15 ppm is observed in all the complexes owing to the phenyl pro- tons of the salicylaldehyde and o-hydroxyacetophenone residues. A further sharp signal is observed at 82.50 ppm attributable to the -CH3 protons of dithiocarbazate moiety, In the complexes, the disappearance of the sig- nals at ca. 811.20, 4.35 and 10.05 ppm assigned to OH, SH and NH protons, respectively, in the spectra of the ligands clearly indicates their deprotonation. Signals at S8.7ppm in complex (I) and 82.8 ppm in complex (II) occur owing to the -CH and -CH, protons, respectively. These are shifted downfield as compared to their posi- tions in the ligands owing to the coordination of C=N group with the metal atom. The complexes show ad- ditional signals at S 0.7-1.8 ppm owing to the protons of butyl group.

The mass spectral fragmentation scheme of the com- pound Bu2Sn[OC6H,.C(CH,): N.N.CS(SCH,)] is shown in Fig. 1. The molecular ion peak due to ‘19Sn isotope is observed at m/e 471. The peaks at m t 1 and m - 1 have also been observed due to the presence of “*Sn and ‘*‘Sn isotopes. The fragmentation starts with the simple cleavage of Sn-Bu bond eliminating Bu of 57 a.m.u. leading to the formation of a three coordinate Sn frag- ment ion15. The base peak is observed at m/e 352. However, the Sn-S bond is more readily cleaved than the Sn-0 bond. Some low abundance ions containing Sn-S at m/e 151 are also obtained by the processes not involv- ing cleavage of bonds16. The last step in the frag- mentation is the removal of HCN molecule, which is characteristic of the Schiff base complexes.”

“C NMR data have been recorded for both the ligands

_ y m/e 91 !? m/e 118 f m/e 237

Fig. 1. Mass spectrum of C1sH2&NZOSn.

Bu

Bu

Fig. 2. Structure of organotin complex.

and the complexes. The shifts in carbons attached to 0, S and N indicate the involvement of 0, S and N atoms in coordination. The a(C) shifts and ‘J(‘19Sn-‘3C) values of 555 and 561 Hz indicates the five coordination around the tin atom in these complexes. Domazetis et ~1.” have reported a value of 56OHz for Bu,Sn complexes of thioamino acids and which are further supported by Mitchell ef (11.‘~

These complexes give sharp signals at S-130.4 and - 156.7 ppm in ‘19Sn NMR spectra and which strongly support the five coordination around tin in a trigonal

Table 1. Analysis and physical characteristics of complex

Compound state Yield Color Mol. wt. Analysis g ---

% Found (Calcd.)

Sn 5 c H Found Found Found Found (Calc .) (Cslc .) (CdlC .) (Calc .)

(C4H9)2Sn(C9HgN2S20) Oily 95 Green 441.00 25.85 12.92 42.05 6.23 liquid 456.98 26.03 14.00 44.54 5.68

(C4H9)2Sn(C10H1$12S20) Oily 92 Yellow 453.00 24.92 12.23 43.92 5.13 liquid brown 470.98 25.26 13.58 45.86 5.94

Multinuclear magnetic resonance

Table 2. ‘H and ‘19Sn NMR data (8 ppm) of ligands and complexes

445

Ligands and complexes -OH -C6H4* -C-R -NT?! n-C H "'Sn R= -H

-CH3 49

= -CH3

OH.C6H4.CH:N.NH.C:S.S.CH3 11.20 7.20 a.52 9.95 2.45 -

(C4H9)2Sn(0.C6H4.CH:N.N:C.S:SCH3) - 7.11 8.70 - 2.50 0.70-l .a2 -130.4

0H.C6H4.C(CH3):N.NH.C:S.SCH3 12.52 7.10 2.55 10.05 2.48 -

(C4H9),Sn(0.C6H4.C(CH3):N.N:C.S.SCH3) - 7.16 2.82 - 2.57 0.62-1.80 -156.7

l = Centre of multiplet.

Table 3. ‘%Z NMR data of ligands and their organotin complex I_---

Structure Chemical shift in km 1 2 3 4 5 6 7 a 9

z 3

4 158.67 12G.36 133.53 121.09 123.45 117.92 146.6:: 13a.6L 18.~4

- ---~~_- 'J (l19S"- 13C) = 561 Hz structure 1: 6 - _a Y . s

2J (119Sn- 13C) = 32 Hz Structure 2: 26.3 27.5 26.5 13.5

3J (l19Sn - 13C) = 89 Hz

bipyramidal geometry. Vahtes20 for similar five-coor- dinated Bu,Sn(IV) complexes have been reported in the range of S - 128 to - 165 ppm.

On the basis of the foregoing spectral evidences, tlte following geometry (Fig. 2) may be assigned to these complexes:

Acknowledgements-We are thankful to Prof. T. N. Mitchell (W. Germany) for kindly recording the ‘C and “9Sa NMR spectra. Thanks are also due Dr. S. Dua-Bhabha Atomic Centre, Bombay recording the spectra. One us (A.S.)

thanks the New Delhi the award a Senior Fellowship.

REFERENCES

‘S. Kiischner, Y. K. Wei, D. Francis and J. G. Bergman, 1. Med Chem. 1966,9,369.

2S. E. Livingstone and M. Das, kit. J. Cancer 1978,37,466. ‘M. Das and S. E. Livingstone, Inorg. Chim. Acta 1976,19,5. ‘M. A Ali, S. E. Livingstone and D. J. Philips, Inotg. Chim. Acta 1971,5, 119.

‘A. Saxena, J. K. Koacher and J. P. Tandon, 1x0~ Nucl Chem. L.&t. 1981,17,229.

6A. Saxena, J. P. Tandon, K. C. Molloy and J. J. Zuckerman, Inooo. Chim. Acta 1982.63.71.

‘M. A. Ah, S. E. Livin&ne~and D. J. Philips, Inorg. Chim. Acta 1973.7. 179.

*S. A. Pardiej, S. &pinathan and C. Gopinathan, Ind. L Chem., Sect. A, 1980,19,130.

9M. A. Ali and S. E. Livingstone, Coonl. Chum. Reo. 1974, 13, 101.

“A Saxena. J. K. Koacher and I. P. Tandon, J Jnorg Nucl. CiienL 1981,43,3091.

“M. A. Ali and R. Bose, 1. Inorg. Nucl Chem. 1977,39,265. ‘*M. A. Ali, S. E. Livingstone and D. J. Philips, Inorg Chim.

Acta, 1972,6, 11.

446 A. SAXENA and J. P. TANDGN

“R. H. Helm, G. V. Everett, Jr. and A. Chakravorty, Prog. Znorg. “J. M. Femandezg, E. Cortes and J. G. Larra, I. Znorg. Nucl. Chem. 1966,7, 161. Chim. 1975,37, 1385.

14W D Honnick and J. J. Zuckerman, J. Organomef. Chem. 1979, 178, i33.

‘sG Domazetis, R. J. Magee and B. D. James, Z. Organomet. hem. 1978,148,339.

“J. K. Terlouw, W. Heerma, P. C. M. Frintrop, G. Dijkstra and ‘9. N. Mitchell, 1. Orgenomer. C/tern. 1974,71,39. H. A. Meinema, J. Organomer. Chem. 1974,64,205. *‘A G. Davies, P. G. Harrison, J. D. Kennedy, R. I. Puddephatt,

16D B Chambers and F. Glocking, Znorg. Chimica, Ado. 1970,4, 150..

T: N. Mitchell and W. McFarlane, /. Chem. Sot. C, 1136 (1%9).