a-Naphthylamine dithiocarbamate and its complexes with
Co(II), Ni(U), Cu(II), Ru(III) , Rh(III), Pd(II), Pt(IV), Zn(II), Cd(II)
and Hg(II) have been prepared and characterized by chemical
analysis, IR - and reflectance spectral studies and magnetic
susceptibili ty measurements. In all these complexes the dithiocarbamato
moiety acts as a chelate. The Ni(II), Cu(II) and Pd(Il)
complexes have been found to be square planar while those of
Ru(III), Rh(III) and Pt(IV) were proposed to be octahedral in
nature. The Co(II) ion seems to have a tetrahedral geometry, unlike
the other known square planar dithiocarbamato complexes of
Co(II). No definite structure, however, could be proposed for Zn(II),
Cd(II) and Hg(II) on the basis of limited studies

K. S. Siddiqi

M. R. H. Siddiqi

Parveen Khan

S. A . A . Zaidi

Saleem Khan

English

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CROATICA CHEMICA ACTA CCACAA 55 (3) 271-276 (1982) CCA-1329 YU ISSN 0011-1643 UDC 546.4/.5.,546.7 Original Scientific Paper Transition Metal Complexes of a-Naphthylamine Dithiocarbamate K. S. Siddiqi*, Parveen Khan, Saleem Khan~ M. R. H. Siddiqi, and S. A . A . Zaidi Division of Inorganic Chemistry, Department of Chemistry, ALigarh Muslim University, ALigarh, India Receiv ed July 20, 1981 a-Naphthylamine dithiocarbamate and its complexes with Co(II), Ni(U), Cu(II), Ru(III) , Rh(III), Pd(II), Pt(IV), Zn(II), Cd(II) and Hg(II) have been prepared and characterized by chemical analysis, IR - and reflectance spectral studies and magnetic susceptibili ty measurements. In all these complexes the dithio-carbamato moiety acts as a chelate. The Ni(II), Cu(II) and Pd(Il) complexes have been found to be square planar while those of Ru(III), Rh(III) and Pt(IV) were proposed to be octahedral in nature. The Co(II) ion seems to have a tetrahedral geometry, unlike the other known square planar dithiocarbamato complexes of Co(II). No definite structure, however, could be proposed for Zn(II), Cd(II) and Hg(II) on the basis of limited studies. During the last two decades interest has been invoked in the study of dithiocarbamate complexes of transition metal ions1- 5 and group IV metal halides6- 8, particularly owing to their dual behaviour of acting both as a unidentate ligand and a chelating agent. In our ea'rlier communications, we have reported on the symmetrical and unsymmetrical n ature of dithiocarba-mato groups. In this paper we are reporting on the study of transition metals with __a-hit-herto unknown a-naphthylamine dithiocarbamate. EXPERIMENTAL a-Naphthylamine (B.D.H.) melting at 50 °c was recrystallised from ethyl alcohol. The solvents were purified by conventional methods. Carbon disulphide and sodium hydroxide used were also B.D.H. reagents. Chloroplatinic acid, palladium(II) chloride, ruthenium(III) chloride (Johnson-Matthey), rhodium(III) chloride (Koch--Light) and other metal chlorides (B.D.H. A.R. grade) were used as such. The IR spectra (4000-200 cm-1) were run on a Perkin Elmer 651 spectrophoto-meter. The diffuse reflectance spectra were recorded on a Carl-Zeiss VSU-2P spectrophotometer using MgO as calibrant. The magnetic susceptibility measurements were done by the Faraday's Method. Molecular susceptibilities were corrected for diamagnetism of the component atoms by use of the Pascal's constants. Elemental analyses were done by the usual microanalytical techniques. Synthesis of Sodium a -N aphthyiamine Dithiocarbamate [( a-NHdtc)' Na] a-Naphthylamine, carbon disulphide and sodium hydroxide were taken in 1 : 1 : 1 molar ratios respectively. To an ethanolic solution of a-naphthylamine, carbon disulphide and sodium hydroxide were added with continuous stirring. On 272 K. S. SIDDIQI ET AL. completion of this reaction a light violet crystalline solid melting at 290 °C, was obtained (yield = 800/o). It was soluble in DMF and DMSO. Preparation of Complexes with Transition Metal Chlorides The metal dithiocarbamate may be synthesized by one of the following methods. (i) By direct insertion of a -CS2 group in the presence of an amine and the metal chloride (MCh or MCb) 2 RHNH + 2 CS2 + MCl2 ~ (RHNCS2)2 M + 2 HCl (ii) By a replacement reaction using the sodium salt of the dithiocarbamate 2 (RHNCS2) Na + MCh ~ (RHNCS2)2 M + 2 NaCl In the present case the complexes of a-naphthylamine dithiocarbamate were synthesized by the first method. To a mixture of metal chloride in alcohol and carbon disulphide, a solution of a-naphthylamine in the same solvent (in 1 : 2 : 2 or 1 : 3: 3 molar ratio) was added dropwise. The reaction mixture was stirred for one hour, heated on a water bath for fifteen minutes and then kept overnight. The solid thus obtained was filtered, washed with excess of hot alcohol and dried in vacuum. RESULTS AND DISCUSSION The analytical results of the complexes, their colour and melting points are given i:n Table I. Complexes of the type M(a-NHdtc)iC10_ 2 have been isolated where, M = Co(II), Ni(II), Cu(II), Rh(III), Pd(II), Pt(IV), Zn(II) , Cd(II) and Hg(II). According to Chatt and coworkers9 the IR spectra of alkyl dithiocarbamates should exhibit a strong band between 1480 to 1550 cm-1 assigned to polar 8 2 C-'-'-~N stretching frequency. This frequency lies intermediate to those associated with the C-N single bond (1250-1350 cm-1) and C=N double bond (1640-1690 cm-1) . The 8 2 C-;..!.-'-'-N stretching frequency in aryl dithiocar-bamates pave been found to lie below the range quoted by Chatt et aP, which may be due to the electron withdrawing nature of the aryl group3• In the present work the absorption bands observed between the 1370-1380 cm-1 region (Table II) have been assigned to v C-'-'--'-'-N which are consistent with that reported by Coucouvanis and his coworkers10• The bands between 1010 cm-1 and 1020 cm-1 (Table II) have been assigned to the (C~ '.: 8) stretching modes3. This v (C~:: S) band also seems to have partial double bond character as it falls between a C-8 single bond (600-800 cm-1), aind a C = 8 double bond (1050-1200 cm-1) . A comparison of the far IR spectra of a-naphthylamine dithiocarbarnate and its complexes showed some additional bands besides the usual group frequencies which are essentially due to metal-sulphur and metal-halogen bonds (Table II). Most dithiocarbamato Co(II) complexes are square planar with the magnetic moment value ranging from 1.60 to 2.5 ,u8 3- 4 . The magnetic moment value of - 4.79 µ 8 dark green colour and the electronic spectral band are the characteristics of a tetrahedral Co(II) complex with sulphur donors1J . In our green Co(a-NHdtc)i complex (µ cff = 4.69 µ 8 ) only one absorption band is also indicative of a tetrahedral cobalt (II) ion. For a tetrahedral Co(II} complex with sulphur donors the 11 (Co - S) falls in the 388- 390 cm-1 region12 while for a square planar cobalt(II) dithiocarbamate complex4, it has been noted at 360 cm-1. The v (Co - S) TABLE I Analytical Data and Other Physical Properties of a-Naphthylamine Dithiocarbama,te Complexes M. P. Calcd. Calcd. Calcd. Calcd. Calcd. Calcd. Complexes Colour oc O/oC 0 /oH 0ioN O/oS 0 /oCl O/oM (Obs) (Obs) (Obs) (Obs) (Obs) (Obs) a.-NHdtc · Na Light violet 290 54.77 3.31 5.80. 26.55 (54.91) (3.29) (5.78) (26.70) Co(a.-NHdtc)2 Black 280'' 53.12 3.62 5.63 25.75 -11.85 (53.19) (3.69) (5.68) (25.82) -(11.91) >-3 ~ > Ni(a-NHdtc)2 Dark green 220 53.14 3.62 5.64 25.76 -11.81 z rJl (53.31) (3.64) (5.71) (25.07) -(11.61) H >-3 H Cu(a.-NHdtc)2 Black 250 52.63 3.58 5.58 25.54 -12.52 0 z (52.72) (3.64) (5.69) (25.69) -(12.69) ;;s: Ru(a.-NHdtc)2Cl Black 250 45.94 3.13 4.87 ~2.27 6.17 t"1 ->-3 (46.21) (3.14) (4.89) (22.35) (6.05) -> t"' Rh(a.-NHdtc)3 Dark brown 250 52.11 3.55 5.52 25.26 --n 0 (51.34) (3.56) (5.55) (25.51) ---;;s: '1J Pd(a.-NHdtc)2 Yellow 245 48.49 3.30 5.14 23.51 --t"' t"1 (48.64) (3.32) (5.18) (23.59) --· ~ t"1 Pt(a.-NHdtc)2Ch Black 250 37.49 2.55 3.97 18.17 10.08 rJl (37.77) (2.57) (3.91) (18.29) (10.21) Zn(a.-NHdtc)2 Grey 210 52.44 1.57 5.56 25.42 (53.55) (1.58) (5.68) (25.91) Cd(a.-NHdtc)2 Pale yellow 220d 47.96 3.27 5.08 23.25 (48.86) (3.29) (5.17) (23.38) Hg(a-NHdtc)2 Grey 280 41.34 2.81 4;33 20.04 (40.31) (2.78) (4.42) (19.18) to.:> d decomposition temperature -J w 274 K. S. SIDDIQI ET AL. TABLE II IR Spectra (4000-200 cm-1) of a-Naphthylamine Dithiocarbamato Complexes and Their Assignments Complexes v (C==N) v (C==s) v (M-S) v (M--Cl) cm-1 cm-1 cm-1 cm-1 a-NHdtc ·Na 1370vs 1010vs Co(a-NHdtc)2 1370s 1010vs 375m Ni(a-NHdtch 1375s 1005vs 390m 325w Cu(a-NHdtc)2 1370s 1010s 365s 325m Ru(a-NHdtc)2Cl 1380s 1010vs 340m 325m 315m Rh(a-NHdtc)a 1370s 1010vs 330s Pd(a-NHdte)2 1370s 1009vs 340s Pt(a-NHdtc)2Cl2 1370s 1009vs 380m 320m Zn(a-NHdtch 1370s 1002s 330m Cd(a-NHdtc)2 1380s 1020m 330m Hg(a-NHdtc)2 1380s 1020m 325s vs = very strong; s =strong; m = medium; w = \veak TABLE III Magnetic Measurement and Electronic Spectra of a-NaphthyLamine Dithiocarbama.to Complexes band Complexes µeff position Assignment µ13 cm-1 Co(a-NHdtc)2 4.69 14,705 4T1g (P) -<- 4A2,,; Ni(a-NHdtc)2 D 24,390 Charge transfer 17,500 lB3g +---- IAtg 15,810 1B1g +---- 1A1g Cu(a-NHdtc)2 1.89 25,641 Charge transfer 23,000 2A1g +---- 2Btg 17,241 2Eg· +---- 2Btg Pd(a-NHdtc)2 D 27,030 Charge transfer 21,000 1B1g +---- 1 A1 ~; Rh(a-NHdtc)s D 25,641 1T1g +---- 1A1;;· 28,571 1T2g +---- 1A1,, Pt(a-NHdtc)2Ch D 27,777 lT1 g +----1 A1 g 24,390 1Ttg +---- 1A1;; 16,666 3T2g +---- 1 A1g D = diamagnetic TRANSITION METAL COMPLEXES 275 observed at 375 cm-1 in this case also supports a tetrahedral geometry for the Co(II) ion. The complex, [Ni(a-NHdtc)i] and its pyridine adduct were reported by Kaul and Pandeya'~ during the course of this \'rnrk and it is intereshng to note that the results of this work are almost the same as reported by them. The magnetic moment values and the electronic spectral data (Table III) for Ni(II), Cu(II) and Pd(II) bis (a-naphthylamine dithiocarbamate) are in accordance with other reported squ are-planar complexes5. The diamagnetism of Rh(III) and Pt(IV) is common for octahedral envir-onment5,14 but the diamagnetic behaviour of Ru(III) is naturally unusual. The spin pairing in this case may be explained by the overlap of suitable metal orbitals yielding in o or !>. bond formation if the metal ions are very close to each other (as in the case of dimers) or due to the formation of extended molecular orbitals by the extended overlap of the metal and chloride orbitals. It is, of course difficult to choose one of the above two possibilities when deciding on the geometry of the molecule, unless a thorough X-ray structure is determined. However, the diamagnetism can also be explained on the basis of electron interaction through the intervening anions, when there is chlorine bridging, which seems more plausible in the present case. This complex shows only charge transfer bands. This is in accordance v,:ith the reported diamagnetic Ru(III) complex1:;. As Zn(II), Cd(II) and Hg(II) have a d10 electronic configuration, no d-d transitions are expected in the reflectance spectra of their complexes. On the basis of limited studies no conclusive results pertaining to their geometries could be drawn. Acknowledgements. - The authors thank Prof. W. Rahman, Head of the De-partment of Chemistry, Aligarh Muslim University, Aligarh, for providing labora-tory facilities and Prof. R. C. Aggarwal (BHU) for magnetic measurements. Two of us (P. K. and S. IC.) are thankful to CSIR for financial assistance. REFERENCES 1. K. s. s id di qi, P . Khan, N. Singh al, and s. A. A. Zaidi, Indian J. Chem. A19 (1980) 265. 2. K. s. s id di qi, P. Khan, N. Singh al, and S. A. A. Zaidi, Bull. Soc. Chim. France 7-8. (1980) I-303. 3. G. Marco trig i an o, G. C. Pe 11 a can i, and C. Pr et i, J. InoTg. Nucl. Chem. 36 (1974) 3709. 4. C. Preti and G. Tosi, J. Inorg. Nucl. Ch.em. 38 (1976) 1746. 5. G. Marco trig i an o, G. C. Pel 1 a can i , C. Preti, and G. To s i, Bul l. Chem. Soc. Japan, 48 (1975) 1018. 6. S. A. A. Zaidi, K. S. Siddiqi, and N. I s l am, Indian J. Chem. 12 (1974) llfl'I. 7. S. A. A. Zaidi, T. A. Khan, and N. S. Neel am, Indian J. Ch.em. 17A (1979) 419. 8. K. S. Siddiqi, F. R. Zaidi, and S. A. A. Zaidi, Synth. Inorg. Met-Org. Ch.em. 10(6) (1980) 569. 9. J. Ch at t, L. A. Duncanson, anc! L. :iVL Ven an z i, Soumen Kemi B2!J (1956) 75. 10. D. Co u co u van is and J . F. Fack 1 er, Jr., Inorg. Chem. 6 (1967) 2047. 11. P. P. Singh and A. K. Srivastava, Aust. J. Chem. 27 (1974) 509. 12. F. A. Cotton, D. M. L. Good game, and M. Good game, J. Amer. Chem. Soc. 83 (1961) ·1690. 276 K. S. SIDDIQI ET AL. 13. B. B. Ka u 1 and K. B. Pandey a, J. Inorg. Nucl. Chem. 40 (1978) 229. 14. Car 1 J. Ba 11 ha use n, Introduction to Ligand field theory McGraw-Hill Book Company, Inc., New York, p. 277, 283 (1962). 15. M. R. Gajendragad and U. Agarwala, J. Inorg. Nucl. Chem. 37 (l!J10; 2429. SAZETAK Kompleksi a-naftilamin-ditiokarbamata s prijelaznim metalima K. S. Siddiqi, Parveen Khan, Saleem Khan, M. R. H. Siddiqi i S. A. A . Zaidi Pripravljeni su kompleksi a-naftilamin-ditiokarbamata sa Co(TI), Ni(II), Cu(II), Ru(III), Rh(III), Pd(II), Pt(IV) , Zn(II) , Cd(II) i Hg(II) i karakterizirani elementnom analizom, spektrima refleksije i IR-apsorpcije te mjerenjima magnetske suscepti-bilnosti. U svima ispitanim spojevima ditiokarbamatna skupina djeluje kao kelira-juce mjesto. Koordinacija je u kompleksima Ni(ll), Cu(II) i Pd(II) kvadratno-pla-narna, a u kompleksima Ru(llI) , Rh(III) i Pt(IV) je oktaedarska ; Co(Il) pa k koordi-nira se vjerojatno tetraedarski. Nije bilo moguce predloziti tip strukture za komplekse Zn(II) , Cd(Il) i Hg(II). 

Transition Metal Complexes of a-Naphthylamine Dithiocarbamate

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