Synthesis and Spectral Studies of Zirconium (IV) Complexes with Ligands Containing N and S Donor Atoms

 

Mallikarjun S Yadawe¹* and Sangamesh A Patil²

¹S.B.Arts and K. C. P. Science College Bijapur, Karnataka India.

²Department of Chemistry, Karnataka University Dharawad-3.

*Corresponding Author E-mail: mallikarjunyadawe82@gmail.com

ABSTRACT:

 

 

INTRODUCTION:

During past few years much information has been added to the literature on Zirconium (IV) ^1-10. However, only little information has been published on zirconium (IV) Schiff base complexes.^11-13 Kogan and coworkers⁵ have prepared adducts from zirconium tetrachloride and few bidentate Schiff bases. The complexes of zirconyl chloride with bidentate and tridentate Schiff bases have also been reported.^2,13,14 Macarovici et al;¹¹ have synthesized the hexacoordinated Schiff base complexes with zirconyl chloride and they have assigned dimeric structure containing no Zr=O bond in themon the basis of spectral and TG analysis. The theoretical promises show that,zr is capable of displaying coordination number ranging from four to eight.^15,16 However, it is noted that, in most of the complexes prepared in nonaqueous medium zirconium exhibits coordination number six.

 

A number of metal complexes of various transition metals with substituted triazole Schiff bases and oxozirconium (IV) complexes of thiocarbohydrazones have been reported from our laboratory.^17-19

 

It is evident from the literature that, there is no information on the zirconium (IV) complexes with Schiff bases derived from 3-substituted-4-amino-5-mercapto-1,2,4-triazole with glyoxal/ biacetyl/ benzyl.

 

Hence we wish to report the synthesis of new series of zirconium (IV) complexes with the following Schiff bases.

 

Figure 1. Structure of Schiff bases

 

Schiff base	R’	R
I	H	H
II	H	CH3
III	H	C2H5
IV	H	C3H7
V	CH3	H
VI	CH3	CH3
VII	CH3	C2H5
VIII	CH3	C3H7
IX	C6H5	H
X	C6H5	CH3
XI	C6H5	C2H5
XII	C6H5	C3H7

The conductance measurements were made on an elico-CM-82 conductivity bridge.

 

The PMR spectra of the ligands and their zirconium (IV) complexes in DMSO were recorded on a V-60 spectrometer using TMS as an internal reference.

Table – 1: Analytical and Molar Conductance Data of Zirconium (IV) Complexes of 3 – Substituted-4-amino-5-mercapto-1,2,4- triazole Schiff bases

Complex NO	Empirical formula	M% Calcd.        Obtd.	N% Calcd.        Obtd	S% Calcd.        Obtd	C1%        Calcd.        Obtd	Molar Conductance Ohm-1cm2mole-1
1	(C6H6N8S2)Zr(OH)2.Cl2	20.26          20.20	24.87          24.80	14.21          14.25	15.77          15.70	13.42
2	C8H10N8S2)Zr(OH)2.Cl2	19.07          19.09	23.42          23.38	13.38          13.35	14.84          14.85	14.92
3	C10H14N8S2)Zr(OH)2.Cl2	18.01          18.05	22.12          22.15	12.64          12.68	14.02          14.09	18.33
4	C12H18N8S2)Zr(OH)2.Cl2	17.07          17.10	20.96          20.90	11.98          11.86	13.29          13.33	19.85
5	C8H10N8S2)Zr(OH)2.Cl2	19.07          19.11	23.42          23.50	13.38          13.35	14.84          14.78	16.33
6	C10H14N8S2)Zr(OH)2.Cl2	18.01          18.08	22.12          22.15	12.64          12.60	14.02          14.10	23.19
7	C12H13N8S2)Zr(OH)2.Cl2	17.07          17.00	20.96          20.75	11.98          11.89	13.29          13.35	16.90
8	C14H22N8S2)Zr(OH)2.Cl2	16.22          16.30	19.92          19.84	11.38          11.40	12.62          12.70	24.65
9	C18H14N8S2)Zr(OH)2.Cl2	15.14          15.20	18.59          18.64	10.62          10.65	11.78          11.75	12.95
10	C20H18N8S2)Zr(OH)2.Cl2	14.47          14.52	17.77          17.80	10.15          10.13	11.26          11.22	11.96
11	C22H22N8S2)Zr(OH)2.Cl2	13.85          13.75	17.07          17.00	9.72            9.65	10.78          10.75	14.90
12	C24H26N8S2)Zr(OH)2.Cl2s	13.29          13.31	16.32          16.28	9.25            10.34	10.34          10.30	16.13

 

 

RESULTS AND DISCUSSION:

Stochiometry:

Zrocl₂----->Zr(OH)₂cl₂ + LH₂…methanol……….>Zr(OH)₂LH₂cl₂

Where, LH₂ is a ligand (I-XII)

These complexes are yellowish orange in colour and they are soluble to a limited extent in DMF and DMSO. The insolubilities of these complexes in nitrobenzene have slendered our efforts to determine the molecular weights.

 

The analytical data systematized in Table-1 indicate that, these complexes conform to the stochiometry of the type Zr(OH)₂LH₂.cl₂ where, LH₂ is a ligand(I-XII).

The conductance measurements in DMF are too low to account for any dissociation. Hence, these complexes may be regarded as non-electrolytes.

 

IR SPECTRA:

The present free ligands exist both in tautomeric thiol and thione forms. These ligands show a broad medium band in the region 3280-3130cm^-1 followed by a weak band around 2400 cm^-1 due to v(NH) and v(SH) vibrations. Thus, these ligands exhibit thiol-thione tautomerism. The high intensity bands around 1635 +_5cm^-1 are assigned to v(C=N) in view of the previous assignments.²² this observation renders proof for the presence of glyoxal, biacetyl and benzyl residue.

These ligands also exhibit a medium intensity band around 740 cm^-1 has been attributed to v(C=S).²³

 

In the zirconium(IV) complexes we observe the broad band of medium intensity in the region 3280-3130 cm^-1 followed by a weak broad band around 2400cm^-1 can be assigned to v(NH) and v(SH) vibrations. Thesecomplexes exhibit medium to high intensity bands in the region 1620-1615cm^-1. These can be attributed to the C=N stretching vibrations. Shifting of the band suggests the coordination of C=N groups of the ligands to the metal ion through nitrogen.

 

The band due to v(C=S) vibration appear around 740cm^-1 in all the Zr(IV) complexes. In the ligands this band has been located at 740cm^-1. The absence of shift in the v(C=S) is indicating the non-involvement of –S- in the coordination to the metal ion.

It has been established that, when a copound contains M=O moiety, its ir spectrum shows a narrow band in the region 1100-800 cm^-1 belonging to the M=O stretch,^24,25 whereas, a broad band in the same region show the presence of a polymeric M-O-M chain. Paul and coworkers²⁶ have assigned a strong band at 870 cm^-1 to the Zr=O stretch in zirconyl complexes. The absence of non-ligand band in the region 720-780 cm^-1 precludes the possibility of the complexes being ionic in nature. Patel and coworkers^27,28 have assigned a narrow intense band around 980 cm^-1 to the Zr=O stretch in DPSO complexes of zirconium. Taking into consideration of these observations and the comparative study of IR spectra of ligands and the complexes suggest that, these zr (IV) complexes do not show any band which can be attributed to Zr=O or Zr-O-Zr stretch in the region 1000-800cm^-1. The absence of this band and the presence of a new band around 1150 cm^-1 due to the v (Zr-OH) favor the formation of Zr(IV) complexes as Zr(OH)₂L.cl₂. As the zirconyl chloride octahydrate does not have Zr=O bond and has the structure[Zr₄(OH)₈(H₂O)₁₆]cl₈ as indicated by single crystal x-ray work.³⁰ Since, we have used the zirconyl chloride as the starting material for the synthesis of present zirconium(IV) complexes, which does not contain Zr=O bond is confirmed by the non-aqueous titrations of these Zr(IV) complexes with standard NaOH solution in methanol after dissolving in excess of 3N HCl; which indicates more reaction of complexes with3N HCl. This proves the absence of Zr=O bond in the present Zr (IV) complexes.

 

The previous literatre^31-33 suggests that, the metal ligand vibrations occur below 600 cm^-1. There are some reports, wherein, metal-ligand bands are located around 650 and 700 cm^-1.^34,35 Ueno and Martell³⁶ have ascribed medium intensity band around 615 and 419 cm^-1 to the metal ligand vibrations. In view of these assignments the medium intensity bands observed in the region 580-480 cm^-1 have been assigned to v (Zr-N) vibrations. Nakamoto and coworkers³⁷ in an extensive study of metal acetyl acetonates have observed pure metal oxygen bands in the region 500-400 cm^-1. We have assigned medium intensity bands occurring in the region 410-340 cm^-1 to the Zr-O stretching vibrations in view of previous assignments.³⁸ In addition to these bands, there are a few bands observed in the region 320-260 cm^-1 and these have been attributed to v (Zr-Cl) vibrations on the basis of previous assignments39-41. It is reported that, the M-X vibrations are sensitive to oxidation state and the coordination number of metal ion. It is evident from the table that, there is no considerable variation in the v (M-Cl) vibrations. Thus, it tent amounts to the conclusion that, in all these complexes metal maintains the same configuration and the oxidation state.

 

PMR SPECTRA:

The PMR spectral studies have been done for only two representative complexes namely complex No.1 and 9 along with their ligands.

 

In the PMR spectra of the complexes1 and 9, the resonance due to the NH proton of the ligands (13.63 and 13.60ppm) I and IX respectively are unaffected. This indicates thione form of the ligand and non-involvement of sulfur in the coordination with the metal ion.

 

The another characteristic resonance due to the azomethine proton in the complex of the ligand appears at 9.13ppm indicating the downfield shift with the corresponding ligand(8.2ppm) due to deshielding. This conformed the coordination of azomethine group to the metal ion through nitrogen. In the PMR spectrums of complex No.9, the complicated multiplet occur in the region 7.00-8.30ppm are due to the protons of phenyl ring of the ligand No. IX. This downfield shift of the aromatic proton signal with respect to the ligand IX (6.9-7.9 ppm) supprted the coordination of azomethine group to the metal ion through nitrogen.

 

The analytical data indicates 1:1stoichiometry for these complexes. IR and  PMR spectral studies suggest the involvement of both the C=N groups in the complex formation by keeping S-H groups away from the coordination, considering all these observations, we propose the following structure, in which zirconium exhibits coordination number of six.

 

Figure 2. Structure of metal complexes

 

ACKNOWLEDGEMENT:

The one of the authors (MSY) is grateful to UGC, New Delhi, for awarding Teacher fellowship and authors are also grateful to Principal and B. L. D. E. Association Bijapur for encouragement.

 

REFERENCES:

1.       Bhar and Thamiltz, A z.Anorg. allgem. Chem., 282, 3 (1955)

2.       kudryavestev A.S. and.Savich A.I, Zh.Vses, Khim. Obshestva in D.I.mendeleeva, 7,591 (1962); chem.. abstr.,58, 22121b, (1963).

3.       Savich A.I, pikav A.K. Lebedev., I.A and.Spytsyn, V.I Vestnik, Moskov, Univ.II ser. Mat. kelkh.Astron, Fix.Khim.1,225 (1956);Chem.Abstr., 51, 1134 3c (1957).

4.       Kudryavestev.A.S and.Savich, I.A Zh.Obshch.khim.,33,3763 (1963); Chem.Abstr.60,887 3a(1964).

5.       Kogan V.A,.Sokolov V.P  and.Osipov O.A Zh.Obshch. Khim.40, 332 (1970); Chem. Abstr., 73, 20968q, (1970).

6.       Orlova L.V,.Garnovskii A.D. Osipov, O.A  and.Kukushkina, I.I Zh.Obshch.Khim., 38, 1850 (1968); Chem. Abstr., 69, 113055q.

7.       P.prashar and Tandon, J.P. J.Less. Common Metals; 15 219 (1968); Chem. Abstr.,69, 794 1r (1968).

8.       Poddar and J.P.Tndon, Sci.cult. (culcutta); 34, 117 (1968).

9.       T.N.Matskevich,  E.P.traillina and I.A.Savich, Vestn.Mosk. Univ.Khim.,23, 31 (1968); Chem.Abstr., 69,113017d (1968).

10.     V.A.Kogan, V.R.Sokolov and O.A.Osipov, Russ.J. Inorg.chem.,13.,13,1195 (1968).

11.     C.G.Makarovici, E.Petris and E.Motiu, Rev.Roumain chim.,11, 53, 59 (1966).

12.     D.C.Bradley, M.B.husrthouse and I.F.Rendalf, J.Chem, Soc.,D,368(1970).

13.     N.S.Biradar and V.H.Kulkarni, Karn.Univ.J., 15,10,53,59 (1970).

14.     N.S.Biradar and A.L.Locker, Karn, Univ.,J.17,! (1972).

15.     W.B.blumenthal, The Chemical behavior of zirconium,D.Van. Nostrand co. Princeton (1968).

16.     F.A.Cotton and Wilkinson, Advanced Inorganic Chemistry, East-west private Ltd., New delhi,(1969).

17.     S.A.Patil, B.M.Badiger, S.M.Kudari and V.H.Kulkarni, J.Trans.Met.chem.,8,238 (1983).

18.     B.M.Badiger, S.A.Patil, S.M.Kudari and V.H.Kulkarni, Rev.roum.Chim.,31, 849 91986).

19.     S.A.Patil and V.H.Kulkarni, J.Less.common.Metals,106,89 (1985).

20.     M.S.Yadawe and S.A.Patil, Indian J.Hetero Chem., 2, 41 (1992).

21.     A.I.Vogel, Quantitative Inorganic Analysis, Longmans Green, London,!962.

22.     P.R.Shukle, V.K.Singh and J.Bhargava, J.Indian.Chem.Soc.,59, 620 (1082).

23.     R.V.Gadag and M.R.Gajendragad, Talanta, 25,418 (1978)

24.     Yuva kharilonov, L.I.Yuvanova, V.I.Plyustchev andV.G.Pervikh, Russ.J.Inorg, Chem.,399 (1965).

25.     C.G.Barraclough, I.Lewis and R.S.Nyholm, J.Chem.Soc.,3552, (1954).

26.     R.C.Paul, A.K.moudgil, S.L.Chadha and S.K.Vasist, Indian J. Chem.,8,1017 (1970).

27.     V.Krishnan and C.C.Patel, J.Inorg.Nucl.Chem.,26, 2201 (1964).

28.     V.V.Savant and C.C.Patel, J.Inorg.Nucl.Chem., 31, 2319 (1969).

29.     K.Nakamoto, ‘Infrared spectra of inorganic and coordination compounds’                Wiley-interscience,New York, 169 (1971).

30.     A.Clearfield and P.A.Vaughan, Acta.Crystallogr.,9, 555 (1966).

31.     A J.R.Durig, B.R.mitchell, D.W.Sink, J.R.Willer, and A.S.Wilson, Spectrochim,Acta.,23A, 1121 (1967). b J.R.Durig, R.Layton and D.W.Sink, Spectrochim.Acta.,21, 3157 (1965).

32.     D.M.Adams, Metal ligand and related v ibrations, Edward Arnold London 268  (1967).

33.     D.W.James and M.J.nolan, Progr.Inorg.Chem.,9, 195 (1968); Estd. By F.A.Cotton, Interscience,New York (1968).

34.     T.behnke and K.Nakamoto, Inorg.Chem.,6, 433 (1967).

35.     a K.Nakamoto and A.E.Martell, J.Chem. Phys., 32 588 (1960). b.K.Nakamoto, P.J.Mocarthy, A.Ruby and A.E.Martell, J.Am.Chem.Soc.,83, 1066 (1961) c.K.Nakamoto, P.J.Mokarthy and A.E.Martell, J.Am.Chem.Soc.,83,  1272 (1961).

36.     KUeno and A.E.martell, J,Phys.chem., 60, 1270 (1966).

37.     K.Nakamoto, IR and Raman Spectra of Inorganic and coordination compounds” John-Wiley,New York 213 (1978).

38.     R.C.Fay and T.J.Pinnavan, Inorg.Chem., 7, 508 (1968)

39.     J.A.Real, M.C.Manoz and J.Borras, Thermochem.Acta.,101, 83 (1968).

40.     J.A.Real and J.Borras, Synth.React.Met.Org.Chem., 14, 843, 657 (1984); 16, 13 (1986).

41.     P.W.Hunter and G.A.Webb,  J.Inorg.Nucl.Chem.,34 1511 (1972).

 

 

Received on 15.01.2010        Modified on 09.03.2010

Accepted on 02.04.2010       © AJRC All right reserved