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Journal of Organometallic Chemistry 696 (2012) 4202e4206

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Journal of Organometallic Chemistry

journal homepage: www.elsevier .com/locate/ jorganchem

Synthesis, spectral characterization and crystal structure of a novel trinucleardi-n-butyltin(IV) complex with pyruvic acid-N(4)-cyclohexylthiosemicarbazone(H2PACT)

M.A. Salam a, M.A. Affan a,*, Fasihuddin B. Ahmad a, I. Jusoh a, Mustaffa B. Shamsuddin b, Bohari Yamin c,Yang Farina c

a Faculty of Resource Science and Technology, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, MalaysiabDepartment of Chemistry, Universiti Teknology Malaysia, 81310 UTM, Skudai, Johor, Malaysiac School of Chemical Sciences and Food Technology, Universiti Kebangsaan Malaysia, 43600 UKM, Bangi, Selangor, Malaysia

a r t i c l e i n f o

Article history:Received 27 June 2011Received in revised form12 September 2011Accepted 17 September 2011

Keywords:Trinuclear di-n-butyltin(IV) complexPyruvic acid-N(4)-cyclohexylthiosemicarbazoneSpectral analysisCrystal structure

* Corresponding author. Tel.: þ60 82583042; fax: þE-mail addresses: salambpx@yahoo.com (M.A.

(M.A. Affan).

0022-328X/$ e see front matter � 2011 Elsevier B.V.doi:10.1016/j.jorganchem.2011.09.013

a b s t r a c t

A new trinuclear di-n-butyltin(IV) complex with pyruvic acid-N(4)-cyclohexylthiosemicarbazone(H2PACT) ligand was synthesized and characterized by elemental analyses, molar conductivity, UVeVis,FT-IR, 1H, 119Sn NMR spectroscopy and single crystal X-ray study. Single crystal X-ray diffraction datarevealed that this complex was trinuclear cyclic fashion with the pyruvic acid-N(4)-cyclo-hexylthiosemicarbazone ligand. In the trinuclear di-n-butyltin(IV) complex, the ligand (H2PACT) iscoordinated to the central tin(IV) atoms via the carboxylato-O, the azomethine-N and the thiolato-Satoms. The trinuclear tin system is formed by the bridges through the carbonyl oxygen atom of thecarboxylate moieties and making the tin atom of seven coordinated in distorted pentagonal bipyramidalgeometry. Single crystal X-ray data indicates that the complex (1) crystallized in cubic system with spacegroup I-43d, a ¼ b ¼ c ¼ 30.3273(17) Å, a ¼ b ¼ g ¼ 90�, Z ¼ 16, m(MoKa) ¼ 1.209 mm�1, F(000) ¼ 12,144,and final R1 ¼ 0.0390, wR2 ¼ 0.0843 for observed reflections 4582(I > 2s(I)).

� 2011 Elsevier B.V. All rights reserved.

1. Introduction

Thiosemicarbazones are thiourea derivatives and the studies ontheir structural and chemical properties have receivedmuch attentiondue to their biological (viz, antibacterial, antiviral and antitumor)activities [1,2]. Organotin(IV) complexes havebeenextensively studiedduring recent years mainly because of their potential biological activ-ities (viz, antiviral and antitumor) as well as their wide industrial andagricultural applications [3,4,5,6]. For the past few years, a largeamount of work on the synthesis and chracterization of transitionmetal complexes with thiosemicarbazone have been reported[7,8,9,10] but very little work has been reported on tin(IV) complexeswith substituted thiosemicarbazone ligands. The chemistry of poly-nuclear complexes containing tin or tin mixed with other metal ionshas been the subject of much interest in chelate systems [11,12,13].Recently organotin(IV) macrocycles are attracting more and moreattention for their potential industrial applications and biologicalactivities [14,15]. Xu Hao-long (2009) has reported the synthesis andcrystal structure of one trinuclear di-n-butyltin(IV) complex with

60 82583160.Salam), maaffan@yahoo.com

All rights reserved.

salicylaldoxime which suggested that the complex is displayingtwo unequivalent salicylaldoximate with one seven coordinatepentagonal bipyramidal tin atom linked two five coordinate trigonalbipyramidal tin atoms by SneOeSn bridges [16]. In our recentworks, we reported the X-ray structure analysis of pyruvic acid-N(4)-cyclohexylthiosemicarbazone ligand and its mono organotin(IV)complex [17,18]. As part of our continuous research work on organo-tin(IV) complexes of N(4)-substituted thiosemicarbazone ligands ouraimtoexploit theversatilityof coordinationbehaviouroforganotin(IV)derivatives with pyruvic acid-N(4)-cyclohexylthiosemicarbazoneligand. We obtained a trinuclear di-n-butyltin(IV) complex of pyruvicacid-N(4)-cyclohexylthiosemicarbazone. Herein, we report thesynthesis, spectroscopic characterization and crystal structure of tri-nuclear di-n-butyltin(IV) complex of pyruvic acid-N(4)-cyclohex-ylthiosemicarbazone.

2. Experimental

2.1. Materials and methods

All reagentswere purchased from Fluka, Aldrich and JT Baker. Allsolvents were purified according to standard procedures [19].

M.A. Salam et al. / Journal of Organometallic Chemistry 696 (2012) 4202e4206 4203

UVeVis spectra were recorded in CHCl3 solution with a PerkinElmer Lambda 25 UVeVisible spectrophotometer. Infrared spectrawere recorded on KBr discs using a Perkin Elmer Spectrum GXFourier-Transform spectrometer in the range 4000e370 cm�1 atroom temperature. 1H NMR and 119Sn NMR spectra were recordedon a JEOL 500 MHz-NMR spectrometer; chemical shifts were givenin ppm relative to SiMe4 and Me4Sn in CDCl3 solvent. CHN analyseswere obtained with a Flash EA 1112 series CHN elemental analyzer.Molar conductance value was measured with DMF solvent usinga Jenway 4510 conductivity meter. Crystals of trinuclear dibutylti-n(IV) complex were formed by slow evaporation of chloroform/methanol (1:1) solution suitable for X-ray analysis after 14 days atroom temperature. The structure was solved by direct methods andrefined by full-matrix least square on F2 using the SHELXL software.

2.2. Synthesis of pyruvic acid-N(4)-cyclohexylthiosemicarbazone(H2PACT)

Cyclohexylisothiocyanate (0.706 g, 5 mmol) and hydrazinehydrate (0.250 g, 5 mmol), each dissolved in 10 mL methanol weremixed with constant stirring. The stirring was continued for 30 minand the white product, N(4)-cyclohexylthiosemicarbazide formedwas washedwithmethanol and dried in vacuo over P2O5. A solutionof N(4)-cyclohexylthiosemicarbazide (0.51 g, 3 mmol) in 10 mLmethanol was treated with 10 mL methanolic solution of pyruvicacid (0.261 g, 3 mmol). The resulting reaction mixture was stirredand refluxed for 5 h. On cooling the solution to room temperaturewhite powder formed, filtered off and washed several times withmethanol. The white powder was recrystallised frommethanol anddried in vacuo over silica gel. Yield: 0.68 g, 87%: Mp.: 188e190 �C:UVevisible (CHCl3) lmax/nm: 327 : FT-IR (KBr disc, cm�1) nmax: 3322(br, OH), 3197 (s, NH), 2922, 2851 (s, cyclohexyl), 1692 (m, C]O),1619 (m, C]N), 980 (m, NeN), 1249, 873 (w, C]S). 1H NMR (CDCl3)d: 12.21 (s,1H, COOH), 9.49 (s,1H, N1eH), 8.08 (s,1H, CyC6eH), 2.21(s, 3H, N¼CeCH3), 2.05e2.03 (m, 10H, CyCeH), 1.8 (s, 1H, SH). Anal.Calc. for C10H17N3O2S: C, 49.36; H, 7.04; N, 17.26%. Found: C, 49.31;H, 7.01; N, 17.18%.

2.3. Synthesis of complex {Bu2Sn[PACT]}3 .4H2O (1)

Pyruvic acid-N(4)-cyclohexylthiosemicarbazone [H2PACT]ligand (0.243 g, 1.0 mmol) was dissolved in 10 mL of dry methanolin a Schlenk round bottom flask under purified dry nitrogenatmosphere. Then, 10 mL methanolic solution of dibutyltin(IV)dichloride (0.303 g, 1.0 mmol) was added drop wise to a solution of

Hydrazine hydrate

Cyc

Cyclohexylisothiocyanate

Scheme 1. Synthesis of pyruvic acid-N(4)-cyclo

ligand. The resulting reaction mixture was refluxed for 6 h (Scheme2) and cooled to room temperature. The solvent was graduallyremoved on a rotary evaporator under reduced pressure untila solid product was obtained. After filtration the solids were driedin vacuo over silica gel. The white solids were recrystallized frommethanol. The microcrystals were filtered, washed with a smallamount of cold methanol and dried in vacuo over silica gel. Col-ourless crystals suitable for X-ray were obtained by slow evapora-tion of chloroform/methanol (1:1) solutions after 14 days at roomtemperature. Yield: 0.41 g, 75%: Mp.: 208e210 �C Molar conduc-tance (DMF) U�1 cm2 mol�1: 8.3: UVevisible (CHCl3) lmax/nm: 260,328, 366: FT-IR (KBr disc, cm�1) nmax: 3393 (s, NH), 2926, 2853 (s,cyclohexyl), 1590 [m, nasy (COO�)], 1483 [m, nsym (COO�)], 1565 (m,C]N), 1010 (m, NeN), 1219, 827 (w, CeS), 685 (w, SneOeSn), 597(w, SneC), 583 (w, SneO), 492 (w, SneN). 1H NMR (CDCl3) d: 9.50 (s,1H, N1eH), 8.04 (s,1H, CyC6eH), 2.45 (s, 3H, N]CeCH3), 2.15e2.05(m, 10H, CyCeH), 2.04e2.03 (t, 2H, SneCH2eCH2eCH2eCH3),1.68e1.61 ( m, 2H SneCH2eCH2eCH2eCH3), 1.55e1.29 ( m, 2H,SneCH2eCH2eCH2eCH3), 0.88e0.85 (t, 3H, SneCH2eCH2e

CH2eCH3). 119Sn NMR (CDCl3) d: �446. Anal. Calc. for[C54H96N9O6S3Sn3].4H2O: C, 43.48; H, 6.49; N, 8.45%. Found: C,43.43; H, 6.44; N, 8.39%.

3. Results and discussion

Pyruvic acid-N(4)-cyclohexylthiosemicarbazone (H2PACT) wasprepared by the condensation reaction of pyruvic acid and4-cyclohexylthiosemicarbazide. The ligand is capable of existingeither as the thione form (I) or thiol form (II) (Scheme 1). Trinucleardi-n-butyltin(IV) complex was synthesized by reacting stoichio-metric amounts of nBu2SnCl2 and H2PACT in anhydrous methanol(Scheme 2). The physical properties and elemental analysis ofH2PACT and its trinuclear complex 1 are given in the experimentalsection. The complex 1 was stable under N2 atmosphere andsoluble in CHCl3, CH2Cl2, DMF, DMSO and MeCN solvents exceptmethanol, ethanol, hexane, pentane, THF and ether. The molarconductance values indicate that the complex 1 behave as nonelectrolytes [20].

3.1. UVeVisible spectra

Electronic spectra of the ligand H2PACT and its trinuclear di-n-butyltin(IV) complex 1were recorded from CHCl3 solution (10�4 M)at room temperature. The electronic absorption spectrum of ligandshowed only one band at 327 nmwhich correspond to the NHeC]

lohexylthiosemicarbazide

hexylthiosemicarbazone (H2PACT) ligand.

Sn

Dibutyltin(IV) dichloride

Sn

Sn

1

2

3

1

2

1

23

4

5 6

7

8

1

2

21

Refluxed, 6 h N2 Atmosphere

Abs. MeOH

12

3

45

61 2

3

78

Pyruvic acid-N(4)-cyclohexylthiosemicarbazone

Scheme 2. Synthesis of trinuclear di-n-butyltin(IV) complex 1.

M.A. Salam et al. / Journal of Organometallic Chemistry 696 (2012) 4202e42064204

S group in the ligand. After complexation, the complex 1 showedtwo new absorption bands at 260 and 366 nm, respectively. Theband at 260 nm, whichwas attributed to pep* of>C]O group. Theband at 366 nm is attributable to the thiomide nep* transition ofthe complexation of the thiolato of sulfur due to tautomerization,suggesting the ligand / metal (Sn) charge transfer (LMCT) band isoccured [21]. The shift of the lmax band from the ligand to thecomplex is a clear indication that coordination occurred betweentin(IV) and ligand (H2PACT).

3.2. IR spectra

The free ligand H2PACT showed absorption band at 3322 cm�1

which is due to the stretchingmode of theeOHgroup. A broad bandobserved in the IR spectrum of the free ligand at 3197 cm�1 attrib-uted to the NH moiety linked to the cyclohexyl group. The otherbands observed in the spectrum at 2922, 2851, 1692, 1619, 980 and1249, 873 cm�1 due to n(cyclohexyl), n(C]O), n(C]N), n(NeN), andn(C]S), respectively. For tin(IV) complex 1, the medium stretchingband at 3322 cm�1 correspond to theeOH group in the spectrum ofligand is disappeared in the spectrum of complex 1 due to thedeprotonation,indicates metal-ligand bond formation through thesite. The stretching and bending frequency of the n(CeS) bandobserved at 1249 and 873 cm�1 in the spectrum of the ligand areshifted to lower frequency at 1219 cm�1 and 827 cm�1 in the spec-trum of tin(IV) complex 1, indicating coordination of sulfur atom inthe thiolate form [22,23]. The (nCOOH) band observed at 1692 cm�1

in infrared spectrumof the free ligand,was absent in the IR spectrumof the complex 1. Two newabsorption bands were observed at 1590and 1483 cm�1 which attributed to nasy(COO�) and nsym(COO�),

respectively in the IR spectrum of the complex 1. The difference,D[nasy(COO�)� nsym(COO�)] for complex 1was found 107 cm�1 anditwas used to indicate the mode of tin carboxylate interaction. HereIR spectrum of the complex 1 give a separation value (Dn) less than200 cm�1, which indicates bidentate nature of carboxylate group[24]. Amediumbandat 1619 cm�1 assignable to n(C]N), is shifted tolower wave number at 1565 cm�1 in the spectrum of the complex 1,suggesting coordination of the azomethine nitrogen to the tinmoiety [25]. The stretching frequency is lowered owing to thedisplacementof electrondensity fromNtoSn atom, thus resulting inthe weakening of the C]N bond as reported in the literature [26].The n(NeN) band of the free ligand at 980 cm�1 is shifted to higherfrequencyat 1010 cm�1 in the spectrumof complex1, again confirmsthe coordination of azomethine nitrogen to the Sn(IV) atom. Char-acteristic two new bands at 685 and 583 cm�1 in the complex 1indicated that the presence of SneOeSn and SneO bond, respec-tively [27]. Another one new band at 492 cm�1 is characteristic ofSneN absorption. These observations have also been confirmed byX-ray single crystal structure analysis of complex 1.

3.3. 1H and 119Sn NMR spectra

The 1H NMR spectral assignments of ligand and its organotin(IV)complex 1 were carried out and interpreted based on the atomleveling inScheme2.1HNMRspectrumof free ligandH2PACTshowedresonance signals at 12.21, 9.49, 8.08, 2.21 and 1.8 ppm due to COOH,NH, CyC6eH,N]CeCH3 and SH, respectively. The resonance signal ofSH is not found in the spectrum of complex 1 which suggested thedeprotonation of the SH proton and confirming that the ligandcoordinated to the Sn(IV) in the thiolate form. The OH proton signal

Table 1Crystal data and structure refinement parameters for complex (1).

Compound 1

Empirical formula C54H96N9O6S3Sn3 4H2OFormula weight 1491.782Temperature (K) 298 (2)Wavelength (Å) 0.71073Crystal system CubicSpace group I�43dUnit cell dimensionsa (Å) 30.3273(17)b (Å) 30.3273(17)c (Å) 30.3273(17)a (�) 90.00b (�) 90.00g (�) 90.00

Volume (Å3) 27,893(3)Z 16Calculated density (mg/m3) 1.404Radiation type l (Å) MoKaF (000) 12,144Crystal size (mm) 0.50 � 0.49 � 0.41Crystal colour ColorlessScan range q (�) 1.64e25.98Absorption coefficient (m) (mm�1) 1.209Max. and min. transm 0.6370 and 0.5831Goodness-of-fit on F2 1.190Data/restrains/parameters 4582/4/263Final R indices [I > 2s(I)] R1 ¼ 0.0390, wR2 ¼ 0.0843R indices (all data) R1 ¼ 0.0540, wR2 ¼ 0.0998

M.A. Salam et al. / Journal of Organometallic Chemistry 696 (2012) 4202e4206 4205

was also absent in the complex 1 suggested deprotonation of thecarboxylic proton and the coordination is occured with tin(IV) atom.The resonance signal at 9.49 ppm is assigned to theN1eHproton andthe adjacent cyclohexyl proton CyC6eH shows a singlet at 8.08 ppmin the free ligand. After complexation, the N1eH proton signal isappeared in the downfield region at 9.50 ppm and CyC6eH protonsignal is also appeared in the upfield region at 8.04 ppm. The azo-methine proton (N]CeCH3) signal appears at 2.21 ppm in the freeligand which is shifted to downfield at 2.45 ppm in complex 1. Thisdownfield shift indicating the azomethine nitrogen atom is coordi-nated to tin (IV) atom. The cyclohexyl moiety forms a chair confor-mation and hence the protons exist in axial and equatorialenvironment. The equatorial protons are observed at a slightly higherchemical shift compared to that of the axial protons in the free ligandand complex 1. The two butyl groups attached to the organotin(IV)moiety in complex 1 gave four resonance signals namely,2.04e2.03 ppm (triplet, SneCH2eCH2eCH2eCH3), 1.68e1.61 ppm(multiplet, SneCH2eCH2eCH2eCH3), 155e1.29 ppm (multiplet,SneCH2eCH2eCH2eCH3) and 0.88e0.85 ppm (triplet,SneCH2eCH2eCH2eCH3). 1HNMR information also supported the IRdata of the complex 1.

119Sn NMR spectra can be used as an indicator of the coordi-nation number of the tin atom. In the trinuclear di-n-butyltin(IV),the signal of the 119Sn spectrum appeared at �446 ppm, suggestingthat the tin atom is seven-coordinate in the complex 1 [28,29]. Thisdata is confirmed by the X-ray diffraction studies in the complex 1.

3.4. X-ray crystallography diffraction analyses

Crystals suitable for X-ray investigation of the complex 1 wereobtained by slow evaporation from chloroform/methanol after 14days at room temperature. The complex 1 crystallized in cubicsystem with space group I-43d, a ¼ b ¼ c ¼ 30.3273(17) Å, Z ¼ 16and V ¼ 27,893(3) Å. The symmetrically generated moleculeshowed a trinuclear di-n-butyltin(IV) complex [Bu2Sn(PACT)]3,(Fig. 1) with four solvated water molecules. The main crystalparameters are reported in Table 1. Selected bond lengths and bondangles are given in Table 2. Each PACT ligand coordinated to thecentral tin(IV) atoms via the carboxylate oxygen, the azomethinenitrogen and the thiolato sulfur atoms. The trinuclear tin system isformed by the bridges through the carbonyl oxygen atoms of thecarboxylate moieties and making the geometry of the tin atoms ofdistorted pentagonal bipyramid. The coordinated N, S and O atomsare at the equatorial positions with subtended angle about the tinatom between 69.65(15)e132.99(44)�. The butyl groups occupy the

Fig. 1. Molecular structure of [Bu2Sn(PACT)]3. The hydrogen atoms and solvated watermolecules are omitted for clarity.

axial position with C11eSn1eC15 bond angle of 157.0(3)�. The C17and C18 atoms are disordered. The coordinated Sn1eO1, Sn1eN3,Sn1eS1 and Sn1eO2 bond lengths are 2.420(4) Å, 2.302(5) Å,2.5489(17) Å and, 2.335(4) Å, respectively. In the complex, threetin(IV) atoms are linked via a network of oxygen atoms bySneOeSn bridges. The bridging Sn1eO1 bond length is slightlylonger than Sn1eO2 bond length. The bridging oxygen atoms arecloser to the Sn atom. The Sn1eN3 bond length is 2.302(4) Å,slightly greater than the sum of the covalent radii of tin andnitrogen atoms (2.15 Å) but are considerably less than the van derWaals radii of the two atoms (3.75 Å), indicating strong SneNinteraction [30]. The SneN bond distance is in the accordance withthe values previously reported for coordinative bonds in sevencoordinated tin atom. The Sn1eS1 bond distance is 2.5489(17) Åwhich is close to the sum of covalent radii of SneS (2.42 Å) [31], butmuch shorter than the sum of the van der Waals radii (4.0 Å) [32].

Table 2Selected Bond lengths (Å) and angles (�) of complex 1.

Bond lengths (Å)Sn1eC11 2.124(6) N1eC7 1.320(8)Sn1eC15 2.129(6) N1eC6 1.462(8)Sn1eN3 2.302(5) N2eC7 1.323(8)Sn1eO2 2.335(4 N2eN3 1.360(6)Sn1eO1 2.420(4) N3eC8 1.294(8)Sn1eS1 2.5489(17) C1eC2 1.514(11)S1eC7 1.753(6) C1eC6 1.517(10)C9eO1 1.252(7) C8eC10 1.497(9)O2eC9 1.263(7) C8eC9 1.496(8)Bond angles (�)C11eSn1eC15 157.0(3) O2eSn1eO1 132.99(14)C11eSn1eN3 97.7(2) C11eSn1eS1 99.9(2)C15eSn1eN3 97.8(2) C15eSn1eS1 100.4(2)C11eSn1eO2 85.2(2) N3eSn1eS1 75.29(12)C15eSn1eO2 84.4(2) O2eSn1eS1 144.94(11)N3eSn1eO2 69.65(15) O1eSn1eS1 82.06(11)C11eSn1eO1 85.6(2) C7eS1eSn1 98.1(2)C15eSn1eO1 86.6(2) C9eO1eSn1 101.9(4)N3eSn1eO1 157.35(16) C9eO2eSn1 117.8(4)

Fig. 2. Molecular packing of [Bu2Sn(PACT)]3 viewed down the b-axis.

M.A. Salam et al. / Journal of Organometallic Chemistry 696 (2012) 4202e42064206

The value is also comparable to that reported in trimeric complex[Me3SnSCN4Ph]3 (2.56 Å) [33]. Thus, the Sn1eS1 bond formationwas through the thiolate anion. Th Sn1eO1 and Sn1eO2 bondlengths are 2.420(4) Å and 2.335(4) Å, respectively, which is slightlygreater than the sum of the covalent radii of tin and oxygen (2.10 Å)but are considerably less than the van der Waals radii of the twoatoms (2.8 Å), indicating tin-oxygen bond interaction. The asym-metric mode of the coordination of the carboxylate ligand is furtherconfirmed by unequal CeO band values 1.252(7) and 1.263(7). TheSn1eC15 and Sn1eC11 bond distances are 2.129(6) Å and2.124(6) Å, respectively, which are in agreement with previousreports [34,35]. The sum of the angles subtended at the tin atom inthe equatorial plane S1eSn1eN3 (75.29(12)�), N3eSn1eO2(69.65(15)�), S1eSn1eO1 (82.06(11)�), and O1eSn1eO2(132.99(44)�) is 359.99�, so atoms Sn1, O1, O2, N3 and S1 are in thesame plane. The axial positions are occupied by two butyl carbonatoms and the angle of the axial C11eSn1eC15 is 157.0(3)�, whichdeviates from the linear angle 180�. The N3eSn1eO1 angle157.35(16)� is comparatively similar to the correspondingC11eSn1eC15 angle, which also shows a significant distortion fromlinear angle. The distortion is partly due to the rigid framework ofthe ladder. On the other hand, the coordinated non-bridgingSn1eO2eC9 angle is slightly larger of 117.8(4)� is significantlymore than the Sn1eO1eC9 angle 101.9(4)�. The O1eSn1eO2 angleis 132.99(44)�, which deviates considerably from180�, indicated thestructure is distorted pentagonal bipyramidal. The crystal packingpattern of the complex 1 is shown in Fig. 2.

4. Conclusion

The ligand H2PACT and its new trinuclear di-n-butylyltin(IV)complex (1) were synthesized and fully characterized by variousspectroscopic techniques and X-ray crystallography. Based on theoutcome of characterization of the ligand (H2PACT) exists in thi-one form in a solid state but it takes on a thiol form when it is insolution. The X-ray crystallography analysis revealed that thecomplex 1 is trinuclear cyclic fashion with pyruvic acid-N(4)-cyclohexylthiosemicarbazone ligand and bridge by itscarboxylate-O atom to the another tin(IV) atom. The pentagonalbipyramidal geometry is of particular interest because geometryof such kind is less available in the literature from organotin(IV)compounds.

Acknowledgement

This work was financially supported by the Ministry of ScienceTechnology and Innovation (MOSTI) under a research grant (No. 06-01-09-SF0046). The authors would like to thank Universiti MalaysiaSarawak (UNIMAS) for the facilities to carry out the research work.The authors would also thank the Universiti Kebangsaan Malaysiafor the X-ray diffraction analysis.

Appendix. Supplementary data

Crystallographic data for structural analysis has been depositedwith the Cambridge Crystallographic Data center, CCDC referencenumber 823603 for compound [Bu2Sn(PACT)]3. These data can beobtained free of charge from The Cambridge Crystallographic DataCentre via www.ccdc.cam.ac.uk/data_request/cif.

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