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Inorganic Chemistry Communications 10 (2007) 139–142

First X-ray crystal structure of cation [cis-Co(en)2(H2O)Cl]2+:Synthesis, spectroscopic and X-ray structural study of

[cis-Co(en)2(H2O)Cl](C6H5SO3)2ÆH2O

Rajni Sharma a, Raj Pal Sharma a,*, Konstantin Karaghiosoff b, Thomas M. Klapoetke *,b

a Department of Chemistry, Panjab University, Chandigarh 160014, Indiab Department of Chemistry and Biochemistry, Ludwig-Maximilians-University, Munich, Butenandtstrasse, Germany

Received 13 August 2006; accepted 14 September 2006Available online 1 October 2006

Abstract

A new cobalt(III) complex salt, [cis-Co(en)2(H2O)Cl](C6H5SO3)2 Æ H2O] (I) has been synthesized and characterized by single crystal X-ray structure determination and NMR spectroscopy. This is a first report of the cobalt(III) cation in cis-configuration. The crystal latticeof the complex salt is stabilized by electrostatic forces of attraction and hydrogen bonding interactions.� 2006 Elsevier B.V. All rights reserved.

Keywords: Cobalt(III); Coordination chemistry; Benzenesulphonate; X-ray crystallography; IR spectroscopy; UV/visible spectroscopy

Both the cis and trans isomers of salts containing[Co(en)2(H2O)Cl] are known in the literature [1,2]. Thesalt [cis-Co(en)2(H2O)Cl]Cl2 results from the hydrolysisof [trans-Co(en)2Cl2]Cl which gave the correspondingsalt [cis-Co(en)2(H2O)Cl]SO4Æ2H2O upon addition of(NH4)2SO4 [1]. The sulphate salt is converted to bromidesalt when reacted with hydrobromic acid. The other isomer[trans-Co(en)2(H2O)Cl]S2O4 has been isolated as a dithio-nate salt from the reaction of [Co(en)2CO3]Cl2 and HCl.Although the X-ray structure of trans isomer of cation in[trans-Co(en)2(H2O)Cl]H2S3P2O6 Æ H2O is reported [2] butthere is no report regarding the structure of cis isomeri.e., ½cis-CoðenÞ2ðH2OÞCl�2þ, to the best of our knowledge.This paper reports the synthesis, and characterization of[cis-Co(en)2(H2O)Cl](C6H5SO3)2ÆH2O [3] in continuationof our interest in cobalt(III) salts [4–7]. A single-crystalX-ray structure determination of this is also described here[8] to unambiguously establish the structure of cis-cation inthe newly synthesized salt which was unexpectedly

1387-7003/$ - see front matter � 2006 Elsevier B.V. All rights reserved.

doi:10.1016/j.inoche.2006.09.014

* Corresponding author. Tel. +91 172 253 4433.E-mail address: rpsharmapu@yahoo.co.in (R.P. Sharma).

obtained from the reaction to prepare a simple salt replac-ing chloride ligands by benzenesulphonates (Scheme 1).

Both cis- and trans-[Co(en)2Cl2]+ salts are known toundergo hydrolysis upon heating to give chloro-aquo saltscontaining the cation [cis-Co(en)2(H2O)Cl]2+ [1,9,10] as:

[trans-Co(en)2Cl2]þ+ H2O! [cis-Co(en)2(H2O)Cl]2þ+ Cl�

In our opinion, for the title complex salt, the driving forceis the tendency of ‘‘Co(en)2’’ moiety to reorient so that theanions can interact via H-bonding with two hydrogens oftwo different N–H groups from two different ethylenedia-mine groups in cis position thereby giving rise to a morestable structure. This is similar to the conformationalchange of crown ethers under the influence of approachingmetal ion.

The solution state electronic spectrum of newly synthe-sized salt (I) in water shows absorptions at 513 and374 nm. The solution state UV/visible spectrum of a similarcomplex cation, i.e., [cis-Co(en)2(H2O)Cl]2+, shows absorp-tions at 516 nm and 375 nm [11]. The two spectra are fairlyidentical. The UV/visible absorption spectrum of complexsalt (I) has also been recorded in methanol. These spectra

trans-[Co(en) 2(C6H5SO3)2]C6H5SO3

(Expected) [trans-Co(en) 2Cl2]Cl + 3NaC6H5SO3

[cis-Co(en)2(H2O)Cl](C6H5SO3)2

(Unexpected)

Scheme 1.

a

b

Abs

Wavelength

0.8

0.6

0.4

0.2

200 400 600 800

Fig. 1. UV/visible spectra (wavelength vs absorbance) of [cis-Co(en)2-(H2O)Cl]2+ in: (a) H2O (374 nm and 513 nm) and (b) methanol (373 nmand 509 nm).

Fig. 2. Molecular diagram (ball and stick model) and atom nu

140 R. Sharma et al. / Inorganic Chemistry Communications 10 (2007) 139–142

of cationic salt in two different solvents are compared inFig. 1 showing kmax at nearly the same values. This showedthat the complex cation is stable in these two solvents. Themolar extinction coefficients (emax) of 0.01 molar solution ofthe complex salt in water and methanol were found to be 70and 64 respectively, indicating solvent dependence.

To distinguish between cis and trans isomers, the NMRspectra of ethylenediamine cobalt(III) complexes in deute-rium oxide is very diagnostic: the nitrogen protons show dif-ferent number of signals depending on geometry of complex[12]. The cis-bisethylenediaminecobalt(III) complex has mul-tiple peaks attributed to nitrogen protons, while the trans iso-mer shows single peak due to nitrogen protons. Also theabsorption of the trans isomer is at field strength in betweenthose of the absorptions of the isomeric cis complex.

NMR spectrum of the complex salt was recorded inD2O. The chemical shift values are expressed as d value

mbering scheme of [cis-Co(en)2(H2O)Cl](C6H5SO3)2 Æ H2O.

Fig. 3. Packing diagram of [cis-Co(en)2(H2O)Cl](C6H5SO3)2 Æ H2O showing H-bonding interactions of oxygens of benzene sulphonate with hydrogens ofNH (en).

R. Sharma et al. / Inorganic Chemistry Communications 10 (2007) 139–142 141

(ppm) downfield from tetramethylsilane as an internalstandard. In 1H NMR, the four signals at 4.1, 4.3, 5.4and 5.7 ppm are attributed to nitrogen protons of ethylene-diamine, characteristic of [cis-Co(en)2] group while CH2

protons of ethylenediamine [12] group are observed at2.0 ppm, thus confirming the cis geometry of the complex.The two signals at 7.0 and 7.3 ppm are attributed to theprotons of benzene ring, the two protons in the vicinityof SO�3 group and the three protons far from this grouprespectively. 13C NMR spectrum shows the characteristicsignal at 45.4 ppm for carbon atoms of ethylenediaminegroup. Signals at 149.5 129.1, 127.6, 124.1 ppm correspondto C1, C2,6, C3,5, C4 of the benzene ring [13] (where C1 is thecarbon attached to sulphonate group).

X-ray structure determination revealed that the cobaltatom is surrounded by four nitrogen atoms originating

Table 1Hydrogen bonding parameters for [cis-Co(en)2(H2O)Cl](C6H5SO3)2ÆH2O

D–H� � �A D–H H� � �A D� � �A D–H� � �AN(2)–H(12N)� � �O(4)c 1.0131 1.9255 2.919(5) 166.20N(3)– H(13N)� � �O(4) 1.0951 1.9116 2.979(5) 163.74N(4)– H(14N)� � �O(1)a 0.83(4) 2.23(4) 3.054(6) 172(4)O(7)–H(17O)� � �O(3)b 1.0509 1.6228 2.660(4) 168.25O(8)–H(18O)� � �O(5)d 0.75(6) 2.05(6) 2.784(4) 165(7)N(1)–H(21N)� � �O(3) 0.85(6) 2.37(6) 3.086(6) 142(5)N(2)–H(22N)� � �O(6) 1.0468 1.9656 2.920(6) 150.05N(3)–H(23N)� � �O(1)b 1.1188 1.9757 2.948(5) 143.05N(4)–H(24N)� � �O(8)c 0.83(5) 2.37(5) 3.070(6) 142(4)O(7)–H(27O)� � �O(2)a 0.9944 1.6979 2.629(4) 154.27Intra C(6)–H(6A)� � �O(6) 0.9498 2.4776 2.887(6) 105.98Intra C(8)–H(8A)� � �O(2) 0.9505 2.4749 2.880(6) 105.61C(13)–H(13A)� � �O(4) 0.9899 2.5111 3.434(7) 155.13C(13)–H(13B)� � �O(2) 0.9907 2.4907 3.355(7) 145.56C(14)–H(14B)� � �O(5)d 0.9903 2.4184 3.367(6) 160.23

Sym. Op.: a 3/2 � x,�1/2 + y, 1 � z; b 3/2 � x,1/2 + y, 1 � z; c x,�1 + y,z

and d 2 � x,y, 1 � z.

from two coordinated ethylenediamine ligands in cis posi-tion, one coordinated chloride ligand and one oxygen atomof coordinated water molecule as can be seen in Fig. 2. Inaddition one lattice water molecule is also present per asym-metric unit. The crystal lattice of complex is stabilized byextensive intermolecular H-bonds of ethylenediamineligands with the oxygen atoms of the sulphonate group aswell as O–H(water)� � �O(sulphonate) (see Fig. 3). It was foundthat the trans angles are\Cl1Co1N3 = 177.0�,\N1Co1N4 =177.1 and \OCo1N2 = 176.6� and that cis angles are\N3Co1N2 = 91.5�, \N2Co1N1 = 86.0�, \Cl1Co1H =89.4�, \N1Co1Cl1 = 91.5�, \OCo1N4 = 89.7�, \N4Co1-N3 = 85.8�. This revealed that the octahedral geometryaround cobalt atom is slightly distorted octahedral. Twobenzenesulphonate anions are present separately as count-eranions but are involved in H-bonding interactions whichplay crucial role in stabilization of this chloro-aquocation in cis geometry. H-bonding parameters are given inTable 1.

In conclusion, a newly obtained ionic salt [cis-Co(en)2-(H2O)Cl](C6H5SO3)2 Æ H2O] has been isolated and charac-terized for the first time. Single crystal X-ray structuredetermination revealed the presence of the cation [cis-Co(en)2(H2O)Cl]2+ which is stabilized by hydrogen bond-ing interactions with two benzene sulphonate anions apartfrom lattice water which undoubtedly is also important incontributing to the overall stability of crystal lattice. Thisis a first structural report confirming the existence of a sta-ble salt containing this cation.

Appendix A. Supplementary material

Supplementary data associated with this article can befound, in the online version, at doi:10.1016/j.inoche.2006.09.014.

142 R. Sharma et al. / Inorganic Chemistry Communications 10 (2007) 139–142

References

[1] J.M. Vaught, R.D. Lindholm, Inorg. Synth. 9 (1967) 163.[2] V. Janickis, K. Marøy, Acta Chem. Scand. 48 (1994) 465.[3] Synthesis of the title compound: One gram (0.003 mol) of trans-

[Co(en)2Cl2]Cl was dissolved in 25 ml hot water and filtered. Inanother beaker 1.9037 g (0.01 mol) of sodium salt of benzenesul-phonic acid was dissolved in minimum amount of hot water (5 ml).Both the solutions were mixed slowly after cooling them to roomtemperature. The violet crystals appeared after 3–4 h, which werecollected by drawing off the mother liquor and air-dried(yield = 75%). The newly synthesized complex salt is freely solublein water and methanol but insoluble in acetone, benzene, andchloroform. The complex salt decomposes at 180 �C. Anal. Calcd. forCo(en)2(H2O)Cl](C6H5SO3)2 Æ H2O: Co, 10.6%; C, 33.9%; H, 5.31%;N, 9.9%. Found: Co, 10.4%; C, 34.2%; H, 5.5%; N, 10.1%. Solubility:0.7 g/100 ml at 25�C, Ksp = 1 · 10�4. FT IR (KBr pellet): (CH2)rocking 822, dasNH2 1570, masð–SO�3 Þ 1195 cm�1, msð–SO�3 Þ1128 cm�1, dasð–SO�3 Þ 565 cm�1 and m(C–S) 686 cm�1 which arecomparable with literature values [14,15]. Electronic spectrum (inH2O): kmax 513, 374 nm corresponding to d–d transitions typical foroctahedral low spin cobalt(III) salts [16].

[4] R.P. Sharma, R. Bala, R. Sharma, P. Venugopalan, Cryst. Eng.Commun. 8 (2006) 215.

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[8] Crystal data for the title compound: [cis-Co(en)2(H2O)Cl](C6H5-SO3)2 Æ H2O] , Space group is monoclinic, C2 with a = 27.916(4) A,b = 6.3246(9) A, c = 14.761(2) A, b = 120.284(3)�, V = 2250.5(6) A3,

Z = 2, Dc = 1.641 Mg/m3, l = 1.1 mm�1, R (for reflections withI > 2r(I)) = 0.0331 wR2 (for all data) = 0.0562. Data were collected atroom temperature for a crystal with dimensions 0.15 · 0.20 ·0.40 mm at room temperature on a Bruker Smart Apex CCDdiffractometer fitted with graphite monochromatized Mo Ka,k = 0.71073 A, such that hmax was 28.02. The structures were solvedusing the SHELX-97 program [17] and refine by a full-matrix leastsquares procedure based on F2. Atom numbering scheme employed isshown in Fig. 2 which was drawn using the XtalGX [18]. Packingdiagram showing H-bonding interactions is shown in Fig. 3. Com-plete crystallographic data have been deposited at the CambridgeCrystallographic Data Centre (CCDC No. 616043) and may beobtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html.

[9] F.A. Cotton, G. Wilkinson, C. Murillo, M. Bochmann, AdvancedInorganic Chemistry, sixth ed., John Wiley & sons, 1988.

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Florencio, S. Martinez-Carrere, G. Blanco, Inorg. Chim. Acta 128(1987) 113.

[15] K. Nakamoto, Infrared and Raman Spectra of Inorganic andCoordination Compounds, fourth ed., John Wiley & Sons, NewYork, 1986.

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