Polyhedron 20 (2001) 2329–2337

Electrochemical synthesis, X-ray diffraction and spectroscopiccharacterisation of Co(II) compounds with

[(4-methylphenyl)sulfonyl]-1H-imino-2-phenyl-2-oxazolines

Jesus Castro a,*, Santiago Cabaleiro a, Paulo Perez-Lourido a, Jaime Romero b,Jose A. Garcıa-Vazquez b, Antonio Sousa b,*

a Departamento de Quımica Inorganica, Uni�ersidade de Vigo, 36200 Vigo, Galicia, Spainb Departamento de Quımica Inorganica, Uni�ersidade de Santiago de Compostela, 15706 Santiago, Galicia, Spain

Received 31 January 2001; accepted 23 April 2001

Abstract

The electrochemical oxidation of anodic cobalt in acetonitrile solutions of [(4-methylphenyl)sulfonyl]-1H-imino-2-phenyl-2-ox-azoline ligands, [HTs�ROz], affords compounds of general formula [Co(Ts�ROz)2]. All complexes have been characterised bymicroanalysis, IR and UV–Vis spectroscopy, magnetic measurements and, in the cases of HTs�4iPrOz, [Co(Ts�Oz)2],[Co(Ts�4MeOz)2], [Co(Ts�4iPrOz)2] and [Co(Ts�4EtOz)2], by single-crystal X-ray diffraction. © 2001 Elsevier Science Ltd. Allrights reserved.

Keywords: Electrochemical synthesis; Cobalt(II) complexes; Oxazolines; Sulfonamide complexes; X-ray structures

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1. Introduction

The coordination chemistry of metallic complexeswith amide ligands remains relatively unexplored, prob-ably due to the difficulty in replacing the amide hydro-gen atom by a metal [1]. However, in sulfonamides theelectron withdrawing effect of the sulfonyl group in-creases the acidity of the N�H group and, in thedeprotonated form, these anionic systems are effectivesigma-donor ligands. The coordination process is facili-tated by the presence of additional donor atoms on theligand, allowing the formation of stable five- or six-membered chelate rings with the metal ion. In this way,metal complexes of sulfonamide ligands incorporatingadditional donor atoms from iminomethyl and phenolgroups [2], iminomethyl and thiophenol groups [3] orpyridine groups [4–7] have been investigated recently.

As part of our continuing interest in the coordination

of sulfonamide ligands, in this paper we describe thesynthesis and characterisation of cobalt complexes with[(4-methylphenyl)sulfonyl]-1H-imino-2-phenyl-2-oxazo-lines (see Scheme 1). These complexes were synthesisedby an electrochemical procedure in which the metal isthe anode of an electrochemical cell. This procedurerepresents a simple, high-yielding alternative to otherstandard chemical procedures.

2. Experimental

Anthranilonitrile, tosyl chloride, amino alcohols, ace-tonitrile, chlorobenzene, dichloromethane and othersolvents were dried by standard methods [8]. Cobalt(Aldrich) was used in plate form (approximately 2×2cm).

2.1. Synthesis of ligands

The ligands were synthesised under argon using slightmodifications of the standard literature procedure [9](Scheme 1). Details are given for a representativeexample.

* Corresponding authors. Tel.: +34-986-812-278; fax: +34-986-813-798 (J.C.). Tel.: +34-981-563-100x14245; fax: +34-981-597-525(A.S.).

E-mail addresses: fojo@uvigo.es (J. Castro), qiansoal@usc.es (A.Sousa).

0277-5387/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.PII: S 0 2 7 7 -5387 (01 )00847 -6

J. Castro et al. / Polyhedron 20 (2001) 2329–23372330

2.1.1. [(4-Methylphenyl)sulfonyl]-1H-imino-(2-phenyl-4-isopropyl-2-oxazoline) (HTs�4 iPrOz)

2-(4-Isopropyl-2-oxazoline)aniline was prepared byreaction of anthranilonitrile (3 g, 25 mmol) and 2-amino-3-methyl-1-butanol (8.6 ml, 75 mmol) inchlorobenzene, in the presence of ZnCl2 (0.5 g, 3.7mmol) as a catalyst. The mixture was refluxed underargon for 36 h to give a red solution. The solvent wasremoved and the red crude product was dissolved indichloromethane. After being washed with water, theorganic layer was dried with anhydrous Na2SO4 andthe solvent removed under vacuum. The resulting solidwas purified by chromatography on silica using hex-ane–ethyl acetate (19:1) as eluent to obtain the pureamine (3 g, 59%). Reaction of a solution of this amine(1 g, 4.9 mmol) in dichloromethane with p-toluenesul-fonyl chloride (1.6 g, 8.4 mmol) and aqueous KOH (0.5g, 8.9 mmol) gave a white solid (1.6 g, 89%), which wascharacterised as HTs�4iPrOz. Anal. Found: C, 63.5; H,6.0; N, 7.9; S, 9.2. Calc. for C19H22N2O3S: C, 63.7; H,6.2; N, 7.8; S, 8.9%. IR (KBr, cm−1): 2964 (m), 1625(s), 1559 (m), 1318 (s), 1241 (m), 1173 (s). 1H NMR(CDCl3, ppm): � 12.4 (s, 1H, NH), 7.8–6.7 (m, 8H,phenyl), 4.3 (m, 2H, �CH2), 3.9 (m, 1H, �CH), 2.3 (s,3H, �CH3 tolyl), 1.5 [s, 1H, �CH (isopropyl)], 1.0 [d,3H, �CH3 (isopropyl)], 0.9 [d, 3H, �CH3 (isopropyl)].EI MS; m/z : 358 (M+, 68%), 203 (M+−{O2S�tolyl},5%). Crystals suitable for X-ray diffraction studies wereobtained by crystallisation from dichloromethane.

2.1.2. Analytical data for the other ligands

2.1.2.1. [(4-Methylphenyl)sulfonyl]-1H-imino-(2-phenyl-2-oxazoline) (HTs�Oz). Anal. Found: C, 60.4; H, 5.2;N, 9.0; S, 10.1. Calc. for C16H16N2O3S: C, 60.7; H, 5.1;N, 8.9; S, 10.1%. IR (KBr, cm−1): 2969 (m), 1615 (s),1560 (s), 1313 (s), 1241 (m), 1132 (s). 1H NMR (CDCl3,ppm): � 13.1 (s, 1H, NH), 8.6–7.6 (m, 8H, phenyl),5.2–4.8 (m, 4H, �CH2), 3.1 (s, 3H, �CH3). EI MS; m/z :316 (M+, 100%), 161 (M+−{O2S�tolyl}, 7%).

2.1.2.2. [(4-Methylphenyl)sulfonyl]-1H-imino-(2-phenyl-5-methyl-2-oxazoline) (HTs�5MeOz). Anal. Found: C,

62.1; H, 5.6; N, 8.5; S, 9.6. Calc. for C17H18N2O3S: C,61.8; H, 5.5; N, 8.5; S, 9.7%. IR (KBr, cm−1): 2970(m), 1620 (s), 1558 (m), 1315 (s), 1242 (m), 1135 (s). 1HNMR (CDCl3, ppm): � 12.4 (s, 1H, NH), 7.9–6.9 (m,8H, phenyl), 4.4 (m, 1H, �CH), 3.8 (m, 2H, �CH2), 2.3(s, 3H, �CH3 tolyl), 1.3 (s, 3H, �CH3). EI MS; m/z : 330(M+, 100%), 175 (M+−{O2S�tolyl}, 11%).

2.1.2.3. [(4-Methylphenyl)sulfonyl]-1H-imino-(2-phenyl-4-methyl-2-oxazoline) (HTs�4MeOz). Anal. Found: C,61.7; H, 5.6; N, 8.5; S, 9.8. Calc. for C17H18N2O3S: C,61.8; H, 5.5; N, 8.5; S, 9.7%. IR (KBr, cm−1): 2977(m), 1634 (s), 1506 (m), 1340 (s), 1261 (m), 1161 (s). 1HNMR (CDCl3, ppm): � 12.2 (s, 1H, NH), 7.6–6.9 (m,8H, phenyl), 4.4 (m, 2H, �CH2), 3.8 (m, 1H, �CH), 2.3(s, 3H, �CH3 tolyl), 1.3 (s, 3H, �CH3). EI MS; m/z : 330(M+, 100%), 175 (M+−{O2S�tolyl}, 11%).

2.1.2.4. [(4-Methylphenyl)sulfonyl]-1H-imino-(2-phenyl-4-ethyl-2-oxazoline) (HTs�4EtOz). Anal. Found: C,62.9; H, 5.2; N, 8.0; S, 10.1. Calc. for C18H20N2O3S: C,62.8; H, 5.9; N, 8.1; S, 9.3%. IR (KBr, cm−1): 2970(m), 1634 (s), 1506 (s), 1339 (s), 1268 (m), 1154 (s). 1HNMR (CDCl3, ppm): � 12.4 (s, 1H, NH), 7.8–6.9 (m,8H, phenyl), 4.4 (m, 1H, �CH), 3.8 (m, 2H, �CH2), 2.3(s, 3H, �CH3 tolyl), 1.7 (m, 2H, �CH2(Et)), 1.1 (m, 3H,�CH3(Et)). EI MS; m/z : 344 (M+, 100%), 189 (M+−{O2S�tolyl}, 6%).

2.2. Electrochemical synthesis

The electrochemical method used in the synthesis ofthe complexes was similar to that described by Tuck etal. [10]. The foil anode was suspended from a platinumwire and the cathode was a platinum wire. The ligandwas dissolved in acetonitrile and about 10 mg of te-tramethylammonium perchlorate was added to the so-lution. Applied voltages of 10–20 V allowed sufficientcurrent flow for smooth dissolution of the metal. Dur-ing electrolysis, nitrogen was bubbled through the solu-tion to provide an inert atmosphere and to stir thesolution phase. The cell can be summarised as Co(+ )/CH3CN+HTs�ROz/Pt(− ).

Scheme 1. Formation of [(4-methylphenyl)sulfonyl]-1H-imino-(2-phenyl-2-oxazolines).

J. Castro et al. / Polyhedron 20 (2001) 2329–2337 2331

2.2.1. [Co(Ts�Oz)2]Electrochemical oxidation of a cobalt anode in a

solution of [(4-methylphenyl)sulfonyl]-1H-imino-(2-phenyl-2-oxazoline) (0.251 g, 0.79 mmol) in acetonitrile(50 ml), at 6.5 V and 10 mA for 2 h, caused 23.3 mg ofcobalt to be dissolved, Ef=0.53 mol F−1. During theelectrolysis hydrogen was evolved at the cathode and atthe end of the experiment a crystalline solid had formedat the bottom of the vessel. The solid was filtered off,washed with acetonitrile and diethyl ether, and driedunder vacuum. Anal. Found: C, 55.7; H, 4.8; N, 8.2; S,9.1. Calc. for C32H30CoN4O6S2: C, 55.7; H, 4.4; N, 8.1;S, 9.3%. IR (KBr, cm−1): 2970 (m), 1620 (s), 1558 (m),1315 (s), 1242 (m), 1135 (s). Crystals suitable for X-raydiffraction studies were obtained by crystallisation fromchloroform.

2.2.2. [Co(Ts�5MeOz)2]An experiment similar to that described above (7.5 V,

10 mA, 2 h), with the ligand Ts�5MeOz (0.246 g, 0.75mmol) in acetonitrile (50 ml), dissolved 21.9 mg ofcobalt, Ef=0.50 mol F−1. The solid was collected,washed with cool acetonitrile and diethyl ether, anddried under vacuum. Anal. Found: C, 57.0; H, 5.0; N,7.8; S, 8.8. Calc. for C34H34CoN4O6S2: C, 56.9; H, 4.8;N, 7.8; S, 8.9%. IR (KBr, cm−1): 2984 (m), 1620 (s),1559 (m), 1306 (s), 1240 (m), 1135 (s).

2.2.3. [Co(Ts�4MeOz)2]An acetonitrile solution of HTs�4MeOz (0.246 g,

0.75 mmol) was electrolysed at 10 mA for 2 h and 22mg of cobalt was dissolved from the anode, Ef=0.50mol F−1. At the end of the electrolysis red crystals werepresent in the cell and these were recovered, washedwith cool acetonitrile and diethyl ether, dried undervacuum and identified as [Co(Ts�4MeOz)2]. The crys-tals were suitable for X-ray studies. Anal. Found: C,56.6; H, 4.7; N, 7.4; S, 8.3. Calc. for C34H34CoN4O6S2:C, 56.9; H, 4.8; N, 7.8; S, 8.9%. IR (KBr, cm−1): 2969(m), 1615 (s), 1560 (m), 1313 (s), 1241 (m), 1132 (s).

2.2.4. [Co(Ts�4EtOz)2]An experiment similar to that described above (9 V,

10 mA, 2 h), with the ligand Ts�4EtOz (0.280 g, 0.81mmol) in acetonitrile (50 ml), dissolved 24 mg ofcobalt, Ef=0.55 mol F−1. Crystals, which were suit-able for X-ray studies, were obtained directly from thecell. The solid was collected, washed with cool acetoni-trile and diethyl ether, and dried under vacuum. Anal.Found: C, 58.0; H, 5.4; N, 7.4; S, 8.6. Calc. forC36H38CoN4O6S2: C, 58.0; H, 5.1; N, 7.5; S, 8.6%. IR(KBr, cm−1): 2964 (m), 1615 (s), 1559 (m), 1318 (s),1241 (m), 1135 (s).

2.2.5. [Co(Ts�4 iPrOz)2]A solution of [(4-methylphenyl)sulfonyl]-1H-imino-

(2-phenyl-4-isopropyl-2-oxazoline) (0.267 g, 0.75 mmol)in acetonitrile (50 ml) was electrolysed at 10 mA for 2h and 22.0 mg of cobalt metal was dissolved from theanode, Ef=0.50 mol F−1. The resulting crystals werecollected by filtration, washed with acetonitrile, driedand identified by elemental analysis. Anal. Found: C,59.1; H, 5.6; N, 7.4; S, 8.0. Calc. for C38H42CoN4O6S2:C, 59.0; H, 5.5; N, 7.2; S, 8.3%. IR (KBr, cm−1): 2967(m), 1617 (s), 1559 (m), 1305 (s), 1244 (m), 1134 (s).Crystallisation from chloroform gave monocrystals thatwere suitable for X-ray studies.

2.3. Physical measurements

Elemental analyses were performed on a Carlo-ErbaEA 1108 microanalyser. IR spectra were recorded fromKBr mulls on a Bruker Vector-22 spectrophotometer.Solid-state electronic spectra were recorded on a Shi-madzu UV 3101 PC. Magnetic measurements wereobtained using a DMS VSM 1160 instrument. EI massspectra were recorded on a Kratos-MS-50T spectrome-ter connected to a DS90 data system.

2.4. Crystal structure determination

The data collection was carried out on a BrukerSmart CCD area-detector diffractometer. Data collec-tion was carried out under ambient conditions, usinggraphite monochromated Mo K� radiation (�=0.71073 A� ). All the structures were solved by directmethods and refined by full-matrix least-squares basedon F2 [11]. Non-hydrogen atoms were refined withanisotropic displacement parameters. In the case ofHTs�4iPrOz the hydrogen atoms, except those of themethyl groups, were located on a difference electron-density map and refined. For the other compounds,hydrogen atoms were included in idealised positionsand refined with isotropic displacement parameters.Atomic scattering factors and anomalous dispersioncorrections for all atoms were taken from the Interna-tional Tables for X-ray Crystallography [12]. In thecase of [Co(Ts�4iPrOz)2], the SQUEEZE program [13]was used to correct the reflection data for the diffusescattering due to the presence of disordered solvent.The crystal parameters and other experimental detailsfor the data collection and refinement are summarisedin Table 1.

3. Results and discussion

The analytical data show that the electrochemicalprocedure described can be satisfactorily used for thesynthesis of cobalt complexes of ligands derived from

J. Castro et al. / Polyhedron 20 (2001) 2329–23372332

Table 1Summary of crystal data and structure refinement

[Co(Ts�4MeOz)2]-HTs�4iPrOz [Co(Ts�4EtOz)2] [Co(Ts�4iPrOz)2]Identification code [Co(Ts�Oz)2]CH3CNC36H37CoN5O6S2 C36H38CoN4O6S2C19H22N2O3S C38H42CoN4O6S2Empirical formula C32H30CoN4O6S2

Formula weight 689.67 758.76 745.75 773.81358.45Temperature (K) 291(2)293(2) 293(2) 293(2)293(2)

0.71073 0.710730.71073 0.71073Wavelength (A� ) 0.71073orthorhombicmonoclinic monoclinic orthorhombic monoclinicCrystal system

Space group P21/n (14)P21/c (14) Fddd (70) C2/c (15)Pnaa (56)Unit cell dimensions

14.5353(2)a (A� ) 21.7187(10)12.0558(16) 22.0730(8)13.45090(10)13.64280(10)9.4439(12) 15.37650(10) 22.9076(11) 10.7613(4)b (A� )

16.6241(2) 29.1643(15)16.8554(2) 19.0203(7)16.822(2)c (A� )9096.791(3) 105.4803(7) 90 117.3151(4)� (°)3093.10(5)1901.8(4) 3580.73(7) 14509.9(12) 4014.2(3)V (A� 3)

4 164 4Z 41.407 1.366 1.280Dcalc (g cm−3) 1.252 1.481

0.742 0.648 0.6380.189 0.579Absorption coefficient(mm−1)

F(000) 1428 1580 6224 1620760Crystal size (mm) 0.05×0.10×0.45 0.30×0.30×0.15 0.25×0.40×0.45 0.30×0.45×0.500.62×0.37×0.12

1.92–28.29 1.66–28.241.70–28.02 1.47–28.28Theta range for data 2.08–28.31collection (°)

−29�h�23,−17�h�11, −28�h�27,−15�h�15, −19�h�13,Index ranges−17�k�18,−12�k�11, −20�k�20, −30�k�30, −14�k�14,

−21�l�22−22�l�21−17�l�22 −13�l�25−21�l�38Reflections 10 519/4290 19 862/3840 14 635/498525 438/8753 25 642/4505

[Rint=0.0577] [Rint=0.0288][Rint=0.0263][Rint=0.0590]collected/unique [Rint=0.0587]1.0, 0.56Max/min transmission 1.0, 0.841.0, 0.57 1.0, 0.841.0, 0.53

3840/0/205 8753/0/456 4505/0/2874290/0/233 4985/0/232Data/restraints/parameters

1.036 1.076Goodness-of-fit on F2 1.0700.911 1.039R1=0.0511, R1=0.0528,R1=0.0579, R1=0.0433,Final R indices R1=0.0492,

[I�2�(I)] wR2=0.1237wR2=0.1013 wR2=0.1230wR2=0.1249 wR2=0.1268R1=0.1555,R indices (all data) R1=0.1032, R1=0.1143, R1=0.0704,R1=0.0572,

wR2=0.1341wR2=0.1346wR2=0.1519wR2=0.1225wR2=0.15440.202 and −0.235 0.333 and −0.312Largest difference 0.630 and −0.373 0.794 and −0.234 0.525 and −0.329

peak and hole(e A� −3)

p-toluenesulfonamide-oxazoline, and that the methodrepresents a simple alternative to other standard chemi-cal procedures.

The compounds are of the general formula[Co(Ts�ROz)2], where Ts�ROz − represents the anionof the corresponding ligand. The electrochemical effi-ciency value, Ef, defined as the amount of metal dis-solved per Faraday of charge, was always close to 0.5mol F−1. This fact, along with the evolution of hydro-gen at the cathode, is compatible with the followingreaction mechanism:

cathode: 2HTs�ROz+2e− �2Ts�ROz− +H2

anode: Co+2Ts�ROz− � [Co(Ts�ROz)2]+2e−

3.1. Molecular structure of [HTs�4 iPrOz]

The molecular structure of the ligand HTs�4iPrOz isshown in Fig. 1 along with the atom numbering system

used. Selected bond distances and angles are sum-marised in Table 2.

The ligand shows the expected structure, with thetwo nitrogen atoms bonded through a strong in-tramolecular hydrogen bond (Table 3). The phenyl andthe oxazoline rings are nearly planar, in spite of the sp3

character of the C(1) and C(5) carbon atoms of theoxazoline ring. Conjugation between phenyl and oxazo-line rings is also observed, although this only affects theN�C�O portion in the oxazoline moiety. This conjuga-tion makes both rings coplanar, with a dihedral anglebetween them of only 5.5(1)° and a low value for theC(6)�C(7) bond distance. The C(6)�N(1) bond distancein the oxazoline, 1.276(3) A� , is shorter than C(1)�N(1),1.471(3) A� , as a consequence of the multiple bondbetween C(6) and N(1). Even the O(3)�C(6) bondlength, 1.355(3) A� , is shorter than O(3)�C(5), 1.437(3)A� , due to the different natures of the carbon atoms.The isopropyl group of the oxazoline and the toluene

J. Castro et al. / Polyhedron 20 (2001) 2329–2337 2333

Fig. 1. The molecular structure of [HTs�4iPrOz].

ring are situated at the same side of the plane formedby the phenyl and oxazoline rings, in a configurationdefined by Fujisawa et al. as B [14] (see Scheme 2).Other structural parameters are similar to those foundin other p-toluenesulfonamide ligands [4,7].

3.2. Crystal structure of [Co(Ts�Oz)2]

The molecular structure of [Co(Ts�Oz)2] is shown inFig. 2. Selected bond distances and angles are sum-marised in Table 4. The compound consists of discretemolecules with the cobalt(II) atom in a crystallographictwo-fold axis and tetracoordinated by the nitrogenatoms of the sulfonamide and oxazoline groups of twomonoanionic bidentate ligands. Electronic density datawould normally be insufficient to decide if the coordi-nation of the oxazoline ring is through the nitrogen orthe oxygen atom. However, the asymmetric nature ofthe ligand, with a C�N bond length that is shorter thanthe C�O length, allows us to conclude that this coordi-nation occurs through the nitrogen atom. The environ-ment around the metal can be described as distortedtetrahedral with a dihedral angle between chelate ringsof 78.58(9)°. The main source of distortion is the smallbite angle of these chelate rings, 90.49(10)°, a value thatis similar to those found in other cobalt(II) complexeswith tosylamides as ligands; for instance [2-tosy-lamino(2�-pyridyl)anilinato]cobalt(II), 93.6(5)° [15],or bis - [N - 2 - (2 - pyridyl)phenyl - 4 - methylsulfonamide]-cobalt(II), 91.37(7) and 91.01(7)° [7]. This situationmakes the other angles around the metal bigger thanthe theoretical values. Weak interactions between themetal and the O(2) and O(2)� atoms of the sulfonylgroups are also observed, Co�O(2)=2.690(3) A� . This

behaviour has also been observed in bis-[N-2-(2-pyridyl)phenyl-4-methylsulfonamide]cobalt(II) [7], withCo�O bond distances of 2.727 and 3.127 A� . This weak

Table 2Selected bond lengths (A� ) and bond angles (°) for HTs�4iPrOz

Bond lengths1.4276(19)S�O(2) S�O(1)1.4164(19)

S�N(2) 1.749(3)S�C(13)1.617(2)N(1)�C(1)1.276(3)N(1)�C(6) 1.471(3)

1.355(3)N(2)�C(12) 1.412(3) O(3)�C(6)1.497(4)O(3)�C(5) 1.437(3) C(1)�C(2)1.519(4)C(2)�C(3)C(1)�C(5) 1.533(3)

C(2)�C(4) 1.528(4)

Bond anglesO(2)�S�O(1) 109.54(14)O(2)�S�N(2)119.58(13)O(1)�S�N(2) 107.51(12)103.99(12) O(2)�S�C(13)

109.05(13)O(1)�S�C(13) N(2)�S�C(13) 106.47(12)C(6)�N(1)�C(1) 108.2(2) C(12)�N(2)�S 127.44(19)

112.7(2)N(1)�C(1)�C(2)C(6)�O(3)�C(5) 106.35(19)103.0(2)N(1)�C(1)�C(5) C(2)�C(1)�C(5) 115.3(2)

C(1)�C(2)�C(3) 111.7(2) C(1)�C(2)�C(4) 109.9(2)C(3)�C(2)�C(4) O(3)�C(5)�C(1) 105.1(2)110.9(3)

117.0(2)N(1)�C(6)�O(3) N(1)�C(6)�C(7) 126.3(3)116.7(2)O(3)�C(6)�C(7)

Table 3Hydrogen bonds for HTs�4iPrOz

Atom: A···HD d(D�H) �DHAd(D···A)d(H···A)

144(3)2.646(3)1.90(2)N(2)�H(2)···N(1) 0.86(3)0.93 2.747(4)C(8)�H(8)···O(3) 2.41 101.4

C(11)�H(11)···O(2) 0.93 2.46 3.101(4) 126.20.93C(18)�H(18)···O(2) 2.916(4) 102.92.56

J. Castro et al. / Polyhedron 20 (2001) 2329–23372334

Scheme 2.

Fig. 2. The molecular structure of [Co(TsOz)2].

Co�O interaction makes the O(2)�S�N(2) angle,103.38(14)°, slightly smaller than one would expect fora regular tetrahedron. In the complex the ligands adoptan arrangement with the tosyl groups pointing in oppo-site directions, making the Nsulfamide�Co�Nsulfamide bondangle 126.35(13)°.

The values of the Co�Noxazoline bond distances arenormal and are similar to the Co�N bond distancesfound in the two complexes mentioned above. In addi-tion, they are not dissimilar from those found in the[�3-sulfido-(oxazolyl)(oxazol-2-thiolate)hexacarbonyl]-tricobalt trimer [16], 1.98(1) A� , a complex of Co(II)coordinated to a nitrogen atom of an oxazoline ring.

3.3. Crystal structure of [Co(Ts�4MeOz)2],[Co(Ts�4EtOz)2] and [Co(Ts�4 iPrOz)2]

Views of the molecular structures of these complexesare shown in Figs. 3–5. Selected bond lengths andangles are given in Tables 5–7.

These compounds are monomeric with the cobaltatom in a two-fold symmetry axis that is also crystallo-graphic in the case of [Co(Ts�4EtOz)2] and[Co(Ts�4iPrOz)2]. The metal is tetracoordinated by two

anionic bidentate chelate ligands in a [CoN4] environ-ment. The coordination is through the nitrogen atom ofthe oxazoline ring, in spite of the steric effect of thesubstituents, and through the sulfonamide nitrogen.

Table 4Selected bond lengths (A� ) and bond angles (°) for [Co(Ts�Oz)2]

Bond lengths2.000(2)Co�N(2)1.999(3)Co�N(1)

1.999(3) Co�N(2)� 2.000(2)Co�N(1)�2.690(3) Co�O(2)� 2.690(3)Co�O(2)

1.447(2)S�O(2)S�O(1) 1.439(2)1.603(2) S�C(10) 1.762(3)S�N(2)1.278(4)N(1)�C(3) N(1)�C(1) 1.479(4)

1.355(3)1.412(4) O(3)�C(3)N(2)�C(9)1.444(5)O(3)�C(2)

Bond angles101.51(16)N(1)�Co�N(1)� N(1)�Co�N(2) 90.49(10)

N(1)��Co�N(2) 124.22(10) N(1)�Co�N(2)� 124.22(10)N(1)��Co�N(2)� 90.49(10) 126.35(13)N(2)�Co�N(2)�O(1)�S�O(2) 116.77(15) O(1)�S�N(2) 115.00(13)

103.38(14)O(2)�S�N(2)

Symmetry transformations used to generate equivalent atoms: x,0.5−y, 1.5−z.

J. Castro et al. / Polyhedron 20 (2001) 2329–2337 2335

Fig. 3. The molecular structure of [Co(Ts�4MeOz)2]. The solvent chloroform molecule has been excluded for clarity.

Fig. 4. The molecular structure of [Co(Ts�4EtOz)2].

The coordination polyhedron around the metal is ahighly distorted tetrahedron, with dihedral angles be-tween the two chelate rings of 78.59(9), 76.73(6) and71.47(7)°, respectively, showing the increasing stericeffect of the substituents. The replacement by differentR groups of an �-hydrogen atom in the oxazoline ringcauses only minor changes in the structures of thecomplexes.

However, the presence of these substituents producessteric restrictions that force the ligands to adopt, in the

complex, the configuration defined by Fujisawa et al. asA [14] (see Scheme 2), a situation in contrast with theconfiguration B adopted in the case of the free ligand.As one can see from Scheme 2, the main differencebetween the two configurations is the relative positionof the groups directly attached to the sulfur atom of thesulfonamide group.

The influence of the substituent on the oxazoline ringis also reflected in the relative positions adopted by thep-toluene rings of the sulfonamide groups in the struc-

J. Castro et al. / Polyhedron 20 (2001) 2329–23372336

tures of the complexes containing substituents whenthey are compared with the complex without sub-stituents, as judged by the angle N(2)�Co�N(2)� in[Co(Ts�Oz)2], which changes from 126.35(13) to146.80(11), 149.42(10) and 147.69(12)° for the corre-sponding angles in [Co(Ts�4MeOz)2], [Co(Ts�4EtOz)2]and [Co(Ts�4iPrOz)2], respectively. This situationmakes the distance between the �-carbon of the oxazo-line ring and the p-toluene ring carbon atom bonded tosulfur larger in the complexes containing a substituent(in the range 5.4–5.8 A� ) than the corresponding dis-tances in the complex without a substituent, 4.673 A� .

Table 6Selected bond lengths (A� ) and bond angles (°) for [Co(Ts�4EtOz)2]

Bond lengths2.0106(18)Co�N(1) Co�N(2) 2.0108(17)2.0106(18)Co�N(1)� Co�N(2)� 2.0108(17)

2.5502(17)Co�O(2)�Co�O(2) 2.5502(17)1.350(2)O(3)�C(5)1.282(3)N(1)�C(5)

1.4310(18)S�O(1) 1.4496(19)S�O(2)�S�C(12)1.6040(17)S�N(2) 1.768(2)

1.436(4)O(3)�C(1) N(1)�C(2) 1.484(3)N(2)�C(11) 1.402(3) O(3)�C(5) 1.350(3)

Bond angles89.78(7)111.77(11) N(1)�Co�N(2)N(1)�Co�N(1)�

107.43(7)N(1)�Co�N(2)� N(1)�Co�N(2)� 107.43(7)89.78(7)N(1)��Co�N(2)� N(2)�Co�N(2)� 149.42(10)

150.01(7)N(1)�Co�O(2) N(1)�Co�O(2)� 87.23(7)N(2)�Co�O(2)95.14(7) 61.70(6)N(2)��Co�O(2)

61.70(6)N(2)��Co�O(2)� O(2)�S�N(2) 102.55(10)114.78(10) O(1)�S�O(2)O(1)�S�N(2) 116.21(12)

Symmetry transformations used to generate equivalent atoms: x,1.5−y, 1.5−z.

Fig. 5. The molecular structure of [Co(Ts�4iPrOz)2].

Table 7Selected bond lengths (A� ) and bond angles (°) for [Co(Ts�4iPrOz)2]

Bond lengths2.0005(17)Co�N(2)Co�N(1) 2.005(2)

2.0005(17)Co�N(2)� Co�N(1)� 2.005(2)Co�O(2) 2.6237(18) Co�O(2)� 2.6237(18)

1.346(3)O(3)�C(6)N(1)�C(6) 1.286(3)S�O(1) 1.4441(18) S�O(2)� 1.4510(17)S�N(2) 1.603(2) S�C(13) 1.768(2)N(2)�C(12) 1.286(3)1.406(3) N(1)�C(6)

1.346(3)O(3)�C(6)N(1)�C(1) 1.491(3)1.458(4)O(3)�C(2)

Bond anglesN(2)�Co�N(2)� 147.69(12) N(1)�Co�N(2) 90.80(8)

105.90(8) N(1)�Co�N(2)�N(1)��Co�N(2) 105.90(8)90.80(8)N(1)��Co�N(2)� N(1)�Co�N(1)� 117.69(13)

N(2)�Co�O(2) 60.62(7) N(1)�Co�O(2) 149.29(7)N(2)�Co�O(2)� 95.19(7) N(1)�Co�O(2)� 83.36(7)

88.04(9)O(2)�Co�O(2)� O(2)�S�N(2) 103.20(10)O(1)�S�O(2)� 114.27(11)O(1)�S�N(2)115.86(11)

Symmetry transformations used to generate equivalent atoms: −x, y,0.5−z.

Table 5Selected bond lengths (A� ) and bond angles (°) for [Co(Ts�4MeOz)2]

Bond lengthsCo�N(11) 2.008(3) Co�N(22) 2.014(2)Co�N(21) Co�N(12) 2.017(2)2.015(3)

Co�O(12)2.575(2) 2.614(2)Co�O(22)1.285(4)N(21)�C(24)1.275(4)N(11)�C(14)1.349(4)O(13)�C(14) 1.361(4) O(23)�C(24)1.457(2)S(1)�O(12)S(1)�O(11) 1.443(2)

S(1)�N(12) 1.606(3) 1.437(2)S(2)�O(21)S(2)�O(22) S(2)�N(22)1.451(2) 1.616(3)

Bond angles111.54(11)N(21)�Co�N(12)106.74(10)N(11)�Co�N(22)

N(11)�Co�N(21) 111.27(12) N(22)�Co�N(21) 89.51(11)N(11)�Co�N(12) 146.80(11)N(22)�Co�N(12)89.73(10)

61.44(8)N(11)�Co�O(22) 86.83(9) N(22)�Co�O(22)N(21)�Co�O(22) 91.83(9)149.74(9) N(12)�Co�O(22)

149.85(9) N(22)�Co�O(12) 96.81(9)N(11)�Co�O(12)87.02(10) N(12)�Co�O(12) 60.71(8)N(21)�Co�O(12)

O(22)�Co�O(12) 102.89(13)88.22(8) O(12)�S(1)�N(12)114.26(14) O(11)�S(1)�O(12) 116.35(14)O(11)�S(1)�N(12)102.43(13)O(22)�S(2)�N(22)

This fact surely reflects a tendency to reduce the inter-action between the substituent on the oxazoline ringand the p-toluene ring. In this respect, the value of thebond angle for Nsulfamide�Co�Nsulfamide increases up to146.80(11), 149.42(10) and 147.69(12)° and, conse-quently, the extent of distortion of the geometry aroundthe metal increases. A weak interaction between thecobalt atom and one oxygen atom from the sulfonylgroup is also observed in these compounds, and thenew disposition of the ligand approaches the oxygenatoms such that bond distances in the range2.5502(17)–2.6237(18) A� are seen. All other bondlengths and angles in these three compounds are verysimilar to those found in [Co(Ts�Oz)2].

J. Castro et al. / Polyhedron 20 (2001) 2329–2337 2337

The [Co(Ts�4MeOz)2] compound crystallises with amolecule of solvent acetonitrile, but it does not interactwith the complex to any significant extent.

3.4. Spectroscopic studies

The IR spectra of the ligands show the expectedbands. The absence of bands at 3200 cm−1, at-tributable to �(N�H), and the presence of bands near2970 cm−1 are indicative of an intramolecular hydro-gen bond. These bands are absent from the IR spectraof the complexes, indicating that the ligand is in theanionic form in all the metallic complexes. A strongband in the 1620–1625 cm−1 region, attributed to�(C�N), is shifted to lower frequency on going from thefree ligand to the complexes. The �(S�O) symmetricand asymmetric vibration modes appear at 1130–1180and 1315–1320 cm−1, respectively. Bands in the 1500–1580 cm−1 region, which are characteristic of aromaticring vibrations �(C�C), and a medium band at approx-imately 1240 cm−1, attributable to �(C�O), are alsoobserved.

The solid state electronic spectra in the near IR–Visregion of cobalt(II) complexes show two d–d transitionbands of the type expected for distorted tetrahedralcobalt(II) compounds [17], one at 19 400–20 190 cm−1

and the other as a multicomponent band in the range7200–13 000 cm−1. The band in the visible region hasbeen assigned to a 4T1(P)�4A2 (�3) and the multicom-ponent one in the near-IR region to a 4T1(F)�4A2 (�2)transition. The 4T2�4A2 (�1) transition was not ob-served, but its position at the range 6600–5690 cm−1

has been calculated using the method described byLever [17]. The values obtained for 10Dq, in the rangeof 5700–6500 cm−1, for �, 0.722–0.875, and B, 701–790 cm−1, are also in the range expected for pseudote-trahedral cobalt(II) complexes. The magnetic momentsfor the complexes, 3.9–4.1 BM, are in the range ex-pected for tetrahedral cobalt(II) compounds.

4. Supplementary material

Crystallographic data for the structural analysis havebeen deposited with the Cambridge CrystallographicData Centre, CCDC Nos. 156545–156549. Copies ofthis information may be obtained free of charge from

The Director, CCDC, 12 Union Road, Cambridge,CB2 1EZ (fax: +44-1223-336033; e-mail: deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).

Acknowledgements

We thank the Xunta de Galicia (PGIDT00PX-I20305PR) and (PGIDT99PXI20306B) for financialsupport. All the crystallographic calculations were per-formed on the FERGUS system (http://angus.uvigo.es/).

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