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[S2], [S3], and [N3] coordination modes of hydrotris(thioxotriazolyl)borato. Zinc, nickel, cobalt, and bismuth complexes
Inorganica Chimica Acta 357 (2004) 367–375 www.elsevier.com/locate/ica
[S2], [S3], and [N3] coordination modes of hydrotris(thioxotriazolyl)borato. Zinc, nickel, cobalt, and bismuth complexes q *, Clara Mora, Maria Angela Pellinghelli Maurizio Lanfranchi, Luciano Marchio Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Universit a degli Studi di Parma, Parco Area delle Scienze 17a, I 43100 Parma, Italy Received 22 January 2003; accepted 11 June 2003
Abstract The ligand hydrotris(1,4-dihydro-3-methyl-4-phenyl-5-thioxo-1,2,4-triazolyl)borato (TrPh;Me ) was synthetized as natrium salt and the complexes [Zn(TrPh;Me )2 ] 7.5H2 O 1.5CH3 CN (2a), [Zn(TrPh;Me )2 ] 8DMF (2b), [Co(TrPh;Me )2 ] 8DMF (3a), [Ni(TrPh;Me )2 ] H2 O 6DMSO (4a), [Bi(TrPh;Me )2 ]NO3 (5), have been isolated and structurally characterized by X-ray diffraction. In the zinc derivatives the ligand adopts different denticity and coordination modes, g2 and [S2 ] for 2a and g3 and [N3 ] for 2b, depending on the crystallization solvent, giving rise to tetrahedral and octahedral geometry, respectively. In the octahedral cobalt and nickel complexes the ligand is g3 and [N3 ] coordinated whereas in the bismuth complex the g3 and [S3 ] coordination is exhibited. Ó 2003 Elsevier B.V. All rights reserved. Keywords: Substituted tristriazolylborates; Zinc; Cobalt; Nickel; Bismuth
1. Introduction The realm of boron centered tripodal ligands includes a great number of compounds that are mainly differentiated by the donor capability of the heterocyclic rings linked to the boron center. The Tp ([N3 ] coordination mode) [1] and Tm ([S3 ] coordination mode) [2] ligand classes have been extensively used as models for zinc enzyme [3,4], and in order to better mimic the alcohol dehydrogenase active sites, the mixed ligands [pzBm] ([S2 N] coordination mode, displaying pyrazole and thioxoimidazole rings) have been employed [5,6]. A different approach has been followed with the synthesis of the hydrotris(1,4-dihydro-3-R0 -4-R-5-thioxo-1,2,4-triazolyl)0 borato ligands (TrR;R ) 1 as they bear on each triazoline ring a nitrogen atom and a C@S group and can act as q
Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.ica.2003.06.004. * Corresponding author. Tel.: +39-521-905424; fax: +39-521-905557. E-mail address: [email protected] (L. Marchi o). 1 The apex indicates the substituents on the thioxotriazolinyl rings. The first fragment is relative to the substituent on the N4 nitrogen atom whereas the second is for the substituent on the C3 carbon atom. 0020-1693/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2003.06.004
[S3 ] and [N3 ] donors towards metal ions [7]. They are able to satisfy the coordination requirements of hard and soft metal ions and allow tetrahedral or octahedral coordination geometries. We are currently examining their coordination chemistry with various metal ions and we are presently investigating the effect that the steric hindrance, in proximity to the C@S and nitrogen atoms, may play on the coordination properties of these ligands. Placing a phenyl group close to C@S could limit the accessibility of the [S3 ] coordination mode in favor of the less encumbered [N3 ] mode in [M(L)2 ]ðn 2Þþ octahedral complexes. The steric hindrance for the Tp, Tm, and [pzBm] ligands has been used as a tetrahedral enforcer in order to favor the tetrahedral geometry of zinc complexes and to better mimic the geometrical features of the alcohol dehydrogenase and carbonic anhydrase active sites [4,5,8]. In fact, many TpZn-X structures have been reported where the steric hindrance on the pyrazole 3position forces a tetrahedral geometry [9] and only one example of an octahedral zinc complex is reported where the bulkiness of the pyrazole substituents does not seem to interfere with the coordination geometry [10].
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product is collected (1.961 g, 45%). Anal. Calc for C27 H25 BN9 S3 Na: C, 53.55; H, 4.16; N, 20.82. Found: C, 53.17; H, 4.32; N, 20.46%. IR data (KBr disks cm1 ): 3063m, 2926m, 2551w [m(B–H)], 1578s, 1499s, 1415s, 1382m, 1324s, 1274s, 1130m, 1014m, 698m, 565m. 1 H NMR (300 MHz, D2 O): 2.28 (s, 3H, CH3 ), 7.54 ppm (m, 2H, Ph), 7.75 ppm (m, 3H, Ph). 2.2. [Zn(TrPh;Me )2 ] (2)
Scheme 1.
In this paper we report the syntheses and structures of TrPh; Me (Scheme 1) derivatives of zinc, nickel, cobalt, and bismuth in the molar ratio 2:1. In the case of the zinc complex, two structures are obtained whereby the metal is in a tetrahedral and octahedral geometry and the ligand exhibits [S2 ] and [N3 ] binding modes, respectively.
2. Experimental All solvents and reagents are commercially available (Sigma–Aldrich) and were used as received. The 1 H NMR spectra were recorded on a Bruker AC 300 spectrometer operating at room temperature. Chemical shifts are reported in ppm referenced to residual solvent protons (DMSO-d6 , DMF-d7 , D2 O, CDCl3 ). Mass spectra were obtained with a Finnigan 1020 mass spectrometer in positive ion mode with a MATSS 710 quadrupole. Infrared spectra were recorded using KBr pellets from 4000 to 400 cm1 on a Perkin–Elmer FT-IR Nexus spectrometer. Elemental analysis (C, H, N) was performed with a Carlo Erba EA 1108 automated analyser. The compound 1,4-dihydro-3-methyl-4-phenyl-5thioxo-1,2,4-triazole has been prepared according to published procedures [11,12]. 2.1. [Na(TrPh;Me )] (1) 1,4-Dihydro-3-methyl-4-phenyl-5-thioxo-1,2,4-triazole (5.29 g, 27.6 mmol) and sodium tetrahydroborate (0.270 g, 7.13 mmol) were mixed together in a 100 ml round-bottomed flask fitted to a volumetric device for measuring hydrogen evolution. Upon stirring, the temperature was raised gently to 230 °C whereupon evolution of hydrogen gas began. The mixture melted at this temperature which was maintained for 1.5 h. The reaction mixture was allowed to cool to room temperature. The resulting yellow glassy solid was then inserted in the thimble of a soxhlet apparatus and washed with chloroform for 6 h. From the thimble, a powdery white
A mixture of ZnSO4 7H2 O (0.110 g, 0.383 mmol) and 1 (0.460 g, 0.760 mmol) was heated to reflux in methanol (100 ml) for 6 h. The solvent was removed under vacuum from the resulting white suspension. The pale yellow powder was suspended in water (30 ml) and filtered. The pale yellow product was then collected (0.406 g, 86%). Anal. Calc for C54 H50 N18 S6 B2 Zn: C, 52.71; H, 4.10; N, 20.49. Found: C, 52.21; H, 4.45; N, 20.28%. IR data (KBr disk, cm1 ): 3063m, 2927m, 2497w [m(B–H)], 1576m, 1499s, 1414s, 1383s, 1328s, 1279s, 1015m, 835m, 697m. 1 H NMR (300 MHz, CDCl3 ): 2.06 ppm (s, 3H, CH3 ), 7.17 ppm (m, 2H, Ph), 7.44 ppm (m, 3, Ph); 1 H NMR (300 MHz, DMF-d7 ): 2.24 ppm (s, 3H, CH3 ), 7.39 ppm (m, 2H, Ph), 7.58 (m, 3H, Ph). 1 H NMR (300 MHz, CH3 CN-d3 ): 2.42 ppm (m, 3H, CH3 ), 7.29–7.65 ppm (m, 5H, Ph). The product was recrystallized from an acetonitrile/water solution and from a DMF solution from which two crystal types suitable for X-ray structure determination were obtained ([Zn(TrPh;Me )2 ] 7.5H2 O 1.5CH3 CN (2a) in acetonitrile/water and [Zn(TrPh;Me )2 ] 8DMF (2b) in DMF). 2.3. [Co(TrPh;Me )2 ] (3) CoCl2 6H2 O (0.060 g, 0.252 mmol) was dissolved in water (15 ml) and was added to a suspension (20 ml) of 1 (0.320 g, 0.528 mmol) in the same solvent. The mixture instantly became pale pink and was stirred at room temperature for 4 h. The solvent was then removed by filtration and the pink powder was collected (0.293 g, 95%). Anal. Calc for C54 H50 N18 S6 B2 Co: C, 52.99; H, 4.12; N, 20.60. Found: C, 52.38; H, 3.78; N, 19.96%. IR data (KBr disk, cm1 ): 3062m, 2927w, 2568w [m(B–H)], 1590m, 1580m, 1498s, 1414s, 1383s, 1323m, 1224m, 819m, 693m. Recrystallization of the pink powder from a DMF solution gave yellow crystals suitable for X-ray analysis corresponding to [Co(TrPh;Me )2 ] 8DMF (3a). 2.4. [Ni(TrPh;Me )2 ] (4) A mixture of NiCl2 6H2 O (0.070 g, 0.295 mmol) and 1 (0.370 g, 0.611 mmol) was stirred at room temperature in methanol (40 ml) for 7 h. The initially green solution turned to yellow after a few hours. The solvent was
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removed under vacuum and the yellow powder was dissolved in acetonitrile (30 ml). The mixture was filtered, the solvent was removed under vacuum and a green product was collected (0.322 g, 89%). Anal. Calc for C54 H50 B2 N18 S6 Ni: C, 53.00; H, 4.12; N, 20.60. Found: C, 52.13; H, 4.45; N, 20.13%. IR (KBr disk, cm1 ): 3062w, 2965w, 2926w, 2601w, 1593s, 1567s, 1498s, 1417s, 1380s, 1272s, 1129s, 1020s, 823m, 698m. Suitable crystals for X-ray structure determination were obtained from a DMSO solution corresponding to [Ni(TrPh;Me )2 ] H2 O 6DMSO (4a). 2.5. [Bi(TrPh; Me )2 ]NO3 (5) Bi(NO3 )3 5H2 O (0.084 g, 0.232 mmol) was dissolved in methanol (15 ml) and was added to a methanolic (30 ml) solution of 1 (0.281 g, 0.464 mmol). The mixture turned red instantly. The solution was stirred at room temperature for 4 h. The solvent was then removed under vacuum, the red powder was washed with water (30 ml) and collected (0.315 g, 72%). IR data (KBr disk, cm1 ): 3061m, 2927m, 2520m [m(B–H)], 1567m, 1498m, 1427m, 1384s, 1325m, 1276m, 693m. 1 H NMR (300 MHz, DMSO-d6 ): 2.14 (s, 3H, CH3 ), 7.36 ppm (m, 2H, Ph), 7.55 ppm (m, 3H, Ph). Anal. Calc for C54 H50 B2 N19 O3 S6 Bi: C, 45.16; H, 3.51; N, 18.53. Found: C, 44.88; H, 2.99; N, 18.83%. Recrystallization of the reddish powder from an acetonitrile/water solution gave red crystals suitable for X-ray analysis corresponding to [Bi(TrPh;Me )2 ]NO3 .
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2.6. X-ray crystallography A summary of data collection and structure refinement is reported in Tables 1 and 2. Single crystal data were collected with an Enraf-Nonius CAD4 diffractom for 2a, and 4a, with a eter (Cu Ka; k ¼ 1:541838 A) Bruker AXS Smart 1000 area detector diffractometer for 2b and 3a and with a (Mo Ka; k ¼ 0:71073 A) Philips PW 1100 diffractometer (Mo Ka; k ¼ 0:71073 A) for 5. Empirical absorption correction was applied using the program X A B S 2 [13] for 2a and 4a, the program S A D A B S [14] for 2b and 3a and the Psi-scan semiempirical method [15] for 5 (max. and min. absorption correction coefficients: 1.000, 0.376 (2b); 1.000, 0.201 (2a); 1.000, 0.815 (3a); 1.000, 0.633 (4a); 1.000, 0.784 (5)). These structures were solved by direct methods (SIR97) [16] and refined with full-matrix least-squares (S H E L X L -97) [17], using the Wingx software package [18]. Non-hydrogen atoms were refined anisotropically; H atoms were found and refined for the BH groups of 4a and 5. The remaining H atoms were placed at their calculated positions. The nitrate ion of 5 was found to be disordered and distributed in 12 positions each with an occupancy factor of 0.083. DMF solvent molecules in 2b and 3a were severely disordered and were treated using the S Q U E E Z E P L A T O N program [19]. In the asymmetric unit of 4a, three DMSO solvent molecules and a water molecule with an occupancy factor of 0.5 were found whereas for each asymmetric unit of 2a, 1.5 acetonitrile solvent molecules and 7.5 water molecules
Table 1 Summary of X-ray crystallographic data for 2a and 2b
Empirical formula Formula weight Colour, habit Crystal size, mm Crystal system Space group a (A) b (A) c (A)
(2a)
(2b)
C57 H69:50 B2 N19:50 O7:50 S6 Zn 1427.17 colourless, block 0.40 0.39 0.13 triclinic P1 11.956(8) 14.397(5) 22.927(13) 72.93(2) 75.04(2) 85.19(2) 3645(3) 2 1488 Cu Ka (1.54184) 293 1.300 2.580 3.21–55.00 9130/9130 0.0690 0.1760 0.512 and )0.428
C78 H106 B2 N26 O8 S6 Zn 1815.24 colourless, block 0.30 0.30 0.30 cubic Pa3 21.170(7) 21.170(7) 21.170(7) 90 90 90 9488(5) 4 3824 Mo Ka (0.71073) 293 1.271 0.455 1.92–24.02 16,079/2487 0.0436 0.0689 0.125 and )0.173
a (°) b (°) c (°) 3 ) V (A Z F (0 0 0) Radiation (k (A)) T (K) qcalc (Mg/m3 ) l (mm1 ) h range, (°) Number of reflections/observed F > 4rðF Þ R1 wR2 3 ) Largest difference peak/hole (e A P P P P R1 ¼ jjFo j jFc jj= jFo j, wR2 ¼ ½ ½wðFo2 Fc2 Þ2 = ½wðFo2 Þ2 1=2 , w ¼ 1=½r2 ðFo2 Þ þ ðaP Þ2 þ bP , where P ¼ ½maxðFo2 ; 0Þ þ 2Fc2 =3.
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Table 2 Summary of X-ray crystallographic data for 3a, 4a and 5 (3a)
(4a)
(5)
Empirical formula Formula weight Colour, habit Crystal size (mm) Crystal system Space group a (A) b (A) c (A)
C78 H106 B2 CoN26 O8 S6 C66 H88 B2 N18 NiO7 S12 C54 H50 B2 BiN19 O3 S6 1808.80 1710.59 1436.09 yellow, block green, block red, block 0.35 0.35 0.27 0.25 0.20 0.15 0.35 0.28 0.21 cubic triclinic rhombohedral Pa3 P1 R3 21.219(4) 11.978(7) 14.516(3) 21.219(4) 12.445(3) 14.516(3) 21.219(4) 14.484(8) 25.240(5) a (°) 90 102.95(3) 90 b (°) 90 95.68(4) 90 c (°) 90 96.74(3) 120 3 ) V (A 9554(3) 2072(2) 4606(2) Z 4 1 3 F (0 0 0) 3812 869 2160 Radiation (k, A) Mo Ka (0.71073) Cu Ka (1.54184) Mo Ka (0.71073) T (K) 293 173 293 qcalc (Mg/m3 ) 1.258 1.371 1.553 0.375 3.654 3.135 l (mm1 ) h range (°) 1.92–21.99 3.16–62.49 3.61–25.05 Number of reflections/observed F > r4ðF Þ 14,628/1955 6378/6378 5399/1814 R1 0.0453 0.0687 0.0279 wR2 0.0649 0.1853 0.0369 3 ) Largest difference peak/hole (e A 0.141 and )0.124 0.405 and )0.670 0.253 and )0.284 P P P P 2 2 2 2 2 2 1=2 2 2 2 R1 ¼ jjFo j jFc jj= jFo j, wR2 ¼ ½ ½wðFo Fc Þ = ½wðFo Þ , w ¼ 1=½r ðFo Þ þ ðaP Þ þ bP , where P ¼ ½maxðFo ; 0Þ þ 2Fc2 =3.
were present. The programs P A R S T [20,21] and O R T E P for Windows [22] were also used. Full tables of bond lengths and angles, atomic positional parameters, isotropic and anisotropic displacement parameters are given in the supplementary material.
The complexes have been synthesized by metathesis by reacting (in methanol for 2, 4, and 5 and in water for 3) suitable inorganic salt of the metals and 1. They are insoluble in water and can be purified washing the reaction powder with this solvent. 3.1. Molecular structures
3. Results and discussion It has been shown that in the [Cu(TrEt;Me )]2 and [Bi(TrEt;Me )2 ]NO3 complexes the ethyl groups close to the C@S adopt a conformation in which they are perpendicular to the triazoline rings and this results in their limited ability to function as hindering group for the thioxo moiety [23]. This prompted us to increase the steric bulk of the substituent on the N4 triazoline atom, (Scheme 1). Placing the phenyl group in close proximity to the C@S could limit the accessibility of the [S3 ] coordination mode in [M(TrPh;Me )2 ]ðn 2Þþ complexes and could consequently hinder the occurrence of the octahedral geometry if the ligand binds through the thioxo groups. On the contrary, the less encumbered methyl group close to the triazoline nitrogen atoms would not prevent the occurrence of the [N3 ] coordination mode for [M(TrPh;Me )2 ]ðn 2Þþ octahedral complexes as it was found in the [Na(Tt)2 ]þ cation [7]. In this were the case, the phenyl groups would point away from the coordination center and would not affect the coordination geometry.
For the crystals of 2 obtained from the acetonitrile/ water solution, the solvent enters the crystal lattice and the complex was formulated as [Zn(TrPh;Me )2 ] 7.5H2 O 1.5CH3 CN (2a), Fig. 1. The metal is in a distorted tetrahedral geometry and the ligand behaves as bidentate [S2 ]. The Zn–S distances range from 2.310(3) to 2.381(3) and the bond angles from 97.71(9)° to 119.21(10)° A (Table 3) in accordance with the value reported for and 85.58– similar thionic compounds (2.258–2.413 A 121.55°) [24]. Noteworthy is the fact that for each tripodal ligand, one of the triazoline rings does not participate in the coordination, a situation previously reported for [Zn(Ttt-Bu )2 ] [4]. In this latter case the metal adopts a tetrahedral coordination despite the presence of a relatively small encumbering group such as methyl close to the C@S. It is possible that the phenyl ring in TrPh;Me does not have any effect in dictating the coordination geometry around zinc in 2a but this could be a consequence of a natural tendency for Zn(II) to adopt a Zn[S4 ] coordination geometry as it was suggested for [Zn(Ttt-Bu )2 ]. The ligands could also act as tridentate
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Fig. 1. ORTEP drawing of 2a. Thermal ellipsoids are drawn at the 30% probability level.
[S2 N] but the preferred tetrahedral geometry of the zinc(II) cation [25] prevents the additional coordination of the triazoline nitrogen atoms. An analogous scenario was exhibited for [pzBmMe ]2 Zn in which the pyrazolyl ‘‘arm’’ of the tripodal ligand does not bind the metal [6]. It is not excluded that for these ZnS4 motifs, the coorTable 3 and angles (°) with estimated standard deSelected bond lengths (A) viations in parentheses for compounds 2a, 2b, 3a, 4a, and 5 (2a) Zn–S1 Zn–S2 Zn–S4 Zn–S5
2.381(3) 2.310(3) 2.339(3) 2.335(2)
S1–Zn–S2 S1–Zn–S4 S1–Zn–S5 S2–Zn–S4 S2–Zn–S5 S4–Zn–S5
109.21(9) 97.71(9) 108.82(9) 119.22(10) 110.62(10) 110.22(9)
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dinated thioxo groups provide sufficient electron density to satisfy the zinc demand limiting the coordination to tetrahedral. In 2a, the two eight-membered chelate rings can be considered equivalent to a six-membered one because the triazoline rings are planar and the S and B atoms lie in this plane. The centroid of each triazoline ring can be considered occupying a vertex of the sixmembered ring as it was proposed for the ligand BtEt;Me [26]. In this context the conformation is boat for both chelating rings with the apices occupied by a sulfur atom and a triazoline centroid. In both chelating ring systems the separation between a coordinated sulfur atom and the opposite C1 and N1 atoms is less than the sum of the van der Waals radii (S1 C12, 3.28(1); S1 N12, and can 3.19(1); S4 C15, 3.36(1); S4 N15, 3.22(1) A) be defined, from geometrical consideration, as a p interaction. In the boat containing B1 the uncoordinated triazoline ring occupies an equatorial position whereas in the boat containing B2, an axial one. As reported for [Cu(TrEt;Me )]2 [23], of the two ligands, the one containing B1 exhibits an ‘‘inverted’’ conformation (with two of the C@S surrounding the B–H group) and the B1–H1 points toward the metal even though the Zn H1 separation is too long for a possible Zn H–B inter(3.554(2) A) action whereas the ligand containing B2 is in a ‘‘normal’’ conformation with the B–H pointing away from the metal. The dihedral angles between the triazoline rings and the phenyl groups attached to them range from 68.6(5) to 87.7(4)°. Apart from N26, which interacts with the other the coordinated S2 atom (S2 N26, 3.28(1) A), iminic nitrogen atoms are involved in hydrogen bonds with solvation water molecules. Recrystallization of 2 from a DMF solution gave the complex that could be formulated as [Zn(TrPh;Me )2 ] 8DMF (2b) (Fig. 2) in which the metal is in a regular octahedral environment and the ligand is [N3 ] coordinated (Table 3). The complex crystallizes in the cubic space group Pa3 and the zinc atom lies on an inversion
(2b) Zn–N2 2.153(3) N2–Zn–N20 85.81(14) Symmetry transformation used to generate equivalent atoms: Ô ¼ y þ 1=2, z þ 1=2, x þ 1 (3a) 86.2(2) Co–N2 2.123(4) N2–Co–N20 Symmetry transformation used to generate equivalent atoms: Ô ¼ y þ 1=2, z þ 1=2, x þ 1 (4a) Ni–N21 Ni–N22 Ni–N23
2.112(6) 2.095(6) 2.068(6)
N21–Ni–N22 N21–Ni–N23 N22–Ni–N23
88.9(2) 87.2(2) 87.1(2)
(5) 89.07(2) Bi–S 2.8102(9) S–Bi–S0 Symmetry transformation used to generate equivalent atoms: Ô ¼ x þ y, x, z
Fig. 2. ORTEP drawing of 2b. Thermal ellipsoids are drawn at the 30% probability level.
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center and on a C3 axis; the complex has a S6 crystallographic and pseudo D3d symmetry. The six-membered chelate rings present a boat conformation. The Zn–N bond length and the ligand bite angle (2.148(2) A) (86.0(1)°) are in accordance with the corresponding val and ues found for the [Zn(Tp)2 ] complex (2.115–2.265 A 83.94–99.89°) [27]. The phenyl ring is perpendicular to the triazoline one (89.3(2)°) and is directed outward from the metal center. The 2b crystals were air sensitive and they rapidly break up once exposed to the air. The X-ray analysis has revealed the presence of large cavities that run parallel to the crystallographic axes. They are filled with severely disordered DMF solvation molecules weakly interacting with the zinc complexes. The packing diagrams are shown in Fig. 3. The cobalt complex 3 has been recrystallized in DMF and the X-ray structure determination showed that the complex 3a is isostructural to the zinc complex 2b
displaying a coordinative situation similar to the octahedral Co(II) complexes of the Tp ligand class [28]. Similarly to 2b, the phenyl and triazoline rings are nearly perpendicular to each other (87.2(2)°). X-ray quality crystals of 4 were obtained from a DMSO solution and the complex, which crystallizes in the P 1 space group, could be formulated as [Ni(TrPh;Me )2 ] H2 O 6DMSO (4a) (Fig. 4). The metal lies on an inversion center and is in a regular octahedral environment bound by six triazoline nitrogen atoms as found for the zinc complex 2b. Also in this case, the sixmembered chelate rings are in the boat conformation. The Ni–N bond lengths [2.068(6), 2.095(6), and 2.112(6) and the ligand bite angles [87.1(2)°, 87.2(2)°, and A] 88.9(2)°] (Table 3) show the almost symmetric environment of the metal and are in accordance with the geometric parameters found for the [Ni(Tp)2 ] complex and 85.01–95.00°) [29]. The phenyl rings (2.048–2.178 A are not perpendicular to the triazoline planes (range 67.3(3)–85.3(3)°) and, as for 2b and 3a, they do not interfere with the coordination environment. The crystal packing has shown the presence of large cavities hosting disordered solvation molecules (DMSO and H2 O). Two of the three independent methyl groups exchange hydrogen bonds with the oxygen atoms of the solvate molecules. The complex presents a pseudo D3d symmetry and the projection of the structure along the [1 )1 )1] direction shows great similarities with the crystal packing of 2b (the [1 )1 )1] direction corresponds to the pseudo-C 3 axis of the complex), Fig. 5. The crystal structure of the [Bi(TrPh;Me )]þ complex (Fig. 6) shows an octahedral coordination in which
Fig. 3. Crystal packing of 2b. Unit cell content of 2b, projection along the C3 crystallographic axis (a); projection along a (b).
Fig. 4. ORTEP drawing of 4a. Thermal ellipsoids are drawn at the 30% probability level.
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Fig. 5. Crystal packing of 4a. Unit cell content of 4a, projection along the pseudo-C3 axis ([1 )1 )1] direction) (a); Projection along a (b).
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lographic symmetry. The tripodal ligand forms eightmembered chelate rings exhibiting a boat conformation (adopting the same criterion used for 2a) and a propellerlike disposition of the triazoline rings that form dihedral angles of 88.9(1)°. The phenyl and triazoline rings are not coplanar forming a dihedral angle of 71.5(1)°. The two tripodal ligands closely envelop the metal atom with the six phenyl rings interlocking one after the other, in fact the C7–C8 bonds lie roughly in the plane perpendicular to the C3 axis passing through the Bi atom. Worthy of note is the interaction between the sulfur atom and the C1 and N1 atoms of an adjacent triazoline ring that can be defined The as p interaction (S C1 3.245(4), S N1 3.154(3) A). Bi–S bond distance (2.810(1) A) (Table 3) is comparable to those found in [Bi(Tt)2 ]Cl, [Bi(TrEt;Me )2 ]NO3 (range: and in the complex cation of 2.744(3)–2.836(3) A) [Bi(Tm)2 ][Na(Tp)2 ], the only similar complex found at the The liCCDC Cambridge database (UK) [30] (2.816 A). gand displays the [S3 ] mode, despite the presence of the phenyl ring close to C@S; it can be argued that the long Bi–S distances and the propeller arrangement of the ligand prevent any steric influences from the phenyl rings. Packing is determined by van der Waals interactions and by hydrogen bonds between a methyl H atom, a phenyl H atom and the oxygen atoms of the disordered NO 3 anion. In all compounds the phenyl and triazoline rings are nearly perpendicular owing to the presence of C@S and CH3 vicinal groups on the triazoline ring, so that the steric hindrance determined by the phenyl ring is displaced from C@S and constrained to be in a plane approximately perpendicular to the triazoline ring. In conclusion, for TrPh;Me , it can be argued that the rigid and flat nature of the phenyl ring poorly influence the C@S donor ability towards the metals. Moreover, no steric effect is exhibited by the rings when TrPh;Me binds in the [N3 ] mode. The presence of hydrogen bonds between the methyl groups and acceptor atoms of solvate molecules in 2a, 4a, and 5 is in accordance with the relatively high chemical shifts of the methyl hydrogen atoms in the 1 H NMR spectra. In order to investigate the role of the solvent in the molecular structures of 2, 1 H NMR spectra have been recorded in different solvents (Section 2). The complexity of the spectrum recorded in CD3 CN agrees with the non-symmetrical structure obtained from the crystals grown from this solvent (2a). On the other hand, 1 H NMR spectra recorded in CDCl3 and DMF-d7 reflect the high symmetry presented by the crystal structure of 2b.
Fig. 6. ORTEP drawing of 5. Thermal ellipsoids are drawn at the 30% probability level.
4. Supplementary material
the ligands behave as [S3 ] donors as it has already been reported for the complexes [Bi(Tt)2 ]Cl [7] and [Bi(TrEt;Me )2 ]NO3 [23]. The complex presents S6 crystal-
Listings of atomic coordinates of the non-hydrogen and hydrogen atoms, anisotropic displacement parameters and bond lengths and angles for 2a, 2b, 3a, 4a, and 5
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are given in the supplementary materials. CCDC219849-219853 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html or from the Cambridge Crystallographic Data Center, 12 Union Road, CB2 1EZ, UK [Fax: (internat.) +44-1223/336-033; e-mail: [email protected]].
Acknowledgements This work was supported by the Ministero dellÕIstruzione, dellÕUniversit a e Ricerca (Rome, Italy). Thanks are also due to Daniele Belletti, Andrea Cantoni and Gianfranco Pasquinelli for technical assistance during X-ray data collection.
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[16] A. Altomare, M.C. Burla, M. Camalli, G.L. Cascarano, C. Giacovazzo, A. Guagliardi, A.G.G. Moliterni, G. Polidori, R. Spagna, J. Appl. Crystallogr. 32 (1999) 115. [17] G.M. Sheldrick, S H E L X 97. Programs for Crystal Structure Analysis, University of G€ ottingen, Germany, 1997 (Release 97-2). [18] L.J. Farrugia, J. Appl. Crystallogr. 32 (1999) 837. [19] S Q U E E Z E – Sluis P.v.d., Spek A.L. Acta Cryst. A, 46 (1990) 194. [20] M. Nardelli, Comput. Chem. 7 (1983) 95. [21] M. Nardelli, J. Appl. Crystallogr. 28 (1995) 659. [22] L.J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565. [23] M. Careri, L. Elviri, M. Lanfranchi, L. Marchi o, C. Mora, M.A. Pellinghelli, Inorg. Chem. 42 (2003) 2019. [24] (a) C. Kimblin, B.M. Bridgewater, D.G. Churchill, T. Hascall, G. Parkin, Inorg. Chem. 39 (2000) 4240; (b) I.W. Nowell, A.G. Cox, E.S. Raper, Acta Crystallogr., Sect. B 35 (1979) 3047; (c) M. Tesmer, M. Shu, H. Vahrenkamp, Inorg. Chem. 40 (2001) 4022; (d) C.M.V. Stalhandske, C.I. Stalhandske, M. Sandstrom, I. Persson, Inorg. Chem. 36 (1979) 1997; (e) A. Wilk, M.A. Hitchman, W. Massa, D. Reinen, Inorg. Chem. 32 (1993) 2483; (f) R. Vega, A. Lopez-Castro, R. Marquez, Acta Crystallogr., Sect. B 34 (1978) 2297; (g) M. Bridgewater, T. Fillebeen, R.A. Friesner, G. Parkin, J. Chem. Soc., Dalton Trans. (2000) 4494. [25] F.A. Cotton, G. Wilkinson, Advanced Inorganic Chemistry, Wiley-Interscience Publications, 1988. [26] R. Cammi, M. Lanfranchi, L. Marchi o, C. Mora, C. Paiola, M.A. Pellinghelli, Inorg. Chem. 42 (2003) 1769. [27] (a) C. Janiak, H. Hemling, J. Chem. Soc., Dalton Trans. (1994) 2947; (b) G.G. Lobbia, B. Bovio, C. Santini, C. Pettinari, F. Marchetti, Polyhedron 16 (1997) 671; (c) Ke-Wu Yang, Yong-Zhen Wang, Zhong-Xian Huang, Jie Sun, Polyhedron 16 (1997) 1297; (d) C. Janiak, S. Temizdemir, S. Dechert, W. Deck, F. Girgsdies, J. Heinze, M.J. Kolm, T.G. Scharmann, O.M. Zipffel, Eur. J. Inorg. Chem. (2000) 1229; (e) A. Looney, R. Han, I.B. Gorrell, M. Cornebise, Keum Yoon, G. Parkin, A.L. Rheingold, Organometallics 14 (1995) 274; (f) K. Nakata, S. Kawabata, K. Ichikawa, Acta Crystallogr., Sect. C (Cr. Str. Comm.) 51 (1995) 1092. [28] (a) M.R. Churchill, K. Gold, C.E. Maw Jr., Inorg. Chem. 9 (1970) 1597; (b) S. Trofimenko, J.C. Calabrese, P.J. Domaille, J.S. Thompson, Inorg. Chem. 28 (1989) 1091; (c) J.C. Calabrese, P.J. Domaille, S. Trofimenko, G.J. Long, Inorg. Chem. 30 (1991) 2795; (d) A.L. Rheingold, L.M. Liable-Sands, S. Trofimenko, Inorg. Chem. 39 (2000) 1333; (e) A.L. Rheingold, B.S. Haggerty, G.P.A. Yap, S. Trofimenko, Inorg. Chem. 36 (1997) 5097; (f) A.L. Rheingold, B.S. Haggerty, G.P.A. Yap, S. Trofimenko, Inorg. Chem. 36 (1997) 5097; (g) A.L. Rheingold, G.P. Yap, L.M. Liable-Sands, I.A. Guzei, S. Trofimenko, Inorg. Chem. 36 (1997) 6261; (h) M. Ruf, B.C. Noll, M. Groner, G.T. Yee, C.G. Pierpont, Inorg. Chem. 36 (1997) 4860; (i) C. Janiak, S. Temizdemir, S. Dechert, W. Deck, F. Girgsdies, J. Heinze, M.J. Kolm, T.G. Scharmann, O.M. Zipffel, Eur. J. Inorg. Chem. (2000) 1229; (j) C. Janiak, Chem. Commun. (1994) 545; (k) J. Huang, L. Lee, B.S. Haggerty, A.L. Rheingold, M.A. Walters, Inorg. Chem. 34 (1995) 4268. [29] (a) J.C. Calabrese, P.J. Domaille, J.S. Thompson, S. Trofimenko, Inorg. Chem. 29 (1990) 4429;
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(f) C. Janiak, S. Temizdemir, S. Dechert, Inorg. Chem. Commun. 3 (2000) 271; (g) P. Cecchi, G.G. Lobbia, F. Marchetti, G. Valle, S. Calogero, Polyhedron 13 (1994) 2173; (h) C. Janiak, T.G. Scharmann, H. Hemling, D. Lentz, J. Pickardt, Chem. Ber. 128 (1995) 235. [30] J. Reglinski, M.D. Spicer, M. Gardner, A.R. Kennedy, J. Am. Chem. Soc. 121 (1999) 2317.
[S2], [S3], and [N3] coordination modes of hydrotris(thioxotriazolyl)borato. Zinc, nickel, cobalt, and bismuth complexes q *, Clara Mora, Maria Angela Pellinghelli Maurizio Lanfranchi, Luciano Marchio Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Universit a degli Studi di Parma, Parco Area delle Scienze 17a, I 43100 Parma, Italy Received 22 January 2003; accepted 11 June 2003
Abstract The ligand hydrotris(1,4-dihydro-3-methyl-4-phenyl-5-thioxo-1,2,4-triazolyl)borato (TrPh;Me ) was synthetized as natrium salt and the complexes [Zn(TrPh;Me )2 ] 7.5H2 O 1.5CH3 CN (2a), [Zn(TrPh;Me )2 ] 8DMF (2b), [Co(TrPh;Me )2 ] 8DMF (3a), [Ni(TrPh;Me )2 ] H2 O 6DMSO (4a), [Bi(TrPh;Me )2 ]NO3 (5), have been isolated and structurally characterized by X-ray diffraction. In the zinc derivatives the ligand adopts different denticity and coordination modes, g2 and [S2 ] for 2a and g3 and [N3 ] for 2b, depending on the crystallization solvent, giving rise to tetrahedral and octahedral geometry, respectively. In the octahedral cobalt and nickel complexes the ligand is g3 and [N3 ] coordinated whereas in the bismuth complex the g3 and [S3 ] coordination is exhibited. Ó 2003 Elsevier B.V. All rights reserved. Keywords: Substituted tristriazolylborates; Zinc; Cobalt; Nickel; Bismuth
1. Introduction The realm of boron centered tripodal ligands includes a great number of compounds that are mainly differentiated by the donor capability of the heterocyclic rings linked to the boron center. The Tp ([N3 ] coordination mode) [1] and Tm ([S3 ] coordination mode) [2] ligand classes have been extensively used as models for zinc enzyme [3,4], and in order to better mimic the alcohol dehydrogenase active sites, the mixed ligands [pzBm] ([S2 N] coordination mode, displaying pyrazole and thioxoimidazole rings) have been employed [5,6]. A different approach has been followed with the synthesis of the hydrotris(1,4-dihydro-3-R0 -4-R-5-thioxo-1,2,4-triazolyl)0 borato ligands (TrR;R ) 1 as they bear on each triazoline ring a nitrogen atom and a C@S group and can act as q
Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.ica.2003.06.004. * Corresponding author. Tel.: +39-521-905424; fax: +39-521-905557. E-mail address: [email protected] (L. Marchi o). 1 The apex indicates the substituents on the thioxotriazolinyl rings. The first fragment is relative to the substituent on the N4 nitrogen atom whereas the second is for the substituent on the C3 carbon atom. 0020-1693/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2003.06.004
[S3 ] and [N3 ] donors towards metal ions [7]. They are able to satisfy the coordination requirements of hard and soft metal ions and allow tetrahedral or octahedral coordination geometries. We are currently examining their coordination chemistry with various metal ions and we are presently investigating the effect that the steric hindrance, in proximity to the C@S and nitrogen atoms, may play on the coordination properties of these ligands. Placing a phenyl group close to C@S could limit the accessibility of the [S3 ] coordination mode in favor of the less encumbered [N3 ] mode in [M(L)2 ]ðn 2Þþ octahedral complexes. The steric hindrance for the Tp, Tm, and [pzBm] ligands has been used as a tetrahedral enforcer in order to favor the tetrahedral geometry of zinc complexes and to better mimic the geometrical features of the alcohol dehydrogenase and carbonic anhydrase active sites [4,5,8]. In fact, many TpZn-X structures have been reported where the steric hindrance on the pyrazole 3position forces a tetrahedral geometry [9] and only one example of an octahedral zinc complex is reported where the bulkiness of the pyrazole substituents does not seem to interfere with the coordination geometry [10].
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product is collected (1.961 g, 45%). Anal. Calc for C27 H25 BN9 S3 Na: C, 53.55; H, 4.16; N, 20.82. Found: C, 53.17; H, 4.32; N, 20.46%. IR data (KBr disks cm1 ): 3063m, 2926m, 2551w [m(B–H)], 1578s, 1499s, 1415s, 1382m, 1324s, 1274s, 1130m, 1014m, 698m, 565m. 1 H NMR (300 MHz, D2 O): 2.28 (s, 3H, CH3 ), 7.54 ppm (m, 2H, Ph), 7.75 ppm (m, 3H, Ph). 2.2. [Zn(TrPh;Me )2 ] (2)
Scheme 1.
In this paper we report the syntheses and structures of TrPh; Me (Scheme 1) derivatives of zinc, nickel, cobalt, and bismuth in the molar ratio 2:1. In the case of the zinc complex, two structures are obtained whereby the metal is in a tetrahedral and octahedral geometry and the ligand exhibits [S2 ] and [N3 ] binding modes, respectively.
2. Experimental All solvents and reagents are commercially available (Sigma–Aldrich) and were used as received. The 1 H NMR spectra were recorded on a Bruker AC 300 spectrometer operating at room temperature. Chemical shifts are reported in ppm referenced to residual solvent protons (DMSO-d6 , DMF-d7 , D2 O, CDCl3 ). Mass spectra were obtained with a Finnigan 1020 mass spectrometer in positive ion mode with a MATSS 710 quadrupole. Infrared spectra were recorded using KBr pellets from 4000 to 400 cm1 on a Perkin–Elmer FT-IR Nexus spectrometer. Elemental analysis (C, H, N) was performed with a Carlo Erba EA 1108 automated analyser. The compound 1,4-dihydro-3-methyl-4-phenyl-5thioxo-1,2,4-triazole has been prepared according to published procedures [11,12]. 2.1. [Na(TrPh;Me )] (1) 1,4-Dihydro-3-methyl-4-phenyl-5-thioxo-1,2,4-triazole (5.29 g, 27.6 mmol) and sodium tetrahydroborate (0.270 g, 7.13 mmol) were mixed together in a 100 ml round-bottomed flask fitted to a volumetric device for measuring hydrogen evolution. Upon stirring, the temperature was raised gently to 230 °C whereupon evolution of hydrogen gas began. The mixture melted at this temperature which was maintained for 1.5 h. The reaction mixture was allowed to cool to room temperature. The resulting yellow glassy solid was then inserted in the thimble of a soxhlet apparatus and washed with chloroform for 6 h. From the thimble, a powdery white
A mixture of ZnSO4 7H2 O (0.110 g, 0.383 mmol) and 1 (0.460 g, 0.760 mmol) was heated to reflux in methanol (100 ml) for 6 h. The solvent was removed under vacuum from the resulting white suspension. The pale yellow powder was suspended in water (30 ml) and filtered. The pale yellow product was then collected (0.406 g, 86%). Anal. Calc for C54 H50 N18 S6 B2 Zn: C, 52.71; H, 4.10; N, 20.49. Found: C, 52.21; H, 4.45; N, 20.28%. IR data (KBr disk, cm1 ): 3063m, 2927m, 2497w [m(B–H)], 1576m, 1499s, 1414s, 1383s, 1328s, 1279s, 1015m, 835m, 697m. 1 H NMR (300 MHz, CDCl3 ): 2.06 ppm (s, 3H, CH3 ), 7.17 ppm (m, 2H, Ph), 7.44 ppm (m, 3, Ph); 1 H NMR (300 MHz, DMF-d7 ): 2.24 ppm (s, 3H, CH3 ), 7.39 ppm (m, 2H, Ph), 7.58 (m, 3H, Ph). 1 H NMR (300 MHz, CH3 CN-d3 ): 2.42 ppm (m, 3H, CH3 ), 7.29–7.65 ppm (m, 5H, Ph). The product was recrystallized from an acetonitrile/water solution and from a DMF solution from which two crystal types suitable for X-ray structure determination were obtained ([Zn(TrPh;Me )2 ] 7.5H2 O 1.5CH3 CN (2a) in acetonitrile/water and [Zn(TrPh;Me )2 ] 8DMF (2b) in DMF). 2.3. [Co(TrPh;Me )2 ] (3) CoCl2 6H2 O (0.060 g, 0.252 mmol) was dissolved in water (15 ml) and was added to a suspension (20 ml) of 1 (0.320 g, 0.528 mmol) in the same solvent. The mixture instantly became pale pink and was stirred at room temperature for 4 h. The solvent was then removed by filtration and the pink powder was collected (0.293 g, 95%). Anal. Calc for C54 H50 N18 S6 B2 Co: C, 52.99; H, 4.12; N, 20.60. Found: C, 52.38; H, 3.78; N, 19.96%. IR data (KBr disk, cm1 ): 3062m, 2927w, 2568w [m(B–H)], 1590m, 1580m, 1498s, 1414s, 1383s, 1323m, 1224m, 819m, 693m. Recrystallization of the pink powder from a DMF solution gave yellow crystals suitable for X-ray analysis corresponding to [Co(TrPh;Me )2 ] 8DMF (3a). 2.4. [Ni(TrPh;Me )2 ] (4) A mixture of NiCl2 6H2 O (0.070 g, 0.295 mmol) and 1 (0.370 g, 0.611 mmol) was stirred at room temperature in methanol (40 ml) for 7 h. The initially green solution turned to yellow after a few hours. The solvent was
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removed under vacuum and the yellow powder was dissolved in acetonitrile (30 ml). The mixture was filtered, the solvent was removed under vacuum and a green product was collected (0.322 g, 89%). Anal. Calc for C54 H50 B2 N18 S6 Ni: C, 53.00; H, 4.12; N, 20.60. Found: C, 52.13; H, 4.45; N, 20.13%. IR (KBr disk, cm1 ): 3062w, 2965w, 2926w, 2601w, 1593s, 1567s, 1498s, 1417s, 1380s, 1272s, 1129s, 1020s, 823m, 698m. Suitable crystals for X-ray structure determination were obtained from a DMSO solution corresponding to [Ni(TrPh;Me )2 ] H2 O 6DMSO (4a). 2.5. [Bi(TrPh; Me )2 ]NO3 (5) Bi(NO3 )3 5H2 O (0.084 g, 0.232 mmol) was dissolved in methanol (15 ml) and was added to a methanolic (30 ml) solution of 1 (0.281 g, 0.464 mmol). The mixture turned red instantly. The solution was stirred at room temperature for 4 h. The solvent was then removed under vacuum, the red powder was washed with water (30 ml) and collected (0.315 g, 72%). IR data (KBr disk, cm1 ): 3061m, 2927m, 2520m [m(B–H)], 1567m, 1498m, 1427m, 1384s, 1325m, 1276m, 693m. 1 H NMR (300 MHz, DMSO-d6 ): 2.14 (s, 3H, CH3 ), 7.36 ppm (m, 2H, Ph), 7.55 ppm (m, 3H, Ph). Anal. Calc for C54 H50 B2 N19 O3 S6 Bi: C, 45.16; H, 3.51; N, 18.53. Found: C, 44.88; H, 2.99; N, 18.83%. Recrystallization of the reddish powder from an acetonitrile/water solution gave red crystals suitable for X-ray analysis corresponding to [Bi(TrPh;Me )2 ]NO3 .
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2.6. X-ray crystallography A summary of data collection and structure refinement is reported in Tables 1 and 2. Single crystal data were collected with an Enraf-Nonius CAD4 diffractom for 2a, and 4a, with a eter (Cu Ka; k ¼ 1:541838 A) Bruker AXS Smart 1000 area detector diffractometer for 2b and 3a and with a (Mo Ka; k ¼ 0:71073 A) Philips PW 1100 diffractometer (Mo Ka; k ¼ 0:71073 A) for 5. Empirical absorption correction was applied using the program X A B S 2 [13] for 2a and 4a, the program S A D A B S [14] for 2b and 3a and the Psi-scan semiempirical method [15] for 5 (max. and min. absorption correction coefficients: 1.000, 0.376 (2b); 1.000, 0.201 (2a); 1.000, 0.815 (3a); 1.000, 0.633 (4a); 1.000, 0.784 (5)). These structures were solved by direct methods (SIR97) [16] and refined with full-matrix least-squares (S H E L X L -97) [17], using the Wingx software package [18]. Non-hydrogen atoms were refined anisotropically; H atoms were found and refined for the BH groups of 4a and 5. The remaining H atoms were placed at their calculated positions. The nitrate ion of 5 was found to be disordered and distributed in 12 positions each with an occupancy factor of 0.083. DMF solvent molecules in 2b and 3a were severely disordered and were treated using the S Q U E E Z E P L A T O N program [19]. In the asymmetric unit of 4a, three DMSO solvent molecules and a water molecule with an occupancy factor of 0.5 were found whereas for each asymmetric unit of 2a, 1.5 acetonitrile solvent molecules and 7.5 water molecules
Table 1 Summary of X-ray crystallographic data for 2a and 2b
Empirical formula Formula weight Colour, habit Crystal size, mm Crystal system Space group a (A) b (A) c (A)
(2a)
(2b)
C57 H69:50 B2 N19:50 O7:50 S6 Zn 1427.17 colourless, block 0.40 0.39 0.13 triclinic P1 11.956(8) 14.397(5) 22.927(13) 72.93(2) 75.04(2) 85.19(2) 3645(3) 2 1488 Cu Ka (1.54184) 293 1.300 2.580 3.21–55.00 9130/9130 0.0690 0.1760 0.512 and )0.428
C78 H106 B2 N26 O8 S6 Zn 1815.24 colourless, block 0.30 0.30 0.30 cubic Pa3 21.170(7) 21.170(7) 21.170(7) 90 90 90 9488(5) 4 3824 Mo Ka (0.71073) 293 1.271 0.455 1.92–24.02 16,079/2487 0.0436 0.0689 0.125 and )0.173
a (°) b (°) c (°) 3 ) V (A Z F (0 0 0) Radiation (k (A)) T (K) qcalc (Mg/m3 ) l (mm1 ) h range, (°) Number of reflections/observed F > 4rðF Þ R1 wR2 3 ) Largest difference peak/hole (e A P P P P R1 ¼ jjFo j jFc jj= jFo j, wR2 ¼ ½ ½wðFo2 Fc2 Þ2 = ½wðFo2 Þ2 1=2 , w ¼ 1=½r2 ðFo2 Þ þ ðaP Þ2 þ bP , where P ¼ ½maxðFo2 ; 0Þ þ 2Fc2 =3.
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Table 2 Summary of X-ray crystallographic data for 3a, 4a and 5 (3a)
(4a)
(5)
Empirical formula Formula weight Colour, habit Crystal size (mm) Crystal system Space group a (A) b (A) c (A)
C78 H106 B2 CoN26 O8 S6 C66 H88 B2 N18 NiO7 S12 C54 H50 B2 BiN19 O3 S6 1808.80 1710.59 1436.09 yellow, block green, block red, block 0.35 0.35 0.27 0.25 0.20 0.15 0.35 0.28 0.21 cubic triclinic rhombohedral Pa3 P1 R3 21.219(4) 11.978(7) 14.516(3) 21.219(4) 12.445(3) 14.516(3) 21.219(4) 14.484(8) 25.240(5) a (°) 90 102.95(3) 90 b (°) 90 95.68(4) 90 c (°) 90 96.74(3) 120 3 ) V (A 9554(3) 2072(2) 4606(2) Z 4 1 3 F (0 0 0) 3812 869 2160 Radiation (k, A) Mo Ka (0.71073) Cu Ka (1.54184) Mo Ka (0.71073) T (K) 293 173 293 qcalc (Mg/m3 ) 1.258 1.371 1.553 0.375 3.654 3.135 l (mm1 ) h range (°) 1.92–21.99 3.16–62.49 3.61–25.05 Number of reflections/observed F > r4ðF Þ 14,628/1955 6378/6378 5399/1814 R1 0.0453 0.0687 0.0279 wR2 0.0649 0.1853 0.0369 3 ) Largest difference peak/hole (e A 0.141 and )0.124 0.405 and )0.670 0.253 and )0.284 P P P P 2 2 2 2 2 2 1=2 2 2 2 R1 ¼ jjFo j jFc jj= jFo j, wR2 ¼ ½ ½wðFo Fc Þ = ½wðFo Þ , w ¼ 1=½r ðFo Þ þ ðaP Þ þ bP , where P ¼ ½maxðFo ; 0Þ þ 2Fc2 =3.
were present. The programs P A R S T [20,21] and O R T E P for Windows [22] were also used. Full tables of bond lengths and angles, atomic positional parameters, isotropic and anisotropic displacement parameters are given in the supplementary material.
The complexes have been synthesized by metathesis by reacting (in methanol for 2, 4, and 5 and in water for 3) suitable inorganic salt of the metals and 1. They are insoluble in water and can be purified washing the reaction powder with this solvent. 3.1. Molecular structures
3. Results and discussion It has been shown that in the [Cu(TrEt;Me )]2 and [Bi(TrEt;Me )2 ]NO3 complexes the ethyl groups close to the C@S adopt a conformation in which they are perpendicular to the triazoline rings and this results in their limited ability to function as hindering group for the thioxo moiety [23]. This prompted us to increase the steric bulk of the substituent on the N4 triazoline atom, (Scheme 1). Placing the phenyl group in close proximity to the C@S could limit the accessibility of the [S3 ] coordination mode in [M(TrPh;Me )2 ]ðn 2Þþ complexes and could consequently hinder the occurrence of the octahedral geometry if the ligand binds through the thioxo groups. On the contrary, the less encumbered methyl group close to the triazoline nitrogen atoms would not prevent the occurrence of the [N3 ] coordination mode for [M(TrPh;Me )2 ]ðn 2Þþ octahedral complexes as it was found in the [Na(Tt)2 ]þ cation [7]. In this were the case, the phenyl groups would point away from the coordination center and would not affect the coordination geometry.
For the crystals of 2 obtained from the acetonitrile/ water solution, the solvent enters the crystal lattice and the complex was formulated as [Zn(TrPh;Me )2 ] 7.5H2 O 1.5CH3 CN (2a), Fig. 1. The metal is in a distorted tetrahedral geometry and the ligand behaves as bidentate [S2 ]. The Zn–S distances range from 2.310(3) to 2.381(3) and the bond angles from 97.71(9)° to 119.21(10)° A (Table 3) in accordance with the value reported for and 85.58– similar thionic compounds (2.258–2.413 A 121.55°) [24]. Noteworthy is the fact that for each tripodal ligand, one of the triazoline rings does not participate in the coordination, a situation previously reported for [Zn(Ttt-Bu )2 ] [4]. In this latter case the metal adopts a tetrahedral coordination despite the presence of a relatively small encumbering group such as methyl close to the C@S. It is possible that the phenyl ring in TrPh;Me does not have any effect in dictating the coordination geometry around zinc in 2a but this could be a consequence of a natural tendency for Zn(II) to adopt a Zn[S4 ] coordination geometry as it was suggested for [Zn(Ttt-Bu )2 ]. The ligands could also act as tridentate
M. Lanfranchi et al. / Inorganica Chimica Acta 357 (2004) 367–375
Fig. 1. ORTEP drawing of 2a. Thermal ellipsoids are drawn at the 30% probability level.
[S2 N] but the preferred tetrahedral geometry of the zinc(II) cation [25] prevents the additional coordination of the triazoline nitrogen atoms. An analogous scenario was exhibited for [pzBmMe ]2 Zn in which the pyrazolyl ‘‘arm’’ of the tripodal ligand does not bind the metal [6]. It is not excluded that for these ZnS4 motifs, the coorTable 3 and angles (°) with estimated standard deSelected bond lengths (A) viations in parentheses for compounds 2a, 2b, 3a, 4a, and 5 (2a) Zn–S1 Zn–S2 Zn–S4 Zn–S5
2.381(3) 2.310(3) 2.339(3) 2.335(2)
S1–Zn–S2 S1–Zn–S4 S1–Zn–S5 S2–Zn–S4 S2–Zn–S5 S4–Zn–S5
109.21(9) 97.71(9) 108.82(9) 119.22(10) 110.62(10) 110.22(9)
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dinated thioxo groups provide sufficient electron density to satisfy the zinc demand limiting the coordination to tetrahedral. In 2a, the two eight-membered chelate rings can be considered equivalent to a six-membered one because the triazoline rings are planar and the S and B atoms lie in this plane. The centroid of each triazoline ring can be considered occupying a vertex of the sixmembered ring as it was proposed for the ligand BtEt;Me [26]. In this context the conformation is boat for both chelating rings with the apices occupied by a sulfur atom and a triazoline centroid. In both chelating ring systems the separation between a coordinated sulfur atom and the opposite C1 and N1 atoms is less than the sum of the van der Waals radii (S1 C12, 3.28(1); S1 N12, and can 3.19(1); S4 C15, 3.36(1); S4 N15, 3.22(1) A) be defined, from geometrical consideration, as a p interaction. In the boat containing B1 the uncoordinated triazoline ring occupies an equatorial position whereas in the boat containing B2, an axial one. As reported for [Cu(TrEt;Me )]2 [23], of the two ligands, the one containing B1 exhibits an ‘‘inverted’’ conformation (with two of the C@S surrounding the B–H group) and the B1–H1 points toward the metal even though the Zn H1 separation is too long for a possible Zn H–B inter(3.554(2) A) action whereas the ligand containing B2 is in a ‘‘normal’’ conformation with the B–H pointing away from the metal. The dihedral angles between the triazoline rings and the phenyl groups attached to them range from 68.6(5) to 87.7(4)°. Apart from N26, which interacts with the other the coordinated S2 atom (S2 N26, 3.28(1) A), iminic nitrogen atoms are involved in hydrogen bonds with solvation water molecules. Recrystallization of 2 from a DMF solution gave the complex that could be formulated as [Zn(TrPh;Me )2 ] 8DMF (2b) (Fig. 2) in which the metal is in a regular octahedral environment and the ligand is [N3 ] coordinated (Table 3). The complex crystallizes in the cubic space group Pa3 and the zinc atom lies on an inversion
(2b) Zn–N2 2.153(3) N2–Zn–N20 85.81(14) Symmetry transformation used to generate equivalent atoms: Ô ¼ y þ 1=2, z þ 1=2, x þ 1 (3a) 86.2(2) Co–N2 2.123(4) N2–Co–N20 Symmetry transformation used to generate equivalent atoms: Ô ¼ y þ 1=2, z þ 1=2, x þ 1 (4a) Ni–N21 Ni–N22 Ni–N23
2.112(6) 2.095(6) 2.068(6)
N21–Ni–N22 N21–Ni–N23 N22–Ni–N23
88.9(2) 87.2(2) 87.1(2)
(5) 89.07(2) Bi–S 2.8102(9) S–Bi–S0 Symmetry transformation used to generate equivalent atoms: Ô ¼ x þ y, x, z
Fig. 2. ORTEP drawing of 2b. Thermal ellipsoids are drawn at the 30% probability level.
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center and on a C3 axis; the complex has a S6 crystallographic and pseudo D3d symmetry. The six-membered chelate rings present a boat conformation. The Zn–N bond length and the ligand bite angle (2.148(2) A) (86.0(1)°) are in accordance with the corresponding val and ues found for the [Zn(Tp)2 ] complex (2.115–2.265 A 83.94–99.89°) [27]. The phenyl ring is perpendicular to the triazoline one (89.3(2)°) and is directed outward from the metal center. The 2b crystals were air sensitive and they rapidly break up once exposed to the air. The X-ray analysis has revealed the presence of large cavities that run parallel to the crystallographic axes. They are filled with severely disordered DMF solvation molecules weakly interacting with the zinc complexes. The packing diagrams are shown in Fig. 3. The cobalt complex 3 has been recrystallized in DMF and the X-ray structure determination showed that the complex 3a is isostructural to the zinc complex 2b
displaying a coordinative situation similar to the octahedral Co(II) complexes of the Tp ligand class [28]. Similarly to 2b, the phenyl and triazoline rings are nearly perpendicular to each other (87.2(2)°). X-ray quality crystals of 4 were obtained from a DMSO solution and the complex, which crystallizes in the P 1 space group, could be formulated as [Ni(TrPh;Me )2 ] H2 O 6DMSO (4a) (Fig. 4). The metal lies on an inversion center and is in a regular octahedral environment bound by six triazoline nitrogen atoms as found for the zinc complex 2b. Also in this case, the sixmembered chelate rings are in the boat conformation. The Ni–N bond lengths [2.068(6), 2.095(6), and 2.112(6) and the ligand bite angles [87.1(2)°, 87.2(2)°, and A] 88.9(2)°] (Table 3) show the almost symmetric environment of the metal and are in accordance with the geometric parameters found for the [Ni(Tp)2 ] complex and 85.01–95.00°) [29]. The phenyl rings (2.048–2.178 A are not perpendicular to the triazoline planes (range 67.3(3)–85.3(3)°) and, as for 2b and 3a, they do not interfere with the coordination environment. The crystal packing has shown the presence of large cavities hosting disordered solvation molecules (DMSO and H2 O). Two of the three independent methyl groups exchange hydrogen bonds with the oxygen atoms of the solvate molecules. The complex presents a pseudo D3d symmetry and the projection of the structure along the [1 )1 )1] direction shows great similarities with the crystal packing of 2b (the [1 )1 )1] direction corresponds to the pseudo-C 3 axis of the complex), Fig. 5. The crystal structure of the [Bi(TrPh;Me )]þ complex (Fig. 6) shows an octahedral coordination in which
Fig. 3. Crystal packing of 2b. Unit cell content of 2b, projection along the C3 crystallographic axis (a); projection along a (b).
Fig. 4. ORTEP drawing of 4a. Thermal ellipsoids are drawn at the 30% probability level.
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Fig. 5. Crystal packing of 4a. Unit cell content of 4a, projection along the pseudo-C3 axis ([1 )1 )1] direction) (a); Projection along a (b).
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lographic symmetry. The tripodal ligand forms eightmembered chelate rings exhibiting a boat conformation (adopting the same criterion used for 2a) and a propellerlike disposition of the triazoline rings that form dihedral angles of 88.9(1)°. The phenyl and triazoline rings are not coplanar forming a dihedral angle of 71.5(1)°. The two tripodal ligands closely envelop the metal atom with the six phenyl rings interlocking one after the other, in fact the C7–C8 bonds lie roughly in the plane perpendicular to the C3 axis passing through the Bi atom. Worthy of note is the interaction between the sulfur atom and the C1 and N1 atoms of an adjacent triazoline ring that can be defined The as p interaction (S C1 3.245(4), S N1 3.154(3) A). Bi–S bond distance (2.810(1) A) (Table 3) is comparable to those found in [Bi(Tt)2 ]Cl, [Bi(TrEt;Me )2 ]NO3 (range: and in the complex cation of 2.744(3)–2.836(3) A) [Bi(Tm)2 ][Na(Tp)2 ], the only similar complex found at the The liCCDC Cambridge database (UK) [30] (2.816 A). gand displays the [S3 ] mode, despite the presence of the phenyl ring close to C@S; it can be argued that the long Bi–S distances and the propeller arrangement of the ligand prevent any steric influences from the phenyl rings. Packing is determined by van der Waals interactions and by hydrogen bonds between a methyl H atom, a phenyl H atom and the oxygen atoms of the disordered NO 3 anion. In all compounds the phenyl and triazoline rings are nearly perpendicular owing to the presence of C@S and CH3 vicinal groups on the triazoline ring, so that the steric hindrance determined by the phenyl ring is displaced from C@S and constrained to be in a plane approximately perpendicular to the triazoline ring. In conclusion, for TrPh;Me , it can be argued that the rigid and flat nature of the phenyl ring poorly influence the C@S donor ability towards the metals. Moreover, no steric effect is exhibited by the rings when TrPh;Me binds in the [N3 ] mode. The presence of hydrogen bonds between the methyl groups and acceptor atoms of solvate molecules in 2a, 4a, and 5 is in accordance with the relatively high chemical shifts of the methyl hydrogen atoms in the 1 H NMR spectra. In order to investigate the role of the solvent in the molecular structures of 2, 1 H NMR spectra have been recorded in different solvents (Section 2). The complexity of the spectrum recorded in CD3 CN agrees with the non-symmetrical structure obtained from the crystals grown from this solvent (2a). On the other hand, 1 H NMR spectra recorded in CDCl3 and DMF-d7 reflect the high symmetry presented by the crystal structure of 2b.
Fig. 6. ORTEP drawing of 5. Thermal ellipsoids are drawn at the 30% probability level.
4. Supplementary material
the ligands behave as [S3 ] donors as it has already been reported for the complexes [Bi(Tt)2 ]Cl [7] and [Bi(TrEt;Me )2 ]NO3 [23]. The complex presents S6 crystal-
Listings of atomic coordinates of the non-hydrogen and hydrogen atoms, anisotropic displacement parameters and bond lengths and angles for 2a, 2b, 3a, 4a, and 5
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are given in the supplementary materials. CCDC219849-219853 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html or from the Cambridge Crystallographic Data Center, 12 Union Road, CB2 1EZ, UK [Fax: (internat.) +44-1223/336-033; e-mail: [email protected]].
Acknowledgements This work was supported by the Ministero dellÕIstruzione, dellÕUniversit a e Ricerca (Rome, Italy). Thanks are also due to Daniele Belletti, Andrea Cantoni and Gianfranco Pasquinelli for technical assistance during X-ray data collection.
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