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Silver compounds in synthetic chemistry
Journal of Fluorine Chemistry 127 (2006) 213–217 www.elsevier.com/locate/fluor
Silver compounds in synthetic chemistry Part 4. 4-Tetrafluoropyridyl silver(I), AgC5F4N in redox transmetallations— possibilities and limitations in reactions with group 15 elements§ Wieland Tyrra *, Said Aboulkacem, Berthold Hoge, Waldemar Wiebe, Ingo Pantenburg Institut fu¨r Anorganische Chemie, Universita¨t zu Ko¨ln, Greinstr. 6, D-50939 Ko¨ln, Germany Received 7 September 2005; received in revised form 10 October 2005; accepted 15 October 2005 Available online 18 January 2006
Abstract While reactions of AgC5F4N with elemental arsenic, antimony, and bismuth proceed selectively yielding E(C5F4N)3 (E = As, Sb, Bi), those with white and red phosphorus remained obscure giving product mixtures of so far unknown stoichiometry. The phosphorus compound was therefore prepared by an alternative route. P(C5F4N)3 and As(C5F4N)3 crystallize isostructurally in the monoclinic space group P21/c (no. 14) with four molecules per unit cell. p–p Offset stacking together with edge-face stacking lead to dimeric units which are connected by a second edge-face stacking of nitrogen onto the opposite side of the same tetrafluoropyridyl ring extending the structure into infinite chains. # 2005 Elsevier B.V. All rights reserved. Keywords: 4-Tetrafluoropyridyl; Group 15; Synthesis; Crystal structure; p-Stacking
1. Introduction
2. Results and discussion
Oxidative properties of perfluoroorgano silver compounds have been outlined in some foregoing papers [1–4]. Reactions described therein had in common that perfluoroorgano element compounds of group 15 elements could be prepared more or less selectively for the heavier elements in moderate to good yields (As, Sb, Bi). In a recent publication, we showed that AgC5F4N [5] has comparable oxidative properties as AgC6F5 [1–4]. Additionally it has been shown by theoretical calculations [6] that the electron-withdrawing effect of the C5F4N ligand is even higher than that of the isolobal C6F5 group; the 4position is protected against unpredictable nucleophilic attack [7]. Herein, we offer a new selective approach for the syntheses of E(C5F4N)3 (E = As, Sb, Bi) starting from AgC5F4N and the corresponding elements. The low toxicity of silver, the ease of recycling together with the selectivity in redox transmetallations make silver compounds attractive for studies in the field of element organic synthesis [3].
2.1. Redox transmetallations of AgC5F4N and the pnicogens, phosphorus, arsenic, antimony, and bismuth
§
For Part 3 see [5]. * Corresponding author. Tel.: +49 221 470 3276; fax: +49 221 470 3276. E-mail address: [email protected] (W. Tyrra).
0022-1139/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jfluchem.2005.10.009
Redox transmetallations of AgC5F4N and arsenic, antimony and bismuth proceed in a similar manner as described for the group 12–14 elements [5] or for AgC6F5 and group 12–16 elements [4] (Eq. (1)).
(1)
Unfortunately, reactions with white and red phosphorus gave product mixtures which were not further identified. Therefore, P(C5F4N)3 was prepared alternatively by a literature procedure [8]. While As(C5F4N)3 was obtained as a colourless, crystalline material by common procedures, the extreme air and moisture sensitivity of Sb(C5F4N)3 and Bi(C5F4N)3 prevented from a full characterization. However, 19F NMR and mass spectra prove unambiguously the existence of both compounds.
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Table 1 Crystal data and structure refinement parameters for P(C5F4N)3 and As(C5F4N)3
Empirical formula Formula mass (g mol1) Data collection Diffractometer Radiation Temperature (K)
P(C5F4N)3
As(C5F4N)3
C15N3F12P 481.15
C15N3F12As 525.10 STOE IPDS II Mo Ka, l = 71.073 pm
170(2)
170(2)
Index range
14 h 14 15 k 15 19 l 19
14 h 14 16 k 16 18 l 18
Rotation angle range
08 v 1808; c = 08 08 v 288; c = 908
08 v 1808; c = 08 08 v 1808; c = 908
Increment No. of images Exposure time (min) Detector distance (mm) 2u range (8) Total data collected Unique data Observed data Rmerg Absorption correction Transmission min/max
Dv = 28 104 10 100 2.2–59.5 17397 4407 2234 0.0625
Dv = 28 180 5 100 2.2–59.5 32019 4641 3669 0.0426 Numerical, after crystal shape optimization [15,16] 0.8353/0.9638 0.4835/0.7332
Crystallographic data [22] Crystal size (mm) Colour, habit Crystal system Space group a (pm) b (pm) c (pm) b (8) Volume (106 pm3) Z rcalc (mg m3) m (mm1) F(0 0 0)
0.3 0.3 0.1 Colourless, plate Monoclinic P21/c (no. 14) 1041.0(2) 1133.1(2) 1390.6(2) 98.80(1) 1621.0(4) 4 1.972 0.311 936
Structure analysis and refinement Structure determination No. of variables
281
0.2 0.2 0.15 Colourless, polyhedron Monoclinic P21/c (no. 14) 1045.3(1) 1176.6(1) 1360.3(1) 98.74(1) 1653.7(2) 4 2.109 2.194 1008 SIR-92 [17] and SHELXL-97 [18] 281
R indexes (I > 2sI)
R1 = 0.0453 wR2 = 0.0975
R1 = 0.0318 wR2 = 0.0710
R indexes (all data)
R1 = 0.1089 wR2 = 0.1216
R1 = 0.0441 wR2 = 0.0750
0.928 1.047 Goodness of fit (Sall) Largest difference map hole/peak (e 106 pm3) 0.423/0.397 0.655/0.513 hP i1=2 hP i1=2 P P P R1 ¼ kFO jjFC k= jFO j, wR2 ¼ wðjFO j2 jFC j2 Þ2 = wðjFO j2 Þ2 , S2 ¼ wðjFO j2 jFC j2 Þ2 =ðn pÞ , with w ¼ 1=½s 2 ðFO Þ2 þ ð0:0581PÞ2 for h i P(C5F4N)3, and w ¼ 1=½s 2 ðFo Þ2 þ ð0:0359PÞ2 þ 0:9123P for As(C5F4N)3, where (P ¼ ðFo2 þ 2Fc2 Þ=3). Fc ¼ kFC 1 þ 0:001jFC j2 l3 =sinð2uÞ1=4 .
2.2. Molecular structures of tris(4tetrafluoropyridyl)phosphane, P(C5F4N)3 and tris(4tetrafluoropyridyl)arsenic, As(C5F4N)3 Both compounds crystallize isostructurally in the monoclinic space group P21/c (no.14) with four molecules per unit cell (Tables 1 and 2, Figs. 1 and 2).
The environment at the pnicogen atom is best described as a distorted trigonal pyramid with phosphorus or arsenic atoms forming the top (pseudo-tetrahedron). Bond length (mean values) of 184.3(3) pm (P) and 197.1(2) pm (As) do not deviate significantly from those reported for the isolobal pentafluorophenyl compounds (183.0(4) pm for P(C6F5)3 [9], 196.5(2) pm for As(C6F5)3 [10]). The molecular structure deviates
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Table 2 Selected bond lengths (pm) and angles (8) with estimated standard deviations in parentheses for P(C5F4N)3 and As(C5F4N)3 E = P, As
P(C5F4N)3
As(C5F4N)3
E1-C11 E1-C21 E1-C31 C11-E1-C21 C11-E1-C31 C21-E1-C31
184.8(3) 183.1(3) 185.0(3) 105.9(1) 94.8(1) 104.9(1)
197.4(1) 195.8(2) 198.0(2) 103.5(1) 91.2(1) 101.9(1)
extensively from ideal C3 symmetry. Also the C–P–C angles of 94.8(1), 104.9(1), and 105.9(1)8 as well as the C–As–C angles of 91.2(1), 101.9(1), and 103.5(1)8 agree approximately with those found for the analogous C6F5 derivatives [9–11]. The aromatic rings are tilted significantly to each other. All tetrafluoropyridyl groups are planar and deviations of angles within the aromatic rings may be attributed to the large selectron withdrawing influence of the C5F4N group [12]. In both molecules, aromatic rings (‘‘ring 3’’; N34, Fig. 2) of two neighbouring molecules are aligned in a parallel alternate fashion, with an interplanar separation of 365.5(2) pm (P) and 353.1(2) pm (As) exhibiting a characteristic p–p offset stacking [13]. Additionally, each N34 and each N24 atom is directed perpendicular onto ‘‘ring 1’’ (N14) making a doublesided edge-face stacking. While the interaction of N34 with ‘‘ring 1’’ (319.7(3) pm (P); 314.6(2) pm (As)) is essential for the formation of dimeric units, the perpendicular position of N24 over ‘‘ring 1’’ (310.5(3) pm (P); 308.3(2) pm (As)) is the structure-giving motif for extending the dimeric units into infinite chains of E(C5F4N)3 dimers (Fig. 2). This packing motif is better expressed in the structure of the arsenic compound than in the phosphorus derivative.
Fig. 1. View of As(C5F4N)3 showing the labeling scheme and the displacement ellipsoids at the 50% probability level.
3. Experimental Schlenk techniques were used throughout all manipulations. NMR spectra were recorded on a Bruker AC 200 (1H, 19F, 13C, 31 P) spectrometer. External standards were used in all cases (1H, 13C: Me4Si; 19F: CCl3F; 31P: H3PO4 (85%)). Acetone-d6 was used as an external lock (5 mm tube) in reaction control measurements while an original sample of the reaction mixture was measured in a 4 mm insert. EI mass spectra were recorded with the Finnigan MAT 95 spectrometer (20 eV) and Finnigan MAT 900 (70 eV). Intensities are referenced to the most intense peak of a group. Isotope patterns for comparison were calculated with the program Isopro [14]. Visible decomposition points were determined using HWS Mainz 2000 apparatus. C,
Fig. 2. View on a section of the infinite chain caused by p-stacking (As(C5F4N)3). Similar motifs are found for P(C5F4N)3.
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H, and N analyses were carried out with HEKAtech Euro EA 3000 apparatus. Details of crystal data and structure refinement parameters for P(C5F4N)3 and As(C5F4N)3 are summarised in Table 1. 3.1. Crystal structure analyses Both compounds, P(C5F4N)3 and As(C5F4N)3, easily form colourless single crystals which were sealed in glass capillaries and the suitability was checked with the help of an IPdiffractometer (STOE IPDS II) (see Table 1). The same device was used to collect the reflection data of the respective best specimen. The structures were solved by direct methods [17] and refined by full-matrix least-squares methods on F2 [18]. Distances between planes or atoms and planes were determined using the program PARST97 [19]. 3.2. Synthesis of tris(4-tetrafluoropyridyl)phosphane, P(C5F4N)3 [8] 1.45 g (5.8 mmol) tris(trimethylsilyl)phosphane, P(SiMe3)3, and 2.89 g (17.1 mmol) pentafluoropyridine were dissolved in 30 mL dimethoxyethane. The reaction mixture was refluxed for 22 h. After termination of the reaction, all volatile components were condensed off in vacuo. Colourless crystals (2.10 g; 75%) were grown from the pale yellow raw material by crystallization from chloroform. mp 168 8C; 250 8C (onset of decomposition). 19F-NMR (188.3 MHz, CDCl3): d = 88.5 (m, 2F, F-2,6); 130.7 (m, 2F, F-3,5); 13C-NMR (50.3 MHz, (CD3)2CO): d = 144.2 (dm, 1 JF,C 250 Hz, C-2,6); 143.4 (dm, 1JF,C 259 Hz, C-3,5); 123.8 (m, C-4); 31P-NMR (81.0 MHz, CDCl3): d = 71.8 (sept, 3 JP,F 28 Hz). EI-MS (20 eV): m/z (rel. int.): 481 [P(C5F4N)3]+ (100), 331 [P(C5F4N)2]+ (7), 300 [(C5F4N)2]+ (2).
3.4. Synthesis of tris(4-tetrafluoropyridyl)antimony, Sb(C5F4N)3 In a similar manner as described for arsenic, the reaction mixture was stirred for 48 h at 90 8C. The colourless reaction mixture was separated from the metal with a pipette. Evaporation of all volatile components gave a colourless solid, only sparingly soluble in common organic solvents. In contrast to Sb(C6F5)3 [20], Sb(C5F4N)3 exhibited to be extremely sensitive to moisture and air. 19 F-NMR (188.3 MHz, CD3CN): d = 92.5 (m, 2F, F-2,6); 124.6 (m, 2F, F-3,5). EI-MS (70 eV): m/z (rel. int.): 571 [121Sb(C5F4N)3]+ (48), 421 [121Sb(C5F4N)2]+ (16), 243 [C10F5N2]+ (81), 159 [121SbF2]+ (45), 151 [C5HF4N]+ (100). 3.5. Synthesis of tris(4-tetrafluoropyridyl)bismuth, Bi(C5F4N)3 In a similar manner as described for arsenic, the reaction mixture was stirred for 16 h at room temperature. The colourless reaction mixture was separated from the metal with a pipette. Evaporation of all volatile components gave a colourless solid, only sparingly soluble in common organic solvents. In contrast to Bi(C6F5)3 [21], Bi(C5F4N)3 is extremely sensitive to moisture and air. Addition of water to the mother liquor spontaneously gave C5HF4N and BiO(OH). The addition of the O-donor solvents DMF and DMSO to an EtCN solution caused turbidity and was accompanied by the formation of C5HF4N. 19 F-NMR (188.3 MHz, EtCN): d = 93.1 (m, 2F, F-2,6); 120.7 (m, 2F, F-3,5). EI-MS (20 eV): m/z (rel. int.): 659 [Bi(C5F4N)3]+ (100), 509 [Bi(C5F4N)2]+ (58), 359 [Bi(C5F4N)]+ (9), 151 [C5HF4N]+ (14). Acknowledgements
3.3. Synthesis of tris(4-tetrafluoropyridyl)arsenic, As(C5F4N)3 To a solution of AgC5F4N, prepared from 2.0 mmol AgF and 2.20 mmol Me3SiC5F4N, in 8 mL EtCN elemental arsenic dust was added in a large excess. The reaction mixture was stirred for 48 h at 80 8C. All volatile components were condensed off in vacuo. The remaining solid was extracted in a Soxhlet apparatus with dichloromethane. Colourless, crystalline As(C5F4N)3 was obtained in 45% yield (0.47 g; 0.90 mmol). Single crystals were grown upon storing a saturated dichloromethane/n-hexane solution overnight at 28 8C. mp 165–166 8C. 19F-NMR (188.3 MHz, EtCN): d = 91.3 (m, 2F, F-2,6); 129.7 (m, 2F, F-3,5); 13C-NMR (50.3 MHz, CD3CN): d = 144.4 (dm, 1JF,C 255 Hz, C-2,6); 144.0 (dm, 1 JF,C 255 Hz, C-3,5); 126.9 (t, 2JF,C 27 Hz). EI-MS (70 eV): m/z (rel. int.): 525 [As(C5F4N)3]+ (100), 375 [As(C5F4N)2]+ (44), 325 (?) (24), 262 [C10F6N2]+ (36), 243 [C10F5N2]+ (52), 225 [As(C5F4N)]+ (17). Anal. calcd for C15F12N3As: C, 34.3; N, 8.0%. Found: C, 34.8; N, 7.9%.
Generous support of this work by Prof. Dr. Dieter Naumann is gratefully acknowledged. We are indebted to our technicians for their great help. Thanks to Dr. Mathias Scha¨fer (Institute of Organic Chemistry) for recording the EI mass spectra (70 eV). References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]
W.E. Tyrra, J. Fluorine Chem. 112 (2001) 149–152. W. Tyrra, Heteroatom. Chem. 13 (2002) 561–566. W. Tyrra, D. Naumann, J. Fluorine Chem. 125 (2004) 823–830. W. Tyrra, M.S. Wickleder, Z. Anorg. Allg. Chem. 628 (2002) 1841– 1847. W. Tyrra, S. Aboulkacem, I. Pantenburg, J. Organomet. Chem. 691 (2006) 514–522. B. Hoge, C. Tho¨sen, T. Herrmann, P. Panne, I. Pantenburg, J. Fluorine Chem. 125 (2004) 831–851. W. Tyrra, D. Naumann, J. Fluorine Chem. 126 (2005) 1303–1306, and literature cited therein. Yu.A. Veits, N.B. Karlstedt, A.V. Chuchuryukin, I.P. Beletskaya, Russ. J. Org. Chem. 36 (2000) 750–756. A. Karipides, C. Miller Cosio, Acta Cryst. C45 (1989) 1743–1745. H. Mahalakshmi, V.K. Jain, E.R.T. Tiekink, Z. Kristallogr. NCS 218 (2003) 67–68.
W. Tyrra et al. / Journal of Fluorine Chemistry 127 (2006) 213–217 [11] A.L. Rheingold, D.L. Staley, M.E. Fountain, J. Organomet. Chem. 365 (1989) 123–125. [12] A. Domenicano, A. Vaciago, C.A. Coulson, Acta Cryst. B31 (1975) 221– 234; A. Domenicano, A. Vaciago, C.A. Coulson, Acta Cryst. B31 (1975) 1630– 1641. [13] M.L. Waters, Curr. Opin. Chem. Biol. 6 (2002) 736–741; C.A. Hunter, K.R. Lawson, J. Perkins, C.J. Urch, J. Chem. Soc, Perkin Trans. 2 (2001) 651–669; C.A. Hunter, J.K.M. Sanders, J. Am. Chem. Soc. 112 (1990) 5525–5534. [14] M. Senko, Isopro 3.0, Shareware, Sunnyvale, CA. [15] X-RED 1.22, Stoe Data Reduction Program (C) 2001 Stoe & Cie GmbH Darmstadt. [16] X-Shape 1.06, Crystal Optimisation for Numerical Absorption Correction (C) 1999 STOE & Cie GmbH Darmstadt.
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[17] A. Altomare, G. Cascarano, C. Giacovazzo, J. Appl. Crystallogr. 26 (1993) 343–350. [18] G.M. Sheldrick, SHELXL-97-Program for Structure Refinement, Go¨ttingen, 1998. [19] M. Nardelli, J. Appl. Crystallogr. 28 (1995) 659. [20] H.J. Frohn, H. Maurer, J. Fluorine Chem. 34 (1986) 129–145. [21] D. Naumann, W. Tyrra, J. Organomet. Chem. 334 (1987) 323– 328. [22] Crystallographic data for the structures have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication nos. CCDC-275840 for P(C5F4N)3 and CCDC-275841 for As(C5F4N)3. Copies of the data can be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223 336033 or e-mail: [email protected]).
Silver compounds in synthetic chemistry Part 4. 4-Tetrafluoropyridyl silver(I), AgC5F4N in redox transmetallations— possibilities and limitations in reactions with group 15 elements§ Wieland Tyrra *, Said Aboulkacem, Berthold Hoge, Waldemar Wiebe, Ingo Pantenburg Institut fu¨r Anorganische Chemie, Universita¨t zu Ko¨ln, Greinstr. 6, D-50939 Ko¨ln, Germany Received 7 September 2005; received in revised form 10 October 2005; accepted 15 October 2005 Available online 18 January 2006
Abstract While reactions of AgC5F4N with elemental arsenic, antimony, and bismuth proceed selectively yielding E(C5F4N)3 (E = As, Sb, Bi), those with white and red phosphorus remained obscure giving product mixtures of so far unknown stoichiometry. The phosphorus compound was therefore prepared by an alternative route. P(C5F4N)3 and As(C5F4N)3 crystallize isostructurally in the monoclinic space group P21/c (no. 14) with four molecules per unit cell. p–p Offset stacking together with edge-face stacking lead to dimeric units which are connected by a second edge-face stacking of nitrogen onto the opposite side of the same tetrafluoropyridyl ring extending the structure into infinite chains. # 2005 Elsevier B.V. All rights reserved. Keywords: 4-Tetrafluoropyridyl; Group 15; Synthesis; Crystal structure; p-Stacking
1. Introduction
2. Results and discussion
Oxidative properties of perfluoroorgano silver compounds have been outlined in some foregoing papers [1–4]. Reactions described therein had in common that perfluoroorgano element compounds of group 15 elements could be prepared more or less selectively for the heavier elements in moderate to good yields (As, Sb, Bi). In a recent publication, we showed that AgC5F4N [5] has comparable oxidative properties as AgC6F5 [1–4]. Additionally it has been shown by theoretical calculations [6] that the electron-withdrawing effect of the C5F4N ligand is even higher than that of the isolobal C6F5 group; the 4position is protected against unpredictable nucleophilic attack [7]. Herein, we offer a new selective approach for the syntheses of E(C5F4N)3 (E = As, Sb, Bi) starting from AgC5F4N and the corresponding elements. The low toxicity of silver, the ease of recycling together with the selectivity in redox transmetallations make silver compounds attractive for studies in the field of element organic synthesis [3].
2.1. Redox transmetallations of AgC5F4N and the pnicogens, phosphorus, arsenic, antimony, and bismuth
§
For Part 3 see [5]. * Corresponding author. Tel.: +49 221 470 3276; fax: +49 221 470 3276. E-mail address: [email protected] (W. Tyrra).
0022-1139/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jfluchem.2005.10.009
Redox transmetallations of AgC5F4N and arsenic, antimony and bismuth proceed in a similar manner as described for the group 12–14 elements [5] or for AgC6F5 and group 12–16 elements [4] (Eq. (1)).
(1)
Unfortunately, reactions with white and red phosphorus gave product mixtures which were not further identified. Therefore, P(C5F4N)3 was prepared alternatively by a literature procedure [8]. While As(C5F4N)3 was obtained as a colourless, crystalline material by common procedures, the extreme air and moisture sensitivity of Sb(C5F4N)3 and Bi(C5F4N)3 prevented from a full characterization. However, 19F NMR and mass spectra prove unambiguously the existence of both compounds.
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W. Tyrra et al. / Journal of Fluorine Chemistry 127 (2006) 213–217
Table 1 Crystal data and structure refinement parameters for P(C5F4N)3 and As(C5F4N)3
Empirical formula Formula mass (g mol1) Data collection Diffractometer Radiation Temperature (K)
P(C5F4N)3
As(C5F4N)3
C15N3F12P 481.15
C15N3F12As 525.10 STOE IPDS II Mo Ka, l = 71.073 pm
170(2)
170(2)
Index range
14 h 14 15 k 15 19 l 19
14 h 14 16 k 16 18 l 18
Rotation angle range
08 v 1808; c = 08 08 v 288; c = 908
08 v 1808; c = 08 08 v 1808; c = 908
Increment No. of images Exposure time (min) Detector distance (mm) 2u range (8) Total data collected Unique data Observed data Rmerg Absorption correction Transmission min/max
Dv = 28 104 10 100 2.2–59.5 17397 4407 2234 0.0625
Dv = 28 180 5 100 2.2–59.5 32019 4641 3669 0.0426 Numerical, after crystal shape optimization [15,16] 0.8353/0.9638 0.4835/0.7332
Crystallographic data [22] Crystal size (mm) Colour, habit Crystal system Space group a (pm) b (pm) c (pm) b (8) Volume (106 pm3) Z rcalc (mg m3) m (mm1) F(0 0 0)
0.3 0.3 0.1 Colourless, plate Monoclinic P21/c (no. 14) 1041.0(2) 1133.1(2) 1390.6(2) 98.80(1) 1621.0(4) 4 1.972 0.311 936
Structure analysis and refinement Structure determination No. of variables
281
0.2 0.2 0.15 Colourless, polyhedron Monoclinic P21/c (no. 14) 1045.3(1) 1176.6(1) 1360.3(1) 98.74(1) 1653.7(2) 4 2.109 2.194 1008 SIR-92 [17] and SHELXL-97 [18] 281
R indexes (I > 2sI)
R1 = 0.0453 wR2 = 0.0975
R1 = 0.0318 wR2 = 0.0710
R indexes (all data)
R1 = 0.1089 wR2 = 0.1216
R1 = 0.0441 wR2 = 0.0750
0.928 1.047 Goodness of fit (Sall) Largest difference map hole/peak (e 106 pm3) 0.423/0.397 0.655/0.513 hP i1=2 hP i1=2 P P P R1 ¼ kFO jjFC k= jFO j, wR2 ¼ wðjFO j2 jFC j2 Þ2 = wðjFO j2 Þ2 , S2 ¼ wðjFO j2 jFC j2 Þ2 =ðn pÞ , with w ¼ 1=½s 2 ðFO Þ2 þ ð0:0581PÞ2 for h i P(C5F4N)3, and w ¼ 1=½s 2 ðFo Þ2 þ ð0:0359PÞ2 þ 0:9123P for As(C5F4N)3, where (P ¼ ðFo2 þ 2Fc2 Þ=3). Fc ¼ kFC 1 þ 0:001jFC j2 l3 =sinð2uÞ1=4 .
2.2. Molecular structures of tris(4tetrafluoropyridyl)phosphane, P(C5F4N)3 and tris(4tetrafluoropyridyl)arsenic, As(C5F4N)3 Both compounds crystallize isostructurally in the monoclinic space group P21/c (no.14) with four molecules per unit cell (Tables 1 and 2, Figs. 1 and 2).
The environment at the pnicogen atom is best described as a distorted trigonal pyramid with phosphorus or arsenic atoms forming the top (pseudo-tetrahedron). Bond length (mean values) of 184.3(3) pm (P) and 197.1(2) pm (As) do not deviate significantly from those reported for the isolobal pentafluorophenyl compounds (183.0(4) pm for P(C6F5)3 [9], 196.5(2) pm for As(C6F5)3 [10]). The molecular structure deviates
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Table 2 Selected bond lengths (pm) and angles (8) with estimated standard deviations in parentheses for P(C5F4N)3 and As(C5F4N)3 E = P, As
P(C5F4N)3
As(C5F4N)3
E1-C11 E1-C21 E1-C31 C11-E1-C21 C11-E1-C31 C21-E1-C31
184.8(3) 183.1(3) 185.0(3) 105.9(1) 94.8(1) 104.9(1)
197.4(1) 195.8(2) 198.0(2) 103.5(1) 91.2(1) 101.9(1)
extensively from ideal C3 symmetry. Also the C–P–C angles of 94.8(1), 104.9(1), and 105.9(1)8 as well as the C–As–C angles of 91.2(1), 101.9(1), and 103.5(1)8 agree approximately with those found for the analogous C6F5 derivatives [9–11]. The aromatic rings are tilted significantly to each other. All tetrafluoropyridyl groups are planar and deviations of angles within the aromatic rings may be attributed to the large selectron withdrawing influence of the C5F4N group [12]. In both molecules, aromatic rings (‘‘ring 3’’; N34, Fig. 2) of two neighbouring molecules are aligned in a parallel alternate fashion, with an interplanar separation of 365.5(2) pm (P) and 353.1(2) pm (As) exhibiting a characteristic p–p offset stacking [13]. Additionally, each N34 and each N24 atom is directed perpendicular onto ‘‘ring 1’’ (N14) making a doublesided edge-face stacking. While the interaction of N34 with ‘‘ring 1’’ (319.7(3) pm (P); 314.6(2) pm (As)) is essential for the formation of dimeric units, the perpendicular position of N24 over ‘‘ring 1’’ (310.5(3) pm (P); 308.3(2) pm (As)) is the structure-giving motif for extending the dimeric units into infinite chains of E(C5F4N)3 dimers (Fig. 2). This packing motif is better expressed in the structure of the arsenic compound than in the phosphorus derivative.
Fig. 1. View of As(C5F4N)3 showing the labeling scheme and the displacement ellipsoids at the 50% probability level.
3. Experimental Schlenk techniques were used throughout all manipulations. NMR spectra were recorded on a Bruker AC 200 (1H, 19F, 13C, 31 P) spectrometer. External standards were used in all cases (1H, 13C: Me4Si; 19F: CCl3F; 31P: H3PO4 (85%)). Acetone-d6 was used as an external lock (5 mm tube) in reaction control measurements while an original sample of the reaction mixture was measured in a 4 mm insert. EI mass spectra were recorded with the Finnigan MAT 95 spectrometer (20 eV) and Finnigan MAT 900 (70 eV). Intensities are referenced to the most intense peak of a group. Isotope patterns for comparison were calculated with the program Isopro [14]. Visible decomposition points were determined using HWS Mainz 2000 apparatus. C,
Fig. 2. View on a section of the infinite chain caused by p-stacking (As(C5F4N)3). Similar motifs are found for P(C5F4N)3.
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H, and N analyses were carried out with HEKAtech Euro EA 3000 apparatus. Details of crystal data and structure refinement parameters for P(C5F4N)3 and As(C5F4N)3 are summarised in Table 1. 3.1. Crystal structure analyses Both compounds, P(C5F4N)3 and As(C5F4N)3, easily form colourless single crystals which were sealed in glass capillaries and the suitability was checked with the help of an IPdiffractometer (STOE IPDS II) (see Table 1). The same device was used to collect the reflection data of the respective best specimen. The structures were solved by direct methods [17] and refined by full-matrix least-squares methods on F2 [18]. Distances between planes or atoms and planes were determined using the program PARST97 [19]. 3.2. Synthesis of tris(4-tetrafluoropyridyl)phosphane, P(C5F4N)3 [8] 1.45 g (5.8 mmol) tris(trimethylsilyl)phosphane, P(SiMe3)3, and 2.89 g (17.1 mmol) pentafluoropyridine were dissolved in 30 mL dimethoxyethane. The reaction mixture was refluxed for 22 h. After termination of the reaction, all volatile components were condensed off in vacuo. Colourless crystals (2.10 g; 75%) were grown from the pale yellow raw material by crystallization from chloroform. mp 168 8C; 250 8C (onset of decomposition). 19F-NMR (188.3 MHz, CDCl3): d = 88.5 (m, 2F, F-2,6); 130.7 (m, 2F, F-3,5); 13C-NMR (50.3 MHz, (CD3)2CO): d = 144.2 (dm, 1 JF,C 250 Hz, C-2,6); 143.4 (dm, 1JF,C 259 Hz, C-3,5); 123.8 (m, C-4); 31P-NMR (81.0 MHz, CDCl3): d = 71.8 (sept, 3 JP,F 28 Hz). EI-MS (20 eV): m/z (rel. int.): 481 [P(C5F4N)3]+ (100), 331 [P(C5F4N)2]+ (7), 300 [(C5F4N)2]+ (2).
3.4. Synthesis of tris(4-tetrafluoropyridyl)antimony, Sb(C5F4N)3 In a similar manner as described for arsenic, the reaction mixture was stirred for 48 h at 90 8C. The colourless reaction mixture was separated from the metal with a pipette. Evaporation of all volatile components gave a colourless solid, only sparingly soluble in common organic solvents. In contrast to Sb(C6F5)3 [20], Sb(C5F4N)3 exhibited to be extremely sensitive to moisture and air. 19 F-NMR (188.3 MHz, CD3CN): d = 92.5 (m, 2F, F-2,6); 124.6 (m, 2F, F-3,5). EI-MS (70 eV): m/z (rel. int.): 571 [121Sb(C5F4N)3]+ (48), 421 [121Sb(C5F4N)2]+ (16), 243 [C10F5N2]+ (81), 159 [121SbF2]+ (45), 151 [C5HF4N]+ (100). 3.5. Synthesis of tris(4-tetrafluoropyridyl)bismuth, Bi(C5F4N)3 In a similar manner as described for arsenic, the reaction mixture was stirred for 16 h at room temperature. The colourless reaction mixture was separated from the metal with a pipette. Evaporation of all volatile components gave a colourless solid, only sparingly soluble in common organic solvents. In contrast to Bi(C6F5)3 [21], Bi(C5F4N)3 is extremely sensitive to moisture and air. Addition of water to the mother liquor spontaneously gave C5HF4N and BiO(OH). The addition of the O-donor solvents DMF and DMSO to an EtCN solution caused turbidity and was accompanied by the formation of C5HF4N. 19 F-NMR (188.3 MHz, EtCN): d = 93.1 (m, 2F, F-2,6); 120.7 (m, 2F, F-3,5). EI-MS (20 eV): m/z (rel. int.): 659 [Bi(C5F4N)3]+ (100), 509 [Bi(C5F4N)2]+ (58), 359 [Bi(C5F4N)]+ (9), 151 [C5HF4N]+ (14). Acknowledgements
3.3. Synthesis of tris(4-tetrafluoropyridyl)arsenic, As(C5F4N)3 To a solution of AgC5F4N, prepared from 2.0 mmol AgF and 2.20 mmol Me3SiC5F4N, in 8 mL EtCN elemental arsenic dust was added in a large excess. The reaction mixture was stirred for 48 h at 80 8C. All volatile components were condensed off in vacuo. The remaining solid was extracted in a Soxhlet apparatus with dichloromethane. Colourless, crystalline As(C5F4N)3 was obtained in 45% yield (0.47 g; 0.90 mmol). Single crystals were grown upon storing a saturated dichloromethane/n-hexane solution overnight at 28 8C. mp 165–166 8C. 19F-NMR (188.3 MHz, EtCN): d = 91.3 (m, 2F, F-2,6); 129.7 (m, 2F, F-3,5); 13C-NMR (50.3 MHz, CD3CN): d = 144.4 (dm, 1JF,C 255 Hz, C-2,6); 144.0 (dm, 1 JF,C 255 Hz, C-3,5); 126.9 (t, 2JF,C 27 Hz). EI-MS (70 eV): m/z (rel. int.): 525 [As(C5F4N)3]+ (100), 375 [As(C5F4N)2]+ (44), 325 (?) (24), 262 [C10F6N2]+ (36), 243 [C10F5N2]+ (52), 225 [As(C5F4N)]+ (17). Anal. calcd for C15F12N3As: C, 34.3; N, 8.0%. Found: C, 34.8; N, 7.9%.
Generous support of this work by Prof. Dr. Dieter Naumann is gratefully acknowledged. We are indebted to our technicians for their great help. Thanks to Dr. Mathias Scha¨fer (Institute of Organic Chemistry) for recording the EI mass spectra (70 eV). References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]
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W. Tyrra et al. / Journal of Fluorine Chemistry 127 (2006) 213–217 [11] A.L. Rheingold, D.L. Staley, M.E. Fountain, J. Organomet. Chem. 365 (1989) 123–125. [12] A. Domenicano, A. Vaciago, C.A. Coulson, Acta Cryst. B31 (1975) 221– 234; A. Domenicano, A. Vaciago, C.A. Coulson, Acta Cryst. B31 (1975) 1630– 1641. [13] M.L. Waters, Curr. Opin. Chem. Biol. 6 (2002) 736–741; C.A. Hunter, K.R. Lawson, J. Perkins, C.J. Urch, J. Chem. Soc, Perkin Trans. 2 (2001) 651–669; C.A. Hunter, J.K.M. Sanders, J. Am. Chem. Soc. 112 (1990) 5525–5534. [14] M. Senko, Isopro 3.0, Shareware, Sunnyvale, CA. [15] X-RED 1.22, Stoe Data Reduction Program (C) 2001 Stoe & Cie GmbH Darmstadt. [16] X-Shape 1.06, Crystal Optimisation for Numerical Absorption Correction (C) 1999 STOE & Cie GmbH Darmstadt.
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[17] A. Altomare, G. Cascarano, C. Giacovazzo, J. Appl. Crystallogr. 26 (1993) 343–350. [18] G.M. Sheldrick, SHELXL-97-Program for Structure Refinement, Go¨ttingen, 1998. [19] M. Nardelli, J. Appl. Crystallogr. 28 (1995) 659. [20] H.J. Frohn, H. Maurer, J. Fluorine Chem. 34 (1986) 129–145. [21] D. Naumann, W. Tyrra, J. Organomet. Chem. 334 (1987) 323– 328. [22] Crystallographic data for the structures have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication nos. CCDC-275840 for P(C5F4N)3 and CCDC-275841 for As(C5F4N)3. Copies of the data can be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223 336033 or e-mail: [email protected]).