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Novel iodoammonium cations: Synthesis and characterization of o-C6H4(NH2)2I+X− (X− = I−, AsF6−, AlI4−)
Polyhedron Vol. 8, No. 24, pp. 2911-2914, Printed in Great Britain
1989 0
0277-5387/89 $3.00+.00 1989 Pergamon Press plc
NOVEL IODOAMMONIUM CATIONS: SYNTHESIS AND CHARACTERIZATION OF o-C,J&(NH2)21+X- (X- = I-, AsF,, AU;) and TH. M. KLAPt)TKE*
I. TORNIEPORTH-OE’ITING
Institut fiir Anorganische und Analytische Chemie, Technische UniversitHt Berlin, StraSe des 17. Juni 135, D-1000 Berlin 12, F.R.G. (Received 20 July 1989 ; accepted 3 August 1989) Abstract-The new iodoammonium salts o-CsH4(NH2)21+I- (1) and o-C6H4(NH2)21+ AsF, (2) were prepared by reaction of o-phenylene diamine with I2 or I:AsF,, respectively. Compound 1 reacts with AlI yielding quantitatively the corresponding tetraiodoaluminate o-C,jH4(NH2)21+AlI; (3). The species were characterized by chemical analysis, vibrational (IR and Raman) and temperature-dependent ‘H NMR spectropscopy. Direct evidence for a N-I bond was found in the Raman spectra of 1, 2 and 3 (v(N1) = 599600 cm- ‘).
Compounds containing the free monoatomic cation, I+, in the condensed phase are still unknown. ’ However, the I+ cation can be stabilized by coordination and both 1: 1 and 1: 2 adducts of pyridine 2-4 and nitriles’ are known and may be prepared, via the disproportionation of iodine with nitriles or pyridine, respectively [eq. (l)] :6 nR-CN+I:AsF,
--+(R-CN),I+AsF; n = 1,2.
+Iz
unknown as far as we are aware. o-Phenylene diamine was used as the primary amine due to its ability to form chelate complexes. On the basis of a simple Born-Haber cycle (see below) we estimated that a reaction according to eq. (2) should be thermodynamically favourable (AH = - 59 kcal mol- ‘) ~-C~H~(NH~)~(S)+I:ASF;(S)Iz(s) + o-C6H4(NH&I+AsFi
(1) On the other hand, the reaction of ammonia with I:AsF, leads to the formation of N13, NH: AsF, and 12.6 As far as we are aware no iodoammonium salt has been prepared prior to this work. The reaction behaviour of I+ toward chalcogens and chalcogen-containing compounds is well known. However, the reactivity of “I+” towards compounds of group 15 is not very well established. For instance, I:AsF, reacts with elemental selenium yielding SeI$ AsF; .7 It also reacts with (CH3)2S giving (CH3)$I+AsF, .’ Quite recently the oxidation of iodine by MoF6 and UF6 in acetonitrile affording I(CH,CN):MF; (M = MO, v) was reported. ‘9’ We were particularly interested in the reaction behaviour of I: (and other “I+” sources) towards organic amines, especially with respect to the synthesis of novel iodoammonium salts. These are *Author to wham correspondence should be address&
(s).
(2)
EXPERIMENTAL Iodine (Merck) and AlI (Aldrich) were used as commercially avaiable. o-Phenylene diamine (Merck) was recrystallized twice from acetonitrile. The preparation of I: AsF; was carried out as described in the literature.7 The solvent (SO,(l), Messerqriesheim) was purified by distillation and dried over CaH,. All manipulations were carried out in an inert gas atmosphere (dry box). Preparation ofo-C6H4(NH&I+I-
(1)
A solution of 0.2129 g (1.97 mmol) of o-phenylene diamine in 5 cm3 of SOz was added to a suspension of 0.500 g of I2 (1.97 mmol) in 5 cm3 SO* and stirred for 1 h at room temperature. The sulphur dioxide was pumped off in vacua. The remaining black product was recrystallized from SO*. Yield : 0.7126 g (100%). Found: C, 19.5; H, 2.1; N, 7.7. Calc. for C6H812N2 (361.953) C, 19.9 ; H, 2.2 ; N,
2911
2912 ’
I. TORNIEPORTH-OETTING
7.7%. ‘H NMR (SO,) G(ppm) 7.10 s (CH), 6.45s (NH), relative to TMS. IR : v(cm- ‘) (CsI) 3330m, 316Ow, 292Ow, 167Ow, 1628m, 1565m, 1528s 1498s, 132Ow, 1270m, 1155m, 1035m, 94Ow, 885m, 825m, 752s, 583m, 525w, 445m. Raman : v(cm- ‘) (647 mn, 60 mW, 20°C); (int) 872 (4), 817 (6) 739 (5), 599 (loo), 327 (3), 314 (2), 275 (26), 200 (l), 81 (17). Preparation
of o-C6H4(NH2)J+AsF;
(2)
A solution of 0.3147 g (2.91 mmol) of o-phenylene diamine in 5 cm3 of SO2 was reacted with 1.6576 g (2.91 mmol) of I:AsF; in 5 cm3 of SOa at room temperature. The reaction mixture was stirred for 1 h and the precipitated iodine was filtered off (D3). The remaining solution was evaporated and traces of dissolved iodine were removed by pumping in a dynamic vacuum. The remaining microcrystalline, deep red product was isolated nearly quantitatively. Yield: 1.2253 g (99%). Compound 2 was recrystallized twice from SOz. Found : C, 17.4 ; H, 2.1; N, 6.8. Calc. for C6HBAsF61N2 (423.952) C, 17.0; H, 1.9; N, 6.6%. MS (160°C 70 eV): m/z (int.) 456 (3) AsI:, 318 (3) (CsH4N2 H,):, 300 (1) As:, 254 (46) I;, 180 (9) C6H4NZ HAS+, 151(6)AsF$, 132(77)AsF:, 128 (ll)HI+, 127 (41) I+, 113 (100) AsF:, 105 (4) C6H4NZH+, 94(5)AsF + . ‘H NMR (SO,) G(ppm) 7.42 s, relative to TMS. Vapour pressure osmometry (THF) 467 g mol- ‘. IR : v(cm-‘) (CsI) 332Ow, 324Ow, 322Ow, 165Ow, 1610m, 1522s, 1490m, 138Ow, 1258w, 124Ow, 1155w, 842m, 757m, 698~s 585m, 395s. Raman : v(cm- ‘) (647 nm, 100 mW, 20°C) ; (int) : 736 (7), 600 (IOO), 273 (22), 236 (5), 167 (6), 96 (25). Preparation
of o-C6H4(NHJJ+A11;
(3)
To a suspension of 0.643 g (1.576 mmol) of AlI in 5 cm3 of SO* a solution of 0.570 g (1.576 mmol) of 1 in 5 cm3 of SO1 was added at room temperature. The mixture was stirred for 1 hat room temperature and the solvent evaporated. The remaining black product was recrystallized from SOz. Yield: 0.946 g (78%). Found: C, 9.4; H, 1.1; N, 3.3. Calc. for C6HsAl15N2 (769.626) C, 9.4; H, 1.0; N, 3.6%. ‘H NMR (SO,) G(ppm) 7.25s (CH), 6.27s (NH). IR: v(cm- ‘) (CsI) 33OOs, br, 1670sh, 1615s, 1528m, 149Ow, 1385vw, 126Ovw, 124Ovw, 1035m, 912m, 755m, br, 66Ow, 59Ow, 535w, 430~. Raman: v(cm- ‘) (647 nm, 75 mW, 20°C) 599.
and TH. M. KLAPOTKE
iodoammonium
salt 1 according to eq. (3) :
o-C6Hz,(NH& +I2 >o-C6H4(NH&I+I-. (1)
(3) The hexafluoroarsenate species, 2, was obtained by reaction of the amine with 1: AsF; [eq. (2)]. Complex 1 was converted into the tetraiodoaluminate salt, 3, by reaction with one equivalent of AlI according to eq. (4) : 1+A113 sq,
o-C6H4(NH2)J+AlI;
.
(4)
(3) Complexes 1, 2 and 3 were identified by chemical analysis (C, H, N), ‘H NMR, IR, Raman and mass spectroscopy. The quality of the elemental analyses varies and only freshly prepared samples give satisfying results ; dependent on technique, too low C/H/N values (especially for the AlI; salt) were often observed (probably due to carbide or nitride formation). Thermodynamic
aspects
On the basis of a simple Born-Haber cycle (Scheme 1) (using a similar approach to that described in ref. 10) we estimated that a reaction according to eq. (2) should be thermodynamically favourable (AH = - 59 kcal mol- ‘). The BornHaber cycle estimate for AH0 for the reaction indicates that nitrogen is a better base towards I+ than I’. Therefore the cationic N-I species should be thermodynamically more stable than neutral compounds. This is in good agreement with the experimental results described above. Vibrational spectroscopy
Direct evidence for N-I bonds was found in the Raman spectra of all compounds. The most intense peak at 599-600 cm-’ can be attributed to a N-I stretching mode (Fig. 1). Both, the shift to higher wavenumbers compared with the neutral tetracoordinatedNI,*NH,(v, = 378cr~‘)‘~due to the stronger N-I bond in the cationic species and the similarity to the isoelectronic carbon derivative (CH31, v(C1) = 523 cm-‘)” are in good agreement with the formulated N-I bond. ‘H NMR spectroscopy
RESULTS Preparative
AND DISCUSSION
aspects
Reaction of o-phenylene diamine with elemental iodine led to the preparation of the new cationic
In the room temperature ‘H NMR spectrum of 1 and 3 two resonances appear, one due to the CH, the other due to the NH protons. (N.B. ‘H NMR of o-CgH4(NH& in SO*: G(ppm) 6.68s, 3.97~.)~
Novel iodoammonium +
I
I
a IS+(g)
C6H4(NH2)2(g)
1
b I+(e) I
I*(S)
+
C6H,+(NH2)2I+AsF6-W A
C
+
1
C6H4(NH2)2+W
*
13+AsF6-(s)
2913
cations
AsF6-(9)
d
f +
2
h
I(g)
e
I(g)
-
C6H4tNH2)21+tg)
9
Scheme 1. Energy cycle for the formation of o-C,H,(NHJJ+AsF; (2) from o-phenylene diamine and 1:AsF; according to eq. (2). (a) AiYs,,,,,(CsHsNJ was taken to be equal to 20 kcal mol-’ (cf. AZ&,,(salicylic acid) = 22.8 kcal mol-‘).‘” (b) Z&H,NJ = 172 kcal mol- ‘. ‘I (c) U,(I:AsF;) = 128 kcal mol-‘.I2 (d) AH(I:,g + I+, g+21, g) = 72.4 kcal mol-‘.I* (e) AHI, g + I+, g) = 242.5 kcal mol-I.‘* (f) AH,O(I, g) = 25.6 kcal mol-‘.I* (g) Bond energy (N-I) = 48 kcal mol-‘.‘3 (h) U,_(C6HsN21+AsF;) = 110 kcal mol-‘. Estimated as demonstrated in ref. 12 using the linear relationship: U,(kcal mol-‘) = 556.3 VM(A3)-o.33+26.3;‘2 I/,(AsF;) = 105 A3,‘* assuming that V,(C,H,N,I+) is equal to V,(C,H,N,)+V,(I+), using V,(CJ&N,) = 148 A3 and V,(I+) = 34 A’.‘“*” This gives: a+b+c+d-e-2f-g-h = -59.3 kcal mol-‘.
0
200
wavenumber
400
/
600
cm-’
Fig. 1. Raman spectrum of o-CsH@JH2)21+II
temperature spectrum of 2 shows one resonance in the aromatic CH region (7.42 ppm), which can be explained by intermolecular NH proton exchange (Fig. 2). As 2 is the only example with an iodine-free anion it may have the most ionic character, which probably favours the intermolecular exchange reactions. Moreover, the ‘H
The room
=
800
1000
(1) (excitation line 647 nm, 100 mW, ZO’C).
NMR spectrum of 2 (Fig. 2) shows a reversible temperature dependence. At low temperature resonances appear due to both the NH protons (“singlet”) and the aromatic protons (multiplet, AA’XX’ pattern). The equivalence of the NH protons in all three compounds can be easily explained by the equilibrium of the cations according to eq. (5) and rapid exchange reactions :
=
(5) H2
I. TORNIEPORTH-OETTING
2914
,7.42
PPI
!
+4O'C
Y
[[y
+2O'C TI'C / -4O'C
I
I
6/ppn
7.0
5.0
3.0
Fig. 2. Temperature-dependent ‘H NMR spectrum of oCsH,(NH&IfAsF; (2) in SO2 solution, relative to TMS. thank the members of our department staff for support. We also acknowledge the financial support of the Technische Universitat Berlin, the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. Acknowledgements-We
REFERENCES 1. A. F. Holleman, E. Wiberg and N. Wiberg, Lehrbuch der Anorganischen Chemie, 91-100 edns, p. 403. Walter de Gruyter, Berlin, New York (1985).
and TH. M. KLAMTKE 2. R. A. Zingaro, C. A. VanderWerf and J. Kleinberg, J. Am. Chem. Sac. 1949,71,575. 3. R. A. Zingaro and W. E. Tolberg, J. Am. Chem. Sot. 1959,81, 1353. 4. R. A. Zingaro and W. B. Witmer, J. Phys. Chem. 1960,64, 1705. 5. G. M. Anderson and J. M. Winfield, J. Chem. Sot., Dalton Trans. 1986, 337. 6. Th. Klapiitke, J. Passmore and I. TornieporthOetting, unpublished results. 7. J. Passmore and P. Taylor, J. Chem. Sot., Dalton Trans. 1976,804. 8. R. Minkwitz and H. Prenzel, 2. Anorg. Allg. Chem. 1987,54&97. 9. G. M. Anderson, I. F. Fraser and J. M. Winfield, J. Fluorine Chem. 1983,23,403. 10. Handbook of Chemistry and Physics, 55th edn, p. 716. CRC Press, Cleveland (1974/75). 11. Beilstein, E IV 13, p. 38. 12. N. Burford, J. Passmore and J. C. P. Sanders, Molecular Structure and Bonding, Vol. 11. VCH Verlag Chemie, Weinheim (1989). 13. R. Steudel, Chemistry of Non-metals, p. 130. Walter de Gruyter, Berlin (1977). 14 J. Jander and U. Engelhardt, Nitrogen Compounds of Chlorine, Bromine and Iodine in Developments in Inorganic Nitrogen Chemistry (Edited by C. B. Colbum), Vol. 2, p. 184 and refs therein. Elsevier, Amsterdam (1973). 15. F. R. Dollish, W. G. Fateley and F. F. Bentley, Characteristic Raman Frequencies of Organic Compour&, p. 12. John Wiley, New York (1978).
1989 0
0277-5387/89 $3.00+.00 1989 Pergamon Press plc
NOVEL IODOAMMONIUM CATIONS: SYNTHESIS AND CHARACTERIZATION OF o-C,J&(NH2)21+X- (X- = I-, AsF,, AU;) and TH. M. KLAPt)TKE*
I. TORNIEPORTH-OE’ITING
Institut fiir Anorganische und Analytische Chemie, Technische UniversitHt Berlin, StraSe des 17. Juni 135, D-1000 Berlin 12, F.R.G. (Received 20 July 1989 ; accepted 3 August 1989) Abstract-The new iodoammonium salts o-CsH4(NH2)21+I- (1) and o-C6H4(NH2)21+ AsF, (2) were prepared by reaction of o-phenylene diamine with I2 or I:AsF,, respectively. Compound 1 reacts with AlI yielding quantitatively the corresponding tetraiodoaluminate o-C,jH4(NH2)21+AlI; (3). The species were characterized by chemical analysis, vibrational (IR and Raman) and temperature-dependent ‘H NMR spectropscopy. Direct evidence for a N-I bond was found in the Raman spectra of 1, 2 and 3 (v(N1) = 599600 cm- ‘).
Compounds containing the free monoatomic cation, I+, in the condensed phase are still unknown. ’ However, the I+ cation can be stabilized by coordination and both 1: 1 and 1: 2 adducts of pyridine 2-4 and nitriles’ are known and may be prepared, via the disproportionation of iodine with nitriles or pyridine, respectively [eq. (l)] :6 nR-CN+I:AsF,
--+(R-CN),I+AsF; n = 1,2.
+Iz
unknown as far as we are aware. o-Phenylene diamine was used as the primary amine due to its ability to form chelate complexes. On the basis of a simple Born-Haber cycle (see below) we estimated that a reaction according to eq. (2) should be thermodynamically favourable (AH = - 59 kcal mol- ‘) ~-C~H~(NH~)~(S)+I:ASF;(S)Iz(s) + o-C6H4(NH&I+AsFi
(1) On the other hand, the reaction of ammonia with I:AsF, leads to the formation of N13, NH: AsF, and 12.6 As far as we are aware no iodoammonium salt has been prepared prior to this work. The reaction behaviour of I+ toward chalcogens and chalcogen-containing compounds is well known. However, the reactivity of “I+” towards compounds of group 15 is not very well established. For instance, I:AsF, reacts with elemental selenium yielding SeI$ AsF; .7 It also reacts with (CH3)2S giving (CH3)$I+AsF, .’ Quite recently the oxidation of iodine by MoF6 and UF6 in acetonitrile affording I(CH,CN):MF; (M = MO, v) was reported. ‘9’ We were particularly interested in the reaction behaviour of I: (and other “I+” sources) towards organic amines, especially with respect to the synthesis of novel iodoammonium salts. These are *Author to wham correspondence should be address&
(s).
(2)
EXPERIMENTAL Iodine (Merck) and AlI (Aldrich) were used as commercially avaiable. o-Phenylene diamine (Merck) was recrystallized twice from acetonitrile. The preparation of I: AsF; was carried out as described in the literature.7 The solvent (SO,(l), Messerqriesheim) was purified by distillation and dried over CaH,. All manipulations were carried out in an inert gas atmosphere (dry box). Preparation ofo-C6H4(NH&I+I-
(1)
A solution of 0.2129 g (1.97 mmol) of o-phenylene diamine in 5 cm3 of SOz was added to a suspension of 0.500 g of I2 (1.97 mmol) in 5 cm3 SO* and stirred for 1 h at room temperature. The sulphur dioxide was pumped off in vacua. The remaining black product was recrystallized from SO*. Yield : 0.7126 g (100%). Found: C, 19.5; H, 2.1; N, 7.7. Calc. for C6H812N2 (361.953) C, 19.9 ; H, 2.2 ; N,
2911
2912 ’
I. TORNIEPORTH-OETTING
7.7%. ‘H NMR (SO,) G(ppm) 7.10 s (CH), 6.45s (NH), relative to TMS. IR : v(cm- ‘) (CsI) 3330m, 316Ow, 292Ow, 167Ow, 1628m, 1565m, 1528s 1498s, 132Ow, 1270m, 1155m, 1035m, 94Ow, 885m, 825m, 752s, 583m, 525w, 445m. Raman : v(cm- ‘) (647 mn, 60 mW, 20°C); (int) 872 (4), 817 (6) 739 (5), 599 (loo), 327 (3), 314 (2), 275 (26), 200 (l), 81 (17). Preparation
of o-C6H4(NH2)J+AsF;
(2)
A solution of 0.3147 g (2.91 mmol) of o-phenylene diamine in 5 cm3 of SO2 was reacted with 1.6576 g (2.91 mmol) of I:AsF; in 5 cm3 of SOa at room temperature. The reaction mixture was stirred for 1 h and the precipitated iodine was filtered off (D3). The remaining solution was evaporated and traces of dissolved iodine were removed by pumping in a dynamic vacuum. The remaining microcrystalline, deep red product was isolated nearly quantitatively. Yield: 1.2253 g (99%). Compound 2 was recrystallized twice from SOz. Found : C, 17.4 ; H, 2.1; N, 6.8. Calc. for C6HBAsF61N2 (423.952) C, 17.0; H, 1.9; N, 6.6%. MS (160°C 70 eV): m/z (int.) 456 (3) AsI:, 318 (3) (CsH4N2 H,):, 300 (1) As:, 254 (46) I;, 180 (9) C6H4NZ HAS+, 151(6)AsF$, 132(77)AsF:, 128 (ll)HI+, 127 (41) I+, 113 (100) AsF:, 105 (4) C6H4NZH+, 94(5)AsF + . ‘H NMR (SO,) G(ppm) 7.42 s, relative to TMS. Vapour pressure osmometry (THF) 467 g mol- ‘. IR : v(cm-‘) (CsI) 332Ow, 324Ow, 322Ow, 165Ow, 1610m, 1522s, 1490m, 138Ow, 1258w, 124Ow, 1155w, 842m, 757m, 698~s 585m, 395s. Raman : v(cm- ‘) (647 nm, 100 mW, 20°C) ; (int) : 736 (7), 600 (IOO), 273 (22), 236 (5), 167 (6), 96 (25). Preparation
of o-C6H4(NHJJ+A11;
(3)
To a suspension of 0.643 g (1.576 mmol) of AlI in 5 cm3 of SO* a solution of 0.570 g (1.576 mmol) of 1 in 5 cm3 of SO1 was added at room temperature. The mixture was stirred for 1 hat room temperature and the solvent evaporated. The remaining black product was recrystallized from SOz. Yield: 0.946 g (78%). Found: C, 9.4; H, 1.1; N, 3.3. Calc. for C6HsAl15N2 (769.626) C, 9.4; H, 1.0; N, 3.6%. ‘H NMR (SO,) G(ppm) 7.25s (CH), 6.27s (NH). IR: v(cm- ‘) (CsI) 33OOs, br, 1670sh, 1615s, 1528m, 149Ow, 1385vw, 126Ovw, 124Ovw, 1035m, 912m, 755m, br, 66Ow, 59Ow, 535w, 430~. Raman: v(cm- ‘) (647 nm, 75 mW, 20°C) 599.
and TH. M. KLAPOTKE
iodoammonium
salt 1 according to eq. (3) :
o-C6Hz,(NH& +I2 >o-C6H4(NH&I+I-. (1)
(3) The hexafluoroarsenate species, 2, was obtained by reaction of the amine with 1: AsF; [eq. (2)]. Complex 1 was converted into the tetraiodoaluminate salt, 3, by reaction with one equivalent of AlI according to eq. (4) : 1+A113 sq,
o-C6H4(NH2)J+AlI;
.
(4)
(3) Complexes 1, 2 and 3 were identified by chemical analysis (C, H, N), ‘H NMR, IR, Raman and mass spectroscopy. The quality of the elemental analyses varies and only freshly prepared samples give satisfying results ; dependent on technique, too low C/H/N values (especially for the AlI; salt) were often observed (probably due to carbide or nitride formation). Thermodynamic
aspects
On the basis of a simple Born-Haber cycle (Scheme 1) (using a similar approach to that described in ref. 10) we estimated that a reaction according to eq. (2) should be thermodynamically favourable (AH = - 59 kcal mol- ‘). The BornHaber cycle estimate for AH0 for the reaction indicates that nitrogen is a better base towards I+ than I’. Therefore the cationic N-I species should be thermodynamically more stable than neutral compounds. This is in good agreement with the experimental results described above. Vibrational spectroscopy
Direct evidence for N-I bonds was found in the Raman spectra of all compounds. The most intense peak at 599-600 cm-’ can be attributed to a N-I stretching mode (Fig. 1). Both, the shift to higher wavenumbers compared with the neutral tetracoordinatedNI,*NH,(v, = 378cr~‘)‘~due to the stronger N-I bond in the cationic species and the similarity to the isoelectronic carbon derivative (CH31, v(C1) = 523 cm-‘)” are in good agreement with the formulated N-I bond. ‘H NMR spectroscopy
RESULTS Preparative
AND DISCUSSION
aspects
Reaction of o-phenylene diamine with elemental iodine led to the preparation of the new cationic
In the room temperature ‘H NMR spectrum of 1 and 3 two resonances appear, one due to the CH, the other due to the NH protons. (N.B. ‘H NMR of o-CgH4(NH& in SO*: G(ppm) 6.68s, 3.97~.)~
Novel iodoammonium +
I
I
a IS+(g)
C6H4(NH2)2(g)
1
b I+(e) I
I*(S)
+
C6H,+(NH2)2I+AsF6-W A
C
+
1
C6H4(NH2)2+W
*
13+AsF6-(s)
2913
cations
AsF6-(9)
d
f +
2
h
I(g)
e
I(g)
-
C6H4tNH2)21+tg)
9
Scheme 1. Energy cycle for the formation of o-C,H,(NHJJ+AsF; (2) from o-phenylene diamine and 1:AsF; according to eq. (2). (a) AiYs,,,,,(CsHsNJ was taken to be equal to 20 kcal mol-’ (cf. AZ&,,(salicylic acid) = 22.8 kcal mol-‘).‘” (b) Z&H,NJ = 172 kcal mol- ‘. ‘I (c) U,(I:AsF;) = 128 kcal mol-‘.I2 (d) AH(I:,g + I+, g+21, g) = 72.4 kcal mol-‘.I* (e) AHI, g + I+, g) = 242.5 kcal mol-I.‘* (f) AH,O(I, g) = 25.6 kcal mol-‘.I* (g) Bond energy (N-I) = 48 kcal mol-‘.‘3 (h) U,_(C6HsN21+AsF;) = 110 kcal mol-‘. Estimated as demonstrated in ref. 12 using the linear relationship: U,(kcal mol-‘) = 556.3 VM(A3)-o.33+26.3;‘2 I/,(AsF;) = 105 A3,‘* assuming that V,(C,H,N,I+) is equal to V,(C,H,N,)+V,(I+), using V,(CJ&N,) = 148 A3 and V,(I+) = 34 A’.‘“*” This gives: a+b+c+d-e-2f-g-h = -59.3 kcal mol-‘.
0
200
wavenumber
400
/
600
cm-’
Fig. 1. Raman spectrum of o-CsH@JH2)21+II
temperature spectrum of 2 shows one resonance in the aromatic CH region (7.42 ppm), which can be explained by intermolecular NH proton exchange (Fig. 2). As 2 is the only example with an iodine-free anion it may have the most ionic character, which probably favours the intermolecular exchange reactions. Moreover, the ‘H
The room
=
800
1000
(1) (excitation line 647 nm, 100 mW, ZO’C).
NMR spectrum of 2 (Fig. 2) shows a reversible temperature dependence. At low temperature resonances appear due to both the NH protons (“singlet”) and the aromatic protons (multiplet, AA’XX’ pattern). The equivalence of the NH protons in all three compounds can be easily explained by the equilibrium of the cations according to eq. (5) and rapid exchange reactions :
=
(5) H2
I. TORNIEPORTH-OETTING
2914
,7.42
PPI
!
+4O'C
Y
[[y
+2O'C TI'C / -4O'C
I
I
6/ppn
7.0
5.0
3.0
Fig. 2. Temperature-dependent ‘H NMR spectrum of oCsH,(NH&IfAsF; (2) in SO2 solution, relative to TMS. thank the members of our department staff for support. We also acknowledge the financial support of the Technische Universitat Berlin, the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. Acknowledgements-We
REFERENCES 1. A. F. Holleman, E. Wiberg and N. Wiberg, Lehrbuch der Anorganischen Chemie, 91-100 edns, p. 403. Walter de Gruyter, Berlin, New York (1985).
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