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Octaethyltetraselenaporphyrin Dication.

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[9] M. Driess, H. Griitzmacher, Angew. Chem. 1996, 108, 900-929; Angew.
Chem. Inr. Ed. Engl. 1996,35,828-856.
[lo] a) Z. Shi, V. Goulle, R. G. Thummel, Tetrahedron Lett. 1996,372357 -2360;
b) G. V. Tormos, M. G. Bakker, .'F Wang, M. V. Lakshmikantham, M. P.
Cava, R. M. Metzger, J. Am. Chem. SOC. 1995,117,8528-8535.
[I11 T. A. Taton, P. Chen, Angew. Chem. 1996,108,1098- 1100; Angew. Chem.
Int. Ed. Engl. 1996,35, 1011- 1013.
[I21 a) M. Denk, R. Lemon, R. Hayashi, R. West, A. V. Belyakov, H. P. Verne,
A. Haaland, M. Wagner, N. Metzler, J. Am. Chem. SOC.1994, 116, 2691 2692; b) M. Denk, R. K. Hayashi, R. West, J. Chem. SOC.Chem. Commun.
1994.33-34; c) M. Denk, J. Green, N. Metzler, M. Wagner, J. Chern. SOC.
Dalton Trans. 1994, 2405-2410; d) N. Metzler, M. Denk, J. Chem. Soc.
Chem. Commun. 1996,2657-2658.
(131 W. A. Herrmann, M. Denk, J. Behm. W. Scherer, F.-R. Klingan, H. Bock, B.
Solouki, M. Wagner, Angew. Chem. 1992,104, 1489-1492; Angew. Chem.
In!. Ed Engl. 1992,31, 1485- 1488.
1141 M. K. Denk, S. Gupta. R. Ramachandran, Tetrahedron Lett. 1996,37,90259028.
[I51 a) R. A. Donia, J. A. Shotton, L. 0. Bentz, G. E. F'. Smith, J. Org. Chem.
1949,14,946-951; b) C. Li, S. L. Mella, A. C. Sartorelli, J. Med. Chem. 1981
24, 1089- 1092.
[16] N. Kuhn, T. Kratz, Synthesis 1993,561 -562.
[17] a) B. Cetinkaya, P. B. Hitchcock, M. F. Lappert, D. B. Shaw, K. Spyropoulos,
N. J. W. Warhurst. J. Orgonomet. Chem. 1993, 459, 311-317; b) M. F.
Lappert, J. Organomet. Chem. 1988,358,185-214.
[I81 Reviews on cnetetramines: N. Wiberg, Angew. Chem. 1968, 80,809-833;
Angew. Chem. Int. Ed. Engl. 1968, 7,766-779; J. Hocker, R. Merten, ibid.
1972.84,1022; Angew. Chem. Int. Ed. Engl. 1972,11,964.
[I91 Details will be published elsewhere. Different rate laws can be observed in
the presence of protic impurities (R. W. Alder, personal communication).
[20] Earlier studies have ruled out the dissociation of olefins 4 into free carbenes:
a) D. M. Lemal, R. A. Lovald, K. I. Kawano, J. Am. Chem. SOC.1964,86,
2518-2519. b) H. E. Winberg, J. E. Carnahan, D.D. Coffman, M. Brown,
ibid. 1%5, 87. 2055-2056.
1211 a) R. W. Alder, P. R. Allen, S. J. Williams, J. Chem. SOC. Chem. Commun.
1995,1267- 1268; b) X.-W. Li, J. Su, G. H. Robinson, J. Chem. Soc. Chem.
Commun. 1996,2683-2684.
[221 Crystal data €or 3d: M,= 182.31, monoclinic, space group PZ,/n, a =
6.2116(5),
b = 18.510(2), C = 10.1210(9) A, B=92.732(7)",
V=
1162.3(2) A'. pcalcd
= 1.042 g cm-), p(MoKn)= 0.62 cm-', T = 173 K, 3651
reflections collected (3.0 < 0 < 30.0') and no absorption correction. Structure refined on F' and hydrogen atoms were refined with isotropic thermal
parameters. Final R1 [ I > 20(f)I =OM47 for 2698 observed reflections and
wR2 (all data) =0.1166 for 3383 independent reflections. Maximum and
minimum peaks in final AFmap were 0.31 and - 0.26 e k 3 . 48:M , = 196.30,
monoclinic, space group Pl,a=7.731(3), b=8.100(2), c=9.912(2) A,Q =
96.74(2), p = 99.37(2), y = 113.21(2)", V = 551.5(2) A3, pcald
= 1.182 g cm-),
p(Moxa)= 0.75 cm-I, T = 173 K, 3395 reflections collected (3.0 < 0 < 30.0")
and n o absorption correction. Structure refined on F 2 and hydrogen atoms
in calculated positions. Final R, [I>2o(Z)] =0.0411 for 2342 observed
reflections and wR2 (all data) =0.1209 for 3178 independent reflections.
Maximum and minimum peaks in final AFmap were 0.48 and -0.18 e k 3 .
Both structures were solved and refined by using SHELXTLPC [23].
Crystallographic data (excluding structure factors) for 3d and 4a have been
deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-100576. Copies of the data can be obtained
free of charge on application to the Director, CCDC, 12 Union Road,
Cambridge CB2 lEZ, UK (Fax: Int. Code +(1223) 336-033; e-mail:
deposit@chemcrys.cam.ac.uk) .
[23] G. M. Sheldrick, SHELXTLiPC V5.0, Program for Structure SoIution and
Refinement. Siemens Analytical X-ray Systems Inc. Madison, Wisconsin,
USA, 1994.
1241 M. Denk, results presented at the 80th Canadian Society for Chemistry
Conference, Windsor, Ontario, June 1-4,1997.
Octaethyltetraselenaporphyrin Dication**
E m a n u e l Vogel,* Christoph Frode, Andreas Breihan,
Hans Schmickler, and Johann Lex
Dedicated to Professor Marianne Baudler
on the occasion of her 75th birthday
The oxygen analogue of porphyrin, the Dlh symmetrical
dication 1 (as its perchlorate) d1,2]constitutes a key compound
in the chemistry of nonnatural porphyrins. There exists a close
relationship between 1 and porphyrin, both in terms of their
synthesis and their aromaticity, as evident from spectra and
molecular structure. However, the two macrocycles differ
markedly in their chemical properties. Unlike porphyrin and
the neutral monooxa- and dioxaporphyrin~,[~I
1 is no longer
able to form complexes with metal ions because of its positive
charge. Central to the chemistry of 1 are nucleophilic
additions (and subsequent transformations) and the tetraoxaporphyrin redox system, which is derived from the dication
and is interesting from many viewpoints.[4]
9
F
I
R
fi
A
1-6
R=H
R=C,H,
1: X=O, 2: X=S, 3:X=Se (in solution only)
4: X=O, 5: X=S. 6: X=Se
The recently synthesized tetrathiaporphyrin dication 2 (as
its p e r c h l ~ r a t e ) [ ~
and
, ~ ]the tetraselenaporphyrin dication 3,c51
which has until now only been obtained in solution, both
resemble 1 in terms of their reactivity and spectral characteristics, even though the ring system deviates significantly from
planarity because of the steric interactions of the heteroatoms.
Since the study of 1-3 is adversely affected by problems
associated with solubility and/or crystallization, it is sensible
to follow the lead of porphyrin chemistry and turn to the
octaethyl compounds 4-6. After the syntheses of 4c71and 5,ISI
that of 6, presented here, has also been achieved, and with it
the set of chalcogenaporphyrins-with the exception of the
tellura comp~und[~l-isnow complete.
The 2-(hydroxymethyl)-3,4-diethylselenophene (7)"OI was
chosen as the starting material in the synthesis of the
octaethyltetraselenaporphyrindication 6 (as its perchlorate).
This would allow use of the route already proven in the
synthesis of 1, 4, and E t h e tetracyclocondensation to
"porphyrinogen" and its oxidation with 2,3-dichloro-5,6dicyano-1,4-benzoquinone(DDQ) with addition of HC104.
Treatment of 7 with one equivalent of p-toluene sulfonic
acid in nitromethane at 80°C (10 min) gave the expected octaethyltetraselenaporphyrinogen8, albeit only in small amounts.
Analogous to the cyclocondensation of 2-(hydroxymethy1)[*] Prof. Dr. E. Vogel, Dr. C. Frode, Dr. A. Breihan, Dr. H. Schmickler,
Dr. J. Lex
Institut fur Organische Chemie der Universitat
Greinstrasse 4, D-50939 Koln (Germany)
Fax: Int. code (221)470-5057
[**I We thank Prof. Dr. J. Hahn and Bruker Analytische Messtechnik GmbH,
Karlsruhe for measuring the 77SeNMR spectra.
+
Angew. Chem. Inf. Ed. Engl. 1997,36, No. 23
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7
P-TsOH
8
1. DDQ
2. HClO4
1
9
SbCI,
4
1
L
6.2 C1040
10 . (SbxCly)30
3,4-diethylthiophene,@lthe macrocycle 9, which contains five
selenophene units, was also formed. The complex reaction
mixture was worked up conventionally in order to isolate the
cyclocondensation products 8 and 9. These were then further
purified by chromatography using silica gel and n-hexanel
dichloromethane (311). The first fraction contained several
open-chain condensation products (all in less than 1YOyield),
after which 8 and 9 were eluted together.["] It proved
expedient to treat this fraction, after removal of the eluent,
with n-hexane. This treatment left the major amount of 8
undissolved, and it could be filtered off. Chromatography of
the filtrate with n-hexaneltoluene (4/1), again on silica gel,
finally allowed the remainder of 8 (first fraction) to be
separated from 9. Recrystallization of both compounds from
ethanol yielded 8 as colorless needles (m.p. 220-222°C) and 9
as an amorphous colorless powder (m.p. 130-132"C, yield in
each case 3 YO).The homologous compounds 8 and 9 could
not be differentiated by NMR spectroscopy, and were thus
assigned structurally on the basis of their mass spectra.
The tendency of 8 to form is very noticeably lower than that
of its oxygen and sulfur analogues, which is probably due to
the large increase in the angle between the exocyclic bonds at
the a positions of the heterocycle (from 147" to 156")[121on
going from thiophene to selenophene; such a change favors
the formation of open-chain compounds. The helical effect[13]
of the ethyl groups, to which the relatively high yields of
porphyrinogens from 2-(hydroxymethyl)-3,4-diethylfuranand
-thiophene is ascribed, evidently plays a negligible role in the
case of 7.
Oxidation of octaethyltetraselenaporphyrinogen(8) to give
the octaethyltetraselenaporphyrin dication 6 (as its perchlorate) proceeded smoothly: 8 was heated to 80°C in glacial
acetic acid with DDQ ( 3 mol equiv) for 30 min and the
reaction mixture was then treated with 70% perchloric acid
2610
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(1:lO in HOAc; 5 mol equiv). Compound 6 was formed and
separated upon cooling of the solution as a microcrystalline
green powder. This was taken up in a small amount of
trifluoroacetic acid, layered with three times the volume of
acetic acid, and left to crystallize. After two days 6 had
precipitated in the form of metallic green needles, which
contained two equivalents of trifluoroacetic acid (material
used for X-ray structure analysis). Heating the crystals to
50°C under vacuum (0.01 Torr, 2 d) gave analytically pure 6 as
a stable, very hydrolytically sensitive compound in 58 Y yield.
The 'H NMR spectrum (CD3N0,) of 6 is very similar to the
spectra of the oxygen and sulfur analogues 4 and 5. In accord
with the presence of an aromatic dicationic porphyrin, the
singlet for the meso-protons (H,) occurs at very low field (6 =
12.10, see Table 2). The slight high-field shift of the H, signal
in 6 compared to that in 5 (Ad =0.43) most likely arises from
the fact that the ring system in 6, due to the larger van der
Waals radius of the heteroatoms (S: 1.85 A, Se: 2.0 A), is
more deformed than that in 5. The I3C NMR spectrum of 6,
which as expected contains five signals, corresponds well to
that of the sulfur analogue. On the basis of Se-H coupling
(?I(Se,H,) = 10.8 Hz), an inverse 'H - 77Se NMR spectrum
could be obtained, which indicated a chemical shift for the
77Se nucleus of 6=747 (standard: (CH,),Se). The UV/Vis
spectrum of 6 in formic acid has a flattened maximum at
483nm (~=61800),which can be interpreted as a bathochromically shifted SBret band, but displays relatively high
absorption (A = 700- 800 nm, E x 9000) at longer wavelengths
(in the Q band region); however, defined energy transitions
cannot be recognized.
An X-ray crystallographic analysis of the octaethyltetrareveals that
selenaporphyrin dication (6, as its per~hlorate)['~1
the molecule has a nonplanar ring conformation, as shown in
Figure 1. In accordance with the established centrosymmetry
of the dication, the four selenophene rings are twisted from
the molecular plane (defined by the four meso-carbon atoms)
in the sense of a syn,syn,anti,anri arrangement. The twist
angles of the selenophene rings are 24.3" and 30.5", respec-
Figure 1. Structure of 6 in the crystal (top: plan view; bottom: side view; ethyl
groups are omitted for clarity). Selected bond lengths [A] and bond angles ["I;
the vibrational ellipsoids represent 40 % probability.
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Table 2. Selected physical data for 6-14[a].
tively, and thus are significantly greater than those of the
thiophene rings in the corresponding sulfur compound 5
6: IH NMR (CD,NO,): 6 = 12.10 (s, 4 H ; H,,,), 4.16 (9, 16H; CH2), 1.79 (t, 24H;
CH,); I3C NMR (CD,NO,): 6 = 173.39, 160.72, 138.21, 25.44, 17.74; 77SeNMR
(19"), which likewise exhibits centrosymmetry. q e shortest
(CD,NO,): 6 = 747; MS (FAB): mlz 1%): 793 (100) [M' - 2 CIO,]; IR (CsI): a=
Se ...Se distance in 6 is 2.9 A, that is more than 1 A Iess than
2969,2933,2873,1452, 1399,1369,1350, 1213,1173, 1130, 1105,1083,625 cm-';
double the van der Waals radius of the selenium atom. The
UVNis (HCOOH): A,,, (E) =483 nm (61800), 700-800 (9000)
simplicity of the NMR spectra indicates that in solution 6 (like
7: 'HNMR(CDCI3):6=7.45(s,lH;H-5),4.74(s,2H;H-2a),2.90(s,1H;OH),
5) is a dynamic molecule, in which the hetero five-membered
2.50 (q.2H; H-3a), 2.48 (q.2H; H-4a), 1.24 (t, 3 H ; H-4b), 1.07 (t, 3 H ; H-3b);
' C N M R (CDCI,): 6=146.10, 143.89, 141.25, 121.85, 59.86, 23.75, 21.10, 15.00,
rings exchange sites rapidly by conformational processes.
13.44; MS (GC-MS, EI, 70eV): m / z (YO):218 (65) [M7],
189 (45), 137 (100); IR
The most remarkable chemical transformation of the
(film): ?=3334,2964,2931, 2872, 1460, 1375, 1305, 1185, 1143, 1100, 1004, 924,
dication 6 is its exhaustive reduction to the dianion 11,[15]798,782,728 cm-I; UViVis (CH,CI,): A,, (E)=257 nm (7400)
achieved by a potassium mirror in deuterated THF at
8: 'H NMR (CDCI,): d=4.05 (s, 8 H ; HJ, 2.42 (9, 16H; CH,), 1.06 (t. 24H;
- 78 "C (complete conversion after two days with formation
CH,); I3C NMR (CDC13): d = 143.69, 140.50, 30.40, 21.61, 15.19; 77Se-NMR
(CHJX,): 6=600; MS (FAB): m / z (Yo): 796 ( 5 ) [ M i ] , 307 (30). 154 (loo), 137
of a brown-red solution) .[I6] Whereas the sulfur compound 5
(60); IR (KBr): 5=2959, 2928, 2899, 2868, 2822, 1462, 1445, 1374, 1307, 1280,
reacts under these conditions to give predominantly poly1115, 1047, 937 cm-l; UVNis (CH,CI,): A,, (&)=258nm (25400)
meric products, 6 amazingly accepts four electrons smoothly
9: 'H NMR (CDCI,): 6=4.14 (s, IOH; H,,,), 2.45 (q, 20H; CH,), 1.08 (t. 30H;
to give the aromatic dianion 11with 22 n electrons. This was
CH,); "C NMR (CDCI,): 6 = 141.71, 140.60,30.61,21.68,15.16; MS (EI, 70 eV):
clearly identified by the ' H NMR spectrum (analogous to that
m / z (Y): 996 (60) [ M ' ] , 967 (70), 201 (100); IR (KBr): d= 2962,2928,2869,1451,
1375, 1311, 1293, 1119, 1048, 930cm-'; UViVis (CH,CI,): A,,
( ~ ) = 2 5 7nm
of 6 ) , the I3C NMR spectrum (five signals), and the inverse
(38 900)
'H -77Se NMR spectrum (singlet, Table 1). That the signal of
10: 'H NMR (CD3NO2):6 = 14.78 (s, 5 H ; H,), 5.71 (q.20H; CH?),2.56 (t. 30H;
the meso protons of 11is only shifted by AS = 1 to higher field
NMR (CDjNO,): d = 170.43, 162.93, 136.07, 28.37, 20.07; MS (FAB):
991 (100) [M+]; IR (CSI): P=3526,2968,2930,2870, 1521, 1473, 1448,
1419, 1373, 1308, 1256, 1183, 1110, 1052, 983, 925, 838cm-'; UVlVis (CH2C12,
0.2% SbC15):A,,,=551. 778, 856 nm (E on the basis of mixed counterions, not
exactly defined)
11: 1HNMR([D~]THF):d=11.03(s,4H;H,,,),4.01
(9. 16H;CH,), 1.98(t,24H;
CH,); "C NMR ([DJTHF): 6 = 131.12, 126.08, 107.45, 24.48, 18.21; 77Se-NMR
([D,]THF): 6 = 586
12[10]: 'H NMR (CDCI,): 6=3.64 (s, 6 H ; CH,), 3.29 (s, 4H: CH,); "C NMR
(CDCI,): 6 = 171.07,52.24, 23.14; MS (EI, 70 eV): d z (%): 226 (15) [M'], 194
(35),167(15), 152(10),94(15),74(20),45 (lOO);IR(Film):G=3003,2953,1733,
1437, 1409, 1270, 1109, 1010, 878, 770, 669 cm-'; UVlVis (CH?CI,): A,,
(E)=
242 nm (900)
13[10]: IHNMR(C,D,): 6=3.30(s,3H;CO0CH3),2.90(q,2H;H-4a),2.81
(4,
2H;H-3a), 1.15 (t,3H;H-4b), 1.13 (t,3H;H-3b);I3C-NMR (C,D6):6= 169.18,
163.25, 156.74, 155.29, 137.15, 134.84, 51.73, 22.75, 22.64, 14.92. 14.85; MS (El,
70 eV): m/z (%): 290 (100) [ M + ]275
, (go), 257 (95),91 (65); IR (KBr): P=2982,
2875,1715,1680,1653,1541,1277,1264,1249,1229,1153 cm-'; UVNis (CH,CI,):
A,, ( ~ ) = 2 9 4nm (13700)
14[10]: 'HNMR(CDC13):6=7.72(s, 1H;H-5),3.80(s,3H;COOCH3),2.93(q,
2H; H-3a),2.50 (q,2H;H-4a), 1.23 (t,3H; H-4b). 1.13 (t,3H: H-3b);"CNMR
(CDCI,): 6=163.96, 154.08, 147.40, 130.32, 129.79, 51.65, 23.63, 22.28, 14.17,
13.59; MS (EL 70eV): m/z (%): 246 (100) [ M + ] 231
, (SO), 215 (90). 91 (80); IR
(film): 5=2968, 2874,2837, 1709, 1547, 1452, 1383, 1309, 1233. 1189, 1167, 1112,
1088, 1059, 1023 cm-I; UViVis (CH,CI,): I,,, (E)= 270 nm (10800)
CHJ;
m/z
Table 1. Characterististic NMR data for 6[a] and ll[b].
6
6 H,
6 c,,,
6 Se
6
12.10
138.21
747 (II(Se,H,) = 10.8 Hz)
11
11
11.03
107.45
586 (3J(Se,H,)
= 14.9 Hz)
[a] 'H-NMR 300 MHz, I3C-NMR 75.5 MHz, "Se-NMR 57.2 MHz, CD,N02.
[b] IH-NMR 300 MHz, "C-NMR 75.5 MHz, 77Se-NMR76.3 MHz, [D,]THF.
with respect to that of 6, indicates that despite the negative
charge on 11 strong deshielding is still prevalent. Thus the
dianion maintains a pronounced diamagnetic ring current. On
going from dication6 to dianionll the center of I3C
resonances of the twenty perimeter carbon atoms is shifted
to higher field by AS = 36. This corresponds roughly to the
value of 32, which is the value expected for 6 as derived from
the empirical Spiesecke - Schneider
between
charge density and chemical shift in (4n + 2)n-electron
The cyclocondensation product 9, which contains five
selenophene rings. should be capable of being oxidized[*]to
the potentially aromatic 22n-electron decaethylpentaselenapentaphyrin trication (10). Thus 9 was treated with antimony(v) chloride in dichloromethane. A saltlike product was
obtained (green needles with a metallic luster), whose
cationic component was unambiguously shown to be the
desired trication by NMR spectroscopy (Table 2). Isolation of
10 with a uniform counterion remains to be accomplished,
since the anionic component of the oxidation product is a
mixture of different chloroantimonate ions.
After the successful synthesis of cationic oxygen, sulfur, and
selenium analogues of the porphyrins (the chalcogenaporphyrins with the exception of the tellurium compound),
attention is now focussed on the fascinating neutral tetraAngew Chem. Int. Ed. Engl. 1997,36, No. 23
I
T
(Yo):
[a] 'H NMR 300 MHz, "C NMR 75.5 MHz, 77SeNMR 57.2 or 76.3 MHz. Apart
from 10 (mixture of chloroantimonate counterions) and 11 (generated in an
NMR experiment), correct elemental analyses were obtained for all compounds.
phosphaporphyrins as the remaining synthetic challenge in
the field of porphyrin derivatives, which are derived from the
parent tetrapyrrolic macrocycle by substitution of the nitrogen atoms for other heteroatoms.
Received: May 13, 1997 [Z10434IE]
German version: Angew. Chem. 1997,109,2722 - 2725
Keywords: aromaticity
phyrinoids selenium
-
- heterocycles - macrocycles - por-
[I] E. Vogel, W. Haas, B. Knipp, J. Lex, H. Schmickler, Angew. Chem. 1988,100,
445; Angew. Chem. Int. Ed. Engl. 1988, 27, 406; W. Haas, B. Knipp, M.
Sicken, J. Lex, E. Vogel, ibid. 1988,100,448and 1988,27409; for expanded
tetraoxaporphyrin dications see: G. Markl, H. Sauer, P. Kreitmeier, T.
Burgemeister, F. Kastner, G. Adolin, H. Noth, K. Polborn, rbid. 1994, 106,
1211 and 1994, 33, 1151; R. Bachmann, F. Gerson, C. Putz, E. Vogel, J
Chem. SOC.Perkin Tram. 2,1996,541.
[2] a) For mono- and dioxaporphyrins see: A. W. Johnson in Porphyrins and
Metalloporphyrins (Ed.: K. M. Smith), Elsevier, Amsterdam, 1975, p. 729;
b) L. Latos-Graiynski, E. Pacholska, P. J. Chmielewski, M. M. Olmstead,
A. L. Balch, Angew. Chem. 1995, 107, 2467; Angew. Chcm. Int. Ed. Engl.
0 WILEY-VCH Verfag GmbH, D-69451 Weinheim, 1997
0570-0833i9713623-2611$ 17.50+.50/0
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COMMUNICATIONS
[3]
[4]
[5]
[6]
[7]
[8]
[Y]
[lo]
1995,34,2252; c) dioxa-5-oxophlorins are described by T. D. Lash, Y. L. S.T. Armiger, J. Heterocycl. Chem. 1991, 28, 965; T. D. Lash, J. Org. Chem.
1992,57,4312.
Monooxa- and 21,23-dioxaporphyrins can form paramagnetic Ni”C1- and
Ni”C1, complexes, respectively, with nickel chloride (the latter with
pseudooctahedral coordination geometry): P. J. Chmielewski, L. LatosGrazynski, M. M. Olmstead, A. L. Balch, Chem. Eur. J. 1997, 3, 268; Z.
Gross, Technion, Haifa (Israel), personal communication.
R. Bachmann, F. Gerson, G. Gescheidt, E. Vogel, J. Am. Chem. SOC. 1992,
114, 10855; E. Vogel, Pure Appl. Chem. 1993,65,143.
E. Vogel, P. Rohrig, M. Sicken, B. Knipp, A. Herrmann, M. Pohl, H.
Schmickler, J. Lex, Angew. Chem. 1989,101, 1683; Angew. Chem. Int. Ed.
Engl. 1989, 28, 1651.
There are a number of reports on mono- and dithiaporphyrins as well as
diselenaporphyrins: a) M. J. Broadhurst, R. Grigg, A. W. Johnson, J. Chem.
SOC.C 1971,3681; b) A. Ulman, J. Manassen, J. Am. Chem. SOC. 1975, 97,
6540; c) A. Ulman, J. Manassen, F. Frolow, D. Rabinovich, ibid. 1979,101,
7055; d) R. L. Hill, M. Gouterman, A. Ulman, Inorg. Chem. 1982,21,1450.
For the coordination chemistry of monothia- and monoselenaporphyrins
see: e) L. Latos-Graiynski, J. Lisowski, M. M. Olmstead, A. L. Balch, J. Am.
Chem. SOC.1987,109,4428;f) Inorg. Chem. 1989,28,1183; g) R. P. Pandian,
T. K. Chandrashekar, J. Chem. SOC. Dalton Trans. 1993, 119; h) M.
Ravikanth, T. K. Chandrashekar, Struct. Bonding (Berlin) 1995, 82, 105; i)
L. Latos-Grazynski, E. Pacholska, P. J. Chmielewski, M. M. Olmstead, A. L.
Balch, Inorg. Chem. 1996,35, 566; j) a monoselenasapphyrin was reported
by J. Lisowski, J. L. Sessler, V. Lynch, Inorg. Chem. 1995,34, 3567.
E. Vogel, J. Dorr, A. Herrmann, J. Lex, H. Schmickler, P. Walgenbach, J. P.
Gisselbrecht, M. Gross, Angew Chem. 1993, 105, 1667; Angew. Chem. Int.
Ed. Engl. 1993,32, 1597.
E. Vogel, M. Pohl, A. Herrmann, T. WiB, C. Konig, J. Lex. M. Gross, J. P.
Gisselbrecht, Angew. Chem. 1996,108, 1677; Angew. Chem. Int. Ed. Engl.
1996,35,1520.
Monotelluraporphyrins are already known, see refs. [2b] and [6c,i]. There
should be no doubt as to the viability of the octaethyltetratelluraporphyrin
dication, since octaethyl-N,N’,N”,N’”tetrametbylporphyrin dication is both
stable and aromatic, even though its ring skeleton is very strongly
nonplanarjsl Despite the advances in the chemistry of tellurium (see N.
Petragnani, Tellurium in Organic Syntheses, Academic Press, London,
1994), the synthetic route to the tellurium analogue of 4, 5, and 6 still
appears to be strewn with difficulties.
The new compound 7 can be obtained according to the following reaction
scheme (in analogy to the corresponding thiophene [S]). For the preparation
of the required 12 from Na,Se and methyl chloroacetate see: H. Rheinboldt
in Methoden Org. Chem. (Houben-Weyl), 4th. ed. voi9, p. 976:
13: R = COOH
+ b
14R=H
12
7
a) tBuOK in tBuOH, 1 h, 25°C; crude 13 is sufficiently pure and is used
directly; analytical sample: colorless crystals, m.p. 158°C (n-hexane). b) Cu/
ca. 300°C. 0.5 h; 14 was purified by chromatography on silica gel, first with
n-hexane (separation of diethylselenophene) then with n-hexanelethyl
acetate (Yl), and isolated in 38% yield; colorless crystals, m.p. 18°C (from
n-hexane). c) LiAIH, in THF, 1 h, 25°C; 7 precipitated from n-hexane as a
colorless, mother-of-pearl-like solid, m.p. 21 ‘C (yield 94 %).
I l l ] The compounds 8 and 9 were identified on the basis of their characteristic
violet color, which appeared on the thin layer chromatograms [n-hexanel
toluene (4/1)] after treatment with nitric acid vapor (the color of the first
fraction disappeared after a short time).
1121 Calculated from the relevant bond angles for thiophene and selenophene
given in C. W. Bird, G. W. H. Cheeseman in Comprehensive Heterocyclic
Chemistry, Vol. 4, Part 3 (Eds.: A. R. Katritzky, C. W. Rees), Pergamon,
Oxford, 1984, p. 3.
[13] B. Franck, A. Nonn, K. Fuchs, M. Gosmann, Liebigs Ann. Chem. 1994,503;
G. Bringmann, B. Franck, ibid. 1982,1272; see also L. F. Tietze, H. Geissler,
Angew. Chem. 1993,105,1087; Angew. Chem. Int. Ed. Engi. 1993,32,1038.
[14] Crystal structure data for 6 . 2 CF3COOH: C36H,C120,Se, . 2 CF3COOH,
M , = 1219.51,crystals from CH3COOH/CF3COOH(3/1); crystal dimensions
0.25 x 0.18 x 0.15 mm?, monoclinic, space group P2,/n, a =7.9260(10), b =
22.651(6), c=13.146(3)
B=98.12(2)”, V=2336.5(9)A3, 2 = 2 , pEaicd=
1.733 gem-); F(000) = 1212; p M o= 3.337 mm-‘; 4536 measured reflections,
=25”; R1=
3854 independent, 2038 observed reflections ( F ; >20F;);
0.0940, wR2 = 0.1868. Enraf-Nonius CAD4 diffractometer (room temperature, Mo,, irradiation, 1 = 0.71069 A). The structure was solved by direct
methods and refined with F 2 for all independent reflections (heavy atoms
with anisotropic temperature factors, the positions of the H atoms were
”2.
used: MolEN
calculated); wR2 = ( a v ( F k - F ~ ) 2 / u w ( F ~ ) 2 \Programs
A,
2612
0 WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1997
(Enraf-Nonius) for structure determination and SHELXL-93 (G. M.
Sheldrick, University of Gottingen) for refinement. Calculations were
carried out at the Regionales Rechenzentrurn der Universitat Koln. The
crystallographic data (excluding structure factors) for the structures
reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-100418.
Copies of the data can be obtained free of charge on application to The
Director, CCDC, 12 Union Road, Cambridge, CB21EZ, UK (fax: Int code
+(1223)336-033; e-mail: deposit@chemcrys.cam.ac.uk).
1151 Cyclovoltammetric studies on 6 indicate two reduction waves, which in
terms of the electron transitions cannot be interpreted unambiguously
because of the strong broadening.
[I61 The reduction took place under an inert atmosphere in a reaction flask that
was connected through a frit to a NMR tube.
(171 H. Spiesecke, W. G. Schneider, Tetrahedron Lect. 1%1,468; B. Eliasson, U.
Edlund, K. Mullen, J. Chem. SOC. Perkin Trans. 2 1986, 937; G. A. Olah,
G. D. Mateescu, J. Am. Chem. SOC.1970, 92, 1430.
1181 The fairly good correlation of experimental and calculated A6 values is
astonishing, because the possibility that the heteroatoms in both 6 and 11
could carry charge was not taken into consideration.
Contracted Porphyrins: Octaethylisocorrole**
Emanuel Vogel,* Beate Binsack, Yvonne Hellwig,
Christoph Erben, Andreas Heger, Johann Lex, and
Yun-Dong Wu*
Dedicated to Sir Alan Battersby
The tetrapyrrolic aromatic macrocycle corrole 1,pioneered in
the 1960sby A. W. Johnson[’] (and related structurally to vitamin
B,J2]through corrin), is the prototype of the “contracted porphyrins”. In analogy to porphyrin, compound 1 is distinguished
by an 18 JC main conjugation pathway, but has three internal NH
hydrogen atoms, making it a potential trianionic ligand. As has
been documented by publications from a series of research
groups, 1 readily undergoes complexation to yield corrolates
with numerous metal ions, in particular those of trivalent
metals.I31 The ability of the corrole ligand to stabilize metal
ions in higher oxidation states has recently been established.E4I
This, along with the most recent synthesis of bis-c~rroles,[~~
corrole heterodimer~)~]
and meso-phenyl-substituted metallocorrolates[61have all played a part in bringing the chemistry of
corroles out of the shadows of porphyrin chemistry.
Starting from the conceptualization of structural isomers of
porphyrin with N, coordination, four of which-porphycene,
hemiporphycene, corrphycene, and isoporphycene-have already been synthesized,17]it is a logical step to consider the
possible existence of isomers of corrole. While porphyrin has no
fewer than seven isomers, the absence of one meso unit reduces the possible number of isomers under discussion in the
case of 1 to three: compounds 2 -4. These are given in Table 1
in order of their relative energies (with respect to l),calculated
by the PM3 and BLYP/6-31G**//3-21G methods; the relative
energies listed refer to the most stable NH t a u t ~ m e r . [ ~ , ~ ]
[*] Prof. Dr. E. Vogel, Dr. B. Binsack, Dr. Y . Hellwig, Dr. C. Erben, A. Heger,
Dr. J. Lex
Institut fur Organische Chemie der Universitat
Greinstrasse 4, D-50939 Koln (Germany)
Fax: Int code + (221)470-5057
Prof. Dr. Y.-D. Wu
Department of Chemistry
The Hong Kong University of Science and Technology
Clear Water Bay, Kowloon, Hong Kong (China)
Fax: Int code +(2358)1594
[**I This work was funded by the Deutsche Forschungsgemeinschaft and the
Fonds der Chemischen Industrie.
0570-0833/97/3623-2612$ 17.50+.50/0
Angew. Chem. Int. Ed. Engl. 1997.36, No. 23
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