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Bis(dicyanomethylene) and Bis(cyanoimino) Derivatives of Indigo and Thioindigo.

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[6] The synthesis and X-ray structures of complexes la -d will he reported elsewhere: G. C. Lloyd-Jones, A. Pfaltz, Z . Nuturforsrh. B, in press.
[7] Uncdtalyzed reactions (c(substrate) = 0 . 0 9 ~in THF, 2.6 equiv of NaCH(CO,Me),, 60°C) gave exclusively the achiral regioisomers (81 % 10a from 5 a
after 18 h; 58% 8 from 7 after 24 h). At -13°C: ca. 1 YOconversion in two
weeks ( 0 . 0 7 5a,
~ 5.5 equiv of NaCH(CO,Me),).
[8] Reaction of [W(CO),(CH,CN),] with NaCH(CO,Me), in the presence of 2 a
resulted in much lower activity. In the absence of NaCH(CO,Me),,
[W(CO),(CH,CN),] presumably reacts with 2a and 5 a or 7 to generate analogues of l b, resulting in lower reactivity and poor regioselectivity.The importance of adding NaCH(CO,Me), before the substrate has also been noted with
W(bpy) catalysts (ref. [5b]).
191 [W(CO),(CH,CN),] reacts with Za ('H, 3'P N M R , [DJTHF) to yield a mixture including l c . 1 d, and [(2a),W(CO),]. the ratios of which depend on the
relative amounts of the starting compounds (ref. [6]). Compound 1 d is inactive
as a catalyst.
[lo] Substrates 5a-e were prepared from the corresponding aromatic aldehydes:
(1) CH, = CHMgC1, TH E 25 "C, 60-83%; (2) Ac,O, Et,N. DMAP, CH,CI,,
25 .C. 86-96%; (3) [Pd(CH,CN),CI,] (1 mol%), THF 25 "C. 68-97%; (4)
MeOH, K,CO, (cat), 25 "C, 47-81%: (5) (EtO),POCl. C,H,N, DMAP,
CH,CI,, 25 "C, 50-80%.
[ll] P. von Matt. Dissertation, University of Basel, 1993.
[12] D. P. Tate, W. R. Knipple, J. M. Augl. Inorg. Chem. 1962. 1 , 433.
NC)-CN
la: x = s
lb:~=S02
NC
?vCN
3
and 3. The crystal structure analysis['] of 4b (Fig. 1 ) shows that
the phenyl ring avoids interaction with the dicyanomethylene
groups by twisting out of the plane of the tricyclic system. In
contrast, the bond to the dicyanomethylene group (C2-C9) is
only slightly twisted (8.3").
Bis(dicyanomethy1ene) and Bis(cyanoimino)
Derivatives of Indigo and Thioindigo""
Rudolf Gompper," Karsten Hartmann,
Robert Kellner, and Kurt Polborn
Indigo and related compounds are of great technical importance owing to their properties as dyes. The indigo chromophore
giving this class of relatively small and simple molecules their
characteristic intense color has been the subject of numerous
investigations."] Surprisingly, no indigo derivatives are known
in which the 0 atoms of the carbonyl groups have been replaced
by other electron-withdrawing groups. We report here on our
successful synthesis of compounds of this type.
In our studies we focused on dicyanomethylene and cyanoimino groups, in particular, as acceptor groups. (The analogy between dicyanovinyl and carbonyl functions was discussed in detail
previously."]) Since these groups extend the .rr-electron system, it
was expected that the resulting chromogens would absorb at
longer wavelengths, possibly even in the near-IR ( > 700 nm). An
additional bathochromic shift due to the twist of the compounds
about the central double bond as a result of steric repulsion may
also contribute (cf. ref. [3]).
A typical method for the synthesis of indigoid dyes is the condensation of compounds such as indolin-3-one ("indoxyl") or
benzo[b]thiophen-3(2H)-one ("oxythionaphthene") with anils
like 2-phenyliminoindolin-3-one ("isatin-2-anil") .I4]However,
the reaction of benzo[b]thien-3-ylmalodinitrile 1a['] with anil 3
in acetic anhydride/glacial acetic acid did not lead to the desired
thioindigo derivative 2. Instead an unusual reaction sequence
produced a poorly soluble, dark blue compound (A,,, = 662 nm
(DMSO)), which we assign structure 4 a based on its analytical
and spectroscopic data (which are similar to those of the better
characterized 4 b). To our knowledge, compounds of this type
have not been described previously. The analogous compound 4 b
(A,,
= 590 nm (DMSO)) was prepared from sulfone 1 bLSb*
Fig. 1. Crystal structure of 4 b [7) (ORTEP plot). Selected bond lengths [A] and
angles ["I: C1-N 127.3(7),C1-C2 1461(8), C I S 1 180.1(4), C2-C9 136.1(6), C9-ClO
144.3(8), C9-Cll 142.5(9), C10-N4 141.1(8), C11-N5 113.1(8), Cl2-Nl 142.0(7),
C12-N2 133.6(8). C13-C22 142.7(7), C22-N3 112.9(7), C14-Cl5 138.6(6), C15-Nl
134.3(8), C15-S2 171.9(6), C16-S2 177.0(5); Cl-N2-C12 134.5(4), C1-Sl-C8
92.8(2), C12-Nl-Cl5 107.8(4), C15-S2-C16 89.5(3); Cl-C2-C9-C10 6.39(0.87), C1C2-C9-C1I 1.61(0.55), C3-C2-C9-Cll6.22(0.91). C3-C2-C9-C10 10.99(0.53),C12Nl-C23-C24 46.87 (0.52), C15-Nl-C23-C28 48.30(0.54).
Thioindigo can be obtained, for example, by treatment of
2-bromobenzo[b]thiophen-3(2H)-one with base or by reaction
of its 2,2-dibromo derivative with ben~o[b]thiophen-3(2H)-one.[~~
Despite extensive efforts we were not able to prepare either the
mono- or dibromo derivative of 1 a because of the instability of
the products. However, treatment of a solution of 1 a in chloroform at room temperature with bromine, followed by addition
of triethylamine gave the yellow bi(benzothiophene) derivative 5
NC CN
[*] Prof. Dr. R. Gompper, Dr. K . Hartmann, Dr. R. Kellner, Dr. K. Polborn
lnstitut fur Organische Chemie der Universitit
[**I
464
Karlstrasse 23, D-80333 Munchen (Germany)
Telefax: Int. code + (89)5902-420
This work was supported by the Deutsche Forschungsgemeinschaft and the
Fonds der Chemischen Industrie.
0 VCH
Verlugsgrsellschufi mbH, 0.69451 Wrinheim, 1995
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7
Angew. Chem. I n f . Ed. Engl. 1995, 34, No. 4
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in addition to a small amount of an isomeric yellow compound.
Electrocyclization of the cis derivative of 2 is presumed to provide
5. The UV/VIS spectrum of the side product
= 425 nm
(CH,C12)) indicates that it is not 2, which like its cis isomer
should absorb at much longer wavelengths.
In the crystal structure analysis[g1of 5 (Fig. 2) the twisted
cyclohexadiene ring apparently prevents an eclipsed arrangement of the nitrile groups. As a result the planes of the two
The conditions used for the conversion of 1 a into 5 or 7 did
not convert indole derivative 8[5b,31 into 9. However, oxidation
of 8 to give 9 was possible with silver salts in the presence of
organic bases. The best results were obtained with silver acetate
in a mixture of two parts water and one part imidazole at 100 ‘C.
Compound 9 forms as a dark green, poorly soluble powder and
’
AgOAc
N1
c10
8
k
‘”c4cN
9
10a
Nla
[A] and
angles 1-1: C1-Cla 145.1(6), C2-C9 152.4(4), C9-C9a 161.2(6), C2-C3 143.9(4),
Cl-SI 170.70). C9-Cl0 148.9(5), C9-Cll 147.7(4); C2-Cl-Cla 121.8(2), C2-C9C9a 109.32). Cl-C2-C3 113.3(3). ClO-C9-C11 10X.5(3). Sl-Cl-C2 113.4(2), C2C3-C4 109.7(3), Sl-C4-C3 112.5(2). Cl-Sl-C4 91.1(1).
Fig. 2. Crystal structure of 5 191 (ORTEP plot). Selected bond lengths
I l a : R = H v W /
I l b : R = Br
I l c : R = OMe
benzo[h]thiophene units are tilted in opposite directions forming
an angle of 17.8“. The extremely long single bond (C9-C9a;
161 pm) between the CN-substituted C atoms is especially noticeable. The conversion of 5 into 2 was not possible, even
though similar reactions are known for related systems.”
The most common approach for the synthesis of indigoid
compounds is the oxidative coupling of appropriate methyleneactive “monomers” and dehydration of the resulting “dimers”.
Reaction of 1a with oxidizing agents such as aerial oxygen and
potassium dichromate, which are used to convert benzo[b]thiophene-3(2H)-one into thioindigo, did not lead to 2 or 5 . However, l a can be lithiated with butyllithium in T H F at - 70 “C
and at the same temperature the lithium salt subsequently oxidized with iodine. The fleeting intermediate 6 undergoes ring
closure to give the cycloheptatriene derivative, whose structure
is similar to that of dimethylcycloheptadithiophenone.[’ We
attempted to prepare the dianion of 6 by addition of two further
equivalents of butyllithium and then oxidize it with iodine, but
this did not succeed.
In the crystal structure analysis[’21 of 7 (Fig. 3) the folding of
the seven-membered ring and the slight tilt of the benzo[b]thiophene planes in opposite directions are evident.
P
”
N4
Fig. 3. Crystal structure of 7 1121 (ORTEP plot). Selected bond lengths [A] and
angles [“I: Cl-C12 143.4(3), C1-C2 137.5(3), C2-C9 146.4(2), C9-Cll 136.5(3),
Cll-C20 153.8(3), C13-CZ0 152.6(3), C12-CI3 136.4(3), C1-S2 173.3(3), C8-S2
173.2(3), C3-CX 140.1(3), C2-C3 145.0(3); CI-C2-C9 123.9(2). C2-C9-C11
125.3(2), C1 I -C20-C13 107.4(1),C12-Cl 3-C20 117.5(2), Cl -C12-C13 126.1(2); C2CI-Cl2-Cl3 34.4(0.1), S2-Cl-Cl2-Sl - 34.0(0.2).
~
A n g i w Chem. l n r . Ed. Engl. 1995, 34. N o . 4
8
W
N\
U
CN
can be purified by extractive recrystallization from chlorobenzene. The “medium effect” known for indigo is especially interesting here. A thin layer of solid 9 on a quartz plate absorbs at
significantly longer wavelengths than in DMSO solution (A,,
=778 vs 746 nm).
The bis(cyanoimino) derivatives 11 of indigo are formed by
treatment of indoles with a solution of cyanogen azide in acetonitrile at reflux. In analogy to the conversion of olefins into
N-cyanoimines by cyanogen azide[l4] it can be assumed that
indoline derivatives 10 form as intermediates. which are then
oxidized by aerial oxygen to give 11. The longest wavelength
absorption of I l a in DMSO lies at 751 nm ( l l b : 765; l l c :
813 nm). Compounds 9 and 11 absorb at significantly longer
wavelengths than indigo (A,, (DMSO) = 621 nm), and are thus
new near-IR dyes.
Like indigo, 9 and 11 can be converted to colorless, water-soluble forms by treatment with alkaline sodium dithionite solution. For 9 this process is irreversible; in the case of 11 the dye
can be recovered by exposure to aerial oxygen or treatment with
Km(CN),I’
In conclusion the UVjVIS spectra of 9 and 11 display the
anticipated strong bathochromic shift relative to that of indigo.
Since crystal structure analyses of the new compounds are not
available, the bonding relationships in 9 and 11 must be derived
from AM3 calculation^.['^] These indicate that in contrast to
planar 11a, 9 has a convex structure, in which the planes of the
benzene rings are tilted towards each other forming an angle of
133 ’; the C atoms of the central C=C bond are only slightly cis
pyramidalized (4”). The pronounced distortion of the entire chromophore explains why 9 absorbs at somewhat shorter wavelengths than 11a, even though dicyanomethylene systems usuall y absorb at longer wavelengths than cyanoimine systems.[5b1
The fact that 9 could be prepared but 2 still remains elusive
points out that the gain in energy upon formation of two benzothiophene systems is a key contribution to the stability of 5.
Consistent with this, the putative “dithio-thioindigo” is actually
a 1,2-dithiine derivative[161and structurally comparable to 5.
VCH Ver/u~sh.ese//srhu/fr
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E-yperimental Procedure
green residue was extractively recrystallized from chlorobenzene. Yield 0.23 g
(38%); dark green timorphous powder, m.p. >350"C. IR (KBr): 11 = 3292. 2206.
3 . A solution of 1 a [5] (2.0 g, 10.09 mmol) in ethanol was treated with nitrosohen1605, 1590. 1406.1310, I221,747cm-'. - LJV;VIS (DMSO): i,,
=746.674,
,
435,
zene (1.18 g. 11.00mmol). After addition of O.2mL of piperidine, the reaction
CN), 331 (18.
395 nm. MS (245 'C): mi: ("/a) = 358 (100, M i ) , 332 (13, M'
mixture was stirred at room temperature for 30 min. The red precipitate was reM i HCN), 305 (1 I. M i - HCN - CN), 278 (18, M t - 2 H C N - CN), 180(5,
moved by vacuum filtration, washed with ethanol and ether, and recrystallized from
C , IHhN,).
ethanol. Yield 1.41 g (45%); dark red crystals, m.p. 165- 166 ' C . IR (KBr):
I 1 a : A solution of cyanogen bromide (3.70 g. 34.95 mmol) in 50 mL of anhydrous
UVWIS
Y = 3073.2216.1585, 1532, 1442.1328. 1295.1108.771. 728. 685cm-I.
acetonitrile was treated with sodium aride (2.60 g, 39.92 mmol) and stirred at room
(DMSO): i,,, ( I : ) = 515 nm (22390). - ' H N M R (400 MHz, [DJDMSO): 6 ~ 7 . 3 1
temperature for 90min. After the precipitate was filtered off. indole (4.0g,
(m,4H),7.41(d.'J=7.4Hz,IH),7.47(t.'J=8.1Hz,2H),7.57(t.'J=7.4Hz. 34.2 mmol) was added to the light yellow solution, which was then heated to reflux.
1 H). 8.60 (d, 'J = 8.2 Hz. 1 H). "CNMR (400 MHz. [DJDMSO): 6 =79.04.
After 1 h the resulting dark green precipitate was removed by vacuum filtration,
113.16, 114.00. 121.91. 124.02. 126.93, 127.52, 128.30. 128.60. 129.54. 135.86.
washed with hot acetonitrile, and dried. Crude yield 1.50 g (28%); purification by
142.95. 147.49. 156.99. - MS (245 C ) : in/: ( O h ) = 287 (100. M i ) , 261 (26,
recrystallization from xylene; fine blue-gi-een needles, m.p. >350 'C. 1R (KBr):
M i - C N ) , 184(40. M i - CN - Ph), 157 (3, M + - HCN CN - Ph). 77 (20.
1 = 3281. 2160, 1610, 1540.1456, 1312. 1109. 763 c m - ' . - LJV;VlS (DMSO): i,,,
Phi).
( I : ) =751 (28184). 5% (2240). 378 (11 220). 306nm (36310). - MS (245 'C): mi:
4a: A mixture o f 3 (0.17 g. 0.59 mmol). I a (0.14 g, 0.71 mmol). 5 g of acetic anhy(%) = 310 (76. M i ) , 284 (14. M' - C N ) . 283 (25, M i - HCN), 269 (6.
dride, and 1 g of glacial acetic acid was heated at reflux for 10 min. The reaction
Mi
HNCN), 257 (18. M i - HCN NCN), 181 (10, C,,H,N,),
156 (6.
mixture was cooled, and the dark blue precipitate removed by vacuum filtration.
C,H,N,). 155 (6. C,]H,N,).
washed with hot ethanol aiid ether. aiid recrystallized from a large volume of xylene.
Correct elemental analyses were obtained for all compounds.
Yield 0.1 1 g (39%); fine, blue-violet, metallic needles, m.p. 358-359 C . IR (KBr):
I' = 3030, 2216. 1585. 1511, 1436, 1411. 1289. 1112, 1064, 770. 761. 739 c m - ' . UV/VIS (DMSO): A,,, (c) = 662 (15140). 319 nm (11 750). - MS (250°C): in;:
Received. September 8, 1994 [Z7300IE]
(74) = 485 (26. M'
H,). 483 (100, M i ) . 458 (28. 485 - HCN). 432 (19,
German version: Angm. Cliem. 1995. 107. 531
458 - CN. 380 (9. M i - CN - Ph). 366 (7. M i - CN - NPh), 289 (9,
C,,H,,N,S). 274 (32, C,,H,,N2S), 261 (4. C,,H,N,S), 246 (7). High-resolution
Keywords : dyes . indigo derivatives . thioindigo derivatives
MS (250 C, ref. = 480.9697): m / z = 483.0626 (calcd. 483.0621)
4b: Conditions analogous to those for 4a were used but with 3 (0.65 g, 2.26 mmol)
and 0.52 g of 1 b [5h,6]. Yield 0.21 g (39%); blue-violet crystals: m.p. >350 C. IR
a) J. Fabian, H. Hartmann. Light Ahsorprion o/Orgunic Cdorunfs, Springer.
(KBr): r = 2 2 2 3 , 1595, 1539, 1436, 1383. 1322, 1227. 1170, 1052. 764. 745.
Berlin. 1980. p. 32. 115, 162; b) G. Miehe, P. Susse, V. Kupcik, E. Egert, M.
730cin-'. - UV!VIS (DMSO): i,,,, (c) = 590 (4470), 294 nm (10715). - MS
Nieger. G. Kunz. R. Gerke. 9. Knieriem, M. Niemeyer, W. Luttke. Angeu..
(200 C ) : m/: ('A)= 515 (12. M i ) . 451 (20. M ' -SO,).
424 (8.
Chon. 1991. 103. 1008; Angm.. Chem. I n / . Ed. Engl. 1991, 30, 964.
M' -SO, - HCN). 289 (100, C,-H,,N,S). 261 (25. C,,H,N,S). 246 (17). 212
a) K. Wallenfels. K. Friedrich. J. Rieser. W. Ertel, K . Thieme. A n g w . Chem.
(51. C,,H,N,OS), 184 (19).
1976, XX, 31 1 : Angrit.. Clicm. I n / . Ed. Engl. 1976. 15. 261: h) W. J. Middleton,
5: Compound 1 a (0.99 g, 5.00 mmol) was dissolved in 50 m L of anhydrous chloroV. A. Engelhardt, J. Am. Cheni. Soc.. 1958,80, 2788.
form under nitrogen. A mixture of bromine (0.80 g. 5.00 mmol) and 10 mL of
A. Beck, R. Gompper, K . Polhorn, H.-U. Wagner, Anxew. Chem. 1993, 105,
anhydrous chloroform was added dropwise to this solution. The reaction mixture
1424; Atrgeb~..C/?em.lnt. Ed, EngI. 1993, 32. 1352.
was stirred at room temperature for ca. 12 h. Then a mixture of triethylamine
a) A. Bezdrik, P. FriedlHnder. 5w. Drsch. CIiem. Gcs. 1908, 41, 375; b) R.
( 1 .I 1 g, 1 I .O mmol) and 7 mL of anhydrous chloroform was added dropwise. The
Pumnicrer, ihid. 1911, 44, 338.
reaction mixture was again stirred at room temperature for ca. 12 h before 500 mL
a) K. Hashimoto. M. Nishikuri, A. Takeshita (Sumitomo Chemical). JP-B
ofchloroform was added. The solution was Nashed successively with water, saturat60-220785. 1985 [Chew. Ahsrr. 1986, 105, 105845~1;h) R. Kellner, Dissertaed sodium bicarbonate solution. saturated sodium thiosulfate solution, and water.
tion, UniversitHt Miinchen, 1991.
The solution was dried over magnesium sulface. filtered and concentrated to drya) W. Baumann (Sandor), GB-B 2.026.528. 1980 [Chem. Absrr. 1980. 93,
ness. The residue was recrystallized from acetic anhydride. Yield 0.40 g (41 %); pale
48539el; h) W. Baumann (Sandoz), FR-B 2.438,045. 1980 [Chcm. Abstr. 1981,
yellowish platelets. m.p. 301 "C (decomp). The product was purified further by
94, 4953bl.
fractional crystallization from toluene, yielding in addition to 5 (pale yellow
Crystal structure analysis of 4b: A suitable crystal was obtained by vapor
platelets. m.p. 311 -312'C (decomp)) a small amount of an isomer (fine yellow
diffusion of ether into a solution of 4b in chloroform. C,,H,,N,O,S;
needles. m.p. ,360 C ) . 5: IR (KBr): 1' = 3060,2255,2248.1510. 1461.1436.1322,
CH,OH.CH,CN, M = 588.67 gmol- I . crystal dimensions 0.10 x 0.20 x
( I : ) = 386 (18620). 367
1315, 1242, 759. 727cm-'. - UV/VlS (CH,CI,): i,,,
0.50 mni,. triclinic, space group Pi (no.2), ( I = 892.7(2), h = 1222.7(4). c =
(23990), 350 (21 380). 329 (sh, 14450). 257 (17380), 228 nm (30200). - 'H NMR
1366.7(4) pm. c( = 64.64(2). 11 =76.83(2), 1' = 80.35(2)', V =13.085 nm', Z =
(400MH~,CDC1,):6=7.60(ddd.~J=8.1
Hz,'J=7.2Hz.4J=1.2H~,2H.H-3,
2. pirlLd
= 1.2273 gem-'. Enraf-Nonius CAD-4 diffractometer, p(MoK,) =
H-8),7.67(ddd. ' J = 8 . 4 H z . 3 J = 7 . 2 H z . 4 J = 1 . 2 H z . 2H. H-2.H-9).7.99 (mc.
2.400 cni- I. T = 294K. (1)scan, 28 range 4-46', maximum measurement time
' J = 8.1 Hz. 2 H . H-4. H-7). 8.46 (mc, ' J = 8.4 Hz, 2 H . H-I. H-10). "CNMR
120 s, scan width (0.75 0.35 tanfl) ,3805 reflections measured. of which 3625
(400MHz, CDCI,): 6 = 43.41, 109.31. 112.42. 121.78, 123.63. 127.25. 127.51.
were unique, and 2685 were classified as observed [ I > 3o(l)]. Structure refine134.39. 134.67, 139.73. - MS (90 C ) : /nj: (%) = 392 (100. M i ) , 366 (10.
ment with the SIR program package. least squares refinement with the system
M i - C N ) . 3 4 0 ( 3 1 . M t - 2 C N ) . 3 3 4 ( 4 , M ' - S C N ) . 3 2 8 ( 2 . M t -C,N2),327
MolEN, 376 parameters refined, R = 0.0559, R, = 0.0925, maximum residual
(3, M
C,HN,). 313 (1, M ' - HCN - 2CN). 308 (4. M i - 2 C N - S), 302 (6.
electron density0.776j-0.237 1 0 - h e p m - J . Furtherdetails ofthecrystal strucM i - CN - C,N,), 295 (4). 284 (2. M i - C,H,S). 196 (4, M 2 ' ) . 170 (4).
ture investigations may be obtained from the Fachinformationszentrum Karls7: Toasolutionof Ia(1.98g. 10.0mmol)in 7 5 m L o f a n h y d r o u s T H F a t -7O'C
ruhe. D-76344 Eggenstein-Leopoldshafen (FRG) on quoting the depository
under nitrogen was added dropwise a 1 5 % solution of hutyllithium in hexane
number CSD-58657.
(6.7 mL, I 1 .O mmol). After 30 min at room temperature the reaction mlxture was
a ) P. Friedliinder. Monorsh. C h m . 1908.29. 359; b) A. BeLdrik. P. Friedliinder.
again cooled to -7O'C, and iodine (1.27 g, 5.00 mmol) was added. The reaction
P. Koeninger. 5c.r. Di.wh. Chom Gc,.<.1908. 41. 227.
mixture was allowed t o warm slowly to room temperature, stirred for ca. 12 h, and
Crystal structure analysis of 5 : A suitahlc crystal was obtained from a solution
then poured into 400 m L of water with stirring. The initially formed oil crystallized
o f 5 in toluene. C,,H,N,S,, M = 392.4 g m o l - ' , crystal dimensions 0.3 x 0.3
after prolonged stirring. The crystals were removed by vacuum filtration and drled
x 0 , 6 m m 3 , monoclinic. space group C2:<,(no. 15). u =1435.4(3), h =
under vacuum. 1.46 g of the crude product was recrystallized from a large volume
942.6(2). c' = 131 1.4(4) pm, /j = 93.61(2) ', V = 1.7707 nm'. Z = 4, pCdlLe
=
of ethanol. Yield 0.96 g (49 %); pale pinkish platelets, m.p. 236 237 C. IR (KBr):
1.472
EnrdfNonius CAD-4 diffrdctometer, p(MoK,)
= 3.02 cm- I ,
Y = 3433, 3360, 3205. 3056, 2205. 1636, 1569. 1317. 1227. 766. 753, 735 c m - ' . T = 296K. (11 scan, 20 range 4 - 4 6 . maximum measurement time 120 s, scan
U V N S (DMSO): i.,,, (c) = 377 (2455), 341 (sh, 15490), 293 (35480). 265 nm
width (1.2 + 0.35tan0)". 1356 reflections measured. of which 1183 were
(22910). - ' H N M R (400 MHz. [DJDMSO): 6 =7.58- 7.71 (m. 4 H , aryl-H). 8.15
unique. and 1108 were classified as observed (12 3 a ( / ) ] .Structure solution
(~.2H,NH~).8.16(mc,1H.aryl-H),8.19(d,~J=8Hz,lH,aryl-H),8.40(mc,IH,
with SHELX-86. refinement with SHELXTL-PLUS. R = 0.0392. R, =
aryl-H). 8.69 (d, 'J = 8 Hz. 1 H , aryl-H). "CNMR (400 MHz, [D,]DMSO)0.0413. maximum residual electron density 0.22;-0.27 lO-'epm-'.
6 = 40.39, 73.29. 110.80. 115.28, 117.32. 121.77. 123 28, 123.6. 123.81, 125.48,
a ) K. Uchida. Y Nakayama. M. hie, Bid/. Clzrnr. Soc.. Jpn. 1990, 6 3 , 131 I ; h)
125.98. 126.40. 127 16. 127.71. 129.29. 133.36. 135.13. 136.07. 138.57. 140.03.
A. Pawlick. W. Griihn. A. Reisner, P. G. Jones, L. Ernst, Angnc. C/zrm. 1994,
345.28. - MS (195'C): m / z ( O h ) = 394 (28, M i ) , 368 (5. M i - CN). 341) (6.
106. 2058; A n g ( 2 ~C ~' / .t ~ ~ m
I n. / . Ed. Engf. 1994, 33. 1958.
M + - 2 H C N ) . 330 (100. M i - - C,N,). 302 (8. M i - C N - C,H2N2). 197 (4.
N. R. Krishnaswamy. C. S. S. R. Kumar. Iridiurr J. Chfm. Secr. 5 1992,31,449.
M " ) , 165 (5).
Crystal structure analysis of7: A suitable crystal was obtained by recrystallization from ethanol. C,,H,,,N,S,. M = 394.48 gmol-'. crystal dimensions
9:Toasolutionof5.0gofimidarolein 1 0 m L o f w a t e r a t 100 Cwasadded8[5b.12]
0.40 x 0.47 x 0.53 mm". monoclinic. space group P2,;c. (no. 14). u = 1264.1(3).
(0.75 g.3.3X mmol). After 1 min silver acetate ( 1 .SO g, 8.99 mmol) was added and
h = 9 0 8 . 3 ( 2 ) , ~ ~ = 1 6 2 1 . 5 ( 4 ) p m , / ~ = 9 8 . 3 3 ( V=1.8421
2)',
nm3.Z=4.pcaIc,=
the mixture stirred for 2 min. The mixture was vacuum-filtered while still hot and
the residue washed with boiling dimethylformamide (2 x 20 mL). The dark
1.422 gcm-'. Enraf-Nonius CAD-4 diffractometer. p(MoKz)= 2.909 c m - ' .
~
~
~
~
~
~
~
+
~
+
466
+
~
(1') VCH
Ver/ufisRPsL./l.~chuffr
m b H . D-694Jl Wrinherm, 1995
0570-0~33/Y5/0404-0466
$ I(J.OO+ .3/0
A n g c w . Cheni. In/. Ed. EngI. 1995. 34, No. 4
COMMUNICATIONS
I = 294K. t r i scan. 211 range 4-46 , maximum measurement time 60s. scan
\bidth (0.11 0.35tiin0) , 2843 reflections measured. of which 2495 were
unique. diid 2368 were classified as observed [I > 3a(/)]. Structure solution
with SHELXS-86. refinement with SHELXTL-PLUS, R = 0.0291. R, =
0.0310. m;ixniium residual electron density 0.22/-0.19 10-bepm-'.
V. S. Vele-/heva. V. P. Sevodin, V. Y. Erofeev. N. K . Genkina. T. A. Korik, V. V.
Vxmpilow. N. N. Suvorov. Khim. G e w r o ~ i k lSoedtn.
.
1977. 360: Chem. Ahs/r.
1977. 87. 102157~.
F. D. Mar\h. M. E. Hermes. J. A m . Clirm. SOC.1964, 86.4506.
We thank Dr. U Thibaut, Fa. Byk-Golden. Konstanr (FRG). for conducting
thu AM1 calculations.
W. Schroth. pcr5on;il communication. 1990: W. Schroth. E. Hintzsche. M.
Fclicetti. R. Spitsner, J. Sieler. R. Kempe, A n g i w Chem. 1994. 106. 808;
.Aticyii.. ( ' / w m . / ! I / . GI. E/7,q/. 1994. 33. 739; W. Schroth, E. Hintrsche. H. Viola.
R. Winklrr. H. Klose. R. Boese. R. Kempe, J. Sieler. C'hivii. B w . 1993. 127.401 ;
W. Schroth. bl Felicetti. E. Hintzsche. R . Spitzner. M. Pink, E/ru/rrdronLrrt.
1994, 3.i. 1977
+
[I 31
[14]
[15]
(161
A Cyclic Hexairon(rI1) Complex with an
Octahedrally Coordinated Sodium Ion at the
Center, an Example of the [12]Metallacrownd
Structure Type**
diffraction study reveals that 2 has precisely the same overall
ring structure as that proposed for the [Fe,(OH),,]6+ core in 1,
and surprisingly that this ring serves as a host for the sodium
ion.'" Compound 2 thus qualifies as an authentic example of the
[12]metallacrown-6 structure type.'"]
The crystal lattice of 2["] comprises centrosymmetric
~aFe6(OCH3),,(dbm),]+cations (Fig. I), as well as disordered
chloride anions, chloroform, and methanol molecules. The six
iron atoms are located at the vertices of an ahnost regular
hexagon, with Fe . . . Fe separations in the range 3.18-3.20 p\,
vertex angles of 1l9.5-120.5", and average deviations of
- 0.024 8, from the best least-squares plane. The diameter of the
ring. defined as the average distance between two opposing iron
atoms, is 6.39(2) A. Bis(methoxo) bridges connect adjacent iron
atoms; the remaining two sites of the distorted octahedral coordination sphere of each iron(rr1) center are occupied by a chebating
dibenzoylmethanido ligand. Adjacent Fe,O, planes through each
pair of methoxo ligands and their two bound iron atoms are
twisted with respect to each other and form dihedral angles of
120- 121 with the mean plane of the Fe, ring. As a consequence,
within each layer of six oxygen atoms contributed by the methoxo
bridges, one above and one below the plane through the iron(rrr)
centers, three oxygen atoms lie closer to the virtual C, symmetry
+
A n d r e a Caneschi, Andrea C o r n i a , Stephen J. Lippard *
Over the past ten years, several studies have been carried out
to investigate possible pathways for the hydrolytic aggregation
of iron(n1) in an aqueous environment.['] One strategy has been
to use suitably designed polydentate organic ligands to control
the chemical routes leading ultimately to the deposition of solids
containing a portion of the a-FeO(0H) (goethite) crystal lattice.
In this manner. a variety of polynuclear iron-oxo aggregates has
been isolated either from aqueous12*31 o r nonaqueousr4, solutions. In particular, new synthetic techniques have been developed that take advantage of hydrolytic polymerization processes involving iron(o)/iron(m) in nonaqueous solvents to build up
polyiron-oxo aggregates, which may serve as models for the
mineral core in ferritin."] Large polyiron complexes are also of
interest for obtaining nanometer-size magnetic particles.[61The
possible use of hydrolytic processes in the deposition of thin
layers of iron oxides['] makes them attractive entities for materials science as well.
Solution studies have provided evidence for the existence of a
cyclic hexanuclear iron(rI1) species, in which the metal ions are
connected by two hydroxo ligands, tentatively formulated as 1 .
Such a species may be responsible for the reversible gelation
[ ~ ~ , ( O ~ l ) , ~ ( s1.~ H
~ +r o)r~ =
, ]sorbirol
~'~
phenomena observed upon careful neutralization of concentrated alkaline aqueous solutions of iron(rrr) and sorbitol.['] We
report here on the preparation and characterization of the hexanuclear iron(1ir) compound 2. A solid-state X-ray diffraction
[NaFe,(OCH,),Z(dhi~~),lC1.
l Z C H , O H . C H C l , 2, H d h m = dihenzoylmethane
[*] Prol. S . J. Lippxrd
Department 01'Chemistry. Massachusetts Institute of Technology
Cambridge. M A 07139 (USA)
T e l e f k Int. code (617)258-8150
+
[**I
Dr. A. Caneschi
Dipartiinento d i Chimic,i. Universiti degli Studi di Firenze (Italy)
A. Cornra
Dipartimciito di Cliimica. UniversitB degli Studi di Modena (Italy)
This work w'is wpported by ii grant from the National Science Foundation.
A. Cnneschi acknowledges the Consiglio Nazionale della Ricerche Comitato
Nnrionale Scienre ('himiche for funding his stay a t MIT.
Fig. 1. ORTEP representation of the cation in 2 with atom labels. Hydrogen atoms
have been omitted for clarity. An inversion center relates primed atoms to unprimed
and angles
ones. Thermal ellipsoids enclose 50% probability. Relevant distances
["I: F e l - 0 1 2.022(3). F e l - 0 2 2.005(5), Fel-05' 2.019(3). Fel-06' 2.003(5). F e l - 0 7
1.983(3). F e l - 0 8 1.975(4), Fe2-01 2.029(5), Fe2-02 2.001(3). Fez-03 2.016(4).
Fe2-04 2.025(3), Fe2-09 1 .998(5), Fe2-010 1.977(3). Fe3-03 2.003(3), Fe3-04
2 027(4). Fe3-05 2.032(5). Fe3-06 2.007(3). Fe3-011 1.979(5), Fe3-012 1.996(4),
Fel-Fe2 3.184(1). Fel'-Fe3 3.197(1), Fe2-Fe3 3.201(1). Na-Ol 2.338(3), Na-04
2.374(4). Na-05 2.341(3); 0 1 - F e l - 0 2 75.5(2). 01-Fel-05' 94.4(1). 02-Fel-05'
93.1(2). 0 6 ' - F e l - 0 1 94.7(2). 06'-Fel-05' 75.1(2). 0 7 - F e l - 0 1 89.5(1). 07-FeI-02
99.8(2). 07-Fel-06' 92.3(2), OX-Fel-02 92.5(2), 08-Fel-05' 93.0(1). 08-Fel-06'
98.4(2). 0 8 - F e l - 0 7 85.9(1), 04-Fe2-03 74.9(1), 09-Fe2-04 89.2(2). 09-Fe2-03
99.6(2). 010-Fe2-03 91.6(1), 010-Fe2-09 86.9(2). 010-Fe2-02 99.7(1), 010-Fe20 1 92.5(7), 02-Fe2-09 92.5(2). 02-Fe2-04 94.8(1). 01-Fe2-01 75.5(2). 03-Fe201 92.7(2). 04-Fe2-01 94.3(1). 04-Fe3-03 75.1(1), 05-Fe3-03 95.4(2), 05-Fe30 4 95.0(2). 06-Fe3-04 92.8(1). 06-Fe3-05 74.7(2). 011-Fe3-03 101.3(2),
011-Fe3-04 92.6(2), 011-Fe3-06 89.7(2). 012-Fe3-03 89.9(1). 012-Fe3-05
90.1(2). 012-Fe3-06 102.6(1). 012-Fe3-01 I 86.6(2). Fel-Fe2-Fe3 119.51(3). Fe2Fe3-Fel' 119.90(3). FeY-Fel-FeZ 1?0.52(3). 04-Na-01' 101.8(1). 05-Na-01'
78.6(1), 05-Na-04 78.8(1), 0 1 - N a - 0 5 101.4(1). 01-Na-04 78.2(1). 0 5 - N a - 0 4
101.2(1).
[A]
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