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Synthesis and X-ray Structure of a Shape-Persistent Macrocyclic Amphiphile.

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6
5
Scheme I . a) BrCH,COOfBu. KOH. dioxane. 55 C, 2 h. 91 %; b) KOCMe,.
THF. H,O. 0 C. 7 min. 9 5 % ; c) H,, Pd!C. MeOHITHF, 20 C. 1.5 h. 9 6 %
(Z = beii7yloxycai-honyl)
Hgo%
HO
5
+
H2NOBn
6
+
5
I
0
0
8
9
Scheme 2. a ) CICOOfBu. NEt3. THF:'MeCN, 20 C. 12 h , Ac,O. Py. 87%: b)
AcOH X0 '!Io.
80 C . 1.5 h ; Ac,O. Py. 20 C. 18 h. 90%; c) H,, PdiC (10%). dioxanej
H,O. 20 C, 1.5 h. 9 5 % : d) CICOOiBu, NEt,. THFiMeCN. 20 'C. 30h. 8 4 % ; e)
NaOMe, dioxane:MeOH. 20 'C. 10 h. 85%; f )
AcOH XO%. XO C. 1.5 h. 0 . 3 ~
CDMT, N-inethylmorpholine. DMF, 50 C. 18h. Ac,O, Py 40%; g j 0 . 3 NaOMe.
~
dioxane'niethanol. 2 0 C . 2.5 h. 81 %.
[2] a) D. Rouzaud. P. Sinay. J. Chem. S,J<.C'/iwlf,<.<JnlnllUl19x3. 1 3
Giese, T. Witzel, At7,pr. C/iefn. 1986. 98. 459. . A t i , ~ y i i .C/ii~rilnr.
1986, 25, 4 5 0 : ~ )0. R. Martin. F. Xie. R. Kakarla. R. Benhaiiira. Sjnlrr( 1993.
165: d) B. Vauzeilles. D. Cravo. J.-M. Mallet. P Sina4:. d i d 1993. 522. e ) A .
Wei, Y. Kishi. J. Org. Chem. 1994. SY. 88: f) L. Lay. F Nicotra, C. PnngraLio,
L. Panza, G . Russo, J. Chew. So(.. Perkiff Trun.i. / 1994. 37 I . g ) H. Dietrich,
R. R. Schmidt. L i i ~ h i gAnn.
~ Chef??.1994.975; h) R. Ferritto. .1' Vogcl. 7i/ruhr,clrofi A.ywon. 1994. 5. 2077.
[3] T. Haneda. P. G. Goekjian. S. H. Kim, Y Kishi, J. Urg. C h ? n 1992. i 7 . 490.
[4] a) R. J. Ferrier. N Prasad, J. Chem. Soc. C 1969, 581. b) J. Jurczak, T Bauer,
S. Jarosz, Terruhedron L ~ i f 1984.
.
25. 4809; c ) B. Gieae. 1%. Ruckerr. K. S.
Groninper, R. Muhn. H. J. Lindner, Liehig.s Anti. C/wni. 1988. Y97; d ) R W.
Armstrong. B. R. Teegarden, J. Org. Clieti.1. 1992. 57. 915: L') H. P. Wessel. G.
Englert. J C'urholijdr. Chetn. 1995. 14, 179.
IS] a) B. Aebischer. J. H. Bieri. R. Prewo. A. Vasella, Heir. C h m .4cfu 1982, 6.5,
2251; b) J. M. Beau, P. Sinay. Tefrul7edron Lrrr. 1985. 26. 61x9, 6193: c) S. J.
Danisheliky. W. H . Pearson, F. D. Harvey. C. J. Maring. J. P. Springer, J An,.
C ' l l ~ t i i . So<,. 1985. 107, 1256; d) 1. M. Dawson. T. Johnwn. R M Paton,
R. A. C. Rennie. J C/ion. Soc. C h i r . Connnuri. 1988. 133Y. e ) W. B. Motherwell, B. K. Ross, M. J. Tozer. Siwlrcr 1989. 68: f ) A. de Rdadt, A. € . Stiitz.
C'urholiwlr. Res. 1991. 220, 101; g) R . R. Schmidt. A. Beyei-hach. L i r h f p Anti.
Clwtn. 1992. 983: h) H. M Binch. A. M. Griffin. S. Schmidetzki. M. V. J.
Ramsey. T. Gallagher. F. W. Lichtenthaler. J. C h m . S o < C/icvn. Conitnufr.
1995. 967.
[6] a) S . Jarosz. D. Mootoo, B. Fraser-Reid, Crrrboli~dr.Rr.$. 1986. 147. 59; b)
S. M. Daly. R. W. Armstrong, Tefruhedron Lett. 1989. 30, 57 13. c ) J. Alzeer. A.
Vasella, Heli.. Clnni. A f u 1995. 78, 177.
[7] Muramic acid ( = (R)-2-amino-3-O-(l-carboxyethylj-2-deox~-u-glucose) is
found i n the bacterial cell wall.
18) E. Graf von Roedern. H. Kessler. Angcw Chem. 1994, 106. 684: A n g e ~Chrm.
I n r . Ed. Engl. 1994, 33. 687.
[9] A similar approach has been mentioned in the context of nucleoside mimetics
synthesis. K C. Nicolaou. H. Florke. M. G . Egan, T. Barth, V. A. Estevez.
Ti,frukei/ron Lrft. 1995. 36, 1775.
[lo] a ) R. Gigg. P. M. Carroll. Nafrirr 1961, 191. 495; b) T. Miyazaki. Y. Matsushima. Bull. Chem. So(. Jpn. 1968. 41. 2723.
[I 11 Dissociation constants ofcarbohydrate-protein complexes itre generally in the
upper micromolar range. as hydrogen bonding dominates, and strong hydrophobic interactions are missing: cf. C.-H. Wong. R. L. Halcomb, Y Ichikawa,
T. Kajimoto, Afigeu.Chcvn. 1995, 1067. 569; A N ~ L Clicni.
W
/ f i r . Ed. Etigl. 1995.
34. 521.
[I21 P. C . Wyss. J. Kiss, Heli,. Chin?. Acra 1979, 58. 1833.
[13] W. Meyer zu Reckendorf. B. Radatus, E. Bischof. R. Weher. Chrm. Ber. 1974,
107. 869. We have prepared 7 from the N-Z-protected precursor (H. P. Wessel,
J Curholfjrlr. C/irm. 1988. 7 . 263).
[I41 Z. J. Kaminski. Srnrhesis 1987, 419.
[l 51 Physical data of 10: [TI;" = 125 (c = 0.2 in methanol): MS (laser desorption)
tn;: 1353 (90%. [iM+Na]+); ' H N M R (400MHz. [DJDMSO, TMS): 6
= 8.20 (d. 1H. J = 8.7 Hz, NH). 8.15 (d, l H , J = 8.6 Hz. NH), 7.94 (d, 1H.
J = 8.6 Hz, NH). 7.16 (br. d. l H , J-7.2 Hr. NH).
+
This block synthesis of tetramer lo[''' demonstrates the comparatively efficient access to a novel class of oligosaccharide
mimetics comprising peptide- saccharide hybrids.
Expwimentul ProcPdure
To a wspension o f 9 (771 mg) in D M F (3 m L ) , activated with C D M T (I76 mg) in
the presence of .V-methylmorpholine (121 pL) for 1.5 h, is added a solution of 8
(789 mg) i n DM t. ( 7 mL). After stirring for I X h at 50 C the reaction mixture is
concentrated and acetylated filth Ac,Oipyridine. The solvent is removed. and the
residue chromatographed over silica gel (eluent: ethyl acetatejhexane). Pure
product fractions (684 mg. 40%) are deacetylated in a mixture of methanol (6 mL)
and dioxane (4 m L ) containing 0 . 3 ~
sodium methanolate solution in methanol
( I mL). Neutrali~ationwith ion exchange resin (Amberlite IRl2O H + j and chromatography ovei- silica gel (ethyl acetateimethanoljwater X5!10:5) affords pure
amorphous 10 ( X I
Received: July 18, 1995 [Z822SIE]
German version: Afi,qew. Chotn. 1995, 107, 2920-2921
Keywords: carbohydrate amino acids . compound libraries
normuramic acid . oligosaccharide mimetics
[I]
; I ) E. Truschcit. W. Frommer. B. Junge. L. Miiller. D. D. Schmidt, W. Wingen.
1981, 93. 73X: A f i g e s . C h m h i . Ed. Enpl. 1981. 20, 744;
der. . 4 f i , ~ yC/rtwi.
b) L. E. Fellow, Chcvn. Brit. 1987. 23. 847: c) N. M Carpenter. G. W. Fleet.
I . Cenci di Bello, B. Winchester, L. E. Fellows, R. J. Nash. Tetrahedron Leff.
1989. 30, 7261, d ) M. L. Sinott, Chetn. Rcr. 1990. YO, 1171; e j G. Legler. Ad,,.
('orhohvlr. Chon. Biorhcni. 1990. 48. 319; f ) H. Paulsen. M. Matrke, B. Orthen. R Nuck. W. Reutter. Liebigs Atin. C%etii.1990. 953, g) G. Papandreou.
M . K . Tong. B. Gancm. J. Atn. Clfeni. So(.. 1993, 115, 11682.
Synthesis and X-ray Structure of a
Shape-Persistent Macrocyclic Amphiphile
Sigurd Hoger* and Volker Enkelmann
The study of shape-persistent, structurally defiQed macrocycles capable of binding guest molecules within their cavities
has attracted a great deal of interest during the last few years."]
For example, naturally occuring cyclodextrins and their derivatives are able to bind organic substrates through hydrophobic
interactions and are also capable of catalyzing chemical reactions of certain substrates.['] Host molecules having a hydrophobic exterior and a hydrophilic interior have also been synthesized and studied in detail as models for enzymes.[31A great
[*] Dr. S. Hoger. Dr. V. Enkelmann
Max-Planck-Institut fur Polymerforschung
Ackermannweg 10. D-55128 Mainz (Germany)
Telefax: Int. code +(6131)379100
deal of effort has been directed recently towards the preparation
of macrocycles with cavities having nanometer dimension^.^^] I n
addition to their ability to complex large guest molecules, large
macrocycles may play an important role in the design of organic
zeoh tes.I51
Here we describe the synthesis and X-ray structure of I , an
interesting example of a macrocyclic amphiphile, which has a
shape-persistent molecular backbone and hydrophilic and hy-
A
selective coupling of a terminal alkyne with an aryl iodide in the
presence of an aryl bromide['] and the site-selective removal of
the TMS group in the presence of the triisopropylsilyl (TIPS)
group.18J
Phenol 3I9I was first converted into the tetrahydro-(2H)pyranyl (THP) ether 4. which was coupled successively in a
one-pot Pd-catalyzed reaction with 1 .I equivalents of TIPSacetylene for four days at 55°C and then two equivalents of
TMS-acetylene for an additional four days at the same temperature to yield 5. Selective removal of the TMS group was accomplished by stirring a solution of 5 in MeOH/THF ( l / l ) in the
presence of a small amount of 1 N aqueous NaOH. This method
can be used to prepare 2 in 20-30g quantities.
Palladium-catalyzed coupling of 2 with 3,5-diiodotoluene,
followed by removal of the TIPS protecting group, yielded tetrayne 6 (Scheme 2). Coupling of 6 with 3-bromo-5-iodotoluene
TIPS
&-=
h
a), b)
\ /
OPr
2
/
/
4THPO
6
OTHP
*
Y
1
drophobic substituents. Our research has been directed towards
the synthesis of molecules of defined shape, size, and functionality,16]in which the polarity of the interior depends on the polarity of the surrounding solvent and/or confined guest molecules.
The preparation of large amounts of the macrocycle 1 described here depended on an efficient route to monoprotected
diynes of type 2. Preliminary attempts to obtain the trimethylsilyl (TMS) analogue of 2, starting from the corresponding diyne,
by deprotonation with EtMgBr and trapping of the acetylide
with TMSCl led to a statistical mixture of starting material and
mono- and bis-TMS-protected compounds. We were not able to
separate larger amounts of these materials because of their similar R,values. Therefore, it was necessary to find an alternative
way to 2 (Scheme 1 ) . The key steps in this approach are the
HO
I
Br
7
I
el
8
THPO
\
AD.
0
THPO
Scheme 2. a) 3,s-diiodotoluene. 4 m o l % [PdCI,(PPh,),]. 2 mol% CuI, piperidine,
55 C. 14 h: b) Bu,NF, THF, RT, 2 h (88%); c) 3-bromo-5-iodotoluene, 4 mol%
[PdCI,(PPh,),]. 2 mol% Cul, piperidine, 55°C. 14 h (84%); d) TMS-acetylene,
4 mol% [PdCI,(PPh,),], 2 mol YOCuI. piperidine, 5 5 ' C, 4 d ; e) I N NaOH, MeOH/
T H F ( I l l ) , RT. 3 h (70%); f ) CuCI!CuCI,. pyndine. RT (60-65%). g) CH,CI,/
MeOH ( Z I I ) , H i , 1 d (quantitative).
THPO
OPr
OPr
5
2
Scheme 1. a) 3.4-Dihydro-2H-pyran, CH,CI,. H', 0 C 1 h. room temperature
(RT), 1 h (90%): b) 1. 1.1 equiv TIPS-acetylene. 4 mol% [PdCI,(PPh,),]. 2 mol%
Cul. piperidine. 55 'C, 4 d , 2. Zequiv TMS-acetylene. 4 d (82%); c) 1 N NaOH.
MeOH'THF ( l / l ) , RT. 30 inin (96%).
gave the dibromide 7. The much higher reactivity of aryl iodides
over aryl bromides prevents, in this case, formation of oligomeric side products. Coupling of 7 with TMS-acetylene, followed by
removal of the TMS group, generated the bisacetylene 8. The
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THP-protectcd macrocycle 9 was obtained by a modified
Eglington --Glaser coupling['01 of 8 under high-dilution conditions." ' I The crude product was recrystallized from CH,CI, to
give 9 in 45% yield as slightly yellow crystals, which were unstable when removed from the mother liquor." Acid-catalyzed
deprotection of 9 produced compound I in nearly quantitative
yield." J1 All synthetic procedures outlined can be scaled up such
that this new ainphiphile is available in gram quantities.
In its synthesis macrocycle 1 is formed as a slightly yellow
precipitate. which darkens in the presence of air but is stable
under an inert atmosphere. The compound is marginally soluble
in most organic solvents but readily soluble in THF, pyridine,
pyridine water mixtures (with only limited amounts of water)
at room temperature and in tetrachloroethane at elevated temperatures. Single crystals suitable for X-ray analysis were obtained by recrystallization from pyridine. Like crystals of 9.
these a l s o decompose, although more slowly, when removed
from the mother liquor due to loss of solvent. A suitable crystal
was therefore embedded in Inertoil and the data collection was
performed a t 165 K.[I4]Under these conditions the crystal was
stable for several weeks and a good-quality X-ray structure of 1
was obtained (Figs. 1 and 2). The R-value after anisotropic
refinement was 0.063.["]
0
Fig. 2. Crystal structure of 1; view perpendicular to the stacking axis
C76
C24
31
cs9
C?
c1
diyne bridge is 6.7". It is interesting to note that the deformation
of the macrocycle is not symmetrical. The section ring(C3.. .S)/
ring(C12.. .17)/ring(C23.. 2 8 ) is nearly linear. whereas the rest
(C30.. .47) shows a strong bending (C27-C30-C31 173.3(10)".
C30-C31-C32 175.4(10)' deviate significantly from linearity).
As a result of this torsion and deformation the arene units
C23.. . C28 and C23'. . . C28' are separated by a vertical distance
of 3.4 A within the macrocycle. ' H NMR data a t room temperature and above show that in solution the macrocycle is either
symmetric or, more probable, in several. rapidly interconverting
conformations. It is still unclear whether the propyloxy groups,
which are coplanar with their aromatic rings in the crystal structure, prefer to be on the inside of the ring in solution.
Compound 1 is the first example of an amphiphilic shapepersistent macrocycle, in which free rotation about diphenyl
acetylene units in the molecule should result in either a more
hydrophilic or a more hydrophobic interior. Current studies of
I , derivatives of 1, and amphiphilic macrocycles of other size
and structure are addressing this issue.
Received: July 21. 1995 [ZX231 IE]
German version. A n , q w . <'hem. 1995, 107. 2917-2919
Y
Fig. 1. Crkstiil 'itructtire of I ; top view of the macrocycle. For clarity only the
hydrogen bonded pqridtne molecules are shown.
The nonbonding distances of C51GC51' (2.400(1) nm) and
C28-C28' (2.009(1) nm) give an idea of the size of the interior
of the macrocycle. In its crystal structure 1 has a center of
symmetry. For each macrocycle eight molecules of pyridine
were localized. Four of them form hydrogen bonds (distances:
0 3 ' . . N 2 : 2.85 A. 01 . . . N1: 2.72 A) with the phenolic OH
groups on the outside of the ring. The remaining pyridines pack
within the crystal lattice without specific interactions with the
macrocycle. One of them is localized at the center of symmetry,
which leads to orientational disorder. In this case the N and one
C atom occupy the same position with a probability of 50%.
The macrocycle itself is not planar; the torsion angle around the
Keywords: amphiphiles . macrocycles
supramolecular chemistry
nanostructures
[l] Recent examples: a) H. L. Anderson. A. Bashall. K. Hendrick. M. McPartlin.
J. K . M. Sanders, Angel!. Cheni. 1994. 106. 445: A n g o r (%mi. Inr. Ed. Erlgl.
1994, 33. 429. and references therein; h) M. R. Ghadiri. K . Kohaydshi. J. R.
Granja. R. K. Chadha. D. E. McRee. ihid. 1995. 107. 70 and 1995. 34. 93;
c ) D. J. Cram. Nulure 1992. 356, 29; d) J. M. Lehn. S w m ? 1993. 260. 1762:
e) F. Dtederich. Narrrrr 1994, 369, 199.
[2] a) G . Wenz. Angeiv. Chew. 1994, 106, 851 : Angcm Cherir I n / . E d E i i ~ l 1994,
.
33. 803: h) W. Saenger. ihrd. 1980, 92. 343 and 1980. I Y . 344.
[3] a) Y H. Kim. 0. W Wehster. J. A m Chem. Soc. 1990. 1/2. 4592, b) E
Diedertch, K. Dick, D. Griehel. ihid. 1986, 108, 2273. ant1 references therein.
[4] a ) J. S Moore. J. Zhang. Angru.. Chem. 1992. 104. 873: Aii,yor. Chern. /I?/ Ed.
En$ 1992, 31. 922; h) P. Timmermann, W Verhoom. F (1. J. M. van Veggel,
W. P. van Hoorn, D. N . Reinhoudt, ihiri. 1994. 106. 1313 :ind 1994. 33. 1292.
c) A M. Boldi, E Diederich. i h d . 1994. 106, 482 and 1994. 33. 486. d ) A. de
Meijere, S. Kozhushhov. C. Puls, T. Haumann, R. Boese. M . J. Cooney. L. T.
Scott. ihid. 1994. 106. 934 and 1994, 33. 869, A. de Meiicre. S. Korhushhov,
T. Haumann. R. Boese. C. Puls, M. J. Cooney. L . T, Scott. Chcm Eur. J 1995.
1. 124.
[5] Z . Wu. J. S . Moore, P o / m i . P r e p . ( A n t Cheni. So?. Die !'~~/j~i?i.
<'hwz.) 1993,
34(1). 122.
[6] M. Antonietti. S . Heinz. rVur~hr.Chwn. Tidni. Loh. 1992. 40. 310.
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[7] a) K . Sonogasliira, Y. Tohdzr. N . Hagihara. W r u h d r o n Letr. 1975.4467; h) Y.
Tohda, K. Sonogzishifi~N. Hagihzira. Svnthcsrs 1977, 777.
181 P Firton. A. E. Rick. J. Org~rnon7~~r
C/i~n.nl.
1971. 93. 254.
(91 S. Hoger, unpublished.
[lo] D. O'Krongly. S . R Denmade. M. Y. Chiang. R. Breslow. .
I
Am. Ckem. Sac.
1985, 107, 5544.
[ l l ] The cyclization was performed by the dropwise addition of a pyridine solution
of 8 with a syringe pump over 96 hours to a slurry of CuCl and CuCI, in
pyridine at room temperature. After workup no signals attributable to alkyne
protons were found in the ' H N M R spectrum. The yield of 9 by determined by
HPLC was 60 - 6 5 % ; no starting material was evident.
[I21 Macrocycles with analogous behavior have been described by others, e.g. a) J.
S. Moore. Po/vm. P r e p . ( A m . Cizem. Sac. Dro. Polw?. Chem.), 1993. 34(1).
170; b) A. de Meijere, F. Jaekel. A. Simon. H. Borrmann, J. Kohler, D. Johnels.
L. T, Scott, J. A m . Chf'n?. SOC. 1991. 113. 3935.
[I31 Selected spectroscopic data of I : ' H N M R (300 MHz. [DJpyridine. 50' C):
6 =1.11 (t, J =7.4 Hz. 12H). 1.87 (in. 8 H ) . 2.14 (s, 6 H ) , 2.15 (s. 12H). 4.09
(m.XH).7.46(~.4H).
(t, J = 6.SHz,8H).4.60(br.s.OH),7.29(m,4H),7.31
7.69 (s. 4H). 7.80 (s. 2 H ) . Characteristic "C N M R signals (75MHz.
[DJpyridine. 5 0 ' C ) : 6 =74.8, 81.9. 87.4. 88.7, 94.1, 94.6.
triclinic, space group
[14] Crystal structure data for 1: C,,,H,,0;8C5H,N.
pi. u = 12.297(2). h = 13.963(s). = 1 7 . 4 ~ 6 ) A ;2 = 85.642(31). [j =
80.644(22), 7 = 68.344(23)'. V = 2887 A'. Z = 2 , pcrlrd
= 1.184 gcm-',
[I = 5.435 cm-', T = 165 K. A crystal with the dimensions 0.4 x 0.2 x 0.1 mm
was placed in Inertoil (Type RS 3000. Riedel de Haen). Nonius CAD4 diffractometer. graphite-monochromated Cu,, radiation. i.
= 1.5418 8, Om,, = 6 2 .
0120 scans. 9473 independent reflections, of which 4280 were observed
( I > 3u(I)).empirical absorption correction. The structure was solved by direct
methods. Refinement was done by full-matrix least squares analysis with anisotropic temperature factors for C. H. and 0. Hydrogen atoms were refined
with fixed isotropic temperature factors in the riding mode. The refinement
converged at R = 0.063 and R, = 0.067. Difference Fourier analysis showed
no peaks beyond +0.35 or -0.27 e k 3 . Further details on the crystal structure investigation may be obtained from the Director of the Cambridge Crystallographic Data Centre, 12 Union Road, GB-Cambridge CB2 I E Z ( U K ) . on
quoting the full journal citation.
[I 51 X-ray data of other shape-persistent macrocycles having cavities of nanometer
dimensions: a) D. Venkataraman. S. Lee, J. Zhang. J. S. Moore, Nutrrre 1994.
371. 591 ; b) H. L. Anderson, A. Bashall. K . Henrick. M. McPartlin. J. K . M.
,
I n / . Ed. Big/. 1992. 31.
Sanders. Afigeir. Chem. 1994. 106. 445; A n g ~ i r Chrnr.
429: c) S . Anderson, H. L. Anderson, A. Bashall. M. McPartlin. J. K. M.
Sanders. ibrd. 1995. 107, 1196 and 1995, 34. 1096.
Our group has isolated cyclic hexairon(ii1) complexes of general formula 1 (M = Li, Na; H L = Hdbm, Hpmdbrn[5]).['~41
These compounds are reliable structural models of OH-bridged
polynuclear complexes believed to exist in aqueous solution. In
the course of this study Fe, ,[41 Fe,,16] and Fe4[41complexes were
also isolated. Though these complexes contain CH,O and L
ligands, they are structurally reminiscent of the infinite lattices
of iron oxides and
Here we report the synthesis,
crystal structure, and magnetic properties of the novel decaironfm) cluster 2..-cCHCI,, which extends the previously
[Fen,O,(OCH,),,(~~~),]~.UCHCI,
2 . Y CHCI,
mentioned series of polynuclear compounds and has an inorganic core arising from hydrolysis.
The crystal lattice['] of 2.xCHC1, contains decairon clusters
2 and highly disordered chloroform molecules. The structure of
2 is shown in Figure 1. A view of the iron-oxygen core is pre-
Structure and Magnetic Properties of a
Decanuclear Oxoiron(m) Cluster :
A Further Step to Understanding Iron
Aggregation Processes**
Andrea Caneschi, Andrea Cornia, Antonio C . Fabretti,
and Dante Gatteschi*
The hydrolysis of iron salts can be controlled by organic
ligands so as to yield soluble molecular aggregates with nanometer dimensions, which can often be isolated in crystalline form
and structurally characterized.['
Though some work has
been carried out directly in aqueous environments, the use of
nonaqueous media with a low water content has led to the
synthesis of an unexpected variety of polynuclear clusters.
['I
[**I
Prof. D. Gatteschi. Dr. A. Caneschi
Dipartimento di Chimica. Universiti degli Studi di Firenze
1-50144 Florence (Italy)
Telefax: Int. code +(55)354845
e-mail gattesch(it chimatl .chiml .unifi.it
Dr. A. Cornia, Prof. A. C. Fabretti
Dipartimento di Chimica, Universitd degli Studi di Modena (Italy)
This work was supported by the Italian Minister0 dell'llniversiti e della Ricerca Scientifica e Tecnologica. The authors acknowledge the Centro Interdipartimentale di Calcolo Automatic0 e Informatica Applicata of Modena University
for comcmter facilities.
27 16
*PVCH
Verlugsgesellschufr mhH. D-69451 Weiniieim, 1995
Fig. 1 . Structure of 2 (ORTEP representation with atom labels). Hydrogen atoms
have been omitted for clarity. An inversion center relates the primed atoms to the
unprimed ones. Thermal ellipsoids for iron atoms enclose 35 % probability. All the
remaining atoms are represented by spheres of arbitrary radius. Relevant distances
[Aland angles [ 1: 01-Fel 2.07(3), 02-Fel 2.06(3). 07-Fel 2.00(3),08-Fel 2.05(2),
015-Fel 2.07(3). 012'-Fel 1.97(3). 03-Fe2 1.9X(3). 04-Fe2 2.07(2). 08-Fe2
2.00(3). 09-Fe2 2.15(2), 010-Fe2 2.02(3). 015-Fe2 1.96(2), 05-Fe3 2.00(2), 0 6 Fe3 2.00(3). 09-Fe3 2.15(3). 010-Fe3 1.99(3), 011-Fe3 2.00(3). 016-Fe3 1.89(2),
07-Fe4 1.94(3), 09-Fe4 2.17(2), 014-Fe4 1.98(2). 015-Fe4 2.04(2), 016-Fe4
2.09(3). 016'-Fe(4) 2.00(3). 016-Fe5 2.20(3). 011-Fe5 1.97(2), 012-Fe(5) 2.05(3),
013-Fe5 1.90(3), 014-Fe5 2.03(3). 015'-Fe5 2.04(2), Fe2-015-Fel 99(1), Fe2-015Fe5' 148(1), Fe4-015-Fe5' 99(1), Fel-015-Fe5' 100(1), Fe4-015-Fel 98(1), Fe4015-Fe2 103.7(9). Fe4-016-Fe3 105( 1). Fe4-016-Fe3 155(2). Fe4-016-Fe4 94( 1).
Fe4-016-Fe5 95(1). Fe3-016-Fe5 100(I). Fe4-016-Fe5 96(1), 012'-Fel-08 152(1).
016-Fe4-09 157(1).
sented in Figure 2. Cluster 2 can be formally broken down into
two pentanuclear subunits related by an inversion center, which
are assigned primed and unprimed atom labels in Figures 1 and
2. The iron(m) ions in each subunit are found to lie on a plane
(max. deviation 0.08 A). The intralayer Fe-Fe separations are
0570-0~33/95;34~3-,7716
$ 10.00 i
.2S/O
Angrw. CIimt. Inr. Ed. Engl. 1995, 34, No. 23/24
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