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Complexes with Sb2 and cyclo-Sb3 Ligands The Tetrahedranes [{C5H5(CO)2Mo}2Sb2] [C5H5(CO)2MoSb3] and [C5Me5(CO)2MoSb3].

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severe structural reorganization: The perpendicular benzoid
system is transformed into a planar quinoid structure (Figure 2).
Received: May 14,1997
Revised version: August 14, 1997 [Z 10439IEl
German version: Angew. Chem. 1997,109,2926-2929
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Keywords: arenes cyclic voltammetry
radical ions stilbenes
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- electron transfer -
[I] J:M. Lehn. Supramolecular Chemrstry, VCH, Weinheim 1995; H. Meier,
Angew. Chem. 1992, 104, 1425; Angew. Chem. Int. Ed. Engl. 1992,31, 199.
[2] A. Knorr, J. Daub, Angew. Chem. 1995, 107, 2925; Angew. Chem. Int. Ed.
Engl. 1995, 34, 2664; J. Daub, M. Beck, A. Knorr, H. Spreitzer, Pure Appl.
Chem. 1996.68.1399; K. Kelnhofer, A. Knorr, J. Daub, Y.-H. Tak, H. Bassler,
Acru Polym. 1997, 48, 188.
[3] A. Knorr. Dissertation, Universitat Regensburg, 1995; F. Effenberger, C.-P.
Niesert. Synthesis 1992. 1137; G. Bartocci, U. Mazzucato, A. Spalletti, G.
Orlandi. G. Poggi, J. Chem Soc. Furaday Trans. 1992, 3139; T. Arai, T.
Karatsu, H. Misawa, Y. Kuriyama, H. Okamoto, T. Hiresaki, H. Furuuchi, H.
Zeng. H. Sakuragi. K. Tokumaru, Pure Appl. Chem. 1988.60.989.
141 1: M.p. 281.5-282.5-C. red needles, yield 27%, purification by column
chromatography on SiO, with CH,Cl,; 2: m.p. 208-209"C. red crystals, yield
8 0 % , purification by recrystallization from CH,Cl,/hexanes; 3: m.p. 322 'C
(decoma).
. _microcrvstalline orange solid, yield 28 %, no purification necessary, filtration from the mother liquor; 4: m.p. 195°C yellow needles, yield
100%. purification by column chromatography on SiO, with CH,Cl,/hexanes
(lil) and recystallization from CH,Cl,/hexanes; 5 : m.p. 3 1 7 - 3 1 9 T yellow
microcrystalline solid, yield 62 %,purification by column chromatography on
S O z with CH&l,/hexanes (lil) and recystallization from CHCI?; 6: m.p.
235 'C (decomp), dark red solid, yield 67%, purification by column
Chromatography on SiO, with CH,Cl,/hexanes (1/1) and recrystallization
from CHzCl,/hexanes.
a) AMI: M. J. S. Dewar, E. G. Zoebisch, E. F. Healy, J. J. P. Stewart, J. Am.
Chem. Soc. 1985. 107,3902; b) PM3: J. J. P. Stewart, J. Cornput. Chem. 1989,
10, 209: c) G. Rauhut, A. Alex, J. Chandrasekhar, T. Steinke, T. Clark,
VAMP5.01, Oxford Molecular Ltd., Oxford, 1993. d) The geometries of
closed-shell species were optimized using the RHF formalism, and those of
open-shell species were treated with the AUHF formalism. All obtained
structures were characterized as stationary points on the energy surface by
vibrational analysis.
The calculations of the neutral species showed that rotation about bond d l
leads to two transition states with dihedral anglesa of lo" and 90": 2 (10"):
8.80 (AMI), 4.20 kcalmol-' (PM3); 3 (10"): 8.53 (AMl), 4.46 kcalmol-l
(PM3); 2: (YO-): 0.34 (AMl), 0.05 kcalmol-' (PM3); 3 (90"): 0.25 (AMl),
0.03 kcalmol ' (PM3). Activation enthalpies of 1.63 to 1.26 kcalmol-' were
found for rotation about bond d3 depending on the model system and the
hamiltonian used. An analagous calculation for the correponding dication of
2 and dianion of 3 showed that rotation about bonds dl, d2, and d3 have
activation barriers between 21.18 and 26.25 kcalmol-', again depending on
the compound and the semiempirical method applied. It is remarkable that
rotation about bond d2 (a formal single bond) leads to such high energy
barriers. Furthermore. according to the semiempirical calculations the s-cis
conformation of these doubly charged species represents a transition state
and not a minimum on the energy surface of the rotation process (all
transition states were characterized by vibrational analysis).
H. Spreitzer. M. Scholz, G. Gescheidt, J. Daub, Liebigs Ann. 1996, 2069.
For the limited-CI calculation the four highest occupied and four lowest
unoccupied orbitals using only single and pairwise double excitation microstates were considered. Implementation of a perpendicular geometry for Z2+
and 3' in the calculation of the UV transitions yields numbers that
significantly deviate from the experimental findings. For computational
details. see ref. [Sc]
Complexes with Sb2and cyclu-Sb, Ligands:
The Tetrahedranes [{C5H5(C0)2Mo}2Sb2],
[CSHs(C0)2MoSb3],and
[CsMes(CO)2MoSb3]**
Hans Joachim Breunig,* Roland Rosler, and Enno
Lork
Dedicated to Professor Ionel Haiduc
on the occasion of his 60th birthday
Although complexes with organosubstituent-free cyclo-P,
or cyclo-As, ligands ( n = 3 - 6) have been investigated intensively,[']analogous compounds with cyclo-Sb, ligands have
not yet been described. Known complexes contain Sb,:'] Sb2,['1
Sb$-,I31 Sb:-f41 or organoantimony rings15] as ligands. An
interesting example of an Sbz complex is the tetrahedrane
derivative 1J21described by Rheingold, which can be considered an analogue of Sb,. We report here on a favorable
synthesis of 1 and on the preparation and the structure of 2
and 3, the first complexes with cyclo-Sb, ligands.
Compounds 1 and 2 are formed by the reactionI61 of
(tBuSb)J71 with [(C,H,Mo(CO),},] in boiling toluene. Although the Sb:Mo molar ratio of approximately 3:l should
favor the formation of 2, the main product is 1. Complex 2
forms in 2.3 % yield as dark red, crystal needles with a metallic
luster. Solutions of 2 in toluene or benzene are yellow. The
crystals decompose at 110°C and turn black. The analogous
reaction of (t BuSb), with [{C5Me,Mo(CO),},] produced red
needles of 3 in 27% yield. All three compounds are airsensitive. The identity of the compounds was confirmed by
elemental analysis and by 'H NMR, IR and mass spectra. The
structures of 2 and 3 were determined by X-ray structure
1,2 Cp" = C5H5; 3 Cp" = CsMe5
1
2,3
analysis.[*] Complex 2 crystallizes with two independent
molecules in the asymmetric unit. Both molecules contain
slightly distorted tetraehedral MoSb, units in which the
antimony atoms form an almost equilateral triangle. The
average Sb-Sb bond length in 2 is 274.94(10)pm. This is
considerably shorter than the Sb-Sb single bond lengths in
MeC(CH,Sb), (280-282 pm),F91(tBuSb), (281.8(2) prn),[8b]or
Sb:- (287.6-290.6 pm)J31 but longer than Sb-Sb multiple
bond lengths (double bond in [{C,H,Mo(C0)z)2Sb,J
[*] Prof. Dr. H. J. Breunig, R. Rosler, Dr. E. Lork
Institut fur Anorganische und Physikalische Chemie (FB 02)
der Universitat
Postfach 330440, D-28334 Bremen (Germany)
Fax: Int. code+(421)218-4042
e-mail' breunig@chemie.uni-bremen.de
[**I This work was supported by the Deutsche Forschungsgemeinschaft. We
thank Prof. 0. Scherer and his group at the Universitat Kaiserslautern for
the support given to R.R. during during a research visit.
Angew. Chem. h i Ed. Engl. 199736, No 24
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267.8(1) pm,[2]triple bond in [Sb,(W(CO),),] 266.3(3) pm[lo1).
The average Mo-Sb bond length in 2 is 290.25(10) pm, which
is longer than those in 1 (276.2(1), 285.4(1) pm).Izl
The molecular structure of 3 is shown in Figure 1. The
distorted tetrahedral MoSb, unit resembles very closely the
associate through close intermolecular Sb ...Sb contacts to
form supramolecular units. In the case of 2 the relevant
intermolecular contact distances range from 383.8 - 427.1 pm,
within the van der Waals limit of 440pm. Similar short
Sb ...Sb contact distances are also found in thermochromic
organo distibanes Me,Sb, (368 pm)[”] and (Me,Si),Sb2
(399 pm),[121and the organo cyclostibanes (2,4,6-Me,C6H2Sb)4
(390 pm)[l3]and MeC(CH,Sb), (397-401 pm).I91The molecules
in 2 associate to form to corrugated bands, which overlap like
roofing tiles. The [CSH5M~(C0)2]
units lie above and below
the antimony layers. In the crystal of 3 the molecules are
associated through intermolecular Sb ... Sb interactions with
distances of 374.5 and 383.4pm. The number of contacts
between the molecules is smaller, because the pentamethylcyclopentadienyl groups shield the tetrahedrane molecules
more thoroughly.
Experimental Section
Sb(l1
Figure 1. Molecular structure of 3 in the crystal. Selected bond lengths [pm] and
mean angles [“I: Sb(1)-Sb(2) 276.82(8), Sb(1)-Sb(3) 274.25(10), Sb(2)-Sb(3)
273.97(9), Mo(1)-Sb(1) 285.12(8), Mo(1)-Sb(2) 286.00(9), Mo(l)-Sb(3)
292.52(9); Sb-Sb-Sb 60.00(2), Sb-Sb-Mo 61.47(2), Sb-Mo-Sb 56.06(2).
MoSb, unit in 2. The crystal packing of 2 and 3 is, however,
different (Figures2 and 3). In both cases the molecules
1and 2: (tBuSb), (2.00 g) and [(C,H,(CO),Mo),] (2.00 g) are stirred under reflux
in 70 mL toluene for about 6 h. The dark red solution is decanted, and the black
precipitate washed with 5 0 m L toluene. The solvent is removed from the
combined extracts under reduced pressure, and the residue washed with 2 x
80mL petroleum ether. The purple red powder that was not dissolved by
petroleum ether was taken up in toluene (20 mL), combined with A1,0, (10 g),
dried to a flowing powder under reduced pressure, and placed on a chromatography column (3 x 10 cm neutral AI,O, according to Brockmann, particle size
0.063-0.200 mm,degree of activity 11). Compound 2 is eluted as a yellow fraction
with petroleum ethedtoluene (1011) and crystallizes after concentration of the
solution. Yield 50mg (2.3%). ‘H NMR (360MHz, C,D,, 2 5 T) : 6=4.22 (s,
CsH,); IR (toluene): C = 1962,1910 cm-I (C=O):
MS (EI, 70 eV): d z : 584 (90)
[ M + ] , 556 (50) [M+-CO], 528 (100) [ M i -2COI. Thereafter a broad red
fraction is obtained with toluene giving crystals of 1 upon concentration. Yield
0.96g, 76%. The ‘H NMR, IR and MS data are in accordance with the
literature. [2]
3: The reaction of (tBuSb), (1.63 g) with [(C,Me,(CO),MoJ,] (0.85 g) and
subsequent work-up are performed analogously. However, the crude material is
not washed with petroleum ether. By successive chromatography with petroleum
ether, petroleum etherltoluene (12/1), petroleum etheritoluene (8/1), and
petroleum etherltoluene (2/1) four fractions are obtained. The first fraction
contains 65 mg (tBuSb),, the third (0.37 g [(C,Me,Mo(CO),J,]. Concentration of
the fourth fraction and cooling to - 20°C yields red needles of 3 (0.47 g, 27%).
m.p. 198-199°C (decomp.); ‘H NMR (360 MHz, C6Dn.25°C) 6 = 1.70 (s, CH,):
MS (EI, 70 eV): d z : 654 (40) [ M + ] ,
IR (toluene): 3= 1951, 1897 cm-l (C=O):
626 (20) [ M +- CO]. 596 (100) [ M +- ZCO].
Received: July 8,1997 [Z10651IE]
German version: Angew. Chem. 1997,109,2941-2942
Figure 2. Selected contacts between the molecules in the crystal of 2 with Sb-Sb
contact distances smaller than 440 pm.
-
Keywords: antimony molybdenum
elucidation
br
Figure 3. Side view of a layer of molecules in the crystal of 3.
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*
Sb ligands
*
structure
ill
J. Scherer, Angew.
.~0.
Chern. 1990,102, 11371155; Angew. Chem. Int. Ed. Engl. 1990,29,
1104-1122; M. Scheer, E. Herrmann, Z .
Chem. 1990, 30, 41-55: A.-J. DiMaio, A. L.
Rheingold, Chem. Rev. 1990,90,169- 190.
[2] J. R. Harper, A. L. Rheingold, J. Organometal.
Chem. 1990,390, C36.
[3] W. J. Evans, S. L. Gonzales, J. W. Ziller, J.
Chem. SOC.Chem. Commun. 1992,1138-1139.
[4] U. Bolle, W. Tremel, J. Chem. SOC. Chem.
Commun. 1994, 217-219: S . Charles, B. W.
Eichhorn, A. L. Rheingold, S. G. Bott, J. Am.
Chem. SOC.1994,116,8077-8086.
[5] J. Ellermann, A. Veit, J. Organomet. Chem.
1985,290,307-319: H. J. Breunig, J. Pawlik, Z .
Anorg. Allg. Chem. 1995,621, 817-822.
[6] J. Queisser, H. Oesen, D. Fenske, B. Lehari, Z.
Anorg. A&. Chem. 1994, 620, 1821- 1831; J.
Queisser, H. Oesen, D. Fenske, H. Schottmuller, ibid. 1996, 622, 1731-1739; 0.M. Kekia,
R.L. Jones, Jr., A. L. Rheingold, Urganomeratlics 1996. 15, 4104-4106.
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Angew. Chem. Int. Ed. Engl. 1997,36, NO. 24
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17) a) K. Issleib, B. Hamann, L. Schmidt, Z. Anorg. Allg Chem. 1%5,339,298303; b) 0.Mundt, G. Becker, H.J. Wessely, H. J. Breunig, K. Kischkel, ibid.
1982,486.70 - 89.
[S] X-ray crystal structure analyses: Siemens P4 four-circle diffractometer,
Mo,,, radiation, I = 71.073 pm, scan mode w21B, T = 173(2) K, absorption
correction DIFABS, structure solution: direct methods with SHELXS-86,
refinement program
refinement: full-matrix least-squares against
SHELXL-93. hydrogen atoms geometrically positioned and refined with a
riding model. 2: crystal dimensions 0.6 x 0.5 x 0.1 mm3, triclinic, space group
P i , a = 715.60(10), b = 1243.3(2). c = 1387.7(2) pm, a = 105.490(10), 0 =
96.330(10),
y = 104.329(10)',
V = 1.1321(3) nm',
Z=4,
pcalcd
=
3.416 Mgm-', Om,, =27.50', 10436 measured reflections, 5137 unique
(R,,, = 0,0752). absorption coefficient 8.130 mm- number of free parameters 237. final R value(l>2o1), R1=0.0600, wR2=0.1448. 3: crystal
dimensions 0.7 x 0.3 x 0.3 mm', orthorhombic, space group Pbca, a =
1256.00(10), h=906.80(10), c=2874.4(3) pm, V=3.2738(6) nm3, Z = 8 ,
pcalid
= 2.647 Mgm ?, B,,
= 27.48", 4137 measured reflections, 3142 unique
(R,,,,= 0.0306). absorption coefficient 5.638 mm-', number of free parameters 170, final R value ( I > 200, R1 = 0.0387, wR2 = 0.0757. The crystallographic data (excluding structural factors) for the structures reported in this
publication have been deposited as supplementary publication no. CCDC100534 at the Cambridge Crystallographic Data Centre. 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;email :deposit@chemcrys.cam.ac.uk).
[9] J. Ellermann. E. Kock. H. Burzlaff, Acta Cryst. Sect. C 1985,41,1437- 1439.
[lo] G. Huttner, U. Weber, B. Sigwarth, 0.Scheidsteger, Angew. Chem. 1982.94,
210-211; Angew. Chem. In!. Ed. Engl. 1982.21, 215-216; Angew. Chem.
Suppl. 1982.414-416.
1111 0.Mundt. H. Riffel, G. Becker, A. Simon, 2. Naturforsch. B 1984,39,317322; A. J. Ashe 111, E. G. Ludwig, J. Oleksyszyn, J. C. Huffman, Organornerallics 1984,3, 337-338.
I121 G. Becker. H. Freudenblum, C. Witthauer, Z. Anorg. Altg. Chem. 1982,492,
37-51.
[13] M. Ates. H. J. Breunig, S. Giilec, W. Offermann, K. Haberle, M. Drager,
Chem. Ber 1989,122,473-478.
a,
central core of these molecules relying on an intramolecular
Diels - Alder rea~tion.1~1
In preliminary studies designed to explore the feasibility of
a strategy towards the total synthesis of the CP molecules
involving a rhodium-catalyzed carbenoid generation and
intramolecular trapping, followed by a divinylcyclopropane
rearrangement141and a radical cyclization (Scheme 1) the core
',
3
divinylcyclopropane
[3,3]-sigmatropic
rearrangement
carbenoid
cyclopropanation
bTBS
OTBS
OPMB
OPMB
4
0
Scheme 1. Retrosynthetic analysis of the CP core model system 3
model system 3 was defined as a target. We wish to report here
the execution of this strategy, which culminated in the
construction of racemic 22 which has the opposite stereochemistry at the quaternary center.
A Novel Approach to the
CP-225,917 and CP-263,114 Core**
K. C . Nicolaou,* Maarten H. D. Postema,
Neil D. Miller, and Guang Yang
The naturally occurring substances CP-263,114
(1) and CP-225,917(2) possess intriguing molecular
architecture,['] important biological properties, and
As inhibitors
an interesting mechanism of
of squalene synthase and farnesyl transferase, these
substances are attractive from the pharmaceutical
point of view, particularly with regards to lowering
cholesterol levels and to treating cancer. Isolated
from an unidentified species of fungi, these compounds include within their structures a novel
bicyclo[4.3.l]dec-l(9),4-dien-lO-one framework onto which a variety of substituents are attached. We
have previously reported on an approach to the
[*I
[*"I
Prof. Dr. K. C. Nicolaou, Dr. M. H. D. Postema, Dr. N. D. Mlller,
Dr. G. Yang
Department of Chemistry and The Skaggs Institute for Chemical Biology
The Scripps Research Institute
10550 North Torrey Pines Road, La Jolla, CA 92037 (USA)
Fax: Int. code + (619)784-2469
and
Department of Chemistry and Biochemistry
University of California, San Diego
9500 Gilman Drive, La Jolla, CA 92093 (USA)
This work was financially supported by The Skaggs Institute for Chemical
Biology and the National Institutes of Health (USA). We thank Dr. Dee H.
Huang and Dr. Gary Siuzdak for help with NMR spectroscopy and mass
spectrometry. respectively.
Angew. Chem. Int. Ed. Engl. 1997,36, No. 24
.COOH
-COOH
1: CP-263,114
2: CP-225,917
0
3
NOE
22
The synthesis of the requisite ketocyclopropane 15 proceeded as summarized in Scheme 2. Thus, methyl vinyl ketone
(5) was treated with formaldehyde under Baylis - Hillman[sl
conditions to afford, after p-methyoxybenzyla tion,I61 compound 6 in 25 70overall yield. Formation of the enol triflate
from 6 (60 % yield), followed by palladium-catalyzed coupling
with Me,SnSnMe, resulted in the formation of vinyltin
compound 7 (73% yield). Metal exchange followed by
reaction with TBSO(CH,),CHO and silylation furnished
bis(sily1)ether 8 in 80 % overall yield. Sequential deprotection, Swern and NaC10,/NaH,P04/2-methyl-2-butene oxidations, followed by exposure of the resulting carboxylic acid to
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sb2, c5me5, cycle, 2mosb3, complexes, 2mo, sb3, 2sb2, tetrahedranes, ligand, c5h5
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