Helical sense bias induced by point chirality in cage compounds

Article abstract of DOI:10.1002/1521-3773(20020402)41:7<1205::AID-ANIE1205>3.0.CO;2-X

Highly efficient chirality transfer is employed in controlling the topological asymmetry of chiral cages with propeller-like shape and pseudo C₃ symmetry (see picture; R=H, Cl). The cages are formed when two tripodal units (a tribenzylamine and

Full text of DOI:10.1002/1521-3773(20020402)41:7<1205::AID-ANIE1205>3.0.CO;2-X

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Boussac, S. Un, T. Kargar-Grisel, G. Bouchoux, J. J. Girerd, Eur. J.
Inorg. Chem. 1999, 993 996; d) A. J. Simaan, S. Dˆpner, F. Banse, S.
Bourcier, G. Bouchoux, A. Boussac, P. Hildebrandt, J. J. Girerd, Eur.
J. Inorg. Chem. 2000, 1627 1633.
Helical Sense Bias Induced by Point Chirality in
Cage Compounds**
¬
Mateo AlajarÌn,* Carmen Lopez-Leonardo,
[4] a) M. Lubben, A. Meetsma, E. C. Wilkinson, B. Feringa, L. Que, Jr.,
Angew. Chem. 1995, 107, 1610 1612; Angew. Chem. Int. Ed. Engl.
1995, 34, 1512 1514; b) I. Bernal, I. M. Jensen, K. B. Jensen, C. J.
McKenzie, H. Toftlund, J. P. Tuchagues, J. Chem. Soc. Dalton Trans.
1995, 3667 3675; c) M. E. de Vries, R. M. La Crois, G. Roelfes, H.
Kooijman, A. L. Spek, R. Hage, B. L. Feringa, Chem. Commun. 1997,
1549 1550; d) C. Kim, K. Chen, J. Kim, L. Que, Jr., J. Am. Chem. Soc.
1997, 119, 5964 5965; e) G. Roelfes, M. Lubben, K. Chen, R. Y. N.
Ho, A. Meetsma, S. Genseberger, R. M. Hermant, R. Hage, S. K.
Mandal, V. G. Young, Jr., Y. Zang, H. Kooijman, A. L. Spek, L.
Que, Jr., B. L. Feringa, Inorg. Chem. 1999, 38, 1929 1936; f) R. Y. N.
Ho, G. Roelfes, B. L. Feringa, L. Que, Jr., J. Am. Chem. Soc. 1999, 121,
264 265.
¬
¬
Angel Vidal, Jose Berna, and Jonathan W. Steed*
¬
Dedicated to Professor Jose Elguero
At the molecular level, helical chirality[1] is usuallya
consequence of strong conformational preferences around
covalent bonds. This is the case in molecular propellers, chiral
molecules possessing two or more subunits which can be
considered as ™blades∫ (e.g., aryl or spirocyclic rings), which
radiate from an axis of rotation (propeller axis).[2] Triaryl-
methanes are the most extensivelystudied structures of this
class.[3] Bicyclic organic compounds of local C3 symmetry,
constructed bylinking two propeller tripodal units exhibit this
type of chirality. However, this propeller shape has been
observed onlyfor a limited number of such compounds in
solution.[4] We have reported the preparation of several types
of C3 or pseudo-C3 symmetric, chiral macrobicyclic triphos-
phazides (e.g. 1a, Scheme 1), which possess propeller-like
[5] a) Y. Zang, T. E. Elgren, Y. Dong, L. Que, Jr., J. Am. Chem. Soc. 1993,
¬
115, 811 813; b) S. Menage, E. C. Wilkinson, L. Que, Jr., M.
Fontecave, Angew. Chem. 1995, 107, 198 199; Angew. Chem. Int.
Ed. Engl. 1995, 34, 203 205; c) J. Kim, E. Larka, E. C. Wilkinson, L.
Que, Jr., Angew. Chem. 1995, 107, 2191 2194; Angew. Chem. Int. Ed.
Engl. 1995, 34, 2048 2051; d) Y. Zang, J. Kim, Y. Dong, E. C.
Wilkinson, E. H. Appelman, L. Que, Jr., J. Am. Chem. Soc. 1997, 119,
4197 4205; e) A. Wada, S. Ogo, Y. Watanabe, M. Mukai, T. Kitagawa,
K. Jitsukawa, H. Masuda, H. Einaga, Inorg. Chem. 1999, 38, 3592
3593; f) T. Ogihara, S. Hikichi, M. Akita, T. Uchida, T. Kitagawa, Y.
Moro-oka, Inorg. Chim. Acta 2000, 297, 162 170; g) N. Lehnert,
R. Y. N. Ho, L. Que, Jr., E. I. Solomon, J. Am. Chem. Soc. 2001, 123,
8271 8290.
[5]
topologyin solution and in the solid state.
R
[6] The resonance Raman spectra of the deep blue species in DMF at
À608C with 607 nm laser excitation showed an isotope sensitive band
R
R
R
R
R
at 877 cmÀ1 which was shifted to 831 cmÀ1 bythe use of H 18O2,
N
2
N
suggesting the presence of a peroxo species.
CDCl3
N
[7] A. Adam, M. Mehta, Angew. Chem. 1998, 110, 1457 1459; Angew.
Chem. Int. Ed. 1998, 37, 1387 1388.
[8] R. Ugo, F. Conti, S. Cenini, R. Mason, G. B. Robertson, J. Chem. Soc.
Chem. Commun. 1968, 1498 1499.
333 K, 24 h
N
N
N
N
N
N
N
N
P
- 3 N2
N
P
N
N
P
P
P
P
CH3
CH3
[9] a) S. Hikichi, M. Akita, Y. Moro-oka, Coord. Chem. Rev. 2000, 198,
61 87, and references therein; b) N. Kitajima, T. Katayama, K.
Fujisawa, Y. Iwata, Y. Moro-oka, J. Am. Chem. Soc. 1993, 115, 7872
7873; c) A. V. Asselt, B. D. Santarsiero, J. E. Bercaw, J. Am. Chem.
Soc. 1986, 108, 8291 8293; d) G. Ferguson, P. K. Monaghan, M.
Parvez, R. J. Puddephatt, Organometallics 1985, 4, 1669 1674.
[10] a) T. Ookubo, H. Sugimoto, T. Nagayama, H. Masuda, T. Sato, K.
Tanaka, Y. Maeda, H. Okawa, Y. Hayashi, A. Uehara, M. Suzuki, J.
Am. Chem. Soc. 1996, 118, 701 702; b) Y. Dong, S. Yan, V. G.
Young, Jr., L. Que, Jr., Angew. Chem. 1996, 108, 673 676; Angew.
Chem. Int. Ed. Engl. 1996, 35, 618 620; c) K. Kim, S. J. Lippard, J.
Am. Chem. Soc. 1996, 118, 4914 4915.
[11] a) W. Micklitz, S. G. Bott, J. G. Bentsen, S. J. Lippard, J. Am. Chem.
Soc. 1989, 111, 372 374; b) I. Shweky, L. E. Pence, G. C. Papaefthy-
miou, R. Sessoli, J. W. Yun, A. Bino, S. J. Lippard, J. Am. Chem. Soc.
1997, 119, 1037 1042.
[12] There is no band overlapping with the DMF band at 865 cmÀ1; this was
confirmed bythe measurement of spectra in [D 7]DMF (see in
Figure 3d, e, and f).
a
b
R = H
R = Br
1
2
Scheme 1. Synthesis of 2 bydinitrogen expulsion from 1.
Herein, we report that, when compound 1a was kept at
333 K in CDCl3 solution for 24 h, it cleanlyconverted into tri-
l5-phosphazene 2a in 75% yield, by triple expulsion of
molecular N2 (Scheme 1). The dinitrogen expulsion from
¬
¬
[*] Dr. M. AlajarÌn, Dr. C. Lopez-Leonardo, Dr. A. Vidal, J. Berna
¬
Departamento de QuÌmica Organica
Facultad de QuÌmica, Campus de Espinardo
Universidad de Murcia, 30100 Murcia (Spain)
Fax : (‡349)68-364149
[13] M. Aresta, I. Tommasi, E. Quaranta, C. Fragale, J. Mascetti, M.
Tranquille, F. Galan, M. Fouassier, Inorg. Chem. 1996, 35, 4254 4260.
[14] G. M. Sheldrick, SHELXS-86, A Program for Crystal Structure
Determination, Universityof Gˆttingen, Germany, 1986.
[15] teXsan: Crystal Structure Analysis Package, Molecular Structure
Corporation (1985 & 1992).
E-mail: alajarin@um.es
Dr. J. W. Steed
Department of Chemistry
King×s College London
Strand, London WC2R 2LS (UK)
Fax : (‡44)20-7848 2810
E-mail: jon.steed@kcl.ac.uk
¬
¬
[**] We thank the Direccion General de Investigacion-MCYT (Project
¬
¬
BQU2001-0010), Fundacion Seneca-CARM (Projects PB/2/FS/01 and
PI-1/00749/FS/01), and Acedesa (a division of Takasago) for financial
support. J.B. also thanks the MECD for a fellowship. J.W.S. thanks the
EPSRC and King×s College London for diffractometer funding.
Supporting information for this article is available on the WWW under
http://www.angewandte.com or from the author.
Angew. Chem. Int. Ed. 2002, 41, No. 7
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each PN3 unit can be understood as the second mechanistic
step of a Staudinger PIII imination reaction.[6]
The new cage compound 2a was fullycharacterized byits
analytical and spectroscopic data,[7] but we were unable to
obtain a crystalline sample suitable for molecular structure
determination byX-raycrsytallograph.y To overcome this
mation with time-averaged C3v symmetry. The calculated[10]
activation energyof this racemization process,
DG=ˆ
20.8 kcalmolÀ1, is notablyhigher than the values found in
other bicyclic molecular propellers[4b,d] and slightlyhigher
than those of some tricyclic [4.4.4]propellanes[11] and the
1-azonia[4.4.4]propellane cation.[12] When a similar high-
temperature NMR spectroscopyexperiment was carried out
with 2b in wet [D6]DMSO solution, the results were
comparable to those above, but surprisinglyno trace of
hydrolysis of the tri-l5-phosphazene was observed, which
reveals the chemical stabilityof compounds 2 to be in sharp
contrast with the hydrolytic sensitivity of most of the
l5 phosphazenes prepared to date.[13]
problem we prepared the new triphosphazide 1b, byour well-
[5b,c]
established methodology,
which was then heated in
solution (CDCl3) to yield the tri-l5-phosphazene 2b (74%).
Suitable crystals of 2b enabled analysis of the molecular
structure.[8] Two perspective views of the structure of 2b are
shown in Figure 1. The molecule is located on a non-
crystallographic threefold axis passing through the two
bridgehead atoms of the bicyclic cage, and its propeller-
To our knowledge, compounds 2 are the first examples of
bicyclic tri-l5-phosphazenes, a subclass of the rare species
bearing intracyclic phosphazene units,[14] and the conversion
of 1 into 2 is the first observation of nitrogen expulsion from a
[15]
fullycharacterized cyclic phosphazide.
We then wondered if the sense of twist (P/M) of the helical
asymmetry of cages type 2 could be controlled bythe
configuration of a single chiral carbon atom on one of the
arms. Byusing standard methods, we synthesized a-methyl
substituted triazides 3 in racemic form, which were converted
into tri-l5-phosphazenes 4 (Scheme 2).
CH3
N
R
Figure 1. a) Molecular structure of 2b (hydrogen atoms omitted for
clarity), b) perspective view as projected along the threefold axis.
a) CH3C(CH2PPh2)3, Et2O, RT
b) CDCl3, 333 K
N3
N3
2
like shape is clearlyapparent when the molecule is viewed
along this axis (Figure 1b). Both propeller units, the upper
tribenzylamine core and the lower tert-pentane fragment,
present the same helical twist sense, M[9] (Figure 1b). The
twist apparentlyarises from the need to minimize the volume
of the unoccupied molecular cavity. The cavity is too small to
include anyavailable guest species and therefore screws down
upon itself like the lid of a screw-top jar, which results in a
cavityof almost negligible volume. Four molecules of chloro-
form cocrystallize with 2b. One of these chloroform mole-
R
3
CH3
R
N
a : R = H
b : R = Cl
N
N
N
P
P
P
CH3
4
Scheme 2. Preparation of a-methyl tri-l5-phosphazenes 4.
ˆ
cules engages in a CH ¥¥¥ N hydrogen bond to one of the N P
nitrogen atoms (C ¥¥¥ N 3.155 ä), while the others form strong
CH ¥¥¥ p-system interactions with H ¥¥¥ centroid distances both
approximately2.45 ä (C ¥¥¥ centroid 3.388 and 3.413 ä).
The NMR spectroscopic data of compound 2b in CDCl3
solution at 298 K (particularlythe magnetic nonequivalence
of the diastereotopic ligands), similar to those of 2a, revealed
that the solid state conformation of compounds 2 is probably
retained in solution at 298 K. High-temperature 1H NMR
experiments (compound 2b, o-Cl2C6D4 solution) demonstrat-
ed the simultaneous coalescence of the signals of the
methylene CH2N and CH2P protons at 423 K. At this temper-
ature, the coalescence of signals for the two phenyl groups on
the phosphorus atom was also observed in the 13C{1H} NMR
spectrum. On cooling to 298 K, the spectrum recovered its
original appearance. These results are explained byequilibra-
tion, at the coalescence temperature, between the two
enantiomeric propeller-like forms of 2b via a labile confor-
Although two diasteroisomeric pairs (R,P/S,M and
R,M/S,P) are possible for both 4a and 4b, these compounds
were obtained as single diastereoisomers in 70 and 63% yield,
respectively(based on the starting triazides). An X-raycrystal
structure determination showed 4b to be the R,M/S,P
diastereoisomer (Figure 2). The same stereochemistrywas
assumed for 4a as a consequence of the close similarityof its
spectral data to that of 4b.
These results demonstrate that the helical asymmetry of the
bicyclic, propeller-like cages 4 is totallycontrolled bythe
absolute configuration of their single stereogenic benzylic
carbon atoms. This control seems to be determined bythe
marked preference of the methyl group for the occupation of
a −pseudoaxial× position (parallel to the pseudo C3 axis)
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recrystallized from hot methanol (25 mL). After 16 h at room temperature,
the solid was collected byfiltration and dried to give the amine tartrate
salt (0.84 g). The salt was suspended in dichloromethane (30 mL), 1m
NaOH (20 mL) was added and the mixture was stirred for 1 h. The organic
layer was separated, the aqueous layer was extracted twice (CH2Cl2, 2 Â
20 mL), and the combined organic extracts were dried over MgSO4. The
solvent was removed under reduced pressure to give (S)-1-(3-azidophenyl)-
ethylamine (0.41 g, 45%). The a-methoxy-a-phenyl-a-(trifluoromethyl)-
acetamide of this material was prepared from (R)-(‡)-a-methoxy-a-
trifluoromethylbenzeneacetic acid (MPTA) and N,N'-dicyclohexylcarbo-
diimide (DCC) and analyzed by 1H and 19F NMR spectroscopyto reveal a
diastereoisomeric ratio of 95:5, the major isomer was the (S)-1-(3-
azidophenyl)ethylamine. A third recrystallization of the amine tartrate
salt from methanol (15 mL) afforded 0.63 g of the salt, which yielded (S)-1-
(3-azidophenyl)ethylamine upon addition of base a2D0 ˆ À26.28 (c ˆ 8.3 Â
10À3 in CHCl3, 98% ee). Mosher amide of (S)-1-(3-azidophenyl)ethyl-
amine: yield 94%; m.p. 69 718C; 1H NMR (300 MHz, CDCl3, 258C,
TMS): d ˆ 1.49 (d, J ˆ 6.8 Hz, 3H, CH3), 3.43 (d, J ˆ 6.8 Hz, 3H, OCH3),
5.14 (q, J ˆ 6.8 Hz, 1H, CH), 7.12 (m, 9H); 13C NMR (75.4 MHz, CDCl3,
258C): d ˆ 21.53 (CH3), 48.65 (OCH3), 54.94 (CH), 84.15 (q, 2J(C,F) ˆ
26.7 Hz, CCF3), 116.66, 118.08, 122.72, 123.75 (q, 1J(C,F) ˆ 289.5 Hz,
CF3), 127.56, 128.19, 128.51, 129.00, 129.50, 130.04, 132.37 (q), 140.42 (q),
144.70 (q), 165.46 (q, CO); 19F NMR (282.4 MHz, CDCl3, 258C): d ˆ 9.07;
Figure 2. Molecular structure of 4b with hydrogen atoms omitted for
claritya) side view, b) perspective view as projected along the pseudo-
threefold axis.
instead of the alternative pseudoequatorial situation closer to
the internal cavity, and therefore to the aryl groups. The sense
of twist of the arm bearing the a-methyl group in turn
determines those of the other two arms (Scheme 3).[16]
IR (Nujol): nÄ ˆ 2121 (N3), 1690 (C O) cmÀ1. The alkylation of (S)-1-(3-
ˆ
azidophenyl)ethylamine with 3-azido-6-chlorobenzyl iodide as above
yielded (S)-3b in 22% yield. a2D0 ˆ À33.08 (c ˆ 6.0  10À3 in CHCl3).
General synthesis of 4: Two solutions of the corresponding tribenzylamine
3 (5 mL, 0.5 mmol, 0.1m in CDCl3) and [2-((diphenylphosphino)methyl)-2-
Ar
N
Ar
H
H
H
H3C
Ar
N
H
Ar
Ar
Ar
methyl-1,3-propanediyl]bis[diphenylphosphine](TRIPHOS;
5 mL,
(S,P)
(S,M)
0.5 mmol, 0.1m in CDCl3) were simultaneouslyadded to a round-bottom
flask containing CDCl3 (10 mL) under nitrogen at room temperature, over
a period of 1 h with stirring. The resulting mixture was then stirred for
about 3 h (monitoring byIR) at room temperature. After this time, the
mixture was placed in an oil bath and heated at 608C for 24 h. After
cooling, the solvent was removed under reduced pressure and the crude
product was crystallized from a mixture of chloroform and hexane. The
compounds 4a and 4b were obtained in 70% and 64% yield, respectively.
CH3 pseudoaxial
CH3 pseudoequatorial
disfavoured
favoured
Scheme 3.
The calculated[17] difference in energybetween both
diastereoisomers of 4b is 3.89 kcalmolÀ1 in favor of the one
present in the crystal. When enantioenriched (À)-(S)-3b
(98% ee) was used in the procedure described in Scheme 2,
opticallyactive ( S,P)-4b (aD ˆ ‡398.48, c ˆ 6.20  10À3 in
CHCl3) of definite helical sense was obtained.
The present case of point-to-helix chiralitytransfer at the
molecular level in discrete organic compounds maybe added
to the limited number of such cases reported mainlyin metal-
coordinated systems[18] and polymeric superstructures.[19]
Received: November 9, 2001 [Z18193]
[1] K. P. Meurer, F. Vˆgtle, Top. Curr. Chem. 1985, 127, 1; L. J. Prins, J.
Huskens, F. De Jong, P. Timmerman, D. N. Reinhoudt, Nature 1999,
398, 498.
[2] E. L. Eliel, S. H. Wilen, L. N. Mander, Stereochemistry of Organic
Compounds, Wiley, New York, 1994, p. 1156.
[3] K. Mislow, Acc. Chem. Res. 1976, 9, 26; K. Mislow, D. Gust, P.
Finocchiaro, R. J. Boettcher, Fortschr. Chem. Forsch. 1974, 47, 1; K. P.
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[4] a) J.-M. Lehn, J.-P. Vigneron, Y. Bkouche Waksman, J. Guilhem, C.
Pascard, Helv. Chim. Acta 1992, 75, 1069; b) M. Nakazaki, K.
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West, Jr., D. V. Engen, R. A. Pascal, Jr., J. Am. Chem. Soc. 1991,
113, 2672; e) C. Bolm, K. B. Sharpless, Tetrahedron Lett. 1988, 29,
5101; f) C. Bolm, W. D. Davis, R. L. Haltermann, K. B. Sharpless,
Angew. Chem. 1988, 100, 882; Angew. Chem. Int. Ed. Engl. 1988, 27,
835.
Experimental Section
General synthesis of 2: A solution of compound 1 (5 mL, 1 mmol, 0.2m in
CDCl3) placed in a looselysealed round-bottom flask, immersed in an oil
bath, was heated at 608C for 24 h. After cooling, the solvent was removed
under reduced pressure and the crude product was crystallized from a
mixture of dichloromethane and diethyl ether. In this way compounds 2a
and 2b were obtained in 75% and 74% yield, respectively.
General synthesis of rac-tribenzylamines 3: The corresponding 3-azido-
benzyl iodide (4 mmol) was added to a solution of rac-1-(3-azidophen-
yl)ethylamine (30 mL, 2 mmol, 0.07m in dioxane). The mixture was heated
under reflux with stirring for 4 h. After cooling to room temperature, an
excess of triethylamine (0.45 g, 4.5 mmol) was added at once, and the
mixture stirred for 2 h. The precipitated triethylammonium iodide was
separated byfiltration. The dioxane was removed from the filtrate under
reduced pressure and the residue was chromatographed (silica gel; ethyl
acetate/n-hexane (1:9)). In this waycompounds 3a and 3b were obtained in
44% and 27% yield, respectively.
¬
¬
[5] a) M. AlajarÌn, P. Molina, A. Lopez Lazaro, C. Foces Foces, Angew.
Chem. 1997, 109, 147; Angew. Chem. Int. Ed. Engl. 1997, 36, 67; b) M.
¬
¬
AlajarÌn, A. Vidal, C. Lopez Leonardo, J. Berna, M. C. RamÌrez
de Arellano, Tetrahedron Lett. 1998, 39, 7807; c) M. AlajarÌn, A.
¬
¬
¬
Lopez Lazaro, A. Vidal, J. Berna, Chem. Eur. J. 1998, 4, 2558.
[6] The imination of tertiaryphosphanes byazides, via intermediate
phosphazides, to yield l5-phosphazenes is known as the Staudinger PIII
1
2
1
2
1
ˆ À ˆ À
ˆ
imination reaction: R3P ‡ R N3 !R3P N N N R !R3P NR2
‡
N2. For references and reviews see: H. Staudinger, J. Meyer, Helv.
Chim. Acta 1919, 2, 635; Y. G. Gololobov, L. F. Kasukhin, Tetrahedron
1992, 48, 1353; Y. G. Gololobov, Y. N. Zhmurova, L. F. Kasukhin,
Tetrahedron 1981, 37, 437; A. W. Johnson, Ylides and Imines of
Phosphorus, Wiley, New York, 1993, p. 403. For recent high level
calculations on the mechanism of the Staudinger PIII imination
Preparation of (S)-3b: rac-1-(3-Azidophenyl)ethylamine (1.84 g,
11.3 mmol) and (R,R)-tartaric acid (1.70 g, 11.3 mmol) were dissolved in
hot methanol (40 mL). The solution was cooled to room temperature. After
12 h, the supernatant liquid was separated and the white solid was
Angew. Chem. Int. Ed. 2002, 41, No. 7
¹ WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002
1433-7851/02/4107-1207 $ 20.00+.50/0
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reaction see: M. AlajarÌn, C. Conesa, H. S. Rzepa, J. Chem. Soc.
À
Alkene C H Activations at Dinuclear
Perkin Trans.
2 1999, 1811; C. Widauer, H. Gr¸tzmacher, Y.
Complexes Promoted by Oxidation**
Shevchenko, V. Gramlich, Eur. J. Inorg. Chem. 1999, 1659.
[7] New compounds have been fullycharacterized byspectroscopic
methods and elemental composition (see Supporting Information).
[8] Crystal structure analysis of 2b ¥ 4CHCl3: C66H58Br3Cl12N4P3, Mr ˆ
¬
M. Victoria Jimenez, Eduardo Sola, Javier Caballero,
Fernando J. Lahoz, and Luis A. Oro*
1665.20 gmolÀ1
,
triclinic space group P1, a ˆ 12.8432(4), b ˆ
≈
14.7484(6), c ˆ 19.5242(5) ä, a ˆ 85.839(2), b ˆ 89.058(2), g ˆ
72.373(2)8, Vˆ 3515.2(2) ä3, Z ˆ 2, unique data 15993 (2q ꢀ 558),
parameters 795, R1 [F 2 > 2s(F 2)] 0.044, wR2 (all data) 0.094. Crystal
structure analysis of 4b: C67.5H59Cl15.26N4P3, Mr ˆ 779.85 gmolÀ1, tri-
Several recent discoveries in the chemistryof transition
metal di- and polynuclear complexes have disclosed new
methods of hydrocarbon activation and functionalization,
[1, 2]
favored bypolynuclear environments.
In parallel, consid-
≈
clinic space group P1, a ˆ 12.453(3), b ˆ 14.853(3), c ˆ 19.456(6) ä,
a ˆ 85.522(14), b ˆ 89.845(15), g ˆ 72.399(12)8, Vˆ 3419.0(15) ä3,
Z ˆ 2, unique data 10508 (2q ꢀ 488), parameters 796, R1 [F 2 >
2s(F 2)] 0.190, wR2 (all data) 0.422. The poor overall precision
resulted from the presence of a great deal of disordered chloroform,
coupled with poor overall crystal quality as a result of decomposition.
The structural details of the macrobicycle are clear and unambiguous,
however. CCDC-143862 (2b), and -172792 (4b) contain the supple-
mentarycrsytallographic data for this paper. These data can be
obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html
(or from the Cambridge Crystallographic Data Centre, 12, Union
Road, Cambridge CB2 1EZ, UK; fax: (‡44)1223-336-033; or deposit
@ccdc.cam.ac.uk).
erable progress has been made in understanding the reactivity
features resulting from multimetallic reaction sites.[1, 3, 4]
Together, such advances maycontribute to the rational design
of new catalysts and applications based on this type of
compound. However, the proximityof the metal centers is
likelyto have significant repercussions for the reactivit,y
which remain to be determined.
In our recent studies on ™open-book∫ d8 diiridium com-
plexes with N-donor bridges, we have observed a remarkable
substrate selectivityin the reactions of these compounds
towards oxidative addition reactants. Whereas the d8 diiri-
dium complexes underwent fast SN2 oxidative additions with
substrates such as halocarbons,[4] the additions of less-polar
reactants such as dihydrogen were not observed. The oxida-
tion of these d8d8 diiridium compounds, to species of d6d8 or
d7d7 electronic configurations, gave dihydrogen-activating
compounds.[5] Here we report that such an oxidation strategy
also allows the transformation of nonreactive d8d8 compounds
[9] The conventional assignment of the stereochemical descriptor P or M
(helical twist sense) to the propeller units of the chiral macrobicycles
was made bylooking at the molecule along its threefold axis from the
side of the tribenzylamine fragment.
[10] The activation energywas calculated from the equation: DG=ˆ
(4.57  10À3) Tc (10.32 ‡ log(Tc 2/pDn)) following: D. H. Williams, I.
Fleming, Spectroscopic Methods in Organic Chemistry, 4th ed.,
McGraw-Hill, New York, 1989, p. 103.
[11] H. Gilboa, J. Altman, A. Loewenstein, J. Am. Chem. Soc. 1969, 91,
6062.
[12] R. W. Alder, R. J. Arrowsmith, J. Chem. Res. (S) 1980, 163.
[13] Compounds 2 did not hydrolize on heating solutions in a mixture of
THF:H2O (5:1, v:v) at 608C for 48 h, monitored by 1H and 31P{1H}
NMR.
[14] Macrobicyclic cryptands with two intracyclic P ˆ N units have been
characterized, see: J. Mitjaville, A.-M. Caminade, R. Mathieu, J.-P.
Majoral, J. Am. Chem. Soc. 1994, 116, 5007. For a review on bicyclic
phosphorus compounds see: A.-M. Caminade, R. Kraemer, J.-P.
Majoral, New J. Chem. 1997, 21, 627.
[15] A.-M. Caminade, J.-P. Majoral, Chem. Rev. 1994, 94, 1183.
[16] A comparable situation has been found in the tricyclic 2-methyl-1-
azonia[4.4.4]propellane cation, see: J. M. McIntosh, J. Org. Chem.
1982, 47, 3777.
[17] Semi-empirical calculations were carried out byusing the MNDO
method as implemented in the Gaussian 98 set of programs. The
geometries of both stationarypoints were optimized, and harmonic
frequencycalculations were performed in order to characterize both
structures as minima.
À
into dinuclear C H activating species.
The treatment of the diamidonaphthalene ((NH2)naphth)-
bridged diiridium(iii) complex [Ir2(m-1,8-(NH)2naphth)-
(m-H)H3(NCCH3)(PiPr3)2] (1) with two equivalents of an
internal alkyne such as 2-butyne or diphenylacetylene afford-
ed diiridium(i) derivatives of the formula [Ir2(m-1,8-
2
ˆ
(NH)2naphth)(h -Z-RHC CHR)2(PiPr3)2] (R ˆ Me (2), Ph
(3)) [Eq. (1)]. The solution NMR spectra of both compounds
indicate symmetric C2 structures with a transoid arrangement
of nonrotating Z-alkene ligands. These features have been
confirmed bythe X-raycrystallographic determination of the
structure of 2,[6] (Figure 1).
[18] T. Mizutani, S. Yagi, T. Morinaga, T. Nomura, T. Takagishi, S.
Kitagawa, H. Ogoshi, J. Am. Chem. Soc. 1999, 121, 754; J. W. Canary,
C. S. Allen, J. M. Castagnetto, Y. Wang, J. Am. Chem. Soc. 1995, 117,
8484; Y. Yao, C. J. A. Daley, R. McDonald, S. H. Bergens, Organo-
metallics 1997, 16, 1890.
[19] L. J. Prins, J. Husken, F. De Jong, P. Timmerman, D. N. Reinhoudt,
Nature 1999, 398, 498; D. B. Amabilino, E. Ramos, J.-L. Serrano, T.
Sierra, J. Veciana, J. Am. Chem. Soc. 1998, 120, 9126; R. B. Prince, L.
Brunsveld, E. W. Meijer, J. S. Moore, Angew. Chem. 2000, 112, 234;
Angew. Chem. Int. Ed. 2000, 39, 228.
¬
[*] Prof. Dr. L. A. Oro, Dr. M. V. Jimenez, Dr. E. Sola,
Dipl.-Chem. J. Caballero, Dr. F. J. Lahoz
¬
Departamento de QuÌmica Inorganica
¬
Instituto de Ciencia de Materiales de Aragon
Universidad de Zaragoza-CSIC
50009 Zaragoza (Spain)
Fax : (‡34)976-761143
E-mail: oro@posta.unizar.es
¬
[**] We are grateful to the Plan Nacional de Investigacion, Ministerio de
Ciencia yTecnologÌa, for the support of this research (Project
No. BQU2000-1170).
1208
¹ WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002
1433-7851/02/4107-1208 $ 20.00+.50/0
Angew. Chem. Int. Ed. 2002, 41, No. 7