Cyclodextrin cavities as probes for ligand-exchange processes

Article abstract of DOI:10.1002/1521-3773(20010702)40:13<2526::AID-ANIE2526>3.0.CO;2-T

A multitopic cavity equipped with two phosphorus and four oxygen donor atoms has been successfully used for the covalent entrapment of organometallic fragments. The α-cyclodextrin-silver complex 1 is able to reversibly host one or two acetonitrile ligands.

Full text of DOI:10.1002/1521-3773(20010702)40:13<2526::AID-ANIE2526>3.0.CO;2-T

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telluride group relative to that of an iodine atom.[15] Some
experimental results are included in Table 1 and demonstrate
the efficiency of the phenyl telluride approach. The reaction
was successful with secondary and primary alkyl tellurides.
We briefly examined a sequential radical reaction involving a
cyclization and acylation sequence [Eq. (7)]. Reaction of 21
1988, pp. 1089 ± 1113; c) M. Bertrand, Org. Prep. Proced. Int. 1994, 26,
257 ± 290.
[9] S. Kim, J.-Y. Yoon, I. Y. Lee, Synlett 1997, 475 ± 476.
[10] a) D. Crich, L. Quintero, Chem. Rev. 1989, 89, 1413 ± 1432; b) J.
Boivin, J. Camara, S. Z. Zard, J. Am. Chem. Soc. 1992, 114, 7909 ±
7910; c) B. Quiclet-Sire, S. Z. Zard, J. Am. Chem. Soc. 1996, 118,
9190 ± 9191; d) S. Z. Zard, Angew. Chem. 1997, 109, 724 ± 737; Angew.
Chem. Int. Ed. Engl. 1997, 36, 672 ± 685; e) B. Quiclet-Sire, S. Seguin,
S. Z. Zard, Angew. Chem. 1998, 110, 3056 ± 3058; Angew. Chem. Int.
Ed. 1998, 37, 2864 ± 2866.
[11] a) D. H. R. Barton, J. C. Jaszberenyi, E. A. Theodorakis, J. Am. Chem.
Soc. 1992, 114, 5904 ± 5905; b) M. A. Lucas, C. H. Schiesser, J. Org.
Chem. 1996, 61, 5754 ± 5761.
[12] a) C. Chen, D. Crich, A. Papadatos, J. Am. Chem. Soc. 1992, 114,
8313 ± 8314; b) C. Chen, D. Crich, Tetrahedron Lett. 1993, 34, 1545 ±
1548; c) D. Crich, C. Chen, J.-T. Hwang, H. Yuan, A. Papadatos, R. I.
Walter, J. Am. Chem. Soc. 1994, 116, 8937 ± 8951.
E
E
OBn
Me
E
E
5, V-40
tBuC6H5, 140 o
N
OBn
+
(7)
N
C
H
X
H
8
22
20:
21:
31%
67%
X = I
55%
0%
X = TePh
[13] D. P. Curran, A. A. Martin-Esker, S.-B. Ko, M. Newcomb, J. Org.
Chem. 1993, 58, 4691 ± 4695.
[14] L.-B. Han, K.-I. Ishihara, N. Kambe, A. Ogawa, I. Ryu, N. Sonoda, J.
Am. Chem. Soc. 1992, 114, 7591 ± 7592.
[15] We thank the referees for suggesting a competition experiment and
for drawing our attention to ref. [13].
with 5 under the same conditions afforded the desired oxime
ether 22 in 67% yield, whereas the use of iodide 20 gave 22 in
31% yield along with 8 (55%); this demonstrates the
efficiency of the phenyl telluride group as a radical precursor.
Experimental Section
Typical procedure: A degassed solution of 1-bromo-4-iodomethyl-benzene
(118 mg, 0.40 mmol), O-benzyl-1-(methanesulfonyl)formaldoxime (5,
128 mg, 0.60 mmol) and V-40 (20 mg, 0.08 mmol) in freshly distilled octane
(2 mL) was heated to reflux under N2 for 8 h. The solvent was evaporated
under reduced pressure, and the residue was purified by chromatography
on a silica gel column (n-hexane: ethyl acetate 1:15) to yield O-benzyl-1-(4-
bromobenzyl)formaldehyde (98 mg, 0.32 mmol, 80% yield, E:Z ˆ 1.1:1).
1H NMR (CDCl3, 200 MHz): E isomer: d ˆ 3.45 (d, J ˆ 6.4 Hz, 2H), 5.08 (s,
2H), 7.06 (d, J ˆ 2.2 Hz, 2H), 7.32 ± 7.43 (m, 7H), 7.49 (t, J ˆ 6.4 Hz, 1H); Z
isomer: d ˆ 3.65 (d, J ˆ 5.4 Hz, 2H), 5.15 (s, 2H), 6.80 (t, J ˆ 5.4 Hz, 1H),
7.02 (d, J ˆ 2.2 Hz, 2H), 7.32 ± 7.43 (m, 7H); 13C NMR (CDCl3, 100 MHz):
d ˆ 31.9, 35.3, 75.8, 76.1, 120.5, 120.8, 127.8, 127.9, 128.2, 128.4, 128.6, 128.8,
130.4, 130.5, 131.7, 131.8, 135.3, 135.8, 137.6, 137.7, 149.0, 149.3; IR (NaCl):
nÄ ˆ 3031, 2928, 1656, 1586, 1488, 1454, 1367, 1276, 1072, 1012 cm 1; HR-MS:
Cyclodextrin Cavities as Probes for Ligand-
Exchange Processes
Eric Engeldinger, Dominique Armspach,* and
Dominique Matt*
Cyclodextrins (CDs) have attracted a lot of attention as
chiral building blocks for the construction of enzyme mimics
because of their ability to bind a wide range of organic
substrates in water.[1±4] Combining CDs with transition metals
has proven a very attractive goal in terms of achieving highly
selective and efficient catalysis.[5±11] One of the challenges, so
far not met, is to force a metal that is covalently linked to a
CD framework to be confined in the cavity where maximum
interaction between the first coordination sphere of the metal
and the CD walls is expected to take place so as to stabilize
unusual coordination modes. In addition, cavities with intro-
verted[12] functionalities could provide new catalysts where a
metal center operates inside a spatially restricted environ-
ment.[13±15] We report here the first a-CD-based multitopic
ligand (2) capable of hosting metal ± organic fragments. As
shown by NMR investigations, the complexes derived from
this ligand display unique intra- and intermolecular ligand-
exchange phenomena at the included metal center.
‡
[M ] calcd for C15H14BrNO: 303.0259; found: 303.0257.
Received: February 5, 2001 [Z16557]
[1] P. A. Baguley, J. C. Walton, Angew. Chem. 1998, 110, 3272 ± 3283;
Angew. Chem. Int. Ed. 1998, 37, 3072 ± 3082, and references therein.
[2] a) B. Quiclet-Sire, S. Z. Zard, J. Am. Chem. Soc. 1996, 118, 1209 ±
1210; b) F. L. Guyader, B. Quiclet-Sire, S. Seguin, S. Z. Zard, J. Am.
Chem. Soc. 1997, 119, 7410 ± 7411; c) F. Bertrand, B. Quielet-Sire, S. Z.
Zard, Angew. Chem. 1999, 111, 2135 ± 2138; Angew. Chem. Int. Ed.
1999, 38, 1943 ± 1946.
[3] a) J. Gong, P. L. Fuchs, J. Am. Chem. Soc. 1996, 118, 4486 ± 4487; b) J.
Gong, P. L. Fuchs, Tetrahedron Lett. 1997, 38, 787 ± 790; c) J. Xiang,
P. L. Fuchs, J. Am. Chem. Soc. 1996, 118, 11986 ± 11987; d) J. Xiang,
W. Jiang, J. Gong, P. L. Fuchs, J. Am. Chem. Soc. 1997, 119, 4123 ±
4129.
[4] C. Ollivier, P. Renaud, J. Am. Chem. Soc. 2000, 122, 6496 ± 6497.
[5] a) S. Kim, I. Y. Lee, J.-Y. Yoon, D. H. Oh, J. Am. Chem. Soc. 1996, 118,
5138 ± 5139; b) S. Kim, J.-Y. Yoon, J. Am. Chem. Soc. 1997, 119, 5982 ±
5983.
We anticipated that an easy way to ensure metal encapsu-
lation in a cavity would be to use an a-CD derivative bearing
[6] a) D. P. Curran, M.-H. Chen, D. Kim, J. Am. Chem. Soc. 1986, 108,
2489 ± 2490; b) D. P. Curran, D. Kim, Tetrahedron Lett. 1986, 27,
5821 ± 5814; c) D. P. Curran, D. Kim, Tetrahedron 1991, 47, 6171 ±
6188; d) D. P. Curran, D. Kim, C. Zigler, Tetrahedron 1991, 47,
6189 ± 6196.
[7] S. Kim, I. Y. Lee, Tetrahedron Lett. 1998, 39, 1587 ± 1590.
[8] a) A. Horowitz, L. A. Rajbenbach, J. Am. Chem. Soc. 1975, 97, 10 ± 13;
b) C. Chatgilialoglu in The Chemistry of Sulfones and Sulfoxides
(Eds.: S. Patai, Z. Rappoport, C. J. M. Stirling), Wiley, Chichester,
[*] Dr. D. Armspach, Dr. D. Matt, E. Engeldinger
Â
Laboratoire de Chimie Inorganique Moleculaire, UMR 7513 CNRS
Â
Universite Louis Pasteur
1, rue Blaise Pascal, 67008 Strasbourg Cedex (France)
Fax : (‡33)3-90-240-722
E-mail: dmatt@chimie.u-strasbg.fr
Supporting information for this article is available on the WWW under
http://www.angewandte.com or from the author.
2526
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2
MeO
OMe
1
3
MeO
P
OMe
MeO
OMe
MeO
OMe
O
OMe
4
BF4
BF4
OMe
O
O
5
MeO6
OMe
O
O
Ph2P
PPh2
P
P
P
MeO
OMe
OMe
MeO
MeO
MeO
MeO
Ag
Ag
O
O
OMe
OSO2Me
MeO2SO
N
C
MeO
N
C
N
C
O
LiPPh2
(1)
OMe
OMe
O
THF
OMe
MeO
O
Me
Me
Me
O
O
MeO
MeO
OMe
3
4
1
BF4
2
BF4
MeO
OMe
OMe
MeO
P
P
Ag
P
P
OMe
MeO
MeO
Ag
donor functions that preferentially point inside the CD. This
feature is realized in diphosphane 2, in which the orientation
of the phosphorus lone pairs is controlled by steric inter-
actions between the CD matrix and the closely appended
phosphanyl groups. The presence of adjacent methoxy groups
provides additional binding sites that may help metal
stabilization. Two diphenylphosphanyl fragments were graft-
ed onto the C-6 atoms of the A and D units of an a-CD
platform by using a method developed by Brown et al. for the
functionalization of trehalose units.[16] Thus, the reaction of
the known dimesylate 1[17] with lithium diphenyl phosphide in
THF afforded compound 2 in high yield [Eq. (1)]. The 31P
NMR spectrum of the resulting chiral diphosphane consists of
a singlet at d ˆ 17.9 commensurate with its expected C2
symmetry. The latter was confirmed by the presence of eight
methyl signals as well as three doublets for the H-1 protons in
MeO
N
C
5
6
1H NMR study. Thus, at room temperature, the H NMR
spectrum of 5, recorded in C2D2Cl4, reveals the presence of
two distinctive species (45:55 ratio) both of which have
averaged C2 symmetry. As the sample is heated, the signals
first broaden, then coalesce near 708C, and finally sharpen to
produce a spectrum with half the number of signals, consistent
with a rapid equilibration of the (B,E)[23] and (C,F) glucose
units (Scheme 1, equilibrium B). The calculated energy bar-
1
1
the H NMR spectrum. Interestingly, the proximity of the
chiral cavity produces a strong differentiation between the
two phenyl groups attached to each phosphorus atom as
revealed by 13C NMR spectroscopy. This effect is no longer
observed when the coordinating atoms are separated from the
C-6 atoms by longer spacers like phenylene.[18]
1
rier for this process is about 67.8 kJmol . Upon cooling a
CD2Cl2 solution of 5 to
208C, the room-temperature
B
C
The reaction of ligand 2 with one equivalent of AgBF4 in
MeCN leads to the quantitative formation of the complex
[Ag(2)(CH3CN)2]BF4 (3), which is only stable in the presence
of a large excess of MeCN (>15 equiv). The formulation of 3
was inferred from its ES-MS spectrum, which revealed the
OMe
MeO
OMe
MeO
P
P
A
Ag
Ag
D
P
P
MeO
OMe
MeO
OMe
F
E
‡
presence of a strong peak for the [M‡H2O] ion[19] together
with fragmentation peaks resulting from loss of one and two
molecules of MeCN. The 1H, 13C, and 31P NMR spectra are all
consistent with a C2-symmetrical complex. Furthermore, the
2D ROESY spectrum of 3 in a CDCl3 solution containing
15 equivalents of MeCN clearly shows cross-peaks corre-
sponding to NOEs between the coordinated MeCN mole-
cules[20] and all the H-3 CD protons as well as two types of H-5
CD proton[21] but no through-space correlations between
MeCN with protons outside the cavity.[22] These observations
are fully consistent with coordinated MeCN molecules that
are located inside the cavity.
B
OMe
MeO
OMe
MeO
P
P
Ag
Ag
P
P
MeO
OMe
MeO
OMe
A2
A1
Scheme 1. Hemilabile behavior of ligand 2 in complex 5. A1 and A2, low-
energy dynamics; B, high-energy exchange processes.
Upon evaporation of MeCN, 3 loses coordinated MeCN to
produce complexes 4 and 5 in a 80:20 mixture whose ratio
does not decrease significantly after prolonged drying in
vacuo at 908C. However, as confirmed by 31P NMR spectros-
copy and microanalysis, quantitative formation of 5 occurs
when acetone is added to the mixture prior to evaporation.
Coordination of one of the four MeO-6 groups to the silver
atom in 5 was inferred from a temperature-dependent
spectrum no longer persists. Indeed, two new sets of signals
emerge that correspond to two C1-symmetrical species,
reflecting a slow exchange on the 1H NMR time scale
between diametrically opposed MeO-6 groups (Scheme 1,
equilibria A1 and A2).[24] Overall, our findings are best
rationalized in terms of ligand fluxionality about a tricoordi-
nate silver ion, the dynamics involving alternative binding of
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all four ether groups. Unsurprisingly, the hemilabile[25] behav-
ior of ligand 2 allows substitution of the coordinated oxygen
atom by stronger donors.
Finally, the addition of benzonitrile (ca. 8 equiv) to a
solution of 3 in a CHCl3/MeCN mixture (3/MeCN ˆ 1:15)
resulted in the quantitative formation of complex 6 in which a
single benzonitrile molecule is coordinated to the silver ion, as
revealed by the corresponding ES-MS spectrum. A range of
correlations between some H-3 as well as MeO-3 protons[29]
and aromatic protons belonging to the entrapped guest in the
2D ROESY spectrum of 6 confirmed the inclusion of
benzonitrile in the CD cavity. Careful examination of the
2D spectra reveals that, upon complexation, the orientation of
the benzonitrile plane must be close to that of the P-Ag-P
plane. In addition, as a result of the magnetic field anisotropy
created by the included phenyl ring, the MeO-3 and MeO-2
The addition of 5 ± 10 equivalents of MeCN to a solution of
5 in CDCl3 led to a mixture of complexes 3 and 4, both of
which interconvert with 5, as revealed by NMR experiments.
A larger excess of MeCN causes 4 to bind an extra MeCN
molecule to give 3 exclusively. Conversely, dilution of
solutions containing 3 with CDCl3 regenerated compounds 4
and 5. The C2 symmetry of the trigonal complex 4 was
confirmed by NMR spectroscopy as well as by a single-crystal
X-ray diffraction study (Figure 1). As anticipated, the two
1
signals in the H NMR spectrum (CDCl3) are considerably
more spread out in 6 than in 3 (Dd ˆ 0.65 vs. 0.2). Clearly, the
CD cavity does not allow the coordination of more than one
benzonitrile molecule, but can easily accomodate two smaller
nitrile ligands such as MeCN. Favorable van der Waals
interactions between the inner walls of the CD torus and
the cavity-matching phenyl residue, together with the better
electron-donating ability of benzonitrile, are likely to account
for the higher stability of 6 compared to 4.
Experimental Section
2: Selected data: 1H NMR (400.1 MHz, CDCl3, 258C; assignment by
2
or
COSY): d ˆ 2.18, 3.29 (AB, JAB ˆ 10.4 Hz, 4H; H-6C,F B,E), 2.50, 2.67
(brAB, 4H; H-6A,D), 2.76 (s, 6H; CH3O-6), 2.99 (s, 6H; CH3O-6), 3.10 (dd,
2H; H-2C,For B,E), 3.15 (dd, 2H; H-2B,E or C,F), 3.22 (dd, 2H; H-2A,D), 3.28, 4.05
Figure 1. X-ray structure of 4 showing the encapsulated MeCN ligand. The
BF4 ion and the solvent molecules are not shown. Selected bond lengths
[Š] and angles [8]: Ag-P(1) 2.570(4), Ag-P(2) 2.558(4), Ag-N(1) 2.41 (1),
P(1)-Ag-P(2) 142.9(1), P(1)-Ag-N(1) 108.9(4), P(2)-Ag-N(1) 108.2(4), Ag-
N(1)-C(1) 158.3 (2), N(1)-C(1)-C(2) 173.2 (2). Shortest Ag ´´´ O separation:
3.86(1) Š (Ag-O(25)).
(AB, JAB ˆ 10.5 Hz, 4H; H-6B,E C,F), 3.40 (t, 2H; H-4A,D), 3.45 (s, 6H;
OCH3), 3.47 (s, 6H; OCH3), 3.51 (s, 6H; OCH3), 3.57 (t, 2H; H-3A,D), 3.58
(t, 2H; H-3C,F or B,E), 3.59 (t, 2H; H-3B,E or C,F), 3.61 (s, 6H; OCH3), 3.63 (s,
6H; OCH3), 3.64 (t, 2H; H-4C,F or B,E), 3.64 (t, 2H; H-5C,F or B,E), 3.65 (s, 6H;
OCH3), 3.71 (t, 3J ˆ 8.9 Hz, 2H; H-4B,E or C,F), 3.79 (m, 2H, 3J ˆ 9.6 Hz, 2H;
H-5B,E or C,F), 4.39 (m, 3J ˆ 8.8 Hz, 2H; H-5A,D), 4.93 (d, 3JH-2,H-1 ˆ 2.9 Hz, 2H;
H-1A,D), 5.01 (d, 3JH-2,H-1 ˆ 3.2 Hz, 2H; H-1B,E or C,F), 5.03 (d, 3JH-2,H-1 ˆ 3.6 Hz,
2H; H-1C,F or B,E), 7.22 ± 7.64 (m, 20H; arom. H); 31P{1H} NMR (121.5 MHz,
CDCl3, 258C): d ˆ 17.8 (s). Elemental analysis (%): calcd for
C76H110O28P2 (1533.62): C 59.52, H 7.23; found: C 59.80, H 7.48.
2
or
phosphorus atoms point towards the interior of the cavity. The
trigonal-planar coordination mode forces the coordinated
MeCN molecule to be included in the CD cavity which does
not undergo significant deformation upon complexation.
However, compared to the related complex [Ag(PPh3)2(NC-
Me)]BF4,[26] the Ag P bonds are unusually long (av 2.56 Š vs.
2.44 Š), reflecting the shortness of the two phosphane arms.
Incidentally, the stereochemistry of the silver atom signifi-
cantly deviates from an ideal trigonal geometry; the P-Ag-P
angle (142.9(1)8) is considerably larger than 1208. This
geometry is comparable to those observed in trigonal-planar
silver complexes obtained with Venanziꢁs trans-spanning
ligands.[27] Interestingly, the Ag N bond is also longer than
usual (2.41(1) Š vs. 2.321(2) Š in [Ag(PPh3)2(NCMe)]BF4),
consistent with a weakly bonded nitrile. Finally, we note that
the nitrile rod is slightly bent with respect to the Ag N axis
(Ag-N(1)-C(1) 158.3(2)8).
3: The 31P NMR spectrum in CDCl3 reveals the presence of a mixture of 3,
107
4, and 5 (31P{1H} NMR (121.5 MHz, CDCl3, 258C): d ˆ 7.7 (2 d,
J
ˆ
Ag,P
109
107
107
109
458,
(2d,
J
ˆ 529 Hz; 3), 6.1 (2d,
J
Ag,P
ˆ 417,
J
Ag,P
ˆ 480 Hz; 4), 3.5
Ag,P
109
J
Ag,P
ˆ 503,
J
Ag,P
ˆ 581 Hz; 5)). When the spectrum was recorded in
1
pure CD3CN, only 3 was detected. H NMR (400.1 MHz, CD3CN, 258C):
d ˆ 2.52 (d, 2H, 2J ˆ 10.6 Hz; H-6bA,D, tentative assignment), 2.78 (s, 6H;
CH3O-6), 2.83 (s, 6H; CH3O-6), 3.43 (s, 6H; OCH3), 3.44 (s, 6H; OCH3),
3.49 (s, 6H; OCH3), 3.56 (s, 6H; OCH3), 3.57 (s, 6H; OCH3), 3.60 (s, 6H;
OCH3), 2.84 ± 3.69 (32H; H-2, H-3, H-4, H-5B,C,E,F, H-6a, H-6bB,C,E,F), 4.44
(m, 2H; H-5A,D), 4.79 (d, JH-2,H-1 ˆ 2.6 Hz, 2H; H-1), 4.95 (d, JH-2,H-1
ˆ
3
3
3
3.2 Hz, 2H; H-1), 5.14 (d, JH-2,H-1 ˆ 3.2 Hz, 2H; H-1), 7.35 ± 7.80 (m, 20H;
arom. H); 31P{1H} NMR (121.5 MHz, CD3CN, 258C): d ˆ 7.6 (2 d,
J
Ag,P
ˆ
107
109
‡
458,
J
ˆ 529 Hz); MS (ES): m/z (%): 1741.3 (13) [M
BF4‡H2O]. As
Ag,P
deduced from 2D NMR experiments, the Me signals of free and
coordinated MeCN overlap (d ˆ 1.90 ± 2.10). All protons of 3 could be
assigned by a COSY experiment (CDCl3/CH3CN). The latter experiment
also allowed to unambiguously distinguish protons of 3 from those of 4.
5: 1H NMR (500.1 MHz, C2D2Cl4, 278C): d ˆ 2.81 (s, 3H; CH3O-6), 2.90 (s,
3H; CH3O-6), 3.07 (s, 3H; CH3O-6), 3.24 (s, 3H; CH3O-6), 3.36 (s, 3H;
OCH3), 3.42 (s, 3H; OCH3), 3.47 (s, 6H; OCH3), 3.49 (s, 6H; OCH3), 3.51
(s, 3H; OCH3), 3.59 (s, 3H; OCH3), 3.63 (s, 6H; OCH3), 3.64 (s, 3H;
OCH3), 3.74 (s, 3H; OCH3), 2.80 ± 4.30 (36H, H-2, H-3, H-4, H-5, H-6), 4.67
(d, 3JH-1, H-2 ˆ 2.0 Hz, 2H; H-1), 4.79 (d, 3JH-1, H-2 ˆ 4.2 Hz, 2H; H-1), 4.90 (d,
The aforementioned experiments provide, for the first time,
spectroscopic evidence for dinitrile complexes of the type
‡
[Ag(phosphane)2(MeCN)2] , although such species have al-
ready been proposed.[28] In contrast, related monoacetonitrile
silver cations are well documented.[26] Subtle interactions
between the cavity and the acetonitrile ligand may contribute
to the unexpected stabilization of the ªAg(MeCN)2º unit by
cavitand 2.
3JH-1,H-2 ˆ 2.6 Hz, 2H; H-1), 5.09 (d, 3JH-1,H-2 ˆ 3.0 Hz, 2H; H-1), 5.39 (d, 3JH-
3
ˆ 3.0 Hz, 2H; H-1), 5.45 (d, JH-1,H-2 ˆ 3.6 Hz, 2H; H-1), 7.10 ± 7.65
1,H-2
(20H; arom. H); 31P{1H} NMR (121.5 MHz, C2D2Cl4, 258C): d ˆ 11.37 (2d,
107
109
107
109
J
ˆ 488,
J
Ag,P
ˆ 565 Hz; 5a), 11.60 (2d,
J
Ag,P
ˆ 483,
J
Ag,P
ˆ
Ag,P
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559 Hz; 5b). Elemental analysis (%): calcd for C76H110O28P2BF4Ag
(1728.30): C 52.82, H 6.41; found: C 53.08, H 6.45; MS (FAB): m/z (%):
[20] Coordinated MeCN molecules could not be differentiated from
uncoordinated ones.
[21] H.-J. Schneider, F. Hacket, V. Rüdiger, Chem. Rev. 1998, 98, 1755 ±
1785.
[22] This includes H-1, H-2, H-4, H-6, OMe-3, and OMe-6 protons.
Molecular models show that coordination of MeCN molecules outside
the cavity would result in strong steric interactions with some of the
OMe-6 and H-6 protons.
[23] Owing to C2 symmetry, the B and C glucose units are equivalent to the
E and F units, respectively.
[24] The whole variable-temperature NMR study required the use of two
distinct solvents, CD2Cl2 ( 40 ± 208C) and C2D2Cl4 (20 ± 1008C). The
coalescence temperature for the two low-energy processes is close to
the boiling point of CD2Cl2 and hence the corresponding activation
barriers could not be determined accurately.
[25] A. Bader, E. Lindner, Coord. Chem. Rev. 1991, 108, 27 ± 110.
[26] R. E. Bachman, D. F. Andretta, Inorg. Chem. 1998, 37, 5657 ± 5663.
[27] M. Camalli, F. Caruso, S. Chaloupka, P. N. Kapoor, P. S. Pregosin,
L. M. Venanzi, Helv. Chim. Acta 1984, 67, 1603 ± 1611.
[28] D. K. Johnson, P. S. Pregosin, L. M. Venanzi, Helv. Chim. Acta 1976,
59, 2691 ± 2703.
‡
‡
1657.4 (60) [M
BF4‡O], 1641.4 (100) [M
BF4].
6: 1H NMR (400.1 MHz, CDCl3/C6H5CN, 258C; assignment by COSY):
d ˆ 2.28, 3.60 (AB, JAB ˆ 10.2 Hz, 4H; H-6B,E C,F), 2.73 (s, 6H; OCH3),
2
or
2.76, 3.30 ± 3.35 (brAB (Â2), 8H; H-6A,D and H-6C,F B,E), 2.93 (s, 6H;
or
OCH3), 2.95 (t, 2H; H-3B,E C,F), 2.95 (t, 2H; H-3C,F or B,E), 3.00 (d, 2H;
or
H-2C,F or B,E), 3.03 (s, 6H; OCH3), 3.05 (d, 2H; H-5C,F or B,E), 3.05 (d, 2H;
H-2B,E or C,F), 3.32 (s, 6H; OCH3), 3.35 (d, 2H; H-2A,D), 3.37 (s, 6H; OCH3),
3.40 (d, 2H; H-5B,E or C,F), 3.50 (s, 6H; OCH3), 3.50 (br, 2H; H-4A,D), 3.52 (s,
6H; OCH3), 3.55 (d, 2H; H-4B,E or C,F), 3.65 (d, 2H; H-4C,F or B,E) 3.70 (s, 6H;
OCH3), 3.75 (t, 2H; H-3A,D), 4.70 (m, 2H; H-5A,D), 4.84 (d, 3JH-2,H-1 ˆ 2.2 Hz,
3
3
2H; H-1C,F or B,E), 4.88 (d, JH-2,H-1 ˆ 2.6 Hz, 2H; H-1A,D), 5.16 (d, JH-2,H-1
ˆ
3.3 Hz, 2H; H-1B,E C,F), 7.35 ± 7.90 (m, 20H, arom. H); 31P{1H} NMR
or
107
109
(121.5 MHz, CDCl3/C6H5CN, 258C): d ˆ 8.7 (2d,
J
Ag,P
ˆ 458,
J
Ag,P
ˆ
‡
529 Hz); MS (ES): m/z (%): 1744.7 (22) [M
BF4].
Crystal structure analysis of 4 ´ H2O ´ 3CH3CN: crystals suitable for X-ray
diffraction were obtained by slow diffusion of diisopropyl ether into a
butanone ± acetonitrile (100:1, v/v) solution of the complex; Mr ˆ 1910.56,
Å
triclinic, space group P1, a ˆ 13.7530(4), b ˆ 14.4944(6), c ˆ 15.0189(6) Š,
Vˆ 2447.8(6) Š3, Z ˆ 1, 1 ˆ 1.30 gcm 3, MoKa radiation (l ˆ 0.71073 Š),
m ˆ 0.321 mm 1. Data were collected on a Kappa CCD Enraf Nonius
system at 173 K. The structure was solved by direct methods and refined on
Fo2 by full-matrix least-squares. All non-hydrogen atoms were refined
anisotropically. The absolute structure was determined by refining Flackꢁs x
parameter. R1 ˆ 0.069 and wR2 ˆ 0.089 for 5753 data with I > 3s(I).
Crystallographic data (excluding structure factors) for the structure
reported in this paper have been deposited with the Cambridge Crystallo-
graphic Data Centre as supplementary publication no. CCDC-157445.
Copies of the data can be obtained free of charge on application to CCDC,
12 Union Road, Cambridge CB21EZ, UK (fax: (‡44)1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk).
[29] Unlike the MeO-2 groups, the MeO-3 protons are known to point
towards the cavity interior. See ref. [21].
Ruthenium Nitrides: Redox Chemistry and
Photolability of the Ru ± Nitrido Group**
Received: February 5, 2001 [Z16553]
Lucia Bonomo, Euro Solari, Rosario Scopelliti, and
Carlo Floriani*
[1] I. Tabushi, Acc. Chem. Res. 1982, 15, 66 ± 72.
[2] Y. Murakami, J.-i. Kikichi, Y. Hisaeda, O. Hayashida, Chem. Rev.
1996, 96, 721 ± 758.
[3] Cyclodextrins: Comprehensive Supramolecular Chemistry, Vol. 3
(Eds.: J. L. Atwood, J. E. D. Davies, D. D. Macnicol, F. Vögtle),
Pergamon, Oxford, 1996.
[4] R. Breslow, S. D. Dong, Chem. Rev. 1998, 98, 1997 ± 2011.
[5] J. F. Stoddart, R. Zarzycki, Recl. Trav. Chim. Pays-Bas 1988, 107 ± 109,
515 ± 528.
[6] E. U. Akkaya, A. W. Czarnik, J. Am. Chem. Soc. 1988, 110, 8553 ±
8554.
[7] R. Breslow, B. Zhang, J. Am. Chem. Soc. 1992, 114, 5882 ± 5883.
[8] M. Sawamura, K. Kitayama, Y. Ito, Tetrahedron: Asymmetry 1993, 4,
1829 ± 1832.
[9] R. Breslow, B. Zhang, J. Am. Chem. Soc. 1994, 116, 7893 ± 7894.
[10] M. Reetz, S. R. Waldvogel, Angew. Chem. 1997, 109, 870 ± 873; Angew.
Chem. Int. Ed. Engl. 1997, 36, 865 ± 867.
[11] M. T. Reetz, Catal. Today 1998, 42, 399 ± 411.
[12] A. R. Renslo, J. Rebek, Jr., Angew. Chem. 2000, 112, 3419 ± 3421;
Angew. Chem. Int. Ed. 2000, 39, 3281 ± 3283.
[13] H. K. A. C. Coolen, P. W. N. M. van Leeuwen, R. J. M. Nolte, Angew.
Chem. 1992, 104, 906 ± 909; Angew. Chem. Int. Ed. Engl. 1992, 31,
905 ± 907.
The metal nitride[1] group plays a key role in nitrogen
transfer to organic[2±4] and inorganic[5] substrates. Such reac-
tivity exists when the nitrido group is associated with a labile
metal, which generally displays catalytic properties. To this
end we considered the ruthenium ion in meso-octamethyl-
porphyrinogen,[6] which is related to porphyrinÐthe macro-
cycle par excellence in ruthenium chemistry. Ruthenium
nitride chemistry[7] has received considerable attention in the
recent past, and some major issues are considered here: 1) the
[7]
ꢀ
formation of the Ru N group by cleavage of N N bonds
which mimic the N2 molecule; 2) the redox chemistry
ꢀ
associated with the [Ru N] fragment, with the intent of
tuning the nucleophilic ± electrophilic properties of the nitrido
group;[7a,b] 3) the relationship between the terminal [Ru N]
ꢀ
ˆ ˆ
and the bridging [Ru N Ru] groups; 4) the photolabilization
of Ru N bonds; and 5) the use of a tetrapyrrolic macrocycle
related to porphyrin, a key ligand in Ru chemistry and one
ꢀ
with which the Ru N group has so far not been associated.
[14] S. Blanchard, L. Le Clainche, M.-N. Rager, B. Chansou, J.-P.
Tuchagues, A. F. Duprat, Y. Le Mest, O. Reinaud, Angew. Chem.
1998, 110, 2861 ± 2864; Angew. Chem. Int. Ed. 1998, 39, 2732 ± 2735.
[*] C. Floriani, L. Bonomo, E. Solari, R. Scopelliti
Â
Á
[15] L. Le Clainche, Y. Rondelez, O. Seneque, S. Blanchard, M. Campion,
M. Giorgi, A. F. Duprat, Y. Le Mest, O. Reinaud, C. R. Acad. Sci. Ser.
IIc 2000, 811 ± 819.
Â
Institut de Chimie Minerale et Analytique
Â
Universite de Lausanne
BCH, 1015 Lausanne (Switzerland)
Fax : (‡41)21-692-3905
[16] J. M. Brown, S. J. Cook, A. G. Kent, Tetrahedron 1986, 42, 5097 ± 5104.
[17] D. Armspach, D. Matt, N. Kyritsakas, Polyhedron 2001, 20, 663 ± 668.
[18] D. A. Armspach, D. Matt, Chem. Commun. 1999, 1073 ± 1074.
[19] Complex 5 crystallized with a water molecule located outside the
cavity. The latter is hydrogen-bonded to the BF4 ion and a MeO-3
oxygen atom. Similar noncovalent aggregates are known to withstand
the conditions used for this ES-MS experiment.
E-mail: carlo.floriani@icma.unil.ch
[**] This work was supported by the ªFonds National Suisse de la
Recherche Scientifiqueº (Grant No. 20-61ꢁ246.00).
Supporting information for this article is available on the WWW under
http://www.angewandte.com or from the author.
Angew. Chem. Int. Ed. 2001, 40, No. 13
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4013-2529 $ 17.50+.50/0
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