5
404
Inorg. Chem. 1998, 37, 5404-5405
Synthesis and Characterization of Molecular Rectangles Based upon Rhenium Thiolate Dimers
Kurt D. Benkstein, Joseph T. Hupp,* and Charlotte L. Stern
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3114
ReceiVed May 6, 1998
There has been substantial recent interest in the construction
and characterization of transition-metal-containing macrocycles;
particularly popular have been tetrametallic “molecular squares,”
i.e., macrocycles featuring cis-coordinated transition-metal corners
and rigid or semirigid difunctional ligand edges. (Other known
Scheme 1
1,2
macrocycles, although not tetrametallic, include triangles and
3
,4 5-13
hexagons. )
Notably, many of the squares have been shown
5-7,9,14
to behave as hosts for small molecule guests
and some have
been shown to function as solution phase sensors.9 In addition,
,14
X-ray crystallographic studies have shown that the compounds
tend to form aligned channel structures.8
,10,11
Exploitation of this
solid-state feature may allow thin films of the squares to be used
for sieving and separations.11
To the best of our knowledge, all tetrametallic macrocycles
15
might display useful alternative redox, optical or molecular charge
characteristics. Previous attempts to synthesize tetrametallic
rectangles from mixtures of singly functional bridging ligands
such as pyrazine (pz) and 4,4′-bipyridine (4,4′-bpy), together with
reported to date have square or near-square cavities. Of particular
interest would be the synthesis of an assembly in which one side
of the cavity is of a significantly different length than the others
a molecular rectangle. In a host/guest or molecular recognition
context, such an arrangement should lead to altered chemical
selectivity and might prove especially useful in achieving selective
binding and/or enhanced binding of planar aromatic guest species.
It should be noted that purely organic cyclophane-type rectangles
have already been reported by several workers, and that binding
5
Re(CO) Cl, exclusively yielded squares rather than mixed bridging
ligand rectangles.1 In this communication we report the synthesis
and characterization of molecular rectangles based upon rhenium-
thiolate dimers.
1
The dimeric complex [(CO)
4
Re(µ-SR)]
synthesized by reaction of HRe(CO)
we have found that it can also be formed by reaction of
Re(CO)
OTf 23 (OTf ) trifluoromethanesulfonate) with various
alkyl and aromatic thiols at room temperature in deoxygenated
CH Cl Purification of a rhenium-propanethiolate dimer by
column chromatography (3:2 hexanes/CH Cl , silica), followed
by reaction with 4,4′-bpy in refluxing CHCl and under flow of
, gave the molecular rectangle 1 as a yellow precipitate in 80%
2
has been known for
some time,2
0-22
with HSR;
of planar aromatic guests has been demonstrated.1
6-19
5
We
reasoned, however, that transition-metal-containing rectangles
5
*
Corresponding author. Fax: (847) 491-7713. E-mail: jthupp@chem.
nwu.edu.
2
2
.
(
(
(
(
1) Fujita, M.; Sasaki, O.; Mitsuhashi, T.; Fujita, T.; Yazaki, J.; Yamaguchi,
K.; Ogura, K. J. Chem. Soc., Chem. Commun. 1996, 1535.
2) Schnebeck, R.-D.; Randaccio, L.; Zangrando, E.; Lippert, B. Angew.
Chem. 1998, 37, 119.
2
2
3
N
2
3) Hall, J. R.; Loeb, S. J.; Shimizu, G. K. H.; Yap, G. P. A. Angew. Chem.
1
998, 37, 121.
4) Lai, S.-W.; Cheung, K.-K. Chan, M. C.-W.; Che, C.-M. Angew. Chem.
998, 37, 182.
yield. Rectangle 2 was prepared analogously to 1 by replacing
4,4′-bpy with pz. Addition of hexanes to the reaction mixture
precipitated the pz-containing product as dark red crystals. The
1
(
(
5) Fujita, M.; Yakazi, J.; Ogura, K. J. Am. Chem. Soc. 1990, 112, 5645.
6) Fujita, M.; Nagao, S.; Iida, M.; Ogata, K.; Ogura, K. J. Am. Chem. Soc.
2
4
synthesis of the rectangles is summarized in Scheme 1.
1
1
993, 115, 1574.
Rectangles 1 and 2 were characterized by H NMR, FAB-MS,
(
(
7) Fujita, M.; Yakazi, J.; Ogura, K. Tetrahedron Lett. 1991, 32, 5589.
8) Stang, P. J.; Olenyuk, B. Acc. Chem. Res. 1997, 30, 502 and references
therein.
9) Slone, R. V.; Yoon, D. I.; Calhoun, R. M.; Hupp, J. T. J. Am. Chem.
Soc. 1995, 117, 11813.
10) Slone, R. V.; Hupp, J. T.; Stern, C. L.; Albrecht-Schmitt, T. E. Inorg.
elemental analysis, UV-vis absorption, FTIR, and X-ray crystal-
lography.2
5,26
No evidence was obtained for luminescence, either
(
in the solid state or in solution.
The infrared absorption spectra for both rectangles show four
bands in the region associated with carbonyl stretches. Only three
(
(
(
(
Chem. 1996, 35, 4096.
11) Slone, R. V.; Benkstein, K. D.; B e´ langer, S.; Hupp, J. T.; Guzei, I. A.;
Rheingold, A. L. Coord. Chem. ReV. 1998, 171, 221.
12) Leung, W.-H.; Cheng, J. Y. K.; Hun, T. S. M.; Che, C.-M.; Wong, W.-
T.; Cheung, K.-K. Organometallics 1996, 15, 1497.
13) For an early report see: Kalb, W. C.; Demidowicz, Z.; Speckmann, D.
M.; Knobler, C.; Teller, R. G.; Hawthorne, M. F. Inorg. Chem. 1982,
(20) Hieber, V. W.; Schuster, L. Z. Anorg. Allg. Chem. 1956, 285, 205.
(21) Osborne, A. G.; Stone, F. G. A. J. Chem. Soc. A 1966, 1143.
(22) Blower, P. J.; Dilworth, J. R. Coord. Chem. ReV. 1987, 76, 121.
(23) Schmidt, S. P.; Nitschke, J.; Trogler, W. C. Inorg. Synth. 1989, 26, 113.
(24) The synthetic scheme was extended to two other rectangles. Rectangle
3 was formed from a benzenethiolate-rhenium dimer and a 4,4′-bpy
bridge. Rectangle 4 used a benzeneselenolate-rhenium dimer and a 4,4′-
2
1, 4027.
(
(
14) Beer, P. D.; J. Chem. Soc., Chem. Commun. 1996, 689.
15) Woessner, S. M.; Helms, J. B.; Shen, Y.; Sullivan, B. P. Inorg. Chem.
1
bpy bridge. These compounds were characterized only by H NMR,
1
998, 37, 5406.
FTIR, and UV-vis absorption methods. (See Supporting Information.)
(
(
(
(
16) Odell, B.; Reddington, M. V.; Slawin, A. M. Z.; Spencer, N.; Stoddart,
J. F.; Williams, D. J. Angew. Chem., Int. Ed. Engl. 1988, 27, 1547.
17) Ashton, P. R.; Odell, B.; Reddington, M. V.; Slawin, A. M. Z.; Stoddart,
J. F.; Williams, D. J. Angew. Chem., Int. Ed. Engl. 1988, 27, 1550.
18) Geuder, W.; H u¨ nig, S.; Suchy, A. Angew. Chem., Int. Ed. Engl. 1983,
(25) 1H NMR spectra for 1 (acetone-d
6
), δ 1.18 (CH
3
-, t, J ) 7.23 Hz, 12H),
S, t, J ) 7.35 Hz, 8H),
, d, J ) 6.78 Hz, 8H); 2 (acetone-
-, t, J ) 7.41 Hz, 12H), 1.73 (-CH -, m, J ) 7.41 Hz,
S, t, J ) 7.35 Hz, 8H), 9.22 (Hpz, s, 8H). Mass spectra
for 1 (LRFAB), 1696.0 calcd, 1696.1 obsd; 2 (LRFAB), 1541.9 calcd,
1.81 (-CH
7.92 (H , d, J ) 6.81 Hz, 8H), 9.15 (H
), δ 1.10 (CH
8H), 3.25 (-CH
2
-, m, J ) 7.35 Hz, 8H), 3.34 (-CH
2
m
o
d
6
3
2
2
2
2, 489.
-
1
19) B u¨ hner, M.; Geuder, W.; Gries, W.-K.; H u¨ nig, S.; Koch, M.; Poll, T.
1542.2 obsd. IR spectra in CH
1919, 1900; 2, 2021, 2013, 1932, 1912 cm
2 2
Cl (CO region, cm ): 1, 2019, 2006,
1
-
Angew. Chem., Int. Ed. Engl. 1988, 27, 1553.
.
1
0.1021/ic980513v CCC: $15.00 © 1998 American Chemical Society
Published on Web 09/24/1998