COMMUNICATIONS
dimethylcyclohexane and cis-2-heptene, and the significant
from CH
2
Cl
2
/diethyl ether afforded a-1 as large pale yellow blocks (1.19 g,
9
9%). Elemental analysis calcd (%) for C22
28 6 4 6 2
H F FeN O S : C 38.95, H 4.16,
incorporation of O into the alcohol and epoxide products.
2
N 8.26, S 9.45; found: C 38.97, H 4.37, N 8.30, S 9.41.
II
Such catalytic behavior strongly resembles that of [Fe (6-
2
[5±7]
Me -tpa)(CH CN) ] (3).
Perhaps even more compelling
3
3
2
Received: January16, 2002
is the catalysis of cis-dihydroxylation by b-1. Not onlyare the
cis-diol/epoxide ratios increased bysix- to tenfold relative to
those observed for a-1, but the cyclooctene cis-dihydroxyla-
tion product also derives both oxygen atoms from H O , as
Revised: March 19, 2002 [Z18530]
2
2
[1] L. Que, Jr., R. Y. N. Ho, Chem. Rev. 1996, 96, 2607 ± 2624.
[2] E. I. Solomon, T. C. Brunold, M. I. Davis, J. N. Kemsley, S.-K. Lee, N.
reported for 3.[
4, 6]
Lehnert, F. Neese, A. J. Skulan, Y.-S. Yang, J. Zhou, Chem. Rev. 2000,
Our results show that the small change in ligand topology
around the metal center between a-1 and b-1 elicits dramat-
icallydistinct outcomes in the h yd rocarbon oxidation reac-
tions observed for these two isomers, ones that parallel the
contrasting behavior of 2 and 3. The difference between 2 and
1
00, 235 ± 349.
3] C. Kim, K. Chen, J. Kim, L. Que, Jr., J. Am. Chem. Soc. 1997, 119,
964 ± 5965.
[4] K. Chen, L. Que, Jr., Angew. Chem. 1999, 111, 2365–2368; Angew.
Chem. Int. Ed. 1999, 38, 2227 ± 2229.
5] K. Chen, L. Que, Jr., J. Am. Chem. Soc. 2001, 123, 6327 ± 6337.
6] K. Chen, M. Costas, J. Kim, A. K. Tipton, L. Que, Jr., J. Am. Chem.
Soc. 2002, 124, 3026 ± 3035.
[
5
[
[
3
is less subtle; 3 has 6-Me substituents whose steric effects
III
[15]
affect the spin state of the Fe ÀOOH intermediate, which
in turn influences the course of the oxidations (Scheme 2,
[7] K. Chen, M. Costas, L. Que, Jr., J. Chem. Soc. Dalton Trans. 2002,
right branch).[
5±7]
Byanalog ,y we propose that the distinct
672 ± 679.
[
[
8] M. Costas, A. K. Tipton, K. Chen, D.-H. Jo, L. Que, Jr., J. Am. Chem.
Soc. 2001, 123, 6722 ± 6723.
9] J. R. Aldrich-Wright, R. S. Vagg, P. A. Williams, Coord. Chem. Rev.
ligand topologies of a-1 and b-1 give rise to different spin
III
states for their respective Fe ÀOOH intermediates. That the
a-ligand topologyexerts a stronger cr sy tal field is clearly
1
997, 166, 361 ± 389.
1
II
manifested in H NMR experiments on the Fe catalysts in
[10] U. Knof, A. von Zelewsky,Angew. Chem. 1999, 111, 312–333; Angew.
Chem. Int. Ed. 1999, 38, 302 ± 322.
11] C. Ng, M. Sabat, C. L. Fraser, Inorg. Chem. 1999, 38, 5545 ± 5556.
12] M. Costas, J.-U. Rohde, A. Stubna, R. Y. N. Ho, L. Quaroni, E.
M¸nck, L. Que, Jr., J. Am. Chem. Soc. 2001, 123, 12931 ± 12932.
CD CN. While both isomers exhibit large paramagnetic shifts
3
[
[
at 258C indicative of high-spin metal centers (Figure 1), the
a isomer undergoes a transition to a diamagnetic low-spin
form as it is cooled to À458C, indicated bya spectrum that
spans only12 ppm. In contrast, the b isomer remains high spin
at À458C.
[13] K. Chen, L. Que, Jr., Chem. Commun. 1999, 1375 ± 1376.
[14] M. C. White, A. G. Doyle, E. N. Jacobsen, J. Am. Chem. Soc. 2001,
1
23, 7194 ± 7195.
[
15] Y. Zang, J. Kim, Y. Dong, E. C. Wilkinson, E. H. Appelman, L.
In summary, ligand effects appear to play a significant role
in determining the course of hydrocarbon oxidation by
nonheme iron catalysts in combination with H O . One
Que, Jr., J. Am. Chem. Soc. 1997, 119, 4197 ± 4205.
[
16] Y. Mekmouche, S. M e¬ nage, C. Toia-Duboc, M. Fontecave, J.-B. Galey,
C. Lebrun, J. Pecaut, Angew. Chem. 2001, 113, 975–978; Angew.
Chem. Int. Ed. 2001, 40, 949 ± 952.
2
2
important factor is the availabilityof two cis-labile sites as
demonstrated byChen et al. [
5, 6]
in a comparison of related
tetradentate and pentadentate ligands and byMekmouche
et al.[ in a comparison of [Fe(L)X ] (X Cl or CH CN)
16]
2
3
catalysts. We have also shown the dramatic effect of introduc-
ing 6-methyl substituents on pyridine ligands.[ Herein, we
show that the catalytic chemistry can be controlled by ligand
topology. This work demonstrates that exquisite tuning of the
reaction mechanisms can be accomplished bysubtle control of
the coordination environment of the nonheme iron site. Such
fine tuning mayalso serve as a precedent to understand the
diversity on the reactions of hydrocarbon oxidation catalyzed
bynonheme iron enz ym es.
5±7]
Design of a Bilayer Structure in an Organic
Inclusion Compound**
Sang-Ok Lee, Benson M. Kariuki, and
Kenneth D. M. Harris*
[
1, 2]
Since their discoveryover 50 years ago,
several hundreds
of urea inclusion compounds[
3±11]
have been prepared con-
taining different types of guest molecules (mainly based on n-
alkane chains, with onlya limited degree of substitution
Experimental Section
allowed). The vast majorityof urea inclusion compounds are
based on a hexagonal host structure[
3, 12]
that comprises
II
] (b-1) was prepared as previouslydescribed. [8]
3 2
)
b-[Fe (bpmcn)(CF
3
SO
continuous, parallel tunnels constructed from a hydrogen-
bonded arrangement of urea molecules. These ™conventional∫
II
II
a-[Fe (bpmcn)(CF
3
SO
3
)
2
] (a-1) was prepared from a-[Fe (bpmcn)Cl
CN (7 mL) with a
(0.64 g, 5 mmol) in CH CN (3 mL)
CN and
] (1.97 g;
O: C 51.19, H
2
].
Overnight reaction of bpmcn (1.63 g, 5 mmol) in CH
vigorouslystirred suspension of FeCl
afforded a yellow precipitate that was filtered, washed with CH
dried under vacuum to afford the product a-[Fe (bpmcn)Cl
7%). Elemental analysis calcd (%) for C20
.44, N 11.94; found: C 51.38, H 6.20, N 12.21. A suspension of a-
Fe (bpmcn)Cl
with a solution of AgCF
3
2
3
3
II
[*] Prof. Dr K. D. M. Harris, Dr S.-O. Lee, Dr B. M. Kariuki
School of Chemical Sciences
2
8
6
[
H
28Cl
2
FeN
4
¥ H
2
Universityof Birmingham
II
Edgbaston, Birmingham B15 2TT (United Kingdom)
Fax : (44)121-414-7473
2
] (800 mg, 1.78 mmol) in CH
3
CN (5 mL) was then treated
CN (4 mL),
3
SO (912 mg, 3.55 mmol) in CH
3
3
E-mail: K.D.M.Harris@bham.ac.uk
resulting in the formation of a fine precipitate of AgCl, which was filtered
awayafter allowing the mixture to stir. The filtrate was then dried in vacuo,
yielding the desired complex as a pale yellow powder. Recrystallization
[**] We are grateful to the EPSRC, the Universityof Birmingham, and
CVCP for financial support.
Angew. Chem. Int. Ed. 2002, 41, No. 12
¹ WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002
1433-7851/02/4112-2181 $ 20.00+.50/0
2181