A rhodium catalyst for single-step styrene production from benzene and ethylene

Article abstract of DOI:10.1126/science.aaa2260

Rising global demand for fossil resources has prompted a renewed interest in catalyst technologies that increase the efficiency of conversion of hydrocarbons from petroleum and natural gas to higher-value materials. Styrene is currently produced from benz

Full text of DOI:10.1126/science.aaa2260

RESEARCH
| REPORTS
2
sphere of radius rcE, P3b = 3/4 (r3b/rcE) ≈ 0.02, or
22. A. Diaferio, M. J. Geller, Astrophys. J. 481, 633–643 (1997).
Life of GAlaxies .”. The project used computational resourses funded
by the M. V. Lomonosov Moscow State University Program of
Development. This research has made use of Aladin developed by the
Centre de Données Astronomiques de Strasbourg;TOPCAT and STILTS
software packages developed by M. Taylor; “exploresdss” script by
G. Mamon; the VizieR catalog access tool, CDS, Strasbourg, France; and
the NASA/IPAC NED, which is operated by the Jet Propulsion
Laboratory, California Institute of Technology, under contract with
NASA. Funding for the SDSS and SDSS-II has been provided by the
Alfred P. Sloan Foundation, the Participating Institutions, the National
Science Foundation, the U.S. Department of Energy, NASA, the
Japanese Monbukagakusho, the Max Planck Society, and the Higher
Education Funding Council for England. The SDSS Web Site is
www.sdss.org. GALEX and SDSS databases used in our study are
available via the CasJobs web-site http://skyserver.sdss.org/CasJobs.
2
2
3. A. Diaferio, Mon. Not. R. Astron. Soc. 309, 610–622 (1999).
4. R. G. Carlberg, H. K. C. Yee, E. Ellingson, Astrophys. J. 478,
~
6 to 8% for three or four merger events.
In our sample of cluster and group cE galaxies,
462–475 (1997).
we indeed see numerous examples in which a cE
resides only 20 to 80 kpc in projection from an
ongoing major merger scene or several other mas-
sive cluster members are visible in the cE vicinity
apart from the massive central cluster/group gal-
axy. Also, there is a known example of a globular
cluster in the Virgo cluster (31) that was likely
ejected at the speed of 2500 km/s and became
gravitationally unbound to the cluster and its cen-
tral galaxy, Messier 87.
We conclude that the tidal stripping process
can explain all observational manifestations of
compact elliptical galaxies, including the forma-
tion of isolated cEs whose existence was suggested
as a strong counter-argument for tidal stripping
25. A. Biviano, M. Girardi, Astrophys. J. 585, 205–214 (2003).
26. J. Pfeffer, H. Baumgardt, Mon. Not. R. Astron. Soc. 433,
997–2005 (2013).
1
2
2
2
7. W. R. Brown, M. J. Geller, S. J. Kenyon, M. J. Kurtz, Astrophys.
J. 622, L33–L36 (2005).
8. L. V. Sales, J. F. Navarro, M. G. Abadi, M. Steinmetz, Mon. Not.
R. Astron. Soc. 379, 1475–1483 (2007).
9. A. R. Wetzel, J. L. Tinker, C. Conroy, F. C. Bosch, Mon. Not. R.
Astron. Soc. 439, 2687–2700 (2014).
3
3
0. G. De Lucia, J. Blaizot, Mon. Not. R. Astron. Soc. 375, 2–14 (2007).
1. N. Caldwell et al., Astrophys. J. 787, L11 (2014).
32. M. Geha, M. R. Blanton, R. Yan, J. L. Tinker, Astrophys. J. 757,
5 (2012).
8
SUPPLEMENTARY MATERIALS
www.sciencemag.org/content/348/6233/418/suppl/DC1
ACKNOWLEDGMENTS
Materials and Methods
Supplementary Text
Figs. S1 to S4
References (33–46)
Table S1
The authors are greatful to F. Combes (Observatoire de Paris),
I. Katkov (Sternberg Astronomical Institute), and M. Kurtz (Smithsonian
Astrophysical Observatory) for useful discussions and critical reading
of the manuscript. This result emerged from the tutorial run by the
authors at the Astronomical Data Analysis Software and Systems
conference in 2012. The authors acknowledge support by the Russian
Science Foundation project 14-22-00041 “VOLGA—A View On the
(
9). The ejection of cEs from central regions of
galaxy clusters by three-body encounters is a chan-
nel for these galaxies to survive for an extended
period of time in the violent cluster environment,
where they would otherwise be accreted by mas-
sive hosts on a time scale of 2 billion to 3 billion
years. The 11 isolated cEs probably represent a
population of runaway galaxies that received suf-
ficient kick velocities to leave their host clusters
or groups forever.
The gravitational ejection mechanism may also
explain the very existance of extremely rare iso-
lated quiescent dwarf galaxies (32), where the star
formation quenching is usually explained by envi-
19 November 2014; accepted 20 March 2015
10.1126/science.aaa3344
ORGANIC CHEMISTRY
A rhodium catalyst for single-step
styrene production from benzene
ronmental effects. These systems are more spatially and ethylene
extended than cEs and do not exhibit substantial
tidal stripping footprints. This suggests that they
never came very close to cluster/group centers,
and therefore, the three-body encounter proba-
bility for them should be lower than that for cEs,
although still nonnegligible.
1
1
2
1
Benjamin A. Vaughan, Michael S. Webster-Gardiner, Thomas R. Cundari, * T. Brent Gunnoe *
Rising global demand for fossil resources has prompted a renewed interest in catalyst
technologies that increase the efficiency of conversion of hydrocarbons from petroleum and
natural gas to higher-value materials. Styrene is currently produced from benzene and
ethylene through the intermediacy of ethylbenzene, which must be dehydrogenated in a
separate step.The direct oxidative conversion of benzene and ethylene to styrene could provide
a more efficient route, but achieving high selectivity and yield for this reaction has been
REFERENCES AND NOTES
1.
S. D. M. White, C. S. Frenk, Astrophys. J. 379, 52 (1991).
S. Cole, C. G. Lacey, C. M. Baugh, C. S. Frenk, Mon. Not. R.
Astron. Soc. 319, 168–204 (2000).
M. J. Drinkwater et al., Nature 423, 519–521 (2003).
J. Price et al., Mon. Not. R. Astron. Soc. 397, 1816–1835 (2009).
I. Chilingarian et al., Science 326, 1379–1382 (2009).
I. V. Chilingarian, G. Bergond, Mon. Not. R. Astron. Soc. 405,
L11–L15 (2010).
2.
Fl
2
Fl
2 4
challenging. Here, we report that the Rh catalyst ( DAB)Rh(TFA)(h –C H ) [ DAB is N,N′-
3.
bis(pentafluorophenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene; TFA is trifluoroacetate] converts
benzene, ethylene, and Cu(II) acetate to styrene, Cu(I) acetate, and acetic acid with 100%
selectivity and yields ≥95%. Turnover numbers >800 have been demonstrated, with catalyst
stability up to 96 hours.
4.
5.
6.
7.
M. A. Norris et al., Mon. Not. R. Astron. Soc. 443, 1151–1172 (2014).
A. P. Huxor, S. Phillipps, J. Price, R. Harniman, Mon. Not. R.
Astron. Soc. 414, 3557–3565 (2011).
8.
inyl arenes are important precursors for
fine chemical synthesis, as well as for the
preparation of plastics and elastomers
product (polyalkylation is inherent to the mech-
anism), and the generation of stoichiometric
waste (2). Zeolite catalysts have improved the
process for benzene alkylation, yet these cat-
alysts still require high temperatures (generally
350° to 450°C) and give polyalkylated products
(2, 7–10).
An alternative method for the production of
vinyl arenes is a direct and single-step oxidative
arene vinylation (Fig. 1). If the terminal oxidant
is oxygen from air (either introduced in situ or
used to recycle a different in situ oxidant), the net
reaction is the conversion of benzene, ethylene,
and oxidant to styrene and water (11). Acid-based
(i.e., Friedel-Crafts or zeolite catalysts) catalysis
occurs by electrophilic aromatic substitution and
does not offer a viable pathway to directly gen-
erate vinyl arenes. Transition metal complexes
that catalyze ethylene hydrophenylation by benzene
9.
A. P. Huxor, S. Phillipps, J. Price, Mon. Not. R. Astron. Soc. 430,
1956–1960 (2013).
1
0. S. Paudel, T. Lisker, K. S. A. Hansson, A. P. Huxor, Mon. Not. R.
(
1–5). For example, styrene is produced
Astron. Soc. 443, 446–453 (2014).
V
globally on a scale of ~18.5 million tons (2).
1
1
1. R. M. Rich et al., Nature 482, 192–194 (2012).
2. N. C. Amorisco, N. W. Evans, G. van de Ven, Nature 507,
Current methods for the large-scale production
of vinyl arenes involve multiple steps, typically
beginning with arene alkylation using a Friedel-
335–337 (2014).
1
3. O. Fakhouri, C.-P. Ma, M. Boylan-Kolchin, Mon. Not. R. Astron.
Soc. 406, 2267–2278 (2010).
3
Crafts (e.g., AlCl with HF) or zeolite catalyst
1
4. I. V. Chilingarian, I. Y. Zolotukhin, Mon. Not. R. Astron. Soc. 419,
followed by energy-intensive dehydrogenation
of the alkyl group (Fig. 1) (1–6). Friedel-Crafts ca-
talysis suffers from the use of harsh acids, includ-
ing HF, low selectivity for the monoalkylated
1727–1739 (2012).
1
1
1
5. K. N. Abazajian et al., J. Suppl. Ser. 182, 543–558 (2009).
6. D. C. Martin et al., Astrophys. J. 619, L1–L6 (2005).
7. I. Chilingarian, P. Prugniel, O. Sil'chenko, M. Koleva, Stellar
Populations as Building Blocks of Galaxies, A. Vazdekis,
R. R. Peletier, Eds. (Cambridge Univ. Press, Cambridge, UK,
1
2
007), vol. 241 of IAU Symposium, pp. 175–176, arXiv:0709.3047.
Department of Chemistry, University of Virginia,
2
1
1
8. L. Spitzer, Astrophys. J. 158, L139 (1969).
9. L. Hernquist, Astrophys. J. 356, 359 (1990).
Charlottesville, VA 22903, USA. Center for Advanced
Scientific Computing and Modeling, Department of Chemistry,
University of North Texas, Denton, TX 76203, USA.
*Corresponding author. E-mail: tbg7h@virginia.edu (T.B.G.),
t@unt.edu (T.R.C.)
2
0. E. Tempel, E. Tago, L. J. Liivamägi, Astron. Astrophys. 540, A106
2012).
1. N. Kaiser, Mon. Not. R. Astron. Soc. 227, 1–21 (1987).
(
2
SCIENCE sciencemag.org
24 APRIL 2015 • VOL 348 ISSUE 6233 421

RESEARCH
| REPORTS
C–H activation followed by ethylene insertion into
a metal-phenyl bond have been reported as alter-
natives to acid-based catalysts (Fig. 2) (12–25).
For these catalysts, b-hydride elimination from a
of styrene leads to catalyst decomposition (27).
We proposed that this catalyst decomposition is
the result of unstable Pt(II)–hydride complexes,
which are formed from b-hydride elimination,
duce styrene. Despite precedent for the key steps
in this catalytic cycle, designing a selective cata-
lyst represents a substantial challenge because
many competing side reactions (shown in red)
are likely to have activation barriers that are
similar to or lower than those of the reactions
along the desired catalytic cycle. In addition to
these possible side reactions, designing a molec-
ular catalyst that achieves high turnover numbers
(TONs) is difficult because the oxidative condi-
tions and the presence of potentially reactive
metal-hydride intermediates could be anticipated
to result in catalyst decomposition.
Table 1 compares previously reported homo-
geneous catalysts for direct oxidative styrene syn-
thesis from ethylene and benzene (29–34). Generally,
all suffer from one or more of the following draw-
backs: low selectivity, low yield, low TON, and/or
use of oxidants that cannot be regenerated using
oxygen. Notable results include the work of Hong
2 2
M–CH CH Ph intermediate and dissociation of
2
that react to release H and produce metallic Pt.
styrene provides a route for the direct oxidative
vinylation of benzene (Fig. 2).
The thermodynamic driving force for the forma-
tion of Pt(s) presents a substantial challenge to
achieving long-lived vinyl arene production with
these catalysts (Fig. 2, inset) (11). Given that the
formation and decomposition of Pt(II)–H species
is problematic, we sought to design catalysts using
isoelectronic Rh(I) in anticipation that Rh(I)–
H would exhibit greater stability compared with
related Pt species (Fig. 2, inset) (11).
Previously, our groups have studied the use of
platinum(II) catalysts for the hydrophenylation
of ethylene to produce ethylbenzene (16–19, 26–28).
Through a combination of experimental and com-
putational mechanistic studies, we discerned a
competing b-hydride elimination pathway from
Pt–CH
2
CH
2
Ph intermediates to form a Pt–styrene
hydride complex, which can lead to the formation
of free styrene (28). Unfortunately, the formation
Figure 2 shows a targeted catalytic cycle for
the direct oxidative vinylation of benzene to pro-
4
and co-workers, who reported a Rh (CO)12 cata-
lyst that gave, to our knowledge, the highest TON
of styrene (472). In tandem with this process,
liberated dihydrogen is consumed by two equiv-
alents of ethylene and one equivalent of CO to
produce 3-pentanone with 809 turnovers (TOs)
Fig. 1. Comparison of
the current route to
styrene production and
the single-step route
described herein.
(
29). Sanford and co-workers reported that (3,5-
dichloropyridyl)Pd(OAc) catalyzes styrene pro-
duction with 100% selectivity and 6.6 TOs for
2
t
3
styrene (33% overall yield) using PhCO Bu, an
oxidant that cannot be recycled with oxygen (33).
Here, we report a rhodium catalyst for the selec-
tive one-step production of styrene from benzene,
ethylene, and Cu(II) salts. We chose a Cu(II) salt
as the in situ oxidant because of industrial prec-
edent for recycling reduced Cu(I) using oxygen.
In the commercial Wacker-Hoechst process for
2
Fig. 2. Proposed cycle for transition metal–catalyzed styrene production from benzene and ethylene using CuX as an oxidant. The cuprous (CuX)
product could be recycled back to the cupric state using air, as shown at the upper left. Potential side reactions that a selective catalyst must avoid are shown
in red.
4
22 24 APRIL 2015 • VOL 348 ISSUE 6233
sciencemag.org SCIENCE

RESEARCH
| REPORTS
ethylene oxidation (35, 36), use of oxygen to re-
oxidize Cu(I) to Cu(II) has proven viable both in
situ and in a second step (37).
C–H activation is a key step in transition metal–
catalyzed oxidative arene vinylation, we hypothe-
sized that this Rh(I) complex might be an effective
catalyst precursor for styrene production. Because
the COE ligand would likely exchange for ethyl-
ene, the ethylene analog ( DAB)Rh(TFA)(h -C H )
2 4
(1) was independently synthesized as our catalyst
precursor (Fig. 3).
2
ethylene and Cu(OAc) (120 equivalents relative
to 1) to 150°C affords 58 to 62 TOs of styrene after
24 hours (for all TOs reported, two runs were
performed, and both results are given). Samples
of the reaction mixture were analyzed by gas
chromatography–flame ionization detector (GC/
FID) using relative peak areas versus an internal
standard (decane). This corresponds to quantitative
yield based on the Cu(II) limiting reagent. The
calculated yield here assumes that two equiv-
alents of Cu(II) are consumed to produce two
equivalents of Cu(I) per equivalent of styrene. No
other products were observed upon analysis of
the reaction mixture by GC–mass spectrometry
or GC/FID, indicating high selectivity for styrene
production. Detection limits for the instruments
were equivalent to ~1 TO of product. Specifically, we
looked for evidence of stilbene, biphenyl, and vinyl
acetate production, because these are the most
commonly observed by-products in previously re-
We recently reported the synthesis of an electron-
Fl
2
deficient Rh(I) complex ( DAB)Rh(TFA)(h -COE)
[
1
Fl
Fl
2
DAB is N,N′-bis(pentafluorophenyl)-2,3-dimethyl-
,4-diaza-1,3-butadiene; TFA is trifluoroacetate;
COE is cyclooctene] and demonstrated that this
complex is an active catalyst for arene H/D ex-
change in trifluoroacetic acid (38). Given that arene
Heating a 20-mL benzene solution of 1 [0.001
mole percent (mol %) relative to benzene] with
Table 1. Comparison of previously reported catalysts for styrene production. Selectivity is defined
as the ratio of turnovers of styrene to total turnovers (all products) and is given as a percentage. Yield of
styrene is reported relative to the limiting reagent. acac, acetylacetonate; DBM, dibenzoylmethane; DCP,
3
,5-dichloropyridine; HPA, H
3 2
PMo12O40 · 30H O; TFA, trifluoroacetate.
Catalyst
Rh (CO)12 (29)
acac) Rh(Cl)(H
Rh(PMe
Oxidant
/CO
TON
Selectivity (%)
Yield (%)
4
C
2
H
4
472
24
3
0.59
19
37
89
38
44
29
19
36
18
12
5
(
2
2
O) (30)
(CO)(Cl) (34)
Cu(OAc)
hn
2
)
3 2
ported catalysis (Table 1). Control reactions with
2
Pd(OAc)
Pd(OAc)
2
(31)
(30)
AgOAc
Cu(OAc)
[
Rh(m-TFA)(h -C
2
H
4
)
2
]
2
, a precursor to complex 1,
2
2
/O
2
afforded <5 TOs of styrene after 24 hours, with or
without Cu(OAc) , highlighting the importance of
the DAB ligand. Control reactions with Cu(OAc)
alone also afforded no styrene formation.
(
(
(
(
DBM)Pd(OAc)
2
(32)
(33)
HPA
PhCO
Cu(OAc)
Cu(OAc)
100
6.6
115
835
58
2
2
t
Fl
3,5-DCP)Pd(OAc)
2
3
Bu
100
100
100
33
96
70
2
Fl
DAB)Rh(TFA)(C
DAB)Rh(TFA)(C
2
H
4
)
)
2
Fl
2
H
4
2
With a competent catalyst in hand, we next
sought to optimize reaction conditions. The ef-
fect of oxidant identity on catalysis with 1 was
the first parameter investigated. Both soluble
{
copper 2-ethylhexanoate [Cu(OHex)
per pivalate [Cu(OPiv) ]} and insoluble {copper
acetate [Cu(OAc) ] and copper trifluoroacetate
hydrate [Cu(TFA) ]} Cu(II) salts were screened.
2
] and cop-
2
2
2
Figure S2 shows a plot of turnovers versus time
for the various Cu(II) oxidants. Using a turnover
frequency (TOF) calculated after 4 hours of re-
2
action, soluble Cu(OHex) gives the fastest initial
−3 –1
rate with a TOF of 2.8 × 10 s , but the reaction
does not reach 100% yield relative to oxidant
until 28 hours, which may indicate that catalyst
deactivation occurs. Cu(OAc)
initial rate than Cu(OHex) , with a TOF of 2.8 ×
after 4 hours, but this oxidant provides a
more stable catalytic process. Both Cu(TFA) and
Cu(OPiv) afford slower initial rates; reactions
with Cu(OPiv) reach 92% yield after 28 hours,
whereas reactions with Cu(TFA) produce only
9 TOs of styrene (32% yield) after 20 hours.
To study catalyst longevity, we varied the amount
of Cu(OAc) . Between 60 and 240 equivalents
relative to 1), the yield of styrene relative to
2
affords a slower
2
−
4 –1
1
0
s
2
2
2
2
1
Fl
2
Fig. 3. Synthesis of ( DAB)Rh(TFA)(h -C
2
H
4
) (1) (RT, room temperature).
2
(
Fig. 4. Effect of ethylene
pressure on catalysis with
H ) (1).
2 4
Reaction conditions: 0.001 mol %
, 120 equivalents Cu(OAc)
50°C, 4 hours. Data for two
oxidant was always >95% (fig. S3). These near-
quantitative yields demonstrate that the catalytic
process using 1 as a precursor is stable and long-
lived. For a reaction using 0.0001 mol % 1 and
Fl
2
(
DAB)Rh(TFA)(h -C
1
2
,
2
2400 equivalents of Cu(OAc) , the catalyst remained
1
active over a period of 96 hours and afforded a
TON of 817 to 852. A plot of TO versus time shows
that the Rh catalyst is stable through at least 96
hours (fig. S1). The tolerance of 1 to a large excess of
oxidant without any decrease in activity is promis-
ing. The effect of temperature on catalysis was also
examined (fig. S4). Generally, the rate of reaction
increased with temperature; however, at 180°C,
rapid catalyst deactivation led to a low TON (<10
TOs) after 12 hours. Minimal activity (<1 TO) was
independent reactions are shown.
SCIENCE sciencemag.org
24 APRIL 2015 • VOL 348 ISSUE 6233 423

RESEARCH
| REPORTS
also observed at temperatures <100°C. The opti-
mal temperature proved to be 150°C.
production of vinyl-aromatic monomers” (International Patent
WO2007073918A1, 2007).
C. Perego, P. Ingallina, Catal. Today 73, 3–22 (2002).
. C. Perego, P. Ingallina, Green Chem. 6, 274 (2004).
9. J. Čejka, B. Wichterlová, Catal. Rev. 44, 375–421 (2002).
31. Y. Fujiwara, I. Noritani, S. Danno, R. Asano, S. Teranishi,
J. Am. Chem. Soc. 91, 7166–7169 (1969).
32. T. Yamada, A. Sakakura, S. Sakaguchi, Y. Obora, Y. Ishii,
New J. Chem. 32, 738 (2008).
7
8
.
We also observed that the reaction rate in-
creased with increasing ethylene pressure. To de-
termine the TOF, we measured TO after 4 hours
of reaction. Figure 4 shows a plot of TOF versus
ethylene pressure. A linear correlation is observed.
Thus, the reaction rate appears to have a first-
order dependence on ethylene concentration. This
is in contrast to previously reported Pt(II) and
Ru(II) catalysts for the hydrophenylation of eth-
ylene, which show an inverse dependence on
33. A. Kubota, M. H. Emmert, M. S. Sanford, Org. Lett. 14,
1
0. I. M. Gerzeliev, S. N. Khadzhiev, I. E. Sakharova, Petrol. Chem.
1760–1763 (2012).
34. K. Sasaki, T. Sakakura, Y. Tokunaga, K. Wada, M. Tanaka,
Chem. Lett. 17, 685–688 (1988).
51, 39–48 (2011).
1
1. CRC Handbook of Chemistry and Physics (CRC Press,
Boca Raton, FL, 1977).
3
5. American Chemical Society, Chem. Eng. News Archive 39 (16),
2–55 (1961).
12. M. Lail, B. N. Arrowood, T. B. Gunnoe, J. Am. Chem. Soc. 125,
506–7507 (2003).
3. M. Lail et al., Organometallics 23, 5007–5020 (2004).
4. N. A. Foley, J. P. Lee, Z. Ke, T. B. Gunnoe, T. R. Cundari,
5
7
3
6. W. A. Herrmann, in Catalysis from A to Z, B. Cornils, W. A. Herrmann,
M. Muhler, C.-H. Wong, Eds. (Wiley, Weinheim, Germany, 2007),
pp. 1512–1524.
1
1
Acc. Chem. Res. 42, 585–597 (2009).
15. E. E. Joslin et al., Organometallics 31, 6851–6860 (2012).
3
7. M. Eckert, G. Fleischmann, R. Jira, H. M. Bolt, K. Golka, in
Ullmann’s Encyclopedia of Industrial Chemistry (Wiley-VCH
Verlag, Weinheim, Germany, 2000), pp. 1–17.
1
6. J. R. Andreatta, B. A. McKeown, T. B. Gunnoe, J. Organomet. Chem.
96, 305–315 (2011).
7. B. A. McKeown et al., J. Am. Chem. Soc. 133, 19131–19152 (2011).
ethylene pressure (14, 17). For the Pt and Ru cat-
6
2
alysts, M(CH
2
CH
2
Ph)(h -C
2 4
H ) complexes were
38. M. S. Webster-Gardiner et al., Cat. Sci. Tech. 5, 96–100 (2015).
1
3
4
9. M. Gómez-Gallego, M. A. Sierra, Chem. Rev. 111, 4857–4963 (2011).
0. W. D. Jones, Acc. Chem. Res. 36, 140–146 (2003).
identified as the likely catalyst resting states.
The opposite dependence on ethylene pressure
using 1 as catalyst precursor signals a likely change
in the catalyst resting state.
To gain further insight into the reaction mech-
anism, we ran the reaction in a 1:1 molar mixture
18. B. A. McKeown, H. E. Gonzalez, T. B. Gunnoe, T. R. Cundari,
M. Sabat, ACS Catal. 3, 1165–1171 (2013).
9. B. A. McKeown, B. M. Prince, Z. Ramiro, T. B. Gunnoe,
T. R. Cundari, ACS Catal. 4, 1607–1615 (2014).
0. S. A. Burgess et al., Chem. Sci. 5, 4355–4366 (2014).
21. W. D. Jones, J. A. Maguire, G. P. Rosini, Inorg. Chim. Acta 270,
77–86 (1998).
1
ACKNOWLEDGMENTS
2
The authors acknowledge support from the U.S. Department of
Energy, Office of Basic Energy Sciences [DE-SC0000776 (T.B.G.)
and DE-FG02-03ER15387 (T.R.C.)] for studies of styrene catalysis;
the Center for Catalytic Hydrocarbon Functionalization, an Energy
Frontier Research Center (award DE-SC0001298), which funded
the initial catalyst discovery; and an AES Corporation Graduate
Fellowship in Energy Research (M.S.W.-G). The authors also thank
B. McKeown, G. Fortman, S. Kalman (University of Virginia), and
R. Nielsen (California Institute of Technology) for helpful discussions.
2
2. A. T. Luedtke, K. I. Goldberg, Angew. Chem. Int. Ed. 47,
694–7696 (2008).
6 6 6 6 H D
of C H and C D . After 1 hour, a k /k (ratio of
7
rate of reaction of protio-benzene and perdeutero-
benzene) of 3.1(2) was determined by exam-
ining the ratio of undeuterated styrene [mass/
2
3. T. Matsumoto, D. J. Taube, R. A. Periana, H. Taube, H. Yoshida,
J. Am. Chem. Soc. 122, 7414–7415 (2000).
24. T. Matsumoto, R. A. Periana, D. J. Taube, H. Yoshida,
J. Mol. Catal. A 180, 1–18 (2002).
5
charge ratio (m/z) = 104] to styrene-d (m/z = 109)
2
5. J. Oxgaard, R. P. Muller, W. A. Goddard 3rd, R. A. Periana,
in the mass spectra from three independent ex-
periments (fig. S5). After 2 hours, the observed
isotope effect was 3.0(2), statistically equivalent
to the data at 1 hour (fig. S5). Thus, the observed
J. Am. Chem. Soc. 126, 352–363 (2004).
26. B. A. McKeown, N. A. Foley, J. P. Lee, T. B. Gunnoe,
Organometallics 27, 4031–4033 (2008).
7. B. A. McKeown et al., Organometallics 32, 3903–3913 (2013).
8. B. A. McKeown et al., Organometallics 32, 2857–2865 (2013).
9. P. Hong, H. Yamazaki, J. Mol. Catal. 26, 297–311 (1984).
30. D. Taube, R. Periana, T. Matsumoto, “Oxidative coupling
of olefins and aromatics using a rhodium catalyst and a
copper(II) redox agent” (U.S. Patent 6127590A, 2000).
SUPPLEMENTARY MATERIALS
www.sciencemag.org/content/348/6233/421/suppl/DC1
Materials and Methods
Figs. S1 to S4
Table S1
References (41–43)
2
2
2
H D
k /k of ~3.1 likely reflects a kinetic isotope ef-
fect (KIE) for the catalytic cycle. The KIE is con-
sistent with other transition metal–mediated C–H
activation reactions. (39, 40) The primary KIE
supports the hypothesis that a Rh catalyst is
facilitating a metal-mediated C–H activation
process, which occurs before or during the turnover-
limiting step. No change in the isotopic distribu-
tion for benzene was observed over the course
of the reaction, and no styrene-d6-8 products were
observed except those predicted by the natural
abundance of deuterium in ethylene.
3 November 2014; accepted 12 March 2015
10.1126/science.aaa2260
SELF-ASSEMBLY
Selective assemblies of giant
Although more detailed studies are required tetrahedra via precisely controlled
to understand the reactivity profile of 1, we be-
lieve that the highly electron-withdrawing per-
positional interactions
Fl
fluorophenyl groups on the DAB ligand help
suppress irreversible oxidation to inactive Rh(III)
1
1
1
1
1
1
Mingjun Huang, Chih-Hao Hsu, Jing Wang, Shan Mei, Xuehui Dong, Yiwen Li,
in the presence of Cu(II), possibly facilitate asso-
ciative ligand exchange between free ethylene
and coordinated styrene, and facilitate rapid eth-
ylene insertion into Rh–Ph bonds. Challenges
that remain for the continued development of
this class of catalyst include increasing activity
with the aim of achieving higher conversions
of benzene.
1
1
1
2
3
Mingxuan Li, Hao Liu, Wei Zhang, Takuzo Aida, Wen-Bin Zhang, *
1
1
Kan Yue, * Stephen Z. D. Cheng *
Self-assembly of rigid building blocks with explicit shape and symmetry is substantially
influenced by the geometric factors and remains largely unexplored. We report the selective
assembly behaviors of a class of precisely defined, nanosized giant tetrahedra constructed by
placing different polyhedral oligomeric silsesquioxane (POSS) molecular nanoparticles at the
vertices of a rigid tetrahedral framework. Designed symmetry breaking of these giant
tetrahedra introduces precise positional interactions and results in diverse selectively
assembled, highly ordered supramolecular lattices including a Frank-Kasper A15 phase, which
resembles the essential structural features of certain metal alloys but at a larger length scale.
These results demonstrate the power of persistent molecular geometry with balanced
enthalpy and entropy in creating thermodynamically stable supramolecular lattices with
properties distinct from those of other self-assembling soft materials.
REFERENCES AND NOTES
1.
G. A. Olah, Á. Molnár, Hydrocarbon Chemistry (Wiley, Hoboken,
NJ, ed. 2, 2003).
2
.
.
C. Perego, P. Pollesel, in Advances in Nanoporous Materials,
E. Stefan, Ed. (Elsevier, Oxford, 2010), vol. 1, pp. 97–149.
S.-S. Chen, in Kirk-Othmer Encyclopedia of Chemical
Technology, A. Seidel, M. Bickford, Eds. (Wiley, Hoboken, NJ,
3
2000), pp. 325–357.
4
.
H. A. Wittcoff, B. G. Reuben, J. S. Plotkin, in Industrial
Organic Chemicals (Wiley, Hoboken, NJ, 2004), pp. 100–166.
Process Evaluation/Research Planning (PERP) Program
Report, Styrene/Ethylbenzene, (PERP Report 91-9, Chem
Systems, Inc., New York, 1992).
elf-assembled hierarchical structures in
soft materials have been intensely studied.
Among them, assemblies of building blocks
with specific geometric shapes and sym-
metry are of particular interest. As the sim-
plest case, ordered structures constructed from
packing of spherical motifs have been a classic yet
dynamic research field that can be traced back to
the study of metals and metal alloys. Most metal
atoms, viewed as congruent spheres, typically tend
5.
6.
M. Lucchini, A. Galeotti, “Improved process for the
dehydrogenation of alkyl-aromatic hydrocarbons for the
S
4
24 24 APRIL 2015 • VOL 348 ISSUE 6233
sciencemag.org SCIENCE

A rhodium catalyst for single-step styrene production from benzene
and ethylene
Benjamin A. Vaughan et al.
Science 348, 421 (2015);
DOI: 10.1126/science.aaa2260
This copy is for your personal, non-commercial use only.
If you wish to distribute this article to others, you can order high-quality copies for your
colleagues, clients, or customers by clicking here.
Permission to republish or repurpose articles or portions of articles can be obtained by
following the guidelines here.
The following resources related to this article are available online at
www.sciencemag.org (this information is current as of April 23, 2015 ):
Updated information and services, including high-resolution figures, can be found in the online
version of this article at:
http://www.sciencemag.org/content/348/6233/421.full.html
Supporting Online Material can be found at:
http://www.sciencemag.org/content/suppl/2015/04/22/348.6233.421.DC1.html
This article appears in the following subject collections:
Chemistry
http://www.sciencemag.org/cgi/collection/chemistry
Science (print ISSN 0036-8075; online ISSN 1095-9203) is published weekly, except the last week in December, by the
American Association for the Advancement of Science, 1200 New York Avenue NW, Washington, DC 20005. Copyright
2
015 by the American Association for the Advancement of Science; all rights reserved. The title Science is a
registered trademark of AAAS.