Transition metal catalysis in fluorous media: Practical application of a new immobilization principle to rhodium-catalyzed hydroborations of alkenes and alkynes

Article abstract of DOI:10.1021/ja982955b

Addition of a yellow-orange toluene solution of [Rh(C1)(COD)]₂ to a colorless CF₃C₆F₁₁ solution of P(CH₂CH₂R(f6))₃ (R(f6) = (CF₂)₅CF₃)₃) gives a colorless toluene solution of COD and an orange CF₃C₆F₁₁ solution of ClRh[P(CH₂CH₂R(f6))₃]₃ (1). Evaporation of CF₃C₆F₁₁ gives analytically pure 1 (94%), which is insoluble in most organic solvents and stable to 300 °C. Alkenes, catecholborane, and CF₃C₆F₁₁ solutions of 1 (950:950:1 mol ratio for norbomene) are stirred for 1-24 h at 40 °C (heterogeneous conditions). The resulting alkylboranes are extracted with benzene (2x; turnover number (TON) 854 (90%) for norbornene), toluene, or THF, and the catalyst solution is reused (TON 2409 for three cycles). Subsequent reactions with H₂0₂/NaOH give alcohols, which are isolated in 92-77% yields (11 examples). Longer reaction times afford TON values higher than 10000 (<0.1 mol % 1). Analogous reactions of alkynes yield alkenylboranes (89-88%). Pinacolborane additions are also catalyzed. A higher homologue of 1, ClRh[P(CH₂CH₂R(f8))₃]₃ (2), and the nonfluorinated analogue ClRh[P((CH₂)₇CH₃)₃]₃ are similarly prepared. Solubilities and reactivities are compared. Atomic absorption analyses shows rhodium losses of 0.4% (1) and 0.2% (2) per cycle, corresponding to 4.52.2 ppm rhodium/mol of addition product. These data demonstrate the viability and practicality of an exciting new approach to catalyst immobilization. Addition of a yellow-orange toluene solution of [Rh(Cl)(COD)]₂ to a colorless CF₃C₆F₁₁ solution of P(CH₂CH₂R_f6)₃ (R_f6 = (CF₂)₅CF₃)₃) gives a colorless toluene solution of COD and an orange CF₃C₆F₁₁ solution of ClRh[P(CH₂CH₂R_f6)₃]₃ (1). Evaporation of CF₃C₆F₁₁ gives analytically pure 1 (94%), which is insoluble in most organic solvents and stable to 300 °C. Alkenes, catecholborane, and CF₃C₆F₁₁ solutions of 1 (950:950:1 mol ratio for norbornene) are stirred for 1-24 h at 40 °C (heterogeneous conditions). The resulting alkylboranes are extracted with benzene (2×; turnover number (TON) 854 (90%) for norbornene), toluene, or THF, and the catalyst solution is reused (TON 2409 for three cycles). Subsequent reactions with H₂O₂/NaOH give alcohols, which are isolated in 92-77% yields (11 examples). Longer reaction times afford TON values higher than 10000 (<0.1 mol % 1). Analogous reactions of alkynes yield alkenylboranes (89-88%). Pinacolborane additions are also catalyzed. A higher homologue of 1, ClRh[P(CH₂CH₂R_f8)₃]₃ (2), and the nonfluorinated analogue ClRh[P((CH₂)₇CH₃)₃]₃ are similarly prepared. Solubilities and reactivities are compared. Atomic absorption analyses shows rhodium losses of 0.4% (1) and 0.2% (2) per cycle, corresponding to 4.5-2.2 ppm rhodium/mol of addition product. These data demonstrate the viability and practicality of an exciting new approach to catalyst immobilization.

Full text of DOI:10.1021/ja982955b

2696
J. Am. Chem. Soc. 1999, 121, 2696-2704
Transition Metal Catalysis in Fluorous Media: Practical Application
of a New Immobilization Principle to Rhodium-Catalyzed
Hydroborations of Alkenes and Alkynes
Jerrick J. J. Juliette,1a Drew Rutherford,1a,b Istva´n T. Horva´th,*,1c and J. A. Gladysz*,1a,d
Contribution from the Department of Chemistry, UniVersity of Utah, Salt Lake City, Utah 84112,
Corporate Research Laboratories, Exxon Research and Engineering Co., Annandale, New Jersey 08801,
and Institut fu¨r Organische Chemie, Friedrich-Alexander UniVersita¨t Erlangen-Nu¨rnberg, Henkestrasse 42,
D-91054 Erlangen, Germany
ReceiVed August 17, 1998
Abstract: Addition of a yellow-orange toluene solution of [Rh(Cl)(COD)]2 to a colorless CF3C6F11 solution
of P(CH2CH2Rf6)3 (Rf6 ) (CF2)5CF3)3) gives a colorless toluene solution of COD and an orange CF3C6F11
solution of ClRh[P(CH2CH2Rf6)3]3 (1). Evaporation of CF3C6F11 gives analytically pure 1 (94%), which is
insoluble in most organic solvents and stable to 300 °C. Alkenes, catecholborane, and CF3C6F11 solutions of
1 (950:950:1 mol ratio for norbornene) are stirred for 1-24 h at 40 °C (heterogeneous conditions). The resulting
alkylboranes are extracted with benzene (2×; turnover number (TON) 854 (90%) for norbornene), toluene, or
THF, and the catalyst solution is reused (TON 2409 for three cycles). Subsequent reactions with H2O2/NaOH
give alcohols, which are isolated in 92-77% yields (11 examples). Longer reaction times afford TON values
higher than 10 000 (<0.1 mol % 1). Analogous reactions of alkynes yield alkenylboranes (89-88%).
Pinacolborane additions are also catalyzed. A higher homologue of 1, ClRh[P(CH2CH2Rf8)3]3 (2), and the
nonfluorinated analogue ClRh[P((CH2)7CH3)3]3 are similarly prepared. Solubilities and reactivities are compared.
Atomic absorption analyses shows rhodium losses of 0.4% (1) and 0.2% (2) per cycle, corresponding to 4.5-
2.2 ppm rhodium/mol of addition product. These data demonstrate the viability and practicality of an exciting
new approach to catalyst immobilization.
The design of new or improved chemical transformations
nated alkane, ether, and tertiary amine solvents. A variety of
such solvents are commercially available and commonly give
bilayers with organic solvents. As such, fluorous media represent
a greatly underutilized “orthogonal phase” for synthesis and
separations.8 Furthermore, many solvent combinations become
miscible at elevated temperatures. This allows chemistry to be
effected under homogeneous one-phase or heterogeneous two-
phase conditions.
How can catalysts be engineered to have high affinities for
fluorous media? Our approach has been to append fluoroalkyl
groups or “pony tails” such as (CH2)y(CF2)xCF3.3a These serve,
when of sufficient length and quantity, a “like dissolves like”
function. Similar strategies are used to design dyes capable of
sticking to Teflon.9 The (CH2)y spacers provide tuning elements
that can be adjusted to insulate the active site from the electron-
withdrawing fluorines (higher y values) or to enhance Lewis
acidity (lower y values).3c The viability of this protocol was
first demonstrated3 with a commodity chemical transformation,
alkene hydroformylation, using a catalyst that was generated
in situ from a rhodium precursor and the fluorous phosphine
P(CH2CH2(CF2)5CF3)3.10 The latter features six perfluorinated
carbons per pony tail and is henceforth abbreviated
invariably turns to catalysis. Two especially active frontiers are
(1) nontraditional reaction media and (2) new catalyst im-
mobilization or recovery strategies to facilitate reuse.2 Toward
these ends, a conceptually new protocol, “fluorous biphase
catalysis”, has been developed in our laboratories.3-7 The term
“fluorous” is used analogously to “aqueous” for highly fluori-
(1) (a) University of Utah. (b) Present address: Concordia College,
Moorhead, MN. (c) Exxon Research and Engineering. (d) Universita¨t
Erlangen-Nu¨rnberg (new permanent address).
(2) (a) Cornils, B. Angew. Chem., Int. Ed. Engl. 1995, 34, 1575; Angew.
Chem. 1995, 107, 1709. (b) Cornils, B. Angew. Chem., Int. Ed. Engl. 1997,
36, 2057; Angew. Chem. 1997, 109, 2147.
(3) (a) Horva´th, I. T.; Ra´bai, J. Science 1994, 266, 72. (b) Horva´th, I.
T.; Ra´bai, J. U.S. Patent 5,463,082, 1995. (c) Horva´th, I. T.; Kiss, G.; Cook,
R. A.; Bond, J. E.; Stevens, P. A.; Raba´i, J.; Mozeleski, E. J. J. Am. Chem.
Soc. 1998, 120, 3133.
(4) Juliette, J. J. J.; Horva´th, I. T.; Gladysz, J. A. Angew. Chem., Int.
Ed. Engl. 1997, 36, 1610; Angew. Chem. 1997, 109, 1682.
(5) Rutherford, D.; Juliette, J. J. J.; Rocaboy, C.; Horva´th, I.; Gladysz,
J. A. Catal. Today 1998, 42, 381.
(6) Horva´th, I. T. Acc. Chem. Res. 1998, 31, 641.
(7) Lead references to other groups now active in fluorous phase
catalysis: (a) Klement, I.; Lu¨tjens, H.; Knochel, P. Angew. Chem., Int. Ed.
Engl. 1997, 36, 1454; Angew. Chem. 1997, 109, 1605. (b) Vincent, J.-M.;
Rabion, A.; Yachandra, V. K.; Fish, R. H. Angew. Chem., Int. Ed. Engl.
1997, 36, 2346; Angew. Chem. 1997, 109, 2438. (c) Betzemeier, B.;
Knochel, P. Angew. Chem., Int. Ed. Engl. 1997, 36, 2623; Angew. Chem.
1997, 109, 2736. (d) Ryu, I.; Niguma, T.; Minakata, S.; Komatsu, M.;
Hadida, S.; Curran, D. P. Tetrahedron Lett. 1997, 38, 7883. (e) Pozzi, G.;
Cinato, F.; Montanari, F.; Quici, S. J. Chem. Soc., Chem. Commun. 1998,
877. (f) Betzemeier, B.; Lhermitte, F.; Knochel, P. Tetrahedron Lett. 1998,
39, 6667. (g) Kling, R.; Sinou, D.; Pozzi, G.; Choplin, A.; Quignard, F.;
Busch, S.; Kainz, S.; Koch, D.; Leitner, W. Tetrahedron Lett. 1998, 39,
9439.
(8) (a) Curran, D. P. Angew. Chem., Int. Ed. Engl. 1998, 37, 1174; Angew.
Chem. 1998, 110, 1230. (b) Barthel-Rosa, L. P.; Gladysz, J. A. Coord. Chem.
ReV. 1999, in press.
(9) (a) Minnesota Mining and Manufacturing Co. British Patent 840,725,
1960. (b) Tiers, G. V. D. (Minnesota Mining and Manufacturing Co.). U.S.
Patent 3,281,426, Oct 25, 1966.
(10) Alvey, L. J.; Rutherford, D.; Juliette, J. J. J.; Gladysz, J. A. J. Org.
Chem. 1998, 63, 6302.
10.1021/ja982955b CCC: $18.00 © 1999 American Chemical Society
Published on Web 03/12/1999

Transition Metal Catalysis in Fluorous Media
J. Am. Chem. Soc., Vol. 121, No. 12, 1999 2697
Scheme 1. Complicating Issues in
Transition-Metal-Catalyzed Hydroboration
target complex ClRh[P(CH2CH2Rf6)3]3 (1). The upper toluene
phase became colorless, and the CF3C6F11 phase became orange.
The latter was separated and taken to dryness to give 1 in 94%
yield as an analytically pure orange powder. The COD remained
in the toluene. This simple workup dramatically illustrates the
utility of fluorous biphase conditions for stoichiometric syn-
theses.
As rendered in Scheme 2, 1 is evocative of a “Teflon
greaseball”. A DSC trace showed a melting point at 90 °C but
no significant decomposition or phase transitions below 300 °C.
To our surprise, single crystals could be obtained from
CF3C6F11/hexane (layering or vapor diffusion). However, they
were soft and diffracted poorly. Crystal structures of related
iridium and rhodium diphosphine complexes have been solved
and exhibit packing motifs with parallel (CF2)x segments and
anti CCCC conformations.15,17 The NMR and IR properties of
1 (Experimental Section) were unexceptional, but very dilute
solutions appeared yellow as opposed to orange.18
For comparison experiments, we sought analogues of 1 in
which (a) the (CF2)x segment was lengthened and (b) all
fluorines were replaced by hydrogens. Accordingly, [Rh(Cl)-
(COD)]2 and the phosphine P(CH2CH2Rf8)3,10 which features
eight perfluorinated carbons per pony tail, were reacted under
the conditions used for 1. Workup gave the higher homologue
ClRh[P(CH2CH2Rf8)3]3 (2; Scheme 2) as an analytically pure
orange powder in 91% yield. Next, [Rh(Cl)(NBD)]2 and
commercially available tri(n-octyl)phosphine, P((CH2)7CH3)3,
were reacted in THF. Workup gave the target complex
ClRh[P((CH2)7CH3)3]3 (3) in 87% yield as a red oil. The NMR
purity was >96%, but correct microanalyses could not be
obtained. Surprisingly, we could not locate a previous report
of this compound in the literature.
The solubility properties of ClRh(PPh3)3 and the new
complexes 1-3 are compared in Chart 1. As expected, the
fluorinated complexes 1 and 2 are very soluble in CF3C6F11,
whereas 3 and ClRh(PPh3)3 are insoluble. Complex 1 is also
soluble in CF3C6H5 (trifluoromethyl benzene), which often
dissolves both fluorous and nonfluorous compounds.8a Complex
1 very faintly colors THF and acetone but is otherwise insoluble
in organic solvents. In contrast, 3 is soluble in all common
organic solvents. Thus, the interchange of (CF2)x and (CH2)x
chains in trialkylphosphine complexes can give striking solubil-
ity differences. Unlike 1, 2 is insoluble in CF3C6H5, THF, and
acetone. The corresponding free phosphines also show a
decrease in absolute solubilities as the (CF2)x segments are
lengthened.10
P(CH2CH2Rf6)3. The product aldehyde was isolated from the
organic phase, and the rhodium was recovered in essentially
quantitative yield from the fluorous phase.3
We sought to develop applications of this protocol in
laboratory-scale catalytic reactions that see use in fine chemical
synthesis. Our attention was drawn to hydroborations of alkenes,
which often require elevated temperatures. A variety of transition
metal and lanthanide catalyst precursors that allow milder
conditions have recently been discovered.12,13 Representative
examples include ClRhL3, [M(COD)(L)(L′)]+ (M ) Rh, Ir),
PdCl2L2, Cp2Ti(CO)2, and SmI3. However, as diagrammed in
Scheme 1, these are destroyed by the customary oxidations of
alkylborane intermediates to alcohol end products (H2O2/NaOH).
An alternative would be to separate the alkylboranes prior to
oxidation. However, they are commonly flammable and incon-
venient to handle. Fluorous catalysts that could be recovered
by phase separations would have obvious advantages.
Wilkinson’s catalyst, ClRh(PPh3)3, is particularly active for
alkene hydroboration, as well as many related transformations.
Hence, we set out to prepare and evaluate fluorous analogues.
As detailed below, fluorous trialkylphosphines give easily
recovered hydroboration catalysts that are effective at 25-40
°C and loadings of 0.009-0.26 mol %, and they give turnover
numbers (TON) higher than 10 000. A portion of this work has
been communicated.4 Applications of these complexes in
catalytic hydrogenations5 and hydrosilylations,14 and syntheses
of related rhodium diphosphine compounds,15 are described
elsewhere.
Results
1. Rhodium Complexes. Efforts were first directed at catalyst
synthesis and characterization. As shown in Scheme 2, a yellow-
orange toluene solution of [Rh(Cl)(COD)]2 and a colorless
CF3C6F11 (perfluorinated methylcyclohexane)16 solution of the
10
fluorous phosphine P(CH2CH2Rf6)3 were stirred at room
temperature. A 1:6 mol ratio was employed, appropriate for the
The data in Chart 1 are qualitative. We sought quantitative
data on relatiVe solubilities, or partition coefficients. These have
a direct bearing on catalyst recovery. Accordingly, 1 and 2
(0.0600-0.0805 g) were added to CF3C6F11/toluene mixtures
(1:1 v/v).19 After 24 h at 27 °C, aliquots were withdrawn from
each phase. Atomic absorption analyses as described in the
Experimental Section gave partition coefficients of 696:1 (99.86:
0.14) and 811:1 (99.88:0.12). Hence, the catalyst with the longer
(CF2)x segments shows the greater fluorous phase affinity.
(11) (a) Most recent review: Beletskaya, I.; Pelter, A. Tetrahedron 1997,
53, 4957. (b) Most recent perspective: Wadepohl, H. Angew. Chem., Int.
Ed. Engl. 1997, 36, 2441; Angew. Chem. 1997, 109, 2547.
(12) Lead references to rhodium catalysts: (a) Ma¨nnig, D.; No¨th, H.
Angew. Chem., Int. Ed. Engl. 1985, 24, 878; Angew. Chem. 1985, 97, 854.
(b) Evans, D. A.; Fu, G. C.; Hoveyda, A. H. J. Am. Chem. Soc. 1992, 114,
6671. (c) Evans, D. A.; Fu, G. C.; Anderson, B. A. J. Am. Chem. Soc.
1992, 114, 6679. (d) Westcott, S. A.; Blom, H. P.; Marder, T. B.; Baker,
R. T. J. Am. Chem. Soc. 1992, 114, 8863. (e) Burgess, K.; van der Donk,
W. A.; Westcott, S. A.; Marder, T. B.; Baker, R. T.; Calabrese, J. C. J.
Am. Chem. Soc. 1992, 114, 9350. (f) Brown, J. M.; Lloyd-Jones, G. C. J.
Am. Chem. Soc. 1994, 116, 866. (g) Pereira, S.; Srebnik, M. J. Am. Chem.
Soc. 1996, 118, 909. (h) Schnyder, A.; Togni, A.; Wiesli, U. Organome-
tallics 1997, 16, 255. (i) Garrett, C. E.; Fu, G. C. J. Org. Chem. 1998, 63,
1370.
(13) Other 1996-98 literature: (a) He, X.; Hartwig, J. F. J. Am. Chem.
Soc. 1996, 118, 1696. (b) Motry, D. H.; Brazil, A. G.; Smith, M. R., III. J.
Am. Chem. Soc. 1997, 119, 2743. (c) Lantero, D. R.; Ward, D. L.; Smith,
M. R., III. J. Am. Chem. Soc. 1997, 119, 9699. (d) Zaidlewicz, M.; Meller,
J. Tetrahedron Lett. 1997, 38, 7279.
(16) We commonly utilize CF3C6F11 in exploratory and mechanistic
studies. Other perfluoroalkane solvents should serve equally well but are
often sold as mixtures of isomers or by boiling point range. This could
compromise the reproducibility and interpretation of rate constants, partition
coefficients, and related measurements.
(17) Fawcett, J.; Hope, E. G.; Kemmitt, R. D. W.; Paige, D. R.; Russell,
D. R.; Stuart, A. M.; Cole-Hamilton, D. J.; Payne, M. J. J. Chem. Soc.,
Chem. Commun. 1997, 1127.
(18) Dilute solutions of ClRh(PPh3)3 do not obey Beer’s law due to
phosphine dissociation: Arai, H.; Halpern, J. J. Chem. Soc., Chem. Commun.
1971, 1571. The visible spectrum of 1 (CF3C6F11) shows a gradual tail with
a very slight shoulder at 429 nm.
(14) Dinh, L.; Gladysz, J. A., manuscript in preparation.
(15) Guillevic, M.-A.; Rocaboy, C.; Arif, A. M.; Horva´th, I. T.; Gladysz,
J. A. Organometallics 1998, 17, 707.

2698 J. Am. Chem. Soc., Vol. 121, No. 12, 1999
Juliette et al.
Scheme 2. Syntheses of Fluorous and Non-Fluorous Catalysts 1-3
Chart 1. Solubilities of Rhodium Complexesa
solvent
ClRh(PPh3)3
ClRh[P(CH2CH2Rf6)3]3 (1)
ClRh[P(CH2CH2Rf8)3]3 (2)
ClRh[(P(CH2)7CH3)3]3 (3)
CF3C6F11
CF3C6H5
pentane
hexane
benzene
toluene
ether
acetone
CHCl3
CH2Cl2
THF
insol
v sl sol
insol
sl sol
sol
sol
sol
sl sol
sol
sol
sol
sol
sol
insol
sol
sl sol
sol
sol
sol
sol
sol
sol
sol
insol
insol
insol
insol
insol
insol
insol
insol
insol
insol
insol
insol
insol
insol
insol
v sl sol
insol
insol
v sl sol
sol
sol
a insol, insoluble; sol, soluble; sl sol, slightly soluble; v sl sol, very slightly soluble.
2. Catalytic Hydroboration and Catalyst Recycling. Mix-
tures of alkenes and freshly distilled catecholborane (4)20 were
treated with 1.21 In all cases, the color of 1 (orange to yellow)
rapidly discharged. Many exploratory runs using the solvent
combinations CF3C6F11/THF or CF3C6F11/toluene and biphasic
conditions (20-45 °C) were successful. The higher temperatures
necessary to achieve single phases were not required. The
original colors returned when reactions were complete. However,
it was soon found that reactions were more rapidly and
economically effected without a nonfluorous solvent, per the
sequence of photographs in Figure 1.
(19) It should be emphasized that liquid biphase systems can contain
both components in each phase. One familiar example is ether/water. After
the ether layer is separated, drying agents are required to render it anhydrous.
With toluene/CF3C6F11 at 25 °C, we measure ratios of 98.4:1.6 (molar),
94.2:5.8 (mass), and 97.1:2.9 (volume) in the upper organic layer, and 3.8:
96.2, 1.0:99.0, and 2.0:98.0 in the lower fluorous layer (Supporting
Information). Since these ratios depend on solutes and temperature, we
approximate our biphase systems as immiscible components that retain their
original volumes in all calculations.
(20) Lane, C. F.; Kabalka, G. W. Tetrahedron 1976, 32, 981.
(21) Sequences in which 1 and 4 were combined in the absence of alkenes
were avoided. 1H NMR experiments showed the formation of rhodium
hydride complexes of limited thermal stability.
Thus, as shown in Scheme 3 (experiment A), a stock solution
of 1 in CF3C6F11 (0.500 mL, 0.00179 M, 8.95 × 10-4 mmol or
0.10 mol %) was added to a 1:1 mixture of norbornene and 4
(0.849 mmol or 950 equiv/Rh).21 Not all of the reactants
dissolved, as indicated by beads or a layer atop the CF3C6F11.

Transition Metal Catalysis in Fluorous Media
J. Am. Chem. Soc., Vol. 121, No. 12, 1999 2699
Figure 1. Representative fluorous rhodium-catalyzed hydroboration: (a) 1 in CF3C6F11; (b) after additions of styrene and catecholborane (4); (c)
after completion of reaction and addition of THF.
Scheme 3. Fluorous Rhodium-Catalyzed Hydroboration

2700 J. Am. Chem. Soc., Vol. 121, No. 12, 1999
Juliette et al.
Chart 2. Alcohols Synthesized under the Conditions of
than 90%. A small amount of gelatinous and possibly polymeric
material was noted. Over five cycles, combined TON values of
2411 and 2129 were achieved. Although the yields in experi-
ments A-E generally appear to drift downward, the rhodium
loss per cycle is minuscule, as described below. An experiment
analogous to D was conducted at room temperature (8-h cycles),
and data are summarized in footnote 8b of our communication.4
Control experiments relating to Scheme 3 were conducted.
First, no reactions of norbornene (40 °C, 2 h) or styrene (room
temperature, 14 h) and 4 were detected in the absence of 1.
Uncatalyzed reactions of alkenes and 4 commonly require 100
°C.22 Second, the reaction with norbornene was repeated (0.701
mmol, 0.16 mol % 1), but the two C6D6 extracts were analyzed
separately. The first contained 0.610 mmol of 5 (87%), and the
second 0.028 mmol (4%). Thus, yields should not be signifi-
cantly increased by a third extraction. Finally, the CF3C6F11/
toluene partition coefficient of 1-dodecene was carefully
determined by GLC.5,8b The result, 2.5:97.5 (24 °C), illustrates
the limited affinity of the types of alkenes used in this study
for fluorous media. However, it also shows that alkenes are, to
some extent, fluorocarbon soluble.
Scheme 3a
3. Isolation of Alcohols. We next sought to transform alkenes
to alcohols. Thus, norbornene and 4 (1:1.1) and a CF3C6F11
solution of 1 (0.04 mol %) were combined as described above.
The sample was kept at 40 °C for 5 h, cooled, and extracted
with THF. An oxidative workup (H2O2/NaOH) gave exo-
norborneol as a spectroscopically pure white solid in 90% yield
(TON 2487), as shown in Chart 2.
Analogous reactions were conducted with a variety of educts,
as summarized in Chart 2. These include monosubstituted, all
patterns of disubstituted, and trisubstituted alkenes. Some THF
was added to dissolve the only solid substrate, trans-stilbene.
With the exception of the least reactive alkene, cyclopentene,
reaction times ranged from 1 to 16 h, and no special efforts
were made to optimize catalyst loadings (0.04-0.26 mol %) or
isolated yields (92-77%). All product identities were verified
a 40 °C, 0.5-16 h. b These data are from 23-24-h reactions.
by at least two criteria (1H/13C NMR or H NMR/GLC).
The sample was kept for 1 h at 40 °C, cooled to room
temperature, and extracted twice with C6D6 (0.5 mL). A weighed
amount of Ph3SiCH3 was added to the extract, and NMR
analysis showed 0.765 mmol of the organoborane 5 (90%, TON
854). The CF3C6F11 mother solution was added to a second
sample of norbornene and 4 (950 equiv). An identical reaction
and workup gave a C6D6 solution containing 0.702 mmol of 5
(83%, TON 785). A third cycle gave similar data, for a
combined TON value of 2409, as summarized in Scheme 3.
Similar sequences were conducted with catalysts 1 and 2
(Scheme 3, experiments B and C; 1.00:1.05 norbornene/4). It
was independently shown that 2 was not quite as reactive as 1
(TON 129 vs 102; 1 h, 40 °C, 0.11 mol %). Thus, experiment
C was conducted at 45 instead of 40 °C. Over four cycles,
combined TON values of 2961 and 2479 were achieved. As
with experiment A, yields for each cycle fluctuated somewhat
(90-84% and 86-81%). Furthermore, experiment B did not
give appreciably better yields than A, despite longer cycle times
(3 vs 1 h). NMR spectra showed that some alkene remained.
Catalyst 1 routinely gave 90-100% conversions in similar
alkene hydrogenation cycles, as detailed elsewhere.5 However,
rhodium-catalyzed hydroborations are, as discussed below,
mechanistically more complex and possibly subject to inhibition
by non-fluorous side products that are removed by extraction.
Similar reactions were conducted with styrene, 1, and 2
(Scheme 3, experiments D and E). The yield of organoborane
6, which formed as a mixture of R/â (branched/linear) regioi-
somers, was assayed by NMR. The cycle times were lengthened
(5 h), but yields still fluctuated, and the average remained less
1
For several alkenes, more than one alcohol regioisomer or
diastereomer is possible. However, only styrene, p-methoxy-
styrene, and p-chlorostyrene gave mixtures. These are also the
only alkenes for which selectivities differ from those of
uncatalyzed reactions (in which primary alcohols constitute
>90% of the product). Interestingly, the regiochemistry of
rhodium-catalyzed hydroborations of styrenes can vary, and
catalyst purity has been shown to be a critical factor.12c,d The
ratios in Chart 2 have been reproduced many times with different
batches of both 1 and 4.
Finally, the feasibility of lower catalyst loadings and com-
mensurably higher TON values was tested. Thus, the reaction
of norbornene, 4, and 1 was repeated, but with a 11150:13520:1
mol ratio (0.009 mol % 1). As would be expected, the reaction
time had to be lengthened (23 h). However, workup gave exo-
norborneol in 93% yield, corresponding to a TON of 10 370!
4. Isolation of Organoboron Products. We sought to extend
the reactions in Scheme 3 and Chart 2. In particular, alkenylbo-
ranes are much more robust and easier to isolate than alkylbo-
ranes and are versatile substrates for a variety of metal-catalyzed
coupling reactions.23 As shown by the first two examples in
Chart 3, 1 catalyzed the addition of 4 to alkynes. Reactions
were more rapid than those in Chart 2 (0.5 h, 40 °C).
Spectroscopically pure alkenylboranes were isolated in 89-88%
(22) Brown, H. C.; Gupta, S. K. J. Am. Chem. Soc. 1975, 97, 5249.
(23) (a) Miyaura, N.; Suzuki, A. Chem. ReV. 1995, 95, 2457. (b) Suzuki,
A. In Metal-catalyzed Cross-coupling Reactions; Diederich, F., Stang, P.
J., Eds.; Wiley-VCH: New York, 1998; Chapter 2.

Transition Metal Catalysis in Fluorous Media
J. Am. Chem. Soc., Vol. 121, No. 12, 1999 2701
Chart 3. Organoborane Compounds Isolateda
catalyzed reactions give deuterium at both C2 and C1 (85:15).7c
This has been interpreted in the context of a reversible addition
of a rhodium deuteride intermediate to a coordinated alkene.
5. Catalyst Activity, Mechanism, and Leaching. Although
1 has obvious advantages over ClRh(PPh3)3 from the standpoint
of catalyst recovery, there is the attendant question of relative
reactivity. As is obvious from Chart 1, few solvents dissolve
both species. However, with effort, 0.00086 M solutions of
ClRh(PPh3)3 in CF3C6H5 could be obtained. Equimolar CF3C6H5
solutions of 1 and the tri(n-octyl)phosphine complex 3 were
also prepared. These were combined with norbornene and 4
(0.61-0.63 mmol) in NMR tubes. After 15 min at room
temperature, the sample with ClRh(PPh3)3 had completely
reacted. The sample with 1 showed no reaction after 5 h. That
with 3 showed 4% conversion after 3 h and 10% conversion
after 22 h. This establishes the reactivity order ClRh(PPh3)3 >
3 > 1 (and 1 > 2 from data above). Hence, arylphosphine
ligands give more reactive catalysts than alkylphosphines, and
the fluorine substituents in 1 further retard reactivity.
The mechanism of rhodium-catalyzed hydroboration has been
studied in detail. It has been shown that ClRh(PPh3)3 and 4 react
in the absence of alkenes to give complex mixtures of rhodium
hydrides and redistribution products, many of which may
independently participate in or inhibit catalysis.12d,26 This may
account for some of the yield trends in Scheme 3. There is also
the possibility of a change of mechanism in fluorous media.
One probe is provided by the regiochemistry of addition to
styrene, which is, as noted above, very sensitive to catalyst purity
and, presumably, mechanism. However, 1 (in CF3C6F11) and 3
(in C6D6) gave similar mixtures of isomers (styrene, R/â 55:45
vs 54:46; p-methoxystyrene, 39:61 vs 30:70). In general,
rhodium alkylphosphine catalysts do not give high regio-
selectivities,12d,26 whereas under rigorously anerobic conditions
ClRh(PPh3)3 gives exclusively the branched R isomer.12c
Catalyst leaching was probed by atomic absorption analysis.
Norbornene, 4, and 1 (0.0302 g, 0.112 mol %) were reacted in
CF3C6F11 (2.5 mL) as described above. Then CF3C6F11 (7.5 mL)
and toluene (10 mL) were added with shaking. After 15 min, a
large toluene aliquot (8.0 mL) was removed by syringe. More
toluene was added (8.0 mL), and the extraction was repeated
(8.0 mL). Both aliquots gave identical rhodium analyses (0.20
ppm), and an aliquot of the CF3C6F11 phase (8.0 mL) gave, as
expected, a much higher rhodium analysis (46.9 ppm). These
values correspond to 0.4% leaching over two extractions. After
adjustment for the solvent volumes not analyzed,19 the rhodium
mass recovery is 91%. An identical experiment with 2 gave
0.2% leaching and a mass recovery of 96%. If all of the
norbornene is consumed, this corresponds to a loss of 4.5 ppm
rhodium/mol of product for 1, and 2.2 ppm for 2.
There was no loss of activity when recovered catalyst
solutions were transferred to fresh vials. No evidence for the
formation of heterogeneous rhodium-containing substances was
ever observed. In contrast, 1 is not indefinitely stable to
hydrogenation conditions,5 and a black solid usually deposits
after three cycles. Activity then drops precipitously. Solid 1 (0.2
mol %) was added to a C6D6 solution of norbornene and 4 and
remained undissolved. After 2 and 24 h at 40 °C, reaction was
17% and 62% complete, respectively. Thus, 1 appears to serve
as a heterogeneous catalyst at a solid/solution interface.
However, it is also possible that, within the limits set by the
leaching experiments, very small quantities of a soluble active
catalyst are generated. The issue of whether the dominant
a 40 °C, 0.5-16 h. b 95:5 mixture of isomers (see refs 25 and 39).
Scheme 4. Deuterium Labeling Experiments
yields, as assayed by integration vs a weighed amount of an
NMR standard. The catalyst was recovered from the reaction
with phenylacetylene and reused (88% and TON 474 for second
cycle).
During the course of this study, Pereira and Srebnik reported
the zirconium- and rhodium-catalyzed addition of pinacolborane
(7) to alkenes and alkynes.12g,24 Importantly, the resulting
organoboranes are stable to air, moisture, and chromatography.25
As shown by the last three examples in Chart 3, 1 also efficiently
catalyzed the addition of 7 to alkenes and alkynes. The product
mixture obtained with styrene is similar to that produced by
ClRh(PPh3)3.12g
We sought to probe for hidden scrambling processes by
deuterium labeling. As shown in Scheme 4, B-deuteriocat-
echolborane (4-d1), excess 1-decene, and a CF3C6F11 solution
of 1 were combined at 40 °C. After 24 h, the C6D6 extract was
2
analyzed by H NMR before and after the removal of excess
1-decene. The alkylborane showed an intense signal for a C2
label (1.54 ppm). The analogous natural abundance adduct was
isolated as a white solid in 82% yield (TON 424) from the
reaction in Chart 2 and characterized by 1H NMR. The labeled
sample was oxidized to 1-decanol, and 1H and 2H NMR spectra
were recorded. At all stages, only C2 deuterium was observed.
As little as 4% of a C1-labeled alcohol (3.68 ppm) would have
been detected. Hence, the addition of 4 to 1-decene occurs
without significant scrambling. Interestingly, ClRh(PPh3)3-
(24) Pereira, S.; Srebnik, M. Organometallics 1995, 14, 3127.
(25) Tucker, C. E.; Davidson, J.; Knochel, P. J. Org. Chem. 1992, 57,
3482.
(26) Westcott, S. A.; Blom, H. P.; Marder, T. B.; Baker, R. T.; Calabrese,
J. C. Inorg. Chem. 1993, 32, 2175.

2702 J. Am. Chem. Soc., Vol. 121, No. 12, 1999
Juliette et al.
catalytic pathway in Scheme 3 involves the fluorous phase or
the interface is also complex and will be addressed with
mechanistically less complicated transformations in the future.
selectivities for oxidative additions in CF3C6F11. However,
Charts 2 and 3 show only normal hydroboration selectivity
patterns.
The successful application of 1 and 2 in catalytic hydrogena-
tions and hydrosilylations5,14 augers well for future extensions
of this chemistry. For example, it is highly probable that other
boron-X bond additions, such as the diborylation of alkenes,30
can be effected under the conditions of Scheme 3. More
speculatively, it might be possible to eliminate waste products
altogether by designing a recoverable boron compound that
could be recycled to a boron hydride. Chiral, nonracemic
fluorous phosphines should allow enantioselective syntheses.
Finally, there are tantalizing possibilities for liquid-phase
combinatorial syntheses involving a sequence of fluorous
catalysts.8a
In conclusion, this paper has rigorously documented (1) the
facile synthesis and fundamental physical properties of the new
fluorous rhodium catalysts 1 and 2, (2) the exceptional affinities
of 1 and 2 for fluorous media, and (3) numerous preparative
catalytic hydroboration reactions from which alcohol or orga-
noboron products have been isolated in high yields from organic
phases, very high levels of catalysts recovered from fluorous
phases, and TON values optimized to higher than 10 000/cycle.
Similar studies involving other new fluorous catalysts and
reagents will be reported soon.
Discussion
The above data demonstrate the viability and practicality of
a new approach to catalyst immobilization in the context of an
important laboratory-scale reaction that is extensively utilized
in fine chemical synthesis. To our knowledge, 1 and 2 represent
the first recoverable hydroboration catalystssa type of attribute
that is increasingly important from environmental standpoints.
Both 1 and 2 (and the constituent phosphines)10 are readily
prepared and exhibit impressive thermal stability. However, it
should be emphasized they are by no means optimized. Many
further refinements can be envisioned.
First, it should be possible to further enhance partition
coefficients and catalyst recovery by using phosphines with
longer or branched Rf segments. In this context, it should be
kept in mind that 1 and 2 are catalyst precursors. Rhodium loss
during product extraction will depend more upon the partition
characteristics of the catalyst rest state, or a catalyst-product
complex. Furthermore, phosphines commonly dissociate from
rhodium during catalysis.19 Thus, most intermediates will be
“less fluorous” than 1 and 2, and increased equilibrium
concentrations in the nonfluorous phase are probable. Partition
coefficients for P(CH2CH2Rf6)3 and P(CH2CH2Rf8)3 are 98.8:
1.2 and >99.7:<0.3, respectively (toluene/CF3C6F11, 27 °C).10
Second, our data and those of prior investigators12d show that
rhodium trialkylphosphine complexes are less active hydrobo-
ration catalysts than rhodium triarylphosphine complexes.
Accordingly, syntheses of fluorous triarylphosphines are under
intense investigation in our laboratory27 and others.28 However,
we chose not to measure turnover rates as a function of cycle
in Scheme 3. As noted above, compositions of rhodium
hydroboration catalysts have been shown to change.12d,e,26 Also,
Figure 1 shows a slight color change between panels a (virgin
catalyst) and c (after reaction and extraction of nonfluorous
species), as well as a dramatic bleaching in panel b (where a
different rest state is probable). Hence, we plan to assay the
activities of recovered 1 and 2 in connection with mechanisti-
cally less complex addition reactions. The critically important
result from this study is the very low level of rhodium loss.
Experimental Section
General Data. Reactions were conducted under N2 atmospheres.
Instrumentation and solvent and reagent purifications were similar to
those described earlier5,15 and are fully documented in the Supporting
Information.
ClRh[P(CH2CH2Rf6)3]3 (1). A flask was charged with P(CH2CH2Rf6)3
(0.643 g, 0.600 mmol)10 and CF3C6F11 (1 mL), and a solution of
[Rh(Cl)(COD)]2 (0.049 g, 0.0994 mmol) in toluene (1 mL) was added.
The biphasic mixture was stirred overnight. The phases were separated
and the CF3C6F11 removed by oil pump vacuum to give 1 as a bright
orange solid (0.620 g, 0.186 mmol, 94%), mp 89.8 °C (Te, DSC;31 no
other phase transitions between 23 °C and the onset of thermal
decomposition, >304 °C). Anal. Calcd for C72H36ClF117P3Rh: C, 25.77;
H, 1.08. Found: C, 25.85; H, 1.09. IR (cm-1, KBr): 1247 m, 1145 m,
1
949 w. H NMR (δ, CF3C6F11, external C6D6 lock): 2.20 (br, 6H),
1.90 (br, 6H). 31P{1H} NMR (ppm, CF3C6F11, external C6D6 lock): 12.9
(dd, JPRh ) 136 Hz, JPP ) 39 Hz), 29.3 (dt, JPRh ) 186 Hz, JPP ) 39
Hz).
ClRh[P(CH2CH2Rf8)3]3 (2). Compounds P(CH2CH2Rf8)3 (1.860 g,
1.356 mmol),10 CF3C6F11 (3 mL), [Rh(Cl)(COD)]2 (0.110 g, 0.226
mmol), and toluene (2 mL) were combined in a procedure analogous
to that for 1. An identical workup gave 2 as a bright orange solid (1.749
g, 0.411 mmol, 91%), mp 103.7 °C (Te, DSC;31 no other phase
transitions between 23 °C and the onset of thermal decomposition, >270
°C). Anal. Calcd for C90H36ClF153P3Rh: C, 25.40; H, 0.85. Found: C,
25.43; H, 0.93. IR (cm-1, KBr): 1244 m, 1203 m, 1148 m, 967 w. 1H
NMR (δ, CF3C6F11, external CDCl3 lock): 1.95 (br, 2H), 2.20 (br, 4H),
2.45 (br, 6H). 31P{1H} NMR (ppm, CF3C6F11): 14.5 (dd, JPRh ) 134
Hz, JPP ) 40 Hz), 28.5 (dt, JPRh ) 183 Hz, JPP ) 40 Hz).
ClRh[P((CH2)7CH3)3]3 (3). A flask was charged with [Rh(Cl)(N-
BD)]2 (0.080 g, 0.173 mmol) and THF (5 mL), and P((CH2)7CH3)3
(0.464 mL, 0.386 g, 1.041 mmol) was added with stirring. The yellow
solution turned red. After 2 h, the volatiles were removed by oil pump
vacuum to give crude 3 as a red oil (0.380 g, 0.304 mmol, 87%, >96%
purity by 31P NMR. Anal. Calcd for C72H153ClP3Rh: C, 69.17; H, 12.33.
Found: C, 68.25; H, 12.16.32 1H NMR (δ, C6D6): 2.18-2.04 (br, 2H),
1.90-1.69 (br, 2H) 1.60-1.22 (m, 10H), 1.02-0.88 (m, 3H). 31P{1H}
Some related reactions deserve note. First, the fluorous
hydroformylation catalyst reported earlier exhibits, in the
absence of alkene, a HRh(CO)[P(CH2CH2Rf6)3)]3 rest state.3 It
shows better long-term stability than the analogous PPh3 catalyst
and lower leaching levels than 1 and 2 (1.18 vs 4.5 and 2.2
ppm rhodium/product). However, we made no attempt to
optimize our values, which should be even lower under the high
TON conditions for norbornene in Chart 2. Second, there is
increasing precedent for carbon-fluorine bond oxidative addi-
tions involving coordinatively unsaturated metal fragments.29
Fortunately, we see no evidence for such deactivation pathways,
including extensive studies with related 16-valence-electron
iridium complexes.15 The iridium complexes also exhibit unique
(27) Rutherford, D.; Barthel-Rosa, L. P.; Bennett, B. L., work in progress,
University of Utah.
(28) See ref 7c and the following: (a) Bhattacharyya, P.; Gudmunsen,
D.; Hope, E. G.; Kemmitt, R. D.; Paige, D. R.; Stuart, A. M. J. Chem.
Soc., Perkin Trans. 1 1997, 3609. (b) Kainz, S.; Koch, D.; Baumann, W.;
Leitner, W. Angew. Chem., Int. Ed. Engl. 1997, 36, 1628; Angew. Chem.
1997, 109, 1699.
(29) (a) Kiplinger, J. L.; Richmond, T. G.; Osterberg, C. E. Chem. ReV.
1994, 94, 373. (b) Burdeniuc, J.; Jedlicka, B.; Crabtree, R. H. Chem. Ber./
Recl. 1997, 130, 145.
(30) Marder, T. B.; Norman, N. C. Top. Catal. 1998, 5, 63.
(31) Cammenga, H. K.; Epple, M. Angew. Chem., Int. Ed. Engl. 1995,
34, 4, 1171; Angew. Chem. 1995, 107, 1284.
(32) Complex 3 remains soluble in hexane at -30 °C, and analytically
pure samples have not yet been obtained.

Transition Metal Catalysis in Fluorous Media
J. Am. Chem. Soc., Vol. 121, No. 12, 1999 2703
NMR (ppm, C6D6): 29.1 (dt, JPRh ) 185 Hz, JPP ) 41 Hz), 13.4 (dd,
JPRh ) 134 Hz, JPP ) 41 Hz). 13C{1H} NMR (ppm, C7D8): 32.8, 32.8,
32.7 (br overlapping C1/C6); 30.8, 30.6, 30.5, 30.3, 30.3 (br overlapping
C4/C5); 27.2, 27.1, 26.9, 26.4, 26.2 (br overlapping C2/C3); 23.6 (s,
C7); 14.8, 14.8 (2s, C8, ca. 2:1).33
(0.75 mL, 6.7 mmol) as described in the reaction of norbornene. An
identical workup gave phenylethanol as a clear, colorless oil (0.522 g,
4.27 mmol, 90%, TON 1906). The 1H and 13C NMR spectra (Supporting
Information) matched those in the Sadtler reference series and indicated
a 55:45 mixture of R/â regioisomers.
Hydroborations. General Aspects. (1) Catecholborane (4, Aldrich)
was vacuum transferred (oil pump) and stored at -30 °C under N2 for
no more than 72 h. (2) Reactions were conducted under rigorously
anaerobic conditions with magnetic stirring, such that 1 and 4 were
not combined in the absence of an alkene.21 (3) Silicone oil baths
(continuously stirred, (1 °C) were used for temperature control. (4)
All CF3C6F11/solvent mixtures were allowed to settle for 5 min before
phase separation. Otherwise, small amounts of CF3C6F11 sometimes
later separated from the nonfluorous phase.
Organoborane Syntheses (Chart 3). The following are representa-
tive, and others are given in the Supporting Information.
A. Phenylacetylene and 4.38a A flask was charged with a CF3C6F11
solution of 1 (0.500 mL, 1.79 × 10-3 M; 8.95 × 10-4 mmol, 0.19 mol
%), phenylacetylene (0.053 mL, 0.049 g, 0.48 mmol, 536 equiv/Rh),
and 4 (0.065 mL, 0.073 g, 0.61 mmol). The mixture was kept in a 40
°C bath (0.5 h), cooled to room temperature, and extracted with THF
(2 × 0.5 mL). Solvent was removed by oil pump vacuum to give the
phenylacetylene/4 adduct as a white solid (0.100 g, 0.450 mmol, 94%,
TON 503).38 The CF3C6F11 solution of 1 was subjected to an identical
charge/workup cycle (0.422 mmol adduct, 88%; TON ) 474).
B. Phenylacetylene and Pinacolborane (7).39a A flask was charged
with 7 (0.179 g, 1.400 mmol), phenylacetylene (0.143 g, 1.400 mmol,
786 equiv/Rh), and a CF3C6F11 solution of 1 (0.500 mL, 3.56 × 10-3
M; 1.78 × 10-3 mmol, 0.13 mol %). The yellow solution turned
colorless. The mixture was kept in a 40 °C bath (12 h), cooled to room
temperature, and extracted with toluene (3 × 0.5 mL). Solvent was
removed by water aspirator vacuum. The yellow oil was flash
chromatographed on silica gel (98:2 v/v hexanes/ether) to give the
phenylacetylene/7 adduct as a lightly colored mixture of isomers (95:5
trans/minor; 0.291 g, 1.26 mmol, 90%, TON 709) that was pure by 1H
and 13C NMR.39b,c
Sequential Reactions (Scheme 3). The following are representative
and others are given in the Supporting Information.
Series B. A flask was charged with norbornene (0.0746 g, 0.792
mmol, 885 equiv/Rh), 4 (0.100 g, 0.834 mmol), and a CF3C6F11 solution
of 1 (0.500 mL, 1.79 × 10-3 M; 8.95 × 10-4 mmol, 0.11 mol %). The
mixture was kept in a 40 °C bath (3 h), cooled to room temperature,
and extracted with C6D6 (2 × 0.5 mL). Then Ph3SiCH3 (0.0481 g, 0.175
mmol) was added to the C6D6, and the yield of the adduct 5 was assayed
by 1H NMR (see Scheme 3).34 The CF3C6F11 solution was subjected to
three similar charge/workup cycles.
Series D. A flask was charged with a CF3C6F11 solution of 1 (0.600
mL, 1.79 × 10-3 M; 1.07 × 10-3 mmol; 0.19 mol %), styrene (0.0574
g, 0.551 mmol, 515 equiv/Rh), and 4 (0.068 g, 0.567 mmol). The
mixture was stirred (5 h) and extracted with C6D6 (2 × 0.5 mL). Then
Ph3SiCH3 was added (0.0837 g, 0.305 mmol), and the yields of the
regioisomeric adducts 6 (R or branched/â or linear ) 57:43) were
assayed by 1H NMR (see Scheme 3).35 The CF3C6F11 solution was
subjected to four similar charge/workup cycles (R/â 58:42, 61:39, 61:
39, 60:40).
Deuterium Labeling (Scheme 4). A flask was charged with a
CF3C6F11 solution of 1 (0.500 mL, 3.56 × 10-3 M; 1.78 × 10-3 mmol,
0.35 mol % vs 4-d1), freshly distilled 1-decene (0.719 g, 5.13 mmol;
10 equiv vs 4-d1), and B-deuteriocatecholborane (4-d1;12c 0.062 g, 0.513
mmol; Supporting Information). The mixture was kept in a 40 °C bath
(24 h), cooled to room temperature, and extracted with C6D6 (2 × 0.5
2
2
Alcohol Syntheses (Chart 2). The following are representative, and
others are given in the Supporting Information.
mL). A H NMR spectrum showed the natural abundance H signals
of excess 1-decene and a much stronger signal at 1.54 ppm (vs C6D6
at 7.15 ppm; ca. 40% more intense than the total 1-decene 2H integral).
The 1-decene was removed by vacuum transfer, and a 2H NMR
spectrum of the residue showed only a signal at 1.55 ppm. A signal
with 4% of this area would have been detected. The sample was
A. Reaction of Norbornene.36 A flask was charged with norbornene
(0.2458 g, 2.61 mmol, 2762 equiv/Rh), 4 (0.342 g, 2.85 mmol), and a
CF3C6F11 solution of 1 (0.500 mL, 1.89 × 10-3 M; 9.45 × 10-4 mmol,
0.04 mol %). The mixture was kept in a 40 °C bath (5 h), cooled to
room temperature, and extracted with THF (2 × 5 mL). Solvent was
removed by oil pump vacuum at 0 °C to give a white solid. Then
ethanol/THF (10 mL, 1:1 v/v) and NaOH (5 mL, 2 M in H2O) were
added. The mixture was placed in an ice bath, and 30% H2O2 (1.0 mL,
8.8 mmol) was added dropwise with stirring. After 0.5 h, the ice bath
was removed. After 6 h, the mixture was extracted with ether (3 × 15
mL). The extract was washed with NaOH (10 mL, 0.5 M in H2O),
H2O (25 mL), and brine (15 mL) and dried over MgSO4. Solvent was
removed by rotary evaporation to give exo-norborneol as a white solid
(0.2633 g, 2.35 mmol, 90%, TON 2487). The 1H and 13C NMR spectra
(Supporting Information) matched those in the Sadtler reference series.
The former spectrum was recorded with weighed amounts of sample
and Ph3SiCH3 standard, and integration established a product purity of
>98%.
1
oxidized (NaOH/H2O2 as in Chart 2) to 1-decanol, and the H NMR
spectrum (δ (CDCl3) 3.68 (d, 2H, CH2OH), 1.60-1.55 (m, 1H), 1.40-
1.20 (m, 14 H), 0.87 (t, 3H)) was compared to that of authentic
1-decanol. The 2H NMR spectrum showed only one signal, coincident
with the 1.55 ppm CH2CH2OH signal of 1-decanol.
Relative Catalyst Reactivities. Run A: An NMR tube was charged
with ClRh(PPh3)3 (0.300 mL, 8.6 × 10-4 M in CF3C6H5; 2.58 × 10-4
mmol, 0.04 mol %), norbornene (0.057 g, 0.61 mmol, 2352 equiv/
Rh), and 4 (0.065 mL, 0.073 g, 0.61 mmol). 1H NMR spectra (external
C6D6 lock/reference) showed complete conversion to 5 after 15 min.34a
Run B: An NMR tube was charged with 3 (0.500 mL, 8.6 × 10-4
M
in CF3C6H5; 4.3 × 10-4 mmol, 0.07 mol %), norbornene (0.058 g,
0.62 mmol, 1432 equiv/Rh), and 4 (0.067 mL, 0.075 g, 0.63 mmol).
After 3 and 22.5 h, NMR spectra showed 4% and 10% conversion to
B. Reaction of Styrene.37 A flask was charged with a CF3C6F11
solution of 1 (0.500 mL, 4.47 × 10-3 M; 2.24 × 10-3 mmol, 0.05 mol
%), styrene (0.495 g, 4.75 mmol, 2121 equiv/Rh), and 4 (0.507 mL,
0.570 g, 4.75 mmol). The mixture was kept in a 40 °C bath (10 h),
cooled to room temperature, and extracted with THF (3 × 3 mL). The
extract was treated with NaOH (10 mL, 2 M in H2O) and 30% H2O2
(38) (a) For the analogous uncatalyzed reaction, which gives a 91:9
mixture of isomers, see ref 22. No data were given for the minor isomer,
but it was assigned as a regioisomer. A second set of very minor 13C NMR
signals was also detected in some samples of our phenylacetylene/4 adduct.
(b) NMR (C6D6): 1H (δ) 7.73 (d, J ) 19 Hz, 1H), 7.26-7.21 (m, 2H),
7.05-6.99 (m, 5H), 6.80-6.77 (m, 2H), 6.37 (d, J ) 19 Hz, 1H); 13C (ppm)
152.3, 137.3, 132.4, 129.7, 128.9, 127.7, 122.9, 122.8, 112.6, 112.4. The
1H NMR spectrum was recorded with weighed amounts of sample and
Ph3SiCH3 standard, and integration (δ 7.73 vs 0.69) confirmed the product
yield and purity (>98%). The 1H NMR data closely matched those
previously reported.22
(39) (a) For the analogous uncatalyzed reaction (96:4 mixture of isomers),
see ref 25. (b) Our NMR data for the major (trans) isomer closely match
those previously reported.25 No data were given for the minor isomer, but
it was assigned as a stereoisomer (in constast to the minor isomer from
phenylacetylene and 438a). (c) NMR (CDCl3): 1H (δ) 7.38-6.94 (ArH, 12H),
trans at 6.06 (d, J ) 18 Hz, 1H) and 1.30 (s, 12H), minor (partial) at 1.22
(s, 12H); 13C{1H} (ppm) trans at 149.4, 128.8, 128.7, 128.4, 128.0, 126.9,
116.2 (br), 83.1, 24.6, minor at 137.7, 137.3, 130.7, 128.0, 127.0, 125.1,
116.2 (br), 83.5, 21.0.
(33) The resonances were assigned as in footnote 39 of ref 15.
(34) (a) NMR (C6D6): 1H (δ) 7.05-6.95 (m, 2H), 6.85-6.70 (m, 2H),
2.43 (s, 1H), 2.09 (br s, 1H), 1.80-1.75 (m, 1H), 1.43-1.26 (m, 4H), 1.22-
1.01 (m, 4H); 13C (ppm) 148.9, 122.7, 112.5, 39.3, 38.5, 37.0, 32.7, 32.4,
29.4. (b) The δ 2.43 resonance of 5 was integrated vs the δ 0.69 resonance
of Ph3SiCH3.
(35) The δ 1.42 and 1.36 resonances of 6R (d, J ) 8 Hz, 3H) and 6â (t,
J ) 7 Hz, 2H) were integrated vs the δ 0.69 resonance of Ph3SiCH3.
(36) For the analogous uncatalyzed reaction, see ref 22 and the
following: Pelter, A.; Smith, K.; Brown, H. C. In Borane Reagents;
Katritzky, A. R., Meth-Cohn, O., Rees, C. W., Eds.; Academic Press: New
York, 1988; p 194.
(37) For the analogous uncatalyzed reaction, see refs 20 and 22.

2704 J. Am. Chem. Soc., Vol. 121, No. 12, 1999
Juliette et al.
5, respectively. Run C: An NMR tube was charged with 1 (0.300 mL,
8.6 × 10-4 M in CF3C6H5; 2.58 × 10-4 mmol, 0.04 mol %), norbornene
(0.059 g, 0.63 mmol, 2437 equiv/Rh), and 4 (0.067 mL, 0.075 g, 0.63
mmol). After 0.25 and 5 h, NMR spectra showed no reaction.
Partition Coefficients. A 2-dram vial was charged with 1 (0.0600
g ) 0.00184 g of rhodium), CF3C6F11 (5.00 mL; shaken to dissolve 1),
and toluene (5.00 mL). The vial was vigorously shaken (2 min) and
equilibrated (27 °C, 24 h) in an inert atmosphere glovebox. An aliquot
(3.0 mL) was removed from each layer by syringe. Analysis by ICP-
AES indicated 0.27 ppm or 0.0000012 g of rhodium (toluene), and
188 ppm or 0.001680 g of rhodium (CF3C6F11).19 An analogous
experiment with 2 (0.0805 or 0.00195 g of rhodium) gave 0.27 ppm
or 0.0000012 g of rhodium (toluene), and 219 ppm or 0.00196 g of
rhodium (CF3C6F11).
toluene (10.00 mL) were added. The vial was vigorously shaken (5
min). After 15 min (27 °C), a toluene aliquot (8.0 mL) was removed
by syringe. Fresh toluene (8.0 mL) was added, and the vial was
vigorously shaken. After 15 min, a second toluene aliquot and a
CF3C6F11 aliquot (8.0 mL each) were removed. Analysis by ICP-AES
as described earlier3c indicated 0.20, 0.20, and 46.9 ppm (0.0000017,
0.0000014, and 0.000838 g; 91% mass balance) of rhodium. An
analogous experiment with 2 (0.0383 g ) 0.000926 g of rhodium, 9.00
× 10-3 mmol, 0.111 mol %), norbornene (0.7605 g, 8.08 mmol), and
4 (1.026 g, 8.56 mmol) gave 0.10, 0.10, and 49.8 ppm (0.0000009,
0.0000007, and 0.000890 g; 96% mass balance) of rhodium.
Acknowledgment. We thank the NSF (CHE-9401572) for
support of this research.
Rhodium Leaching. A 6-dram vial was charged with 1 (0.0302 g
) 0.000926 g of rhodium, 9.00 × 10-3 mmol, 0.112 mol %), CF3C6F11
(2.5 mL; shaken to dissolve 1), norbornene (0.7602 g, 8.07 mmol), 4
(1.013 g, 8.45 mmol), and a stir bar. The vial was sealed and moved
from an inert atmosphere glovebox to a 45 °C bath. The sample was
stirred (3 h) and returned to a glovebox, and CF3C6F11 (7.50 mL) and
Supporting Information Available: Additional experimen-
tal details (PDF). This material is available free of charge via
the Internet at http://pubs.acs.org.
JA982955B