Synthesis, structure, and reactivity of fluorous phosphorus/ carbon/phosphorus pincer ligands and metal complexes

Article abstract of DOI:10.1039/b502309b

Reactions of the diphosphine 1,3-C₆H₄(CH ₂PH₂)₂ and fluorous alkenes H ₂C=CHR_fn (R_fn = (CF₂) ^n-1CF₃; n = 6, 8) at 75°C in the presence of AIBN give the title ligands 1,3-C₆H₄(CH₂P(CH ₂CH₂R_fn)₂)₂ (3-R _fn) and byproducts 1,3-C₆H₄(CH ₃)(CH₂P(CH₂CH₂R_fn) ₂) (4-R_fn) in 1 : 3 to 1 : 5 ratios. Workups give 3-R _fn in 4-17% yields. Similar results are obtained photochemically. Reaction of 1,3-C₆H₄(CH₂Br)₂ and HP(CH₂CH₂R_f8)₂ (5) at 80°C (neat, 1 : 2 mol ratio) gives instead of simple substitution the metacyclophane [1,3-C₆H₄(CH₂P(CH₂CH ₂R_f8)₂CH₂-1,3-C₆H ₄CH₂P (CH₂CH₂R_f8) ₂CH₂]²⁺2Br, which upon treatment with LiAlH₄ yields 3-R_f8 (20%), 4-R_f8, and other products. Efforts to better access 3-R_f8, either by altering stoichiometry or using various combinations of the phosphine borane (H ₃B)PH(CH₂CH₂R_f8)₂ and base, are unsuccessful. Reactions of 3-R_fn with Pd(O ₂CCF₃)₂ and [IrCl(COE)₂]₂ (COE = cyclooctene) give the palladium and iridium pincer complexes (2,6,1-C₆H₃(CH₂P(CH₂CH ₂R_fn)₂)₂)Pd(O₂CCF ₃) (10-R_fn; 80-90%) and (2,6,1-C₆H ₃(CH₂P(CH₂CH₂R_f8) ₂)₂)Ir(Cl)(H) (11-R_f8; 29%), which exhibit CF₃C₆F₁₁/toluene partition coefficients of >96 : <4. The crystal structure of 10-R_f8 shows CH ₂CH₂R_f8 groups with all-anti conformations that extend in parallel above and below the palladium square plane to create fluorous lattice domains. NMR monitoring shows a precursor to 11-R_f8 that is believed to be a COE adduct. The Royal Society of Chemistry 2005.

Full text of DOI:10.1039/b502309b

View Article Online / Journal Homepage / Table of Contents for this issue
F U L L P A P E R
Synthesis, structure, and reactivity of fluorous phosphorus/
carbon/phosphorus pincer ligands and metal complexes†
R o´ bert Tuba, Verona Tesevic, Long V. Dinh, Frank Hampel and J. A. Gladysz*
Institut f u¨ r Organische Chemie, Friedrich-Alexander Universit a¨ t Erlangen-N u¨ rnberg,
Henkestraße 42, 91054, Erlangen, Germany
Received 15th February 2005, Accepted 19th May 2005
First published as an Advance Article on the web 9th June 2005
Reactions of the diphosphine 1,3-C
6
H
4
(CH
2
PH
2
)
2
and fluorous alkenes H
(CH P(CH
2
C=CHRfn (Rfn = (CF
2
)
n−1CF
3
; n = 6, 8) at
◦
75 C in the presence of AIBN give the title ligands 1,3-C
6
H
4
2
2
2
fn 2 2
CH R ) ) (3-Rfn) and byproducts
1
,3-C
6
H
4
(CH
3
)(CH
2
P(CH
2
CH
2
R
fn
)
2
) (4-Rfn) in 1 : 3 to 1 : 5 ratios. Workups give 3-Rfn in 4–17% yields. Similar results
◦
are obtained photochemically. Reaction of 1,3-C
6
H
4
(CH
2
Br)
2
and HP(CH
2
CH
2
R
f8
)
2
(5) at 80 C (neat, 1 : 2 mol
ratio) gives instead of simple substitution the metacyclophane [1,3-C
6
H
4
(CH
2
P(CH
2
CH
2
R
f8
)
2
CH
2
-1,3-C
6
H
4
CH P
2
2
+
−
(
CH
to better access 3-Rf8, either by altering stoichiometry or using various combinations of the phosphine borane
B)PH(CH CH and base, are unsuccessful. Reactions of 3-Rfn with Pd(O CCF and [IrCl(COE)
(COE =
cyclooctene) give the palladium and iridium pincer complexes (2,6,1-C (CH P(CH CH )Pd(O CCF
10-Rfn; 80–90%) and (2,6,1-C (CH P(CH CH )Ir(Cl)(H) (11-Rf8; 29%), which exhibit CF 11/toluene
partition coefficients of >96 : <4. The crystal structure of 10-Rf8 shows CH CH f8 groups with all-anti
2
CH
2
R
f8
)
2
CH
2
] 2Br , which upon treatment with LiAlH
4
yields 3-Rf8 (20%), 4-Rf8, and other products. Efforts
(
H
3
2
2
R
f8
)
2
2
3
)
2
]
2 2
6
H
3
2
2
2
R
fn
)
2
)
2
2
3
)
(
6
H
3
2
2
2
R
f8
)
2
)
2
3
6
C F
2
2
R
conformations that extend in parallel above and below the palladium square plane to create fluorous lattice domains.
NMR monitoring shows a precursor to 11-Rf8 that is believed to be a COE adduct.
Introduction
There has been dramatic growth in the use of pincer ligands
1
for transition metal catalysts over the last decade. This has in
turn prompted a variety of approaches to recoverable pincer
2
–10
ligands and complexes.
These include immobilization on
2
scaffolds such as large self-assembled hyperbranched spheres,
hyperbranched polyglycerol, and fullerenes, or supports such
as silica, PEG, carbosilane dendrimers, polyisobutylene, and
clays. Some efforts have involved fluorous derivatives, examples
of which are provided in Scheme 1. Fluorous compounds
are recoverable by a variety of techniques, as thoroughly
summarized in recent reviews. In the last few months, some
mechanistic caveats that bear upon the recyclability of certain
polymer-bound palladium sulfur/carbon/sulfur (SCS) pincer
3
4
5
6
7
8
9
10
11
12
catalyst systems have appeared.
We recently reported fluorous phosphapalladacycles and
sulfapalladacycles that were excellent catalyst precursors for
13
Heck and Suzuki couplings of aryl halides. However, these
merely served as steady-state sources of catalytically active
palladium nanoparticles under the conditions investigated. The
remaining fluorous palladacycles could be efficiently recycled,
but each cycle exhibited an induction period and activity
eventually ceased. We thought that tridentate fluorous phospho-
rus/carbon/phosphorus (PCP) pincer ligands might give more
stable palladium complexes better disposed towards molecular
catalysis. Our attention was also drawn to iridium PCP pincer
complexes, which are catalysts for another important class of
14
reactions, alkane dehydrogenations.
Scheme Representative fluorous pincer complexes (Rfn
1
=
(
CF )n−1CF ).
2 3
Accordingly, we set out to prepare fluorous PCP pincer
ligands of the general formula I, and develop their coordination
chemistry. Although compounds with aromatic rings are more
15
coefficients. In this paper, we report (1) three independent routes
to such ligands, (2) their facile metalation to give palladium
and iridium derivatives, and (3) a crystal structure of one
of the palladium derivatives. Some preliminary catalysis data
are also discussed. Companion efforts involving fluorous SCS
pincer ligands have also been initiated, and will be described
challenging to render highly fluorophilic, it was thought
that the four ponytails would provide very biased partition
†
Electronic supplementary information (ESI) available: Additional
experiments and details relevant to Scheme 3. See http://www.rsc.org/
suppdata/dt/b5/b502309b/
16
separately.
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
D a l t o n T r a n s . , 2 0 0 5 , 2 2 7 5 – 2 2 8 3
2 2 7 5

View Article Online
both fluorous and non-fluorous solvents, with the exception of
hexane.
Many experiments were conducted in efforts to increase the
3
-Rf8/4-Rf8 ratio. These included higher loadings of AIBN,
◦
other temperatures (70–100 C), alternative initiators (VAZO,
◦
80–100 C), and solvents such as THF or CF
3
C
6
5
H ((tri-
fluoromethyl)benzene). However, none were successful. Pho-
tochemical reactions of 1 and H
temperature or 0 C, gave similar yields of 3-Rf8 and 4-Rf8
2
C=CHRf8, either at room
◦
.
,
Thermal and photochemical reactions of 1 and H
2
C=CHRf6
which has a shorter ponytail, gave comparable yields of the
lower homologs 3-Rf6 and 4-Rf6. Thus, the formation of 4-Rfn
under free radical chain conditions is general, but its exact origin
remains mechanistically obscure. Hence, other approaches to 3-
Results
1
.
Fluorous pincer ligands via radical additions
In previous work, we have described many free radical chain
additions of R3−nPH species to fluorous terminal alkenes
Thus, our attention was drawn to the dipri-
R
fn were investigated.
n
2.
Fluorous pincer ligands via nucleophilic substitution
17
H
2
C=CHRfn
.
mary diphosphine 1,3-C
from a,a -dibromo-m-xylene or 1,3-C
Arbuzov/reduction sequence. As shown in Scheme 2, 1 and
H
radical initiator AIBN. The process was monitored by P NMR,
which showed a sequence of intermediates as the phosphorus–
hydrogen bonds reacted, and a signal appropriate for the tar-
6
H
4
(CH
2
PH
2
)
6
2
(1), which is available
(CH Br) (2) via an
Other groups have shown that the benzyl bromide 2 and/or sub-
stituted derivatives can be condensed with secondary phosphines
to give, after deprotonation, pincer ligands 1,3-C
in high yields. Thus, reactions of 2 and the fluorous secondary
phosphine HP(CH
products formed under homogeneous conditions in refluxing
acetone, toluene, and THF, or under heterogeneous conditions
ꢀ
H
4
2
2
18
6
H
4
(CH
2
PR
2
)
2
◦
20
C=CHRf8 were reacted neat at 75 C in the presence of the
2
3
1
21
2
CH
2
R
f8
)
2
(5-Rf8
)
were investigated. No
◦
get molecule 1,3-C
6
H
4
(CH
2
P(CH
2
CH
2
R
f8
)
2
)
2
(3-Rf8). Another
in DMF at 100 C, even at high concentrations. This is
species (4-Rf8) also formed, which was always the major product
when addition was complete. The 3-Rf8/4-Rf8 ratios ranged from
consistent with the diminished nucleophilicites often found
for fluorous nucleophiles, especially when only two methylene
groups separate the perfluoroalkyl segments and the reactive
17a
1
: 3 to 1 : 5. In some cases, small amounts of P(CH
2
CH
2
R )
f8 3
22
were noted. No other byproducts were detected.
In a few runs, 3-Rf8 was isolated in 15–17% yields. However,
site.
◦
Thus, as shown in Scheme 3, 2 (mp 75–77 C) and 5-Rf8
(mp 80 C) were intimately mixed in a 1 : 2 mol ratio, and
◦
in most cases only 4–5% yields were obtained, despite the
19
◦
high and quite clean NMR conversions to 3-Rf8 and 4-Rf8
.
heated to 80 C in the absence of solvent. The sample melted
Compounds 3-Rf8 and 4-Rf8 were air-sensitive white solids that
and resolidified, and was cooled. The product could not be
1
13
31
were characterized by NMR ( H, C, P) and microanalysis, as
summarized in the Experimental section. The NMR properties
dissolved in any common solvent, including THF, CF
3
C
6
F
11
(perfluoro(methylcyclohexane)) and CF . A FAB mass
3
C
6
H
5
20
of 3-Rf8 were very similar to those of other PCP pincer ligands.
Those of 4-Rf8, coupled with a mass spectrum, showed it to
be the monophosphine 1,3-C (CH )(CH P(CH CH ),
spectrum did not show any peak consistent with the dication
of the desired primary product, the bis(phosphonium salt) 6-
6
H
4
3
2
2
2
R
f8
)
2
R
f8 (Scheme 3; e.g. m/z 978.0 or 1956.0 for z = 2 or 1; 1955.0,
+ 23
allowing a yield of 35% to be calculated. Thus, 4-Rf8 is derived
from the cleavage of a benzylic carbon–phosphorus bond.
As summarized in Table 1, 3-Rf8 and 4-Rf8 were soluble in
dication − H ). However, a strong peak appropriate for the
dication of the metacyclophane 7-Rf8 (Scheme 3) was apparent
(m/z 1029.0 and 1029.5, z = 2, 100 : 67; calc. 100 : 63), as well
Scheme 2 Synthesis of fluorous pincer ligands 3-Rfn via free radical chain additions.
Table 1 Solubility profiles of selected compounds at room temperature
C
6
F
11CF
3
C
6
H
5
CF
3
Hexane
Diethyl ether
THF
CH
2
Cl
2
Acetone
3
4
3
4
9
1
1
1
-Rf8
-Rf8
-Rf6
-Rf6
High
High
High
High
High
Med
High
High
High
High
High
High
High
High
High
High
None
Low
Low
Low
Med
Low
Med
Low
Low
Low
Med
High
High
High
High
Med
Med
Med
Med
Med
Med
Med
Med
Low
Med
Med
Med
Med
Med
High
High
Low
Med
Med
Med
Low
-Rf8
None
None
None
Low
0-Rf8
0-Rf6
1-Rf8
2
2 7 6
D a l t o n T r a n s . , 2 0 0 5 , 2 2 7 5 – 2 2 8 3

View Article Online
Scheme 3 Synthesis of fluorous pincer ligand 3-Rf8 via nucleophilic substitutions.
the idea that it might be possible to isolate 8-Rf8. Excess 2 was
as a slightly more intense peak for a related monocation (m/z
3
1
2
057.6).
removed, and base was added. However, no P NMR signal
was observed in the region expected for the monophosphine
We sought to salvage the inauspicious start in Scheme 3. The
carbon–phosphorus bonds of phosphonium salts can often be
1,3-C
6
H
4
(CH
2
Br)(CH
2
P(CH
2
CH
2
R
f8
)
2
) (−18 to −22 ppm).
24
cleaved reductively. One common protocol involves LiAlH
4
.
The proton transfer equilibria and polyalkylations that plague
Scheme 3 should be eliminated with phosphorus nucleophiles
that lack hydrogen substituents, and can be alkylated only once.
The most obvious candidate would be an anion derived from the
The benzylic linkages in 7-Rf8 should be more reactive, and two
products—the target pincer ligand 3-Rf8 and the monophos-
phine byproduct 4-Rf8—would be possible. Thus, the residue was
treated with a slight excess of LiAlH
gave 3-Rf8 in 20% overall yield from 2. The P NMR spectrum of
4
. Column chromatography
fluorous secondary phosphine borane (H
3
B)PH(CH CH
2
26a
2
R
f8
)
2
3
1
21b,26,27
(9-Rf8).
Following an established procedure,
9-Rf8
,
the crude reaction mixture showed a number of byproducts, with
KOH, and 2 were combined in ethanol. After several days,
workup and removal of the borane protecting group with HNEt
3-Rf8 representing 45% of the integral trace. These included 4-
2
R
H
f8, the secondary phosphine 5-Rf8, and the primary phosphine
gave mainly 5-Rf8, and only traces of the target pincer ligand 3-
21a
◦
2
PCH
2
CH
2
R
f8
,
all of which eluted faster than 3-Rf8 from the
R
f8. Similar sequences involving t-BuOK or n-BuLi (−78 C)
column.
and THF were also unsuccessful, and additional details are
provided in the ESI.†
A variety of other conditions were investigated in hope
of increasing the yield of 3-Rf8. The first-formed species in
Scheme 3 must be the monophosphonium salt 8-Rf8. A higher
concentration of 5-Rf8 should increase the rate of displacement
of the remaining benzylic bromide to give 6-Rf8. However,
reactions using 1 : 4 mol ratios of 2 and 5-Rf8 gave nearly
3. Metal derivatives of fluorous pincer ligands
Despite the modest yields of the fluorous pincer ligands
3-Rfn in Schemes 2 and 3, the masses isolated are commonly
greater than the masses of the educts 1 or 2. Thus, some
coordination chemistry could be developed. As shown in
25
identical results. In order to generate the metacyclophane 7-
f8, the deprotonation of 8-Rf8 (or 6-Rf8) is required. Hence,
R
these results suggest that proton transfer from 8-Rf8 to 5-Rf8 is
intrinsically faster than the displacement of bromide. Reactions
were also conducted with 10 : 1 mol ratios of 2 and 5-Rf8, with
Scheme 4, the trifluoroacetate complex Pd(O
2
CCF
3
)
2
and 3-
R
f6 or 3-Rf8 were combined in THF. In accord with much pre-
1
cedent, workup gave the air-stable palladium pincer complexes
Scheme 4 Metal complexes of fluorous pincer ligands 3-Rfn
.
D a l t o n T r a n s . , 2 0 0 5 , 2 2 7 5 – 2 2 8 3
2 2 7 7

View Article Online
◦
Table 2 Selected bond lengths [ A˚ ], bond angles [ ], and intermolecular
contacts [ A˚ ] for 10
(
9
(
2,6,1-C
6
H
3
(CH
2
P(CH
2
CH
2
R
fn
)
2
)
2
)Pd(O
2
CCF
3
) (10-Rfn) in 80–
0% yields. These were characterized by microanalysis, NMR
1
13
31
H, C, P), and mass spectrometry, as described in the Exper-
31
Pd(1)–C(11)
Pd(1)–O(1)
Pd(1)–P(1)
Pd(1)–P(2)
P(1)–C(12a)
P(1)–C(21)
P(1)–C(31)
P(2)–C(16a)
P(2)–C(41)
2.008(11)
2.126(9)
2.275(3)
2.298(3)
1.817(12)
1.834(11)
1.830(10)
1.825(13)
1.829(12)
P(2)–C(51)
1.832(13)
1.393(16)
1.417(15)
1.508(16)
1.394(15)
1.382(17)
1.382(18)
1.370(16)
1.522(17)
imental section. The P NMR chemical shifts were ca. 60 ppm
downfield of the free ligands. One aryl C NMR signal was a
triplet, and was assigned to the palladium-bound carbon. The
C(11)–C(12)
C(11)–C(16)
C(12A)–C(12)
C(12)–C(13)
C(13)–C(14)
C(14)–C(15)
C(15)–C(16)
C(16)–C(16A)
1
3
28
PCH signals gave apparent triplets due to virtual coupling.
2
As summarized in Table 1, 10-Rf6 and 10-Rf8 were soluble in
most fluorous and non-fluorous solvents at room temperature.
Although hexane was an exception, solubilities in hot hexane
were appreciable. When such solutions of 10-Rf8 were slowly
cooled, single crystals were obtained. X-Ray data were collected
as described in the Experimental section. Refinement gave the
molecular structure depicted in Fig. 1. One fluorine atom (F46A)
showed disorder that could not be resolved. Key bond lengths
and angles are given in Table 2. They are generally close to those
C(11)–Pd(1)–O(1)
C(11)–Pd(1)–P(1)
O(1)–Pd(1)–P(1)
C(11)–Pd(1)–P(2)
O(1)–Pd(1)–P(2)
P(1)–Pd(1)–P(2)
O(1)–C(1)–O(2)
O(1)–C(1)–C(2)
Pd(1)–P(1)–C(21)
Pd(1)–P(1)–C(31)
173.2(4)
83.6(3)
89.9(3)
Pd(1)–P(1)–C(12a)
Pd(1)–P(2)–C(41)
Pd(1)–P(2)–C(51)
Pd(1)–P(2)–C(16a)
C(21)–P(1)–C(31)
C(21)–P(1)–C(12a)
C(31)–P(1)–C(12a)
C(41)–P(2)–C(51)
C(41)–P(2)–C(16a)
C(51)–P(2)–C(16a)
103.5(4)
119.6(4)
116.4(4)
102.7(4)
104.2(5)
109.2(6)
105.7(5)
105.5(6)
107.2(6)
104.0(6)
84.0(3)
102.7(3)
166.98(12)
132.1(18)
111(2)
116.8(4)
116.8(4)
26b,29
found in other neutral palladium PCP pincer complexes.
The ponytails exhibit anti C–C–C–C conformations, with
the torsion angles of the anti F–C–C–F segments averaging
◦
30
1
76.1 . One ponytail on each phosphorus atom extends above
the palladium square plane, and the other below. Both run
parallel to the ponytails on the trans phosphorus atom, which
F(24b)–F(44a)
F(26b)–F(46a)
F(28b)–F(48a)
F(34b)–F(54a)
F(36b)–F(56a)
2.987
2.743
2.716
2.715
2.744
F(38b)–F(58a)
F(33a)–F(58b)
F(35a)–F(56b)
F(37a)–F(54b)
2.827
2.932
2.981
2.932
are nearly in van-der-Waals contact (Fig. 1, bottom). As can be
seen in Fig. 2, the crystal lattice is divided into fluorous and non-
fluorous domains, with the ponytails of neighboring molecules in
comparable van-der-Waals contact. Other square planar metal
31
complexes with fluorous phosphines crystallize similarly. The
32
˚
van-der-Waals radius of fluorine is 1.40 A, and some of the
shorter fluorine–fluorine distances are included in Table 2.
3
3
The iridium bis(cyclooctene) complex [IrCl(COE)
2
]
2
has
Thus, 3-Rf8
were reacted in THF at 80 C. As shown in
Scheme 4, workup gave the expected iridium(III) complex (2,6,1-
(CH P(CH CH )Ir(Cl)(H) (11-Rf8) in 29% yield.
20d,34
often been used to prepare pincer complexes.
◦
and [IrCl(COE)
]
2 2
C
6
H
3
2
2
2
R
f8
)
)
2 2
Complex 11-Rf8 was characterized analogously to 10-Rf8, and
its solubility characteristics and many NMR properties were
similar. However, due to the trigonal pyramidal geometry and
unsymmetrical equatorial substitution pattern, the ponytails
1
3
on each phosphorus become diastereotopic, and separate
C
signals were observed. The hydride ligand gave a characteristic
1
Fig. 1 Molecular structure of the fluorous palladium pincer complex
upfield H NMR signal (−25.3 ppm) that was coupled to both
1
0-Rf8
.
phosphorus atoms.
Fig. 2 Packing diagram for 10-Rf8
.
2
2 7 8
D a l t o n T r a n s . , 2 0 0 5 , 2 2 7 5 – 2 2 8 3

View Article Online
The reaction of 3-Rf8 and [IrCl(COE)
2
]
2
was monitored
with free radical chain additions of the diprimary diphosphine
1, at least with respect to fluorous terminal alkenes. In other
1
by NMR in [D ]THF. As shown in Fig. 3, the H signals
8
of 3-Rf8 disappeared over the course of a few hours. Two
triplets for iridium hydride ligands appeared. The more intense
triplet (−24.2 ppm) was due to an intermediate and gradually
disappeared as the other, arising from 11-Rf8, intensified. This
species was also evident in the P NMR spectrum, and was
tentatively assigned as the octahedral cyclooctene complex
exploratory experiments, 1 was treated with excesses of the
◦
fluorous alkyl iodides ICH
2
CH
2
R
fn (n = 6, 8) at 70 C in
35
22
DMF. However, these are weaker alkylating agents, and
no reactions occurred. Importantly, there are only a limited
number of possible retrosynthetic pathways to 3-Rfn, and the
most obvious candidates have been thoroughly examined in this
study. Hence, in order to realize convenient, high-yield syntheses,
new reaction technologies will likely be required.
3
1
1
2-Rf8 (Scheme 4). A closely related dihydride complex has
34a
been previously characterized by NMR.
Hence, the rate
determining step in the formation of 11-Rf8 is not carbon–
hydrogen bond activation, but rather a simple dissociation of an
alkene ligand. Although Fig. 3 gives the impression of a clean
reaction, some insoluble brown material formed concurrently.
Thus, the modest isolated yield of 11-Rf8 is not due solely to
workup losses.
Nonetheless, when fluorous ponytails are grafted onto 1
or 2, their masses greatly increase. The quantities of 3-Rfn
thus available allowed both palladium and iridium complexes
to be prepared (Scheme 4), the former in particularly good
yield. Several palladium PCP pincer complexes are effective
36
catalyst precursors for Heck alkenylations of aryl halides.
Thus, some exploratory reactions were conducted with 10-Rf8
using (i-Pr) NEt as the base. Material that had been isolated
,
2
by extraction was quite active catalytically. However, material
that had been purified by column chromatography was nearly
inactive. This underscores the importance of removing trace
impurities, a task that in the case of fluorous catalysts is usually
facilitated by their phase properties.
Furthermore, the mechanisms of Heck reactions promoted
by immobilized palladium SCS pincer complexes have recently
12
been studied in detail. Many careful experiments establish
that these complexes merely serve as precursors for pincer-free
palladium(0) species that are likely non-molecular, and which
constitute the active catalysts. Our own preliminary data with
fluorous palladium SCS pincer complexes are best modeled
16
similarly. It would not be surprising if such mechanisms apply
12,36d
to all palladium SCS and PCP pincer complexes.
Hence,
we became much less enthusiastic about testing 10-Rfn as a
recoverable catalyst or catalyst precursor for any type of aryl
halide coupling. However, palladium PCP pincer complexes
5b,29b,37
catalyze other types of reactions,
and here 10-Rfn remain
viable candidates for recyclable molecular catalysts.
The mechanisms of alkane dehydrogenations catalyzed by
iridium PCP pincer complexes have also been studied in
14,34a,38
detail.
In contrast to some of the palladium systems
described above, these are clearly molecular catalysts. However,
monohydride chloride complexes such as 11-Rf8 are not active.
Rather, dihydride complexes such as 13-Rf8 (Scheme 4) are
commonly employed to enter the catalytic cycle. Although
14,26b,34b
LiEt BH is often used to displace such chloride ligands,
3
Fig. 3 NMR monitoring of the reaction of 3-Rf8 and [IrCl(COE)
2
]
2
◦
we were never able to effect a clean conversion to 13-Rf8. NMR
data suggested the formation of polyhydride species (e.g., 14-
(
[D
8
]THF, 80 C) to give the transient 12-Rf8 and iridium fluorous pincer
complex 11-Rf8
.
R
f8), and optimizations were limited by the quantity of 11-Rf8
available.
As illustrated in Table 1, the new fluorous PCP pincer
Finally, the CF
3
C F11/toluene partition coefficients of 10-Rf8
6
19
and 11-Rf8 were measured by HPLC and F NMR, as described
in the Experimental section. Quite high fluorophilicities were
observed (96.4 : 3.6, 98.0 : 2.0), which are further analyzed below.
ligands and metal complexes are soluble in both fluorous and
non-fluorous solvents. However, 10-Rf8 and 11-Rf8 have quite
biased CF
3
C
6
F
11/toluene partition coefficients (>96 : <4), even
groups per Rf8
though they contain an aryl ring, 2.5 CH
2
Discussion
segment, and auxiliary ligands. These values are in the range of
dimeric phosphapalladacycles that contain three Rf8 ponytails
This study has shown that the fluorous PCP pincer ligands 3-Rfn
can be synthesized in only a few steps (Schemes 2, 3), and are
readily metalated (Scheme 4). However, all routes to 3-Rfn feature
one step where the isolated yield is low. Although spectroscopic
yields are somewhat higher, in no case do they approach those
of the non-fluorous counterparts. The latter are usually accessed
via reactions of phosphorus nucleophiles with the dibromide 2.
Syntheses of “heavy” fluorous analogs often present additional
challenges, and the diminished nucleophilicities of our fluorous
phosphines and related anions are likely responsible for at least
some of the difficulties in Scheme 3. Perhaps analogs with longer
insulating methylene segments would give cleaner chemistry.
Surprisingly, the major product under either thermal or
photochemical conditions in Scheme 2 is the monophosphine
13
per arene ring. Fluorophilicities might be further increased
by incorporating additional ponytails, such as in the silyl-
substituted complexes in Scheme 1, or by lengthening existing
Rfn segments, such as with Rf10 analogs. Partition coefficients
for the pincer complexes in Scheme 1 are not available, but the
palladium SCS species is easily recovered by a fluorous solid
10c
phase extraction.
In accord with the trend for 3-Rf6 and 3-Rf8 in Table 1,
lengthening the Rfn segments of our complexes is certain to
decrease their absolute solubilities. Indeed, one very promis-
ing direction for fluorous catalysis involves thermomorphic
species with very little or no solubility in non-fluorous sol-
vents at room temperature, but appreciable solubilities at ele-
39–42
4-Rfn. This indicates that there are intrinsic problems associated
vated temperatures.
This allows catalyst recovery by simple
D a l t o n T r a n s . , 2 0 0 5 , 2 2 7 5 – 2 2 8 3
2 2 7 9

View Article Online
◦
liquid/solid phase separations. The highly temperature-
dependent solubility of 10-Rf8 in hexane suggests considerable
promise for PCP pincer complexes derived from fluorous ligands
I. Also, the high temperature required for alkane dehydrogena-
tion by iridium PCP pincer complexes makes for an ideal test
reaction.
(0.500 g, 3.045 mmol), and placed in a 75 C bath. The mixture
was stirred (6 h), cooled, and filtered through a silica gel plug
(3.0 × 1.5 cm) that was rinsed with hexanes/CF
3
C
6
5
H (4 :
1 v/v, 100 mL). The volatiles were removed from the filtrate
by oil pump vacuum. The yellowish oil was chromatographed
on silica gel (20 × 3 cm column; packed in hexanes) with
In summary, expedient syntheses of fluorous PCP pincer lig-
ands have been developed. However, in contrast to non-fluorous
analogs, one low-yield step cannot be avoided. Nonetheless,
palladium and iridium complexes have been prepared, and
their structures and reactions characterized. Future papers will
describe more readily accessible fluorous SCS pincer ligands that
hexanes/CF
3
C
6
H
5
(7 : 1 v/v, 800 mL; then 4 : 1 v/v,
31
19
500 mL). The fractions were monitored by P NMR, and
the solvents were removed by oil pump vacuum. The earlier cuts
(300–450 mL) gave 1,3-C
6
H
4
(CH
3
)(CH
2
P(CH
2
CH
2
R
f8
)
2
) (4-Rf8;
2.204 g, 2.140 mmol, 35%), and the later cuts (550–1000 mL) 3-
f8 (0.510 g, 0.261 mmol, 4%), both as air sensitive white solids.
R
16
contain two ponytails per arene ring, and palladium complexes
that give non-molecular catalysts for Heck reactions, as noted
Method B. A photochemical immersion well reactor was
charged with 1 (1.527 g, 8.980 mmol), H C=CHR (24.6 g,
2
f8
12
for related species above.
56.0 mmol), and AIBN (0.100 g, 0.609 mmol). The mixture was
irradiated with a Heraeus TQ 150 medium pressure mercury
lamp (6 h). Workup as in method A gave 4-Rf8 and 3-Rf8 (0.851 g,
Experimental
0
.436 mmol, 5%).
General
Method C. A Schlenk flask was charged with HP-
4.520 g, 4.880 mmol) and 2 (0.612 g,
2.32 mmol), which were intimately mixed. The flask was placed
in a 55 C oil bath, and warmed to 75 C over 0.5 h. The mixture
melted, and was stirred with a stir bar until it solidified again.
The flask was warmed to 80 C over a few minutes. After 1 h
total, the mixture was cooled and THF (100 mL) was added. The
solid product was triturated to a sand-like suspension and cooled
(0.0660 g, 1.74 mmol) was added with
stirring. The mixture was slowly warmed to room temperature.
After 3 h, the mixture was cooled to 0 C and aqueous NaOH
3.0 M) was slowly added. After a few minutes, the mixture was
21
(CH
2
CH
2
R
f8
)
2
(5-Rf8
;
Reactions were, unless noted otherwise, conducted under
◦
N
2
with glassware that had been oven-dried (110 C), as-
◦
◦
sembled while warm, and cooled under vacuum. Chemicals
were treated as follows: THF, diethyl ether, hexanes, and
toluene, distilled from Na/benzophenone; ethanol, distilled
◦
from CaH
2
; CF
(Fluka), freeze–pump–thaw degassed; H
C=CHRf8, Pd(O
CCF (3 × ABCR), 1,3-C
2), LiAlH
, AIBN (3 × Aldrich), BH
1.6 M in hexane), C , [D ]THF, [D
3
C
6
F
5
, distilled from P
2
O
5
; CF
3
C F11 (ABCR)
6
and HNEt
2
2
C=CHRf6
,
2
◦
to 0 C. Then LiAlH
4
H
2
2
3
)
2
6
H
4
(CH
2
Br)
(
(
4
3
(1 M in THF), n-BuLi
◦
6
D
6
8
6
]DMSO, (5 × Acros),
(
and KOH (Gr u¨ ssing Gmbh), used as received. Silica gel (Merck
grade 9385, 230–400 mesh) was dried at 110 C and 0.02 Torr
◦
filtered through MgSO . The solvent was removed by oil pump
4
vacuum. Then CF
chromatography as in method A gave 3-Rf8 (0.938 g, 0.480 mmol,
0%).
Data for 3-R . mp 63 C. Calc. for C H F P : C 29.48; H
3
C
6
H
5
(5–10 mL) was added, and column
(
24 h).
NMR spectra were recorded on Bruker 300 or 400 MHz
spectrometers at ambient probe temperature and referenced
2
◦
1
as follows: H, residual internal [D
C
(
C
on ASI React-IR 1000 and Micromass Zabspec instruments,
respectively. DSC and TGA data were recorded with a Mettler-
Toledo DSC821 apparatus and treated by standard methods.
7
]THF (d 1.73, 3.58) or
f8
48
24 68
2
1
1
3
1.23; Found: C 29.74; H 1.14%. NMR (d, [D ]THF): H 1.72
(m, 4H, CH CH CF ), 2.22 (m, 4H, CH CH CF ), 2.95 (s, 4H,
D
5
H (d 7.16); C internal [D
8
]THF (d 25.37, 67.57) or C
(d = 0.00 ppm); F, internal
6
D
6
8
6
3
1
19
d 128.39); P, external H
3
PO
4
2
2
2
2
2
2
ArCH
t, JHH = 7.6 Hz, 1H, Ar); C{ H} 17.8 (d, JCP = 16.1 Hz,
CH CH CF ), 28.6 (m, CH CH CF
), 35.1 (d, JCP = 17.6 Hz,
2
), 7.06 (d, JHH = 7.6 Hz, 2H, Ar), 7.10 (s, 1H, Ar), 7.22
6
F
6
(d = −162.0 ppm). IR and mass spectra were recorded
13 1
(
2
2
2
2
2
2
43
ArCH ), 127.8 (d, J = 5.1 Hz, Ar), 129.7 (s, Ar), 130.2 (t, J
=
2
CP
CP
3
1
1
5
.9 Hz, Ar), 138.1 (d, JCP = 2.9 Hz, Ar); P{ H} −19.4 (s).
Elemental analyses were conducted on a Carlo Erba EA1110
instrument.
◦
Data for 4-Rf8. mp 55 C. Calc. for C28
H F34P: C 32.64; H
17
1
1
.66; Found: C 32.63; H 1.83%. NMR (d, C
6
D ): H 1.59 (m, 4H,
6
18
1
,3-C
6
H
4
(CH
2
PH
2
)
2
(1) . A Schlenk flask was charged with
CH CH CF ), 2.04 (m, 4H, CH CH CF ), 2.30 (s, 3H, ArCH ),
2
2
2
2
2
2
3
LiAlH
4
(5.56 g, 147 mmol) and diethyl ether (25 mL) and
2.70 (s, 2H, ArCH ), 6.87 (d, J = 7.6 Hz, 2H, Ar), 6.91 (s,
13 1
CP
2
HH
◦
cooled to −20 C. Another Schlenk flask was charged with 1,3-
1H, Ar), 7.07 (t, JHH = 7.6 Hz, 1H, Ar); C{ H} 18.0 (d, J
=
2
18b
C
6
H
4
(CH
2
P(=O)(OCH
2
CH
3
)
2
)
2
(22.00 g, 66.63 mmol) and
17.6 Hz, CH CH CF ), 20.7 (s, ArCH ), 28.8 (m, CH CH CF ),
2
2
2
3
2
2
diethyl ether (75 mL). This solution was slowly cannulated into
the first flask with stirring. The mixture was allowed to warm
to room temperature over several hours, stirred overnight, and
35.3 (d, JCP = 17.6 Hz, ArCH ), 126.4 (d, J = 5.9 Hz, Ar),
2
CP
127.6 (d, JCP = 2.9 Hz, Ar), 129.1 (s, Ar), 130.2 (d, J = 5.1 Hz,
CP
Ar), 137.1 (d, J = 3.7 Hz, Ar), 139.4 (d, J = 1.5 Hz, Ar);
CP
CP
◦
3
1
1
23
cooled to 0 C. A degassed solution of saturated aqueous NaOH
P{ H} −22.0 (s). MS (FAB, 3-NBA), m/z (%): 1031 (60)
+ + +
f8 2 2 f8
was slowly added via cannula with vigorous stirring, until the
formation of a white precipitate was complete. The ether layer
[M] , 611 (10) [M − R ] , 583 (10) [M − CH CH R ] .
1
,3-C
6
H
4
(CH
2
P(CH
2
CH
2
2
R
f6
)
2
)
2
(3-Rf6). Compounds
1
was transferred under N
white aqueous layer was further extracted with diethyl ether
),
2
to a flask charged with MgSO . The
4
(
0.501 g, 2.94 mmol), H
C=CHRf6 (6.105 g, 17.65 mmol) and
AIBN (0.121 g, 0.735 mmol) were reacted in a manner analogous
(
2 × 50 mL). The ether layers were combined, dried (MgSO
4
to method A for 3-Rf8. An identical filtration and chromato-
and concentrated by oil pump vacuum. The crude opaque oil
19
graphic workup gave 1,3-C
f6; 0.733 g, 0.882 mmol, 30%) and 3-Rf6 (0.503 g, 0.324 mmol,
11%). as air sensitive clear colorless oils.
Data for 3-Rf6. NMR (d, ):
CH CH CF ), 2.11 (m, 4H, CH CF
6
H
4
(CH
3
)(CH
2
P(CH
2
CH
2
R
f6
2
) ) (4-
was distilled (Kugelrohr) to give 2 as a clear, strong-smelling oil
R
(
5.670 g, 33.35 mmol, 50%). Calcd for C
.11. Found: C, 56.30; H, 7.34%. NMR (d, C
8
H
12
P : C, 56.48; H,
2
1
7
4
6
7
(
1
6
D
6
): H 2.44 (m,
),
1
C
6
D
6
H
1.69 (m, 4H,
H, PH
2
), 2.84 (td, JHH = 7.6 Hz, JPH = 191.7 Hz, 4H, ArCH
2
.75 (d, JHH = 5.6 Hz, 2H, Ar), 6.77 (s, 1H, Ar), 6.99 (t, JHH
=
2
2
2
2
CH
2
2
), 2.79 (s, 4H, ArCH ),
2
1
3
1
7.02 (d, JHH = 7.6 Hz, 2H, Ar), 7.07 (s, 1H, Ar), 7.23 (t, J
=
.6 Hz, 1H, Ar); C{ H} 20.9 (d, JPC = 11.2 Hz, ArCH
2
), 125.1
HH
1
3
1
7
.6 Hz, 1H, Ar); C{ H} 17.5 (d, JCP = 16.1 Hz, CH
2
CH
2
CF ),
2
s, Ar), 127.4 (t, JPC = 14 Hz, Ar), 128.8 (t, JPC = 16.4 Hz, Ar),
3
1
1
28.4 (m, CH CH CF ), 34.6 (d, J = 17.6 Hz, ArCH ), 127.7
29.1 (s, Ar); P{ H} − 121.9 (s).
,3-C (CH P(CH CH
Method A. A Schlenk flask was charged with 1 (1.079 g,
2
2
2
CP
2
(
d, JCP = 5.1 Hz, Ar), 129.6 (s, Ar), 130.5 (t, JCP = 5.9 Hz, Ar),
31 1
CP
1
6
H
4
2
2
2
R
f8
)
2
)
2
(3-Rf8).
138.1 (d, J = 2.9 Hz, Ar); P{ H} −21.5 (s).
1
Data for 4-Rf6. NMR (d,
C
6
D
6
):
H
1.59 (m, 4H,
6
.350 mmol), H
C=CHRf8, (17.0 g, 38.1 mmol), and AIBN
2
CH
2
CH
2
CF
2
), 2.04 (m, 4H, CH
2
CH
2
CF
2
), 2.38 (s, 3H, ArCH ),
3
2
2 8 0
D a l t o n T r a n s . , 2 0 0 5 , 2 2 7 5 – 2 2 8 3

View Article Online
2
1
1
3
1
.75 (s, 2H, ArCH
H, Ar), 7.07 (t, JHH = 7.6 Hz, 1H, Ar); C{ H} 18.0 (d, JCP
7.6 Hz, CH CH CF ), 20.7 (s, ArCH ), 29.0 (m, CH CH CF
5.3 (d, JCP = 17.6 Hz, ArCH ), 126.4 (d, JCP = 5.9 Hz, Ar),
27.6 (d, JCP = 2.9 Hz, Ar), 129.1 (s, Ar), 130.2 (d, JCP = 5.1 Hz,
2
), 6.87 (d, JHH = 7.6 Hz, 2H, Ar), 6.91 (s,
Method B. An NMR tube was charged with 3-Rf8 (0.031 g,
1
3
1
=
0.055 mmol) and a solution of [IrCl(COE)
2
]
2
(0.025 g,
2
2
2
3
2
2
2
),
0.030 mmol) in [D
was tightly closed and immersed in an oil bath (80 C). Data:
Fig. 3.
8
]THF (0.7 mL) in a glove box. The tube
◦
2
◦
Ar), 137.1 (d, JCP = 3.7 Hz, Ar), 139.5 (d, JCP = 1.5 Hz, Ar);
Data for 11-R . mp 98 C. Calc. for C H ClF IrP : C
f8
48
24
68
2
3
1
1
−1
P{ H} − 22.6 (s).
26.40; H 1.10; Found: C 26.44; H 1.15%. IR (cm , powder
film): mIr–H 2200 (vw). NMR (d, [D
4.6 Hz, 1H, IrH), 2.17 (m, 4H, CH
1
8
]THF): H −25.3 (t, JPH
CH CF ), 2.49 (m,
CF ), 3.02 (m, 4H,
), 6.66 (t, JHH
=
(
2,6,1-C
Schlenk flask was charged with 3-Rf6 (0.275 g, 0.177 mmol),
THF (10 mL) and Pd(O CCF (0.058 g, 0.18 mmol). The
6
H
3
(CH
2
P(CH
2
CH
2
R
f6
)
2
)
2
)Pd(O
2
CCF
3
) (10-Rf6).
A
1
4
2
2
2
ꢀ
ꢀ
ꢀ
H, C H
2
C H
2
C F
2
), 2.88 (m, 4H, CH
2
2
2
)
3 2
ꢀ
ꢀ
C H
2
C F
2
), 3.80 (d, JPH = 13.2 Hz, 4H, ArCH
2
=
1
mixture was stirred. After 10 h, the solvent was removed by
oil pump vacuum. The orange solid was chromatographed on
silica gel (20 cm × 2 cm column packed in hexanes) with
1
3
7
1
t,
.3 Hz, 1H, Ar), 6.82 (d, JHH = 7.3 Hz, 2H, Ar); C{ H}
28
7.1 (virtual t,
J
CP = 13.2 Hz, CH
2
CH
), 26.9 (t, JCF = 22.4 Hz,
C F ), 38.9 (virtual t,
), 123.0 (t, JCP = 8.5 Hz, Ar), 124.4
2
CF ), 18.3 (virtual
2
2
8
ꢀ
ꢀ
ꢀ
J
CP = 15.5 Hz, CH
2
CH
2
CF
2
CF
3
C
6
5
H /hexanes (1 : 4 v/v). The solvent was removed from
ꢀ
ꢀ
28
C‘H
2
C F
2
), 27.9 (t, JCF = 22.6 Hz, C‘H
2
2
the product-containing fraction by oil pump vacuum to give
0-Rf6 (0.250 g, 0.142 mmol, 80%) as a white solid.
J
(
2
(
CP = 17.4 Hz, ArCH
2
1
3
1
1
s, Ar), 138.5 (m, Ar), 145.8 (t, JCP = 8.5 Hz, Ar) P{ H}
◦
◦
◦
Data for 10-Rf6. mp 63 C (capillary), 60.7 C (DSC, en-
1
9
6.0 (s); F −122.2 (CF
(CF CF
77.1 (CF ). MS (FAB, 3-NBA), m/z (%): 2181 (30) [M] ,
2
CF
3
), −119.5 (CF
2
CF
2
CF
3
), −118.7
dotherm, T
C
NMR (d, C
e
). TGA, onset of mass loss 174.6 C. Calc. for
CF
2
2
)
2
3
, −117.7 (CH
2
CF (CF
2
2
)
3
), −110.5 (CH
2
CF ),
2
42
H
24
F
55
O
2
P Pd. C 28.44; H 1.36; Found: C 28.42; H 1.90%.
2
23
+
−
3
1
ꢀ
ꢀ
6
D
6
): H 1.63 (m, 4H, CHH CHH CF
2
), 1.96 (m,
), 2.57 (m, 4H,
), 6.79
+
+
2
146 (75) [M − Cl] , 1987 (100) [M − Ir] .
ꢀ
ꢀ
ꢀ
4
H, CHH CHH CF
2
), 2.44 (m, 4H, CHH CF
2
ꢀ
28
CHH CF
2
), 2.71 (virtual t, J = 4.3 Hz, 4H, ArCH
2
Partition coefficients
(
d, J1HH = 7.5 Hz, 2H, Ar), 6.94 (t, JHH = 8.0 Hz, 1H, Ar);
28
2 2 2
1
3
C{ H} 17.3 (virtual t, J = 13.5 Hz, CH
CH
CF
), 28.0 (m,
), 124.4 (t,
Method A. A 10 mL vial was charged with 10-R (0.0112 g,
f8
28
CH
2
CH
2
CF
2
), 38.3 (virtual t, J = 13.2 Hz, ArCH
2
0.00515 mmol), CF C F (2.000 mL), and toluene (2.000 mL),
3
6
11
J = 11.1 Hz, Ar), 127.2 (s, Ar), 149.3 (t, J = 10.1 Hz, Ar), 152.7
fitted with a mininert valve, and vigorously shaken (2 min). After
3
1
1
23
◦
(
(
s, Ar); P{ H} 40.6 (s). MS (FAB, 3-NBA), m/z (%): 1659
2 h (24 C), a 0.200 mL aliquot of the fluorous phase and a
+
100), [M − OCOCF
3
] .
0.800 mL aliquot of the non-fluorous phase were removed. The
solvents were evaporated and the residues dried by oil pump
(
2,6,1-C
Schlenk flask was charged with 3-Rf8 (0.195 g, 0.100 mmol), THF
10 mL), and Pd(O CCF (0.034 g, 0.10 mmol). The mixture
6
H
3
(CH
2
P(CH
2
CH
2
R
f8
)
2
)
2
)Pd(O
2
CCF
3
) (10-Rf8).
A
vacuum (1 h). Each residue was dissolved in CF
3
C
6
F11/EtOH
(
9 : 1 v/v; 0.500 mL) and analyzed by HPLC (average of 5
(
2
◦
)
3 2
injections, 200 × 4 mm Nucleosil 100 − 5 column, UV/visible
detector). The relative peak intensities were, after normalization
to the aliquot volumes, 96.4 : 3.6.
was warmed to 80 C. After 5 h, the solution was cooled and
the solvent removed by oil pump vacuum. The orange solid
was dissolved in CF
20 cm × 2 cm column packed in 4 : 1 v/v CF
with CF /CH Cl (1 : 1 v/v). The eluate was monitored by
3
C
6
H
5
and chromatographed on silica gel
(
3
C
6
H
5
/CH Cl
2
2
)
Method B. A 10 mL flask was charged with 11-R (0.0620 g,
f8
3
C
6
H
5
2
2
0.0284 mmol) and CF C F (3.00 mL). After complete dis-
3
6
11
TLC. Solvent was removed from the product-containing fraction
by oil pump vacuum to give spectroscopically pure 10-Rf8 as a
light yellow solid (0.200 g, 0.093 mmol, 90%). Recrystallization
from hot hexanes gave 10-Rf8 (0.099 g, 0.046 mmol, 46%) as
colorless prisms.
solution, toluene (3.00 mL) was added and the sample was
vigorously shaken (20 min). After 48 h (25 C), 0.500 mL
◦
aliquots were removed from each layer. The CF C F aliquot
3
6
11
was evaporated to dryness. A solution of the internal standard
C F (0.1010 g, 0.5430 mmol) in CF C H (13.4448 g) was
6
6
3
6
5
◦
◦
Data for 10-Rf8. mp 83 C (capillary), 65.4 C (DSC, en-
prepared. Portions of this solution were added gravimetrically to
the aliquots (CF C F : 0.7150 g solution, 0.02870 mmol C F ;
◦
dotherm, T
e
). TGA, onset of mass loss 254.7 C. Calc. for
3
6
11
6
6
C
50
H
23
F
71
1
O
2
P
2
Pd: C 27.65; H 1.07; Found: C 27.67; H 1.09%.
toluene: 0.0633 g solution, 0.00254 mmol C F ), followed by
6
6
−
1
19
IR (cm , powder film): mCO 1690 (m). NMR (d, C
6
D
6
): H 1.67
[D ]THF (0.05 mL). F NMR spectra were recorded. The area
8
ꢀ
ꢀ
ꢀ
ꢀ
(
(
m, 4H, CHH CHH CF
2
), 2.01 (m, 4H, CHH CHH CF
2
), 2.29
of the (CF ) CF signal was integrated versus that of C F . The
2
7
3
6
6
ꢀ
ꢀ
m, 4H, CHH CF
2
), 2.50 (m, 4H, CHH CF
2
), 2.71 (virtual
procedure was repeated, giving an average partition coefficient
2
8
t, J = 4.3 Hz, 4H, ArCH
Ar), 6.93 (t, JHH = 8.0 Hz, 1H, Ar); C{ H} 18.7 (m,
CH CH CF ), 27.7 (m, CH CH CF ), 38.7 (virtual t,
3.0 Hz, ArCH
), 124.2 (t, JCP = 11.0 Hz, Ar), 127.2 (s,
Ar), 148.9 (t, JCP = 10.3 Hz, Ar), 151.4 (s, Ar); P{ H}
CF CF CF
, −120.3 (CH ), −113.3 (CH
). MS (FAB, 3-NBA), m/z (%): 2059 (100) [M −
2
), 6.83 (d, J H1 H = 7.5 Hz, 2H,
of 98.0 : 2.0 (0.000189 g of 11-R in 0.500 mL toluene; 0.00966 g
f8
3
1
of 11-R in 0.0500 mL of CF C F ). A 3.00/0.500 scale factor
f8
3
6
11
28
2
2
2
2
2
2
J
CP
=
gave a mass recovery of 0.0591 g (95%).
1
2
3
1
1
Crystallography
1
9
4
(
1.4 (s); F −124.7 (CF
CF (CF CF
79.4 (CF
2
3
), −122.0 (CF
CF (CF
2
2
3
), −121.2
CF ),
A nearly saturated solution of 10-Rf8 in refluxing hexanes was
allowed to cool to room temperature. After 1 day, a transparent
colorless prism (0.25 × 0.20 × 0.20 mm) was taken to a Nonius
2
2
)
2
3
2
2
2
)
3
2
2
2
3
−
3
+
OCOCF
3
] .
KappaCCD area detector for data collection at 173(2) K (k
(
2,6,1-C
Method A. A Schlenk flask was charged with 3-Rf8 (0.1980 g,
.1012 mmol), THF (12 mL), and argon. Then [IrCl(COE)
6
H
3
(CH
2
P(CH
2
CH
2
R
f8
)
2
)
2
)Ir(Cl)(H) (11-Rf8).
0.71073 A˚ ). Cell parameters were obtained from 10 frames
◦
using a 10 scan and refined with 1242 reflections. Lorentz,
44
0
2
]
2
polarization and empirical (Scalepack) absorption corrections
33
(
0.0580 g, 0.0668 mmol) was added with stirring. After 0.5 h,
were applied. The space group was determined from systematic
absences and subsequent least-squares refinement. The structure
was solved by direct methods. The parameters were refined
◦
the mixture was warmed to 80 C. After 48 h, during which
time some brown precipitate formed, the mixture was cooled
and filtered. The solvent was removed from the filtrate by oil
pump vacuum. The brownish solid (0.0890 g) was dissolved in
2
with all data by full-matrix-least-squares on F using SHELXL-
45
97. Non-hydrogen atoms were refined with anisotropic thermal
parameters. The hydrogen atoms were fixed inidealizedpositions
using a riding model. The atom F46A showed some disorder, but
this could not be resolved. Scattering factors were taken from
CF
3
C
6
F
11 (3 mL). The solution was extracted with toluene (3 ×
1
.5 mL). The CF
3
6
C F
11 was removed by oil pump vacuum to
give 11-Rf8 (0.0630 g, 0.0289 mmol, 29%) as an orange-yellow
solid.
46
the literature.
D a l t o n T r a n s . , 2 0 0 5 , 2 2 7 5 – 2 2 8 3
2 2 8 1

View Article Online
Crystal data. Empirical formula: C50
mula weight: 2173.02; Crystal system: monoclinic; Space
H
23
F
71
O
2
P
2
Pd; For-
16 R. C. da Costa and J. A. Gladysz, manuscript in preparation.
17 (a) L. J. Alvey, D. Rutherford, J. J. J. Juliette and J. A. Gladysz, J. Org.
Chem., 1998, 63, 6302; (b) A. Klose and J. A. Gladysz, Tetrahedron:
Asymmetry, 1999, 10, 2665; (c) L. J. Alvey, R. Meier, T. So o´ s, P.
Bernatis and J. A. Gladysz, Eur. J. Inorg. Chem., 2000, 1975.
˚
3
group: P2
1
/n; Unit cell dimensions: a/b/c [A] 19.2920(9)/
◦
˚
9.3960(11)/20.5830(11), b [ ] 115.522(3), V [A ] 6950.3(6); Z
3
1
4
−
−1
; D
c
[Mg m ]: 2.077; Absorption coefficient [mm ]: 0.546;
1
8 (a) E. I. Musina, G. N. Nikonov, A. S. Balueva, E. F. Gubanov and
E. V. Kovalenko, Russ. J. Gen. Chem., 1999, 69, 407; (b) We substitute
1,3-C H (CH Br) for the dichloride and P(OEt) for the P(OBu)
◦
F(000): 4216; q limit [ ]: 2.19 to 25.10; Index ranges (h, k, l): −22,
2
2; −22, 22; −24, 24; Reflections collected: 23414; Independent
6
4
2
2
3
3
reflections: 12099 [R(int) = 0.0616]; Reflections [I > 2r(I)]:
used in the preceding reference, as reported by N. A. Caplan, C. I.
Pogson, D. J. Hayes and G. M. Blackburn, J. Chem. Soc., Perkin
Trans. I, 2000, 421; (c) Since the final reduction step in our synthesis
of 1 is technically new, full details are given in the Experimental
section.
9 It is essential to conduct the column chromatography (Experimental
section) under rigorous inert atmosphere conditions with degassed
solvents. The highest yields were obtained when this was done in a
glove box.
0 (a) D. G. Gusev, M. Madott, F. M. Dolgushin, K. A. Lyssenko and
M. Y. Antipin, Organometallics., 2000, 19, 1734; (b) E. Hollink, J. C.
Stewart, P. Wei and D. W. Stephan, Dalton Trans., 2003, 3968; (c) J. C.
Grimm, C. Nachtigal, H.-G. Mack, W. C. Kaska and H. A. Mayer,
Inorg. Chem. Commun., 2000, 3, 511; (d) H. A. Y. Mohammad,
J. C. Grimm, K. Eichele, H.-G. Mack, B. Speiser, F. Novak, M. G.
Quintanilla, W. C. Kaska and H. A. Mayer, Organometallics, 2002,
◦
6
854; Completeness to H = 25.10 (%): 97.7; Max. and min.
transmission: 0.8986 and 0.8755; Data/restraints/parameters:
2
1
[
2099/67/1135; Goodness-of-fit on F : 1.037; Final R indices
I > 2r(I)]: R1 = 0.1124, wR2 = 0.2973; R indices (all data):
1
2
−
3
˚
R1 = 0.1731, wR2 = 0.3413; Largest diff. peak and hole [e A ]:
1
.764/−1.096.
CCDC reference number 256984.
See http://www.rsc.org/suppdata/dt/b5/b502309b/ for cry-
stallographic data in CIF or other electronic format.
Acknowledgements
We thank the Bundesministerium f u¨ r Bildung und Forschung
BMBF), the Humboldt Foundation (fellowship to R. T.),
and Johnson Matthey PMC (palladium and iridium loans) for
support, and Dr Philip Osburn, Mr Rosenildo Corr eˆ a da Costa,
and Ms Charlotte Emnet for some helpful observations.
2
1, 5775; (e) D. Hermann, M. Gandelman, H. Rozenberg, L. J. W.
(
Shimon and D. Milstein, Organometallics, 2002, 21, 812.
21 (a) C. Emnet and J. A. Gladysz, Synthesis, 2005, 1012; (b) C.
Emnet, R. Tuba and J. A. Gladysz, Adv. Synth. Catal., submitted
for publication.
2
2 J. A. Gladysz, in Handbook of Fluorous Chemistry, ed. J. A. Gladysz,
D. P. Curran and I. T. Horv a´ th, Wiley/VCH, Weinheim, 2004,
ch. 5.
References and notes
2
3 (a) All m/z values represent the most intense peak of the isotope
1
(a) M. Albrecht and G. van Koten, Angew. Chem. Int. Ed., 2001,
envelope; (b) Both 10-Rf6 and 10-Rf8 gave ions with masses corre-
+
4
3
1
0, 3750; M. Albrecht and G. van Koten, Angew. Chem., 2001, 113,
866; (b) M. E. van der Boom and D. Milstein, Chem. Rev., 2003,
03, 1759.
sponding to [M + H
3
O] , but the intensities strongly depended upon
the sample.
24 (a) W. J. Bailey and S. A. Buckler, J. Am. Chem. Soc., 1957, 79,
3567; (b) S. T. D. Gough and S. Trippett, J. Chem. Soc., 1961, 4263;
(c) K. Sasse, Houben-Weyl Methoden der Organischen Chemie, Georg
Thieme Verlag, Stuttgart, Germany, 1963, vol. XII, part 1, pp. 52–53.
25 In one experiment, the crude reaction mixture was suspended in
2
(a) W. T. S. Huck, F. C. J. M. van Veggel, B. L. Kropman, D. H. A.
Blank, E. G. Keim, M. M. A. Smithers and D. N. Reinhoudt, J. Am.
Chem. Soc., 1995, 117, 8293; (b) W. T. S. Huck, F. C. J. M. van
Veggel and D. N. Reinhoudt, J. Mater. Chem., 1997, 7, 1213; (c)
B.-H. Huisman, H. Sch o¨ nherr, W. T. S. Huck, A. Friggeri, H.-J. van
Manen, E. Menozzi, G. J. Vancso, F. C. J. M. van Veggel and D. N.
Reinhoudt, Angew. Chem. Int. Ed., 1999, 38, 2248; B.-H. Huisman, H.
Sch o¨ nherr, W. T. S. Huck, A. Friggeri, H.-J. van Manen, E. Menozzi,
G. J. Vancso, F. C. J. M. van Veggel and D. N. Reinhoudt, Angew.
Chem., 1999, 111, 2385.
31
THF and treated with NaOAc. A P NMR spectrum showed small
quantities of the target pincer ligand 3-Rf8, presumably formed by
the deprotonation of 6-Rf8
.
26 (a) T. Imamoto, T. Kusumoto, N. Suzuki and K. Sato, J. Am. Chem.
Soc., 1985, 107, 5301; (b) D. Morales-Morales, R. E. Cramer and
C. M. Jensen, J. Organomet. Chem., 2002, 654, 44.
3
4
M. Q. Slagt, S.-E. Stiriba, H. Kautz, R. J. M. K. Gebbink, H. Frey
and G. van Koten, Organometallics, 2004, 23, 1525.
(a) M. D. Meijer, M. Rump, R. A. Gossage, J. H. T. B. Jastrzebski
and G. van Koten, Tetrahedron Lett., 1998, 39, 6773; (b) M. D.
Meijer, N. Ronde, D. Vogt, G. P. M. van Klink and G. van Koten,
Organometallics, 2001, 20, 3993.
27 H. Lebel, S. Morin and V. Paquet, Org. Lett., 2003, 5, 2347.
i
28 (a) W. H. Hersch, J. Chem. Educ., 1997, 74, 1485; (b) The JCP values
given represent the apparent coupling between adjacent peaks of the
i
i + 2
triplet. They are half of the true values | JCP
+
J
CP|.
29 (a) R. J. Cross, A. R. Kennedy and K. W. Muir, J. Organomet. Chem.,
1995, 487, 227 and earlier literature in Table 3 therein; (b) J. M.
Longmire, X. Zhang and M. Shang, Organometallics., 1998, 17, 4374;
(c) W. D. Cotter, L. Barbour, K. L. McNamara, R. Hechter and R. J.
Lachicotte, J. Am. Chem. Soc., 1998, 120, 11016; (d) R. B. Bedford,
S. M. Draper, P. N. Scully and S. L. Welch, New. J. Chem., 2000, 24,
745; (e) B. S. Williams, P. Dani, M. Lutz, A. L. Spek and G. van
Koten, Helv. Chim. Acta, 2001, 84, 3519; (f) R. Chanthateyanonth
and H. Alper, J. Mol. Catal. A, 2003, 201, 23; (g) M. R. Eberhard, S.
Matsukawa, Y. Yamamoto and C. M. Jensen, J. Organomet. Chem.,
2003, 687, 185; (h) A. Naghipour, S. J. Sabounchei, D. Morales-
Morales, S. Hern a´ ndez-Ortega and C. M. Jensen, J. Organomet.
Chem., 2004, 689, 2494.
5
6
7
(a) C. Pathmamanoharan, P. Wijkens, D. M. Grove and A. P. Philipse,
Langmuir, 1996, 12, 4372; (b) R. Chanthateyanonth and H. Alper,
Adv. Synth. Catal., 2004, 346, 1375.
(a) D. E. Bergbreiter, P. L. Osburn and Y.-S. Liu, J. Am. Chem. Soc.,
1
999, 121, 9531; (b) D. E. Bergbreiter, P. L. Osburn, A. Wilson and
E. M. Sink, J. Am. Chem. Soc., 2000, 122, 9058.
G. van Koten and J. T. B. H. Jastrzebski, J. Mol. Catal. A., 1999, 146,
3
17.
8
9
D. E. Bergbreiter and J. Li, Chem. Commun., 2004, 42.
E. Mas-Marz a´ , A. M. Segarra, C. Claver, E. Peris and E. Fernandez,
Tetrahedron Lett., 2003, 44, 6595.
0 (a) H. Kleijn, J. T. B. H. Jastrzebski, R. A. Gossage, H. Kooijman,
A. L. Spek and G. van Koten, Tetrahedron, 1998, 54, 1145; (b) P.
Dani, B. Richter, G. P. M. van Klink and G. van Koten, Eur. J. Inorg.
Chem., 2001, 125; (c) D. P. Curran, K. Fischer and G. Moura-Letts,
Synlett., 2004, 1379.
1 Handbook of Fluorous Chemistry, ed. J. A. Gladysz, D. P. Curran and
I. T. Horv a´ th, Wiley/VCH, Weinheim, 2004.
2 (a) K. Yu, W. Sommer, J. M. Richardson, M. Weck and C. W. Jones,
Adv. Synth. Catal., 2005, 347, 161; (b) D. E. Bergbreiter, P. L. Osburn
and J. Frels, Adv. Synth. Catal., 2005, 347, 172.
1
30 In n-perfluoroalkanes, global energy minima with anti F–C–C–F
◦
torsion angles of ca. 165 are commonly found. See (a) B. Albinsson
and J. Michl, J. Phys. Chem., 1996, 100, 3418; (b) E. K. Watkins
and W. L. Jorgensen, J. Phys. Chem. A., 2001, 105, 4118; (c) J. D.
Dunitz, A. Gavezzotti and W. B. Schwiezer, Helv. Chim. Acta., 2003,
86, 4073.
1
1
31 (a) M.-A. Guillevic, C. Rocaboy, A. M. Arif, I. T. Horv a´ th and
J. A. Gladysz, Organometallics, 1998, 17, 707; (b) J. Fawcett, E. G.
Hope, R. D. W. Kemmitt, D. R. Paige, D. R. Russell, A. M. Stuart,
D. J. Cole-Hamilton and M. J. Payne, Chem. Commun., 1997, 1127;
(c) C. M. Haar, J. Huang and S. P. Nolan, Organometallics, 1998, 17,
5018; (d) D. C. Smith, E. D. Stevens, Jr. and S. P. Nolan, Inorg. Chem.,
1999, 38, 5277; (e) R. T. Stibrany and S. M. Gorun, J. Organomet.
Chem., 1999, 579, 217.
1
3 (a) C. Rocaboy and J. A. Gladysz, New J. Chem., 2003, 27, 39; (b) C.
Rocaboy and J. A. Gladysz, Tetrahedron., 2002, 58, 4007; (c) C.
Rocaboy and J. A. Gladysz, Org. Lett., 2002, 4, 1993.
1
1
4 C. M. Jensen, Chem. Commun., 1999, 2443.
5 J. A. Gladysz, C. Emnet and J. R a´ bai, in Handbook of Fluorous
Chemistry, ed. J. A. Gladysz, D. P. Curran and I. T. Horv a´ th,
Wiley/VCH, Weinheim, 2004, ch. 6.
32 A. Bondi, J. Phys. Chem., 1964, 68, 441.
33 J. L. Herde, J. C. Lambert and C. V. Senoff, Inorg. Synth., 1974, 15,
18.
2
2 8 2
D a l t o n T r a n s . , 2 0 0 5 , 2 2 7 5 – 2 2 8 3

View Article Online
3
4 (a) I. G o¨ ttker-Schnetmann and M. Brookhart, J. Am. Chem. Soc.,
4015; (d) J. Otera, Acc. Chem. Res., 2004, 37, 288 and earlier work
cited therein; (e) G. Maayan, R. H. Fish and R. Neumann, Org. Lett.,
2003, 5, 3547.
2
004, 126, 9330; (b) D. Morales-Morales, R. R e´ don, C. Yung and
C. M. Jensen, Inorg. Chim. Acta, 2004, 357, 2953.
3
3
5 P. Osburn, Universit a¨ t Erlangen-N u¨ rnberg, unpublished results.
6 (a) J. Dupont, M. Pfeffer and J. Spencer, Eur. J. Inorg. Chem., 2001,
41 J. A. Gladysz, R. C. da Costa, in Handbook of Fluorous Chemistry,
ed. J. A. Gladysz, D. P. Curran and I. T. Horv a´ th, Wiley/VCH,
Weinheim, 2004, ch. 4.
1
917; (b) M. Ohff, A. Ohff, M. E. van der Boom and D. Milstein,
J. Am. Chem. Soc., 1997, 119, 11687; (c) K. Kiewel, Y. Liu, D. E.
Bergbreiter and G. A. Sulikowski, Tetrahedron Lett., 1999, 40, 8945;
42 L. V. Dinh and J. A. Gladysz, Angew. Chem. Int. Ed., 2005, 44,
DOI: 10.1002/anie.200500237.
(
d) M. R. Eberhard, Org. Lett., 2004, 6, 2125.
43 H. K. Cammenga and M. Epple, Angew. Chem., Int. Ed. Engl., 1995,
34, 1171; H. K. Cammenga and M. Epple, Angew. Chem., 1995, 107,
1284.
44 (a) Collect data collection software, Nonius B.V., Delft, The
Netherlands, 1998; (b) “Scalepack” data processing software: Z.
Otwinowski and W. Minor, Methods in Enzymology, Academic Press,
New York, 1997, vol. 276 (Macromolecular Crystallography, Part A),
p. 307.
45 G. M. Sheldrick, SHELX-97, Program for refinement of crystal
structures, University of G o¨ ttingen, Germany, 1997.
46 D. T. Cromer and J. T. Waber, in International Tables for X-ray
Crystallography, ed. J. A. Ibers and W. C. Hamilton, Kynoch Press,
Birmingham, UK, 1974.
3
7 (a) N. Solin, J. Kjellgren and K. J. Szab o´ , Angew. Chem. Int. Ed.,
2
2
003, 42, 3656; N. Solin, J. Kjellgren and K. J. Szab o´ , Angew. Chem.,
003, 115, 3784; (b) N. Solin, J. Kjellgren and K. J. Szab o´ , J. Am.
Chem. Soc., 2004, 126, 7026.
3
3
4
8 K. B. Renkema, Y. V. Kissin and A. S. Goldman, J. Am. Chem. Soc.,
2
003, 125, 7770.
9 M. Wende and J. A. Gladysz, J. Am. Chem. Soc., 2003, 125,
861.
0 (a) K. Ishihara, S. Kondo and H. Yamamoto, Synlett., 2001, 1371;
b) K. Ishihara, A. Hasegawa and H. Yamamoto, Synlett., 2002,
299; (c) K. Mikami, Y. Mikami, H. Matsuzawa, Y. Matsumoto, J.
Nishikido, F. Yamamoto and H. Nakajima, Tetrahedron., 2002, 58,
5
(
1
D a l t o n T r a n s . , 2 0 0 5 , 2 2 7 5 – 2 2 8 3
2 2 8 3