Pd(O2CCF2CF3-O)2(dppf) nd PdAg(μ-O2CCF2CF3)2(O2CCF2CF3-O)-(dppf) [dppf = 1,1'-bis(diphenylphosphino)ferrocene]: A stable Pd(II) phosphine carboxylate as a precursor to heterobimetallic carboxylates

Article abstract of DOI:10.1039/b104539n

Single crystal X-ray diffraction analysis of Pd(O2CCF2CF3-O)2(dppf) 1 shows that one of the two unidentate fluoropropanoates shows a rare bonding behavior with significant ? character for the C=O_coord bond whereas the C-O_pendant bond

Full text of DOI:10.1039/b104539n

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Pd(O2CCF2CF3-O)2(dppf )andPdAg(ꢀ-O2CCF2CF3)2(O2CCF2CF3-O)-
(dppf ) [dppf ؍ 1,1Ј-bis(diphenylphosphino)ferrocene]:
A stable Pd(II) phosphine carboxylate as a precursor to
heterobimetallic carboxylates
Yew Chin Neo, Jagadese J. Vittal and T. S. Andy Hor*
Department of Chemistry, National University of Singapore, 3 Science Drive 3,
Singapore 117543. E-mail: andyhor@nus.edu.sg
Received 22nd May 2001, Accepted 26th October 2001
First published as an Advance Article on the web 20th December 2001
Single crystal X-ray diffraction analysis of Pd(O2CCF2CF3-O)2(dppf ) 1 shows that one of the two unidentate
fluoropropanoates shows a rare bonding behavior with significant π character for the C᎐Ocoord bond whereas the
᎐
C–Opendant bond is long and bears a basic function. Complex 1 serves as a metalloligand towards AgO2CCF2CF3
to give PdAg(µ-O2CCF2CF3)2(O2CCF2CF3-O)(dppf ) 2, which is fluxional in solution showing interchanges of the
bridging and unidentate fluoropropanoate groups. Being an unusually stable Pd() carboxylate, 1 also serves an
effective entry to mixed-metal carboxylates.
The spectroscopic data suggest that the fluoropropanoate is
Introduction
in a unidentate mode in 1. Crystallographic analysis reveals that
it is mononuclear with chelating dppf and two unidentately
coordinated fluoropropanoates. With AgO2CCF2CF3, both
pendant oxygens bind to the incoming metal thus forming two
fluoropropanoate bridges in 2. The third fluoropropanoate on
the Ag() remains unidentate. This X-ray structure is not con-
sistent with the 19F NMR spectrum which gives only one set of
19F peaks.
Although carboxylate complexes have a long-standing history
in coordination chemistry,1 the coordination behaviour of
carboxylates towards Pd() phosphine is poorly understood
owing to the spontaneous decomposition of the system.2 Even
on rare occasions when such species were isolated,3–7 their
chemical reactivity and dynamic behaviour were virtually
unknown. The Pt() analogues on the other hand are stable
and established.8,9 In this paper, we report a rare isolation and
structural characterization of a representative in this system,
Pd(O2CCF2CF3)2(dppf ) 1, and demonstrate that this cis-
arrangement of two unidentate carboxylate groups7,9,10 is a
powerful entity to enter into the field of heterobimetallic
carboxylates.11 This is exemplified by the isolation of a Ag()/
Pd() bimetallic system, which is an extension of our recent
interest in Ag() carboxylates.12 While there are examples of
bimetallic carboxylate systems,11,13,14 we are not aware of any
reports on the preparation of a similar system using cis-
oriented unidentate carboxylates as precursors.
We have performed the 19F and 31P variable-temperature
NMR experiments of 2 in CDCl3. The former clearly shows
the dynamics of the system in solution (Fig. 1). As shown, the
two singlets, corresponding to CF2 and CF3, broaden as the
temperature decreases. The CF3 peak eventually splits into
two with ratio 2 : 1 at 233 K. Some degree of selective line
broadening is observed at the lower limit of the experiments
(213 and 223 K), the CF2 (at δ ≈40) shows non-symmetrical
broadening. Deconvolution of the CF2 peak at 223 K (Fig. 2a)
and 213 K (Fig. 2b) shows that it comprises three peaks with
similar intensities. Surprisingly, the CF3 peaks do not show any
significant broadening. The 31P NMR spectrum shows a single
resonance at room temperature. It broadens and splits to two
symmetric peaks at lower temperature (Fig. 3).
Results and discussion
These spectral changes can be related to two independant
fluxional mechanisms as depicted in Schemes 1 and 2. The
unidentate and bridging fluoropropanoates interchange rapidly
Metathesis of PdCl2(dppf ) with two mole equivalents of
AgO2CCF2CF3 yields 1 in near-quantitative yield (95%). Excess
AgO2CCF2CF3 results in PdAg(µ-O2CCF2CF3)2(O2CCF2CF3-
O)(dppf ) 2 as a byproduct. Complex 2 can be obtained from
stoichiometric equivalents of 1 and AgO2CCF2CF3 in good
yield (ca. 88%), which lends support that 1 is the precursor of 2.
The IR symmetrical and antisymmetrical ν(CO2Ϫ) stretches of
1 at 1325 and 1688 cmϪ1 respectively, with a difference (∆ν) of
363 cmϪ1, are consistent with a unidentate coordination mode
for the carboxylate.15 The IR spectrum of 2 is more complex—it
displays features of both unidentate [νantisym(CO2Ϫ) 1715 sh and
1690 vs cmϪ1 and νsym(CO2Ϫ) 1326 m cmϪ1] and bridging
[ν(CO2Ϫ) 1586, 1574, 1436 and 1401 cmϪ1] carboxylates. The
NMR spectra give a significantly more deshielded phosphorus
(δP 40.4) in 2 as compared to 1 (δP 36.5). This deshielding effect
is also felt by the Cp and Ph ring protons of dppf (1H NMR)
and the fluorine nuclei (δF Ϫ7.73 and Ϫ43.90 for 1 and Ϫ7.54
and Ϫ43.01 for 2).
Scheme 1 An interchange mechanism for unidentate and bridging
fluoropropanoate of (dppf )Pd(µ-O2CCF2CF3)2Ag(O2CCF2CF3-O) 2 in
solution via exchange of the pendant oxygen and the oxygen atoms on
palladium.
DOI: 10.1039/b104539n
J. Chem. Soc., Dalton Trans., 2002, 337–342
This journal is © The Royal Society of Chemistry 2002
337

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Fig. 3 VT 31P NMR spectra of PdAg(µ-O2CCF2CF3)2(O2CCF2CF3-
O)(dppf ) 2 in CDCl3.
Fig. 1 VT 19F NMR spectra of PdAg(µ-O2CCF2CF3)2(O2CCF2CF3-
O)(dppf ) 2 in CDCl3.
Scheme 2 Rapid exchange of two- and three-coordinated Ag() of
(dppf )Pd(µ-O2CCF2CF3)2Ag(O2CCF2CF3-O) 2 in solution.
breaking/making that equilibrates all the fluoropropanoates.
Below 243 K, this fluxionality slows down considerably,
which results in splitting and separation of the 19F peaks. The
phosphorus atoms are indistinguishable at ≈253–300 K, which
corresponds to the solid state structure. The symmetric splitting
of the 31P peak at low temperatures could be rationalised by
a facile exchange between two- and three-coordinate Ag()
through making and breaking of Ag–O bonds (Scheme 2). This
process does not require the exchange of bridging and terminal
fluoropropanoates. The CF3 signals of the bridging fluoropro-
panoates are less affected because they are further away from
the migration sites. This exchange (Scheme 2) is understandably
more rapid than that depicted in Scheme 1. These exchanges are
expected to be retarded by the presence of another Lewis acid.
When a molar equivalent of AgO2CCF2CF3 is added to 2, the
product, tentatively assigned as PdAg2(µ-O2CCF2CF3)2-
(O2CCF2CF3-O)2(dppf ) 3 (δP 41.95, δF Ϫ7.54 and Ϫ43.01),
does not show 31P peak splitting at 213 K, although the CF3
singlet splits neatly to two equal-intensity peaks (Fig. 4). The
CF2 signal broadens only at the lowest limit of the experiments.
In view of the rarity of stable Pd() phosphine carboxylates,
their potential use as heterobimetallic precursors, and the
solution dynamics, we have carried out single-crystal X-ray
Fig. 2 Deconvoluted 19F peaks of CF2 of PdAg(µ-O2CCF2CF3)2-
(O2CCF2CF3-O)(dppf ) 2 in CDCl3 at (a) 223 K and (b) 213 K.
through attack of the pendant oxygen on Pd, thereby releasing
one of its attached carboxylate oxygens (Scheme 1). The
displaced oxygen returns to Pd and the cycle repeats on each
of the fluoropropanoates. Effectively, the Ag core rapidly
tumbles around the Pd centre with a sequential Pd–O bond
338
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Fig. 4 VT 19F NMR spectra of PdAg2(µ-O2CCF2CF3)2(O2CCF2CF3-
O)2(dppf ) 3 in CDCl3.
crystallographic analysis of complexes 1 and 2 (Tables 1 and 2;
Figs. 5 and 6). The results are consistent with the solution struc-
tures proposed above. It is notable that 1 prefers a mononuclear
structure with chelating dppf and two cis-fluoropropanoates
despite the fact that (a) bridging (and even ionic) carboxylates
are much more common than unidentate carboxylates;1 (b)
the thermodynamic stability of the cis-arrangement of two
unidentate carboxylates is much lower compared to other
alternative arrangements; (c) carboxylate chains longer than C1
usually prefer a chelating or bridging to a unidentate mode; (d)
Fig.
5
ORTEP25 drawing (50% probability ellipsoids) of the
molecular structure of Pd(O2CCF2CF3)2(dppf ) 1.
Table 1 Crystallographic data and refinement details for 1 and 2ؒ2H2O
1
2ؒ2H2O
Chemical formula
Mr
C40H28F10FeO4P2Pd
986.81
C43H32AgF15FeO8P2Pd
1293.76
Temperature/K
Crystal system
Space group
223(2)
Monoclinic
P21/c
223(2)
Triclinic
¯
P1
a/Å
b/Å
12.776(1)
20.945(2)
11.809(1)
13.747(1)
c/Å
α/Њ
15.511(1)
90
14.955(1)
83.046(1)
β/Њ
110.990(2)
90
3875.2(5)
4
1.691
1.001
74.119(1)
82.730(1)
2306.77(4)
2
1.860
γ/Њ
V/Å3
Z
ρcalcd/g cmϪ3
µ/mmϪ1
1.298
Reflections collected
Independent reflections
GOF on F 2
Final R indices [I > 2σ(I )]
R indices (all data)
(∆ρ)max, (∆ρ)min/e ÅϪ3
32140
11255 [R(int) = 0.1131]
0.824
R1 = 0.0565, wR2 = 0.0817
R1 = 0.1192, wR2 = 0.0930
0.902, Ϫ1.294
13307
9075 [R(int) = 0.0238]
1.095
R1 = 0.0628, wR2 = 0.1650
R1 = 0.0680, wR2 = 0.1706
1.756, Ϫ1.699
4
R1 = Σ Fo| Ϫ |Fc /Σ|Fo|. wR2 = {Σw|[(Fo2 Ϫ Fc2)2]/ΣwFo }1/2
.
J. Chem. Soc., Dalton Trans., 2002, 337–342
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Table 2 Selected bond distances (Å) and angles (Њ) of 1 and 2ؒ2H2O. τ
is the torsional angle of ferrocene while χAand χB are the centroids of
the Cp rings of dppf
1
2ؒ2H2O
Pd(1)–P(1)
Pd(1)–P(2)
Pd(1)–O(1)
Pd(1)–O(3)
Pd(1)–Ag(1)
C(11)–O(1)
C(11)–O(2)
C(14)–O(3)
C(14)–O(4)
Ag(1)–O(2)
Ag(1)–O(4)
Ag(1)–O(5)
C(17)–O(5)
C(17)–O(6)
2.2525(11)
2.2685(11)
2.076(3)
2.2609(15)
2.2808(16)
2.114(4)
2.095(5)
3.0987(8)
1.246(9)
1.224(9)
1.248(10)
1.219(11)
2.249(6)
2.403(7)
2.164(6)
1.240(10)
1.214(10)
2.065(3)
—
1.272(5)
1.197(5)
1.201(6)
1.245(6)
—
—
—
—
—
P(1)–Pd(1)–P(2)
O(1)–Pd(1)–O(3)
P(1)–Pd(1)–O(1)
P(1)–Pd(1)–O(3)
P(2)–Pd(1)–O(1)
P(2)–Pd(1)–O(3)
Pd(1)–O(1)–C(11)
Pd(1)–O(3)–C(14)
O(1)–C(11)–O(2)
O(3)–C(14)–O(4)
O(2)–Ag(1)–O(5)
O(4)–Ag(1)–O(5)
O(2)–Ag(1)–O(4)
Ag(1)–O(5)–C(17)
O(5)–C(17)–O(6)
P(1)–Pd(1)–Ag(1)
P(2)–Pd(1)–Ag(1)
O(1)–Pd(1)–Ag(1)
O(3)–Pd(1)–Ag(1)
O(2)–Ag(1)–Pd(1)
O(4)–Ag(1)–Pd(1)
O(5)–Ag(1)–Pd(1)
96.38(4)
85.53(11)
90.03(8)
174.29(10)
173.59(8)
88.08(9)
113.6(3)
118.8(4)
129.4(4)
131.2(5)
97.64(6)
86.5(2)
Fig. 7 Some possible coordination and geometric isomers of Pd(O2-
CCF2CF3)2(dppf ) 1.
175.49(15)
89.46(15)
85.83(14)
164.43(16)
122.7(4)
127.9(5)
130.5(7)
130.8(7)
153.7(2)
117.0(2)
87.5(3)
116.5(5)
128.2(8)
98.23(4)
109.86(5)
83.22(14)
82.61(15)
74.19(15)
75.54(15)
119.26(16)
square planar platinum group metal complexes, but most of
them are spectroscopically identified,10,17 except a few notable
exceptions that have crystallographic support.3,6,7,9,18 Based on
IR data the AsPh3 analogue of 1 has unidentate carboxylates.17
At first glance, the structure of 1 is similar to that of
Pd(O2CCF3)2(L) [L = dppm 4,7 6,6Ј-dimethoxybiphenyl-2,2Ј-
diyl)bis(diphenylphosphine) 56]. Closer examinations revealed
two notable differences: (a) the two pendant O atoms are in a
syn conformation in 4 and 5 whereas in 1 they are anti to each
other; (b) in a unidentate mode the C–Ocoord is expected to be
typically C–O single bonds (1.237–1.29519c Å)7,9,18a,19 whereas
—
—
—
—
—
—
—
—
—
—
—
—
the C–Opendant usually has a predominantly C᎐O π character
᎐
(1.197,19a–1.2318a Å).7,9,18a,19 This is observed in 4 and 5 but in 1,
only one of the two fluoropropanoates shows such character.
The odd fluoropropanoate has a C–Opendant [1.245(6) Å] bond
that is significantly longer than the C–Ocoord [1.201(6) Å]
(Fig. 8). We are not aware of reports of such an anomaly in
τ
Ϫ33.5
179.71
31.3
178.98
χA–Fe–χB
Fig.
8
Structure of Pd(O2CCF2CF3)2(dppf ) 1 showing different
Ϫ
bonding modes of the CF3CF2CO2 groups: (a) shows the common
unidentate carboxylate bonding mode while (b) shows the odd
unidentate carboxylate bonding mode.
the literature, except perhaps in Hg(O2CMe)(Ph)20 † which
shows much smaller C–O bond distance differences (1.29 and
1.31 Å).20 While the exact reason of such an anomaly is not
clear, the intention seems reasonable—the complex uses this
mechanism to transfer some charge away from the M–O to the
C–O sites. This gives a more anionic and nucleophilic character
to the C–O moiety i.e. –C–OδϪ, and renders the Ocoord more like
Fig.
6
ORTEP25 drawing (50% probability ellipsoids) of the
a neutral (and weaker) σ donor i.e. –C᎐O
M. The higher
᎐
molecular structure of PdAg(µ-O2CCF2CF3)2(O2CCF2CF3-O)(dppf )ؒ
2H2O 2ؒ2H2O. The hydrogen atoms, minor disordered F atoms and
water solvates are omitted for clarity.
charge on the pendant oxygen also forces the neighboring
fluoropropanoate groups to minimize repulsion by adopting an
anti conformation. This arrangement is in line with the steric
effect imposed by dppf. The dissipation of charge away from
the metal appears to support an internal redox mechanism
chelating dppf can easily convert to bridging dppf (in support
of the changes in the mode of coordination of carboxylate)
which is equally common.16 The near quantitative yield of 1
suggests that the synthesis is isomerically self-selective—there is
no evidence of other coordination isomers (Fig. 7). Similar cis-
arranged unidentate carboxylates are also observed in other
† As the Hg–Opendant distance (2.85 Å)20 appears too short to be
ignored, it may be considered as a semi-chelate instead of a typical
unidentate mode as in 1 (Pd ؒ ؒ ؒ Opendant 3.156 Å).
340
J. Chem. Soc., Dalton Trans., 2002, 337–342

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recognized in Pd() phosphine carboxylates. These are active
catalytic precursors because of their ability to give Pd() species
spontaneously without the need to introduce an external
reducing agent. The transformation of an acyloxy to a carbonyl
group appears to provide an avenue for the Pd in its formal
oxidation state (ϩ2) to stabilize itself without going through a
self-destructive reduction process. With such a coordination
mode, the two phosphorus nuclei are strictly inequivalent in a
static state. This is not consistant with the singlet observed in
the rt spectrum. At lower temperatures, the 31P NMR spectrum
(Fig. 9) shows an emerging pair of doublets (δP 40.4 and 35.1;
Scheme 3 Rapid tumbling of a unidentate fluorocarboxylate through
exchange of a pendant and coordinated oxygen of Pd(O2CCF2CF3)2-
(dppf ) 1 in CDCl3.
significantly by >10Њ, whereas for 1 they are essentially equal
[174.29(10) and 173.59(8)Њ]. The Ag() geometry is planar but
tends towards a T than a trigonal shape. The Pd–Ag distance
[3.0987(8) Å], which is shorter than the van der Waals contact
of Pd–Ag (3.30 Å), is brought about by the two bridging fluoro-
propanoates rather than formal M–M interactions.
Isolation of 1 clearly suggests that under favourable con-
ditions, some Pd() phosphine carboxylates are stable enough
to be isolated and studied. This has positive implications in the
design of Heck-type catalysts. The use of fluoro derivatives
helps the cause by stabilizing the unidentate mode, without
nullifying its basicity. This delicate balance helps 1 capture
other Lewis acidic fragments such that formation of species like
2 is realized. Such a balance of stability, catalytic activity
and chemical reactivity poses a prime challenge to the design
of many catalytic systems. Our immediate task is to look for
other bimetallic complexes that could expand the horizon of
Heck-type syntheses, which are almost exclusively Pd() based.
We are also interested to explore the catalytic activities of 2
which is sufficiently basic to react with excess AgO2CCF2CF3.
This opens an extra window for us to enter the field of mixed-
metal mixed-carboxylates.
Fig. 9 VT 31P NMR spectra of Pd(O2CCF2CF3)2(dppf ) 1 in CDCl3.
2JPP = 15.25 Hz) with a small coupling constant consistent with
cis-coupling. At the limit of the experiments, these doublets are
still weak compared to the singlet. Similar observations are
recorded in the CF2CF3 peaks in 19F NMR spectra at lower
temperatures. These point to a slow emergence of a static struc-
ture with phosphine and carboxylates inequivalent (B in
Scheme 3). A reasonable fluxionality would involve the carb-
oxylate fluctuating between syn and trans-conformations (of
the pendant oxygen) in solution. This can proceed via free rota-
tion of Pd–O bonds and nucleophilic attack of pendant oxygen
on the Pd centre (Scheme 3). The single-crystal X-ray structure
of 1 is also consistent with an “intermediate” mode (B) of the
process (Scheme 3).
The nucleophilic character of the pendant O enables 1 to
“mop up” AgO2CCF2CF3 readily. The resultant 2 shows a bi-
metallic structure with two syn-syn bridging and one unidentate
fluoropropanoate group. The coordination to AgO2CCF2CF3
weakens slightly both Pd–P [av. 2.2709(16) Å] and Pd–O [av.
2.105(5) Å] bonds in 2 as compared with 1 [Pd–P: av. 2.2605(11)
Å. Pd–O: av. 2.071(3) Å]. The weaker Pd–O bonds could pro-
vide a pathway for facile carboxylate interchange to occur,
which requires the cleavage of the Pd–O bond as a key step. The
two Ag–O(bridging) bonds are significantly different [2.249(6)
and 2.403(7) Å]. With the mobility of both fluoropropanoate
restricted, some angular distortions are apparent. For example,
the two trans-P–Pd–O angles [175.49(15) and 164.43(16)Њ] differ
Experimental
General procedures
All reactions were performed under pure dry argon using
standard Schlenk techniques. The products are stable and hence
recrystallizations were performed in air. All solvents and
reagents were of reagent grade obtained from commercial
sources and used without further purification. PdCl2(dppf ) was
prepared following the literature method.21
All 1H, 31P and 19F NMR spectra were recorded at ca. 300 K
at operating frequencies of 299.96, 121.49 and 282.23 MHz
1
respectively. H, 31P and 19F chemical shifts are quoted in ppm
downfield of Me4Si, and external CF3CO2H and 85% H3PO4
respectively. All IR spectra were recorded in the solid state on a
Bio-Rad FT-IR spectrometer using a KBr disk. Elemental
analyses were performed by the Elemental Analysis Laboratory
of our Department.
Syntheses
Synthesis of Pd(O2CCF2CF3-O)2(dppf ) 1. PdCl2(dppf )
(0.400 g, 0.547 mmol) and AgO2CCF2CF3 (0.2977 g, 1.099
J. Chem. Soc., Dalton Trans., 2002, 337–342
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mmol) in CH2Cl2 (80 cm3) were stirred at rt, shielded from
direct light for ca. 20 h. The dark red suspension was filtered
through a column of Celite, giving a deep red filtrate which was
concentrated to ca. 10 cm3. Hexane was added to crystallize
the compound, complex 1 (Yield, 0.5143 g, 95%). (Found: C,
48.68; H, 2.52%. C40H28F10O4P2Pd requires C, 48.40; H, 2.86%).
νmax/cmϪ1 (RCO2Ϫ) 1688 vs and 1325 s (KBr); δH (CDCl3) 4.44
Acknowledgements
We acknowledge the National University of Singapore for
financial support (RP 143–000–013–112) and technical
assistance from our Department. We thank G. K. Tan for
assistance with the X-ray analysis. Y. C. Neo is grateful to NUS
for a research scholarship.
3
[4 H, d, J(PH) 1.6 Hz, C5H4]; 4.50 (4 H, s, C5H4); 7.36–7.42
(8 H, m, Ph); 7.50–7.56 (4 H, m, Ph) and 7.77–7.85 (8 H, m,
Ph); δP (CDCl3) 36.48 (s); δF (CDCl3) Ϫ7.73 (6 F, s, CF3) and
Ϫ43.90 (4 F, s, CF2).
References
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Synthesis of PdAg(ꢀ-O2CCF2CF3)2(O2CCF2CF3-O)(dppf ) 2.
AgO2CCF2CF3 (0.0166 g, 0.0613 mmol) was added to a solu-
tion of Pd(O2CCF2CF3)2(dppf ) 1 (0.0600 g, 0.0608 mmol) in
CH2Cl2 (10 cm3). The mixture was stirred for 30 min, shielded
from direct light. The mixture was then filtered to remove the
insoluble Ag particles. Purplish black coloured crystals of 2ؒ
2H2O were collected (0.0692 g, 88%) after slow diffusion of the
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light. (Found: C, 39.44; H, 2.09%. C43H32AgF15FeO8P2Pd
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Ph); δP (CDCl3) 40.44 (s); δF (CDCl3) Ϫ7.54 (9 F, s, CF3) and
Ϫ43.01 (6 F, s, CF2).
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Synthesis of PdAg2(ꢀ-O2CCF2CF3)2(O2CCF2CF3-O)2(dppf ) 3.
PdAg(O2CCF2CF3)3(dppf )ؒ2H2O (0.050 g, 0.0386 mmol)
and AgO2CEtF (0.0108 g, 0.0386 mmol) were allowed to
stir in CH2Cl2 (20 cm3) for 30 min, shielded from direct light.
The reaction mixture was then dried in vacuo. The product 3
was recrystallized in CH2Cl2–hexane. Yield, 0.053 g (87%).
(Found: C, 36.19; H, 1.90%. C46H28Ag2F20FeO8P2Pd requires C,
36.14; H, 1.85%). νmax/cmϪ1 (RCO2Ϫ) 1681 vs, 1635 sh, 1575
w, 1558 w, 1481 m, 1436 s, 1409 s, 1327 vs (KBr); δH (CDCl3)
4.56 (4 H, s, C5H4); 4.64 (4 H, s, C5H4); 7.44–7.52 (8 H, m, Ph);
7.56–7.61 (4 H, m, Ph) and 7.82–7.90 (8 H, m, Ph); δP (CDCl3)
41.95 (s); δF (CDCl3) Ϫ7.54 (12 F, s, CF3) and Ϫ43.01 (8 F,
s, CF2).
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22 SMART and SAINT Software Reference Manuals, Version 5.611,
Bruker Analytical X-Ray Systems, Inc., Madison, WI, 2000.
23 G. M. Sheldrick, SADABS, software for empirical absorption
correction, University of Göttingen, 2000.
Crystal structure determinations
The diffraction experiments were carried out on a Bruker
SMART CCD diffractometer with a Mo-Kα sealed tube at
Ϫ50 ЊC. The program SMART22 was used for collecting frames
of data, indexing reflections and determination of lattice
parameters, SAINT22 for integration of the intensity of reflec-
tions and scaling, SADABS23 for absorption correction and
SHELXTL24 for space group and structure determination and
least-squares refinements on F 2. The relevant crystallographic
data and refinement details are shown in Table 1. Compound 2
crystallized with two molecules of H2O and the F atoms are
severely disordered. The three F atoms attached to C(13) were
found to be disordered. Two disorder models (occupancies
0.6 and 0.4) were resolved and included in the least-squares
refinement cycles. Individual isotropic thermal parameters were
refined for the F atoms with occupancies 0.6 and a common
isotropic thermal parameter was refined for the minor com-
ponent. Two independent orientations were found for one CF2–
CF3 group [attached to C(14)] with occupancies 50 : 50. Com-
mon isotropic thermal parameters were refined for these dis-
ordered atoms. The F atoms attached to C(19) were disordered.
Two orientations of F atoms were included in the model. Of the
two water molecules found in the lattice, one was disordered
with an occupancy of 50 : 50.
24 SHELXTL Reference Manual, Version 5.1, Bruker Analytical
X-Ray Systems, Inc., Madison, WI, 1997.
25 C. K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge National
Laboratory, Oak Ridge, TN, 1976.
CCDC reference numbers 165079 and 165080.
See http://www.rsc.org/suppdata/dt/b1/b104539n/ for crystal-
lographic data in CIF or other electronic format.
342
J. Chem. Soc., Dalton Trans., 2002, 337–342