(2,4,6-tris(trifluoromethyl)phenyl)palladium(II) complexes

Article abstract of DOI:10.1021/om950851t

Complexes containing one or two Fmes ligands (Fmes = 2,4,6-tris(trifluoromethyl)phenyl = nonafluoromesityl) either trans or cis are obtained by treating palladium(II) chloro complexes with Li(Fmes): trans-[PdCl₂L₂] (L = tetrahydrothi

Full text of DOI:10.1021/om950851t

Organometallics 1996, 15, 2019-2028
2019
(2,4,6-Tr is(tr iflu or om eth yl)p h en yl)p a lla d iu m (II)
Com p lexes
Camino Bartolome´, Pablo Espinet,*,† and Fernando Villafan˜e
Departamento de Quı´mica Inorga´nica, Facultad de Ciencias, Universidad de Valladolid,
47005 Valladolid, Spain
Sabine Giesa, Antonio Mart´ın, and A. Guy Orpen‡
School of Chemistry, University of Bristol, Bristol BS8 1TS, U.K.
Received October 27, 1995X
Complexes containing one or two Fmes ligands (Fmes ) 2,4,6-tris(trifluoromethyl)phenyl
) nonafluoromesityl) either trans or cis are obtained by treating palladium(II) chloro
complexes with Li(Fmes): trans-[PdCl2L2] (L ) tetrahydrothiophene (tht), PPh3) lead to trans-
[Pd(Fmes)ClL2] (L ) tht, PPh3) or trans-[Pd(Fmes)2L2] (L ) tht); [PdCl2(L-L)] (L-L ) 1,5-
cyclooctadiene, 2,2′-bipyridine) give [Pd(Fmes)Cl(L-L)] (L-L ) COD, bipy) or [Pd(Fmes)2-
(bipy)]. The structures of two complexes containing two Fmes ligands in trans and cis
arrangement, trans-[Pd(Fmes)2(tht)2] (2) and [Pd(Fmes)2(bipy)] (6), respectively, have been
determined by X-ray diffraction. In spite of the severe steric congestion the complexes are
four coordinated. Distortions due to the bulkiness of the ortho substituents and short
Pd‚‚‚F3C-ortho distances are observed. The high degree of steric crowding is also responsible
for slow rotation around the Pd-P bonds in the complex trans-[Pd(Fmes)Cl(PPh3)2]. ∆Gq
associated with this motion is 12.8 kcal mol-1, one of the highest values reported so far for
rotation around M-PPh3 bonds. Complexes 2 and 6 are redox inactive by cyclic voltammetry
in the range -1.8 to +1.8 V.
In tr od u ction
and induces unusual structural features such as the
stabilization of low-coordinated complexes. Its coordi-
nation to Cu and group 12 metals has also been
reported.7 The stability of these complexes is attributed,
in addition to the above mentioned factors common to
fluoroaryls, to the steric bulk of the ligand and to the
possibility of short metal-fluorine interactions involving
the ortho-CF3 groups. These properties should make
the 2,4,6-tris(trifluoromethyl)phenyl group an interest-
ing ligand also for transition metals, but so far there
are only two reports on its coordination to middle
transition metals: It is mentioned in a review that
Herrmann’s group has synthesized Re(Fmes)O3,2 and
a recent communication has appeared reporting the
syntheses of Co(Fmes)2 and Ni(Fmes)2,8 although no
X-ray structures have been reported.
Fluoroaryl complexes of palladium or platinum, par-
ticularly C6F5 derivatives, have contributed greatly to
the expansion of the chemistry of these metals. They
have made possible the isolation and characterization
of many new structural types of complexes in the solid
state, facilitated studies in solution, and helped in the
elucidation of reaction mechanisms.1 These studies
have been favored by the higher stability of fluoroaryl
complexes compared to the analogous aryl derivatives,
which has been explained by several factors, such as
the greater electronegativity of the fluoroaryl ligand,
which introduces a certain ionic character in the M-C
bond, and some degree of M-fluoroaryl back-donation.
A natural expansion of this chemistry is the use of other
fluoroaryl ligands with different steric requirements,
electronegativities, or symmetries.
Several points of interest can arise in complexes of
the bulky Fmes ligand: (a) If the C6F5 derivatives (the
fluoroaryl ligand most extensively used in palladium
chemistry)1a show a certain degree of crowding, as
revealed by many cases of restricted rotation around the
M-C6F5 bonds,9 the effects of crowding should be much
The 2,4,6-tris(trifluoromethyl)phenyl (nonafluoromes-
ityl or Fmes) group has been used recently as a ligand
for main group metals,2 such as Sn,3 Pb,4 Ga,5 or In,6
† E-mail: espinet@cpd.uva.es.
‡ E-mail: guy.orpen@bris.ac.uk.
X Abstract published in Advance ACS Abstracts, March 15, 1996.
(1) (a) Uso´n, R.; Fornie´s, J . Adv. Organomet. Chem. 1988, 28, 219.
(b) Maitlis, P. M.; Espinet, P.; Russell, M. J . H. In Comprehensive
Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W.,
Eds.; Pergamon: Oxford, U.K., 1982; Chapter 38.4. (c) Hartley, F. R.
Ibid., Chapter 39.
(6) Schluter, R. D.; Cowley, A. H.; Atwood, D. A.; J ones, R. A.; Bond,
M. R.; Carrano, C. J . J . Am. Chem. Soc. 1993, 115, 2070.
(7) (a) Carr, G. E.; Chambers, R. D.; Holmes, T. F.; Parker, D. G. J .
Organomet. Chem. 1987, 325, 13. (b) Brooker, S.; Bertel, N.; Stalke,
D.; Noltenmeyer, M.; Roesky, H. W.; Sheldrick, G. M.; Edelmann, F.
T. Organometallics 1992, 11, 192.
(8) Belay, M.; Edelmann, F. T. J . Organomet. Chem. 1994, 479, C21.
(9) (a) Casares, J . A.; Coco, S.; Espinet, P.; Lin, Y.-S. Organometallics
1995, 14, 3058. (b) Albe´niz, A. C.; Cuevas, J . C.; Espinet, P.; de
Mendoza, J .; Prados, P. J . Organomet. Chem. 1991, 410, 257. (c)
Deacon, G. B.; Gatehouse, B. M.; Nelson-Reed, K. T. Ibid. 1989, 359,
267. (d) Crocker, C.; Goodfellow, R. J .; Gimeno, J .; Uso´n, R. J . Chem.
Soc., Dalton Trans. 1977, 1448. (e) Bennet, R. L.; Bruice, M. I.;
Gardner, R. C. R. Ibid. 1973, 2653.
(2) Edelmann, F. T. Comments Inorg. Chem. 1992, 12, 259.
(3) (a) Gru¨tzmacher, H.; Pritzkow, H.; Edelmann, F. T. Organome-
tallics 1991, 10, 23. (b) Lay, U.; Pritzkow, H.; Gru¨tzmacher, H. J . Chem.
Soc., Chem. Commun. 1992, 260. (c) Vij, A.; Kirchmeier, R. L.; Willett,
R. D.; Shreeve, J . M. Inorg. Chem. 1994, 33, 5456.
(4) Brooker, S.; Buijink, J .-K. Edelmann, F. T. Organometallics
1991, 10, 25.
(5) Schluter, R. D.; Isom, H. S.; Cowley, A. H.; Atwood, D. A.; J ones,
R. A.; Olbrich, F.; Corbelin, S.; Lagow, R. J . Organometallics 1994,
13, 4058.
0276-7333/96/2315-2019$12.00/0 © 1996 American Chemical Society

2020 Organometallics, Vol. 15, No. 8, 1996
Bartolome´ et al.
Ta ble 2. Syn th eses of New Com p lexes w ith
Ta ble 1. 19F a n d 1H NMR Da ta for th e F m es Gr ou p
in th e Com p lexes Descr ibed in Th is Wor k
(Recor d ed a t 283.6 a n d 300 MHz in CDCl3 a t Room
Tem p er a tu r e Un less Oth er w ise Sta ted )
Rea ction s Ca r r ied Ou t a t 40 °C for 24 h Un less
Oth er w ise In d ica ted
starting
material
amt,
mmol
molar
ratioa
product(s)
(yield, %)
compd
ortho-CF3
para-CF3
Ha
a
a
trans-PdCl2(tht)2
trans-PdCl2(tht)2
trans-PdCl2(PPh3)2
PdCl2(COD)
PdCl2(bipy)
PdCl2(bipy)
1.00
0.75
0.50
0.50
1.50
0.50
1/2
1/4
1/2
1/2
1/2b
1/4c
1 (67), 2 (4)
2 (47)
3 (52)
4 (34)
5 (14), 6 (25)
6 (30)
trans-Pd(Fmes)Cl(tht)2, 1
trans-Pd(Fmes)2(tht)2, 2
trans-Pd(Fmes)Cl(PPh3)2, 3 -58.6 (t, 5.6)
Pd(Fmes)Cl(COD), 4
Pd(Fmes)Cl(bipy), 5
Pd(Fmes)2(bipy), 6
-60.1
-59.8
-63.1
-63.1
-63.3
-63.4
-63.0
-63.1
7.88
7.90
7.08b
7.86
7.92
7.79
-57.0
-59.2
-57.7
a
b
Chloro complex/LiFmes. 5 h. c 7 h.
a
Singlets unless otherwise indicated (multiplicity, J PF in Hz).
At -60 °C.
b
more important for Fmes. (b) M‚‚‚F interactions are
frequently found in Fmes complexes involving the
fluorine atoms of the ortho-CF3.2 (c) The Fmes com-
plexes should show a high degree of axial protection of
the square-planar configuration, higher than those
found for mesityl or ortho-C6H4(CF3) groups.10 We
report here the first complexes and X-ray structures
containing the Fmes group attached to palladium(II)
centers.
Resu lts a n d Discu ssion
F igu r e 1. Molecular structure of 2 showing low-occupancy
disordered fluorine atoms. All hydrogen atoms have been
omitted for clarity.
All the complexes containing Fmes described so far
have been synthesized from its lithium derivative, Li-
(Fmes), which is easily produced by treating 1,3,5-tris-
(trifluoromethyl)benzene (FmesH) with LiBu and may
be used in situ.7a,11 The same method is used here, since
attempted alternative methods were unsuccessful. Thus,
the acidity of the hydrogens in FmesH is not sufficient
to eliminate Hacac from [Pd(acac)2] (no reaction after 5
h in refluxing toluene), whereas the reaction of [Pd(µ-
Cl)(η3-C3H5)]2 with excess of FmesH in refluxing aceto-
nitrile leads to deposition of metallic palladium. The
presence of ancillary ligands seems important in obtain-
ing well-defined (Fmes)palladium complexes, since the
reaction of PdCl2 with excess of Li(Fmes) for 24 h at 40
°C gave only a very small amount of an orange oil, which
was a complex mixture of species by 19F NMR. This is
in contrast with the ready isolation of [Ni(Fmes)2] and
[Co(Fmes)2], which have been described recently.8 It is
well-known that low-coordinate complexes are more
easily obtained for smaller metals.
Therefore, the (Fmes)palladium(II) complexes de-
scribed here were synthesized by treating Li(Fmes) with
a variety of chloro complexes of palladium(II). Table 1
lists selected NMR data for the new complexes, and
Table 2 gives the reaction conditions, products, and
yields. An excess of Li(Fmes) (1:2 or 1:4) and moderate
heating (40 °C) were used to promote the reaction with
the bulky Fmes anion. These conditions usually induce
decomposition and some deposition of metallic pal-
ladium but avoid the presence of unreacted chloro
complexes, difficult to separate from the arylated prod-
ucts. In order to test the behavior of the ligand in
different geometries, the following palladium(II) chloro
complexes were chosen: trans-[PdCl2L2] (L ) neutral
monodentate ligand), to obtain mono- or bis-arylated
trans complexes; [PdCl2(L-L)] (L-L ) neutral bidentate
ligand), to isolate mono- or bis-arylated cis complexes.
The products obtained from the reactions of [PdCl2L2]
with an excess of Li(Fmes) depend on the size of L.
When the bis-arylated complex can be formed, its
formation is detected in even the 1/2 ratio reaction. This
is the case for tht (tetrahydrothiophene) and bipy (2,2′-
bipyridine) complexes, whereas for PPh3 and COD (1,5-
cyclooctadiene), which are more sterically demanding
above and below the Pd(II) coordination plane, only the
mono-arylated species are formed.
(A) Ar yla tion of tr a n s-[P d Cl2L2]. As shown in
Table 2, the reaction of trans-[PdCl2(tht)2] with a 2-fold
excess of Li(Fmes) leads to a 67% yield of orange trans-
[Pd(Fmes)Cl(tht)2], 1, and a 4% yield of pale yellow
trans-[Pd(Fmes)2(tht)2], 2. The latter is selectively
isolated in 47% yield when the reactant ratio used is
1/4. The presence of a chloro ligand in 1 is evident from
its elemental analysis and in its IR spectrum which
shows ν(Pd-Cl) at 290 cm-1
. The proposed trans
geometry is confirmed by the equivalence of both tht
1
ligands observed in the H NMR spectrum (see Experi-
mental Section). The trans geometry of 2 is not evident
from its spectroscopic data but is proved by X-ray crystal
structure analysis.
A perspective view of the molecular structure of 2 is
given in Figure 1, and selected distances and angles are
listed in Table 3. The crystal structure consists of
isolated molecules separated by normal van der Waals
contacts. Molecules of 2 show an approximately square-
planar palladium(II) atom coordinated by two tht ligands
and two Fmes ligands in trans positions. The two Pd-C
bond lengths differ slightly (Pd-C(1) 2.083(5), Pd-C(10)
2.114(5) Å), while the Pd-S distances are essentially
identical (Pd-S(1) 2.319(2), Pd-S(2) 2.311(2) Å). These
Pd-C distances are somewhat longer than typical Pd-C
(10) (a) Ceder, R. M.; Cubillo, J .; Muller, G.; Rocamora, M.; Sales,
J . J . Organomet. Chem. 1992, 429, 391. (b) Rieger, A. L.; Carpenter,
G. B.; Rieger, P. H. Organometallics 1992, 11, 842. (c) Fallis, K. A.;
Anderson, G. K.; Rath, N. P. Organometallics 1992, 11, 2423. (d) Klein,
A.; Kaim, W. Organometallics 1995, 14, 1176.
(11) Scholz, M.; Roesky, H. N.; Stalke, D.; Keller, K.; Edelmann, F.
T. J . Organomet. Chem. 1989, 366, 73. X-ray structure of [Et2O‚LiFmes]2:
Stalke, D.; Whitmire, K. H. J . Chem. Soc., Chem. Commun. 1990, 833.

(Tris(trifluoromethyl)phenyl)palladium(II) Complexes
Organometallics, Vol. 15, No. 8, 1996 2021
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 2
angles being larger than the Cmeta-Cortho-CF3 angles
by 4 or 10° (ca. 120 vs 116° for one of the Fmes ligands
and ca. 123 vs 113° for the other Fmes group; see Table
3). The lengthening of the Pd-C bond, these angular
distortions, and the displacement of the metal from the
C6 plane are all consistent with a high degree of steric
crowding resulting from the presence of the CF3 ortho
substituents.
Pd-C(1)
Pd-S(2)
2.083(5)
2.311(2)
Pd-C(10)
Pd-S(1)
2.114(5)
2.319(2)
C(1)-Pd-C(10)
C(10)-Pd-S(2)
C(10)-Pd-S(1)
C(2)-C(1)-C(6)
C(6)-C(1)-Pd
C(3)-C(2)-C(7)
C(4)-C(3)-C(2)
C(5)-C(4)-C(8)
C(4)-C(5)-C(6)
C(5)-C(6)-C(9)
F(3)-C(7)-C(2)
F(2)-C(7)-C(2)
F(5′)-C(8)-C(4)
F(6)-C(8)-C(4)
F(5)-C(8)-C(4)
F(9)-C(9)-C(6)
178.9(2)
87.81(13) C(1)-Pd-S(1)
86.54(13) S(2)-Pd-S(1)
C(1)-Pd-S(2)
92.30(13)
93.44(13)
172.62(5)
124.3(4)
123.5(5)
120.2(4)
120.3(5)
119.6(5)
123.1(5)
120.8(4)
112.8(4)
114.5(5)
121.3(14)
101.5(14)
112.9(5)
112.6(5)
124.3(4)
113.8(4)
121.9(4)
116.2(5)
119.7(5)
120.0(5)
119.6(5)
116.1(4)
113.2(4)
112.8(4)
117.8(11)
113.9(5)
113.2(5)
112.6(5)
C(2)-C(1)-Pd
C(3)-C(2)-C(1)
C(1)-C(2)-C(7)
C(5)-C(4)-C(3)
C(3)-C(4)-C(8)
C(5)-C(6)-C(1)
C(1)-C(6)-C(9)
F(1)-C(7)-C(2)
F(4)-C(8)-C(4)
F(6′)-C(8)-C(4)
F(4′)-C(8)-C(4)
F(8)-C(9)-C(6)
F(7)-C(9)-C(6)
C(11)-C(10)-Pd
It is interesting to compare these short Pd‚‚‚F dis-
tances with other cases of short M‚‚‚X “contacts”. For
this we use the parameter F, defined as experimental
distances/sum of the covalent radii, d/[r(M) + r(X)],13
and take r(F) ) 0.64 Å,14 as used in the reference (a
shorter r(F) value is given in more modern texts,15 which
would make all F values where F is involved about 0.05
larger). In complex 2, F ) 1.51 for the shortest Pd‚‚‚F(12)
distance (2.897 Å), this value being somewhat larger
than those reported for the o-F‚‚‚Ag contacts in a large
series of binuclear C6F5Pt-Ag complexes, which are in
the range 1.31-1.48.13 There are no previous reports
on Pd‚‚‚F contacts, but the shortest Pd‚‚‚O contact
reported (2.651 Å) gives F ) 1.32.16 Larger distances
(about 3 Å), but smaller F values (1.28 for the shortest
distance), are found for Pd‚‚‚S contacts.17 Other fluo-
romesityl complexes show M‚‚‚F contacts in the ranges
F ) 1.31-1.39 for Sn(II),3a F ) 1.28-1.36 for Pb(II),4 F
) 1.38-1.49 for Zn(II), F ) 1.36-1.43 for Cd(II), F )
1.50-1.58 for Hg(II),7b F ) 1.41-1.51 for Ga(III),5 and
F ) 1.27-1.31 for In(III).6 Whereas the presence of
bonding interactions has been concluded in all these
cases of short contacts in which the metal atoms are
coordinatively unsaturated, we feel that in 2 an extra
covalent interaction between a soft 16e palladium center
and a hard fluorocarbon fluorine atom is unlikely.
Indeed, the geometrical distortions observed in the
complex seem to occur in order to allow for a larger
nonbonding Pd‚‚‚F distance, as discussed below.
The fluorine atoms in the ortho-CF3 group are all
equivalent when the complex is in solution, giving rise
to one singlet in the 19F NMR at room temperature
(Table 1). Low-temperature NMR spectra were re-
corded to see whether the rotation of the CF3 group
might be slowed down due to the high steric crowding.
However, the spectra remain invariant even at -90 °C
in CD2Cl2 solution.
A different situation is found in trans-[Pd(Fmes)Cl-
(PPh3)2], 3. This complex is obtained in a 52% yield as
a white solid from the 1:2 reaction of trans-[PdCl2-
(PPh3)2] and Li(Fmes). As indicated before, no bis-
arylated species are detected in this reaction. The
coordination of the chlorine atom in 3 is confirmed by
C(11)-C(10)-C(15) 113.1(4)
C(15)-C(10)-Pd 122.5(4)
C(12)-C(11)-C(10) 123.2(5)
C(10)-C(11)-C(16) 123.6(4)
C(12)-C(13)-C(14) 119.8(5)
C(14)-C(13)-C(17) 120.2(5)
C(14)-C(15)-C(10) 123.6(5)
C(10)-C(15)-C(18) 122.8(4)
F(10)-C(16)-C(11) 112.6(5)
F(12′)-C(16)-C(11) 117.9(24)
F(11)-C(16)-C(11) 111.2(5)
F(13)-C(17)-C(13) 116.4(5)
F(14)-C(17)-C(13) 112.9(6)
F(15)-C(17)-C(13) 113.4(5)
F(17′)-C(18)-C(15) 115.6(12)
F(17)-C(18)-C(15) 114.5(5)
F(18)-C(18)-C(15) 112.9(4)
C(12)-C(11)-C(16) 113.2(5)
C(13)-C(12)-C(11) 120.5(5)
C(12)-C(13)-C(17) 120.0(5)
C(13)-C(14)-C(15) 119.7(5)
C(14)-C(15)-C(18) 113.6(5)
F(11′)-C(16)-C(11) 113.1(21)
F(12)-C(16)-C(11) 116.5(4)
F(10′)-C(16)-C(11) 105.9(22)
F(15′)-C(17)-C(13) 116.3(9)
F(14′)-C(17)-C(13) 109.4(9)
F(13′)-C(17)-C(13) 112.5(8)
F(18′)-C(18)-C(15) 118.0(11)
F(16)-C(18)-C(15) 115.3(5)
F(16′)-C(18)-C(15) 108.2(10)
lengths in Pd-C6F5 complexes [which average 2.025(6)
Å (sample standard deviation 0.036 Å) in 33 examples
from the Cambridge Structural Database]. The Pd-S
distances are in the usual range for Pd(II)-tht com-
plexes [which average 2.321(5) Å (sample standard
deviation 0.012 Å) in 7 examples from the Cambridge
Structural Database]. The coordination angles at pal-
ladium are near the square planar ideal, but the cis
angles involving the shorter Pd-C bond are larger than
those for the other (C(1)-Pd-S(1) 92.30(13), C(1)-Pd-
S(2) 93.44(13), C(10)-Pd-S(1) 86.54(13), C(10)-Pd-
S(2) 87.81(13)°). The palladium atom lies somewhat out
of the mean plane of the aryl groups (by 0.079 and 0.105
Å for rings C(1-6) and C(10-15), respectively; cf. mean
carbon atom displacements of 0.006 and 0.005 Å).
The geometry of the aryl ligands is similar to that
observed in other complexes of the Fmes ligand which
do not contain ancillary ligands,3-6,7b showing that the
presence of the two tht groups does not substantially
affect the geometry of the fluoroaryl ligand. Thus the
C-C-C angle at the ipso carbon is significantly less
than 120° (ca. 113° in 2) and those at the ortho carbons
rather larger than 120° (ca. 123° in 2) as a result of the
electronic effects of the electropositive metal and elec-
tronegative CF3 substituents at these positions.12 The
ortho-CF3 groups lie close to the axial sites above and
below the palladium coordination plane, with the short-
est Pd‚‚‚F distances being Pd‚‚‚F(12) 2.897, Pd‚‚‚F(12′)
2.982, and Pd‚‚‚F(17′) 2.936 Å. The C-C-CF3 angles
show systematic distortions with the Cipso-Cortho-CF3
(13) (a) Uso´n, R.; Fornie´s, J .; Toma´s, M. J . Organomet. Chem. 1988,
358, 525. (b) Uso´n, R.; Fornie´s, J . Inorg. Chim. Acta 1992, 198-200,
165.
(14) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960; p 403.
(15) Emsley, J . The Elements, 2nd ed.; Oxford University Press:
Oxford, U.K., 1991.
(16) Dunbar, K. R.; Sun, J .-S. J . Chem. Soc., Chem. Commun. 1994,
2387.
(17) (a) Blake, A. J .; Gould, R. O.; Lavery, A. J .; Schro¨der, M. Angew.
Chem., Int. Ed. Engl. 1986, 25, 274. (b) Wieghardt, K.; Ku¨ppers, H.-
J .; Raabe, E.; Kru¨ger, C. Ibid. 1986, 25, 1101. (c) Blake, A. J .; Holder,
A. J .; Hyde, T. I.; Roberts, Y. V.; Lavery, A. J .; Schro¨der, M. J .
Organomet. Chem. 1987, 323, 261. (d) Grant, G. T.; Sanders, K. A.;
Setzer, W. N.; VanDerveer, D. G. Inorg. Chem. 1991, 30, 4053. (e) de
Groot, B.; Hanan, G. S.; Loeb, S. J . Inorg. Chem. 1991, 30, 4644. (f)
Blake, A. J .; Crofts, R. D.; de Groot, B.; Schro¨der, M. J . Chem. Soc.,
Dalton Trans. 1993, 485.
(12) (a) Domenicano, A.; Vaciago, A.; Coulson, C. A. Acta Crystal-
logr., Sect. B 1975, 31, 221. (b) Domenicano, A.; Murray-Rust, P.;
Vaciago, A. Acta Crystallogr., Sect. B 1983, 39, 457 and references
therein. (c) Norrestam, R.; Schepper, L. Acta Chem. Scand., Ser. A.
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2022 Organometallics, Vol. 15, No. 8, 1996
Bartolome´ et al.
tion) one phenyl ring to differ from the other two, the
signals of the first appearing at higher field than
normal, whereas those of the other two have normal
chemical shifts. The hydrogen signals of the shielded
phenyl group follow the sequence (δ in parentheses):
ortho-H (6.4) > meta-H (6.8) > para-H (7.0). Further-
more, a marked shielding is also found for the signal
due to the two hydrogens of the Fmes ligand (δ ) 7.08
in 3, vs 7.79-7.91 ppm for the rest of complexes herein
described; see Table 1). These observations may be
interpreted by postulating that the rotation around the
Pd-P bonds has been arrested at low temperature in
the arrangement shown in Figure 2, where the hydrogen
atoms of the fluoroaryl ligand and those of one of the
phenyl groups of each phosphine are subjected to high
shielding anisotropy due to interaction with the aryl
rings.
Restricted rotation around M-PR3 bonds has been
reported previously by several authors, associated with
stereochemically crowded systems.18 In 3, the activation
free energy measured at 208.8 K by spin saturation
transfer experiments (see Experimental Section) was
∆Gq ) 12.8 kcal mol-1, which is among the highest
values reported so far for a barrier to rotation around a
M-PPh3 bond. As ∆Sq for the rotation process has been
shown to be very close to zero, then ∆Gq ≈ ∆Hq, and a
comparison with other ∆Gq values measured at different
temperatures can be made.18b The ∆Gq values reported
for rotation of the bulky PtBu2R (R ) H, CH3, Ph) in
[MX(CO)(PtBu2R)2] (X ) Cl, Br, I; M ) Rh, Ir) are in
the range 12-16 kcal mol-1 18e-f
for PPh3 complexes lie in the range 8-10 kcal mol-1 18a-d
,
but the values reported
.
The highest value in the literature for PPh3 square-
planar complexes has been reported recently within the
series cis-[PtX2(Me2phen)(PPh3)] (Me2phen ) monoden-
tate 2,9-dimethyl-1,10-phenanthroline) were ∆Gq
)
10.2, 10.8, and 11.8 kcal mol-1 for X ) Cl, Br, and I,
respectively. The high-energy barrier to rotation in this
case has been attributed to a stacking interaction
between one phenyl ring of PPh3 and the aromatic
system of the Me2phen ligand acting as a type of
intramolecular brake, rather than to steric effects.18a
In order to ascertain whether the barrier to rotation
in our case was related to stacking interactions or to
steric effects, the complex trans-[Pd(C6F5)Cl(PPh3)2] was
studied. Only a slight broadening was observed in the
1H and 13C{1H} NMR at -90 °C in CD2Cl2, which means
F igu r e 2. 1H NMR spectra at different temperatures of 3
(* indicates CDCl3, 300 MHz).
that ∆Gq should be noticeably lower than 8 kcal mol-1
.
Consequently the barrier to rotation observed in 3 must
be attributed mostly to steric effects.
IR spectroscopy (ν(Pd-Cl) at 302 cm-1), and the trans
geometry is demonstrated by its 31P{1H} NMR spec-
trum, which shows only one signal (δ 21.3 ppm, septet,
J PF 5.6 Hz) showing the equivalence of the PPh3 ligands.
The 19F NMR spectrum shows one triplet for the ortho
CF3 coupled to two equivalent P atoms, consistent with
this structure assignment.
As stated above, the size of the ancillary ligands
greatly influences the products obtained in the synthe-
ses. This was confirmed by additional reactions of other
trans-[PdCl2(PR3)2] complexes with Li(Fmes), which
showed a clear dependence on the cone angle of the
phosphine. Thus, the reaction of [PdCl2(PMe3)2] with
The 19F and 31P{1H} NMR spectra remain invariant
from -60 °C to room temperature. However, the 1H
NMR spectrum of 3 at room temperature shows broad
signals for the aromatic hydrogens of the PPh3 ligand
which do not preclude the observation of the Fmes
hydrogens as a clean singlet (Figure 2). The spectrum
changes on heating at 60 °C toward a pattern more
typical of PPh3 hydrogens (although still somewhat
broad). On cooling of the sample at -60 °C the
spectrum shows (see Figure 2 and Experimental Sec-
(18) (a) Fanizzi, F. P.; Lanfranchi, N.; Natile, G.; Tiripicchio, A.
Inorg. Chem. 1994, 33, 3331. (b) Davies, S. G.; Derome, A. E.; McNally,
J . P. J . Am. Chem. Soc. 1991, 113, 2854 and references therein. (c)
Chudek, J . A.; Hunter, G.; MacKay, R. L.; Kremminger, P.; Schlo¨gl,
K.; Weissensteiner, W. J . Chem. Soc., Dalton Trans. 1990, 2001. (d)
Hunter, G.; Weakley, T. J . R.; Weissensteiner, W. Ibid. 1987, 1545
and references therein. (e) DiMeglio, C. M.; Luck, L. A.; Rithner, C.
D.; Rheingold, A. L.; Elcesser, W. L.; Hubbard, J . L.; Bushweller, C.
H. J . Phys. Chem. 1990, 94, 6255 and references therein. (f) Bush-
weller, C. H.; Rithner, C. D.; Butcher, D. J . Inorg. Chem. 1986, 25,
1610. (g) J ones, W. D.; Feher, F. J . Inorg. Chem. 1984, 23, 2376. (h)
Selnau, H. E.; Merola, J . S. Organometallics 1993, 12, 1583.

(Tris(trifluoromethyl)phenyl)palladium(II) Complexes
Organometallics, Vol. 15, No. 8, 1996 2023
4 equiv of Li(Fmes) led to a complex mixture which
could not be separated by column chromatography nor
fully identified by its NMR spectra. A mixture of cis
and trans isomers can be expected from the cis-trans
equilibrium observed in the solutions of the starting
material.19 Thus two (cis and trans) mono-arylated and
two bis-arylated species are possible, in addition to
dimeric species of the type [Pd2(µ-Cl)2(Fmes)2(PMe3)2]
(two possible isomers), or even more highly arylated
anionic species. Since the NMR spectra of the crude
product revealed the presence of more than four com-
plexes, it seems very likely that bis-arylated complexes
are present in the mixture. It appears then that the
small cone angle of PMe3 (118°)20 allows bis-arylated
complexes to be formed, whereas the bulkier PPh3 (145°)
stops the reaction at the mono-arylated complex. Fur-
thermore, trans-[PdCl2(PCy3)2] (Cy ) cyclohexyl) does
not react with Li(Fmes) and the starting material is
recovered unchanged. In this case, the phosphine is
presumably too bulky (cone angle 170°) and prevents
coordination of Fmes.
(B) Ar yla tion of [P d Cl2(L-L)]. The reaction of
[PdCl2(COD)] with Li(Fmes) using a 1:2 molar ratio
gives a 34% yield of [Pd(Fmes)Cl(COD)], 4, as a pale
yellow crystalline solid. This stoichiometry is supported
by the observation of ν(Pd-Cl) at 323 cm-1 in the IR
spectrum, the presence of signals due to two nonequiva-
lent halves of the COD ligand in the 1H NMR spectrum,
and the analytical data. The bis-arylated product, or
species resulting from insertion reactions of COD in the
Pd-C6H2(CF3)3 bond (as found for [Pd(C6F5)Cl(COD)]),21
were not detected in this reaction. The bis-arylated
product is probably disfavored due to severe steric
effects above and below the coordination plane. In
effect, a cis-bis-arylated complex is cleanly isolated when
the chelating ligand is confined to the coordination
plane, e.g. when using bipy instead of COD. Thus
reaction of [PdCl2(bipy)] with a 2- fold excess of Li(Fmes)
yields 14% of [Pd(Fmes)Cl(bipy)], 5, as a yellow solid,
and 26% of [Pd(Fmes)2(bipy)], 6, as an off-white solid;
using a 1:4 ratio and a longer reaction time only complex
6 is formed in 30% yield.
F igu r e 3. Two perspective views of the molecular struc-
ture of 6: (a) View showing low-occupancy disordered
fluorine atoms; (b) view with minor component disordered
fluorine atoms omitted for clarity.
Figure 3 shows two different perspective views of the
molecular structure of 6, and selected distances and
angles are listed in Table 4. The crystal consists of
isolated molecules separated by normal van der Waals
contacts. The two Fmes ligands are coordinated in a
cis arrangement, and the two nitrogen atoms of the 2,2′-
bipyridyl ligand occupy the other two coordination sites.
The Pd-C distances are very similar (Pd-C(1) 2.032(3),
Pd-C(10) 2.023(3) Å) and similar to typical Pd-C
lengths in Pd-C6F5 complexes as noted above. The
Pd-N distances (Pd-N(1) 2.110(2), Pd-N(2) 2.103(3)
Å) are normal and slightly shorter than those found in
the acyl complex [Pd(CO2Me)2bipy].23
The expected square-planar geometry is severely
distorted. Thus, the N(1)-Pd-N(2) angle is smaller
than 90° (78.83(9)°); this is normal for a small-bite
chelating ligand such as bipy and comparable to the
angle found in [Pd(CO2Me)2bipy] (77.6(3)°). The cis
angle involving the carbon atoms of the Fmes ligands
is larger than 90° (C(1)-Pd-C(10) 96.88(10)°). This is
in contrast with the C-Pd-C angle found in [Pd(CO2-
Me)2bipy] (87.0(5)°); presumably the opening of this
angle in 6 is imposed by steric constraints. With respect
to the plane described by the Pd, N(1), and N(2) atoms,
the 2-pyridyl groups are below (left in Figure 3a) and
above (right in Figure 3a) this plane (N-C-C-N torsion
angle ) 13.1(2)°), whereas the Pd-C bonds in cis
positions are respectively bent above and below, as is
The IR spectrum of 5 shows a Pd-Cl absorption at
1
340 cm-1, whereas the H NMR spectrum reveals the
presence of an asymmetric bipy, as the two ligands trans
to the nitrogen atoms are different. One H6 of the bipy
ligand, cis to the chloro ligand, appears clearly shielded.22
The analytical data for 6 support the presence of two
Fmes ligands in the complex, and the 1H NMR spectrum
suggests that the molecule is symmetrical with equiva-
lent Fmes groups and the two halves of the bipy ligand
equivalent. The presence of a cis-bis(Fmes) moiety in
6 prompted us to determine its solid structure by X-ray
diffraction, as there are no previous reports of complexes
containing two Fmes ligand with this geometry and also
as to provide a comparison with the structure of 2, which
contains a trans-bis(Fmes) moiety.
(19) Goodfellow, R. F.; Evans, J . G.; Goggin, P. L.; Duddell, D. A. J .
Chem. Soc. A 1968, 1604.
(20) McAuliffe, C. A. In Comprehensive Coordination Chemistry;
Wilkinson, G., Gillard, R. D., McCleverty, J . A., Eds.; Pergamon:
Oxford, U.K., 1987; Vol. 2, pp 1012-1029.
(21) Albe´niz, A. C.; Espinet, P.; J eannin, Y.; Philoche-Levisalles, M.;
Mann, B. E. J . Am. Chem. Soc. 1990, 112, 6594.
(22) (a) Byers, P. K.; Canty, A. J . Organometallics 1990, 9, 210. (b)
Ru¨lke, R. E.; Ernsting, J . M.; Spek, A. L.; Elsevier, C. J .; van Leeuwen,
P. W. N. M.; Vrieze, K. Inorg. Chem. 1993, 32, 5769.
(23) Smith, G. D.; Hanson, B. E.; Merola, J . S.; Waller, F. J .
Organometallics 1993, 12, 568.

2024 Organometallics, Vol. 15, No. 8, 1996
Bartolome´ et al.
Ch a r t 1. Sch em a tic Rep r esen ta tion s of th e
F r a gm en ts of 2 Dir ectly In volved in th e Cr ow d in g
a r ou n d th e P d Cen ter , w ith Releva n t Dista n ces
a n d An gles*
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 6
Pd-C(1)
Pd-N(1)
2.032(3)
2.110(2)
Pd-C(10)
Pd-N(2)
2.023(3)
2.103(2)
C(1)-Pd-C(10)
C(1)-Pd-N(1)
C(1)-Pd-N(2)
C(2)-C(1)-Pd
C(6)-C(1)-Pd
96.88(10) N(2)-Pd-N(1)
166.57(10) C(10)-Pd-N(1)
93.82(10) C(10)-Pd-N(2)
78.83(9)
92.38(10)
165.75(10)
118.6(2)
127.1(2)
119.3(2)
C(11)-C(10)-Pd
C(15)-C(10)-Pd
126.9(2)
C(2)-C(1)-C(6) 113.3(2)
C(1)-C(2)-C(3) 123.0(3)
C(1)-C(2)-C(7) 120.8(3)
C(3)-C(2)-C(7) 116.1(3)
C(2)-C(3)-C(4) 121.0(3)
C(3)-C(4)-C(5) 118.3(3)
C(3)-C(4)-C(8) 121.2(3)
C(5)-C(4)-C(8) 120.5(3)
C(4)-C(5)-C(6) 121.2(3)
C(5)-C(6)-C(1) 123.1(3)
C(5)-C(6)-C(9) 111.3(3)
C(1)-C(6)-C(9) 125.6(2)
C(2)-C(7)-F(1) 114.3(3)
C(2)-C(7)-F(2) 112.8(3)
C(2)-C(7)-F(3) 111.9(3)
C(4)-C(8)-F(4) 112.8(5)
C(4)-C(8)-F(4′) 111.4(5)
C(4)-C(8)-F(5) 111.4(4)
C(4)-C(8)-F(5′) 111.7(6)
C(4)-C(8)-F(6) 116.6(5)
C(4)-C(8)-F(6′) 110.4(5)
C(6)-C(9)-F(7) 110.7(3)
C(6)-C(9)-F(8) 110.2(2)
C(6)-C(9)-F(9) 117.6(2)
C(11)-C(10)-C(15) 114.0(2)
C(10)-C(11)-C(12) 122.9(3)
C(10)-C(11)-C(16) 125.6(2)
C(12)-C(11)-C(16) 111.4(3)
C(11)-C(12)-C(13) 120.3(3)
C(12)-C(13)-C(14) 119.4(3)
C(12)-C(13)-C(17) 118.7(3)
C(14)-C(13)-C(17) 121.9(3)
C(13)-C(14)-C(15) 120.2(3)
C(14)-C(15)-C(10) 123.0(3)
C(14)-C(15)-C(18) 115.9(2)
C(10)-C(15)-C(18) 121.0(2)
C(11)-C(16)-F(10) 117.4(2)
C(11)-C(16)-F(11) 109.8(3)
C(11)-C(16)-F(12) 111.9(3)
C(13)-C(17)-F(13) 107.3(9)
C(13)-C(17)-F(13′) 114.0(6)
C(13)-C(17)-F(14) 112.7(5)
C(13)-C(17)-F(14′) 114.8(5)
C(13)-C(17)-F(15) 112.9(5)
C(13)-C(17)-F(15′) 112.0(5)
C(15)-C(18)-F(16) 113.9(2)
C(15)-C(18)-F(17) 113.2(3)
C(15)-C(18)-F(18) 112.1(2)
clearly shown in Figure 3a, leading to a marked distor-
tion of the square-planar coordination toward tetrahe-
dral.
120.5° vs ca. 116°; see Table 4). Therefore these
geometrical distortions seem to be forced in order to
allow for a larger nonbonding Pd‚‚‚F distance as dis-
cussed below.
The fluoroaryl groups are not perpendicular to the
coordination plane, as is common in all aryl derivatives,
but tilt in the same sense by 70.4 and 70.2°. Similar
behavior has been also observed in the closely related
structure of [PtMes2(bipy)].24 All these distortions may
be attributed to the high steric crowding in the complex
and help to keep the ortho-CF3 of the two Fmes ligands
apart from each other. Only one F atom of each Fmes
group comes close to the Pd atom leading to short
contacts Pd‚‚‚F(9) 2.788 Å (F ) 1.45) and Pd‚‚‚F(10)
2.766 Å (F ) 1.44), shorter than those found in 2 (see
above).
Finally, the geometry of the Fmes ligands in 6 is very
similar to that of 2 and of other Fmes compounds
reported.3-6,7b The C-C-C angle at the ipso-carbon is
significantly less than 120° (C(2)-C(1)-C(6) 113.3(2),
C(11)-C(10)-C(15) 114.0(2)°), and those at the ortho-
carbons are larger than 120° (ca. 123°), as reported in
other cases.12 The C-C-CF3 angles show also system-
atic distortions, with the Cipso-Cortho-CF3 angles being
always larger than the Cmeta-Cortho-CF3 angles. In
contrast to 2, the two Fmes ligands in 6 are almost
equivalent, each showing two very different ortho-CF3
substituents: one pseudo-apical (C(9)F3 and C(16)F3)
and one pseudo-equatorial (C(7)F3 and C(18)F3) with
respect to the metal center. For the pseudo-apical CF3
groups the Cipso-Cortho-CF3 and Cmeta-Cortho-CF3 angles
differ by ca. 14.5° (125.6° for both vs ca. 111°; see Table
4), whereas for the pseudo-equatorial ortho-CF3 groups
the corresponding difference is only about 4.5° (ca.
As in complex 2, the ortho-CF3 groups in 6 are
equivalent when the complex is in solution and give rise
to one singlet in the 19F NMR at room temperature
(Table 1). Since the bulk of the Fmes ligands excludes
their free rotation around the Pd-C bond (hindered also
in cis complexes with smaller aryls),9 the equivalence
must be achieved by a concerted tilting of the two Fmes
ligands, so that the average situation corresponds to the
Fmes coordinated perpendicular to the palladium square
plane. This movement cannot be completely stopped
even at -90 °C (CD2Cl2 solution), but the 19F NMR
spectrum at this temperature shows broadening of the
signal of the ortho-CF3 groups, whereas that of the para-
CF3 remains sharp.
Com p a r ison of th e Str u ctu r es of 2 a n d 6. Sche-
matic representations of the fragments of 2 and 6 more
directly involved in the crowding around the Pd center,
with relevant angles and distances, are shown in Charts
1 and 2, respectively. Two different kinds of steric
hindrance occur in the bis(Fmes) complexes: competi-
tion of two CF3 groups for the space close to the z axis
above and below the metal coordination plane (xy); the
short distances between the F atoms and the Pd atom
imposed by the bulkiness of the ortho substituents.
The two complexes studied adopt different strategies
to minimize the interactions between F atoms of the two
aryl rings, some of which are in the lowest limit expected
for F‚‚‚F nonbonding contacts (the literature F‚‚‚F van
der Waals distance is 2.8-3.00 Å).25 In the trans
complex 2 each Fmes group has its two ortho-CF3 groups
(24) Klein, A.; Hausen, H.-D.; Kaim, W. J . J . Organomet. Chem.
1992, 440, 207.
(25) Bondi, A. J . Chem. Phys. 1964, 68, 441 and references therein.

(Tris(trifluoromethyl)phenyl)palladium(II) Complexes
Organometallics, Vol. 15, No. 8, 1996 2025
Ch a r t 2. Sch em a tic Rep r esen ta tion s of th e
F r a gm en ts of 6 Mor e Dir ectly In volved in th e
Cr ow d in g a r ou n d th e P d Cen ter , w ith Releva n t
Dista n ces a n d An gles*
and Cortho-C-F (δ) angles. These differences are all
more marked than in the trans complex and strongly
suggest a direct relationship in the sense that short
Pd‚‚‚F distances are associated with larger Cipso-Pd‚‚‚F
and Cipso-Cortho-CF3 (γ) and Cortho-C-F (δ) angles,
which distortions allow for larger eclipsed Pd‚‚‚F dis-
tances.
Electr och em ica l Stu d ies on 2 a n d 6. Electro-
chemical studies were carried out on complexes 2 and
6 in dichloromethane as solvent in the range -1.8 to
+1.8 V to check whether oxidation accompanied by F
coordination might occur. Both complexes turned out
to be electrochemically inert in the range of potentials
studied, and this supports the view that the short Pd‚‚‚F
distances observed do not imply bonding interaction.
Con clu sion s
The coordination of two bulky 2,4,6-tris(trifluoro-
methyl)phenyl groups to palladium(II) does not lead to
the formation of coordinatively unsaturated species but
to very crowded basically square-planar complexes,
whether in the cis or in the trans isomer. However,
these bis-arylated complexes are not accessible for
ancillary ligands of medium size. The crowding in the
bis-arylated complexes produces very short nonbonding
Pd‚‚‚F and F‚‚‚F contacts.
The crowding seems to be the main reason for the
severe restriction observed to the rotation of the PPh3
ligands around the P-Pd bonds in trans-[Pd(Fmes)Cl-
(PPh3)2], since such restriction is not observed in the
electronically comparable trans-[Pd(C6F5)Cl(PPh3)2].
similarly disposed. The Fmes at the right in Chart 1
has two “staggered” CF3 groups each with two F atoms
at distances to Pd (d, average 3.240 Å) larger than the
sum of van der Waals radii (3.10-3.20 Å) and making
smaller Cipso-Pd‚‚‚F angles (R, average 64.2°); this
ligand shows the shorter Cipso-Pd distance (f) and
smaller Cipso-Cortho-CF3 angles (γ). The Fmes at the
left in Chart 1 has two CF3 groups with fluorine atoms
eclipsed relative to the palladium center with one F
atom at a short distance (d1, d2, 2.897, 3.135 Å) and
making larger Cipso-Pd‚‚‚F angles (R1, R2, 68.2, 64.9°).
This Fmes ligand shows the larger Cipso-Pd distance (f)
and larger Cipso-Cortho-CF3 angles (γ). These differ-
ences suggest that the distances and angles in the Fmes
with the eclipsed CF3 groups are somewhat distorted
in order to keep F(12) and F(18) as far from Pd as
possible.
Exp er im en ta l Section
Gen er a l Com m en ts. All reactions were carried out under
an atmosphere of dry dinitrogen. Diethyl ether was distilled
under nitrogen from sodium/benzophenone ketyl prior to use,
and the rest of solvents were purified according to standard
procedures.26 The complexes trans-[PdCl2(tht)2], trans-[PdCl2-
(PPh3)2], [PdCl2(COD)], [PdCl2(bipy)], and trans-[Pd(C6F5)Cl-
(PPh3)2] were prepared according to literature procedures.27
1,3,5-C6H3(CF3)3 (FmesH) was purchased from Fluorochem and
used as received. Li(Fmes) was prepared as described in the
literature,7a,11a using a ca. 0.6 M solution of FmesH in hexane,
and used immediately in situ without further purification.
Infrared spectra were recorded in a Perkin-Elmer 883
apparatus as Nujol mulls between polystyrene films from 4000
to 200 cm-1. NMR spectra were recorded on Bruker AC-300
or ARX-300 instruments at room temperature unless otherwise
stated. NMR spectra are referred to TMS, 85% aqueous H3-
PO4, and CFCl3. 19F NMR data for the new compounds are
collected in Table 2. Elemental analyses were performed on
a Perkin-Elmer 2400B microanalyzer. Cyclic voltammetry
experiments were carried out using a EG&G Model Versastat
253 in conjunction with a three-electrode cell under experi-
mental conditions described elsewhere.28
In the cis complex 6 each Fmes group has one ortho-
CF3 group in a staggered orientation with respect to the
metal (that in the pseudo-apical site; see above) and one
eclipsed (pseudo-equatorial), as is clearly seen in Figure
3b. As depicted in Chart 2, the two staggered CF3
groups, one in each in one Fmes group, have two F
atoms with Pd‚‚‚F distance larger than the sum of van
der Waals radii (all Pd‚‚‚F > 3.2 Å) and making smaller
Gen er a l Meth od for th e P r ep a r a tion of New Com -
p lexes. Molar ratios of the reactants, products, and yields
are collected in Table 2. The solid chloro complex was added
under nitrogen to a solution of Li(Fmes) in Et2O (10 mL/mmol
of lithium derivative). The reaction mixture was maintained
Cipso-Pd‚‚‚F angles (R, average 62.2°) and smaller Cipso
-
Cortho-CF3 angles (γ). The two eclipsed CF3 groups have
one F atom with a shorter Pd‚‚‚F distance (d1, d3, 2.766,
2.788 Å, noticeably shorter than in 2) and making larger
Cipso-Pd‚‚‚F angles (R1, R3, 74.2, 73.5°, noticeably larger
than in 2); they also have larger Cipso-Cortho-CF3 (γ)
(27) (a) Uso´n, R.; Fornie´s, J .; Mart´ınez, F.; Toma´s, M. J . Chem. Soc.,
Dalton Trans. 1980, 888. (b) J enkins, J . M.; Verkade, J . G. Inorg.
Synth. 1968, 11, 108. (c) Drew, D.; Doyle, J . R. Ibid. 1990, 28, 348. (d)
Wimmer, F. L.; Wimmer, S.; Castan, P. Ibid. 1992, 29, 185. (e) Uso´n,
R.; Royo, P.; Fornie´s, J .; Mart´ınez, F. J . Organomet. Chem. 1975, 90,
367.
(26) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: Oxford, U.K., 1988.
(28) Espinet, P.; Garc´ıa-Herbosa, G.; Ramos, J . M. J . Chem. Soc.,
Dalton Trans. 1990, 2931.

2026 Organometallics, Vol. 15, No. 8, 1996
Bartolome´ et al.
Ta ble 5. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for 2 a n d 6
at 40 °C for 24 h (see Table 2). Then two drops of water were
added to hydrolyze the excess of organolithium reagent, and
the volatiles were removed in vacuo. Once the reaction
mixture had been hydrolyzed, the filtrations on dry Celite and
purification procedures were performed under normal atmo-
sphere. The workup procedure is detailed below for each
compound. All the compounds obtained are air-stable solids.
Ar yla tion of tr a n s-[P d Cl2(th t)2]. The black residue was
extracted with 30 mL of CH2Cl2 and filtered. Hexane (15 mL)
was added to the yellow filtrate, and the solution was
concentrated in vacuo and cooled to -20 °C. The pale yellow
crystals thus obtained were decanted, washed with hexane (3
× 5 mL), and dried in vacuo, yielding trans-[Pd(Fmes)2(tht)2],
2. Anal. Calcd for C26H20F18PdS2: C, 36.96; H, 2.39. Found:
C, 36.72; H, 2.44. 1H NMR (CDCl3): δ 7.90 (s, 4 H, C6H2-
(CF3)3), 2.27 (m, 8 H, H2 of tht), 1.72 (m, 8 H, H3 of tht). IR:
1622 m, 1571 w, 1300 vs, 1283 vs, 1175 vs br, 1130 vs br, 1070
s, 1012 m, 912 m, 852 m, 836 m, 756 m, 686 s, 667 m, 441 m,
243 m.
When the reactant ratio used was 1:2 (see Table 2),
concentration of the mother liquor solution and cooling to -20
°C gave an orange solid, which was decanted, washed with
hexane (3 × 5 mL), and dried in vacuo, yielding trans-[Pd-
(Fmes)Cl(tht)2], 1. Anal. Calcd for C17H18ClF9PdS2: C, 34.45;
H, 3.02. Found: C, 34.17; H, 3.03. 1H NMR (CDCl3): δ 7.88
(s, 2 H, C6H2(CF3)3), 2.97 (m, 8 H, H2 of tht), 2.00 (m, 8 H, H3
of tht). IR: 1621 m, 1569 w, 1297 s, 1277 vs, 1193 vs, 1181
vs, 1140 vs, 1112 vs, 1087 s, 1027 m, 952 w, 916 m, 883 w br,
851 m, 834 m, 802 vw, 754 m, 693 m, 683 s, 520 vs, 468 w,
437 w, 290 w br, 230 m.
X-r a y Cr ysta llogr a p h ic An a lysis of tr a n s-[P d (F m es)2-
(th t)2], 2. Suitable crystals of 2 were grown by slow diffusion
of a concentrated dichloromethane solution of the complex into
hexane at room temperature. A crystal of 2 (approximate
dimensions 0.40 × 0.40 × 0.40 mm) was mounted in a glass
fiber and held in place with epoxy glue. All diffraction
measurements were made at room temperature on a Siemens
R3m diffractometer, using graphite monochromated Mo KR
X-radiation. Unit cell dimensions were determined from 20
centered reflections in the range 16.0 < 2θ < 29.3°. Diffracted
intensities were measured in a unique quadrant of reciprocal
space for 3.0 < 2θ < 50.0° by ω Wyckoff scans. Three check
reflections remeasured after every 150 ordinary data showed
no decay and variation of (2% over the period of data
collection. Of the 5701 intensity data (other than checks)
collected, 5205 unique observations remained after averaging
of duplicate and equivalent measurements (Rint ) 0.044) and
deletion of systematic absences all of which were used in
structure solution and refinement. An absorption correction
was applied based on 504 azimuthal scan data (maximum and
minimum transmission coefficients were 0.294 and 0.205).
Lorentz and polarization corrections were applied.
The structure was solved by Patterson and Fourier methods
and refined using the SHELXL-93 program.29 All non-
hydrogen atoms were assigned anisotropic displacement pa-
rameters. All hydrogen atoms were constrained to idealized
geometries and their positions refined riding on their parent
carbon atoms with a common thermal isotropic parameter. In
four of the six CF3 groups [C(8), C(16), C(17), and C(18)] the
fluorine atoms show a rotational disorder over two set of
positions related by a pseudo-2-fold axis approximately coin-
cident with the Cipso-CF3 bond. In the four cases the oc-
cupancy of one of the sets is clearly bigger than for the other
[0.83(1) in the case of the C(8) group, 0.91(1) for C(16), 0.68(1)
for C(17), and 0.81(1) for C(18)]. The geometry of all the CF3
groups was restrained using the DFIX and SAME instructions.
Common thermal parameters for the pseudo-2-fold related
fluorine atoms in the disordered CF3 groups were applied using
the EADP instruction. Full-matrix least squares refinement
compd 2
compd 6
empirical formula
fw
C26H20F18PdS2
844.94
C28H12F18N2Pd
824.80
temp (K)
293
293
wavelength (Å)
cryst system
space group
unit cell dimens
0.710 73
monoclinic
P21/n
a ) 11.976(5) Å
b ) 15.257(4) Å
c ) 16.299(5) Å
â ) 93.85(3)°
2971.3(17)
4
0.710 73
monoclinic
P21/n
a ) 9.029(5) Å
b ) 18.824(7) Å
c ) 16.603(5) Å
â ) 96.23(4)°
2805(2)
V (Å3)
Z
4
Dcalc (Mg/m3)
1.896
0.900
1.953
0.806
abs coeff (mm-1
)
F(000)
1664
1608
crystal size (mm)
2θ range for data
collcn (deg)
0.40 × 0.40 × 0.40
0.50 × 0.40 × 0.45
3-50
3-50
index ranges
0 e h e 14
0 e k e 18
-19 e l e 19
5470
0 e h e 10
0 e k e 22
-19 e l e 19
5266
reflcns collcd
indepdt reflcns
refinement method
data/restraints/
params
5205 [R(int) ) 0.0435] 4934 [R(int) ) 0.0203]
full-matrix least-squares on F2
5199/54/465
1.055
4932/12/533
1.370
goodness-of-fit
on F2
final R indices
[I > 2σ(I)]a
R1 ) 0.0650
wR2 ) 0.1692
R1 ) 0.0284
wR2 ) 0.0735
R1 ) 0.0363
wR2 ) 0.0775
0.43 and -0.37
R indices (all data)a R1 ) 0.0746
wR2 ) 0.1962
largest diff peak
2.55 and -1.58
and hole (e Å-3
)
a
R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) [∑[w(Fo2 - Fc2)2/∑[w(Fo2)2]1/2
;
goodness-of-fit ) [∑w(Fo - Fc2)2/(no. reflcns - no. params)]1/2
.
2
of this model (465 parameters) on F2 converged to final residual
indices R1 ) 0.065, wR2 ) 0.0169 [for the 4411 reflections
with I > 2σ(I)], and S ) 1.06 for all data. Weights, w, were
set equal to [σc2(Fo2) + (aP)2]-1, where σc2(Fo2) ) variance in
Fo2 due to counting statistics, P ) [max(Fo2,0) + 2Fc2]/3, and a
) 0.15 was chosen to minimize the variation in S as a function
of Fo. Final difference electron density maps showed features
in the range +2.55 to -1.58 e Å-3; the largest features (2.55,
2.45, 1.09, and 1.01 e Å-3) lie within 1 Å of the metal atom.
These and further details are listed in Table 5, while Table 6
lists the final atomic positional parameters for the freely
refined atoms.
Ar yla tion of tr a n s-[P d Cl2(P P h 3)2]. The brown residue
was extracted with 20 mL of toluene and filtered. Concentra-
tion of the brown filtrate and cooling to -20 °C gave white
crystals, which were decanted, washed with hexane (3 × 10
mL), and dried in vacuo, yielding trans-[Pd(Fmes)Cl(PPh3)2],
3. Anal. Calcd for
C45H32ClF9P2Pd: C, 57.04; H, 3.40.
Found: C, 57.18; H, 3.51. 1H NMR (CDCl3, -60 °C): δ 8.05
(m, 8 H, ortho-C6H5), 7.50 (m, 12 H, meta- and para-C6H5),
7.08 (s, 2 H, C6H2(CF3)3), 7.01 (t, J 7.4 Hz, 2 H, para-C6H5),
6.76 (t, J 7.6 Hz, 4 H, meta-C6H5), 6.40 (m, 4 H, ortho-C6H5).
31P{1H} NMR (121.4 MHz, CDCl3, room temperature): δ 21.3
(sept, J PF 5.6 Hz). IR: 1621 w, 1576 vw, 1373 s, 1284 vs, 1260
s, 1180 vs, 1131 vs, 1094 s, 1023 w, 1002 vw, 908 m, 833 vw,
744 s, 694 s, 518 vs, 442 s br, 302 s br.
Sp in Sa tu r a tion Tr a n sfer (SST) Exp er im en t. A ca. 0.02
M solution of 3 in carefully degassed CDCl3 was prepared in
a 5 mm NMR tube. The experiments were carried out at 208.8
K. T1 (0.9 s) was determined by the 180-τ-90 pulse sequence.
The decoupler power was adjusted so that complete saturation
of the peak was observed after irradiation for at least five T1
(10 s). The extent of saturation transfer was ascertained by
examining difference spectra resulting from subtraction of data
collected with and without saturation at the resonances of the
ortho-phenylic hydrogens (A ) 6.40 or B ) 8.05 ppm). A SST
(29) SHELXTL version 5.03, Siemens Analytical Xray, Madison, WI,
1994.

(Tris(trifluoromethyl)phenyl)palladium(II) Complexes
Organometallics, Vol. 15, No. 8, 1996 2027
Ta ble 6. Atom ic Coor d in a tes (×104) a n d
Equ iva len t Isotr op ic Disp la cem en t P a r a m eter s (Å2
× 103) for 2, w ith U(eq) Defin ed a s On e-Th ir d of
th e Tr a ce of th e Or th ogon a lized Uij Ten sor
Ta ble 7. Atom ic Coor d in a tes (×104) a n d
Equ iva len t Isotr op ic Disp la cem en t P a r a m eter s (Å2
× 103) for 6, w ith U(eq) Defin ed a s On e-Th ir d of
th e Tr a ce of th e Or th ogon a lized Uij Ten sor
x
y
z
U(eq)
x
y
z
U(eq)
Pd
S(1)
S(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
F(1)
F(2)
F(3)
C(8)
1084(1)
1293(1)
630(1)
2182(1)
2481(1)
1880(1)
1362(3)
443(3)
1228(1)
2626(1)
-145(1)
1258(3)
1344(3)
1328(3)
1251(3)
1181(3)
1190(3)
1432(3)
2078(2)
774(2)
1543(3)
1216(4)
1804(16)
1543(21)
570(13)
1927(3)
814(5)
32(1)
43(1)
45(1)
36(1)
38(1)
44(1)
47(1)
45(1)
40(1)
48(1)
68(1)
67(1)
71(1)
67(2)
95(2)
88(2)
160(5)
160(5)
95(2)
88(2)
53(1)
97(2)
83(1)
82(1)
36(1)
38(1)
45(1)
45(1)
45(1)
37(1)
49(1)
110(3)
79(2)
97(2)
97(2)
110(3)
79(2)
61(2)
125(4)
144(5)
112(3)
112(3)
125(4)
144(5)
46(1)
79(2)
101(3)
86(2)
101(3)
86(2)
79(2)
57(1)
96(3)
125(5)
68(2)
69(2)
130(5)
103(3)
78(2)
Pd
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
F(1)
F(2)
F(3)
C(8)
9164(1)
8959(3)
9629(3)
9487(3)
8691(4)
8063(3)
8209(3)
10597(3)
9880(3)
11297(3)
11694(3)
8523(5)
9660(10)
8635(16)
7369(13)
7394(19)
9708(13)
8189(22)
7526(3)
6135(2)
8273(3)
7438(2)
7975(3)
8697(3)
7956(4)
6448(3)
5675(4)
6422(3)
10310(3)
11178(2)
10385(2)
10965(2)
5686(5)
5537(27)
6159(14)
4325(10)
4270(8)
5874(10)
6330(9)
5463(3)
5729(2)
4011(2)
5643(2)
9242(3)
10749(2)
8357(4)
8316(4)
9216(5)
10138(4)
10135(3)
11088(3)
12268(4)
13098(4)
12726(4)
11565(3)
2768(1)
2150(1)
2263(1)
1790(2)
1175(2)
1027(2)
1490(1)
2890(2)
3504(1)
2863(1)
2937(1)
669(2)
8165(1)
9150(2)
9954(2)
10581(2)
10452(2)
9677(2)
9047(2)
10156(2)
10109(1)
10910(1)
9676(1)
11128(2)
11702(4)
10886(4)
11458(10)
10947(6)
11316(13)
11779(5)
8249(2)
8307(1)
8059(1)
7615(1)
8511(2)
8638(2)
8828(2)
8878(2)
8723(2)
8547(2)
8528(2)
8447(2)
7858(2)
9124(2)
9068(2)
8502(12)
9801(4)
9261(5)
9089(6)
8551(5)
9738(5)
8343(2)
8858(1)
8323(2)
7610(1)
6992(1)
7717(1)
6630(2)
5821(2)
5366(2)
5725(2)
6544(2)
6974(2)
6650(2)
7080(2)
7826(2)
8123(2)
31(1)
33(1)
38(1)
46(1)
48(1)
46(1)
37(1)
52(1)
79(1)
79(1)
82(1)
74(1)
103(3)
115(3)
177(5)
123(5)
176(8)
115(5)
46(1)
88(1)
84(1)
61(1)
34(1)
38(1)
45(1)
45(1)
42(1)
35(1)
50(1)
71(1)
89(1)
93(1)
65(1)
242(13)
109(5)
58(3)
143(5)
99(2)
150(5)
44(1)
61(1)
73(1)
64(1)
38(1)
37(1)
49(1)
63(1)
68(1)
58(1)
39(1)
38(1)
50(1)
59(1)
57(1)
47(1)
2479(4)
2435(4)
3365(4)
4403(4)
4518(4)
3573(4)
1335(5)
808(3)
-97(4)
266(4)
1155(4)
1694(3)
-7(3)
282(3)
106(2)
-872(2)
-312(4)
45(19)
-1090(11)
-331(29)
-579(8)
-1075(3)
15(4)
614(3)
1434(3)
5393(5)
6099(21)
5342(22)
5980(26)
5810(8)
5167(5)
6191(5)
3770(4)
4847(3)
3437(4)
3249(4)
-313(4)
-1435(4)
-2341(4)
-2173(4)
-1110(5)
-203(4)
-1780(4)
-1925(60)
-2742(27)
-1078(40)
-2583(5)
-2185(9)
-991(3)
-3143(5)
-3253(21)
-2952(22)
-4083(11)
-2910(6)
-3707(11)
-3904(10)
903(4)
F(4)a
F(5)a
F(6)a
F(4′)b
F(5′)b
F(6′)b
C(9)
F(7)
F(8)
F(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
F(10)
F(11)
F(12)
C(17)
F(13)b
F(14)b
F(15)b
F(13′)a
F(14′)a
F(15′)a
C(18)
F(16)
F(17)
F(18)
N(1)
690(5)
-9(3)
718(9)
F(4′)a
F(5′)a
F(6′)a
F(4)b
F(5)b
F(6)b
C(9)
F(7)
F(8)
F(9)
233(8)
314(11)
1016(5)
1186(2)
961(1)
791(5)
2660(4)
2852(3)
3123(3)
2988(3)
3035(3)
2752(3)
3330(4)
4212(4)
4539(4)
3962(3)
1806(4)
1578(35)
1677(30)
1235(28)
1632(3)
1584(4)
1226(3)
4821(4)
5336(20)
5383(19)
4474(11)
5656(4)
4709(9)
4712(10)
4414(3)
5166(13)
4011(17)
4576(25)
5255(3)
4323(6)
4086(5)
1980(5)
1692(8)
1450(9)
1863(6)
1373(5)
1944(9)
2562(7)
2845(5)
1096(4)
1034(4)
1718(3)
419(3)
615(1)
1602(1)
3604(1)
4266(1)
4880(2)
4868(2)
4248(2)
3631(1)
4417(2)
3871(1)
4807(1)
4807(1)
5545(2)
5865(7)
5796(5)
5443(6)
5481(5)
6095(3)
5848(4)
2994(2)
2456(1)
3130(1)
2733(1)
3189(1)
2099(1)
3687(2)
3841(2)
3465(2)
2953(2)
2823(1)
2274(1)
1960(2)
1445(2)
1255(2)
1596(2)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
F(10′)c
F(11′)c
F(12′)c
F(10)d
F(11)d
F(12)d
C(17)
F(13′)e
F(14′)e
F(15′)e
F(13)f
F(14)f
F(15)f
C(18)
F(16′)g
F(17′)g
F(18′)g
F(16)h
F(17)h
F(18)h
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
1193(3)
1203(3)
1223(3)
1223(3)
1203(3)
1187(3)
1171(3)
1936(11)
755(36)
886(42)
1657(5)
421(4)
1356(5)
1252(4)
603(14)
1854(17)
1441(22)
1291(11)
1908(8)
631(8)
1164(3)
1570(18)
1552(21)
450(8)
976(7)
1839(3)
596(4)
3158(4)
3981(5)
3895(5)
3219(4)
-720(4)
-1456(6)
-1584(5)
-785(4)
N(2)
847(19)
1754(17)
1279(19)
853(4)
1564(5)
1535(5)
162(5)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
693(8)
1832(9)
2392(6)
1708(6)
1841(11)
946(10)
557(8)
a
b
Occupancy 0.4. Occupancy 0.6.
irradiating either A or B signals are essentially equal (kchem(A)
) 0.186 ( 0.019 s-1; kchem(B) ) 0.20 ( 0.04 s-1). The free
energies of activation were calculated by using the Eyring
equation, averaging 12.8 kcal mol-1 (∆Gq(A) ) 12.77 ( 0.10
kcal mol-1; ∆Gq(B) ) 12.74 ( 0.19 kcal mol-1). Uncertainties
in the rate constants were calculated from the residuals of the
best-fit line drawn to the data, assuming a (0.01 error in the
a
b
d
Occupancy 0.17. Occupancy 0.83. c Occupancy 0.09. Occu-
pancy 0.91. e Occupancy 0.32. f Occupancy 0.68. g Occupancy 0.19.
Occupancy 0.81.
h
experiment was performed by irradiating one of the resonances
and observing magnetization transfer into the other signal
after variable delays (0.05-0.9 s). Plots of [Mz(H) - M∞(H)]
(30) (a) Sandstro¨m, J . Dynamic NMR Spectroscopy; Academic Press;
London, 1982; p 53 and references therein. (b) Faller, J . W. In
Determination of Organic Structures by Physical Methods; Nachod, F.
C., Zuckerman, J . J ., Eds.; Academic Press: New York, 1973; Vol. 5,
Chapter 5. (c) Sanders, J . K. M.; Hunter, B. K. Modern NMR
Spectroscopy, A Guide for Chemists; Oxford University Press: Oxford,
U.K., 1987; p 225.
vs t were analyzed by standard least-square fitting procedures.
30
Values of 1/τ1(H) thus obtained were used to calculate kobs
.
(kobs(A) ) 0.124 ( 0.013 s-1; kobs(B) ) 0.066 ( 0.013 s-1). Rates
of chemical exchange (kchem) were obtained as previously
outlined for a two-site exchange process between sites of
population 1 and 2 [kchem ) (3/2)kobs(A) ) 3kobs(B)].31 The
chemical rate constants thus obtained from SST experiments
(31) Green, M. L. H.; Wong, L.-L.; Sella, A. Organometallics 1992,
11, 2660.

2028 Organometallics, Vol. 15, No. 8, 1996
Bartolome´ et al.
integrals. The temperature was calibrated with a CH3OH
sample before and after the experiment and is accurate to
within 0.1 °C. The uncertainties in rates and temperature
were propagated to find the uncertainty in ∆Gq.
glass fiber with superglue. Unit cell dimensions were deter-
mined from 25 centered reflections in the range 15 < 2θ <
30°. A total of 5545 diffracted intensities (including checks)
were measured in a unique quadrant of reciprocal space for
3.0 < 2θ < 50.0° by Wyckoff ω scans. Three check reflections
remeasured after every 200 ordinary data showed no decay
and ca. (2% variation over the period of data collection. Of
the 5432 noncheck intensity data collected, 4932 unique
observations remained after averaging of duplicate and equiva-
lent measurements (Rint ) 0.0203) and deletion of systematic
absences and were retained for use in structure solution and
refinement. An absorption correction was applied in the basis
of 306 azimuthal scan data; maximum and minimum trans-
mission coefficients were 0.829 and 0.696, respectively. Lorentz
and polarization corrections were applied.
Ar yla tion of [P d Cl2(COD)]. The gray residue was ex-
tracted with 30 mL of CH2Cl2 and filtered. Hexane (15 mL)
was added to the yellow filtrate, and the solution was
concentrated in vacuo and cooled at -20 °C. The pale yellow
crystals obtained were decanted, washed with hexane (3 × 10
mL), and dried in vacuo, yielding [Pd(Fmes)Cl(COD)], 4. Anal.
Calcd for C17H14ClF9Pd: C, 38.44; H, 2.66. Found: C, 38.36;
H, 2.67. 1H NMR (CDCl3): δ 7.86 (s, 2 H, C6H2(CF3)3), 6.25
(m, 2 H, Holefinic of COD), 5.43 (m, 2 H, Holefinic of COD), 2.79
(m, 4 H, Haliphatic of COD), 2.59 (m, 4 H, Haliphatic of COD). IR:
1711 vw, 1621 w, 1301 s, 1284 vs, 1264 s, 1190 vs, 1123 vs,
1023 m, 914 m, 781 m br, 684 m, 568 w br, 437 m, 323 m, 300
w.
Ar yla tion of [P d Cl2(bip y)]. The green residue was ex-
tracted in a Soxhlet apparatus with 200 mL of refluxing
toluene. The brown solution obtained was filtered and con-
centrated in vacuo. Cooling at -20 °C gave yellow microcrys-
tals, which were decanted, washed with hexane (3 × 10 mL),
and dried in vacuo, yielding [Pd(Fmes)Cl(bipy)], 5. Anal.
Calcd for C19H10ClF9N2Pd: C, 39.41; H, 1.74; N, 4.84. Found:
C, 39.56; H, 1.90; N, 5.03. 1H NMR (CDCl3): δ 9.37 (d, J 4.3
Hz, 1 H, H6 of bipy), 8.08 (m, 4 H, H3, 2 H5 and H6 of bipy),
7.92 (s, 2 H, C6H2(CF3)3), 7.64 (m, 1 H, H4 of bipy), 7.57 (d, J
5.5 Hz, 1H, H3 of bipy), 7.32 (ddd, J 7.3, 5.6, and 1.8 Hz, 1H,
H4 of bipy). IR: 1619 m, 1603 m, 1571 m, 1300 vs, 1282 vs,
1265 vs, 1188 vs, 1128 m, 1106 m, 1085 m, 1036 m, 914 m,
854 m, 835 m, 767s, 755 w, 696 m, 684 s, 667 w, 649 w, 474 w,
439 w, 418 w, 396 vw, 374 vw, 340 m, 252 w.
Concentration of the mother liquors and cooling to -20 °C
afforded an off-white solid, which was decanted, washed with
hexane (3 × 5 mL), and dried in vacuo, yielding [Pd(Fmes)2-
(bipy)], 6. When the reaction was carried out with 4-fold excess
of Li(Fmes), the green residue was extracted with 30 mL of
CH2Cl2 and filtered. This yellow solution was concentrated
and chromatographed on a silica gel column using CH2Cl2 as
eluant. The solution obtained was evaporated to dryness and
the yellow residue was recrystallized from acetone/hexane to
give 6. Anal. Calcd for C28H12F18N2Pd: C, 40.78; H, 1.47; N,
3.40. Found: C, 40.88; H, 1.65; N, 3.62. 1H NMR (CDCl3): δ
8.12 (d, J 7.9 Hz, 2 H, H6 of bipy), 8.04 (ddd, J 7.8, 7.8, and
1.6 Hz, 2 H, H5 of bipy), 7.79 (s, 4 H, C6H2(CF3)3), 7.64 (d, J
5.3 Hz, 2 H, H3 of bipy), 7.36 (ddd, J 7.1, 5.5, and 1.3 Hz, 2 H,
H4 of bipy). IR: 1620 s, 1607 w, 1565 m, 1278 vs, 1192 s, 1163
vs, 1130 vs, 1098 vs, 1073 s, 1031 m, 1015 m, 923 m, 907 m,
852 m, 831 m, 761 s, 749 m, 692 m, 686 s, 663 w, 642 vw, 459
w, 437 w, 373 vw.
X-r a y Cr ysta llogr a p h ic An a lysis of [P d (F m es)2(bip y)],
6. Suitable crystals of 6 were grown by slow diffusion of a
concentrated acetone solution of the complex into hexane at
room temperature All diffraction measurements were made
with a Siemens four-circle R3m diffractometer, using graphite
monochromated Mo KR X-radiation on a single crystal (ap-
proximate dimensions 0.50 × 0.40 × 0.45 mm) mounted on a
The structure was solved by Patterson and Fourier methods
and refined using the SHELXL-93 program.29 All non-
hydrogen atoms were assigned anisotropic displacement pa-
rameters and, except for the disordered CF3 groups in the para
position on the aryl rings, refined without positional con-
straints. For the disordered CF3 groups restraints were
applied so that C-F distances were close to 1.33 Å and F‚‚‚F
distances close to 2.12 Å. Hydrogen atoms were located in the
Fourier maps and freely refined with a common thermal
isotropic parameter. Occupancies of the fluorine atoms of the
para-CF3 groups were initially refined and then fixed (at 0.4
and 0.6 for F(4-6, 13′-15′) and F(4′-6′, 13-15), respectively).
Refinement of the 533 least-squares variables converged
smoothly to residual indices R1 ) 0.028, wR2 ) 0.0074 [for
the 4266 reflections with I > 2σ(I)], and S ) 1.37 for all data.
2
Weights, w, were set equal to [σc2(Fo2) + (aP)2]-1, where σc2(Fo
)
) variance in Fo2 due to counting statistics, P ) [max(Fo2,0) +
2Fc2]/3, and a ) 0.04 was chosen to minimize the variation in
S as a function of Fo. Final difference electron density maps
showed no features outside the range +0.43 to -0.37 e Å-3
,
the largest features being close to the fluorine atoms. Table
5 reports the details of the structure analysis, and Table 7,
the atomic positional parameters.
Ack n ow led gm en t. The authors in Valladolid thank
the DGICYT of Spain for financial support (Project
PB93-0222). The collaboration was under the sponsor-
ship of the European Community (Contract CHRX-
CT93-0147 (DG 12 DSCS)). A.M. thanks the Spanish
Ministerio de Educacio´n y Ciencia for a FPU (Becas en
el extranjero) grant. We also thank Asuncio´n Mun˜oz
(Universidad de Burgos, Burgos, Spain) for performing
the electrochemical experiments.
Su p p or tin g In for m a tion Ava ila ble: For the crystal
structures of 2 and 6, complete tables of bond distances and
angles, anisotropic thermal parameters for the non-hydrogen
atoms, and hydrogen atom positions and isotropic thermal
parameters (6 pages). Ordering information is given on any
current masthead page.
OM950851T