Neutral organometallic palladium(II) aquo complexes

Article abstract of DOI:10.1021/om020198r

The reactions of chlorobridged cyclometalated complexes [Pd(C-N)(μ-Cl)]₂ (C-N = orthometalated N, N-dimethylbenzylamine, dmba; 2-(para-tolyl)pyridine, p-tolpy; azobenzene, azb; N,N-dimethyl-1-naphthylamine, dmna; and 2-benzylpyridine, bzpy) with Li(Fmes) (Fmes = 2,4,6-tris(trifluoromethyl)phenyl or nonafluoromesityl) give, after hydrolysis, neutral aquo complexes |Pd(C-N)(Fmes)(OH₂)], where the ipso carbon atoms of the Fmes and the cyclometalated ligand are coordinated cis, as shown by an X-ray diffraction study of [Pd-(dmba)(Fmes)(OH₂)]. The aquo ligand is readily displaced by other ligands, giving complexes [Pd(C-N)(Fmes)L] (L = PPh₃, 2,6-lutidine, NH₃, CN^tBu, CO) when monodentate ligands are employed or [Pd(dmba-C)(Fmes)(2,2′-bipy)], which contains a chelating 2,2′-bipyridyl and a monodentate C-bonded dmba. Different processes in solution are detected for the complexes containing the bulkier ligands: ligand rotation in the complex with PPh₃; inversion of the bipy ligand in [Pd(dmba-C)(Fmes)(2,2′-bipy)]; and equilibria with residual water in the solutions of [Pd(C-N)(Fmes)(lut)] and [Pd(dmba-C)(Fmes)(2,2′-bipy)].

Full text of DOI:10.1021/om020198r

3536
Organometallics 2002, 21, 3536-3543
Neu tr a l Or ga n om eta llic P a lla d iu m (II) Aqu o Com p lexes
Camino Bartolome´, Pablo Espinet,* Laura Vicente, and Fernando Villafan˜e
Departamento de Quı´mica Inorga´nica, Facultad de Ciencias, Universidad de Valladolid,
47005 Valladolid, Spain
J onathan P. H. Charmant and A. Guy Orpen
School of Chemistry, University of Bristol, Bristol BS8 1TS, U.K.
Received March 11, 2002
The reactions of chlorobridged cyclometalated complexes [Pd(C-N)(µ-Cl)]2 (C-N )
orthometalated N,N-dimethylbenzylamine, dmba; 2-(para-tolyl)pyridine, p-tolpy; azobenzene,
azb; N,N-dimethyl-1-naphthylamine, dmna; and 2-benzylpyridine, bzpy) with Li(Fmes) (Fmes
) 2,4,6-tris(trifluoromethyl)phenyl or nonafluoromesityl) give, after hydrolysis, neutral aquo
complexes [Pd(C-N)(Fmes)(OH2)], where the ipso carbon atoms of the Fmes and the
cyclometalated ligand are coordinated cis, as shown by an X-ray diffraction study of [Pd-
(dmba)(Fmes)(OH2)]. The aquo ligand is readily displaced by other ligands, giving complexes
[Pd(C-N)(Fmes)L] (L ) PPh3, 2,6-lutidine, NH3, CNtBu, CO) when monodentate ligands
are employed or [Pd(dmba-C)(Fmes)(2,2′-bipy)], which contains a chelating 2,2′-bipyridyl
and a monodentate C-bonded dmba. Different processes in solution are detected for the
complexes containing the bulkier ligands: ligand rotation in the complex with PPh3; inversion
of the bipy ligand in [Pd(dmba-C)(Fmes)(2,2′-bipy)]; and equilibria with residual water in
the solutions of [Pd(C-N)(Fmes)(lut)] and [Pd(dmba-C)(Fmes)(2,2′-bipy)].
In tr od u ction
M-Fmes bond, restricted rotation of ancillary ligands,
and a high degree of axial protection in square-planar
complexes.4 The ortho-CF3 groups seem to be involved
in M‚‚‚F bonding interactions [M ) Li, Na, K, Sn(II)]
in many solid state structures,1 but not in the structures
of the fluoromesitylpalladium(II) complexes determined
so far.4 On the other hand, the combination of Fmes and
halide ligands in ligand-deficient conditions for palla-
dium(II) led to an unprecedented self-assembly of a
pyramidal tetrametallic complex with a chloro ligand
in the apex.5
Ligands with high steric demand sometimes stabilize
species that are otherwise inaccessible or difficult to
obtain. The bulky aryl 2,4,6-tris(trifluoromethyl)phenyl
(nonafluoromesityl or Fmes) induces interesting struc-
tural features when coordinated to main group1,2 or
transition metals.3 Some features associated with its
high steric demand are hindrance of rotation around the
* Corresponding author. E-mail: espinet@qi.uva.es.
(1) Edelmann, F. T. Comments Inorg. Chem. 1992, 12, 259.
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1991, 10, 23. (d) Whitmire, K. H.; Labahn, D.; Roesky, H. W.;
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Sheldrick, G. M.; Edelmann, F. T. Organometallics 1992, 11, 192. (g)
Schulter, R. D.; Cowley, A. H.; Atwood, D.A.; J ones, R. A.; Bond, M.
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M.; Markovskii, L.; Schmidt, H.-G. Inorg. Chem. 1996, 35, 6644. (k)
Bender, J . E., IV; Holl, M. M. B.; Kampf, J . W. Organometallics 1997,
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J .; Kampf, J . W. Organometallics 1998, 17, 5166. (m) Klinkhammer,
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37, 124. (n) Bender, J . E., IV; Shusterman, A. J .; Holl, M. M. B.; Kampf,
J . W. Organometallics 1999, 18, 1547. (o) Burford, N.; Macdonald, C.
L. B.; LeBlanc, D. J .; Cameron T. S. Organometallics 2000, 19, 152.
(3) (a) Belay, M.; Edelmann, F. T. J . Organomet. Chem. 1994, 479,
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W.; Elsegood, M. R. J . Chem. Commun. 1996, 2151. (c) Dillon, K. B.;
Gibson, V. C.; Howard, J . A. K.; Redshaw, C.; Sequeira, L.; Yao, J . W.
J . Organomet. Chem 1997, 528, 179. (d) Espinet, P.; Mart´ın-Barrios,
S.; Villafan˜e, F.; J ones, P. G. Organometallics 2000, 19, 290. (e)
Batsanov, A. S.; Dillon, K. B.; Gibson, V. C.; Howard, J . A. K.; Sequeira,
L.; Yao, J . W. J . Organomet. Chem. 2001, 631, 181. (f) Benedikt, G.
M.; Goodall, B. L.; Iyer, S.; McIntosh, L. H., III; Mimna, R.; Rhodes,
L. F.; Day, C. S.; Day, V. W. Organometallics 2001, 20, 2565.
We decided to explore the reactivity of Li(Fmes)
toward complexes [Pd(C-N)(µ-Cl)]2 (C-N ) bidentate
cyclometalated ligand), where, if the chloro ligands were
substituted by Fmes, one coordination position per
metal center would still remain available. It was
interesting to see whether a three-coordinated Pd(II)
complex could be isolated or how the Pd center would
otherwise manage to achieve four-coordination. Two
possibilities foreseen were coordination of F (forming a
favorable five-membered metallacycle) or bridging of the
fluoromesityl ligands,6 since mesityls,7 and other bridg-
ing aryls, including fluoroaryls,8 are well known. It
(4) Bartolome´, C.; Espinet, P.; Villafan˜e, F.; Giesa, S.; Mart´ın, A.;
Orpen, A. G. Organometallics 1996, 15, 2019.
(5) Bartolome´, C.; de Blas, R.; Espinet, P.; Mart´ın-AÄ lvarez, J . M.;
Villafan˜e, F. Angew. Chem., Int. Ed. 2001, 40, 2521.
(6) Voelker, H.; Labahn, D.; Bohnen, F. M.; Herbst-Irmer, R.;
Roesky, H. W.; Stalke, D.; Edelmann, F. T. New J . Chem. 1999, 23,
905.
(7) Meyer, E. M.; Gambarotta, S.; Floriani, C.; Chiesi-Villa, A.;
Guastini, C. Organometallics 1989, 8, 1079.
(8) (a) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Casas, J . M.; Navarro, R.
J . Chem. Soc., Dalton Trans. 1989, 169. (b) Uso´n, R.; Fornie´s, J .;
Toma´s, M.; Casas, J . M.; Cotton, F. A.; Falvello, L. R.; Llusar, R.
Organometallics 1988, 7, 2279. (c) Albe´niz, A. C.; Espinet, P.; Mart´ın-
Ruiz, B. Chem. Eur. J . 2001, 7, 2481.
10.1021/om020198r CCC: $22.00 © 2002 American Chemical Society
Publication on Web 07/25/2002

Neutral Organometallic Pd(II) Aquo Complexes
Organometallics, Vol. 21, No. 17, 2002 3537
Sch em e 1. Syn th esis of Com p lexes 1a
Sch em e 2. Attem p ts a t Syn th esizin g Com p lexes
Sim ila r to 1 w ith Oth er Ar yla tin g Rea gen ts
a
H3 of the five-membered orthometalated ligand is high-
lighted.
subsequent hydrolysis. The results are shown in Scheme
2. The reaction with Li(C6F5) leads in good yield (72%)
to the η1-arene complex cis-[Pd(C6F5)2(C6H5CH2NMe2)],
which had been obtained earlier by displacement of the
THF ligands by dmba from the complex cis-[Pd(C6F5)2-
(THF)2].15 This result can be explained considering that
C6F5 is not as bulky as Fmes. Thus, a second arylation
probably takes place with excess Li(C6F5) to give a cis-
[Pd(C6F5)2(C6H4CH2NMe2)]- intermediate, which then
undergoes protonolysis by attack at the highly nucleo-
philic orthopalladated carbon to give the observed
product [Pd(C6F5)2(C6H5CH2NMe2)]. Performing the
turned out that the availability of water, added for the
hydrolysis of the excess Li(Fmes), provided an additional
ligand and gave rise to neutral aquo complexes, one of
which has been structurally characterized by X-ray
diffraction. The formation of stable complexes with the
hard ligand water on a very soft metal center (a neutral
Pd(II) center with two hydrocarbyl ligands that further
enhance its softness) is remarkable and can be related
to favorable steric factors.
Resu lts a n d Discu ssion
Syn th esis of th e Aqu o Com p lexes. The reactions
of cyclometalated complexes [Pd(C-N)(µ-Cl)]2 with Li-
(Fmes) (Pd/Fmes ) 1:2) were carried in Et2O, at room
temperature or 40 °C, for between 15 and 24 h (see
Experimental Section). Attempts at treating the solu-
tions in the absence of water gave only intractable oils.
However, if a few drops of water were added to hydro-
lyze the excess of Li(Fmes), the neutral aquo complexes
[Pd(C-N)(Fmes)(OH2)] (C-N ) dmba, 1a ; p-tolpy, 1b;
azb, 1c; dmna, 1d ; bzpy, 1e; Scheme 1) could be isolated.
Complexes 1 are somewhat unusual, in that they are
remarkably stable toward reductive coupling, despite
having two cis C-ligands;9 in fact other reactions of
cyclometalated halo-bridged dimers of palladium(II)
with different organolithium reagents reported in the
literature give the coupling product.10 Moreover, com-
plexes 1 feature a hard OH2 ligand coordinated to
palladium(II). This is surprising considering that a
neutral palladium center having two hydrocarbyl ligands
must be very soft. In fact, whereas cationic palladium-
(II) aquo complexes are not uncommon (the metal center
is harder in this case),11 we have not found precedents
in the literature of neutral palladium(II) aquo complexes
other than our proposal of their formation in solu-
tion.12,13
(11) Crystal structures of cationic organometallic palladium aquo
complexes: (a) Deeming, A. J .; Rothwell, I. P.; Hursthouse, M. B.; New,
L. J . Chem. Soc., Dalton Trans. 1978, 1490. (b) Castan, P.; J aud, P.;
Wimmer, S.; Wimmer, F. L. J . Chem. Soc., Dalton Trans. 1991, 1155.
(c) Vicente, J .; Arcas, A.; Borrachero, M. V.; Mol´ıns, E.; Miratvilles, C.
J . Organomet. Chem. 1992, 441, 487. (d) Sheehan, J . P.; Spalding, T.
R.; Ferguson, G.; Gallagher, J . F.; Kaitner, B.; Kennedy, J . D. J . Chem.
Soc., Dalton Trans. 1993, 35. (e) Seligson, A. L.; Trogler, W. C.
Organometallics 1993, 12, 738. (f) Maassarani, F.; Davidson, M. F.;
Wehman-Ooyevaar, I. C. M.; Grove, D. M.; van Koten, M. A.; Smeets,
W. J . J .; Spek, A. L.; van Koten, G. Inorg. Chim. Acta 1995, 235, 327.
(g) Vicente, J .; Arcas, A.; Bautista, D. Organometallics 1997, 16, 2127.
(h) Vicente, J .; Arcas, A.; Blasco, M. A.; Lozano, J .; Ramı´rez de Arellano,
M. C. Organometallics 1998, 17, 5374. (i) Ruiz. J .; Florenciano, F.;
Vicente, C.; Ram´ırez de Arellano, M. C.; Lo´pez, G. Inorg. Chem.
Commun. 2000, 3, 73. (j) Barco, I. C.; Falvello, L. R.; Ferna´ndez, S.;
Navarro, R.; Urriolabeitia, E. P. J . Chem. Soc., Dalton Trans. 1998,
1699. (k) Ma, J .-F.; Kojima, Y.; Yamamoto, Y. J . Organomet. Chem.
2000, 616, 149. Other cationic palladium organometallic aquo com-
plexes reported but not characterized by diffraction methods: (l)
Ryabov, A. D.; Kazankov, G. M.; Yatsimirsky, A. K.; Kuz’mina, L. G.;
Burtseva, O. Y.; Dvortsova, N. V.; Polyakov, V. A. Inorg. Chem. 1992,
31, 3083. Crystal structures of cationic coordination palladium aquo
complexes: (m) Leoni, P.; Sommovigo, M.; Pasquali, M.; Midollini, S.;
Braga, D.; Sabatino, P. Organometallics 1991, 10, 1038. (n) Stang, P.
J .; Cao, D. H.; Poulter, G. T.; Arif, A. T. Organometallics 1995, 14,
1110. Other cationic palladium coordination aquo complexes reported
but not characterized by diffraction methods: (o) Fuss, M.; Siehl, H.
U.; Olenyuk, B.; Stang, P. J . Organometallics 1999, 18, 758.
(12) A reviewer has drawn our attention to the fact that the
compound in ref 11b, [Pd(L)(ONO2)(OH2)]ClO4‚HO2,
L being the
orthometalated N-methyl-2,2′-dipyridinium cation, should be consid-
ered an essentially neutral Pd aquo complex, since the positive charge
must be associated to the methylated nitrogen. Note that the second
anionic ligand (nitrate) is a very poor hard donor, which renders the
Pd center much harder than ours. Also the positive nitrogen in the
heterocycle will still be more electron attracting than a neutral carbon
atom and will make the protonated hydrocarbyl harder than a phenyl.
Whether neutral or cationic, this must be a rather hard Pd center for
which coordination of a hard ligand is not unnatural. Our case is
different and remarkable because of the softness of the center where
water coordinates.
To assess more accurately the role of Fmes in produc-
ing these unusual complexes, parallel reactions were
carried out with C6F5 (a ligand with similar electron-
donating properties but smaller steric volume) and
mesityl (with similar steric volume but more basic).14
The reactions with [Pd(dmba)(µ-Cl)]2 were carried out
under the same conditions as for Li(Fmes): a Pd/C6F5
ratio of 1:2, stirred for 24 h at room temperature, and
(13) Espinet, P.; Mart´ınez-Ilarduya, J . M.; Pe´rez-Briso, C.; Casado,
A. L.; Alonso, M. A. J . Organomet. Chem. 1998, 551, 9.
(14) Although the covalent radii of fluorine (58 pm) and hydrogen
(30 pm) differ, their van der Waals radii are similar: 135 vs 120 pm,
respectively: Emsley, J . The Elements, 2nd ed.; Oxford University
Press: Oxford, 1991.
(9) Brown, J . M.; Cooley, N. A. Chem. Rev. 1988, 88, 1031.
(10) (a) Muharashi, S. I.; Tamba, Y.; Yamamura, M.; Moritani, I.
Tetrahedron Lett. 1974, 3749. (b) Muharashi, S. I.; Tamba, Y.;
Yamamura, M.; Yoshimura, N. J . Org. Chem. 1978, 43, 4099.
(15) Falvello, L. R.; Fornie´s, J .; Navarro, R.; Sicilia, V.; Toma´s, M.
Angew. Chem., Int. Ed. Engl. 1990, 29, 891.

3538 Organometallics, Vol. 21, No. 17, 2002
Bartolome´ et al.
Ta ble 1. IR a n d 1H NMR Da ta of Coor d in a ted OH2
in Com p lexes 1
Sch em e 3. Mech a n ism s P r op osed for th e Boa t
In ver sion Obser ved for 1e
aquo
complex
δ/ppm
(25 °C)
δ/ppm
δ/ppm
ν/cm-1
(solid)
(25 °C)a
(-60 °C)a
1a
1b
1c
1d
1e
1.89
2.10
1.95
2.09
1.70
1.97
2.40
2.14
2.17
1.82
2.21
2.80
2.61
2.40
2.48
3607m, 3529m
3609w, 3542m
3647m, 3606m
3622w, 3544m
3637m, 3518m
a
Recorded in dry CDCl3.
reaction with a Pd/C6F5 ratio of 1:1 gives a mixture of
cis-[Pd(C6F5)2(C6H5CH2NMe2)] and unidentified minor
species that display absorptions in the O-H stretching
region. When the parent chloro complex and BrMgMes
were subjected to the aforementioned reaction condi-
tions, extensive decomposition took place.
Ch a r a cter iza tion of th e Neu tr a l Aqu o Com -
p lexes. The IR spectra of complexes 1 show two
absorptions in the O-H stretching region.16 The hydro-
gens of the coordinated water molecule appear in the
range 1.7-2.1 ppm when the spectra are recorded in
CDCl3 at room temperature. A slight downfield shift is
observed in dry CDCl3 (1.8-2.4 ppm range), and even
more downfield values are obtained in dry CDCl3 at -60
°C (Table 1). These variations must be a result of fast
equilibrium between coordinated water and water in the
solvent, the average chemical shift changing with the
proportion of free water. The traces of free water are
almost completely removed when using dry CDCl3 and
should freeze out at -60 °C. Our chemical shift values
are unusually low compared to most values reported in
the literature,17 which appear in the range 1.8-5 ppm
for cationic complexes11a,f-k,m,n and 4.5-7 ppm for
neutral complexes.13 We suspect that most values
reported in the literature come from recordings at room
temperature in wet CDCl3. Thus, extreme care should
be exercised when comparing chemical shifts of aquo
complexes.
The signals of the cyclometalated ligand are very
similar to those of the parent chloro-bridged dimer,
except for H3 (see Scheme 1), which is clearly shifted
upfield in 1a -d . This supports the structure depicted
in Scheme 1, where the carbon donor atoms of the Fmes
and cyclometalated ligands are cis, and the aryl Fmes
ring produces anisotropic shielding of H3. Moreover, this
arrangement places the two softer donor atoms mutu-
ally cis, as expected for Pd(II).18
spectrum at room temperature and decoalesce into two
doublets at -60 °C. At room temperature the fluorine
atoms of the ortho-CF3 groups of 1e appear as a very
broad signal (v1/2 ) ca. 20 Hz), whereas they are fine
singlets for 1a -d . On cooling to -60 °C, this broad
signal splits into two singlets of equal intensity, indicat-
ing that both ortho-CF3 groups are nonequivalent when
the dynamic process is frozen. This is attributed to a
slow inversion of the boat-shaped six-membered met-
allacycle (Scheme 3), which has been described for other
complexes containing orthometalated 2-benzylpyri-
dine.19 Direct boat-to-boat inversion of bzpy ligand in
the very crowded 1e complex (Scheme 3, center) looks
very unlikely. The most likely mechanism is decoordi-
nation and recoordination of the pyridyl group (Scheme
3, upper), since dissociation from an electron-rich bis-
(hydrocarbyl)palladium(II) center should be easily ac-
cessible. Dissociation of OH2 would require either boat
inversion or Fmes rotation in a three-coordinate inter-
mediate, and both are sterically hindered. Moreover, the
Fmes rotation does not explain the equivalence of the
two methylene hydrogens observed in the room-tem-
perature spectrum of 1e.
Str u ctu r a l Ch a r a cter iza tion of [P d (d m ba )(F m e-
s)(OH2)], 1a . The structure of the aquo complexes was
further supported by the X-ray diffraction study of [Pd-
(dmba)(Fmes)(OH2)], 1a . The molecule is shown in
Figure 1. Relevant distances and angles are collected
in Table 2. The molecule shows an approximately
square-planar palladium atom coordinated by an ortho-
metalated dimethylbenzylamine with its carbon donor
atom cis to the fluoromesityl ligand and a molecule of
water coordinated cis to the nitrogen atom. The coor-
dination angles at palladium are not far from the
square-planar ideal, although the bite angle of the
chelate is noticeably smaller, as expected. The trans
angles differ slightly from 180° [C(1)-Pd-O(20)
The six-membered metallacycle 1e differs from the
others. The loss of planarity on the cyclometalated
ligand results in hydrogen H3 of the orthometalated
ligand not being subjected to anisotropic shielding by
the Fmes ligand and appears in the normal range for
palladated aryls. The methylene hydrogens of the cy-
clometalated ligand give rise to a broad signal in the
(16) Kubas, G. J .; Burns, C. J .; Khalsa, G. R. K.; Van Der Sluys, L.
S.; Kiss, G.; Hoff, C. D. Organometallics 1992, 12, 3390, and references
therein.
(17) There is only one precedent where the signal corresponding to
the hydrogens of the OH2 ligand appears at 1.8 ppm (ref 11c).
(18) The well-known destabilizing effect of two mutually trans soft
ligands attached to a soft metal center has been named “antisymbiotic
effect” (Pearson, R. G. Inorg. Chem. 1973, 12, 712). More recently the
term “transphobia” has been coined for pairs of ligands (see ref 11g
and: Vicente, J .; Abad, J . A.; Frankland, A. D.; Ram´ırez de Arellano,
M. C. Chem. Eur. J . 1999, 5, 3067). For trans influence of common
ligands see: Hartley, F. R. Chem. Soc. Rev. 1973, 2, 163.
(19) Hiraki, K.; Fuchita, Y.; Takechi, K. Inorg. Chem. 1981, 20, 4316.

Neutral Organometallic Pd(II) Aquo Complexes
Organometallics, Vol. 21, No. 17, 2002 3539
to the pseudoplane defined by the metal and the donor
atoms. The Pd‚‚‚F3C-ortho distances found in 1a (3.089
Å, the shortest; 3.463 Å, the largest) are slightly longer
than those found in bisarylated “Pd(Fmes)2” complexes,
confirming that these are nonbonding contacts, as
discussed elsewhere.4
The two hydrogen atoms of the OH2 ligand were
located in a difference Fourier map and refined. To
correct the systematic shortening of F-H bonds mea-
sured by X-ray diffraction, normalized H atom positions
were used. An O-H distance of 0.967 Å was imposed, a
value that has been observed in alcohols by neutron
diffraction.23 Applying this, four O-H‚‚‚F contacts have
been detected, two of them intramolecular and the other
two intermolecular (Figure 1). The distances and angles
of these contacts are listed in Table 3. The H(20B)-
F(13G) distance is 2.200 Å. Only few cases where these
contacts involve H‚‚‚F distances shorter than 2.3 Å have
been described.24
Rea ctivity of th e Aqu o Com p lexes. The substitu-
tion of 1 with different ligands has been studied
(Scheme 4). The aquo ligand is hard and should be easily
removed from the coordination sphere of the soft pal-
ladium(II) center. The high degree of axial protection
to a nucleophilic attack in the bis-arylated [Pd(C-N)-
(Fmes)(OH2)] should favor dissociative mechanisms of
ligand substitution.25
Ligands with different steric and electronic demands
were tested. Bulky donors with different steric features
were chosen: PPh3, of conical shape; 2,6-lutidine (lut),
highly sterically demanding in the axial positions (like
Fmes); and the chelating bidentate ligand 2,2′-bipyridyl
(bipy).
F igu r e 1. Molecular structure of 1a showing the atom-
numbering scheme. Intermolecular and intramolecular
hydrogen bonds observed in 1a . The ellipsoids are drawn
at 30%.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 1a
Olefins and acetylenes do not react with 1. tBuNC and
CO replace the water ligand to give 2a and 3a , which
do not undergo insertion: insertion into the Pd-Fmes
bond does not take place easily, while insertion into the
trans-Pd-C bond is geometrically inaccessible. Am-
monia replaces water to give 4a . Neither 1a nor 4a could
be deprotonated with NBu4OH or N,N,N′,N′-tetra-
methyl-1,8-naphthalenediamine (“proton sponge”).
Pd1-C(1)
1.978(2)
2.006(3)
2.149(2)
2.220(2)
C(1)-Pd(1)-N(8)
C(1)-Pd(1)-C(11)
C(11)-Pd(1)-O(20)
N(8)-Pd(1)-O(20)
C(1)-Pd(1)-O(20)
C(11)-Pd(1)-N(8)
C(18)-C(11)-C(12)
83.35(10)
92.34(10)
91.57(9)
Pd(1)-C(11)
Pd(1)-N(8)
Pd(1)-O(20)
92.81(9)
176.07(10)
171.83(9)
114.7(2)
176.07(10)° and C(11)-Pd-N(8) 171.83(9)°], whereas
the sum of cis angles is almost exactly 360°. The C(18)-
C(11)-C(12) angle at the ipso carbon is significantly less
than 120° [114.7(2)°] as a result of the electronic effects
of the electropositive metal and electronegative CF3
substituents at these positions.20 The Pd-C(11) distance
[2.006(3) Å] is slightly shorter than other Pd-Fmes
distances found in bisarylated complexes [from
2.023(3) to 2.114(5) Å].4 The distances and angles of the
orthometalated dmba are essentially similar to those
found in other palladium(II) complexes containing this
ligand.11a,f,j,k,21 The Pd-OH2 distance [2.220(2) Å] is in
the range found in cationic Pd(II) aquo complexes, from
2.106(4) to 2.301(6) Å.11a-k,m,n The same effect has been
observed in platinum(II) aquo complexes, where neutral
and cationic complexes present similar Pt-O dis-
tances.22 The fluoromesityl lies virtually perpendicular
The complexes [Pd(C-N)(Fmes)(PPh3)] (C-N ) dmba,
5a , p-tolpy, 5b) show a septuplet in the 31P{1H} NMR
spectra, and the ortho-CF3 gives rise to a doublet in their
19F NMR spectra, as expected. These spectra remain
invariant from -60 °C to room temperature. H3 appears
shielded as in the parent compounds, suggesting that
the substitution has retained the original geometry. The
aromatic protons of the phosphines give broad signals
1
in the H NMR spectra at room temperature, while the
signals for the hydrogens of the Fmes group (slightly
shielded compared with the rest of complexes herein
(22) For some structures of Pt(II) aquo complexes see: ionic: (a)
Britten, J . F.; Lippert, B.; Lock, C. J . L.; Pilon, P. Inorg. Chem. 1982,
21, 1936. (b) Rauter, H.; Hillgeris, E. C.; Erxleben, A.; Lippert, B. J .
Am. Chem. Soc. 1994, 116, 616. (c) Meinema, H. A.; Verbeek, F.;
Marsman, J . W.; Bulten, E. J .; Dabrowiak, J . C.; Krishnan, B. S.; Spek,
A. L. Inorg. Chim. Acta 1986, 114, 127. (d) Rochon, F. D.; Melanson,
R. Inorg. Chem. 1987, 26, 989; neutral: (e) Intini, F. P.; Lanfranchi,
M.; Natile, G.; Pacifico, C.; Tiripicchio, A. Inorg. Chem. 1996, 35, 1715.
(23) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G.; Taylor, R. J . Chem. Soc., Perkin Trans. 2 1987, S1.
(20) (a) Domenicano, A.; Vaciago, A.; Coulson, C. A. Acta Crystal-
logr., Sect. B 1975, 31, 221. (b) Domenicano, A.; Mazzeo, P.; Vaciago,
A. Tetrahedron Lett. 1976, 1029. (c) Norrestam, R.; Schepper, L. Acta
Chem. Scand., Ser. A 1981, 35, 91. (d) Domenicano, A.; Murray-Rust,
P.; Vaciago, A. Acta Crystallogr., Sect. B 1983, 39, 457.
(21) (a) Braunstein, P.; Matt, D.; Dusausoy, Y.; Fischer, J .; Mitschler,
A.; Ricard, L. J . Am. Chem. Soc. 1981, 103, 5115. (b) Falvello, L. R.;
Ferna´ndez, S.; Navarro, R.; Urriolabeitia, E. P. Inorg. Chem. 1996,
35, 3064.
(24) Dunitz, J . D.; Taylor, R. Chem. Eur. J . 1997, 3, 89.
(25) (a) Bartolome´, C.; Espinet, P.; Mart´ın-AÄ lvarez, J . M.; Villafan˜e,
F. Manuscript in preparation. (b) Romeo, R. Comments Inorg. Chem.
1990, 11, 21. (b) Minniti, D. Inorg. Chem. 1994, 33, 2631. (c) Casado,
A. L.; Casares, J . A.; Espinet, P. Inorg. Chem. 1998, 37, 4154.

3540 Organometallics, Vol. 21, No. 17, 2002
Bartolome´ et al.
Ta ble 3. Bon d Len gth s (Å) a n d An gles (d eg) for In tr a - a n d In ter m olecu la r Hyd r ogen Bon d s Obser ved in 1a
H(20A)-F(13B)
H(20B)-F(19A)
H(20A)-F(16E)
H(20B)-F(13G)
2.358
2.811
2.554
2.200
F(13B)-H(20A)-O(20)
F(19A)-H(20B)-O(20)
F(16E)-H(20A)-O(20)
F(13G)-H(20B)-O(20)
132.0
118.7
109.3
138.5
intramolecular
intramolecular
intermolecular
intermolecular
Sch em e 4. Su bstitu tion Rea ction s in
Ch a r t 1. Low -Tem p er a tu r e P r efer r ed
Ar r a n gem en t in Com p lexes 5a ,b
[P d (C-N)(F m es)(OH2)]a
Sch em e 5. Tw o P ossible Mech a n ism s for th e
In ver sion of th e Bip y Liga n d in 7a
a
C-N ) dmba, L ) tBuNC, 2a ; CO, 3a ; NH3, 4a ;PPh3, 5a ;
2,6-lut, 6a ; C-N ) dmba, N-N ) bipy, 7a . C-N ) p-tolpy, L
) PPh3, 5b.
described: ca. 7.5 in 5 vs ca. 7.9) and the orthometalated
ligands are sharp. On cooling the solutions of 5a ,b to
-60 °C, the phosphine phenyls become nonequivalent,
where one phenyl group is highly shielded, with the
other two presenting regular chemical shifts. A similar
behavior has been previously observed for complexes
with Fmes and PPh3 coordinated cis and is due to
restricted rotation of the Pd-P bond, which is frozen
at low temperature, as shown in Chart 1. In that
arrangement the Fmes ligand and one of the phenyl
groups of the phosphine exert mutual anisotropic shield-
ing.4 The activation barrier for the rotation of the PPh3
is lower in 5a than in 5b, suggesting that it takes place
in a three-coordinate intermediate. This agrees with the
expectation that decoordination of the amine nitrogen
in dmba should be easier than for the pyridinic nitrogen
in p-tolpy.
The ligand 2,6-lutidine is sterically demanding in the
same axial positions as Fmes. However, the reaction of
1a with equimolar amounts of 2,6-lutidine does produce
[Pd(dmba)(Fmes)(lut)], 6a , which is isolated as a white
solid. Note that although the axial crowding should be
important, it is somewhat less than that in complexes
cis-[Pd(Fmes)2L2].4 The IR spectrum and elemental
microanalysis support the stoichiometry for the solid
obtained, whereas in the NMR spectra at room temper-
ature the signals are very broad, due to the presence of
traces of water in CDCl3 and the existence of a slow
equilibrium between 6a and 1a (eq 1). At -60 °C, the
signals of the species present in the equilibrium are
resolved and those of 6a can be assigned. The equilib-
rium constant at -30 °C in CDCl3 was measured as Ke
) 3.1 ( 0.7, using known water concentrations.26
equilibrium between 7a and 1a (i in Scheme 5) due to
the presence of traces of water in the solvent CDCl3.
Below -10 °C the signals of 7a (major) and 1a (very
minor) can be resolved in the 19F NMR spectrum. At
-20 °C signals of 7a , 1a , and free bipy can be observed
[Pd(dmba)(Fmes)(L)] + H2O h
[Pd(dmba)(Fmes)(OH2)] + L (1)
1
in the H NMR spectrum. The equilibrium constant of
this process, determined for 7a using CDCl3 solutions
of known water concentration, is temperature depend-
ent, as shown in Table 4.
Finally, the reaction of 1a with 2,2-bipyridyl (1:1)
leads to [Pd(dmba-C)(Fmes)(bipy)], 7a , where the dmba
ligand is monodentate. This is supported by the chemi-
cal shift of H3, which is no longer shielded by the Fmes
ring, and by the chemical shift of the bipy signals, which
support coordination of both pyridyl nitrogens. Two
dynamic processes are observed in 7a . The first is an
A second dynamic process is still operative at lower
temperatures. On further cooling the fluorine atoms of
(26) CDCl3 solutions with different concentrations of water were
titrated by NMR by integration of the water signal versus ferrocene
added as reference.

Neutral Organometallic Pd(II) Aquo Complexes
Organometallics, Vol. 21, No. 17, 2002 3541
[Pd(dmna)(µ-Cl)]2,28 and [Pd(bzpy)(µ-Cl)]2 were prepared by
10
Ta ble 4. Equ ilibr iu m Con sta n ts for 7a a n d 1a
the general method currently used in our group,32 involving
synthesis of the corresponding acetato-bridged complexes33 and
subsequent treatment with a methanolic solution of hydrogen
chloride. 1,3,5-C6H3(CF3)3 (FmesH) was purchased from Fluo-
rochem and used as received. Li(Fmes) was prepared as
described in the literature34 and used immediately in situ
without further purification.
Infrared spectra were recorded in Perkin-Elmer 883 or
1720X equipment, as Nujol mulls between polystyrene plates,
from 4000 to 200 cm-1. NMR spectra were recorded on Bruker
AC-300 or ARX-300 instruments, in CDCl3 at room tempera-
ture unless otherwise stated. NMR spectra are referenced to
TMS, CFCl3, or 85% aqueous H3PO4, and coupling constants
are measured in Hz. Elemental analyses were performed on
a Perkin-Elmer 2400B microanalyzer.
Gen er a l Met h od for t h e P r ep a r a t ion of t h e Aq u o
Com p lexes. The orthometalated palladium(II) chloro-bridged
dimer (0.5 mmol) was added to a freshly prepared solution of
Li(Fmes) (2.0 mmol; [Pd(C-N)(µ-Cl)]2/Li(Fmes) ) 1:4) in Et2O
(20 mL). After stirring the mixture for 24 h at the temperature
indicated, two drops of water were added to hydrolyze the
excess of organolithium reagent. The volatiles were removed
in a vacuum, and the dark residue was extracted with CH2-
Cl2 (ca. 50 mL) and filtered on dry Celite. n-Hexane (ca. 20
mL) was added to the filtrate, which was concentrated and
cooled to -20 °C. The microcrystalline solid obtained was
decanted, washed with n-hexane (3 × 5 mL), and dried in a
vacuum. The reaction details (temperature and yield), color,
and spectroscopic data of the products obtained are given
below. The aquo complexes were analized by ATG. Above 110
°C the compounds started to lose water slowly, but before the
loss was complete the compounds started to decompose gradu-
ally. For this reason no well-defined melting or decomposition
temperatures can be given.
temperature/°C
Keq
-30
-25
-20
(24 ( 5) × 10-3
(25 ( 6) × 10-3
(35 ( 7) × 10-3
the ortho-CF3 of 7a broaden. Below -55 °C this broad
signal splits into two singlets, indicating that both ortho-
CF3 groups are nonequivalent. In the H spectrum, not
1
only does the singlet of the methylene hydrogens become
an AB system at low temperature, but also the signals
of the coordinated bipy split, which means that the two
halves of the bipyridine are nonequivalent. A dissocia-
tive mechanism (ii in Scheme 5) involving decoordina-
tion of one Py group of the bipy ligand, followed by
topomerization in the three-coordinate intermediate and
recoordination, could explain the equivalences observed
at -20 °C. Alternatively, inversion of the bipy ligand
through a five-coordinate intermediate A looks less
likely because of the high degree of steric hindrance and
the inappropriate bite angle of bipy in the five-
coordinate transition state and also because of the poor
electrophilicity of PdR2L2 complexes.25b
Both methyls of the amino group are still equivalent
at -100 °C. This can be explained assuming that the
inversion of the nitrogen is fast on the NMR time scale.
This equivalence further proves that the complex does
not possess a monodentate bipy and a chelating dmba,
as this should produce inequivalence for these methyls.
Con clu sion s
The reaction of several orthometalated chloro-bridged
palladium(II) dimers with Li(Fmes) followed by hy-
drolysis affords neutral palladium(II) aquo complexes.
The electronic and steric features of the Fmes ligand
seem to play a decisive role in their stabilization, as
attempts at extending this behavior to alternative aryls
have failed. The aquo ligand can be readily substituted
for a variety of ligands. Those that are sterically
demanding allow the observation of dynamic processes
in solution due to either hindered rotation of any of the
ligands present or equilibrium with the water complex,
which is formed even from traces of water. It is
noteworthy that the hard ligand water can compete with
other much better but bulkier ligands, due to the fact
that water relieves structural crowding. The remarkable
unusual stability of the CO and NH3 complexes must
also benefit from the small steric requirement of these
ligands.
[P d (d m ba )(F m es)(OH2)], 1a . Reaction at room tempera-
ture, 88% yield, pale brown. 19F NMR: δ -60.00 (s, ortho-CF3,
6F), -62.90 (s, para-CF3, 3F). 1H NMR: δ 7.88 (s, C6H2(CF3)3,
2H), 6.86 (m, C6H4, 2H), 6.59 (td, J 7.0 and 2.0, C6H4, 1H),
5.85 (d, J 7.5, H3, C6H4, 1H), 3.82 (s, CH2, 2H), 2.69 (s, NCH3,
6H), 1.97 (s, H2O, 2H). IR: 3607 m, 3529 m, 1616 s, 1580 s,
1563 s, 1403 m, 1283 vs, 1127 vs, 1022 s, 996 s, 976 m, 918 s,
868 m, 852 s, 835 s, 684 s, 564 w, 511 w, 491 w, 467 m, 438 m.
Anal. Calcd for C18H16F9NOPd: C, 40.06; H, 2.99; N, 2.60.
Found: C, 40.18; H, 2.97; N, 2.88.
[P d (p-tolp y)(F m es)(OH2)], 1b. Reaction at 40 °C, 50%
yield, pale brown. 19F NMR: δ -59.71 (br, ortho-CF3, 6F),
-62.79 (s, para-CF3, 3F). 1H NMR: δ 8.38 (br, NC5H4, 1H),
7.95 (s, C6H2(CF3)3, 2H), 7.72 (m, NC5H4, 1H), 7.65 (d, J 8.0,
NC5H4, 1H), 7.33 (d, J 8.0, CH3C6H3, 1H), 7.11 (br, NC5H4,
1H), 6.79 (d, J 7.5, CH3C6H3, 1H), 5.80 (s, CH3C6H3, H3, 1H),
2.41 (br, H2O, 2H), 2.03 (s, CH3C6H3, 3H). IR: 3607 w, 3542
m, 1620 s, 1601 s, 1573 m, 1299 s, 1279 vs, 1189 vs, 1181 vs,
1146 vs, 1130 vs, 1118 vs, 1081 s, 1029 m, 911 s, 852 m, 833
m, 776 s, 693 m, 684 m, 667 w, 466 w, 418 w. Anal. Calcd for
C
21H14F9NOPd: C, 43.96; H, 2.46; N, 2.44. Found: C, 44.11;
Exp er im en ta l Section
H, 2.60; N, 2.60.
[P d (a zb)(F m es)(OH2)], 1c. Reaction at 40 °C, 72% yield,
deep red. 19F NMR: δ -60.02 (s, ortho-CF3, 6F), -62.97 (s,
para-CF3, 3F). 1H NMR: δ 7.97 (s, C6H2(CF3)3, 2H), 7.95
(partially hidden dd, J unknown and 1.5, C6H4, 1H), 7.78 (dd,
J 8.0 and 1.5, C6H5, 2H), 7.57 (m, C6H5, 3H), 7.14 (td, J 7.5
and 1, C6H4, 1H), 6.92 (td, J 7.5 and 1.0, C6H4, 1H), 6.06 (dd,
J 7.5 and 1.0, C6H4, H3, 1H), 2.14 (s, H2O, 2H). IR: 3647 m,
Gen er a l Com m en ts. All reactions were carried out under
nitrogen atmosphere. The solvents were purified according to
standard procedures.27 Diethyl ether was distilled under
nitrogen from sodium/benzophenone ketyl prior to use. [Pd-
28
29
(dmba)(µ-Cl)]2 and Pd3(OAc)6 were prepared according to
literature procedures. [Pd(p-tolpy)(µ-Cl)]2,30 [Pd(azb)(µ-Cl)]2,31
(27) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: Oxford, 1988.
(28) Cope, A. C.; Friedrich, E. C. J . Am. Chem. Soc. 1968, 90, 909.
(29) Stephenson, T. A.; Morehouse, S. M.; Powell, A. R.; Heffer, J .
P.; Wilkinson, G. J . Chem. Soc. 1965, 3632.
(30) Gutie´rrez, M. A.; Newkome, G. R.; Selbin, J . J . Organomet.
Chem. 1980, 202, 341.
(32) Buey, J .; Espinet, P. J . Organomet. Chem. 1996, 507, 137. Based
on the method described in: Onoue, H.; Moritani, I. J . Organomet.
Chem. 1972, 43, 431.
(33) Thompson, J . M.; Heck, R. F. J . Org. Chem. 1975, 40, 2667.
(34) (a) Carr, G. E.; Chambers, R. D.; Holmes, T. F.; Parker, D. G.
J . Org. Chem. 1987, 325, 13. (b) Scholz, M.; Roesky, H. W.; Stalke, D.;
Keller, K.; Edelmann, F. T. J . Organomet. Chem. 1989, 366, 73.
(31) Cope, A. C.; Siekman, R. W. J . Am. Chem. Soc. 1965, 87, 3272.

3542 Organometallics, Vol. 21, No. 17, 2002
Bartolome´ et al.
3606 w, 1618 m, 1567 w, 1553 w, 1299 vw, 1278 vw, 1239 m,
1190 vw, 1121 w, 1081 m, 1022 m, 910 m, 851 w, 834 m, 769
s, 684 m, 666 w, 598 w, 439 w. Anal. Calcd for C21H13F9N2-
OPd: C, 42.99; H, 2.23; N, 4.77. Found: C, 43.02; H, 2.33; N,
4.74.
[P d (d m n a )(F m es)(OH2)], 1d . Reaction at room tempera-
ture, 32% yield, dark yellow. 19F NMR: δ -59.72 (s, ortho-
CF3, 6F), -62.84 (s, para-CF3, 3F). 1H NMR: δ 7.94 (s,
C6H2(CF3)3, 2H), 7.61 (m, C10H6, 1H), 7.39 (m, C10H6, 3H), 6.92
(t, J 7.5, C10H6, 1H), 5.89 (d, J 7.0, C10H6, H3, 1H), 3.24 (s,
CH3, 6H), 2.17 (s, H2O, 2H). IR: 3622 w, 3548 m, 1619 m, 1560
m, 1357 s, 1216 w, 1190 s, 1111 s, 1082 s, 1032 w, 1019 w,
937 w, 915 m, 861 w, 852 w, 834 w, 818 w, 781 m, 772 m, 755
w, 694 m, 684 m, 636 m, 565 w, 468 m, 440 m, 396 w. Anal.
Calcd for C21H16F9NOPd: C, 43.81; H, 2.80; N, 2.78. Found:
C, 44.07; H, 2.93; N, 2.75.
Anal. Calcd for C19H14F9NOPd: C, 41.51; H, 2.57; N, 2.55.
Found: C, 41.58; H, 2.78; N, 2.52.
[P d (d m b a )(F m es)(NH 3)], 4a . Ammonia was bubbled
through a solution of 1a (0.162 g, 0.3 mmol) in toluene (15
mL), while the solution was stirred at room temperature for
15 min. The solvent was removed in a vacuum, and the oily
residue was extracted with CH2Cl2 (30 mL) and filtered on
dry Celite. n-Hexane (ca. 30 mL) was added to the filtrate,
which was concentrated and cooled to -20 °C. The micro-
crystalline solid obtained was decanted, washed with hexane
(3 × 5 mL), and dried in a vacuum, yielding 0.117 g (72%) of
4a as a white microcrystalline solid. 19F NMR: δ -60.65 (s,
1
ortho-CF3, 6F), -62.79 (s, para-CF3, 3F). H NMR: δ 7.86 (s,
C6H2(CF3)3, 2H), 6.92 (d, J 6.0, C6H4 of dmba, 1H), 6.84 (td, J
7.5 and 1.0, C6H4 of dmba, 1H), 6.63 (td, J 7.5 and 1.0, C6H4
of dmba, 1H), 5.90 (dd, J 7.5 and 1.0, H3 of dmba, 1H), 3.87 (s,
CH2 of dmba, 2H), 2.67 (s, CH3 of dmba, 6H), 1.39 (br, NH3,
3H). IR: 3383 w, 3294 m, 1617 s, 1580 m, 1563 m, 1402 w,
1298 vs, 1282 vs, 1233 m, 1213 m, 1181 s, 1132 vs, 1079 m,
1025 m, 996 m, 974 vw, 909 m, 868 w, 852 m, 832 m, 746 s,
694 m, 684 m, 666 w, 622 w, 579 w, 508 w, 470 w, 438 w.
Anal. Calcd for C18H17F9N2Pd: C, 40.13; H, 3.18; N, 5.20.
Found: C, 40.32; H, 3.26; N, 4.98.
[P d (bzp y)(F m es)(OH2)], 1e. Reaction at 40 °C, 17% yield,
pale brown. 19F NMR: δ -59.97 (br, ortho-CF3, 6F), -62.96
(s, para-CF3, 3F). 19F NMR (-60 °C): δ -59.82 (s, ortho-CF3,
3F), -60.4 (s, ortho-CF3, 3F), -62.46 (s, para-CF3, 3F). 1H
NMR: δ 8.61 (d, J 5.0, C6H4N, 1H), 7.86 (s, C6H2(CF3)3, 2H),
7.72 (td, J 6.0 and 1.5, C6H4N, 1H), 7.47 (d, J 7.5, C6H4, 1H),
7.22 (t, J 6.5, C6H4N, 1H), 6.97 (d, J 7.0, C6H4, 1H), 6.80 (td,
J 7.0 and 1.5, C6H4, 1H), 6.60 (td, J 7.0 and 1.5, C6H4, 1H),
6,50 (dd, J 6.5 and 1.0, C6H4N, 1H), 4.40 (br, CH2, 2H), 1.82
[P d (d m ba )(F m es)(P P h 3)], 5a . PPh3 (0.052 g, 0.2 mmol)
was added to a solution of 1a (0.108 g, 0.2 mmol) in toluene
(10 mL). The solution was stirred at room temperature for 16
h, during which time a white solid had precipitated. The solid
was filtered off, washed with n-hexane (3 × 5 mL), and
recrystallized from CH2Cl2/hexane, yielding 0.095 g (60%) of
5a as white crystals. 19F NMR: δ -59.27 (d, J PF 4.0, ortho-
CF3, 6F), -62.79 (s, para-CF3, 3F). 31P{1H} NMR: δ 16.7 (sept).
1H NMR: δ 7.53 (s, C6H2(CF3)3, 2H), 7.3 (br, C6H5, 15H), 7.02
(dt, J 7.0 and 1.0, C6H4CH2NMe2, 1H), 6.91 (t, J 7.0, C6H4-
CH2NMe2, 1H), 6.69 (tt, J 7.0 and 2.0, C6H4CH2NMe2, 1H),
6.01 (m, H3, C6H4CH2NMe2, 1H), 3.97 (s, C6H4CH2NMe2, 2H),
2.29 (s, CH3, 6H). 1H NMR (-60 °C): δ 7.69 (t, J 8.0, C6H5,
4H), 7.52 (m, 2H of C6H2(CF3)3 and 6H of C6H5), 6.99 (m, 2H
of C6H4CH2NMe2 and 1H of C6H5), 6.76 (m, 1H of C6H4CH2-
NMe2 and 2H of C6H5), 6.44 (t, J 8.0, C6H5, 2H), 6.01 (t, J 3.0,
H3, dmba, 1H), 4.00 (s, C6H4CH2NMe2, 2H), 2.28 (s, CH3, 6H).
IR: 1619 m, 1582 m, 1566 w, 1404 w, 1302 s, 1279 m, 1186 s,
1156 w, 1141 w, 1128 w, 1097 w, 1078 m, 1021 m, 974 w, 915
s, 865 w, 847 m, 830 m, 790 w, 752 w, 699 w, 684 m, 619 w,
561 m, 527 m, 511 w, 494 w, 466 w, 449 w, 435 s, 396 w, 310
m. Anal. Calcd for C36H29F9NPPd: C, 55.15; H, 3.73; N, 1.79.
Found: C, 55.07; H, 3.82; N, 1.80.
1
(s, H2O, 2H). H NMR (-60 °C): δ 8.63 (d, J 5.0, C6H4N, 1H),
7.98 (s, C6H2(CF3)3, 1H), 7.75 (t, J 7.5, C6H4N, 1H), 7.70 (s,
C6H2(CF3)3, 1H), 7.50 (d, J 8.0, C6H4, 1H), 7.26 (hidden by the
CHCl3 signal, C6H4N, 1H), 7.00 (d, J 7.0, C6H4, 1H), 6.84 (t, J
7.0, C6H4, 1H), 6,62 (m, C6H4 and C6H4N, 2H), 4.79 (d, J 14.0,
CH2, 1H), 3.97 (d, J 13.0, CH2, 1H), 2.48 (s, H2O, 2H). IR: 3637
m, 3518 m, 1610 s, 1578 s, 1566 s, 1339 s, 1191 s, 1095 s, 1082
m, 102 w, 966 m, 946 w, 924 w, 913 m, 890 w, 871 w, 851 m,
832 m, 693 m, 684 m, 667 m, 650 w, 622 m, 577 m, 508 w, 468
m, 447 m, 373 w. Anal. Calcd for C21H14F9NOPd: C, 43.96; H,
2.46; N, 2.44. Found: C, 43.83; H, 2.60; N, 2.62.
[P d (d m ba )(F m es)(CNtBu )], 2a . CNtBu (57 µL, 0.5 mmol)
was added to a solution of 1a (0.270 g, 0.5 mmol) in toluene
(25 mL). The solution was stirred at room temperature for 1
h. The solvent was removed in a vacuum, n-hexane (10 mL)
was added to the oily residue, and the volatiles were removed
in a vacuum again. This was repeated twice, and the solid
residue was recrystallized from CH2Cl2/hexane, yielding 0.223
g (74%) of 2a as a white microcrystalline solid. 19F NMR: δ
1
-61.40 (s, ortho-CF3, 6F), -62.68 (s, para-CF3, 3F). H NMR:
δ 7.86 (s, C6H2(CF3)3, 2H), 6.95 (d, J 7.0, C6H4 of dmba, 1H),
6.86 (td, J 7.0 and 1.0, C6H4 of dmba, 1H), 6.67 (td, J 7.5 and
1.0, C6H4 of dmba, 1H), 5.92 (dd, J 7.5 and 1, H3 of dmba, 1H),
3.89 (s, CH2 of dmba, 2H), 2.83 (s, CH3 of dmba, 6H), 1.33 (s,
CNC4H9, 9H). IR (CH2Cl2): 2188. IR: 2186 vs, 1620 s, 1581
m, 1560 m, 1407 w, 1300 s, 1278 m, 1186 m, 1128 m, 1081 w,
1025 m, 991 m, 972 w, 937 w, 928 w, 912 s, 873 w, 853 s, 833
m, 755 w, 748 m, 694 m, 685 s, 667 w, 620 w, 581 w, 525 w,
470 w, 439 w. Anal. Calcd for C23H23F9N2Pd: C, 45.74; H, 3.83;
N, 4.63. Found: C, 45.43; H, 3.74; N, 4.70.
[P d (p-tolp y)(F m es)(P P h 3)], 5b. PPh3 (0.052 g, 0.2 mmol)
was added to a solution of 1b (0.115 g, 0.2 mmol) in toluene
(10 mL). The solution was stirred at room temperature for 15
min. The solvent was removed in a vacuum, and the solid was
dissolved in 10 mL of Et2O. After 3 h stirring at room
temperature a white solid had precipitated spontaneously. The
solvent was decanted, and the solid was washed with Et2O (3
× 5 mL) and recrystallized from CH2Cl2/hexane, yielding 0.113
g (69%) of 5b as white crystals. 19F NMR: δ -59.80 (d, J PF
4.5, ortho-CF3, 6F), -62.76 (s, para-CF3, 3F). 31P{1H} NMR:
δ 21.1 (sept). 1H NMR: δ 7.93 (br, C6H5, 4H), 7.80 (m, p-tolpy,
2H), 7.67 (t, J 8.0, p-tolpy, 1H), 7.53 (m, p-tolpy, 1H), 7.51 (s,
C6H2(CF3)3, 2H), 7.4 (br, C6H5, 6H), 7.0 (br, C6H5, 3H), 6.86
(d, J 8.0, p-tolpy, 1H), 6.55 (t, J 7.0, p-tolpy, 1H), 6.5 (br, C6H5,
2H), 6.03 (d, J 6.0, H3, 1H), 2.04 (s, CH3 of p-tolpy, 3H). 1H
NMR (-60 °C): δ 7.94 (t, J 8.5, C6H5, 4H), 7.84 (m, p-tolpy,
2H), 7.72 (t, J 8.0, p-tolpy, 1H), 7.57 (d, J 7.5, p-tolpy, 1H),
7.48 (m, 2H of C6H2(CF3)3 and 2H of C6H5), 7.39 (m, C6H5, 4H),
7.02 (t, J 7.0, C6H5, 1H), 6.88 (d, J 8.0, p-tolpy, 1H), 6.81 (t, J
7.0, C6H5, 2H), 6.64 (t, J 7.0, p-tolpy, 1H), 6.40 (t, J 9.0, C6H5,
2H), 6.03 (d, J 6.0, H3 of p-tolpy, 1H), 2.03 (s, CH3 of p-tolpy,
3H). IR: 1620 m, 1608 m, 1591 w, 1569 m, 1371 s, 1297 m,
1280 s, 1189 m, 1114 s, 1096 w, 1076 w, 1023 m, 913 s, 852
m, 830 w, 814 w, 775 m, 752 m, 746 w, 684 m, 667 w, 528 m,
[P d(dm ba)(Fm es)(CO)], 3a. Carbon monoxide was bubbled
through a solution of 1a (0.540 g, 1.0 mmol) in toluene (40
mL), while the solution was stirred, at room temperature for
30 min. The solvent was removed in a vacuum, and the solid
residue was washed with n-hexane (3 × 5 mL), yielding an
off-white solid, which was recrystallized from CH2Cl2/hexane,
yielding 0.461 g (84%) of 3a as an off-white microcrystalline
solid. 19F NMR: δ -61.43 (s, ortho-CF3, 6F), -62.95 (s, para-
1
CF3, 3F). H NMR: δ 7.95 (s, C6H2(CF3)3, 2H), 7.00 (d, J 7.5,
C6H4 of dmba, 1H), 6.93 (t, J 7.5, C6H4 of dmba, 1H), 6.71 (t,
J 7.0, C6H4 of dmba, 1H), 5.85 (d, J 7.5, H3 of dmba, 1H), 3.99
(s, CH2 of dmba, 2H), 2.96 (s, CH3 of dmba, 6H). IR (CH2Cl2):
2105. IR: 2111 vs, 2061 w, 1623 vw, 1585 m, 1574 m, 1407 m,
1369 w, 1300 s, 1194 s, 1156 w, 1119 s, 1049 m, 1025 m, 992
w, 939 w, 915 s, 873 m, 854 s, 835 s, 747 s, 694 m, 684 s, 667
w, 580 w, 518 w, 469 w, 451 w, 438 w, 396 w, 334 w, 278 w.

Neutral Organometallic Pd(II) Aquo Complexes
Organometallics, Vol. 21, No. 17, 2002 3543
Ta ble 5. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for 1a
506 m, 490 m, 466 w, 441 w. Anal. Calcd for C39H27F9NPPd:
C, 57.26; H, 3.33; N, 1.71. Found: C, 57.14; H, 3.51; N, 1.95.
[P d (d m ba )(F m es)(lu t)], 6a . 2,6-Lutidine (24 µL, 0.2 mmol)
was added to a solution of 1a (0.108 g, 0.2 mmol) in toluene
(10 mL). The solution was stirred at room temperature for 15
h. Workup as for 2a yielded 0.085 g (68%) of 6a as a white
microcrystalline solid. 19F NMR: δ -59.48 (br, ortho-CF3, 6F),
-62.89 (s, para-CF3, 3F). 19F NMR (-60 °C): δ -58.13 (s,
ortho-CF3, 6F), -62.49 (s, para-CF3, 3F). 1H NMR (-60 °C):
δ 7.73 (s, C6H2(CF3)3, 2H), 7.51 (t, J 7.5, NC5H3(CH3)2, 1H),
7.03 (d, J 7.5, NC5H3(CH3)2, 2H), 6.9 (m, C6H4 of dmba, 2H),
6.68 (t, J 7.5, C6H4 of dmba, 1H), 6.06 (d, J 7.5, C6H4, H3 of
dmba, 1H), 3.99 (s, CH2 of dmba, 2H), 3.02 (s, CH3 of dmba,
6H), 2.35 (s, CH3, NC5H3(CH3)2, 6H). These NMR spectra show
also signals of 1a and free 2,6-lutidine (see Discussion). IR:
1619 s, 1584 s, 1565 m, 1403 m, 1369 s, 1355 w, 1295 s, 1187
s, 1072 s, 1048 w, 1018 m, 988 m, 971 w, 920 s, 863 w, 853 w,
843 m, 828 m, 781 m, 754 w, 692 w, 683 m, 667 w, 567 w, 520
w, 462 w, 440 w, 395 w, 326 w. Anal. Calcd for C25H23F9N2Pd:
C, 47.75; H, 3.69; N, 4.45. Found: C, 47.70; H, 3.77; N, 4.25.
[P d (d m ba -C)(F m es)(bip y)], 7a . 2,2′-Bipyridyl (0.031 g, 0.2
mmol) was added to a solution of 1a (0.108 g, 0.2 mmol) in
toluene (10 mL). The solution was stirred at room temperature
for 20 h. Workup as for 2a , yielded 0.065 g (48%) of 7a as a
pale yellow microcrystalline solid. 19F NMR: -59.31 (s, ortho-
CF3, 6F), -62.92 (s, para-CF3, 3F). 19F NMR (CD2Cl2, -95
°C): δ -59.01 (s, ortho-CF3, 3F), -59.85 (s, ortho-CF3, 3F),
-62.09 (s, para-CF3, 3F). These NMR spectra show also signals
of 1a (see Discussion). 1H NMR: δ 8.20 (br, N2C10H8C5H4N,
2H), 8.10 (br, C5H4N, 2H), 7.93 (t, J 7,5, C5H4N, 2H), 7.84 (s,
C6H2(CF3)3, 2H), 7.30 (m, C5H4N, 2H), 7.20 (br, C6H4 of dmba,
1H), 6.92 (t, J 7.5, C6H4 of dmba, 1H), 6.8 (br, C6H4 of dmba,
1H), 6.71 (st, J 7.5, C6H4 of dmba, 1H), 3.86 (s, CH2 of dmba,
2H), 2.21 (br, CH3 of dmba, 6H). 1H NMR (CD2Cl2, -95 °C):
δ 8.13 (m, N2C10H8, 2H), 8.00 (m, N2C10H8, 2H), 7.96 (s, C6H2-
(CF3)3, 1H), 7.75 (s, C6H2(CF3)3, 1H), 7.71 (d, J 5.0, N2C10H8,
1H), 7.57 (d, J 5.0, N2C10H8, 1H), 7.28 (m, 2H of N2C10H8 and
1H of C6H4 of dmba), 7.01 (d, J 7.5, C6H4 of dmba, 1H), 6.85
(t, J 7.5, C6H4 of dmba, 1H), 6.61 (t, J 7.5, C6H4 of dmba, 1H),
4.04 (d, J 15.0, CH2 of dmba, 1H), 3.42 (d, J 15.0, CH2 of dmba,
1H), 2.06 (s, CH3 of dmba, 6H). These NMR spectra show also
signals of 1a and free 2,2′-bipyridyl (see Discussion). IR: 1617
s, 1603 s, 1570 m, 1294 vs, 1280 vs, 1260 vs, 1188 vs, 1127 vs,
1075 m, 1022 s, 916 s, 852 m, 832 m, 759 s, 747 s, 693 w, 685
w, 666 w, 567 w, 465 w, 440 w, 426 w. Anal. Calcd for
empirical formula
fw
C18H16F9NOPd
539.72
cryst syst
space group
a (Å)
monoclinic
P21/c
9.286(1)
b (Å)
17.095(3)
c (Å)
12.895(2)
â (deg)
V (Å3)
Z
100.24(1)
2014.2(5)
4
1.780
1.011
1064
D
calc (g cm-3
)
abs coeff (mm-1
F(000)
)
cryst size (mm)
0.30 × 0.10 × 0.05
temperature (K)
θ range for data collection
wavelength (Å)
173(2)
2.00 to 27.48°
0.71073 (Mo KR)
-6 e h e 12, -22 e k e 22,
-16 e l e 16
12 520
4598 (Rint ) 0.0302)
3604
SADABS
index ranges
no. of reflns collected
no. of ind reflns
no. of obsd reflns [I > 2σ(I)]
abs corr
max. transmn
0.962
min. transmn
0.846
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
extinction coeff
4598/0/282
0.971
R1 ) 0.0292, wR2 ) 0.0642
R1 ) 0.0456, wR2 ) 0.0693
0.0011(2)
largest diff peak and hole (e Å-3
)
0.839 and -0.568
on weighted F2 values for all reflections (see Table 5).38 All
non-hydrogen atoms were assigned anisotropic displacement
parameters and refined without positional constraints. Hy-
drogen atoms H(20A) and H(20B) were located in the electron
density difference map, assigned isotropic displacement pa-
rameters and refined without positional constraints. All other
hydrogen atoms were constrained to ideal geometries and
refined with fixed isotropic displacement parameters. Refine-
ment proceeded smoothly to give residuals shown in Table 5.
Complex neutral-atom scattering factors were used.39
Ack n ow led gm en t. This work was supported by the
MCyT of Spain (Project BQU2001/2015) and J CyL
(Project VA80/99). We thank Dr. J ose´ Miguel Mart´ın-
AÄ lvarez for very helpful discussions.
C
28H22F9N3Pd: C, 49.61; H, 3.27; N, 6.19. Found: C, 49.65;
H, 3.40; N, 5.94.
X-r a y Diffr a ction Stu d y of 1a . Plate-shaped crystals were
grown by slow diffusion of concentrated dichloromethane
solutions of the complex into hexane at -20 °C. X-ray
measurements were made using a Bruker SMART CCD area-
detector diffractometer with Mo KR radiation (λ ) 0.71073 Å).35
Intensities were integrated36 from several series of exposures,
each exposure covering 0.3° in ω, and the total data set being
a hemisphere. Absorption corrections were applied, based on
multiple and symmetry-equivalent measurements.37 The struc-
ture was solved by direct methods and refined by least squares
Su p p or tin g In for m a tion Ava ila ble: Atomic positional
parameters for the freely refined atoms, bond lengths and
interbond angles, atomic displacement parameters, and hy-
drogen atom parameters. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM020198R
(37) Sheldrick, G. M. SADABS: A program for absorption correction
with the Siemens SMART system; University of Go¨ttingen: Germany,
1996.
(35) SMART diffractometer control software; Bruker Analytical
X-ray Instruments Inc.: Madison, WI, 1998.
(36) SAINT integration software; Siemens Analytical X-ray Instru-
ments Inc.: Madison, WI, 1994.
(38) SHELXTL program system version 5.1; Bruker Analytical X-ray
Instruments Inc.: Madison, WI, 1998.
(39) International Tables for Crystallography; Kluwer: Dordrecht,
1992; Vol. C.