Synthesis and molecular structure of Pd2(C6F5)2[μ-P(C6F 5)CH2CH2P(C6F5)2 ]2. A rare example of P-C bond cleavage in a fluoroaryl phosphine

Article abstract of DOI:10.1021/om0200712

A transition metal-mediated P-Ar_f cleavage in a tertiary fluoroarylphosphine was reported. The resulting dimer contained two bridging, chelated fluoroaryl phosphino-phosphido ligands. The P-Ar_f bond cleavage was seen as an anomaly, considering that strong electron-withdrawing groups enhance the rate of P-C(Ar) oxidative addition to low-valent transition metals. The fluoroaryl phosphino-phosphido ligand was seen as a rare example of a bent biphosphido bimetallic complex.

Full text of DOI:10.1021/om0200712

Organometallics 2002, 21, 2781-2784
2781
Notes
Syn th esis a n d Molecu la r Str u ctu r e of
P d 2(C6F 5)2[µ-P (C6F 5)CH2CH2P (C6F 5)2]2. A Ra r e Exa m p le of
P -C Bon d Clea va ge in a F lu or oa r yl P h osp h in e
Richard H. Heyn*,1a and Carl Henrik Go¨rbitz1b
Department of Hydrocarbon Process Chemistry, SINTEF Applied Chemistry, P.O. Box 124
Blindern, N-0314 Oslo, Norway, and Department of Chemistry, University of Oslo,
P.O. Box 1033 Blindern, N-0315 Oslo, Norway
Received J anuary 30, 2002
Summary: Prolonged reflux of a THF solution of Pd2-
(dba)3 (dba ) dibenzylideneacetone) and 2 equiv of the
fluoroaryl phosphine (C6F5)2PCH2CH2P(C6F5)2 results in
formation of the phosphido-phosphino-bridged dimer
Pd2(C6F5)2[µ-P(C6F5)CH2CH2P(C6F5)2]2, which is struc-
turally characterized as the Et2O adduct.
phosphine, which leads to an uncommon Pd dimer with
a chelating, bridging phosphino-phosphido ligand. The
first Pd(dfppe) complexes were characterized only re-
cently.4
Resu lts a n d Discu ssion
Fluorinated phosphines are of interest as sterically
tunable, π-acceptor ligands capable of supporting elec-
tron-poor metal centers.2 One commercially available
member of this class of ligands is the chelating fluoro-
aryl phosphine (C6F5)2PCH2CH2P(C6F5)2, dfppe, which
is reported to give enhanced hydroformylation3 and
olefin polymerization4 catalytic activities compared to
its more common, perprotio analogue, (C6H5)2PCH2-
CH2P(C6H5)2. While dfppe was first synthesized some
20 years ago,5 only a handful of coordination complexes
containing it have been isolated.6
An important, salutary property of fluorinated phos-
phines is their considerable inertness within the coor-
dination sphere of a metal center.2 The exception to the
rule is the ortho C-F bonds in fluoroaryl phosphines,
which have been disrupted in M(dfppe) (M ) Ru, Rh,
Ir)6e-j and Pt[PPh2(C6F5)] systems.7 However, while
transition metals are known to activate the P-C bond
in standard phenyl-containing mono- and chelating
diphosphines,8 the corresponding cleavage of the P-C(flu-
oroaryl) (P-Arf) bond is still a very rare occurrence. We
know of only one literature report of a transition metal-
mediated P-Arf bond cleavage, and that in a secondary
phosphine.9 We report herein the first example of a
transition metal-mediated P-Arf cleavage in a tertiary
The reaction of Pd2(dba)3 and 2 equiv of dfppe in thf-
d8 changes from a dark red and slightly heterogeneous
mixture to a yellow solution with a small amount of
black precipitate within 2 h. The 31P{1H} NMR spec-
trum of this solution contains three signals: two sharp
peaks at -16.5 and -6.5 ppm and a broad multiplet at
13.4 ppm. One explanation for the spectrum is an
equilibrium mixture of Pd(dfppe)2, Pd(dfppe)(thf-d8), and
Pd(dfppe)(dba), respectively, as has been observed in
related systems.10 The upfield signal is unambiguously
assigned to Pd(dfppe)2, as this is the only resonance
observed upon mixing Pd2(dba)3 and 4 equiv of dfppe.11
(6) M ) Cr, Mo, W: (a) Hersh, W. H.; Xu, P.; Wang, B.; Yom, J . W.;
Simpson, C. K. Inorg. Chem. 1996, 35, 5453. (b) Ernst, M. F.; Roddick,
D. M. Inorg. Chem. 1990, 29, 3627. (c) Reference 2e. (d) Cook, R. L.;
Morse, J . G. Inorg. Chem. 1984, 23, 2332. M ) Ru: (e) Bellabarba, R.
M.; Saunders, G. C.; Scott, S. Inorg. Chem. Commun. 2002, 5, 15. M
) Rh, Ir: (f) Bellabarba, R. M.; Nieuwenhuyzen, M.; Saunders, G. C.
Inorg. Chim. Acta 2001, 323, 78. (g) Atherton, M. J .; Fawcett, J .;
Holloway, J . H.; Hope, E. G.; Russell, D. R.; Saunders, G. C. J .
Organomet. Chem. 1999, 582, 163. (h) Atherton, M. J .; Fawcett, J .;
Holloway, J . H.; Hope, E. G.; Martin, S. M.; Russell, D. R.; Saunders,
G. C. J . Organomet. Chem. 1998, 555, 67. (i) Fawcett, J .; Friedrichs,
S.; Holloway, J . H.; Hope, E. G.; McKee, V.; Nieuwenhuyzen, M.;
Russell, D. R.; Saunders, G. C. J . Chem. Soc., Dalton Trans. 1998,
1477. (j) Atherton, M. J .; Fawcett, J .; Holloway, J . H.; Hope, E. G.;
Karac¸ar, A.; Russell, D. R.; Saunders, G. C. J . Chem. Soc., Dalton
Trans. 1996, 3215. (k) Atherton, M. J .; Coleman, K. S.; Fawcett, J .;
Holloway, J . H.; Hope, E. G.; Karac¸ar, A.; Peck, L. A.; Saunders, G. C.
J . Chem. Soc., Dalton Trans. 1995, 4029. (l) Fairlie, D. P.; Bosnich, B.
Organometallics 1988, 7, 936. M ) Pd, Pt: (m) Reference 4. (n)
Bennett, B. L.; Hoerter, J . M.; Houlis, J . F.; Roddick, D. M. Organo-
metallics 2000, 19, 615. (o) Reference 2c.
* Corresponding author. E-mail: Richard.H.Heyn@chem.sintef.no.
Fax: +47 22 06 73 50.
(1) (a) SINTEF Applied Chemistry. (b) University of Oslo. To whom
comments regarding the X-ray crystallography should be addressed.
E-mail: c.h.gorbitz@kjemi.uio.no. Fax: +47 22 85 54 41.
(2) (a) White, S.; Bennett, B. L.; Roddick, D. M. Organometallics
1999, 18, 2536. (b) Houlis, J . F.; Roddick, D. M. J . Am. Chem. Soc.
1998, 120, 11020. (c) Merwin, R. K.; Schnabel, R. C.; Koola, J . D.;
Roddick, D. M. Organometallics 1992, 11, 2972. (d) Koola, J . D.;
Roddick, D. M. J . Am. Chem. Soc. 1991, 113, 1450. (e) Ernst, M. F.;
Roddick, D. M. Inorg. Chem. 1989, 28, 1624.
(7) Park, S.; Pontier-J ohnson, M.; Roundhill, D. M. Inorg. Chem.
1990, 29, 2689.
(8) Garrou, P. E. Chem. Rev. 1985, 85, 171.
(9) (a) Ang, H. G.; Kwik, W. L.; Leong, W. K.; J ohnson, B. F. G.;
Lewis, J .; Raithby, P. R. J . Organomet. Chem. 1990, 396, C43. (b)
Ethylmagnesium bromide cleaves the P-C bond in P(C6F5)3. Sicree,
S. A.; Tamborski, C. J . Fluor. Chem. 1992, 59, 269.
(3) Chan, A. S. C.; Pai, C.-C.; Yang, T.-K.; Chen, S.-M. J . Chem.
Soc., Chem. Commun. 1995, 2031.
(4) Wursche, R.; Debaerdemaeker, T.; Klinga, M.; Rieger, B. Eur.
J . Inorg. Chem. 2000, 2063.
(10) Amatore, C.; Broeker, G.; J utland, A.; Khalil, F. J . Am. Chem.
Soc. 1997, 119, 5176.
(11) No changes were observed in the 31P{1H} spectrum of this
reaction after 3 days at RT. Heating to 66 °C for 66 h gave mainly
free dfppe plus unidentified products.
(5) Cook, R. L.; Morse, J . G. Inorg. Chem. 1982, 21, 4103.
10.1021/om0200712 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 05/25/2002

2782 Organometallics, Vol. 21, No. 13, 2002
Notes
Sch em e 1
Upon warming the equimolar reaction to 65 °C, a new
set of resonances in the 31P{1H} NMR spectrum grows
in over 66 h. At 100 °C, the reaction proceeds faster,
but free dfppe (as observed via 31P{1H} NMR spectros-
copy) and an increased amount of the black precipitate
result. The reaction also proceeds at room temperature;
yet, in contrast to the nearly quantitative conversion
observed at higher temperatures, only approximately
50% conversion is observed after 5 weeks, with no
further change in the 31P NMR spectrum after up to 15
weeks.
F igu r e 1. ORTEP drawing of the top view of R,R-1‚Et2O
showing a partial atom-labeling scheme and thermal
ellipsoids at the 30% probability level. Both the Et2O
solvent of crystallization and the H atoms are removed for
clarity. Selected bond distances (Å): Pd(1)-P(1) 2.3204(8),
Pd(1)-P(1a) 2.3211(8), Pd(1)-P(2) 2.2800(8), Pd(1)-C(41)
2.057(3). Selected bond angles (deg): P(1)-Pd(1)-P(1a)
81.34(3), P(1)-Pd(1)-P(2) 156.40(3), P(1a)-Pd(1)-P(2)
84.32(3), P(1)-Pd(1)-C(41) 94.8(1), P(1a)-Pd(1)-C(41)
172.9(1), P(2)-Pd(1)-C(41) 97.3(1), Pd(1)-P(1)-Pd(1a)
87.51(3).
A scaled-up reaction in refluxing thf provides the
isolation of air-stable, yellow microcrystals from Et2O.
1
The H NMR spectrum of the product is characterized
by four multiplets of equal intensity, in addition to
signals for Et2O. The 19F NMR spectrum shows 11
resolvable signals. Of these, three multiplets between
-123 and -128 ppm, each integrating to two F atoms,
and the three multiplets between -144 and -149 ppm,
each integrating to 1 F atom, can be respectively
assigned to the ortho- and para-F of three inequivalent
C6F5 groups derived from dfppe.2c,6e-k Additionally, the
spectrum shows a broad singlet integrating to two F
atoms at -112.32 ppm and an extra signal for 1 F atom
in the meta region (-155 to -165 ppm). These two
resonances are consistent with the ortho- and para-F
atoms, respectively, of a Pd-bound C6F5 group.12 The
31P{1H} NMR spectrum consists of two AA′XX′ six-line
multiplets at 19.34 and -99.06 ppm and has been
4
2
simulated to give coupling constants J 12 ) -48.6, J 13
) -7.9, 2J 14 ) 142.2, and J 34 ) 0 Hz. No P-F coupling
2
could be observed. The high-field signal is diagnostic for
a phosphido group bridging two noninteracting metal
centers.13 A structure consistent with the interpreted
spectroscopic data is shown in Scheme 1. Formally, each
of two [Pd(dfppe)] moieties has oxidatively added one
P-Arf bond of the other, giving rise to a dimer with two
chelating, bridging phosphino-phosphido ligands.
While the structure of this product can be deduced,
the NMR spectroscopic data cannot resolve the actual
stereochemistry of the compound arising from the two
stereogenic phosphido P atoms. As it cannot be deter-
mined whether the Pd2P2 core is planar, giving rise to
a meso compound, or bent, for which one or both of the
two enantiomers are possible,13c an X-ray crystal struc-
ture of the compound was undertaken. Two ORTEP14
F igu r e 2. ORTEP drawing of R,R-1‚Et2O showing only
the core atoms of the dimer with thermal ellipsoids at the
30% probability level.
views of the R,R-enantiomer of racemic 1‚Et2O are
shown in Figures 1 and 2; pertinent bonds and angles
are also listed in Figure 1. Overall, the molecule
possesses a butterfly structure, resulting from the bent
Pd2P2 core. A vertical C2 symmetry axis runs through
the center of the Pd2P2 core and relates the two halves
of the dimer. The symmetry element also passes asym-
metrically through an Et2O solvent molecule of crystal-
lization, resulting in a disorder. Despite the distortions
arising from the C2-bridge in 1‚Et2O (vida infra), this
is one of the few structural examples of an edge-sharing
square planar bimetallic complex with a strongly bent
bisphosphido bimetallic core.13d,15
(12) (a) Alonso, E.; Fornie´s, J .; Fortun˜o, C.; Mart´ın, A.; Rosair, G.
M.; Welch, A. J . Inorg. Chem. 1997, 36, 4426. (b) Fornie´s, J .; Fortun˜o,
C.; Navarro, R.; Mart´ınez, F.; Welch, A. J . J . Organomet. Chem. 1990,
394, 643. (c) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Casas, J . M.; Navarro,
R. J . Chem. Soc., Dalton Trans. 1989, 169.
(13) (a) Alonso, E.; Fornie´s, J .; Fortun˜o, C.; Toma´s, M. J . Chem. Soc.,
Dalton Trans. 1995, 3777. (b) Falvello, L. R.; Fornie´s, J .; Fortun˜o, C.;
Mart´ınez, F. Inorg. Chem. 1994, 33, 6242. (c) Glaser, R.; Kountz, D.
J .; Waid, R. D.; Gallucci, J . C.; Meek, D. W. J . Am. Chem. Soc. 1984,
106, 6324. (d) Meek, D. W.; Waid, R.; Tau, K. D.; Kirchner, R. M.;
Morimoto, C. N. Inorg. Chim. Acta 1982, 64, L221.
(14) ORTEP-3 for Windows. Farrugia, L. J . J . Appl. Crystallogr.
1997, 30, 565.

Notes
Organometallics, Vol. 21, No. 13, 2002 2783
Ta ble 1. Str u ctu r a l Da ta a for Com p a r a tive Ben t L2M(µ-XR2)ML2 Com p lexes
entry
compoundb
θc
M-X-M
X-M-X
M-X
M-M
ref
1
2
3
4
5
6
7
8
[Pt(µ-PhP(CH2)3PPh2)Me]2
[(dppe)Rh(µ-PPh2)]2
[(dppe)2Pd2(µ-PPE)]Cl2
[(dppe)2Pd2(µ-MPE)]Cl2
1‚Et2O
{Pt[µ-NHCH(C2H4SOMe)CO2]}2
{Pd[µ-N(p-tol)CH2py]Cl}2
[Pt(µ-NMeC6H4CH2dCMe)Cl]2
145d
133
126
99
95
95
90
87.5
89
89
91
75
75
68
69
81.3
82
84
82
2.32
2.36
2.34
2.34
2.32
2.04
2.05
2.08
3.52
3.47
3.47
3.30
3.21
2.86
2.88
2.98
13d
15b
15a
15a
this work
20
19a
118
131.5
136
141d
144d
19b
a
All angles in degrees, all distances in Å. bAbbreviations: dppe, Ph2PCH2CH2PPh2; PPE, PhPCH2CH2PPh; MPE, MePCH2CH2PMe.
cDihedral angle between the two X-M-X planes. dFrom ref 16a.
Ta ble 2. Cr ysta llogr a p h ic a n d Refin em en t
between the C(21)-C(26)/C(41)-C(46) rings and the
C(11)-C(16)/C(11a)-C(16a) rings of 1‚Et2O; the closest
contact distance for the first pair of rings is 3.25 Å
between C(22) and C(46), while the minimum separa-
tion for the latter pair is the 3.23 Å between C(12) and
C(12a). Furthermore, two of the three other structural
examples containing a five-membered chelate ring also
suffer from similar deformations.19 Only {Pt[µ-NHCH-
(C2H4SOMe)CO2]}2, which also has a six-membered
heterocyclic ring fused with the five-membered chelate
ring, exhibits a planar geometry at the metal center.20
The Pd(1)-Pd(1a) distance is 3.2100(5) Å, which indi-
cates the absence of a Pd-Pd bond.12a The Pd-P bond
distances in the Pd2P2 core are effectively equal at 2.32
Å, and these distances are 0.04 Å longer than the
external Pd(1)-P(2) bond distance of 2.2800(8) Å. The
different trans ligands account for the slightly shorter
Pd-P distance (av 2.256 Å) in (dfppe)PdI2.4 The Pd(1)-
C(41) distance of 2.057(3) Å is the same as reported21
for cis-Pt(C6F5)2(PPh3)2 and trans-[Pd(C6F5)(PEt3)2(S2-
CPEt3)]ClO4,22 but shorter than the corresponding bond
(av 2.086 Å) in [PEtPh3]2[Pt2(µ-PPh2)(C6F5)4].23
Attempts to synthesize the analogous Ni dimer via
related chemistry with Ni(COD)2 as a starting material
were unsuccessful. Prolonged heating (up to 6 days) at
65 °C of a stoichiometric 1:1 Ni(COD)2/dfppe thf-d8
solution gave free dfppe as the primary 31P NMR signal,
in addition to a number of unidentifiable signals and a
black precipitate. An analogous reaction in toluene-d8
at 100 °C gave only black decomposition products.
Interestingly, Pt(dfppe) complexes also do not appear
to undergo this P-C cleavage; refluxing Pt(dfppe)(Ph)2
in toluene or DMSO gives exclusively Pt(dfppe)2 after
the reductive elimination of biphenyl.2c
P a r a m eter s for 1‚Et2O
formula
C56H18F40OP4Pd2
1803.4
orthorhombic
Pbcn
13.800(2) Å
21.551(3) Å
20.021(2) Å
5954(1) Å3
4
radiation
λ (Å)
Mo KR
0.7107
293(2)
2.012
wt
syst
T (K)
space group
Dcalcd (g/mL)
a
b
c
V
Z
µ (mm-1
)
0.881
R(Fo)a
0.0394
0.0882
1.501
2
b
Rw(Fo
)
GOF
Calculated on 5399 reflections with I > 2σ(I). bCalculated on
all 6806 reflections.
a
Recent theoretical studies16 of the structural and
conformational preferences of edge-sharing binuclear d8
complexes of the form L2M(µ-XR2)ML2 concluded that
both the M-X distance and X-M-X angle are virtually
unaffected by the bending angle between the square
planes, θ, while the M-X-M angle decreases with
bending. Additionally, structures with five-membered
chelate rings were found to be bent, while those with
six-membered chelate rings were generally planar.
Table 1 collects comparative structural data for 1‚Et2O
and related complexes with either a bent bisphosphido
bimetallic core (entries 1-5) or a five-membered chelate
ring incorporating the bridging and terminal ligands
(entries 5-9). Perusal of these data reveals much less
variation in the M2X2 bond angles for complexes incor-
porating the chelate ring irrespective of the size of θ or
the M-X and M-M distances. The variance between
the metrical parameters for the M2P2 complexes and
theoretical predictions16a could be a consequence of the
different constraints placed upon the phosphido P atoms
in each of the bent bisphosphido bimetallic complexes.
The Pd atom possesses a severely distorted square
planar geometry, with P(2) displaced 0.61 Å out of the
plane defined by the remaining atoms Pd(1), P(1), P(1a),
and C(41)17 and a trans P(1)-Pd(1)-P(2) angle of
156.40(3)°. Distortions of similar proportions have re-
cently been measured in Pd18a and Rh18b complexes, and
aromatic π-π interactions have been held responsible
for these distortions.18b,c Analogous interactions exist
In summary, we have observed the first example of
transition metal-mediated P-Arf bond cleavage in a
tertiary fluoroarylphosphine, a consequence of a formal
oxidative addition to a presumed Pd(0) intermediate.
The resulting dimer contains two bridging, chelated,
fluoroaryl phosphino-phosphido ligands and is a rare
example of a bent bisphosphido bimetallic complex. That
other Pd(0) intermediates with bulky, chelating phos-
i
phines, such as R2PCH2CH2PR2 (R ) Pr, Cy), do not
(15) (a) Mizuta, T.; Aoki, S.; Nakayama, K.; Miyoshi, K. Inorg. Chem.
1999, 38, 4361. (b) Fultz, W. C.; Rheingold, A. L.; Kreter, P. E.; Meek,
D. W. Inorg. Chem. 1983, 22, 860.
(16) The dimers are defined as bent when the M2X2 dihedral angle
is less than 160°. (a) Aullo´n, G.; Lledo´s, A.; Alvarez, S. Inorg. Chem.
2000, 39, 906. (b) Aullo´n, G.; Ujaque, G.; Lledo´s, A.; Alvarez, S.;
Alemany, P. Inorg. Chem. 1998, 37, 804.
(17) The maximum displacement of the atoms defining the plane is
0.077 Å for Pd(1).
(18) (a) Drago, D.; Pregosin, P. S.; Tschoerner, M.; Albinati, A. J .
Chem. Soc., Dalton Trans. 1999, 2279. (b) Magistrato, A.; Merlin, M.;
Pregosin, P. S.; Rothlisberger, U.; Albinati, A. Organometallics 2000,
19, 3591. (c) Magistrato, A.; Pregosin, P. S.; Albinati, A.; Rothlisberger,
U. Organometallics 2001, 20, 4178.
(19) (a) Cuevas, J . V.; Garc´ıa-Herbosa, G.; Mun˜oz, A.; Garc´ıa-
Granda, S.; Miguel, D. Organometallics 1997, 16, 2220. (b) Cooper,
M. K.; Stevens, P. V.; McPartlin, M. J . Chem. Soc., Dalton Trans. 1983,
553.
(20) Freeman, W. A.; Nicholls, L. J .; Liu, C. F. Inorg. Chem. 1978,
17, 2989.
(21) Miki, K.; Kasai, N.; Kurosawa, H. Acta Crystallogr., Cryst.
Struct. Commun. 1988, C44, 1132.
(22) Uso´n, R.; Fornie´s, J .; Navarro, R.; Uso´n, M. A.; Garcia, M. P.;
Welch, A. J . J . Chem. Soc., Dalton Trans. 1984, 345.
(23) Alonso, E.; Casas, J . M.; Cotton, F. A.; Feng, X.; Fornie´s, J .;
Fortun˜o, C.; Tomas, M. Inorg. Chem. 1999, 38, 5034.

2784 Organometallics, Vol. 21, No. 13, 2002
Notes
) 7.0 H, OCH2), 3.13 (dm, 2 H, J ) 60 Hz, PCH), 2.69 (m, 2
H, PCH), 2.17 (dm, 2 H, J ) 57 Hz, PCH), 1.83 (m, 2 H, PCH),
1.16 (t, 6 H, J ) 7.0 Hz, OCCH3). 19F{1H} NMR (282.2 MHz,
thf-d8): δ -112.32 (br s, 2 F, o-PdC6F5), -123.39 (d, J FF ) 15
Hz, 2 F), -125.45 (br s, 2 F), -127.67 (d, J FF ) 20 Hz, 2F,
o-PC6F5), -144.30 (m, 1 F), -146.47 (app t, J FF ) 20 Hz, 1 F),
-148.47 (app t, J FF ) 20 Hz, 1 F; p-PC6F5), -158.65 (overlap-
ping signals, 3 F, p-PdC6F5, m-C6F5), -159.00 (m, 2 F), -160.06
(m, 2 F), -161.13 (m, 2 F, m-C6F5). 31P{1H} NMR (121.5 MHz,
undergo a similar oxidative addition but instead are in
equilibrium with the dinuclear complexes [(µ-R2PCH2-
24
CH2PR2)Pd]2 is consistent with the observation that
P-C(sp3) bonds are more difficult to cleave than P-C(sp2)
bonds.8 The singularity of this P-Arf bond cleavage is
somewhat surprising, however, considering that strong
electron-withdrawing groups enhance the rate of P-C(Ar)
oxidative addition to low-valent transition metals.25
4
2
thf-d8): δ 19.34 (m, PdP12C3), -99.06 (m, J 12 ) -48.6, J 13
)
2
2
-7.9, J 14 ) 142.2, J 34 ) 0 Hz, µ-P34Pd2).
Exp er im en ta l Section
Cr ysta l Str u ctu r e Deter m in a tion . A yellow blocklike
crystal was mounted on a glass fiber at room temperature.
Pertinent data for the crystal and solution are collected in
Gen er a l Com m en ts. All procedures were conducted using
Schlenk techniques under argon unless otherwise noted.
Where necessary, solvents were dried from Na/benzophenone
(thf and toluene) or LiAlH4 (pentane) and distilled prior to use.
Pd2(dba)3 and dfppe (Strem Chemicals) were used as received.
NMR spectra were referenced to the residual solvent peaks
(1H and 13C{1H} NMR), external C6H5CF3 (19F{1H} NMR,
referenced to -63.72 ppm), or external 85% H3PO4 (31P{1H}
NMR). The software package gNMR (Cherwell Scientific, Inc.)
was used for the NMR simulation. Elemental analysis was
performed by Ilse Beetz Mikroanalytisches Laboratorium,
Kronach, Germany.
Table 2. Diffraction data were collected on
a Siemens
SMART CCD diffractometer with SMART27a software and
were integrated using SAINT.27b A semiempirical absorption
correction was made with SADABS,27c the structure was solved
by direct methods in SHELXTL,27d and it was refined on F2
(SHELXTL).27d The diethyl ether solvent molecule is disor-
dered over two positions with occupancy 0.500. All non-
hydrogen atoms were refined anisotropically. Hydrogen atoms
were placed in idealized positions with Uiso values at 1.2 or
1.5Ueq of the carrier atom. Atomic scattering factors were
taken from the International Table for X-ray Crystallography
Vol C.
P d 2(C6F 5)2[µ-P (C6F 5)CH2CH2P (C6F 5)2]2‚Et2O (1‚Et2O). In
a 100 mL Schlenk flask, Pd2(dba)3 (0.34 g, 0.37 mmol) and
dfppe (0.57 g, 0.75 mmol) were dissolved in thf (40 mL) to give
a dark red solution. A condenser was placed on the flask, and
the solution was refluxed for 86 h. Upon reaching reflux, the
solution became golden-brown, and at the end of the reflux
the reaction was dark yellow with a small amount fine black
precipitate. After cooling, the volatiles were removed, and the
resulting olive green residue was washed with pentane (50 mL)
and Et2O (50 mL) to remove dba. The remaining reaction
residue was extracted with toluene (25 mL), the extract was
filtered through Celite, and the Celite was washed with
additional toluene (20 mL). The combined yellow filtrate and
wash were concentrated to ca. 10 mL, warmed to provide a
clear solution, and then cooled to -40 °C. The resulting mass
of yellow precipitate was filtered in air and washed with
pentane (50 mL). Dissolution of the solid in Et2O (75 mL),
followed by slow evaporation of the yellow solution, provided
0.15 g of 1‚Et2O as yellow microcrystals (0.080 mmol, 22%
yield). X-ray quality crystals were obtained from slow evapora-
tion from a concentrated thf-d8 solution. Anal. Calcd for
Ack n ow led gm en t. We would like to thank Aud M.
Bouzga for assistance with the multinuclear NMR
experiments and Richard Blom and Olav B. Ryan for
helpful discussions. The purchase of the SMART dif-
fractometer was made possible through support from
the Research Council of Norway (NFR). SINTEF Ap-
plied Chemistry and the Department of Hydrocarbon
Process Chemistry are also thanked for their encour-
agement to publish these results.
Su p p or tin g In for m a tion Ava ila ble: Tables of refined
and calculated atomic coordinates, bond lengths and angles,
and anisotropic thermal parameters for 1‚Et2O. This material
is available free of charge via the Internet at http://pubs.acs.org.
OM0200712
(26) Amount of residual Et2O after exposure to full vacuum for 36
h as determined by 1H NMR spectroscopy.
(27) (a) SMART, Version 5.054; Bruker AXS Inc.: Madison, WI,
1998. (b) SAINT, Version 6.01; Bruker AXS Inc.: Madison, WI, 1998.
(c) Sheldrick, G. M. SADABS; University of Go¨ttingen: Germany, 1996.
(d) Sheldrick, G. M. SHELXTL, Version 5.10; Bruker AXS Inc.:
Madison, WI, 1998.
C
52H8F40P4Pd2‚0.25C4H10O:26 C, 36.42; H, 0.61. Found: C,
1
36.41; H, 0.63. H NMR (300 MHz, CD2Cl2): δ 3.44 (q, 4 H, J
(24) Reid, S. M.; Fink, M. J . Organometallics 2001, 20, 2959.
(25) Dubois, R. A.; Garrou, P. E. Organometallics 1986, 5, 466.