Palladium(II) complexes of α-stabilized phosphorus ylides

Article abstract of DOI:10.1021/om000429z

Using the α-stabilized phosphorus ylides PhC(O)CH double bond PPh₂CH₂CH₂PPh₂ double bond CHC (O)Ph and Ph₃P double bond CHC(NMe₂) double bond CH₂, novel palladium(II) complexes w

Full text of DOI:10.1021/om000429z

Organometallics 2000, 19, 3991-3993
3991
Notes
P a lla d iu m (II) Com p lexes of r-Sta bilized P h osp h or u s
Ylid es
Anke Spannenberg,* Wolfgang Baumann, and Uwe Rosenthal
Institut fu¨r Organische Katalyseforschung, Universita¨t Rostock, Buchbinderstrasse 5-6,
D-18055 Rostock, Germany
Received May 15, 2000
Summary: Using the R-stabilized phosphorus ylides
PhC(O)CHdPPh2CH2CH2PPh2dCHC(O)Ph and Ph3Pd
CHC(NMe2)dCH2, novel palladium(II) complexes were
synthesized: [PhC(O)CHdPPh2CH2CH2PPh2dCHC(O)-
Ph]PdCl2, where two asymmetric carbon centers were
formed, and the η3-allyl complex [Ph3PdCHC(NMe2)d
CH2]PdCl2 are easily accessible by exchange of cycloocta-
1,5-diene or benzonitrile in the corresponding palladium
complexes. The molecular structures of both complexes
were confirmed by X-ray crystal structure analysis.
thetic route analogous to that for the already known
ylides Ph3PdCHC(O)R (R ) Ph, Me)5 and Ph2PCH2CH2-
Ph2PdCHC(O)Ph.6 Here we report the reactions of both
ylides with Pd(II) complexes.
Resu lts a n d Discu ssion
The diphosphine Ph2PCH2CH2PPh2 reacts with 2
equiv of phenacyl bromide, BrCH2C(O)Ph, forming the
corresponding phosphonium salt (Scheme 1). Further
treatment with aqueous Na2CO3 solution leads to 2-fold
elimination of HBr, giving the free ligand 1.
In tr od u ction
The complexation of this ligand by palladium(II) is
possible by exchange reactions of COD or benzonitrile
starting from either Cl2Pd(COD) or Cl2Pd(PhCN)2. Such
a substitution by the bis-ylide 1 is shown in Scheme 2.
In the case of the reaction with Cl2Pd(COD) an addition
of the ylide to the cycloocta-1,5-diene was not observed.7
The search for nonmetallocene catalysts in catalytic
reactions, such as olefin polymerization, is the aim of
extensive research activities.1 Phosphorus ylide com-
plexes have been well investigated.2 They are versatile
ligands for catalysts in a very small number of catalytic
reactions such as, for example, the hydrogenation of
olefins3a and the cyclotrimerization3b and polymerization
of acetylenes,3c but the most important application is
in the industrially used SHOP process.3d Thus, the
nickel(II) complex [Ph2PCHC(Ph)O]NiPh(PPh3), ob-
tained by Keim et al. from the reaction of the R-carbo-
nyl-stabilized ylide Ph3PdCHC(O)Ph with Ni(COD)2 in
the presence of PPh3, is assumed to be one of the
catalytically active species in this olefin oligomerization.2b
R-Stabilized phosphorus ylides are distinguishable from
nonstabilized ylides, since they can be easily handled
due to an additional stabilization from delocalization of
the negative charge. We recently reported the synthesis
of Ph3PdCHC(NMe2)dCH2 by the reaction of Ph3Pd
CHC(O)Me with Ti(NMe)4.4 The bis-ylide PhC(O)CHd
PPh2CH2CH2PPh2dCHC(O)Ph was prepared by a syn-
The X-ray crystal structure analysis of 2 (Figure 1)
confirmed that the bis-ylide bonds to the soft metal
palladium in the C-coordination form, and therefore two
stereogenic centers are formed. Only one of the possible
diasteriomeric pairs, the one where both asymmetric
carbon atoms adopt the same chirality, crystallizes as
a racemic mixture (R,R and S,S enantiomers).
The coordination geometry is nearly square planar.
As a result of steric interactions the coordination plane
forms an angle with the remaining ligand fragment,
such that there is no molecular symmetry.
A (η3-allyl)palladium complex was obtained by ex-
change of COD or benzonitrile with Ph3PdCHC(NMe2)d
CH2 in either Cl2Pd(COD) or Cl2Pd(PhCN)2 (Scheme 3).
The molecular structure of 3, which was determined
by X-ray crystallography, is depicted in Figure 2. In
complex 3 an η3-allyl ligand and two chloro atoms are
coordinated to palladium(II). The atoms C1, C3, Cl1, and
Cl2 form a distorted square around the metal with C2
above this plane.
(1) Britovsek, G. J . P.; Gibson, V. C.; Wass, D. F. Angew. Chem.
1999, 111, 448; Angew. Chem., Int. Ed. 1999, 38, 428.
(2) (a) Weber, L. In The Chemistry of the Metal-Carbon Bond;
Hartley, F. R., Patai, S., Eds.; Wiley: 1982; Chapter 3. (b) Schmidbaur,
H. Angew. Chem. 1983, 95, 980; Angew. Chem., Int. Ed. Engl. 1983,
22, 907. (c) Navarro, R.; Urriolabeitia, E. P. J . Chem. Soc., Dalton
Trans. 1999, 4111. (d) Falvello, L. R.; Fernandez, S.; Navarro, R.;
Urriolabeitia, E. P. Inorg. Chem. 2000, 39, 2957.
(3) (a) Grey, R. A.; Anderson, L. R. Inorg. Chem. 1977, 16, 3187. (b)
Holy, N. L.; Baenziger, N. C.; Flynn, R. M. Angew. Chem. 1978, 90,
732. (c) Starzewski, K. A., O.; Witte, J . Angew. Chem. 1988, 100, 861;
Angew. Chem., Int. Ed. Engl. 1988, 27, 839. (d) Keim, W.; Bauer, R.
S.; Chung, H. C.; Glockner, P. U.S. Patent 3635937, 1969. Keim, W.;
Mason, R. F.; Glockner, P. U.S. Patent 3647914, 1972.
The angle between the planes defined by Cl1, Pd, Cl2
and C1, C2, C3 is 118°, nearly the same as found in
(5) Ramirez, F.; Dershowitz, S. J . Org. Chem. 1957, 22, 41.
(6) Oosawa, Y.; Miyamoto, T.; Saito, T.; Sasaki, Y. Chem. Lett. 1975,
33.
(4) Spannenberg, A.; Baumann, W.; Rosenthal, U. Appl. Organomet.
Chem. 2000, 14, 611.
(7) Vicente, J .; Chicote, M.-T.; MacBeath, C.; Fernandez-Baeza, J .;
Bautista, D. Organometallics 1999, 18, 2677.
10.1021/om000429z CCC: $19.00 © 2000 American Chemical Society
Publication on Web 08/23/2000

3992 Organometallics, Vol. 19, No. 19, 2000
Notes
Sch em e 1
Sch em e 3
other η3-allyl complexes.8,9 The distance P-C1 is com-
parable with those in other η3-phosphonium allyl-ylide
complexes.
The NMR spectra of both complexes (2 and 3) exhibit
features characteristic of a C-coordination of the ylides.10
The phosphorus resonance suffers a positive coordina-
tion shift of 8.1 ppm (2) or 12.1 and 16.1 ppm (3),
whereas negative (high-field) shifts would be expected
for an O-coordination. The decrease of the coupling
constants observed at the methine group of complex 3
1
(2J P,H by 14.5 Hz, J P,C by 56 Hz) is also indicative of
this bonding mode.
A special feature of the R-vinyl substituted ylide
Ph3PdCHC(NMe2)dCH2 in complex 3 is that the ole-
finic double bond participates in the coordination.
Therefore, and in agreement with the crystal structure
of 3, a high-field shift for the olefinic protons and a large
geminal coupling constant of 5.5 Hz were observed. An
allylic (η3) bonding mode results in a substitution
pattern (Ph3P group in the E position) which was
NOESY spectrum. Interestingly, under the measuring
conditions (T ) 297 K, mixing time 1.5 s) not only NOE
correlations are detected but also cross-peaks of opposite
phase between 1-H and 9-H, between the ortho protons
of the benzoyl group at C1 and of the benzoyl group at
C9, between the respective meta and para protons, and
also between the ortho protons of phenyl 19 and of
phenyl 31 (see Figure 1 for atom numbering). A kind of
chemical exchange must be operative, and inspection
of a ball-and-stick model revealed that the required
positional changes are easily achieved if the configura-
tion of both stereogenic centers, C1 and C9, which is S
for the depicted molecules, is inverted, perhaps after
ligand dissociation. Complex 2 must therefore be re-
garded as stereochemically labile.
1
confirmed by H NOE measurements.
Sch em e 2
The complexes 2 and 3 are moderately sensitive to
air and moisture. Both are very soluble in halogenated
solvents as dichloromethane and insoluble in nonpolar
solvents such as n-hexane.
Exp er im en ta l Section
The coordination of the bis-ylide 1 to PdCl2 creates
two stereogenic centers of the same configuration, and
complex 2 exhibits C1 symmetry, as indicated by the
presence of two 31P NMR signals (doublets of 4 Hz at
29.8 and 33.1 ppm). All atoms of the ligand are non-
equivalent and discriminable (although no attempt was
made to identify all resonances of the phosphorus bound
The bis-ylide 1 was prepared by a synthetic route analogous
to that for already known ylides.5,6 The synthesis of the ylide
Ph3PdCHC(NMe2)dCH2 was described previously.4 All other
reagents were obtained commercially and used as supplied.
The operations were carried out under an inert atmosphere
(argon) using Schlenk techniques. Prior to use, solvents were
dried and freshly distilled under argon. NMR spectra were
recorded on a Bruker ARX 400 spectrometer. 1H and 13C
chemical shifts are referenced to the solvent resonances and
reported relative to tetramethylsilane. Melting points were
determined in sealed capillaries on a Bu¨chi 535 apparatus.
Elemental analyses were performed with a Leco CHNS-932
elemental analyzer. The IR spectra were recorded on a Nicolet
1
phenyl groups) and were assigned with the aid of a H
(8) Facchin, G.; Bertani, R.; Calligaris, M.; Nardin, G.; Mari, M. J .
Chem. Soc., Dalton Trans. 1987, 1381 and references therein.
(9) Werner, H.; Mahr, N.; Frenking, G.; J onas, V. Organometallics
1995, 14, 619.
(10) Albanese, J . A.; Staley, D. L.; Rheingold, A. L.; Burmeister, J .
L. Inorg. Chem. 1990, 29, 2209 and references therein.

Notes
Organometallics, Vol. 19, No. 19, 2000 3993
least-squares techniques against F2 (SHELXL-93).13 XP (Sie-
mens Analytical X-ray Instruments, Inc.) was used for struc-
ture representations.
P h C(O)CHdP P h 2CH2CH2P P h 2dCHC(O)P h (1). Mp: 236
°C. Anal. Calcd for C42H36O2P2‚1/3CH2Cl2 (634.69): C, 76.69;
1
H, 5.57. Found: C, 76.84; H, 5.62. H NMR (CD2Cl2; δ, ppm):
3.24 (“d”, 4H, P-CH2), 4.24 (“t”, 2H, PdCH), 7.40 (m, 6H,
C-Ph), 7.46 (8H, P-Ph m), 7.54 (4H, P-Ph p), 7.78 (8H, P-Ph
o), 7.98 (m, 4H, C-Ph). 13C NMR (CD2Cl2; δ, ppm): 18.9 (“t”,
P-CH2), 47.1 (“t”, PdCH), 127.1 (Ph), 127.9 (i-C(O)Ph), 128.1
(Ph), 129.5 (“t”, o/m-P-Ph), 129.7 (p-C-Ph), 132.0 (“t”, o/m-
P-Ph), 132.5 (Ph), 141.5 (“t”, i-P-Ph), 185.5 (CO). 31P NMR
(CD2Cl2; δ, ppm): 17.7. IR (KBr; v˜CO, cm-1): 1509.
[P h C(O)CHdP P h 2CH2CH2P P h 2dCHC(O)P h ]P d Cl2 (2).
Cl2Pd(PhCN)2 (225 mg, 0.59 mmol) in 20 mL of CH2Cl2 was
added to PhC(O)CHdPPh2CH2CH2PPh2dCHC(O)Ph (373 mg,
0.59 mmol) in 20 mL of CH2Cl2. After it was stirred for 1 h,
the solution was filtered, concentrated in vacuo, and layered
with n-hexane. At -30 °C a yellow solid (220 mg, 46%)
precipitated.
Mp: 225 °C dec. Anal. Calcd for C42H36Cl2O2P2Pd‚CH2Cl2
(812.02): C, 57.58; H, 4.27. Found: C, 57.77; H, 4.51. 1H NMR
(CD2Cl2; δ, ppm): 2.90 (m, 2H, CH2), 3.11 (m, 1H, CH2), 3.44
(m, 1H, CH2), 4.42 (d, 2J H,P ) 2.9 Hz, 1-H), 5.95 (d, 2J H,P ) 1.1
Hz, 9-H), 7.91/6.66/7.14 (o/m/p, 1-benzoyl), 8.54/7.52/7.63 (o/
m/p, 9-benzoyl), 7.50/7.65/8.29/8.48 (2H each, o-P-Ph). 13C
NMR (CD2Cl2; δ, ppm (J C,P)): 16.7 (62 Hz, CH2), 20.1 (63 Hz,
F igu r e 1. Crystal structure of 2. The thermal ellipsoids
correspond to 30% probability. Selected bond lengths (Å)
and angles (deg): C1-P1 ) 1.816(6), C9-P2 ) 1.787(6),
Pd-Cl1 ) 2.380(2), Pd-Cl2 ) 2.337(2); Cl1-Pd-Cl2 )
88.82(6), C1-Pd-C9 ) 94.9(2).
1
1
CH2), 21.0 (48 Hz, J C,H ) 143 Hz, C9), 27.6 (43 Hz, J C,H
)
133 Hz, C1), 129.1/127.7/131.8 (o/m/p, 1-benzoyl), 129.9, 133.5,
133.4 (o/m/p, 9-benzoyl), 131.9 (9 Hz)/133.0 (9 Hz)/134.5 (10
Hz)/136.6 (10 Hz) (o-P-Ph), 128.5 (13 Hz)/129.8 (12 Hz)/129.9
(12 Hz)/130.1 (12 Hz) (m-P-Ph), 200.1/202.1 (CO). 31P NMR
2
2
(CD2Cl2; δ, ppm): 29.8 (d, J P,P ) 4 Hz, P1), 33.1 (d, J P,P ) 4
Hz, P2). IR (KBr; v˜CO, cm-1): 1679, 1632.
[P h 3P dCHC(NMe2)dCH2]P d Cl2 (3). Cl2Pd(PhCN)2 (302
mg, 0.79 mmol) in 20 mL of CH2Cl2 was added to Ph3PdCHC-
(NMe2)dCH2 (272 mg, 0.79 mmol) in 20 mL of CH2Cl2. The
reaction mixture was stirred for 1 h and then filtered. The
filtrate was concentrated in vacuo and layered with n-hexane.
At -30 °C a yellow solid (144 mg, 35%) precipitated. Mp: 214
°C. Anal. Calcd for C23H24Cl2NPPd (522.75): C, 52.85; H, 4.63;
1
N, 2.68. Found: C, 52.46; H, 4.36; N, 2.51. H NMR (CD2Cl2;
δ, ppm): 1.54 (d, 2J H,H ) 5.5 Hz, CH2(E)), 2.98 (s, NMe2), 3.08
F igu r e 2. Crystal structure of 3. Hydrogen atoms are
omitted for clarity. The thermal ellipsoids correspond to
30% probability. Selected bond lengths (Å) and angles
(deg): Pd-Cl1 ) 2.359(3), Pd-Cl2 ) 2.389(3), Pd-C1 )
2.108(12), Pd-C2 ) 2.231(12), Pd-C3 ) 2.090(12), C1-P
) 1.77(1), C1-C2 ) 1.46(2), C2-C3 ) 1.44(2); Cl1-Pd-
Cl2 ) 97.0(1).
2
4
4
(dd, J H,H ) 5.5 Hz, J H,H ) 2.9 Hz, CH2(Z)), 3.98 (dd, J H,H
)
2
2.9 Hz, J H,P ) 3.6 Hz), 7.67 (m, m-CH), 7.80 (m, p-CH), 7.87
(m, o-CH). 13C NMR (CD2Cl2; δ, ppm): 28.0 (1J C,P ) 76 Hz,
1J C,H ) 151 Hz, CH), 38.3 (1J C,H ) 161 Hz, CH2), 40.3 (1J C,H
)
138 Hz, NMe2), 121.8 (1J C,P ) 89 Hz, i-C), 130.1 (3J C,P ) 13
Hz, m-CH), 134.5 (2J C,P ) 10 Hz, o-CH), 134.9 (4J C,P ) 3 Hz,
p-CH), 144.7 (2J C,P ) 7 Hz, Cquat). 31P NMR (CD2Cl2; δ, ppm):
18.6. IR (Nujol; v˜CCC, cm-1): 1541.
Magna 550 spectrometer. X-ray data of compound 2 and 311
were collected on a STOE-IPDS diffractometer using graphite-
monochromated Mo KR radiation. The structures were solved
by direct methods (SHELXS-86)12 and refined by full-matrix
Ack n ow led gm en t. We gratefully acknowledge the
financial support from the Max-Planck-Gesellschaft and
the Fonds der Chemischen Industrie.
(11) For the X-ray crystal structure analysis suitable crystals of 2
and 3 were obtained from a CH2Cl2/hexane solution. The crystals of
both complexes contain CH2Cl2 as solvent. Crystal data for 2: crystal
dimensions 0.4 × 0.3 × 0.3 mm, yellow prisms, space group P21/n,
monoclinic, a ) 11.832(2) Å, b ) 16.017(3) Å, c ) 25.262(5) Å, â )
96.11(3)°, V ) 4760(2) Å3, Z ) 4, Fcalcd ) 1.488 g cm-3, 12 728 reflections
measured, 7000 were independent of symmetry and 4594 were
observed (I > 2σ(I)), R1 ) 0.056, wR2(all data) ) 0.149, 505 param-
eters. Crystal data for 3: crystal dimensions 0.2 × 0.1 × 0.1, yellow
prisms, space group P1h, triclinic, a ) 8.395(2) Å, b ) 12.482(2) Å, c )
13.202(3) Å, R ) 99.94(3)°, â ) 91.40(3)°, γ ) 94.95(3)°, V ) 1356.5(5)
Å3, Z ) 2, Fcalcd ) 1.592 g cm-3, 2782 reflections measured, 2782 were
independent of symmetry, and 1777 were observed (I > 2σ(I)), R1 )
0.070, wR2(all data) ) 0.182, 281 parameters.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and structure refinement details, atomic coordinates,
bond lengths and angles, anisotropic displacement parameters,
and hydrogen coordinates for 2 and 3. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM000429Z
(13) Sheldrick, G. M. SHELXL-93; University of Go¨ttingen, Go¨ttin-
gen, Germany, 1993.
(12) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.