Synthesis of novel phosphaalkene-based bidentate ligands Mes*P=CH(3-R-Ar) (R = pyridyl, carbaldimino) and formation of three-membered palladacycles Mes*(Me)P-CH(3-R-Ar)-PdCl by carbapalladation of the P=C double bond

Article abstract of DOI:10.1021/om980913q

Novel functionalized phosphaalkene-based bidentate ligands of the type 1-[(E)-Mes*P= C(H)]-3-R-benzene (8, R = N-phenylcarbaldimino; 2, R = 2-pyridyl; Mes* = 2,4,6-tri-tert-butylphenyl) were prepared via a Pd(0)-catalyzed cross-coupling reaction of (Z)-bromophosphaalkene (Z)-1 with Grignard reagents. The reaction of 8 and 2 with MePdCl(COD) furnished three-membered phosphapalladacycles of the type Mes*(Me)P-CH(3-R-Ar)-PdCl (9, R = N-phenylcarbaldimino; 10, R = 2-pyridyl), displaying intramolecular coordination between the phosphine ligand and palladium(II). The structure of 10 was established by an X-ray structure determination, showing a dimeric structure. The addition of triphenylphosphine to 9 and 10 causes rupture of the interconnecting Pd-N bonds, furnishing 11 and 12, respectively.

Full text of DOI:10.1021/om980913q

1402
Organometallics 1999, 18, 1402-1407
Syn th esis of Novel P h osp h a a lk en e-Ba sed Bid en ta te
Liga n d s Mes*P dCH(3-R-Ar ) (R ) P yr id yl, Ca r ba ld im in o)
a n d F or m a tion of Th r ee-Mem ber ed P a lla d a cycles
Mes*(Me)P -CH(3-R-Ar )-P d Cl by Ca r ba p a lla d a tion of th e
P dC Dou ble Bon d †
Marcel van der Sluis,‡ Vincent Beverwijk,‡ Arjan Termaten,‡
Friedrich Bickelhaupt,*,‡ Huub Kooijman,§ and Anthony L. Spek§
Scheikundig Laboratorium, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, The
Netherlands, and Bijvoet Center for Biomolecular Research, Crystal and Structural Chemistry,
Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
Received November 9, 1998
Novel functionalized phosphaalkene-based bidentate ligands of the type 1-[(E)-Mes*Pd
C(H)]-3-R-benzene (8, R ) N-phenylcarbaldimino; 2, R ) 2-pyridyl; Mes* ) 2,4,6-tri-tert-
butylphenyl) were prepared via a Pd(0)-catalyzed cross-coupling reaction of (Z)-bromophos-
phaalkene (Z)-1 with Grignard reagents. The reaction of 8 and 2 with MePdCl(COD)
furnished three-membered phosphapalladacycles of the type Mes*(Me)P-CH(3-R-Ar)-PdCl
(9, R ) N-phenylcarbaldimino; 10, R ) 2-pyridyl), displaying intramolecular coordination
between the phosphine ligand and palladium(II). The structure of 10 was established by an
X-ray structure determination, showing a dimeric structure. The addition of triphenylphos-
phine to 9 and 10 causes rupture of the interconnecting Pd-N bonds, furnishing 11 and 12,
respectively.
In tr od u ction
being the phosphorus analogues of the well-known
imines and pyridines,7-9 attract interest because of their
unique coordinative properties.
The development of the synthetic methodology for the
preparation of phosphaalkenes and phosphinines has
evolved into an important new area of organic chemistry
that is presently finding its application in organome-
tallic chemistry.1-6 Phosphaalkenes and phosphinines,
A special class of phosphaalkenes which are kineti-
cally stabilized by a bulky 2,4,6-tri-tert-butyl group
()supermesityl ) Mes*) at the phosphorus atom of the
PdC double bond has been applied in novel coordination
chemistry: Yoshifuji et al. reported (1,2-diphosphin-
idenecyclobutene)palladium dichloride complexes and
their application as homogeneous catalysts in a Heck
reaction.2c Geoffroy et al.1 developed the 1,3-bis(phos-
phaalkenyl)benzene ligand and Yoshifuji et al.2d the
1,3,4,6-tetrakis(phosphaalkenyl)benzene ligand, both of
which underwent bicyclometalation with PdCl2(PhCN)2.
For some time, our group has been engaged in the
development and application of halogen-substituted
phosphaalkenes.5 These reagents are expected to be
useful synthons for the preparation of novel function-
alized phosphaalkenes. Thus, their conversion into
phosphavinylidene carbenoids and (phosphaalkenyl)-
metal reagents has proved to be a versatile tool for
further functionalization, but the functionalization was
limited to C-C bond formation toward sp3-hybridized
carbon centers.5a,b For the preparation of bidentate
† Part of this paper was presented at the XIth International
Conference on Chemistry of Phosphorus Compounds (ICCPC-XI),
Kazan, Russia, Sept 8-13, 1996.
‡ Vrije Universiteit.
§ Utrecht University.
(1) (a) J ouaiti, A.; Geoffroy, M.; Terron, G.; Bernardinelli, G. J .
Chem. Soc., Chem. Commun. 1992, 155. (b) J ouaiti, A.; Geoffroy, G.;
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Geoffroy, G.; Bernardinelli, G. J . Chem. Soc., Dalton Trans. 1994, 1685.
(d) J ouaiti, A.; Geoffroy, M.; Terron, G.; Bernardinelli, G. J . Am. Chem.
Soc. 1995, 117, 2251. (e) J ouaiti, A.; Geoffroy, M.; Bernardinelli, G. J .
Chem. Soc., Chem. Commun. 1996, 437.
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N.; Hirotsu, K.; Higuchi, T. Tetrahedron 1988, 44, 1363. (c) Toyota,
K.; Masaki, K.; Abe, T.; Yoshifuji, M. Chem. Lett. 1995, 221. (d)
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M.; Ricard, L.; Mathey, F. Synthesis 1995, 717. (c) Mathey, F, Le Floch,
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Veldman, N.; Kooijman, H.; Spek, A. L. Chem. Ber. 1995, 128, 465. (b)
van der Sluis, M.; Wit, J . B. M.; Bickelhaupt, F. Organometallics 1996,
15, 174. (c) van der Sluis, M.; Klootwijk, A.; Wit, J . B. M.; Bickelhaupt,
F.; Veldman, N.; Spek, A. L.; J olly, P. W. J . Organomet. Chem. 1997,
529, 107. (d) van der Sluis, M.; Beverwijk, V.; Termaten, A.; Gavrilova,
E.; Bickelhaupt, F.; Veldman, N.; Kooijman, H.; Spek, A. L. Organo-
metallics 1997, 16, 1144.
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10.1021/om980913q CCC: $18.00 © 1999 American Chemical Society
Publication on Web 03/13/1999

Carbapalladation of the PdC Double Bond
Organometallics, Vol. 18, No. 8, 1999 1403
Sch em e 1
Sch em e 2
ligand systems analogous to those mentioned above,1,2c,d
the arylation of the phosphaalkene moiety would be
required.
Recently we discovered a convenient method for the
preparation of aryl-functionalized phosphaalkenes. The
monobromophosphaalkene (Z)-Mes*PdCHBr ((Z)-1) was
cross-coupled with aryl Grignard reagents in a Pd(0)-
catalyzed reaction.5c The reverse mode of coupling was
utilized in the preparation of pyridyl-functionalized
phosphaalkenes, which were applied as bidentate ligands
in novel Pd(II) complexes.5d
Here we present the application of this cross-coupling
reaction for the preparation of two potentially bidentate
ligands in which the two coordination sites are farther
apart: 3-(2-pyridyl)-phosphastyrene (2) and 3-(N-phen-
ylcarbaldimino)phosphastyrene (8). We also describe the
unique reactivity of these two phosphaalkenes with
MePdCl(COD) which unexpectedly gave the three-mem-
bered phosphapalladacycles 10 and 9, respectively, by
a novel insertion of the PdC bond into a palladium-
carbon bond.
had similarly been applied by Yoshifuji et al.2a,b,d and
Geoffroy et al.:1 lithium phosphide 4 was reacted with
3-bromobenzaldehyde at -65 °C, furnishing 5 in 82%
yield (Scheme 2). Product 5 was lithiated by a bromine-
lithium exchange reaction with n-butyllithium at -65
°C. The addition of dimethylformamide and subsequent
hydrolysis at room temperature furnished 6 as the only
product in 62% yield. The second route proceeds via the
dioxolane derivative 7, a “protected” form of 6.10 The
Grignard reagent prepared from 2-(3-bromophenyl)-1,3-
dioxolane and magnesium in THF was reacted with
(Z)-1 under the standard coupling conditions. After
workup, 7 was isolated in 62% yield as yellow crystals.
For the conversion of a dioxolane into an aldehyde, a
variety of mild reagents are known.10 However, quite
unexpectedly, harsh deprotection with hydrochloric acid
appeared to be the most convenient way. Although
phosphaalkenes generally react by addition of HCl to
the PdC double bond,11 stirring 7 overnight in a mixture
of diethyl ether and dilute hydrochloric acid at ambient
temperature furnished 6 in 57% yield.
Syn th esis
During our investigations on new methods for the
preparation of functionalized phosphaalkenes, we re-
cently developed a versatile Pd(0)-catalyzed cross-
coupling reaction of (Z)-1 with aryl Grignard reagents,
furnishing a variety of novel functionalized 2-phos-
phastyrenes in high yield and 100% isomeric purity.
This reaction has the same overall result as conven-
tional Stille-type coupling reactions but has a different
mechanistic course: it occurs with inversion of config-
uration and was therefore proposed to proceed through
an η2-palladium complex such as 3, which reacts with
the Grignard reagent under nucleophilic substitution
of bromine; the intermediate 3 was identified by NMR
spectroscopy.5c By the same procedure, (Z)-1 was con-
verted into the 3-(2-pyridyl)-2-phosphastyrene 2 by
cross-coupling with the Grignard reagent prepared from
1-bromo-3-(2-pyridyl)benzene. The product (Z)-2 was
isolated in 71% yield as an air-stable crystalline solid
(Scheme 1).
Finally, 8 was prepared by heating 6 with aniline in
the presence of molecular sieves in cyclohexane under
reflux (Scheme 2). The condensation was monitored by
31P NMR spectroscopy and was found to be complete
after 1.5 h. Removal of the molecular sieves, evaporation
(10) Kocienski, P. J . Protecting Groups; Georg Thieme Verlag:
Stuttgart, Germany, 1994.
(11) Appel, R. In Multiple Bonds and Low Coordination in Phos-
phorus Chemistry; Regitz, M., Scherer, O. J ., Eds.; Georg Thieme
Verlag: Stuttgart, Germany, 1990; Chapter 4, and references therein.
For the preparation of ligand 8, two less direct routes
were developed. The first route starts with bromophos-
phastyrene 5, obtained by the “classical” approach which

1404 Organometallics, Vol. 18, No. 8, 1999
van der Sluis et al.
Sch em e 3
Whatever the exact mechanism may be, its regiochem-
istry is in line with that of the addition of organometallic
reagents to PdC bonds in general. Due to the electro-
negativity x of the two elements involved (x(P) ) 2.1,
x(C) ) 2.5), the polarization of this bond is δ+PdCδ-
;
consequently, the carbanion equivalent adds to phos-
phorus and the metal adds to carbon. In contrast, the
CdN bonds of imines possess the opposite polariza-
tion (x(N) ) 3.0) and therefore show the opposite
regiochemistry in analogous additions; similarly, nitriles
R-CtN have recently been reported to insert into the
Ar-Pd bond to furnish palladaimines Ar(R)CdN-Pd.13
The addition of triphenylphosphine to 9 and 10 in
dichloromethane at room temperature leads to rupture
of the Pd-N bonds interconnecting the two units and
replaces them by the stronger Ph3P-Pd bonds to furnish
monomeric 11 and 12 in 80% and 67% yields, respec-
tively (Scheme 3); they were identified by their spectral
data. As the crystal structure of 10 shows it to be a
mixture of two enantiomers (RS and SR), this probably
holds for 11 and 12 as well. In both compounds, the 31P
NMR spectrum shows a double doublet with absorptions
at δ 22 and -39 (J (PP) ) 393-397 Hz). The character-
istic 31P chemical shift at δ -39 signals that the three-
membered palladacycle has been retained. The large
J (PP) value clearly indicates that in 11 and 12 the
phosphorus ligands at palladium are trans. In the case
of 12, the chemical shift of the pyridine ortho proton
(δ(1H) 8.66) shows that the pyridine ring is noncoordi-
nating; on coordination, this proton becomes more
deshielded, as illustrated by the value δ(1H) 9.05 in 10.
of the solvent, and crystallization conveniently fur-
nished 8 in 95% yield.
Coor d in a tion Ch em istr y of 2 a n d 8
Compounds 2 and 8 were reacted with MePdCl(COD)
in dichloromethane at ambient temperature for 5 min
(Scheme 3). Unexpectedly, we isolated not the straight-
forward mono- or bidentate complexes in which the
phosphaalkene is coordinated via phosphorus in a η1-
fashion to palladium, but the remarkable dimeric pal-
ladium(II) complexes 10 and 9, respectively, which
contain a three-membered ring involving palladium,
phosphorus, and carbon. This follows from their spec-
troscopic data and was, in the case of 10, confirmed by
an X-ray crystal structure determination (vide infra).
The 31P NMR spectra of 9 and 10 both show a
characteristic signal at δ(31P) -34 in CDCl3. This
indicates the conversion of the phosphaalkene moiety
(typical 31P NMR range 200-300 ppm) to a trivalent
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of 10
The structure of 10 shows a dimer located on a
crystallographic inversion center (point-symmetric and
dimeric); it contains two enantiomeric (RS and SR) 3-(2-
pyridyl)-1-[(supermesityl)(methyl)-η1-phosphino-σ-meth-
yl]benzene palladium chloride(II) units wherein the
σ-bonding ligands, C(1) and Cl(1), are fixed in a cis
arrangement around the square-planar palladium cen-
ter. The benzylic carbon atom C(1) is σ-bonded to
palladium, and the phosphorus atom P(1) is η1-coordi-
nated to palladium; thus, a three-membered pallada-
cycle is formed by intramolecular coordination. The
pyridine moiety of one unit coordinates to the palladium
center of the other one, which leads to the dimeric
structure (Figure 1, Tables 1 and 2). The asymmetric
unit contains four chloroform molecules, three of which
display a short C-H‚‚‚Cl interaction with the Pd-Cl
moiety.
The C(2)-P(1)-C(1)-C(3) moiety is planar with a
torsion angle of -0.8(9)°, and the H(1)-C(1)-P(1)-
C(14) moiety has a torsion angle of -11.4(8)°. The
P(1)-Pd(1)-C(1) angle (48.0(2)°) is very small compared
to the optimal angle of 90° for a square-planar pal-
ladium complex but is comparable to that of (Me3P)2-
Ni[(Me3Si)2CPC(H)(SiMe3)2] (P-Ni-C ) 48.9(2)°).14
This small angle is mainly compensated by the large
P(1)-Pd(1)-N(1)a angle (122.92(16)°).
1
σ3,λ3-phosphine. The H NMR spectra of 9 and 10 show
a signal for one proton at δ(1H) 3.10 (in CDCl3) and 3.38,
respectively, which suggests the presence of one benzylic
proton. One methyl group gave doublets at δ(1H) 2.19
and 2.01 (in CDCl3), respectively, with coupling con-
2
stants J ) 12.0 and 11.3 Hz, respectively, which are
characteristic for a P-Me moiety.
Presumably, after the usual initial η1-coordination of
these phosphaalkenes to methylpalladium chloride, an
insertion of the PdC bond into the palladium-methyl
bond occurred or, put in a different way, an addition of
the palladium-carbon bond to the PdC double bond or
carbapalladation. The mechanism of this reaction is
unknown; it may be analogous to the initial step in the
thoroughly studied Heck reaction.12 Next, the phospho-
rus lone pair forms a chelate bond to palladium.
(13) Luo, F.-H.; Chu, C.-I.; Cheng, C.-H. Organometallics 1998, 17,
1025.
(14) Cowley, A. H.; J ones, R. A.; Lasch, J . G.; Norman, N. C.;
Stewart, C. A.; Stuart, A. L.; Atwood, J . L.; Hunter, W. E.; Zhang, H.-
M. J . Am. Chem. Soc. 1984, 106, 7015.
(12) Cabri, W.; Candiani, I. Acc. Chem. Res. 1995, 28, 2.

Carbapalladation of the PdC Double Bond
Organometallics, Vol. 18, No. 8, 1999 1405
Ta ble 2. Selected Bon d Len gth s (Å), Bon d An gles
(d eg), a n d Tor sion An gles (d eg) for 10 (Esd s in
P a r en th eses)
Bond Lengths
P(1)-C(1)
1.754(8)
2.2217(19)
2.081(8)
2.168(6)
Pd(1)-Cl(1)
Pd(1)-C(14)
C(1)-C(3)
2.411(2)
1.841(8)
1.498(11)
1.464(11)
P(1)-Pd(1)
C(1)-Pd(1)
Pd(1)-N(1)a
C(5)-C(9)
Bond Angles and Torsion Angles
P(1)-Pd(1)-C(1)
P(1)-C(1)-Pd(1)
C(1)-Pd(1)-Cl(1)
C(1)-P(1)-Pd(1)
48.0(2)
70.2(3)
99.2(2)
61.8(2)
P(1)-C(1)-C(3)
132.9(6)
119.4(6)
179.2(2)
C(9)-N(1)-C(13)
P(1)-C(1)-Pd(1)-Cl(1)
C(1)-P(1)-Pd(1)-N(1)a -174.6(4)
Cl(1)-Pd(1)-N(1)a 89.73(16) C(3)-C(1)-P(1)-C(14)
134.7(7)
-0.8(9)
-11.4(8)
-4.8(12)
-36.3(10)
P(1)-Pd(1)-N(1)a 122.92(16) C(2)-P(1)-C(1)-C(3)
C(1)-P(1)-C(14) 108.6(4)
C(1)-P(1)-C(2)
C(2)-P(1)-Pd(1)
H(1)-C(1)-P(1)-C(14)
P(1)-C(1)-C(3)-C(4)
H(1)-C(1)-C(3)-C(8)
117.4(4)
117.7(2)
Pd(1)-P(1)-C(14) 121.2(2)
C(2)-P(1)-C(14) 117.0(3)
C(1)-P(1)-C(14)-C(15) -34.4(7)
C(6)-C(5)-C(9)-N(1) -143.9(7)
F igu r e 1. ORTEP24 drawing (30% probability level) of 10.
Hydrogen atoms and coordinating chloroform molecules
have been omitted for clarity.
a
Indicates symmetry operation 2 - x, 1 - y, -z.
P(1)-C(1) bond length is 1.754(8) Å, which is smaller
than but comparable to that in (Me3P)2Ni[(Me3Si)2C-
PC(H)(SiMe3)2]14 (d(P-C) ) 1.773(8) Å). A “normal” η1-
P(sp3)-C(sp3) bond length is 1.82 Å, which is consider-
ably longer.14 Finally, the P(1)-Pd(1) bond length is
2.2217(19) Å, which is comparable to that in (PAN)-
MePdCl (2.2009(8) Å).15
Ta ble 1. Cr ysta llogr a p h ic Da ta for 10
Crystal Data
formula
mol wt
cryst syst
space group
a, Å
C62H82Cl2N2P2Pd2‚8CHCl3
2156.06
monoclinic
P21/c (No. 14)
13.6333(17)
18.674(3)
18.330(3)
97.998(12)
4621.2(12)
1.549
Three-membered
metallacycles
of the type
b, Å
c, Å
R2P-CH2-M are well-established. They have been
isolated for several metals and have been prepared by
a variety of methods.16 However, only few examples of
the preparation of these species from phosphaalkenes
are known. Recently, Majoral et al. described the
hydrozirconation of phosphaalkenes leading to phos-
phazirconacyclopropanes.17 Geoffroy et al. reported the
formation and X-ray crystal structure of a phosphapal-
ladacyclopropane by reacting a phosphaalkene-PdCl2
complex with alcohols.1e Our carbapalladation of the
PdC double bond opens a novel approach to such
species.
â, deg
V, Å3
D
Z
calcd, g cm-3
2
F(000)
2176
12.1
0.2 × 0.2 × 0.3
µ, cm-1
cryst size, mm
Data Collection
T, K
θ
150
min, θmax, deg
1.09, 25.00
0.710 73 (graphite
monochromator)
ω
0.67 + 0.35 tan θ
3.00 + 1.50 tan θ, 4.00
91
wavelength (Mo KR), Å
scan type
∆ω, deg
horiz, vert aperture, mm
X-ray exposure time, h
linear decay, %
ref rflns
Exp er im en ta l Section
7
All experiments were performed in oven-dried glassware
and under nitrogen. Solvents were distilled from sodium
benzophenone (THF), lithium aluminum hydride (pentane,
diethyl ether), or calcium chloride (dichloromethane). All solid
starting materials were dried in vacuo. Liquids were distilled
under N2 prior to use. NMR spectra were recorded with a
Bruker AC 200 (1H, 13C (50.32 MHz)) and Bruker MSL 400
2h 4h1, 42h3, 2h6h2
-16 to +16, -22 to 0,
-21 to +21
16 009
data set (hkl)
total no. of data
total no. of unique data
8142 (Rint ) 0.108)
Refinement
no. of refined params
470
spectrometers (1H, 13C (100.63 MHz), variable-temperature 31
P
wR2a
0.1450
Rb
0.0655 (for 4313 Fo > 4σ(Fo))
1.016
(162.00 MHz)) or with a Bruker WM 250 spectrometer (31P
(101.25 MHz)). Tetramethylsilane (1H, 13C) or 85% H3PO4 (31P)
was used as an external standard. Mass spectra were recorded
with a Finnigan MAT 90 spectrometer; accurate masses were
determined by peak matching at a mass resolution of ap-
proximately 10 000. Elemental analyses were performed by
S
w-1 c
σ2(F 2) + (0.0500P)2
0.000, 0.006
-0.71, 0.72
(∆/σ)av, (∆/σ)max
min and max resid
density, e Å-3
2
2
2
a
b
wR2 ) [∑[w(Fo - Fc )2]/∑[w(Fo )2]]1/2
.
R ) ∑||Fo| - |Fc||/
∑|Fo|. c P ) (Max(Fo2, 0) + 2Fo2)/3.
(15) Dekker, G. P. C. M.; Buijs, A.; Elsevier, C. J .; Vrieze, K.; van
Leeuwen, P. W. N. M.; Smeets, W. J . J .; Spek, A. L.; Wang, Y. F.; Stam,
C. H. Organometallics 1992, 11, 1937.
The Pd(1)-N(1)a bond length is 2.168(6) Å, which is
comparable to that in [Mes*PdC(SiMe3)Py]MePdCl
(2.164(4) Å).5d The Pd(1)-Cl(1) bond length is 2.411(2)
Å, which is considerably longer than that in [Mes*PdC-
(SiMe3)Py]MePdCl (2.3545(14) Å) or in the phosphine
complex (PAN)MePdCl (2.3869(8) Å; PAN ) 1-(di-
methylamino)-8-(diphenylphosphino)naphthalene).15 The
(16) (a) Al-J ibori, S.; Crocker, C.; McDonald, W.; Shaw, B. L. J .
Chem. Soc., Dalton Trans. 1981, 1572. (b) Mainz, V. V.; Andersen, R.
A. Organometallics 1984, 3, 675. (c) Rabinovich, D.; Parkin, G. J . Am.
Chem. Soc. 1990, 112, 5381. (d) Anstice, H. M.; Fielding, H. H.; Gibson,
V. C.; Housecroft, C. E.; Kee, T. P. Organometallics 1991, 10, 2183.
(e) Kreissl, F. R.; Ostermeier, J .; Ogric, C. Chem. Ber. 1995, 128, 289
and references therein.
(17) (a) Dufour, N.; Caminade, A.-M.; Basso-Bert, M.; Igau, A.;
Majoral, J .-P. Organometallics 1992, 11, 1131. (b) Majoral, J .-P.;
Zablocka, M.; Igau, A.; Ce´nac, N. Chem. Ber. 1996, 129, 879.

1406 Organometallics, Vol. 18, No. 8, 1999
van der Sluis et al.
Microanalytisches Labor Pascher, Remagen, Germany. Com-
pounds (Z)-1,5c 4,2 and MePdCl(COD)18 were prepared accord-
ing to literature procedures.
F r om 7. To a solution of 7 (0.80 g, 1.82 mmol) in diethyl
ether (30 mL) was added dilute HCl in water (2.5 M, 10 mL).
The mixture was vigorously stirred overnight. The ether layer
was separated, dried over magnesium sulfate, and filtered. The
solvent was evaporated under reduced pressure, furnishing a
yellowish oil which solidified on standing. Crystallization of
the product from n-hexane furnished 6 (yield 0.41 g, 1.04
mmol, 57%); mp 90-92 °C. 1H NMR (CDCl3): δ 1.26 (s, 9H,
p-t-Bu), 1.42 (s, 18H, o-t-Bu), 7.35 [d, 2H, 4J (HP) ) 1.3 Hz, Ar
H], 7.36 (m, 1H), 7.65 (m, 2H), 7.92 (m, 1H), 8.04 [d, 1H, 2J (HP)
) 25.3 Hz, PdCH], 9.92 (s, 1H, OdCH). 13C{1H} NMR
(E)-((3-Br om op h en yl)m et h ylen e)(2,4,6-t r i-ter t-b u t yl-
p h en yl)p h osp h in e (5). 3-Bromobenzaldehyde (0.43 g, 2.33
mmol) was dropped into a solution of 4 (2.33 mmol) in THF
(10 mL) at -65 °C. The reaction mixture was warmed to room
temperature, after which trimethylsilyl chloride (0.26 g, 2.36
mmol) was added. The solvent was evaporated, and the orange
residue was dissolved in pentane. This solution was flushed
through a silica column. The pentane was evaporated under
reduced pressure, and the residue was crystallized from
acetonitrile, furnishing 5 as white crystals (yield 0.85 g, 1.91
mmol, 82%); mp 116-118 °C. 1H NMR (CDCl3): δ 1.34 (s, 9H,
p-t-Bu), 1.49 (s, 18H, o-t-Bu), 7.14 (m, 1H), 7.32 (m, 1H), 7.43
[d, 2H, 4J (HP) ) 1.3 Hz, Ar H], 7.68 (m, 1H), 7.99 [d, 1H,
2J (HP) ) 25.4 Hz, PdCH]. 13C{1H} NMR (CDCl3): δ 31.3 [s,
p-C(CH3)3], 33.7 [d, 4J (CP) ) 7.0 Hz, o-C(CH3)3], 34.9 [s,
p-C(CH3)3], 38.1 [s, o-C(CH3)3], 121.7 (s, m-Ar), 119.3-142.1
4
(CDCl3): δ 31.4 [s, p-C(CH3)3], 33.9 [d, J (CP) ) 6.9 Hz, o-C-
(CH3)3], 35.0 [s, p-C(CH3)3], 38.2 [s, o-C(CH3)3], 121.9 (s, m-Ar),
126.8-131.2 (aromatic C), 138.2 [d, 1J (CP) ) 53.2 Hz, ipso-
Ar], 140.8 [d, J (CP) ) 14.6 Hz], 149.9 (s, o-Ar), 154.0 (s, p-Ar),
173.7 [d, 1J (CP) ) 35.2 Hz, PdC], 191.9 (s, CdO). 31P NMR
(CDCl3): δ 270. MS (70 eV): m/z (%) 494 (5) [M+], 337 (3) [M+
- t-Bu]. HRMS: calcd for C26H35OP 394.2426, found 394.2426.
Anal. Calcd for C26H35OP: C, 79.15; H, 8.95. Found: C, 78.63;
H, 9.53.
1
(aromatic C), 149.8 (s, o-Ar), 153.9 (s, p-Ar), 173.5 [d, J (CP)
) 35.2 Hz, PdC]. 31P NMR (CDCl3): δ 269. MS (70 eV): m/z
(E)-((3-(N-P h en ylca r b a ld im in o)p h en yl)m et h ylen e)-
(2,4,6-tr i-ter t-bu tylp h en yl)p h osp h in e (8). Phosphaalkene
6 (2.29 g, 5.80 mmol) and aniline (0.65 mL, 7.0 mmol) were
dissolved in cyclohexane (25 mL). After the addition of mo-
lecular sieves (1.5 g; 8-12 mesh, 3 Å), the reaction mixture
was heated under reflux for 1.5 h. The solution was filtered,
and the solvent was evaporated under reduced pressure. The
residue was crystallized from n-hexane, furnishing 8 as a white
solid (yield 2.58 g, 5.51 mmol, 95%); mp 118-120 °C. 1H NMR
(CDCl3): δ 1.29 (s, 9H, p-t-Bu), 1.46 (s, 18H, o-t-Bu), 7.13 (m,
(%) 444 (4) [M+], 387 (1) [M+ - t-Bu]. HRMS: calcd for
C
25H34P79Br 444.1582, found 444.1582. Anal. Calcd for C25H34
-
PBr: C, 67.41; H, 7.70. Found: C, 67.38; H, 7.61.
(E)-((3-(1,3-Dioxol-2-yl)ph en yl)m eth ylen e)(2,4,6-tr i-ter t-
bu tylp h en yl)p h osp h in e (7). A solution of the Grignard
reagent, prepared by stirring 2-(3-bromophenyl)-1,3-dioxolane
(2.29 g, 10 mmol) with magnesium (0.48 g, 20 mmol) in THF
(20 mL), was dropped into a solution of (Z)-1 (1.44 g, 4 mmol),
tetrakis(triphenylphosphine)palladium(0) (5 mol %, prepared
in situ from Pd2(dba)3 (0.092 g, 0.1 mmol; dba ) dibenzylide-
neacetone), and triphenylphosphine (0.209 g, 0.8 mmol)) in
THF (5 mL). The reaction mixture was heated under reflux
for 6 h, after which the solvent was removed under reduced
pressure. The residue was added to the top of a small silica
column, which was flushed with dichloromethane. Evaporation
of the dichloromethane furnished a yellow solid. Crystallization
of the product from hot acetonitrile furnished yellow crystals
(yield 1.09 g, 2.48 mmol, 62%); mp 148-150 °C. 1H NMR
(CDCl3): δ 1.40 (s, 9H, p-t-Bu), 1.56 (s, 18H, o-t-Bu), 4.00-
4.21 (m, 4H, dioxolane CH2), 5.82 (s, 1H, dioxolane CH), 7.33
(m, 2H), 7.49 [d, 2H, 4J (HP) ) 1.0 Hz, Ar H], 7.58-7.70 (m,
2H), 8.16 [d, 1H, 2J (HP) ) 25.5 Hz, PdCH]. 13C{1H} NMR
4
3H), 7.31 (m, 3H), 7.38 [d, 2H, J (HP) ) 1.2 Hz, Ar H], 7.65
2
(m, 1H), 7.85 (m, 1H), 8.09 [d, 1H, J (HP) ) 25.4 Hz, PdCH],
8.39 (s, 1H, NdCH). 13C{1H} NMR (CDCl3): δ 31.4 [s, p-C-
(CH3)3], 33.9 [d, 4J (CP) ) 7.0 Hz, o-C(CH3)3], 35.0 [s, p-
C(CH3)3], 38.3 [s, o-C(CH3)3], 120.9-129.1 (aromatic C), 121.8
(s, m-Ar), 136.7 [d, J (CP) ) 2.5 Hz], 138.7 [d, 1J (CP) ) 53.3
Hz, ipso-Ar], 140.9 [d, J (CP) ) 13.9 Hz], 149.7 (s, o-Ar), 154.0
(s, p-Ar), 160.0 (s, NdC), 174.9 [d, 1J (CP) ) 35.7 Hz, PdC].
31P NMR (CDCl3): δ 265. MS (70 eV): m/z (%) 469 (12) [M+],
412 (4) [M+ - t-Bu]. HRMS: calcd for C32H40NP 469.2898,
found 469.2898. Anal. Calcd for C32H40NP: C, 81.83; H, 8.59.
Found: C, 81.14; H, 9.19.
3-(2-P yr id yl)br om oben zen e. To a solution of 2-(trimeth-
ylstannyl)pyridine (13.3 g, 55.0 mmol) in toluene (500 mL) was
added 1-bromo-3-iodobenzene (15.7 g, 55.0 mmol) and tetrakis-
(triphenylphosphine)palladium(0) (5 mol %, 3.2 g, 2.75 mmol).
The mixture was heated under reflux overnight, and the
progress of the reaction was monitored by GC-MS. The crude
product was separated from the reaction mixture by extraction
with hydrochloric acid. The aqueous layer was neutralized with
sodium hydroxide and then extracted with diethyl ether. The
solvent was evaporated and the product distilled under
vacuum (4 mmHg, 131 °C), furnishing the pure bromide (yield
9.3 g, 39.7 mmol, 72%). 1H NMR (CDCl3): δ 7.15 [t, 1H, J (HH)
) 4.9 Hz], 7.24 [t, 1H, J (HH) ) 7.9 Hz], 7.46 [d, 1H, J (HH) )
8.0 Hz], 7.60 [t, 1H, J (HH) ) 8.5 Hz], 7.64 [t, 1H, J (HH) ) 8.9
Hz], 7.83 [d, 1H, J (HH) ) 7.7 Hz], 8.13 (s, 1H), 8.62 [d, 1H,
J (HH) ) 4.6 Hz]. 13C{1H} NMR (CDCl3): δ 120.5 (s), 125.5
(s), 125.2 (s), 129.8 (s), 130.1 (s), 136.7 (s), 149.6 (s), 155.5 (s).
MS (70 eV): m/z (%) 233 (84) [M+], 154 (100) [M+ - Br].
HRMS: calcd for C11H8N79Br 232.9840, found 232.9845.
(E)-((3-(2-P yr id yl)p h en yl)m eth ylen e)(2,4,6-tr i-ter t-bu -
tylp h en yl)p h osp h in e (2). The Grignard reagent prepared
from 3-(2-pyridyl)bromobenzene (0.94 g, 4 mmol) and magne-
sium (0.19 g, 8 mmol) in THF was added to a solution of (Z)-1
(0.72 g, 2 mmol) and tetrakis(triphenylphosphine)palladium-
(0) (5 mol %), prepared in situ from Pd2(dba)3 (0.046 g) and
triphenylphosphine (0.10 g), in THF (5 mL). The reaction
mixture was heated under reflux for 6 h. The solvent was
evaporated, and the residue was flushed over a silica column:
first with pentane, which removes the organic byproducts, and
4
(CDCl3): δ 31.3 [s, p-C(CH3)3], 33.7 [d, J (CP) ) 7.1 Hz, o-C-
(CH3)3], 34.9 [s, p-C(CH3)3], 38.2 [s, o-C(CH3)3], 65.2 (s, dioxo-
lane CH2), 103.5 (s, dioxolane CH), 121.7 (s, m-Ar), 123.5-
140.3 (aromatic C), 149.6 (s, o-Ar), 153.9 (s, p-Ar), 175.3 [d,
1J (CP) ) 34.6 Hz, PdC]. 31P NMR (CDCl3): δ ) 262. MS (70
eV): m/z (%) 438 (22) [M+], 381 (2) [M+ - t-Bu]. HRMS: calcd
for C28H39O2P 438.2688, found 438.2687. Anal. Calcd for
C
28H39O2P: C, 76.67; H, 8.97; O, 7.30. Found: C, 76.41; H,
8.96; O, 7.13.
(E)-((3-F or m ylp h en yl)m et h ylen e)(2,4,6-t r i-ter t-b u t yl-
p h en yl)p h osp h in e (6). F r om 5. Phosphaalkene 5 (4.23 g,
9.49 mmol) was dissolved in THF (50 mL) and the solution
cooled to -65 °C. At -65 °C a solution of n-butyllithium in
hexane (6.25 mL, 1.6 M, 10 mmol) was added, furnishing a
red suspension. After the reaction mixture was stirred for 15
min at the same temperature, dimethylformamide (0.73 g, 9.99
mmol) was added. The mixture was warmed to room temper-
ature, after which a saturated solution of ammonium chloride
in water was added. The solvent was evaporated, and the
residue was extracted with pentane. After the pentane layer
was dried with magnesium sulfate and filtered, the pentane
was evaporated from the filtrate under reduced pressure,
furnishing a white solid. Crystallization of the product from
n-hexane furnished 6 (yield 2.30 g, 5.83 mmol, 62%). The
spectral data were identical with those of 6 prepared as
described below.
(18) 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.

Carbapalladation of the PdC Double Bond
Organometallics, Vol. 18, No. 8, 1999 1407
then with diethyl ether, which removes the product. The
product was crystallized from hot acetonitrile, furnishing 2
(yield 0.63 g, 1.42 mmol, 71%); mp 157-158 °C. 1H NMR
(CDCl3): δ 1.35 (s, 9H, p-t-Bu), 1.52 (s, 18H, o-t-Bu), 7.23 (m,
1H), 7.38 (m, 1H), 7.45 (s, 2H, Ar H), 7.63-7.88 (m, 4H), 8.12
853 (0.59) [M+ - Cl], 591 (1.9) [M+ - Cl - PPh3]. Anal. Calcd
for C51H58NP2ClPd: C, 68.91; H, 6.58; Pd, 12.0. Found: C,
67.97; H, 6.82; Pd, 12.1.
12: yield 0.29 g, 0.33 mmol, 67%; mp 110-113 °C. 1H NMR
(CDCl3): δ 1.32 (s, 18H, o-t-Bu), 1.90 (s, 9H, p-t-Bu), 2.26 [dd,
2
2
4
(s, 1H, o-Ph H), 8.18 [d, 1H, J (HP) ) 25.5 Hz, PdCH], 8.79
3H, J (HP) ) 10.9 Hz, J (HP) ) 4.0 Hz, P-Me], 2.64 (d, 1H,
2J (HP) ) 5.0 Hz, P-CH), 6.74 (m, 1H), 6.91-7.76 (m, aromatic
H), 8.66 [d, 1H, 3J (HH) ) 4.0 Hz, o-Py H]. 13C{1H} NMR
(CDCl3): δ 15.1 [dd, 1J (CP) ) 14.8 Hz, 3J (CP) ) 8.3 Hz, P-Me],
31.9 [s, p-C(CH3)3], 34.4 [d, o-C(CH3)3, J (CP) ) 27.7 Hz], 34.7
[s, p-C(CH3)3], 39.9 [d, o-C(CH3)3, J (CP) ) 10.1 Hz], 43.7 [d,
1J (CP) ) 23.2 Hz, CH], 117.6-161.0 (pyridyl and aromatic C).
31P NMR (CDCl3): δ 22 (d, 2J (PP) ) 393 Hz, PPh3), -39 (d,
2J (PP) ) 393 Hz, Mes*PMe). MS (EI, 70 eV): m/z (%) 863
(0.17) [M+], 827 (0.01) [M+ - Cl], 601 (2.9) [M+ - PPh3].
Cr ysta l Str u ctu r e Deter m in a tion a n d Refin em en t of
10. A yellow, block-shaped crystal was glued to the tip of a
glass fiber and transferred into the cold nitrogen stream on
an Enraf-Nonius CAD4-Turbo diffractometer on a rotating
anode. Accurate unit-cell parameters and an orientation
matrix were determined by least-squares fitting of the setting
angles of 25 well-centered reflections (SET419) in the range
9.95 < θ < 13.80°. Reduced-cell calculations did not indicate
higher lattice symmetry.20 Crystal data and details on data
collection and refinement are given in Table 1. Data were
corrected for Lp effects and the observed linear decay, but not
for absorption. The structure was solved by automated direct
methods (SHELXS9621). Refinement on F2 was carried out by
full-matrix least-squares techniques (SHELXL-9622); no ob-
servance criterion was applied during refinement. Hydrogen
atoms were included in the refinement on calculated positions
riding on their carrier atoms. All non-hydrogen atoms were
refined with anisotropic thermal parameters. The hydrogen
atoms were refined with a fixed isotropic displacement pa-
rameter related to the value of the equivalent isotropic
displacement parameter of their carrier atoms by a factor of
1.5 for the methyl hydrogen atoms and 1.2 for the other
hydrogen atoms, respectively. Neutral atom scattering factors
and anomalous dispersion corrections were taken from ref 23.
Geometrical calculations and illustrations were performed with
PLATON.24 All calculations were performed on a DECstation
5000/125.
(m, 1H, o-Py H). 13C{1H} NMR (CDCl3): δ 31.3 [s, p-C(CH3)3],
4
33.7 [d, J (CP) ) 7.0 Hz, o-C(CH3)3], 34.9 [s, p-C(CH3)3], 38.1
[s, o-C(CH3)3], 120.6-157.0 (pyridyl and aromatic C), 121.7 (s,
2
m-Ar), 140.9 [d, J (CP) ) 13.9 Hz], 149.5 [d, J (CP) ) 4.6 Hz,
o-Ar], 154.0 (s, p-Ar), 175.5 [d, 1J (CP) ) 34.6 Hz, PdC]. 31P
NMR (CDCl3): δ 258. MS (70 eV): m/z (%) 443 (12) [M+], 386
(6) [M+ - t-Bu]. HRMS: calcd for C30H38NP 443.2742, found
443.2740. Anal. Calcd for C30H38NP: C, 81.22; H, 8.64; N, 3.16.
Found: C, 80.83; H, 8.61; N, 3.15.
Gen er a l P r oced u r e for th e P r ep a r a tion of 9 a n d 10.
Ligand 8 (0.23 g, 0.5 mmol) or 2 (0.22 g, 0.5 mmol), respec-
tively, was mixed with MePdCl(COD) (0.13 g, 0.5 mmol) and
dissolved in dichloromethane (5 mL). The yellow-orange solu-
tion was stirred for 5 min at ambient temperature. The solvent
was evaporated, and the yellow residue was washed with
pentane (5 mL). The yellow product was dried under vacuum,
furnishing 9 and 10, respectively.
1
9: yield 0.23 g, 0.36 mmol, 71%; mp 183-185 °C. H NMR
(CDCl3): [δ 1.28 (s) and 1.31 (d, J ) 2.5 Hz), 18H, o-t-Bu],
2
[1.58 (br s) and 1.75 (br s), 9H, p-t-Bu], 2.19 [d, 3H, J (HP) )
12.0 Hz, P-Me], 3.10 (1H, P-CH), 7.20-7.76 (m, Ar H), 8.39
(s, 1H, NdCH). 13C{1H} NMR (CDCl3): δ 17.2 (P-Me), 31.0-
34.7 (p-t-Bu and o-t-Bu), 39.9 (s, CH), 115-155 (aromatic C).
31P NMR (CDCl3): δ -33.8 and -34.4. MS (EI, 70 eV): m/z
(%) 627 (12.6) [M+], 591 (50.6) [M+ - Cl], 575 (6.5) [M+ - Cl
- CH4]. HRMS: calcd for C33H43NP105Pd35Cl 624.1868, found
624.1860. Anal. Calcd for C33H43NPPdCl: C, 63.26; H, 6.92;
Pd, 16.9. Found: C, 62.67; H, 7.26; Pd, 16.9.
1
10: yield 0.27 g, 0.45 mmol, 90%; mp 179-181 °C. H NMR
(CDCl3): δ 0.97 (9H, o-t-Bu), 1.15 (9H, o-t-Bu), 1.22 (s, 9H,
p-t-Bu), 2.01 [d, 3H, 2J (HP) ) 11.3 Hz, P-Me], 3.38 (1H,
P-CH), 7.02 (m, 1H), 7.38 (s, 2H, Ar H), 7.60 (m, 1H), 7.71
(m, 3H), 8.44 (s, 1H, o-Ph H), 9.05 [d, 1H, 3J (HH) ) 5.5 Hz,
1
o-Py H]. 13C{1H} NMR (CDCl3): δ 17.5 [d, J (CP) ) 21.0 Hz,
P-Me], 30.8 [s, p-C(CH3)3], 33.6 [d, o-C(CH3)3, J (CP) ) 8.3 Hz],
34.4 [s, p-C(CH3)3], 38.9 [d, o-C(CH3)3, J (CP) ) 3.5 Hz], 40.3
(s, CH), 118.1-160.7 [pyridyl and aromatic C]. 31P NMR
(CDCl3): δ -34. MS (EI, 70 eV): m/z (%) 601 (0.8) [M+], 565
(2.1) [M+ - Cl], 549 (0.2) [M+ - Cl - CH4]. HRMS: calcd for
Ack n ow led gm en t. This work was supported in part
(A.L.S.) by the Netherlands Foundation of Chemical
Research (SON) with financial aid from the Netherlands
Organization for Scientific Research (NWO). Dr. F. J .
J . de Kanter is acknowledged for measuring NMR
spectra and Dr. B. L. M. van Baar for measuring high-
resolution mass spectra.
C
C
31H41NP104Pd35Cl 597.1701, found 597.1694. Anal. Calcd for
31H41NPPdCl: C, 62.00; H, 6.89; Pd, 17.7. Found: C, 61.86;
H, 7.18; Pd, 17.5.
Gen er a l P r oced u r e for th e P r ep a r a tion of 11 a n d 12.
To a solution of 9 or 10 in dichloromethane, prepared as
described above, was added 1 equiv of triphenylphosphine (0.13
g, 0.5 mmol). The solution was stirred for 10 min at ambient
temperature. After filtration the solvent was evaporated and
the yellow residue was washed with pentane (5 mL). The
yellow residue was dried under vacuum, furnishing 11 and
12, respectively.
1
Su p p or tin g In for m a tion Ava ila ble: Figures giving H,
13C, and 31P NMR spectra for 11 and 12 and tables of crystal
data and refinement details, positional and thermal param-
eters, and bond distances and angles for 10. This material is
available free of charge via the Internet at http://pubs.acs.org.
1
11: yield 0.36 g, 0.40 mmol, 80%; mp 91-93 °C. H NMR
OM980913Q
(CDCl3): δ 1.32 (s, 18H, o-t-Bu), 1.90 (s, 9H, p-t-Bu), 2.25 [dd,
2
4
(19) de Boer, J . L.; Duisenberg, A. J . M. Acta Crystallogr. 1984, A40,
C410.
3H, J (HP) ) 10.8 Hz, J (HP) ) 3.9 Hz, P-Me], 2.63 [d, 1H,
2J (HP) ) 4.6 Hz, P-CH], 6.66-7.58 (m, aromatic H), 8.15 (s,
1H, NdCH). 13C{1H} NMR (CDCl3): δ 16.0 (dd, P-Me), 30.8
[s, p-C(CH3)3], 33.9 [d, o-C(CH3)3, J (CP) ) 14.8 Hz], 34.6 [s,
p-C(CH3)3], 39.9 [d, o-C(CH3)3, J (CP) ) 15.14 Hz], 44.0 (dd,
CH), 120.7-151.8 (aromatic C), 159.8 (s, NdC). 31P NMR
(CDCl3): δ 22 (d, 2J (PP) ) 397 Hz, PPh3), -39 [d, 2J (PP) )
397 Hz, Mes*PMe]. MS (EI, 70 eV): m/z (%) 889 (1.38) [M+],
(20) Spek, A. L. J . Appl. Crystallogr. 1988, 21, 578.
(21) Sheldrick, G. M. SHELXS-96 Program for Crystal Structure
Determination; University of Go¨ttingen, Go¨ttingen, Germany, 1996.
(22) Sheldrick, G. M. Program for Crystal Structure Refinement;
University of Go¨ttingen, Go¨ttingen, Germany, 1996.
(23) Wilson, A. J . C., Ed. International Tables for Crystallography;
Kluwer Academic: Dordrecht, The Netherlands, 1992; Vol. C.
(24) Spek, A. L. Acta Crystallogr. 1990, A46, C34.