A new family of P,N chelates: Stereoselective synthesis of 2-pyridyl-2-phospholenes in the coordination sphere of palladium(II) complexes

Article abstract of DOI:10.1021/om049510i

The synthesis of Pd(II) complexes 2a,c′, bearing 2-(2-pyridyl) phosphole ligands which act as P,N chelates, is described. Ligands featuring a pendant pyridyl group spontaneously evolve to the corresponding 2-pyridyl-2-phospholene derivatives in the coordination sphere of Pd(II). This isomerization is a stereoselective process, the stereochemistry of the resulting derivatives 3a,a′ being established by X-ray diffraction studies. The isomerization of ligands lacking pendant pyridyl groups was accomplished by adding pyridine to the reaction media. High yields were achieved under very mild conditions for ligands possessing different substitution patterns. Multinuclear NMR spectroscopic data and X-ray diffraction studies showed that the stereoselectivity of the process is preserved under these new reaction conditions. The transformation did not occur with free 2-(2-pyridyl)phospholes, even at high temperatures in the presence of pyridine. DFT calculations confirmed that coordination to a Pd(II) center is required to make this isomerization thermodynamically feasible. The isomerization has also been demonstrated with Pt(II) precursors but failed with CuCl, CuCl₂, and ZnCl₂. The free 2-pyridyl-2-phospholenes 4a,c′ were obtained by reacting the complexes 3a,c′ with dppe. No inversion of the P atom of the phospholene ring was observed up to 90°C, indicating that this novel family of P,N chelates is a promising class of ligand for homogeneous catalysis.

Full text of DOI:10.1021/om049510i

Organometallics 2004, 23, 6191-6201
6191
A New Family of P,N Chelates: Stereoselective Synthesis
of 2-Pyridyl-2-phospholenes in the Coordination Sphere
of Palladium(II) Complexes
Franc¸ois Leca,† Christophe Lescop,† Lo¨ıc Toupet,‡ and Re´gis Re´au*,†
UMR 6509 CNRS-Universite´ de Rennes 1, Institut de Chimie, and Groupe de la Matie`re
Condense´e et des Mate´riaux, UMR 6626 CNRS-Universite´ de Rennes 1,
Campus de Beaulieu, 35042 Rennes Cedex, France
Received July 2, 2004
The synthesis of Pd(II) complexes 2a,c′, bearing 2-(2-pyridyl)phosphole ligands which act
as P,N chelates, is described. Ligands featuring a pendant pyridyl group spontaneously evolve
to the corresponding 2-pyridyl-2-phospholene derivatives in the coordination sphere of Pd(II).
This isomerization is a stereoselective process, the stereochemistry of the resulting derivatives
3a,a′ being established by X-ray diffraction studies. The isomerization of ligands lacking
pendant pyridyl groups was accomplished by adding pyridine to the reaction media. High
yields were achieved under very mild conditions for ligands possessing different substitution
patterns. Multinuclear NMR spectroscopic data and X-ray diffraction studies showed that
the stereoselectivity of the process is preserved under these new reaction conditions. The
transformation did not occur with free 2-(2-pyridyl)phospholes, even at high temperatures
in the presence of pyridine. DFT calculations confirmed that coordination to a Pd(II) center
is required to make this isomerization thermodynamically feasible. The isomerization has
also been demonstrated with Pt(II) precursors but failed with CuCl, CuCl2, and ZnCl2. The
free 2-pyridyl-2-phospholenes 4a,c′ were obtained by reacting the complexes 3a,c′ with dppe.
No inversion of the P atom of the phospholene ring was observed up to 90 °C, indicating
that this novel family of P,N chelates is a promising class of ligand for homogeneous catalysis.
Introduction
reaction,4 reduction of alkenes or ketones,6-8 and olefin-
CO copolymerization.9 In these contexts, phospholanes
and phospholes have appeared as attractive P donors
(derivatives V-VIII, Figure 1). The electronic and
stereochemical properties of these five-membered phos-
phorus heterocycles are directly related to their degree
of unsaturation. First, phospholanes are more electron-
rich P-donors than the corresponding phospholes.10
Second, the phosphorus atom of phospholanes is a stable
stereogenic center,10,11 while that of phospholes inverts
rapidly at room temperature, due to the aromatic
character of the planar transition-state structure.10-13
Heteroditopic P,N chelates have attracted consider-
able interest in coordination chemistry and homoge-
neous catalysis for several decades.1 The success of these
mixed-donor ligands arises from the different stereo-
electronic properties of the two coordination sites,
providing unique reactivity to their metal complexes.
For example, P,N chelates can act as hemilabile ligands
or induce selective processes, allowing control over the
reactivity of the metal centers. Many different N donors
(imines, pyridines, quinolines, oxazolines, pyrazolines,
oxazines, etc.) have been used for the design of P,N
chelates.1 In contrast, less attention has been paid to
the variation of the P donors, the great majority of P,N
ligands bearing diarylphosphino fragments. Very re-
cently, derivatives based on other P moieties (Figure 1)
have emerged as appealing ligands for important cata-
lytic reactions, including allylic alkylation,2-5 the Heck
(2) Shintani, R.; Lo, M. M-C.; Fu, G.-C. Org. Lett. 2000, 2, 23, 3695.
(3) Delapierre, G.; Brunel, J. M.; Constantieux, T.; Labande, A.;
Lubatti, F.; Buono, G. Tetrahedron: Asymmetry 2001, 12, 1345.
(4) Gilbertson, S. R.; Genov, D. G.; Rheingold, A. L. Org. Lett. 2000,
2, 18, 2885.
(5) Zablocka, M.; Koprowski, M.; Donnadieu, B.; Majoral, J.-P.;
Achard, M.; Buono, G. Tetrahedron Lett. 2003, 44, 2413.
(6) Bunlaksananusorn, T.; Polborn, K.; Knochel, P. Angew. Chem.,
Int. Ed. 2003, 42, 3941.
* To whom correspondence should be addressed. Fax: +33 (0)-
223236939. Phone: +33 (0)223235784. E-mail: regis.reau@
univ-rennes1.fr.
(7) Tang, W.; Wang, W.; Zhang, X. Angew. Chem., Int. Ed. 2003,
42, 943.
† UMR 6509 CNRS.
(8) Thoumazet, C.; Melaimi, M.; Ricard, L.; Mathey, F.; Le Floch,
P. Organometallics 2003, 22, 1580.
‡ UMR 6626 CNRS.
(1) (a) Braunstein, P.; Naud, F. Angew. Chem., Int. Ed. Engl. 2001,
40, 680. (b) Helmchem, G.; Pfaltz, A. Acc. Chem. Res. 2000, 33, 336.
(c) Drury, W. J., III; Zimmermann, N.; Keenan, M.; Hayashi, M.;
Kaiser, S.; Goddard, R.; Pfaltz, A. Angew. Chem., Int. Ed. 2004, 43,
70. (d) Chelucci, G.; Orru, G.; Pinna, G. A. Tetrahedron 2003, 59, 9471.
(e) Espinet, P.; Soulantica, K. Coord. Chem. Rev. 1999, 193-195, 499.
(f) Braunstein, P.; Knorr, M.; Stern, C. Coord. Chem. Rev. 1998, 178-
180, 9039. (g) Bianchini, C.; Meli, A. Coord. Chem. Rev. 2002, 225, 35.
(h) Guiry, P. J.; Saunders, C. P. Adv. Synth. Catal. 2004, 346, 497.
(9) Sauthier, M.; Leca, F.; Toupet, L.; Re´au, R. Organometallics
2002, 21, 1591.
(10) Mathey, F. Phosphorus-Carbon Heterocyclic Chemistry: The
Rise of a New Domain; Elsevier Science: Oxford, U.K., 2001.
(11) (a) Egan, W.; Tang, R.; Zon, G.; Mislow, K. J. Am. Chem. Soc,
1971, 93, 6205. (b) Mathey, F. Chem. Rev. 1988, 88, 429. (c) Quin, L.
D. In Comprehensive Heterocyclic Chemistry; Katritzky, A. R., Ed.;
Pergamon: Oxford, U.K., 1996; p 757.
(12) Nyula´szi, L. Chem. Rev. 2001, 101, 1229.
10.1021/om049510i CCC: $27.50 © 2004 American Chemical Society
Publication on Web 11/20/2004

6192 Organometallics, Vol. 23, No. 26, 2004
Leca et al.
Figure 1. P,N ligands featuring various P moieties.
Scheme 1
Table 1. Selected Spectroscopic Dataa for
Compounds 2-6
Ligands based on 2-phospholenes, which constitute an
interesting “intermediate case”, have been poorly in-
vestigated due to the somewhat underdeveloped chem-
istry of this P heterocycle.10,14,15 In this paper, we report
a general and straightforward route to the first P,N
chelates featuring 2-phospholene moieties. The key step
of this process is a stereoselective base-catalyzed isomer-
ization of a phosphole ring into the corresponding
2-phospholene triggered by coordination to a square-
planar Pd(II) or Pt(II) center.15
compd
yield (%)
δ(31P)
PCH δ(13C) (JPC
)
δ(1H) (2JPH
)
2a
2a′
2b
2b′
2c
2c′
3a
3a′
3b
3b′
3c
3c′
4a
4a′
4b
4b′
4c
4c′
5
95
90
89
92
96
90
91
94
91
91
88
87
95
93
92
90
95
85
79
83
55.2
73.6
56.2
72.4
59.1
69.0
67.3
86.5
69.8
84.3
69.0
82.6
22.7
34.9
25.1
37.2
22.4
36.6
37.3
41.2
57.6 (36.6)
48.3 (32.7)
53.7 (36.4)
47.7 (32.3)
57.2 (36.6)
48.9 (33.6)
55.4 (8.1)
48.9 (10)
56.4 (8.1)
48.1 (11)
56.0 (8.5)
48.8 (11.8)
4.66 (11.9)
4.59 (7.3)
4.61 (13.0)
4.60 (6.2)
4.56 (10.8)
4.63 (8.2)
4.50 (4.7)
4.51 (m)
4.22 (4.9)
4.12 (m)
4.49 (4.6)
4.17 (2.3)
Results and Discussion
The Pd(II) complexes 2a,a′16 and 2b,c′ (Scheme 1)
were prepared in excellent yields (Table 1) by reacting
the corresponding 2-(2-pyridyl)phospholes9,17 1a-c and
1a′-c′ with PdCl2(CH3CN)2 in CH2Cl2 at room temper-
ature. Complexes 2a-c and 2a′-c′ exhibit a sharp
singlet in their 31P NMR spectra (Table 1); the large
downfield 31P NMR coordination chemical shifts (ca. 40
ppm) are consistent with the formation of five-mem-
6
54.5 (42.9)
4.36 (8.2)
a δ values in ppm and J values in Hz.
bered palladacycles.9,17,18 The coordination of the pyridyl
group is also indicated by a downfield shift of the H
(13) Delaire, D.; Dransfeld, A.; Nguyen, M. T.; Vanquinckenborne,
L. G. J. Org. Chem. 2000, 65, 2631.
1
(14) (a) Deschamps, B.; Ricard, L.; Mathey, F. Organometallics 2003,
22, 1356. (b) Tran Hyu, N. H.; Mathey, F. Organometallics 1994, 13,
925. (c) Redwine, K. D.; Nelson, J. H. Organometallics 2000, 19, 3054.
(d) Kla¨rner, F.-G.; Oebels, D.; Sheldrick, W. S. Chem. Ber. 1993, 126,
473. (e) Wilson, W. L.; Rahn, J. A.; Alcock, N. W.; Fischer, J.; Frederick,
J. H.; Nelson, J. H. Inorg. Chem. 1994, 33, 109. (f) Wilson, W. L.;
Fischer, J.; Wasylishen, R. E.; Eichele, K.; Catalano, V. J.; Frederick,
J. H.; Nelson, J. H. Inorg. Chem. 1996, 35, 1486.
NMR signal, assigned to the H6 proton of the pyridyl
group (∆δ(H6), 0.9-1.1 ppm). The proposed structures
were confirmed by an X-ray diffraction study performed
on complex 2c′15 (Figure 2a, Table 2). As expected, the
almost square-planar Pd(II) center is bonded to 1c′ via
the P and N atoms, the coordination sphere of the metal
ion being completed by two chloride ligands. The angles
and the bond lengths of the metallacycle are consistent
(15) For a preliminary account, see: Leca, F.; Sauthier, M.; Le
Guennic, B.; Lescop, C.; Toupet, L.; Halet, J.-F.; Re´au, R. Chem.
Commun. 2003, 14, 1774.
(16) Leca, F.; Sauthier, M.; Deborde, V.; Toupet, L.; Re´au, R. Chem.
Eur. J. 2003, 9, 3785.
(17) Hay, C.; Hissler, M.; Fischmeister, C.; Rault-Berthelot, J.;
Toupet, L.; Nuylaszi, L.; Re´au, R. Chem. Eur. J. 2001, 7, 4222.
(18) Fave, C.; Hissler, M.; Se´ne´chal, K.; Ledoux, I.; Ziss, J.; Re´au,
R. Chem. Commun. 2002, 1674.

A New Family of P,N Chelates
Organometallics, Vol. 23, No. 26, 2004 6193
Figure 2. Molecular structure of the Pd(II) complex 2c′ (thermal ellipsoids at 50% probability). Hydrogen atoms have
been omitted for clarity.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for the Pd(II) Complexes 2c′, 3a‚1.5CH2Cl2, 3a′‚CH2Cl2,
and 3c′‚0.5CH2Cl2 (M ) Pd) and the Pt(II) Complex 6‚CH2Cl2 (M ) Pt)
2c′
3a‚1.5CH2Cl2
3a′‚CH2Cl2
3c′‚0.5CH2Cl2
6‚CH2Cl2
M(1)-P(1)
M(1)-N(1)
M(1)-Cl(1)
M(1)-Cl(2)
P(1)-C(1)
C(1)-C(2)
C(2)-C(7)
C(7)-C(8)
C(8)-P(1)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
C(6)-C(7)
C(1)-C(14)
2.2353(11)
2.076(4)
2.3704(11)
2.2874(10)
1.794(4)
1.354(6)
1.483(6)
1.369(6)
1.819(4)
1.504(6)
1.527(7)
1.513(7)
1.528(7)
1.505(6)
1.461(6)
2.2123(10)
2.082(3)
2.3665(11)
2.2950(11)
1.830(4)
1.512(5)
1.470(5)
1.364(5)
1.816(4)
1.345(5)
1.485(6)
1.500(6)
1.535(6)
1.500(5)
1.489(5)
2.1929(11)
2.076(4)
2.3987(12)
2.2858(11)
1.835(4)
1.527(6)
1.462(6)
1.357(6)
1.802(5)
1.340(7)
1.501(7)
1.521(8)
1.529(7)
1.512(6)
1.502(6)
2.1890(12)
2.0173(4)
2.3770(16)
2.2892(16)
1.838(4)
1.522(6)
1.465(7)
1.351(6)
1.803(4)
1.342(7)
1.466(9)
1.538(9)
1.506(8)
1.500(7)
1.510(6)
2.1966(15)
2.062(5)
2.3727(16)
2.2898(19)
1.845(6)
1.498(8)
1.474(9)
1.358(8)
1.822(6)
1.339(9)
1.481(10)
1.505(12)
1.516(10)
1.514(8)
1.519(8)
P(1)-M(1)-N(1)
P(1)-M(1)-Cl(2)
Cl(2)-M(1)-Cl(1)
Cl(1)-M(1)-N(1)
M(1)-P(1)-C(1)
C(1)-P(1)-C(8)
P(1)-C(1)-C(14)
P(1)-C(1)-C(2)
C(2)-C(1)-C(14)
C(1)-C(2)-C(3)
C(1)-C(2)-C(7)
C(3)-C(2)-C(7)
C(2)-C(3)-C(4)
83.46(10)
94.10(4)
89.79(4)
93.29(10)
96.84(14)
92.4(2)
115.7(3)
110.6(3)
131.5(4)
124.8(4)
113.4(4)
121.9(4)
111.9(4)
84.64(9)
90.48(4)
91.05(4)
93.86(9)
100.50(13)
94.20(17)
111.8(3)
103.0(3)
115.4(3)
124.3(4)
112.8(3)
122.8(4)
122.9(4)
84.95(11)
87.53(4)
91.75(4)
95.61(11)
104.10(14)
95.1(2)
111.1(3)
104.4(3)
114.3(4)
124.5(4)
113.7(4)
121.8(4)
122.7(5)
85.05(11)
87.84(5)
91.99(6)
95.05(11)
103.59(15)
94.7(2)
110.7(3)
104.0(3)
112.4(3)
126.3(5)
113.3(4)
120.4(5)
124.1(6)
83.50(14)
94.70(6)
87.85(7)
94.01(14)
103.49(19)
93.1(3)
107.7(4)
104.5(4)
112.5(5)
125.9(7)
112.0(5)
122.1(6)
121.9(7)
with those reported for related Pd(II) complexes bearing
2-(2-pyridyl)phosphole ligands.9,16 Notably, the P atom
of 2c′ has a highly distorted tetrahedral geometry, while
the C(1) carbon atom does not possess a trigonal-planar
geometry, despite its sp2 hybridization (Figure 2b).
These data suggest a significant degree of ring strain
imposed by the formation of the five-membered metal-
lacycle.
Complexes 2b,c′ are stable for weeks in CH2Cl2
solutions at room temperature. In contrast, complexes
2a,a′, which bear a pendant pyridyl group, transform
slowly into the new complexes 3a,a′ (Scheme 1). The
transformation reaches completion after 5 days, and
compounds 3a,a′ were isolated as air-stable yellow
powders in excellent yields (Table 1). High-resolution
mass spectrometry and elemental analysis showed that
3a,a′ are isomers of their corresponding precursors
2a,a′. They each present one 31P{1H} NMR resonance
that is deshielded (∆δ ca. 10 ppm) compared to those of
the corresponding phosphole complexes 2a,a′. In addi-
tion to the signals expected for coordinated and pendant
1
pyridyl groups, the H and 13C NMR spectra of com-
plexes 3a,a′ share some intriguing features. Their 13C-
{1H} NMR spectra show only three signals assignable
to the methylene carbon of the fused saturated car-
bocycle and a doublet due to a PCH moiety (3a, 57.6
ppm, JPC ) 36.6 Hz; 3a′, 48.3 ppm, JPC ) 32.7 Hz). In
1
the H spectra, a multiplet at low field (3a, ddd, 1H,
6.26 ppm; 3a′, m, 1H, 6.26 ppm) indicates the presence
of a CdCH fragment. These data reveal a profound
modification of the phosphorus heterocycle, and the
exact nature of 3a,a′15 was established by X-ray dif-
fraction studies (Figure 3, Table 2). These new deriva-
tives contain an almost square-planar Pd(II) center
linked to two chlorine atoms, a pyridine, and a 2-phos-
pholene ring. Note that the pendant pyridyl group of
the ligand does not interact with the metal center
(Pd(1)-N(2) distance: 3a, 5.598(3) Å; 3a′, 4.444(5) Å).
The existence of the phospholene framework is clearly
indicated by the tetrahedral geometry about the C(1)

6194 Organometallics, Vol. 23, No. 26, 2004
Leca et al.
Figure 4. Molecular structure of the Pd(II) complex 3b
(thermal ellipsoids at 50% probability). Hydrogen atoms,
except for H(1) and H(3), have been omitted for clarity.
Figure 3. Molecular structure of the Pd(II) complex 3a‚
1.5CH2Cl2 (thermal ellipsoids at 50% probability). Hydro-
gen atoms, except for H(1) and H(3), and dichloromethane
molecules have been omitted for clarity.
quantitatively into the corresponding 2-pyridyl-2-phos-
pholene complexes 3b,b′ and 3c,c′ after 3 days (Scheme
1). In the presence of a stoichiometric amount of
pyridine, the reaction is extremely slow. For example,
according to 31P NMR spectroscopy, only 20% of complex
2b was converted after 2 weeks. In the presence of Et3N
and 1,8-diazabycyclo[5.4.0]undec-7-ene complicated mix-
tures of products were obtained, while with (-)-
sparteine or (-)-cinchonidine no reaction was observed.
According to multinuclear NMR spectroscopy, these
new complexes 3b,b′ and 3c,c′ were formed as only one
of the two possible diastereoisomers. They exhibited
NMR spectroscopic data that are very similar to those
recorded for their related analogues 3a,a′ (Table 1),
strongly supporting the proposed structures. Of par-
ticular interest, the 2JPH values are very similar within
a given series (R2 ) Ph, Cy), suggesting that, again, the
H atom on C(1) and the P substituent adopt a mutually
cis arrangement. To confirm these hypotheses, com-
plexes 3b,c′15 were subject to X-ray diffraction studies.
As expected, 3b,c′ are square-planar Pd(II) complexes
bearing 2-(2-pyridyl)-2-phospholene ligands and the H
atom linked to the C(1) center and the P substituent
adopt a mutually cis configuration (Figure 4, Table 2).
The structure of 3b gave high weighted values of R (see
the Experimental Section), which precludes a discussion
of the metric data. The metric parameters of 3c′
compare well with those of the related complexes 3a,a′
(Table 2). Note that the C(1)-C(2) (1.522(6) Å) and
C(2)-C(3) (1.342(7) Å) distances are fully consistent
with a 3-methylene-2-phospholene framework and that
the C(1) carbon atom has a tetrahedral geometry with
bond angles ranging from 104.0(3) to 112.4(3)°.
carbon atom and the C(1)-C(2) (3a, 1.512(5) Å; 3a′,
1.527(6) Å) and C(7)-C(8) (3a, 1.364(5) Å; 3a′, 1.357(6)
Å) bond distances, which are typical of single and double
carbon-carbon links, respectively. The two endocyclic
P-C distances (3a, 1.830(4) and 1.816(4) Å; 3a′, 1.835(4)
and 1.802(5) Å) are characteristic for single bonds. It is
also noteworthy that the C(3) carbon atoms have a
planar geometry and that the C(2)-C(3) distances (3a,
1.345(5) Å; 3a′, 1.340(7) Å) are consistent with double
bonds. Clearly, the fused carbocycles of 3a,a′ are now
cyclohexene fragments. These solid-state structural data
are in full agreement with the NMR spectroscopic data
recorded in solution.
To the best of our knowledge, derivatives 3a,a′ are
the first P,N chelates to incorporate a 2-phospholene
moiety. Furthermore, their syntheses via isomerization
of the corresponding 2-(2-pyridyl)phospholes is a very
attractive route for several reasons. First, the phosphole
precursors are readily available and their substitution
pattern can be easily varied.9,17 Second, the isomeriza-
tion is not sensitive to the nature of the P substituent,
allowing the stereoelectronic properties of the P donor
to be tuned. Finally, the [1,3]-hydrogen shift leading to
3a,a′ creates a new stereogenic center (the C(1) carbon
atom), and the fact that only one diastereoisomer out
of the two possible ones is detected by NMR spectros-
copy shows that this process is stereoselective. The solid-
state studies revealed that the H atom linked to the C(1)
atom and the P substituent are in a mutual cis config-
uration (Figure 3). It was thus of interest to investigate
the scope of this synthetic method with the aim of
obtaining a family of 2-(2-pyridyl)-2-phospholene ligands.
Complexes 2b,b′ and 2c,c′ bearing phenyl or 2-thienyl
R1 substituents (Scheme 1) are stable for days in CH2Cl2
and THF solutions at reflux. These results constitute a
serious limitation to this new synthetic methodology,
since the isomerization process seems dependent on the
structure of the ligand. The sole difference between
derivatives that undergo (2a,a′) and those that do not
undergo (2b,b′ and 2c,c′) the isomerization is the
absence of a pendant pyridyl group in the latter (Scheme
1). This observation prompted us to investigate the fate
of complexes 2b,b′ and 2c,c′ in the presence of pyridine.
Indeed, in refluxing CH2Cl2 solutions containing an
excess of pyridine, 2b,b′ and 2c,c′ were transformed
The isomerization of 2-pyridylphospholes into 2-pyr-
idyl-2-phospholenes in the coordination sphere of Pd(II)
complexes appears to be a general and powerful syn-
thetic methodology. It is noteworthy that free 2-(2-
pyridyl)phospholes 1a-c and 1a′-c′ do not isomerize
into the corresponding phospholenes in CH2Cl2 and THF
solutions containing pyridine at reflux. This result
raises questions about the crucial role played by the
metal and prompted us to study the isomerization
process by DFT calculations for one particular series.
This theoretical work15 revealed that the 2-pyridylphos-
phole 1a′ is more stable than the 2-pyridyl-2-phos-
pholene 2a′ but that the (2-pyridylphosphole)palla-

A New Family of P,N Chelates
Organometallics, Vol. 23, No. 26, 2004 6195
Figure 5. DFT-calculated relative energies of isomers 1a′ and 4a′ and of the corresponding Pd(II) complexes 2a′ and 3a′.
Scheme 2
Scheme 3
palladium(II) complexes with a cis configuration of the
P substituent and the H atom on C(1) are more stable
than their trans stereoisomers.15 Thus, the Pd(II) center
plays a double role via the formation of a five-membered
metallacycle: it reverses the relative stability of 2-pyr-
idylphospholes vs 2-pyridyl-2-phospholenes, allowing a
thermodynamically controlled isomerization, and im-
poses a stereospecific process.
dium(II) complex 2a′ is less stable than the (2-pyridyl-
2-phospholene)palladium(II) complex 3a′ (Figure 5). In
other words, coordination to a square-planar d8 metal
center reverses the thermodynamic stability of the two
P,N isomers. These calculations agree with the experi-
mental results, which show that the isomerization can
take place only in the coordination sphere of the metal,
the direct isomerization of phosphole 1a′ into phos-
pholene being a thermodynamically unfavorable process
(Figure 5).
Two other examples of isomerization of 3-methylphos-
pholes into 3-methylene-2-phospholenes have already
been reported in the literature. The first involves
metalation of 3,4-dimethylphosphole (DMPP)-borane
adducts, which leads to an intermediate allylic anion,
followed by hydrolysis (Scheme 3).14b The second in-
volves the thermolysis of Ru(II)-DMPP complexes and
proceeds in low yield (ca. 3.9%).14c It is also noteworthy
that the thermal dimerization of 3,4-dimethylphospholes
within the coordination sphere of Pt(II) and Pd(II) to
form exomethylenephospholenes is known.14e,f Our
method offers several advantages compared to these
examples. The reaction conditions are very mild (45 °C,
presence of a weak base), the yields are almost quan-
titative, irrespective of the phosphole substitution pat-
tern, and the purification procedure is extremely simple.
Furthermore, this process is stereoselective. The main
drawback of our method is the requirement for pal-
ladium, which is a rather expensive metal. We thus
investigated two ways to circumvent this problem. The
first is the use of cheaper metals. However, in CH2Cl2
solutions containing pyridine, no isomerization was
observed in the presence of ZnCl2, CuCl, or CuCl2. The
second approach is to perform the isomerization in a
catalytic manner, something that could be favored by
This behavior can be explained tentatively by com-
paring the solid-state structures of Pd(II) complexes
featuring either a 2-pyridylphosphole or a 2-pyridyl-2-
phospholene ligand (Scheme 1). As already stated, the
distorted geometry of the P(1) and C(1) atoms of
coordinated 2-pyridylphospholes revealed a strain, due
to the formation of the five-membered metallacycle
(Figure 2). In contrast, in the Pd(II) phospholene
complexes, the P(1) atom exhibits a geometry close to
that of an ideal tetrahedron, as a consequence of the
change in hybridization of the C(1) center (Figures 3
and 4). These solid-state data suggest that the strain
associated with the metallacycle in phosphole complexes
can account for their lower stability compared to that
of the phospholene complexes. To reinforce this hypoth-
esis, we investigated the behavior of ligand 4a (vide
infra) possessing two possible chelating moieties (for-
mally a “2-pyridylphospholane” and a “2-pyridylphos-
phole”) with (CH3CN)2PdCl2 (Scheme 2). This reaction
led exclusively to the formation of complex 3a. Further-
more, according to 31P NMR spectroscopy, heating 3a
in THF at reflux revealed no fluxional behavior. This
experiment clearly shows that coordination of square-
planar d8 metal centers is thermodynamically more
favored with 2-pyridyl-2-phospholenes than with 2-pyr-
idylphospholes. It is noteworthy that the DFT calcula-
tions also showed that the (2-(2-pyridyl)phospholene)-
the hemilabile behavior of P,N donors.1 According to 31
P
NMR spectroscopy, addition of 10% of (CH3CN)2PdCl2
to a CH2Cl2 solution of phosphole 1a afforded a mixture
of 1a (90%) and complex 2a (10%). After 3 days at room
temperature, this solution contained 1a (90%) and the

6196 Organometallics, Vol. 23, No. 26, 2004
Leca et al.
Scheme 4
the isomerization is not a catalytic process with plati-
num. This feature, also observed with palladium, can
be explained by the fact that 2-pyridyl-2-phospholenes
are more tightly bonded to the metal centers than the
corresponding 2-pyridylphospholes, preventing the ligand
exchange step required for a catalytic process.
The next step toward obtaining free 2-(2-pyridyl)-2-
phospholenes was their release from the Pd(II) centers.
This was easily achieved by addition of 1 equiv of 1,2-
(diphenylphosphino)ethane (dppe) to complexes 3a-c
and 3a′-c′ (Scheme 1). The phospholenes 4a-c and
4a′-c were isolated as air-sensitive powders in excellent
yields (Table 1). Their multinuclear NMR spectra
showed that they are obtained as single diastereisomers,
indicating that the decoordination step proceeds without
racemization of the P center. For example, their 31P{1H}
NMR spectra show a single resonance in the range
expected for P-aryl and P-alkyl phospholenes (Table
1).10,14b The 1H and 13C NMR data are typical and
support the proposed structures. In the 13C NMR
spectra, three singlets for the methylene fragments of
the fused carbocycle are observed and a doublet char-
acteristic of a PCH moiety is observed (Table 1). In all
1
cases, the H NMR spectra exhibit a broad resonance
Figure 6. Molecular structure of the Pt(II) complex
6‚CH2Cl2 (thermal ellipsoids at 50% probability). Hydrogen
atoms, except for H(1) and H(3), and dichloromethane
molecules have been omitted for clarity.
corresponding to the CdCH moiety, with chemical shifts
ranging from 5.52 to 5.62 ppm.
One further key point was to estimate the inversion
barrier at phosphorus for these new types of P,N
ligands. It is reasonable to assume that the stereogenic
C(1) center of phospholenes 4a-c and 4a′-c will not
racemize upon heating in neutral media. Thus, inver-
sion of the P atom should give a new diastereisomer
detectable by NMR. We thus investigated the thermal
behavior in [D8]toluene solutions of 1-phenyl-2-pyridyl-
2-phospholenes 4a-c, featuring respectively a pyridyl,
a phenyl, and a thienyl substituent on the P heterocycle,
and 1-cyclohexyl-2-pyridyl-2-phospholene (4b′). The
samples were gradually heated from 40 to 110 °C, with
phospholene complex 3a (10%) (Scheme 1). This ratio
did not change further upon heating or increasing the
reaction time, clearly showing that the isomerization
is a stoichiometric process with respect to palladium.
Platinum was then investigated as a potential catalyst.
First, it was necessary to establish that 2-pyridylphos-
pholes can be transformed into 2-pyridyl-2-phospholenes
in the coordination sphere of d8-Pt(II) complexes. Phos-
phole 1c was selected for this study; it reacts rapidly
with PtCl2(CH3CN)2 in CH2Cl2 at room temperature to
give complex 5 in 79% yield (Scheme 4). Elemental
analysis and high-resolution mass spectrometry support
the proposed structure. The downfield 31P NMR coor-
dination chemical shift (ca. 25 ppm) is less pronounced
than in the Pd(II) series. However, the coordination of
both the P and the N atoms is clear from the large JPPt
coupling constant (3704.0 Hz) and the low-field chemical
shift of the 1H NMR signal of the H6 proton of the
pyridyl group (δ 9.88 ppm). Complex 5 could be isomer-
ized quantitatively into 6 in a CH2Cl2 solution contain-
ing pyridine at reflux (Scheme 4). The allylic moiety
could be identified by the presence of a doublet at 4.36
ppm (JPH ) 8.2 Hz, PCH) and from a broad resonance
an isotherm of 1 h every 10 °C, and 31P and H NMR
1
spectra were recorded before and after each temperature
ramp. Up to 90 °C no new NMR signals were detected.
This result fits with previous studies that have estab-
lished a high barrier to inversion for phospholenes10,11a
and shows that P,N chelates 4a-c and 4a′-c are
promising P-chiral ligands for homogeneous catalysis.
Very interestingly, at 100 °C, derivatives 4a-c and 4a′
cleanly isomerized into the corresponding phospholes,
as illustrated in Figure 7 for phospholene 4c. This
process fits nicely with the theoretical data, revealing
that free 2-pyridyl-2-phospholenes are thermodynami-
cally less stable than their phosphole isomers.
1
at 6.17 ppm (CdCH) in the H spectrum. These data,
as well as the other 1H and 13C NMR data, are
consistent with the proposed structure. The cis arrange-
ment of the P substituent and the H atom of the PCH
moiety was confirmed by an X-ray diffraction study
(Figure 6). The bond lengths and angles of the Pt(II)
complex 6 are typical and are similar to those of the
related Pd(II) complex 3c′ (Table 2). Thus, the base-
promoted stereoselective isomerization of 2-pyridylphos-
pholes into 2-pyridyl-2-phospholenes in the coordination
sphere of square-planar d8 metal centers appears to be
a general process. Experiments conducted with a phos-
phole 1c/PtCl2(CH3CN)2 ratio less than 1 revealed that
Conclusion
We have described a general and straightforward
route to a new family of P,N chelates featuring a
chirogenic P center. This route involves the stereose-
lective isomerization of Pd(II)-coordinated 2-pyridylphos-
phole ligands into their corresponding 2-pyridyl-2-
phospholene isomers in the presence of pyridine. The
role of the metal is to render this isomerization ther-
modynamically feasible, while the role of the pyridine
is very probably to favor the 1,3-shift via the formation

A New Family of P,N Chelates
Organometallics, Vol. 23, No. 26, 2004 6197
) 15.1 Hz; PCdCâ), 151.8 (d, JPC ) 10.7 Hz; PCdCâ), 153.7 (s;
C6 Py); the C2 Py, ipso-Ph and PCR carbon resonances were
not observed. 31P{1H} NMR (81.014 MHz, CDCl3): δ +56.2.
HR-MS (FAB-mNBA): m/z 520.0209 [M - Cl]+; calcd for
C25H22NPPdCl2 520.0213. Anal. Calcd for C25H22NPPdCl2
(544.753): C, 55.12; H, 4.07; N, 2.57. Found: C, 55.02; H, 4.00;
N, 2.49.
[1-cyclohexyl-2-(2-pyridyl)-5-phenylphosphole]PdCl2
(2b′). Following the procedure described for compound 2b,
reaction of 1-cyclohexyl-2-(2-pyridyl)-5-phenylphosphole (1b′;
0.35 g, 0.90 mmol) and (CH3CN)2PdCl2 (0.23 g, 0.90 mmol)
afforded 2b′ as an air-stable yellow solid (yield 0.45 g, 0.82
mmol, 92%). 1H NMR (200 MHz, CDCl3): δ 1.01-1.19 (m, 3H;
CH2), 1.51-1.87 (m, 12H; CH2), 2.65-2.83 (m, 3H; CH2), 3.12
(m, 1H; CH2), 7.21-7.43 (m, 4H; p-H Ph, m-H Ph, and H5 Py),
7.67 (d, 3JHH ) 8.2 Hz, 1H; H3 Py), 7.85 (d, 3JHH ) 7.2 Hz, 2H;
o-H Ph), 8.05 (dd, JHH ) 8.2 Hz, JHH ) 6.6 Hz, 1H; H4 Py),
9.63 (d, 3JHH ) 5.5 Hz, 1H; H6 Py). 13C{1H} NMR (50.323 MHz,
CDCl3): δ 22.2 (s; dCCH2CH2), 22.7 (s; dCCH2CH2), 25.7 (s;
dCCH2), 26.7 (d. JPC ) 7.2 Hz; CH2), 26.9 (d, JPC ) 9.6 Hz;
CH2), 27.4 (d, JPC ) 8.37 Hz; CH2), 28.1 (d, JPC ) 3.9 Hz; CH2),
3
3
Figure 7. Expansions of the 81.0 MHz 31P{1H} spectra
following isomerization of 2-pyridylphospholene 4c into
2-pyridylphosphole 1c at 100 °C: (a) after 2 h; (b) after 12
h.
29.2 (d, JPC ) 9.6 Hz; CH2), 30.0 (s; dCCH2), 38.5 (d, JPC
)
21.7 Hz; PCH), 123.2 (d, JPC ) 10.8 Hz; C3 Py), 123.8 (s; C5
Py), 128.9 (s; m-C Ph), 129.2 (s; p-C Ph), 131.2 (d, JPC ) 10.8
Hz; o-C Ph), 139.9 (s; C4 Py), 149.8 (d, JPC ) 32.6 Hz; PCRdC),
151.4 (d, JPC ) 10.7 Hz; PCdCâ), 153.0 (d, JPC ) 14.8 Hz; C2
Py), 153.6 (s; C6 Py), one Câ, one CR, and the ipso-C Ph
resonances were not observed. 31P{1H} NMR (81.014 MHz,
CDCl3): δ +72.4. Anal. Calcd for C25H28NPPdCl2 (550.801): C,
54.52; H, 5.12; N, 2.54. Found: C, 55.20; H, 5.01; N, 2.61.
[1-phenyl-2-(2-pyridyl)-5-(2-thienyl)phosphole]PdCl2
(2c). Following the procedure described for compound 2b, the
reaction of 1-phenyl-2-(2-pyridyl)-5-(2-thienyl)phosphole (1c;
0.33 g, 0.90 mmol) and (CH3CN)2PdCl2 (0.23 g, 0.90 mmol)
afforded 2c as an air-stable red solid (yield 0.48 g, 0.86 mmol,
96%). 1H NMR (300 MHz, CD2Cl2): δ 1.72-2.10 (m, 4H; d
CCH2CH2), 2.80 (m, 1H; dCCH2), 2.95 (m, 1H; dCCH2), 3.15
(m, 2H; dCCH2), 7.08 (dd, 3JHH ) 5.1 and 7.7 Hz; 1H; H5 Py),
7.32-7.64 (m, 6H; H arom), 7.80-8.04 (m, 4H; H arom), 9.61
(dd broad, 3JH-H ) 5.1 Hz, 5JHH ) 0.9 Hz, 1H; H6 Py). 13C{1H}
NMR (75.469 MHz, CD2Cl2): δ 21.9 (s; dCCH2CH2), 22.8 (s;
of an allylic anion. The resolution of racemic 2-pyridyl-
2-phospholene derivatives is under intensive investiga-
tion.
Experimental Section
General Remarks. All experiments were performed under
an atmosphere of dry argon using standard Schlenk tech-
niques. Commercially available reagents were used as received
without further purification. Solvents were freshly distilled
under argon from sodium/benzophenone (tetrahydrofuran,
diethyl ether) or from phosphorus pentoxide (pentane, dichlo-
romethane, acetonitrile). Complexes 2a,a′ were prepared ac-
cording to ref 16. 1H, 13C, and 31P NMR spectra were recorded
1
on Bruker AM300, DPX200, and ARX400 spectrometers. H
and 13C NMR chemical shifts are reported in parts per million
(ppm) relative to Me4Si as external standard. 31P NMR
downfield chemical shifts were expressed with a positive sign,
in ppm, relative to external 85% H3PO4. Assignment of carbon
chemical shifts was based on HMBC and HMQC experiments.
High-resolution mass spectra were obtained on a Varian MAT
311 or ZabSpec TOF Micromass instrument at the CRMPO,
University of Rennes. Elemental analyses were performed by
the CRMPO or the Center de Microanalyze du CNRS at
Vernaison, France.
dCCH2CH2), 28.4 (d, JPC ) 9.2 Hz; dCCH2), 30.2 (d, JPC
)
10.4 Hz; dCCH2), 123.9 (s; C5 Py), 124.0 (d, JPC ) 11.0 Hz; C3
Py), 125.0 (d, JPC ) 48.8 Hz; ipso-Ph), 128.0 (s; C4 Thio or C5
Thio), 129.3 (s; C4 or C5 Thio), 129.7 (d, JPC ) 12.2 Hz; m-Ph),
132.3 (d, JPC ) 53.7 Hz; PCRdC), 133.9 (d, JPC ) 50.6 Hz; PCRd
C), 133.4 (d, JPC ) 2.4 Hz; C3 Thio), 133.9 (d, JPC ) 12.8 Hz;
o-Ph), 134.5 (d, JP-C ) 3.6 Hz; p-Ph), 135.5 (d, JPC ) 19.5 Hz;
C2 Thio), 140.0 (s; C4 Py), 148.7 (d, JPC ) 14.7 Hz, PCdCâ),
151.9 (d, JPC ) 11.0 Hz; C2 Py), 152.5 (d, JPC ) 20.0 Hz; PCd
Câ), 153.6 (s; C6 Py). 31P{1H} NMR (81.014 MHz, CD2Cl2): δ
+59.1. HR-MS (FAB-mNBA): m/z 513.9771 [M - Cl]+, calcd
for C23H20NSPPdCl2 513.9768. Anal. Calcd for C23H20NSP-
PdCl2: C, 50.16; H, 3.66; N, 2.54. Found: C, 49.98; H, 3.56;
N, 2.46.
[1,5-diphenyl-2-(2-pyridyl)phosphole]PdCl2 (2b). A so-
lution of the 1-phenylphosphole 1b (0.33 g, 0.90 mmol) in
CH2Cl2 (5 mL) was added, at room temperature, to a solution
of (CH3CN)2PdCl2 (0.23 g, 0.90 mmol) in CH2Cl2 (10 mL). The
solution was stirred for 1 h at room temperature, and the
volatile materials were removed under vacuum. The residue
was washed with diethyl ether (3 × 10 mL) and dried under
vacuum. Complex 2b was isolated as an air-stable yellow solid
(yield 0.43 g, 0.80 mmol, 89%). 1H NMR (200 MHz, CDCl3): δ
1.40-1.80 (m, 4H; dCCH2CH2), 2.50-2.75 (m, 2H; dCCH2),
3.02-3.20 (m, 2H; dCCH2), 7.21-7.43 (m, 8H; H arom and
H5 Py), 7.51-7.62 (m, 3H; H arom), 7.73-7.78 (d broad, 1H;
[1-cyclohexyl-2-(2-pyridyl)-5-(2-thienyl)phosphole]-
PdCl2 (2c′), Following the procedure described for compound
2b, reaction of 1-cyclohexyl-2-(2-pyridyl)-5-(2-thienyl)phosphole
(1c′; 0.34 g, 0.90 mmol) and (CH3CN)2PdCl2 (0.23 g, 0.90 mmol)
afforded 2c′ as an air-stable red solid (yield 0.45 g, 0.81 mmol,
90%). 1H NMR (200 MHz, CDCl3): δ 0.80-1.95 (m, 14H; CH2),
2.60-3.01 (m, 5H; CH2, CH), 7.25 (dd, 3JHH ) 3.8 and 5.0 Hz,
1H; H4 Thio), 7.37 (ddd, 3JHH ) 6.0 and 7.6 Hz, 4JHH ) 1.4 Hz,
3
4
3
4
H3 Py), 7.86 (ddd, JHH ) 7.7 and 7.8 Hz, JHH ) 1.6 Hz, 1H;
1H; H5 Py), 7.57 (dd, JH-H ) 5.0 Hz, JH-H ) 2.8 Hz, 1H; H3
H4 Py), 9.56 (d, JH-H ) 6.0 Hz, 1H; H6 Py). 13C{1H} NMR
Thio), 7.62 (d broad, 3JHH ) 7.4 Hz, 1H; H3 Py), 8.04 (ddd, 3JHH
3
4
(50.323 MHz, CDCl3): δ 21.9 (s; dCCH2CH2), 22.5 (s; d
CCH2CH2), 27.2 (d, JPC ) 9.4 Hz; dCCH2), 29.1 (d, JPC ) 10.5
Hz; dCCH2), 123.1 (d, JPC ) 10.2 Hz; C3 Py) 123.5 (s; C5 Py),
128.6 (s; m-Ph), 128.8 (s; p-Ph), 129.2 (d, JPC ) 11.7 Hz, o-Ph),
130.7 (d; JPC ) 4.7 Hz, m-PPh), 132.7 (d, JPC ) 2.3 Hz; p-PPh),
133.5 (d, JPC ) 11.7 Hz; o-PPh), 139.3 (s; C4 Py), 146.5 (d, JPC
) 7.4 and 7.6 Hz, JHH ) 1.6 Hz, 1H; H4 Py), 8.34 (d broad,
3JHH ) 3.8 Hz, 1H; H5 Thio), 9.59 (d broad, 3JHH ) 6.0 Hz, 1H;
H6 Py). 13C{1H} NMR (50.323 MHz, CDCl3): δ 21.9 (s;
dCCH2CH2), 21.8 (s; dCCH2CH2), 25.7 (d, JPC ) 1.5 Hz; CH2),
26.8 (d, JPC ) 11.7 Hz; CH2), 27.3 (d, JPC ) 7.3 Hz; CH2), 27.3
(d, JPC ) 15.5 Hz; CH2), 28.3 (d, JPC ) 7.9 Hz; dCCH2), 29.6

6198 Organometallics, Vol. 23, No. 26, 2004
Leca et al.
(d, JPC ) 10.3 Hz; dCCH2), 30.7 (d, JPC ) 2.5 Hz; CH2), 39.6
(d, 1JPC ) 20.4 Hz; CH), 123.2 (d, 3JPC ) 11.0 Hz; C3 Py), 123.8
(s; C5 Py), 128.6 (s; C4 or C5 Thio), 129.5 (s; C4 or C5 Thio),
130.8 (d, JPC ) 48.6 Hz, PCRdC), 130.9 (d, JPC ) 45.3 Hz; PCRd
C), 135.2 (d, JPC ) 3.2 Hz; C3 Thio), 135.6 (d, JPC ) 19.5 Hz;
C2 Thio), 140.2 (s; C4 Py), 148.6 (d, JPC ) 13.4 Hz; PCdCâ),
152.5 (d, JPC ) 9.5 Hz, PCdCâ), 153.3 (d, JPC ) 19.5 Hz, C2
Py), 153.6 (s; C6 Py). 31P{1H} NMR (81.014 MHz, CDCl3): δ
+69.0. HR-MS (FAB-mNBA): m/z 520.0258 [M - Cl]+, calcd
for C23H26NPSPdCl2 520.0253. Anal. Calcd for C23H26NPSPdCl2
(556.827): C, 49.61; H, 4.71; N, 2.52. Found: C, 49.31; H, 4.82;
N, 2.61.
under vacuum. Complex 3b was isolated as an air-stable
yellow solid (yield 0.44 g, 0.82 mmol, 91%). 1H NMR (200 MHz,
CD2Cl2): δ 1.71-1.87 (m, 2H; dCCH2CH2), 2.23-2.51 (m, 2H;
2
CH2), 2.55-2.73 (m, 2H; CH2), 4.61 (d, JPC ) 13.0 Hz, 1H;
PCH), 6.15 (t broad, 1H; CdCH), 7.28-7.62 (m, 8H; H arom),
3
7.94-8.10 (m, 4H; H arom), 8.80 (d, JHH ) 6.6 Hz, 1H; H4
Py), 9.86 (d, 3JHH ) 6.5 Hz, 1H; H6 Py). 13C{1H} NMR (50.323
MHz, CD2Cl2): δ 22.1 (s; dCCH2CH2), 26.1 (s; CH2), 28.2 (s;
CH2), 53.7 (d, JPC ) 36.4 Hz; PCH), 124.9 (s; C5 Py), 125.4 (s;
2
C3 Py), 128.5 (s; m-Ph), 128.7 (s; p-Ph), 129.4 (d, JPC ) 7.1
Hz; o-Ph), 130.6 (d, JPC ) 3.1 Hz; m-PPh), 132.6 (d, JPC ) 6.1
Hz; CdCH), 133.3 (s; p-PPh), 134.4 (d, 2JPC ) 12.1 Hz; o-PPh),
139.9 (s; C4 Py), 155.0 (s; C6 Py), 156.0 (s broad, C2 Py); the
PCRdCâ and ipso-Ph carbon resonances were not observed.
31P{1H} NMR (81.014 MHz, CDCl3): δ +69.8. Anal. Calcd for
C25H22NPPdCl2 (544.753) : C, 55.12; H, 4.07; N, 2.57. Found:
C, 55.13; H, 4.10; N, 2.59.
[1-phenyl-2,5-bis(2-pyridyl)phosphol-2-ene]PdCl2 (3a).
A solution of complex 2a (0.49 g, 0.90 mmol) in CH2Cl2 (10
mL) was heated at 45 °C for 3 days. The solvent was removed,
and the residue was washed with diethyl ether (3 × 10 mL)
and dried under vacuum. Complex 3a was obtained as an air-
stable yellow solid (yield 0.45 g, 0.82 mmol, 91%). 1H NMR
(200 MHz, CD2Cl2): δ 1.90 (m, 2H; dCCH2CH2), 2.30 (m, 2H;
[1-cyclohexyl-2-(2-pyridyl)-5-phenylphosphol-2-ene]-
PdCl2 (3b′). Following the procedure for complex 3b, the
reaction of 2b′ (0.43 g, 0.80 mmol) afforded 3b′ as an air-stable
yellow solid (yield 0.40 g, 0.72 mmol, 91%). 1H NMR (200 MHz,
CD2Cl2): δ 1.36-1.52 (m, 2H; CH2), 1.56-1.92 (m, 10H; CH2),
2.21-2.56 (m, 3H; CH2 and CH), 3.01 (m, 2H; CH2), 4.60 (d,
2JPH ) 6.2 Hz, 1H; P-CH), 6.25 (m, 1H; CH2CH), 7.32-7.54
(m, 4H; H arom), 7.83 (d, 3JHH ) 7.4 Hz, 2H; o-H Ph), 7.96 (d,
3JHH ) 6.4 Hz, 1H; H3 Py), 8.80 (dd, 3JHH ) 6.6 Hz, 3JHH ) 6.4
2
dCCH2CH2), 2.90 (m, 2H; dCCH2), 4.66 (dd, JPH ) 11.9 Hz,
3
3JHH ) 1.6 Hz, 1H; PCH), 6.26 (ddd, JHH ) 4.2 and 5.8 Hz,
3
4JHH ) 1.6 Hz, 1H; CdCH), 7.20 (dd, JHH ) 4.9 and 7.8 Hz,
1H; H5 Py), 7.33-7.57 (m, 4H; H5 Py, m-Ph, p-Ph), 7.66 (m,
3
2H; H3 and H4 Py), 7.82 (d, JHH ) 8.0 Hz, 1H; H3 Py), 7.80
(dd, 3JHH ) 7.8 Hz, 4JHH ) 8.0 Hz, 1H; H4 Py), 8.09 (ddd, 3JHH
4
3
) 8.2 Hz, JHH ) 1.5 Hz, JPH ) 12.1 Hz, 2H; o-Ph), 8.54 (d,
3JHH ) 4.9 Hz, 1H; H6 Py), 9.77 (d, 3JHH ) 5.8 Hz, 1H; H6 Py).
13C{1H} NMR (75.469 MHz, CD2Cl2): δ 22.1 (s; dCCH2CH2),
3
Hz, 1H; H4 Py), 9.79 (d, JHH ) 5.2 Hz; H6 Py). 13C{1H} NMR
(50.323 MHz, CD2Cl2): δ 20.9 (s; dCCH2CH2), 25.0 (s; CH2),
25.5 (s; CH2), 25.8 (d, JPC ) 11.1 Hz; CH2), 26.0 (d, JPC ) 5.12
Hz; CH2), 26.6 (d, JPC ) 9.3 Hz; CH2), 28.1 (s; CdCCH2), 28.9
(s; dCCH2), 34.7 (d, JPC ) 25.1 Hz; PCH), 47.7 (d, JPC ) 32.3
Hz; PCH), 123.2 (d, JPC ) 11.9 Hz; C3 Py), 124.2 (s; C5 Py),
127.5 (s; m-C Ph), 129.3 (s; p-C Ph), 129.9 (d, JPC ) 3.8 Hz;
3
26.2 (s; dCCH2), 28.6 (d, JPC ) 10.4 Hz; CdCCH2), 57.6 (d,
JPC ) 36.6 Hz; PCH), 123.3 (s; C5 Py), 124.8 (d, JPC ) 12.8 Hz;
C3 Py), 124.9 (s; C5 Py), 126.9 (s broad; C3 Py), 127.0 (d, JPC
)
51.0 Hz; PCRdC), 129.4 (d, JPC ) 12.2 Hz; m-Ph), 133.1 (d,
JPC ) 3.1 Hz; p-Ph), 134.4 (d, JPC ) 12.8 Hz; o-Ph), 134.9 (d,
JPC ) 4.3 Hz; CdCH), 137.0 (s; C4 Py), 138.7 (d, JPC ) 7.9 Hz;
PCdCâ), 140.0 (s; C4 Py), 149.1 (s; C6 Py), 152.2 (d, JPC ) 14.6
2
2
CH2CH), 130.7 (d, JPC ) 20.1 Hz; PCRdC), 130.8 (d, JPC
)
5.0 Hz; o-C Ph), 131.9 (d, 1JPC ) 11.5 Hz; PCdCâ), 138.6 (s; C4
2
2
Hz; PC-Câ), 154.1 (s; C6 Py), 157.7 (d, JPC ) 9.8 Hz; C2 Py),
Py), 151.9 (d, JPC ) 10.0 Hz; PC-Câ), 152.5 (s; C6 Py), 163.1
163.0 (d, 2JPC ) 7.9 Hz; C2 Py); the ipso-Ph resonance was not
observed. 31P{1H} NMR (81.014 MHz, CD2Cl2): δ +67.3; HR-
MS (FAB-mNBA): m/z 511.0168 [M - Cl]+, calcd for C24H21N2-
PCl2Pd 511.0468. Anal. Calcd for C24H21N2PCl2Pd (545.74): C,
52.82; H, 3.88; N, 5.13. Found: C, 52.66; H, 3.65; N, 5.22.
[1-cyclohexyl-2,5-bis(2-pyridyl)phosphol-2-ene]PdCl2
(3a′). Following the procedure for complex 3a, the reaction of
2a′ (0.51 g, 0.90 mmol) afforded 3a′ as an air-stable yellow
solid (yield 0.48 g, 0.84 mmol, 94%). 1H NMR (200 MHz,
CD2Cl2): δ 0.82-1.95 (m, 8H; CH2), 2.30 (m, 4H; CH2), 2.60-
(d, JPC ) 6.9 Hz; C2 Py); the ipso-C Ph resonance was not
2
observed. 31P{1H} NMR (81.014 MHz, CDCl3): δ +84.3. Anal.
Calcd for C25H28NPPdCl2 (550.801) : C, 54.52; H, 5.12; N, 2.54.
Found: C, 54.32; H, 5.05; N, 2.59.
[1-phenyl-2-(2-pyridyl)-5-(2-thienyl)phosphol-2-ene]-
PdCl2 (3c). Following the procedure for complex 3b, the
reaction of 2c (0.49 g, 0.90 mmol) afforded 3c as an air-stable
yellow solid (yield 0.43 g, 0.79 mmol, 88%). 1H NMR (200 MHz,
CD2Cl2): δ 1.85 (m, 2H; dCCH2CH2), 2.25 (m, 2H; Cd
2
CCH2CH2), 2.92 (m, 2H; CH2), 4.56 (d, JPH ) 10.8 Hz, 1H;
2
3.15 (m, 5H; CH2, CH Cy), 4.59 (d broad, JPH ) 7.3 Hz, 1H;
PCH), 6.26 (s broad, 1H; CdCH), 6.92 (dd, 3JHH ) 4.2 and 4.5
Hz, 1H; H5 Py), 7.31-7.60 (m, 6H; H arom), 7.76-8.1 (m, 4H;
3
PCH), 6.26 (m, 1H; CdCH), 7.23 (dd, JHH ) 4.9 and 7.6 Hz,
1H; H5 Py), 7.36 (dd, 3JHH ) 5.4 and 7.6 Hz, 1H; H5 Py), 7.52-
H arom), 9.79 (d, JH-H ) 4.5 Hz, 1H; H6 Py). 13C{1H} NMR
3
3
7.80 (m, 3H; H3 Py, H4 Py), 7.79 (dd, JHH ) 7.6 and 7.6 Hz,
(50.323 MHz, CD2Cl2): δ 21.5 (s; dCCH2CH2), 25.4 (s; CH2),
3
3
1H; H4 Py), 8.59 (s broad, 1H; H6 Py), 9.40 (d broad, JHH
)
28.2 (d, JPC ) 10.6 Hz; CH2), 57.2 (d, JPC ) 36.6 Hz; PCH),
5.4 Hz, 1H; H6 Py). 13C{1H} NMR (75.469 MHz, CD2Cl2): δ
21.9 (s; dCCH2CH2), 26.0 (s; CH2), 26.2 (s; CH2), 26.8 (d, JPC
122.0 (d, JPC ) 47.8 Hz; ipso-Ph), 124.5 (s; C5 Py), 124.6 (d,
JPC ) 12.9 Hz; C3 Py), 126.0 (d, JPC ) 49.9 Hz, PCRdC), 127.2
(s; C4 or C5 Thio), 127.6 (s; C4 or C5 Thio), 129.1 (d, JPC ) 12.2
) 11.8 Hz; CH2), 27.1 (d, JPC ) 4.3 Hz; CH2), 27.2 (d, JPC
)
5.3 Hz; CH2), 27.9 (d, JPC ) 9.7 Hz; CH2), 29.1 (d, JPC ) 2.3
Hz; m-Ph), 132.0 (d, JP-C ) 4.6 Hz; C3 Thio), 132.5 (d, JPC
6.2 Hz; CdCH), 133.1 (d, JPC ) 2.9 Hz; p-Ph), 134.1 (d, JPC
)
)
2
Hz; CH2), 36.9 (d, JPC ) 24.7 Hz; PCHCH2), 48.3 (d, JPC
)
32.7 Hz; PCH), 123.1 (s; C5 Py), 124.5 (d, JPC ) 12.2 Hz; C3
Py), 124.7 (s; C,5 Py), 125.7 (d, JPC ) 4.8 Hz; C3 Py), 127.9 (d,
JPC ) 44.9 Hz; PCRdC), 133.2 (d, JPC ) 5.3 Hz; CdCH), 136.5
(s; C4 Py), 139.7 (d, JPC ) 7.8 Hz; PCdCâ), 139.3 (s; C4 Py),
149.8 (s; C6 Py), 153.2 (d, JPC ) 12.1 Hz; PC-Câ), 153.5 (d,
JPC ) 9.3 Hz; C2 Py), 153.9 (s; C6 Py), 164.2 (d, JPC ) 6.8 Hz;
C2 Py. 31P{1H} NMR (81.014 MHz, CD2Cl2): δ +86.5. HR-MS
(FAB-mNBA): m/z 515.0638 [M - Cl]+, calcd for C24H27N2-
PPdCl2. 515.0642. Anal. Calcd for C24H27N2PPdCl2 (551.788):
C, 52.24; H, 4.93; N, 5.08. Found: C, 52.03; H, 4.86; N, 5.16.
[1-phenyl-2-(2-pyridyl)-5-phenylphosphol-2-ene]-
PdCl2 (3b). A solution of complex 2b (0.49 g, 0.90 mmol) and
pyridine (1 mL) in CH2Cl2 (20 mL) was heated at 45 °C for 3
days. The volatiles were removed under vacuum, and the
residue was washed with diethyl ether (3 × 10 mL) and dried
12.6 Hz; o-Ph), 138.1 (d, JP-C ) 7.8 Hz; PCdCâ), 139.6 (s; C4
Py), 150.8 (d, JPC ) 12.6 Hz; PC-Câ), 153.8 (s; C6 Py), 162.3
(d, JPC ) 8.1 Hz; C2 Py); the C2 thio was not observed. 31P{1H}
NMR (81.014 MHz, CD2Cl2): δ +69.0. HR-MS (FAB-mNBA):
m/z 515.9772 [M - Cl]+, calcd for C23H20NSPPdCl2 515.9782.
Anal. Calcd for C23H21NSPPdCl2 (551.787): C, 50.07; H, 3.84;
N, 2.54. Found: C, 50.11; H, 3.89; N, 2.45.
[1-cyclohexyl-2-(2-pyridyl)-5-(2-thienyl)phosphol-2-ene]-
PdCl2 (3c′). Following the procedure for complex 3b, the
reaction of 2c′ (0.50 g, 0.90 mmol) afforded 3c′ as an air-stable
1
red solid (yield 0.43 g, 0.78 mmol, 87%). H NMR (200 MHz,
CD2Cl2): δ 0.82-1.95 (m, 8H; CH2), 2.23 (m, 4H; CH2), 2.70-
2
3.15 (m, 5H; CH2, CH Cy), 4.63 (d broad, JPH ) 8.2 Hz, 1H;
PCH), 6.22 (m, 1H; dCH), 7.11 (m, 1H; H5 Py), 7.21-7.63 (m,
3
3H; H arom), 7.74-8.03 (m, 2H; H arom), 9.69 (d, JHH ) 6.5

A New Family of P,N Chelates
Organometallics, Vol. 23, No. 26, 2004 6199
Hz, 1H; H6 Py). 13C{1H} NMR (75.469 MHz, CD2Cl2): δ 21.9
(s; dCCH2CH2), 22.8 (s; CH2), 25.8 (d, JPC ) 3.0 Hz; CH2), 26.9
(d, JPC) 11.6 Hz; CH2), 27.2 (s; CH2), 28.3 (d, JPC ) 8.1 Hz;
4.22 (d, 2JPH ) 4.9 Hz, 1H; PCH), 5.59 (m, 1H; CdCH), 6.92-
7.29 (m, 8H; H arom), 7.32-7.63 (m, 5H; H arom), 8.42 (m,
1H; H6 Py). 13C{1H} NMR (50.323 MHz, CDCl3): δ 22.8 (s; d
CCH2CH2), 26.2 (s; CH2), 28.5 (s; CH2), 56.4 (d, JPC ) 8.1 Hz;
PCH), 120.7 (s; C5 Py), 123.7 (d, JPC ) 7.1 Hz; C3 Py), 126.7 (s;
CdCH), 128.7 (d, JPC ) 7.1 Hz; m-Ph), 129.3 (s; p-Ph), 129.4
(d, JPC ) 4.7 Hz; m-Ph), 129.7 (s; p-Ph), 130.2 (d, JPC ) 19.7
Hz; o-Ph), 133.7 (d, JPC ) 18.0 Hz; o-Ph), 137.1 (s; C4 Py), 139.2
(d, JPC ) 23.1 Hz; PCRdC), 144.8 (d, JPC ) 10.6 Hz; PCdCâ),
148.1 (s; PC-Câ), 149.8 (s; C6 Py), 164.5 (d, JPC ) 16.1 Hz; C2
Py); the ipso-Ph carbon resonance was not observed. 31P{1H}
NMR: δ +25.1. Anal. Calcd for C25H22NP (367.432): C, 81.72;
H, 6.04; N, 3.81. Found: C, 81.62; H, 5.91; N, 3.87.
CH2), 29.7 (d, JPC ) 9.0 Hz; CH2), 30.7 (s; CH2), 39.6 (d, JPC
)
20.3 Hz; PCH), 48.9 (d, JPC ) 33.6 Hz; PCHCd), 124.3 (d, JPC
) 11.8 Hz; C3 Py), 124.8 (s; C5 Py), 128.3 (s; C5 Thio), 129.4 (s;
C4 Thio), 131.6 (d, JPC ) 4.6 Hz; C3 Thio), 134.8 (s broad, Cd
CH), 135.9 (d, JPC ) 19.0 Hz, C2 Thio), 138.2 (s broad, PCd
Câ), 139.1 (s; C4 Py), 148.9 (d, JPC ) 13.0 Hz; PC-Câ), 153.9
(s; C6 Py), 164.2 (d, JPC ) 6.9 Hz; C2 Py); the PCR resonance
was not observed. 31P{1H} NMR (81.014 MHz, CD2Cl2):
δ
+82.6. Anal. Calcd for C23H26NSPPdCl2 (556.827): C, 49.61;
H, 4.71; N, 2.52. Found: C, 49.58; H, 4.64; N, 2.44.
1-Phenyl-2,5-bis(2-pyridyl)phosphol-2-ene (4a). To a
solution of complex 3a (0.49 g, 0.90 mmol) in CH2Cl2 was added
neat 1,2-(diphenylphosphino)ethane (dppe; 0.36 g, 0.90 mmol).
The solution was stirred for 12 h at room temperature, and
then the solvent was removed. The residue was extracted with
toluene (2 × 10 mL). Evaporation of toluene afforded a residue
that was subsequently washed with pentane (3 × 2 mL) and
dried under vacuum. 4a was obtained as a yellow solid (yield
1-Cyclohexyl-2-(2-pyridyl)-5-phenylphosphol-2-ene (4b′).
Following the procedure described for compound 4a, reaction
of complex 3b′ (0.33 g, 0.60 mmol) and dppe (0.18 g, 0.60 mmol)
afforded compound 4b′ as a yellow solid (yield 0.19 g, 0.51
mmol, 85%). 1H NMR (300 MHz, CDCl3): δ 1.02 (m, 4H; CH2),
1.32-1.86 (m, 8H; CH2), 2.52 (m, 4H; CH2, CH Cy), 3.1 (m,
1H; CH2), 4.12 (m, 1H; PCH), 5.44 (m, 1H; CH2CH), 7.13 (dd,
3
3JHH ) 4.5 Hz, JHH ) 7.8 Hz, 1H; H5 Py), 7.32-7.54 (m, 6H;
1
3
0.31 g, 0.85 mmol, 95%). H NMR (200 MHz, C6D6): δ 1.21-
H arom and H3 Py), 7.58 (m, 1H; H4 Py), 8.44 (d, JHH ) 4.5
1.72 (m, 2H; dCH2CH2), 1.75-1.98 (m, 2H; dCCH2), 3.02-
Hz, 1H; H6 Py). 13C{1H} NMR (75.469 MHz, CDCl3): δ 21.3
3.31 (m, 2H; CH2), 4.50 (dd, 2JPH ) 4.7 Hz, 3JHH ) 2.0 Hz, 1H;
(s; dCCH2CH2), 24.7 (s; CH2), 25.2 (s; CH2), 26.0 (d, JP-C
)
3
3
PCH), 5.52 (m, 1H; CdCH), 6.42 (dd, JHH ) 4.7 Hz, JHH
)
2.3 Hz; CH2), 26.1 (s; CH2), 27.8 (d, JPC ) 8.7 Hz; CH2), 28.1
(s; CdCCH2), 28.7 (s; dCCH2), 38.0 (d, JPC ) 20.9 Hz; P-CH),
4.5 Hz, 1H; H5 Py), 6.58 (m, 1H; H3 Py), 6.72-7.08 (m, 6H; H
arom), 7.38 (d, 3JHH ) 7.0 Hz, 1H; H3 Py), 7.68 (dd, 3JHH ) 6.9
48.1 (d, JPC ) 11.0 Hz; PCH), 119.0 (s; C5 Py), 121.7 (d, JPC
)
Hz, JHH ) 5.0 Hz, 1H; H4 Py), 7.70 (dd, JHH ) 7.0 Hz, JHH
7.6 Hz; C3 Py), 127.1 (s; m-C Ph), 127.7 (s; p-C Ph), 125.6 (d,
3
3
3
) 5.2 Hz, 1H; H4 Py), 8.40 (d, 3JHH ) 4.7 Hz, 1H; H6 Py), 8.43
JPC ) 2.1 Hz; CdCH), 128.2 (d, JPC ) 9.8 Hz; o-C Ph), 135.5
2
(d, JHH ) 7.1 Hz, 1H; H6 Py). 13C{1H} NMR (50.323 MHz,
(s; C4 Py), 141.7 (d, JPC ) 9.4 Hz; PCdCâ), 147.8 (s; C6 Py),
3
2
CDCl3): δ 22.3 (s; dCCH2CH2), 28.0 (s; CH2), 29.7 (s; CH2),
55.4 (d, JPC ) 8.1 Hz; PCH), 121.2 (s; 2 × C5 Py), 122.6 (d, JPC
) 6.9 Hz; C3 Py), 123.0 (d, JPC ) 8.2 Hz; C3 Py), 128.2 (d, JPC
) 7.2 Hz; m-Ph), 128.5 (s; CdCH), 132.3 (s; p-Ph), 133.4 (d,
JPC ) 13.2 Hz; o-Ph), 136.1 (s; C4 Py), 136.7 (s; C4 Py), 137.2
(d, JPC ) 8.1 Hz; PCRdC), 141.2 (d, JPC ) 7.1 Hz; PCdCâ),
148.9 (s; PC-Câ), 149.9 (s; C6 Py), 150.2 (s; C6 Py), 158.2 (d,
JPC ) 16.8 Hz; C2 Py), 163.9 (d, JPC ) 16.2 Hz; C2 Py), the
ipso-Ph carbon resonance was not observed. 31P{1H} NMR
(81.014 MHz, CDCl3): δ +22.7. Anal. Calcd for C24H21N2P
(368.420): C, 78.24; H, 5.75; N, 7.60. Found: C. 78.14; H, 5.81;
N, 7.56.
148.4 (s; PC-Câ), 164.2 (d, JPC ) 16.4 Hz; C2 Py); the ipso-C
Ph and PCRd carbon resonances were not observed. 31P{1H}
NMR (81.014 MHz, CDCl3): δ +37.2.
1-Phenyl-2-(2-pyridyl)-5-(2-thienyl)phosphol-2-ene (4c).
Following the procedure described for compound 4a, reaction
of complex 3c (0.52 g, 0.95 mmol) and dppe (0.37 g, 0.95 mmol)
afforded compound 4c as a red solid (yield 0.39 g, 0.90 mmol,
95%). 1H NMR (300 MHz, CDCl3): δ 1.52-1.65 (m, 2H;
CCH2CH2), 1.94-2.01 (m, 2H; CH2), 2.88-2.98 (m, 2H; Cd
2
3
CH2), 4.49 (dd, JPH ) 4.6 Hz, JHH ) 2.1 Hz, 1H; PCH), 5.62
(m, 1H; CdCH), 6.63 (m, 2H; H5 Py and H4 Thio), 6.82 (d, 3JHH
) 5.1 Hz, 1H; H3 Py), 6.95-7.15 (m, 5H; m-Ph, p-Ph, H3 Thio
3
1-Cyclohexyl-2,5-bis(2-pyridyl)phosphol-2-ene (4a′). Fol-
lowing the procedure described for compound 4a, reaction of
complex 3a′ (0.43 g, 0.86 mmol) and dppe (0.32 g, 0.86 mmol)
afforded compound 4a′ as a yellow solid (yield 0.39 g, 0.79
mmol, 93%). 1H NMR (200 MHz, C6D6): δ 0.92 (m, 3H; CH2),
1.10-1.75 (m, 8H; CH2), 1.95 (m, 5H; CH2, CH Cy), 2.95 (m,
1H; CH2), 4.51 (m, 1H; PCH), 5.62 (m, 1H; CdCH), 6.60 (m,
2H; H5 Py), 7.02-7.25 (m, 3H; H4 Py and H3 Py), 7.47 (dd,
3JHH ) 7.7 Hz, 4JHH ) 1.0 Hz, 1H; H4 Py), 8.50 (m, 2H; H6 Py).
13C{1H} NMR (50.323 MHz, C6D6): δ 22.5 (s; dCCH2CH2), 25.8
(s; CH2), 26.4 (s; CH2), 27.2 (d, JPC ) 7.8 Hz; CH2), 27.4 (d, JPC
and H4 Py), 7.21 (d, JHH ) 3.5 Hz, 1H; H5 Thio), 7.71 (ddd,
2JPH ) 15.8 Hz, 3JHH ) 6.1 Hz, 4JHH ) 1.2 Hz, 2H; o-Ph), 8.47
3
(d, JHH ) 4.6 Hz, 1H; H6 Py). 13C{1H} NMR (75.469 MHz,
CDCl3): δ 22.1 (s; dCCH2CH2), 25.4 (s; CH2), 27.9 (s; dCH2),
56.0 (d, JPC ) 8.5 Hz; PCH), 120.8 (s; C5 Py), 121.7 (d, JPC
)
7.3 Hz; C3 Py), 125.5 (d, JPC ) 2.1 Hz; C4 Thio), 127.2 (d, JPC
) 7.8 Hz; CdCH), 127.7 (d, JPC ) 10.1 Hz; C3 Thio), 128.3 (s;
C5 Thio), 128.6 (d, JPC ) 6.5 Hz; m-Ph), 129.1 (s; p-Ph), 130.8
(d broad, JPC ) 15.0 Hz; ipso-Ph), 132.6 (d, JPC ) 20.1 Hz;
o-Ph), 136.1 (s; C4 Py), 140.2 (d, JPC ) 22.6 Hz; PCRdC), 144.1
2
(d, JPC ) 4.3 Hz; PCdCâ), 148.3 (s; PC-Câ), 149.6 (s; C6 Py),
3
) 10.9 Hz, CH2), 28.0 (s; CH2), 28.8 (d, JPC ) 9.7 Hz; CH2),
164.5 (d, 2JPC ) 16.7 Hz; C2 Py); the C2 thio carbon resonance
was not oberved. 31P{1H} NMR (81.014 MHz, CDCl3): δ +22.4.
HR-MS (FAB-mNBA): m/z 373.1054 [M•+]; calcd 373.1054.
Anal. Calcd for C23H20NPS (373.458): C, 73.97; H, 5.40; N,
3.75. Found: C, 73.91; H, 5.31; N, 3.84.
29.8 (d, JPC ) 5.9 Hz; CH2), 39.2 (d, JPC ) 19.3 Hz; PCH), 48.9
(d, JPC ) 10.0 Hz; PCH), 120.9 (d, JPC ) 2.3 Hz; C5 Py), 120.8
(s; C5 Py), 122.3 (d, JPC ) 7.8 Hz; C3 Py), 123.8 (d, JPC ) 8.6
Hz; C3 Py), 127.9 (s; CdCH), 135.3 (s; C4 Py), 136.0 (s; C4 Py),
138.2 (d, JPC ) 8.6 Hz; PCRdC), 146.9 (d, JPC ) 3.1 Hz; PCd
Câ), 149.1 (s; C6 Py), 149.5 (s; C6 Py), 149.6 (s; PC-Câ), 158.0
(d, JPC ) 18.0 Hz; C2 Py), 165.9 (d, JPC ) 17.2 Hz; C2 Py).
31P{1H} NMR (81.014 MHz, C6D6): δ +34.9. HR-MS (FAB-
mNBA): m/z 375.1990 [M + H]+, calcd 375.1990. Anal. Calcd
for C24H27N2P: C, 76.98; H, 7.27; N, 7.48. Found: C, 76.88; H,
7.18; N, 7.56.
1-Cyclohexyl-2-(2-pyridyl)-5-(2-thienyl)phosphol-
2-ene (4c′). Following the procedure described for compound
4a, reaction of complex 3c′ (0.38 g, 0.70 mmol) and dppe (0.28
g, 0.70 mmol) afforded compound 4c′ as an orange solid (yield
0.22 g, 0.59 mmol, 85%). 1H NMR (200 MHz, CDCl3): δ 0.82-
1.30 (m, 6H; CH2), 1.48-1.85 (m, 6H; CH2), 2.56-2.71 (m, 4H;
2
CH2, CH Cy), 3.18 (m, 1H; CH2), 4.17 (d, JPH ) 2.3 Hz, 1H;
1-Phenyl-2-(2-pyridyl)-5-phenylphosphol-2-ene (4b). Fol-
lowing the procedure described for compound 4a, reaction of
complex 3b (0.46 g, 0.85 mmol) and dppe (0.33 g, 0.85 mmol)
afforded compound 4b as a yellow solid (yield 0.29 g, 0.78
mmol, 92%). 1H NMR (200 MHz, CDCl3): δ 1.51-1.92 (m, 2H;
CCH2CH2), 2.22-2.38 (m, 2H; CH2), 3.21-3.53 (m, 2H; CH2),
PCH), 5.69 (m, 1H; CH2CH), 7.12-7.18 (m, 3H; H5 Py, H3 Thio,
3
H4 Thio), 7.48 (d, JHH ) 6.3 Hz, 1H; H3 Py), 7.65 (m, 2H; H5
3
Thio and H4 Py), 8.52 (d, JHH ) 4.3 Hz, 1H; H6 Py). 13C{1H}
NMR (50.323 MHz, CDCl3): δ 22.5 (s; CdCH2CH2), 24.2 (s;
CH2), 25.9 (s; CH2), 26.7 (s; CH2), 28.0 (d, JPC ) 4.7 Hz; CH2),
28.7 (s; dCCH2), 29.0 (s; dCCH2), 30.4 (d, JPC ) 6.9 Hz; CH2),

6200 Organometallics, Vol. 23, No. 26, 2004
Leca et al.
Table 3. Summary of Crystal Data and Structure Refinement Details for 2c′, 3a‚1.5CH2Cl2, 3a′‚CH2Cl2,
3c′‚0.5CH2Cl2, and 6‚CH2Cl2
2c′
3a‚1.5CH2Cl2
3a′‚CH2Cl2
3c′‚0.5CH2Cl2
6‚CH2Cl2
mol formula
mol wt
a (Å)
C
23H26Cl2NPPdS
C25.5H24Cl5N2PPd
673.08
14.985(5)
9.785(5)
37.375(5)
90
98.388(5)
90
5422(3)
8
1.661
C25H29Cl4N2PPd
636.67
8.7170(2)
16.2360(3)
18.9070(4)
90
C23.5H26Cl3NPPdS C24H22Cl4NPPtS
556.78
598.23
10.866(5)
15.475(5)
16.973(5)
90
106.722(5)
90
724.35
9.504(5)
17.436(5)
15.476(5)
90
96.230(5)
90
10.3320(2)
17.1370(5)
13.1100(4)
90
106.6950(10)
90
2223.40(10)
4
1.252
monoclinic
P21/n
293(2)
0.710 69
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
90
90
2675.89(10)
4
1.580
2733.3(17)
4
1.454
2549.4(17)
4
1.887
Dc (g cm-3
)
cryst syst
monoclinic
C2/c
293(2)
0.710 69
orthorhombic
P212121
293(2)
monoclinic
P21/n
monoclinic
P21/n
293(2)
0.710 69
space group
temp (K)
293(2)
wavelength Mo KR (Å)
cryst size (mm)
0.710 69
0.710 69
0.18 × 0.12 × 0.12 0.35 × 0.20 × 0.05 0.38 × 0.36 × 0.36 0.35 × 0.35 × 0.35 0.1 × 0.05 × 0.01
µ (mm-1
F(000)
)
1.252
1128
2.01-27.47
0 e h e 13
0 e k e 22
-17 e l e 16
25 726
0.953
2232
3.10-27.49
-19 e h e 19
-12 e k e 10
-48 e l e 48
11 725
1.170
1288
2.49-27.51
0 e h e 11
0 e k e 21
0 e l e 24
30 440
1.018
1124
6.082
1400
θ limit (deg)
2.92-27.49
-14 e h e 14
-19 e k e 20
-22 e l e 22
34 847
3.18-27.48
-12 e h e 12
-21 e k e 22
-20 e l e 20
30 455
index ranges hkl
no. of rflns collected
no. of indep rflns
5046
3887
6991
4216
3452
3351
12 092
11 191
no. of rflns with I > 2σ(I)
4972
5027
no. of data/restraints/params 5046/0/263
5167/0/324
1.0499
R1 ) 0.0397
wR2 ) 0.0909
R1 ) 0.0546
wR2 ) 0.0977
0.562 and -0.759
3452/0/299
1.125
R1 ) 0.0336
wR2 ) 0.0860
R1 ) 0.0350
wR2 ) 0.0872
0.697 and -0.862
6251/0/298
1.080
R1 ) 0.0570
wR2 ) 0.1687
R1 ) 0.0709
wR2 ) 0.1869
1.254 and -0.837
5841/0/294
1.154
R1 ) 0.0433
wR2 ) 0.1079
R1 ) 0.0517
wR2 ) 0.1131
1.437 and -3.049
goodness of fit on F2
1.097
final R indices (I > 2σ(I))
R1 ) 0.0444
wR2 ) 0.1039
R1 ) 0.0662
wR2 ) 0.1142
0.916 and -1.185
R indices (all data)
largest diff peak and
hole (e Å-3
)
39.4 (d, JPC ) 21.8 Hz; PCH), 48.8 (d, JPC ) 11.8 Hz; PCH),
heated at 45 °C and stirred for 3 days. The solvent was
removed, and then the residue was washed with diethyl ether
(2 × 10 mL) and dried under vacuum. Complex 6 was obtained
as an air-stable orange solid (yield 0.042 g, 0.067 mmol, 83%).
1H NMR (200 MHz, CDCl3): δ 1.80-2.05 (m, 4H; dCCH2CH2),
3
121.3 (s; C5 Py), 122.5 (d, JPC ) 6.9 Hz; C3 Py), 123.9 (s; C4
thio), 125.6 (s; CdCH), 127.1 (d, 3JPC ) 10.2 Hz; C3 thio), 127.5
(s; C5 thio), 137.2 (s; C4 Py), 149.0 (s; PC-Câ), 149.3 (s; C6 Py),
165.7 (d, 2JPC ) 14.2 Hz; C2 Py); the C2 thio, PCRdC, and PCd
Câ carbon resonances were not observed. 31P{1H} NMR (81.014
MHz, CDCl3): δ +36.6.
2
2.90 (m, 2H; CH2), 4.36 (d, JPH ) 8.2 Hz, 1H; PCH), 6.17 (s
broad, 1H; CdCH), 6.87 (m, 1H; H5 Py), 7.30-7.55 (m, 6H; H
[1-phenyl-2-(2-pyridyl)-5-(2-thienyl)phosphole]PtCl2
(5). A solution of 1-phenylphosphole 1a (0.07 g, 0.20 mmol) in
CH2Cl2 (5 mL) was added, at room temperature, to a solution
of (CH3CN)2PtCl2 (0.09 g, 0.20 mmol) in CH2Cl2 (10 mL). The
solution was stirred for 1 h at room temperature, and the
volatile materials were removed under vacuum. The residue
was washed with diethyl ether (3 × 10 mL) and dried under
vacuum. Complex 5 was obtained as an air-stable orange solid
3
arom), 7.70-8.00 (m, 4H; H arom), 10.14 (d, JH,H ) 5.9 Hz,
1H; H6 Py). 13C{1H} NMR (50.323 MHz, CD2Cl2): δ 21.0 (s;
dCCH2CH2), 24.6 (s; CH2), 27.2 (d, JPC ) 9.7 Hz; CH2), 54.5
(d, JPC ) 42.9 Hz; PCH), 123.8 (s; C5 Py), 124.0 (d, JPC ) 47.5
Hz; ipso-Ph), 126.8 (s; C4 thio or C5 thio), 127.0 (s; C4 thio or
C5 thio), 127.7 (d, JPC ) 48.7 Hz; PCRdC), 128.1 (d, JPC ) 12.9
Hz, m-Ph), 131.1 (d; JPC ) 5.4 Hz, C3 thio), 131.1 (s; C3 Py),
1
(yield 0.10 g, 0,16 mmol, 79%). H NMR (200 MHz, CD2Cl2):
131.4 (s; p-Ph), 133.0 (d, JPC ) 12.2 Hz; o-Ph), 133.5 (d, JPC
)
δ 1.62-2.00 (m, 4H; dCCH2CH2), 2.73-2.60 (m, 2H; dCCH2),
16,6 Hz; CdCH), 138.2 (s; C4 Py), 147.1 (d, JPC ) 14.3 Hz, PCd
Câ), 151.5 (s; C6 Py), 152.7 (s; PC-Câ), 163.0 (d, JPC ) 5.4 Hz;
C2 Py); the C2 thio resonance was not observed. 31P{1H} NMR
(81.014 MHz, CDCl3): δ +41.2 (1JP-Pt ) 3877.5 Hz). Anal.
Calcd for C23H20NSPPtCl2: C, 43.20; H, 3.15; N, 2.19. Found:
C, 43.09; H, 3.23; N, 2.09.
3
2.86-3.07 (m, 2H; dCCH2), 6.26 (d, JHH ) 4.3 Hz, 1H; H4
Py), 7.10-7.90 (m, 10H; H arom), 9.88 (d, 3JH-H ) 5.8 Hz, 1H;
H6 Py). 13C{1H} NMR (50.323 MHz, CD2Cl2): δ 21.5 (s;
dCCH2CH2), 22.4 (s; dCCH2CH2), 27.9 (d, JPC ) 9.3 Hz; d
CCH2), 29.5 (d, JPC ) 10.6 Hz; dCCH2), 123.4 (d, JPC ) 9.7
Hz; C3 Py), 123.5 (s; C5 Py), 124.3 (d, JPC ) 53.7 Hz; ipso-Ph),
3
127.7 (s; C4 thio or C5 thio), 128.7 (d, JPC ) 12.4 Hz; m-Ph),
X-ray Crystallographic Study. Single crystals suitable
for X-ray crystal analysis were obtained by diffusion of vapors
of pentane into a CH2Cl2 solution of 3a, 3a′, and 6 at room
temperature, by diffusion of diethyl ether into a CH2Cl2
solution of 2c′ and 3c′ at 5 °C, and by slow evaporation of a
CH2Cl2 solution of 3b. Single-crystal data collections were
performed at room temperature with a Nonius KappaCCD
diffractometer (Center de Diffractome´trie, Universite´ de Rennes
1, France), with Mo KR radiation (λ ) 0.710 73 Å). Reflections
were indexed, Lorentz-polarization corrected, and integrated
by the DENZO program of the KappaCCD software pack-
age. The data merging process was performed using the
129.1 (s; C4 or C5 thio), 130.5 (d, JPC ) 60.6 Hz; PCRdC), 132.6
(d, JPC ) 2.9 Hz; C3 thio), 133.5 (d, JPC ) 12.9 Hz; o-Ph), 133.9
(d, JP-C ) 4.1 Hz; p-Ph), 135.3 (d, JPC ) 19.4 Hz; C2 thio), 135.8
(d, JPC ) 57.5 Hz; PCRdC), 138.9 (s; C4 Py), 150.8 (d, JPC
)
12.0 Hz; PCdCâ), 148.3 (d, JPC ) 15.8 Hz; PCdCâ), 152.1 (s;
C6 Py), 152.6 (d, JPC ) 17.6 Hz; C2 Py). 31P{1H} NMR (81.014
MHz, CD2Cl2): δ +37.3 (JPPt ) 3704.0 Hz). HR-MS (FAB-
mNBA): m/z 602.0375 [M - Cl]+, calcd for C23H20NSPPtCl2
602.036 94. Anal. Calcd for C23H20NSPPtCl2: C, 43.20; H, 3.15;
N, 2.19. Found: C, 43.12; H, 3.21; N, 2.12.
[1-phenyl-2-(2-pyridyl)-5-(2-thienyl)phosphol-2-ene]-
PtCl2 (6). To a solution of 5 (0.051 g, 0.08 mmol) in CH2Cl2
(10 mL) was added an excess of pyridine. The solution was

A New Family of P,N Chelates
Organometallics, Vol. 23, No. 26, 2004 6201
SCALEPACK program.19 Structure determinations were per-
formed by direct methods with the solving program SIR97,20
which revealed all the non-hydrogen atoms. The SHELXL
program21 was used to refine the structures by full-matrix least
squares based on F2. All non-hydrogen atoms were refined with
anisotropic displacement parameters. Hydrogen atoms were
included in idealized positions and refined with isotropic
displacement parameters, except for the H(1), H(3), and H(40)
hydrogen atoms of 3a‚1.5CH2Cl2, the H(1) and H(3) hydrogen
atoms of 3c′‚0.5CH2Cl2, and the H(3) hydrogen atom of
6‚CH2Cl2, which were located and refined with isotropic
displacement parameters. The crystal structure refinement of
compound 3b (R1 ) 0.1582) can only be used for the confirma-
tion of the structure. Atomic scattering factors for all atoms
were taken from ref 22. Details of crystal data and structural
refinements are given in Table 3. CCDC reference numbers
208509-208513 and 236734 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge at www.ccdc.cam.ac.uk/conts/retreving.html or
from the Cambridge Crystallographic Data Center, 12 Union
Road, Cambridge CB2 1EZ, U.K. (fax (internat.) + 44-1223-
336-033; e-mail deposit@ccdc.cam.ac.uk).
Acknowledgment. We thank the Ministe`re de
l’Education Nationale, de la Recherche et de la Tech-
nologie, the CNRS, and the Institut Universitaire de
France.
(19) Otwinowski, Z.; Minor, W. In Methods in Enzymology; Carter,
C. W., Jr., Sweet, R. M., Eds.; Academic Press: New York, 1997; Vol.
276, p 307.
(20) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.; Giaco-
vazzo, C.; Guagliardi, A.; Moliterni, A. G. G., Polidori, G.; Spagna, R.
J. Appl. Crystallogr. 1999, 32, 115.
(21) Sheldrick, G. M. SHELX97: Program for the Refinement of
Crystal Structures; University of Go¨ttingen, Go¨ttingen, Germany,
1997.
Supporting Information Available: X-ray data as CIF
files. This material is available free of charge via the Internet
at http://pubs.acs.org.
OM049510I
(22) International Tables for X-ray Crystallography; Kluwer: Dor-
drecht, The Netherlands, 1992; Vol. C.