P,N-chelate complexes of Pd(II) and Pt(II) based on a phosphaalkene motif: A catalyst for the overman-claisen rearrangement

Article abstract of DOI:10.1021/om700784x

The reaction of E/Z-MesP=C(Ph)(Py) (1, Mes = 2,4,6-Me₃C ₆H_2-) with (cod)PtCl₂ or (cod)PdCl₂ affords P,N-chelate complexes [MesP=C(Ph)(Py)PtCl₂] (2a) and [MesP=C(Ph)(Py)PdCl₂] (2b), respectively. Compounds 2a and 2b were fully characterized spectroscopically, and both were characterized by X-ray crystallography. The molecular structures exhibited almost identical metrical parameters. The P=C bond lengths in 2a and 2b [1.672(4) and 1.675(3) A, respectively] were shortened substantially with respect to that of 1 [1.7043(16) A]. Complex 2b was explored as a catalyst for the Overman-Claisen rearrangement. Several allyl trichloroacetimidate substrates [HN=C(CCI ₃)OCH₂CH=CHR₁: 3a, R₁ = Me; 3b, R₁ = n-Pr; 3c, R₁ = n-Hep; 3d, R₁ = CH ₂CH₂Ph; 3e, R₁ = i-Pr] were successfully rearranged to their respective branched amides [H₂C=CHCH(RI)NHC(O) CCl₃: 4a-e] using 5 mol % 2b as catalyst. Isolated yields ranged from a low of 33% for the bulky 4e to a high of 91% for 4a.

Full text of DOI:10.1021/om700784x

Organometallics 2007, 26, 6481-6486
6481
P,N-Chelate Complexes of Pd(II) and Pt(II) Based on a
Phosphaalkene Motif: A Catalyst for the
Overman-Claisen Rearrangement
Julien Dugal-Tessier, Gregory R. Dake,* and Derek P. Gates*
Department of Chemistry, UniVersity of British Columbia, VancouVer, British Columbia V6T 1Z3, Canada
ReceiVed August 1, 2007
The reaction of E/Z-MesPdC(Ph)(Py) (1, Mes ) 2,4,6-Me3C6H2-) with (cod)PtCl2 or (cod)PdCl2 affords
P,N-chelate complexes [MesPdC(Ph)(Py)PtCl2] (2a) and [MesPdC(Ph)(Py)PdCl2] (2b), respectively.
Compounds 2a and 2b were fully characterized spectroscopically, and both were characterized by X-ray
crystallography. The molecular structures exhibited almost identical metrical parameters. The PdC bond
lengths in 2a and 2b [1.672(4) and 1.675(3) Å, respectively] were shortened substantially with respect
to that of 1 [1.7043(16) Å]. Complex 2b was explored as a catalyst for the Overman-Claisen
rearrangement. Several allyl trichloroacetimidate substrates [HNdC(CCl3)OCH2CHdCHR1: 3a, R1 )
Me; 3b, R1 ) n-Pr; 3c, R1 ) n-Hep; 3d, R1 ) CH2CH2Ph; 3e, R1 ) i-Pr] were successfully rearranged
to their respective branched amides [H2CdCHCH(R1)NHC(O)CCl3: 4a-e] using 5 mol % 2b as catalyst.
Isolated yields ranged from a low of 33% for the bulky 4e to a high of 91% for 4a.
phosphaferrocenes (C6,7), and R-iminophospholyl (D8) com-
pounds have all been employed successfully as ligands for
metals, and complexes of A, B, and C have been successfully
employed in catalysis. Examples that have an acyclic phos-
phaalkene motif are more limited in scope. Most acyclic
phosphaalkene-based ligands employed in catalysis utilize the
sterically encumbering Mes* ligand (Mes* ) 2,4,6-tri-tert-
butylphenyl) to confer kinetic and thermodynamic stability to
the PdC bond (E9-11 and F12).13 Particularly relevant to the
present studies are 2-pyridyl-substituted phosphaalkenes G14 and
H15,16 where the PdC bond is similarly flanked by the Mes*
substituent. Although P(sp2),N(sp2) compounds containing acy-
clic phosphaalkenes have been coordinated to transition metals,
to our knowledge, only E (X ) N) has been employed in
catalysis.
Introduction
The development of tailor-made phosphorus-containing ligands
has played a major role in the immense impact that homoge-
neous catalysis has made on synthetic organic chemistry.
Although trivalent phosphines still dominate the field of late-
transition metal-based catalysis, there is growing interest in the
development of ligands containing low-coordinate phosphorus.1
Low-coordinate phosphorus compounds are attractive because
their unique π-acceptor properties impart desirable character-
istics to electron-rich transition metal centers.1b
Some examples of ligands having low-coordinate phosphorus
atoms are shown in Chart 1. Significant contributions to this
area have stemmed from the development of cyclic divalent
phosphorus systems. As examples, phosphinines (A2,3 and B4,5),
* Corresponding authors. E-mail: gdake@chem.ubc.ca (G.R.D.);
dgates@chem.ubc.ca (D.P.G.).
(5) (a) Schmid, B.; Venanzi, L. M.; Gerfin, T.; Gramlich, V.; Mathey,
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A.; Mathey, F. Inorg. Chem. 1991, 30, 4693. (c) Bre`que, A.; Santini, C.
C.; Mathey, F.; Fischer, J.; Mitschler, A. Inorg. Chem. 1984, 23, 3463.
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(1) For recent reviews highlighting the use of low-coordinate phosphorus
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F.; Le Floch, P. Prog. Inorg. Chem. 2001, 49, 455. (b) Le Floch, P.; Mathey,
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(4) See, for example: (a) Miyake, Y.; Isomura, E.; Iyoda, M. Chem.
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10.1021/om700784x CCC: $37.00 © 2007 American Chemical Society
Publication on Web 11/08/2007

6482 Organometallics, Vol. 26, No. 25, 2007
Dugal-Tessier et al.
Chart 1
Scheme 1. Strategy for the Preparation of Phosphaalkene
Herein, we report two new chelating phosphaalkene-based
P(sp2)-N(sp2) complexes of palladium(II) and platinum(II):
MesPdC(Ph)(Py)PtCl2 (2a) and MesPdC(Ph)(Py)PdCl2 (2b).
These new complexes bear the modestly bulky Mes-substituent
at phosphorus as compared to known P(sp2)-N(sp2) complexes,
which often utilize the larger Mes* substituent to impart stability
to the ligand. Moreover, a phosphaalkene ligated palladium(II)
complex (2b) is demonstrated to be a catalyst for the aza-Claisen
rearrangement of trichloroacetimidates (Overman-Claisen rear-
rangement).
Ligands Bearing Unique Donor-Acceptor Properties
Results and Discussion
We have recently employed the phospha-Peterson reaction
as a general route to phosphaalkenes bearing modest degrees
of steric bulk.17 The relatively mild conditions needed to affect
this transformation suggested to us a route to novel chelating
phosphaalkene ligands for use in transition metal catalysis. An
idealized strategy for the development of phosphaalkene ligands
bearing tunable donor-acceptor properties is shown in Scheme
1. An attractive feature of this approach is that the modular
nature of the ligand synthesis allows for the facile modification
of steric and electronic properties. For example, isolable
phosphaalkene ligands bearing varying degrees of steric bulk
(i.e., Mes and larger) may be synthesized from a variety of
functional ketones using the phospha-Peterson reaction.
Synthesis of Palladium(II) and Platinum(II) Complexes.
In an attempt to prepare platinum complex 2a, C-pyridyl
phosphaalkene 1 was treated with (cod)PtCl2 in CH2Cl2 at
ambient temperature. Analysis of the reaction mixture by 31P
NMR spectroscopy revealed that the signals assigned to E/Z-1
[δ ) 260.1 (E), 242.1 (Z)] had been replaced by a new signal
at 205.6 ppm. Importantly, the observation of 195Pt satellites
(1JPtP ) 4486 Hz) provides convincing evidence for coordination
of the phosphorus center to the platinum center. The coupling
constant is similar to other phosphaalkene complexes such as
F‚PtCl2 (1JPtP ≈ 4500 Hz)18,19 but is higher than the monodentate
phosphaalkene in [MesPdCPh2]2PtCl2 (1JPtP ) 3950 Hz20).
Moreover, the downfield 31P NMR chemical shift is consistent
with retention of PdC multiple bond character in the ligand
upon complexation.
(12) See, for example: (a) Ozawa, F.; Ishiyama, T.; Yamamoto, S.;
Kawagishi, S.; Murakami, H.; Yoshifuji, M. Organometallics 2004, 23,
1698. (b) Liang, H.; Ito, S.; Yoshifuji, M. Org. Lett. 2004, 6, 425. (c) Gajare,
A. S.; Toyota, K.; Yoshifuji, M.; Ozawa, F. Chem. Commun. 2004, 1994.
(d) Ozawa, F.; Okamoto, H.; Kawagishi, S.; Yamamoto, S.; Minami, T.;
Yoshifuji, M. J. Am. Chem. Soc. 2002, 124, 10968. (e) Minami, T.;
Okamoto, H.; Ikeda, S.; Tanaka, R.; Ozawa, F.; Yoshifuji, M. Angew. Chem.,
Int. Ed. 2001, 40, 4501. (f) Ozawa, F.; Yamamoto, S.; Kawagishi, S.;
Hiraoka, M.; Ikeda, S.; Minami, T.; Ito, S.; Yoshifuji, M. Chem. Lett. 2001,
972. (g) Ikeda, S.; Ohhata, F.; Miyoshi, M.; Tanaka, R.; Minami, T.; Ozawa,
F.; Yoshifuji, M. Angew. Chem., Int. Ed. 2000, 39, 4512.
(13) A monodentate phosphaalkene [Mes*PdCH(2-MeOC6H4)] and a
P,C,P-chelating phosphaalkene ligand related to H have recently been
employed in Pd-catalyzed Suzuki and Sonogashira coupling reactions.
See: Deschamps, B.; Le Goff, X.; Ricard, L.; Le Floch, P. Heteroat. Chem.
2007, 18, 363.
Although the above NMR spectroscopic evidence suggested
that 2a had been formed from 1 and (cod)PtCl2, this was
(14) van der Sluis, M.; Beverwijk, V.; Termaten, A.; Gavrilova, E.;
Bickelhaupt, F.; Kooijman, H.; Veldman, N.; Spek, A. L. Organometallics
1997, 16, 1144.
(15) Ionkin, A. S.; Marshall, W. J. Heteroat. Chem. 2002, 13, 662.
(16) Jouaiti, A.; Geoffroy, M.; Bernardinelli, G. Tetrahedron Lett. 1992,
33, 5071.
(18) Nakamura, A.; Kawasaki, S.; Toyota, K.; Yoshifuji, M. Chem. Lett.
2004, 33, 1570.
(19) Nakamura, A.; Kawasaki, S.; Toyota, K.; Yoshifuji, M. J. Orga-
nomet. Chem. 2007, 692, 70.
(17) Yam, M.; Chong, J. H.; Tsang, C. W.; Patrick, B. O.; Lam, A. E.;
Gates, D. P. Inorg. Chem. 2006, 45, 5225.
(20) Eshtiagh-Hosseini, H.; Kroto, H. W.; Nixon, J. F.; Maah, M. J.;
Taylor, M. J. J. Chem. Soc., Chem. Commun. 1981, 199.

P,N-Chelate Complexes of Pd(II) and Pt(II)
Organometallics, Vol. 26, No. 25, 2007 6483
Figure 2. Molecular structure of 2b (50% probability ellipsoids).
All hydrogen atoms and the solvent (2CH2Cl2) are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Pd1-P1 )
2.1749(7), P1-C1 ) 1.675(3), C1-C2 ) 1.470(4), C2-N1 )
1.377(4), N1-Pd1 ) 2.076(2), Pd1-Cl1 ) 2.3412(7), Pd1-Cl2
) 2.2834(7), P1-C13 ) 1.789(3); N1-Pd1-P1 ) 81.43(6), P1-
Pd1-Cl2 ) 91.42(3), N1-Pd1-Cl1 ) 95.20(6), Cl1-Pd1-Cl2
) 91.95(3), Pd1-N1-C2 ) 119.96(17), N1-C2-C1 ) 117.6-
(2), C2-C1-P1 ) 112.7(2), C1-P1-Pd1 ) 108.3(1), C1-P1-
C13 ) 116.35(13), Pd1-P1-C13 ) 135.36(9).
Figure 1. Molecular structure of 2a (50% probability ellipsoids).
All hydrogen atoms and the solvent (1/2CH2Cl2) are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Pt1-P1 )
2.1673(11), P1-C10 ) 1.672(4), C10-C17 ) 1.468(5), C17-N1
) 1.373(5), N1-Pt1 ) 2.069(3), Pt1-Cl1 ) 2.2923(11), Pt1-
Cl2 ) 2.3415(11), P1-C1 ) 1.787(4); N1-Pt1-P1 ) 81.17(10),
P1-Pt1-Cl1 ) 94.02(4), N1-Pt1-Cl2 ) 94.80(10), Cl1-Pt1-
Cl2 ) 90.02(4), Pt1-N1-C17 ) 120.3(3), N1-C17-C10 )
117.4(3), C17-C10-P1 ) 112.3(3), C10-P1-Pt1 ) 108.64(14),
C10-P1-C1 ) 116.15(19), Pt1-P1-C1 ) 134.76(13).
identical metrical parameters. Given that related P,N-chelate
complexes of Pt(II) have not been characterized crystallographi-
cally, in this section, emphasis will be placed on comparing 2b
to related Pd(II) compounds from the literature. In both 2a and
2b, a significant shortening of the PdC bond is observed upon
complexation [1.672(4) Å in 2a and 1.675(3) Å in 2b vs 1.7043-
(16) Å in 1].17 In contrast, E (X ) N), F, and G showed no
significant change or even a slight elongation in PdC bond
length upon complexation {i.e., 1.660(11) Å in [E‚Pd(Me)-
(NCMe)]+ vs 1.684(2) Å in E;9 1.653(12) Å in F‚PdCl2 vs
1.667(8) Å in F;22 1.674(4) Å in G‚PdMeCl vs 1.663(3) Å in
G}.14 The palladium-phosphorus bond length in 2b of 2.1749-
(7) Å is similar to those previously observed for phosphaalk-
ene-palladium complexes of E (X ) N) and G [avg ) 2.179(3)
Å].9,14 However, these are slightly shorter than those observed
in F‚PdCl2 [2.267(2) and 2.256(2) Å].22 In addition, the N-Pd
bond length in 2b of 2.076(2) Å is shorter than that for G‚
PdMeCl [2.164(4) Å]14 and that for [E‚Pd(Me)(NCMe)]+
[2.166(8) Å].9
The C-PdC angle increases significantly upon coordination
of 1 to palladium [107.80(7)° in 117 vs 116.15(19)° in 2a and
116.35(13)° in 2b]. Similar increases in C-PdC bond angles
were observed for the palladium complexes of E [X ) N,
104.36(9)° to 113.7(5)°],9 F [99.6(2)° to 114.1(4)°],22 and G
[99.15(14)° to 114.26(19)°].14 The angle between the mean plane
of the six carbon atoms of the Mes substituent and the PdNC2P
plane in 2b is 69°. Not surprisingly, the complexes employing
the bulkier Mes* substituent show angles between the Mes*
and PdNC2P planes that are close to orthogonal {87° in [E‚Pd-
(Me)(NCMe)]+,9 89° in G‚PdMeCl14}.
confirmed by an X-ray crystallographic analysis. Crystals
suitable for X-ray diffraction were grown by cooling a CH2-
Cl2/hexanes solution to -56 °C. The molecular structure is
shown in Figure 1 and confirms that the chelate complex 2a
had been formed successfully (the metrical parameters are
discussed below). Despite repeated recrystallizations, according
to NMR spectroscopy, there were always traces of (cod)PtCl2
present in samples of 2a.
Given our success in the preparation of 2a, we attempted to
prepare the analogous Pd-complex 2b. Under conditions analo-
gous to those described above for 2a, phosphaalkene ligand 1
was treated with (cod)PdCl2 in CH2Cl2. Analysis of the reaction
mixture by 31P NMR spectroscopy revealed a single resonance
at 230.4 ppm. For comparison, lower field chemical shifts were
observed for pyridyl phosphaalkene complexes containing the
bulkier P-Mes* moiety (i.e., G‚PdCl2: R ) H, 247 ppm; R )
SiMe3, 283 ppm).14 In contrast, higher field shifts are observed
for complexes F‚PdCl2 (R ) C4H4S, 149.4 ppm; R ) Fc, 134.9
ppm).18,19,21 Interestingly, the 13C{1H} NMR signal assigned to
the PdC carbon resonates at 174.8 ppm (1JPC ) 52 Hz) for the
complex 2b, which is further upfield than that found for the
1
free phosphaalkene 1 (δ ) 191.3, JPC ) 40 Hz; i.e., ∆δ )
16.5). Similar upfield shifts were observed for the PdCl2
complexes of G‚PdCl2 (R ) SiMe3, ∆δ ) 4.6)14 and the
phosphaalkene signals for complex F‚PdCl2 (R ) -(CH2)5-
;
∆δ ) 16.0 and 14.7).22 Unlike Pt-complex 2a, the Pd-complex
2b is readily obtained in analytical purity after recrystallization.
Molecular Structures of 2a and 2b. The molecular structures
of 2a and 2b are shown in Figures 1 and 2, respectively, and
selected metrical parameters are given in the figure captions.
Details of the solution and refinement are given in Table 1 and
the Supporting Information. Interestingly, the crystal structures
of the palladium(II) and platinum(II) complexes contain almost
Catalytic Activity of 2b. Efforts were then undertaken to
establish any catalytic activity for the phosphaalkene palladium-
(II) complex 2b. An important palladium(II)-catalyzed process
is the rearrangement of allyl trichloroacetimidates (the Over-
man-Claisen rearrangement).23 This process transforms an allyl
(21) Kawasaki, S.; Nakamura, A.; Toyota, K.; Yoshifuji, M. Organo-
metallics 2005, 24, 2983.
(22) Yamada, N.; Abe, K.; Toyota, K.; Yoshifuji, M. Org. Lett. 2002,
4, 569.
(23) For a recent comprehensive review, see: Overman, L. E.; Carpenter,
N. E. In Organic Reactions; Overman, L. E., Ed.; Wiley: Hoboken, NJ,
2005; Vol. 66, pp 1-107.

6484 Organometallics, Vol. 26, No. 25, 2007
Dugal-Tessier et al.
Table 1. X-ray Crystallographic Data for 2a and 2b
may be a consequence of the bulky nature of complex 2b. A
second observation is an overall decrease in the reaction
efficiency when the acetimidate substrate contained an aryl
moiety. For example, compound 3d reacted to produce amide
4d in 48% isolated yield (entry 6). The addition of toluene to
the reaction of 3a also led to a similar decrease in the reaction
efficiency. The inhibitory role of the aromatic additives is not
clear at the present time. Clearly, efforts to expand substrate
scope will necessitate the design of improved phosphaalkene
complexes. Still, these results suggest a useful starting point
for mixed ligand design using a phosphaalkene as a key
structural motif.
2a
2b
formula
fw
C
21H20NPPtCl2‚1/2CH2Cl2
C
21H20NPPdCl4‚2CH2Cl2
625.80
664.50
cryst syst
space group
color
triclinic
P1h
yellow
triclinic
P1h
orange
a (Å)
b (Å)
c (Å)
9.8721(7)
10.2072(7)
12.0467(8)
105.168(6)
108.919(6)
95.834(6)
1085(1)
173
9.8650(3)
11.7091(4)
12.5723(5)
86.292(1)
88.685(1)
69.904(1)
1360.96(8)
173
R (deg)
â (deg)
γ (deg)
V (Å3)
T (K)
Z
2
2
µ(Mo KR) (cm-1
cryst size (mm3)
)
69.17
13.43
Summary
0.35 × 0.20 × 0.12
0.07 × 0.07 × 0.12
calcd density (Mg m-3
2θ(max) (deg)
no. of reflns
) 1.916
1.622
In closing, we have prepared two new palladium(II) and
platinum(II) complexes bearing P(sp2)-N(sp2) ligands. The
phosphaalkene-based ligand bears moderately bulky mesityl
substituent. Both compounds were characterized spectroscopi-
cally and through X-ray crystallographic analysis. As a proof
of concept, the potential use of this ligand class in catalysis
was demonstrated by showing that compound 2b was effective
in the Overman-Claisen rearrangement. Future work is under-
way in efforts to modify the steric and electronic properties of
the ligand and to explore the scope and effectiveness of these
complexes in a variety of catalytic processes.
55.2
11 319
55.8
22 108
no. of unique data
R(int)
4068
0.025
15.41
0.026; I > 2σ(I)
0.065
1.09
6431
0.031
18.48
0.037; I > 2σ(I)
0.097
1.03
refln/param ratio
a
R1
wR2 (all data)b
GOF
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2(F2[all data]) ) {∑[w(Fo - Fc )2]/
2
2
2
∑[w(Fo )2]}1/2
.
Table 2. Results of the aza-Claisen Rearrangement Using 2b
as Catalyst
Experimental Section
General Procedures. All manipulations of air- and/or water-
sensitive compounds were performed under a nitrogen atmosphere
using standard Schlenk or glovebox techniques. Hexanes and CH2-
Cl2 were deoxygenated with nitrogen and dried by passing through
a column containing activated alumina. 230-400 mesh silica was
used (Silicycle). The complexes (cod)PtCl2 and (cod)PdCl2 were
prepared according to literature procedures.24,25 Trichloroacetonitrile,
1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), crotyl alcohol, and
trans-2-hexen-1-ol were used as received from Aldrich. Other
starting materials were prepared according to the literature proce-
dures, which are cited below. 1H, 31P, 13C{1H} NMR spectra were
recorded at room temperature on Bruker Avance 300 or 400 MHz
spectrometers. 85% H3PO4 was used as an external standard (δ )
0.0 for 31P). 1H NMR spectra were referenced to residual protonated
solvent, and 13C NMR spectra were referenced to the deuterated
solvent. Elemental analyses were performed in the University of
British Columbia Chemistry Microanalysis Facility. Mass spectra
were recorded on a Kratos MS 50 instrument in EI mode (70 eV).
Melting points are uncorrected.
MesPC(Ph)(Py)PtCl2 (2a). This procedure was performed in a
glovebox. To a mixture of (cod)PtCl2 (75 mg, 0.20 mmol) and 117
(65 mg, 0.20 mmol) was added 1 mL of CH2Cl2. The resulting
dark red solution was stirred for 15 min. Cooling of the reaction
mixture to -56 °C with slow addition of 1 mL of hexanes gave
yellow crystals. The mother liquor was decanted, and the crystals
were washed with hexanes (3 × 1 mL). Recrystallization (CH2-
Cl2/hexanes, twice) followed by drying in vacuo for 6 h gave 41
mg (37%) of the title compound as a solid.
entry
substrate
R1
2b (mol %)
yield (%)a
1
2
3
4
5
6
7
3ab
3ac
3ac
3bc
3cc
3dc
3ec
Me
Me
Me
n-Pr
5
0
5
5
5
5
5
91
0
84
86
72
48
33
n-Hep
PhCH2CH2
i-Pr
a Isolated yield. b Purified by distillation. c Purified by column chroma-
tography.
alcohol to an allyl amine derivative in concert with a 1,3-allylic
transposition. For two principal reasons, this process was
deemed to be a useful starting point to examine the potential
catalytic reactivity of these complexes. First, the mechanism
of the Overman-Claisen rearrangement does not involve
changes in the palladium oxidation state, simplifying the overall
reaction path. Second, the starting materials for these processes
are trivial to obtain.
To our delight, subjecting acetimidate 3a with 5 mol % of
2b in CH2Cl2 at 35 °C for 24 h led to the production of branched
amide 4a in 91% isolated yield (Table 2, entry 1). Importantly,
no background reaction was observed when the reaction was
run in the absence of complex 2b (entry 2). Reactions run with
substrate that was not previously purified in any manner tended
to be messy, which is presumably a consequence of the
sensitivity of 2b. Purification of the starting material using either
distillation (entry 1) or standard silica gel column chromatog-
raphy (entry 3) gave satisfactory results. Interestingly, the
reaction proceeds optimally using acetimidate starting materials
possessing linear aliphatic chains (entries 4-6). Substrates
containing branched aliphatic groups reacted, although the
products were obtained in less satisfactory isolated yield (entry
7). We speculate that the lower yields with bulky substrates
31P NMR (121.3 MHz, CDCl3): δ 205.6 (1JPtP ) 4486 Hz). 1H
3
3
NMR (300 MHz, CDCl3): δ 10.34 (dd, JHH ) 6 Hz, JHH ) 1
3
Hz, JPtH ) 36 Hz, 1H), 7.87-7.79 (m, 1H), 7.50-7.44 (m, 1H),
3
7.41-7.27 (m, 4H), 7.11-7.08 (m, 2H), 6.90 (d, JHH ) 4 Hz,
2H), 2.54 (s, 3H), 2.53 (s, 3H), 2.28 (s, 3H).
(24) Drew, D.; Doyle, J. R. Inorg. Synth. 1990, 28, 346.
(25) McDermott, J. X.; White, J. F.; Whitesides, G. M. J. Am. Chem.
Soc. 1976, 98, 6521.

P,N-Chelate Complexes of Pd(II) and Pt(II)
Organometallics, Vol. 26, No. 25, 2007 6485
MesPC(Ph)(Py)PdCl2 (2b). This procedure was performed in
a glovebox. To a mixture of (cod)PdCl2 (100 mg, 0.35 mmol) and
117 (111 mg, 0.35 mmol) was added 1 mL of CH2Cl2. The resulting
dark red solution was stirred for 15 min. Cooling the reaction
mixture to -56 °C with slow addition of 1 mL of hexanes gave
orange crystals. The mother liquor was decanted, and the crystals
were washed with hexanes (3 × 3 mL) and dried in vacuo at
100 °C for 6 h to give 91 mg (53%) of the title compound as orange
crystals.
chromatography (5% ethyl acetate:95% hexanes) gave 1.85 g (68%)
of a colorless oil. The spectroscopic data for the title compound
were identical to the literature.30
1-(1-Imino-2,2,2-trichloroethoxy)-2(E)-4-methyl-pentene (3e).
(E)-4-Methyl-2-penten-1-ol31 (0.36 g, 3.6 mmol) was processed as
outlined in the general procedure. Purification using column
chromatography (5% ethyl acetate:95% hexanes) gave 0.66 g (75%)
of a colorless oil.
1H NMR (400 MHz, CDCl3): δ 8.35-8.20 (br s, 1H), 5.84 (dd,
3
3
3
3JHH ) 16 Hz, JHH ) 6 Hz, 1H), 5.63 (dt, JHH ) 16 Hz, JHH
)
31P NMR (121.3 MHz, CDCl3): δ 230.4 (s). 1H NMR (300 MHz,
3
3
3
3
6 Hz, 1H), 4.75 (d, JHH ) 6 Hz, 2H), 2.35 (sept, JHH ) 7 Hz,
CDCl3): δ 10.03 (d, JHH ) 6 Hz, 1H), 7.86 (dd, JHH ) 4 Hz,
3JHH ) 2 Hz, 1H), 7.48-7.44 (m, 1H), 7.39-7.24 (m, 4H), 7.07
(d, 3JHH ) 8 Hz, 2H), 6.85 (d, 3JHH ) 4 Hz, 2H), 2.50 (s, 3H), 2.50
(s, 3H), 2.25 (s, 3H). 13C{1H} NMR (75 MHz, CD2Cl2): δ 174.8
3
1H), 1.02 (d, JHH ) 7 Hz, 6H). 13C{1H} NMR (100 MHz,
CDCl3): δ 162.8, 143.8, 120.3, 91.7, 70.3, 31.0, 22.1. IR (neat,
NaCl): 3344, 1663, 1290 cm-1. MS (EI): m/z [%] 244 [36, M+ -
H], 242 [37, M+ - H].
(d, JPC ) 52 Hz), 163.0, 159.7 (d, JPC ) 14 Hz), 155.2 (d, JPC
)
Palladium(II)-Catalyzed Overman-Claisen Rearrangement
(General Procedure). This procedure was performed in a glovebox.
To a mixture of 2b (0.05 equiv) and trichloroacetimidate (1 equiv)
was added 2 mL of CH2Cl2. The reaction mixture was stirred for
24 h. The reaction mixture was removed from inert atmosphere
and chromatographed directly on silica gel to afford the trichloro-
acetamide product.
2,2,2-Trichloro-N-(1-methylallyl)acetamide (4a). 3a (96 mg,
0.44 mmol) and 2b (10 mg, 0.02 mmol) were processed as outlined
in the general procedure. Purification using column chromatography
(5% ethyl acetate:95% hexanes) gave 87 mg (91%) of a white solid,
mp ) 37-39 °C (lit. 37-38 °C32). The spectral data for the title
compound matched the literature data.30
2,2,2-Trichloro-N-(1-propylallyl)acetamide (4b). 3c (98 mg,
0.40 mmol) and 2b (10 mg, 0.02 mmol) were processed as outlined
in the general procedure. Purification using column chromatography
(5% ethyl acetate:95% hexanes) gave 84 mg (86%) of a colorless
oil. The spectral data for the title compound matched the literature
data.30
5 Hz), 145.8 (d, JPC ) 3 Hz), 144.0 (d, JPC ) 5 Hz), 140.8 (d, JPC
) 5 Hz), 134.4 (d, JPC ) 13 Hz), 130.3, 129.6, 129.3 (d, JPC ) 10
Hz), 128.4 (d, JPC ) 14 Hz), 125.9 (d, JPC ) 9 Hz), 124.0 (d, JPC
) 25 Hz), 120.2 (d, JPC ) 38 Hz), 23.5, 23.4, 21.9. Anal. Calcd
for C21H20NPdCl2: C, 50.99; H, 4.08; N, 2.83. Found: C, 51.12;
H, 4.21; N, 2.80.
Trichloroacetimidate Formation (General Procedure). To a
solution of allylic alcohol (1 equiv) in CH2Cl2 (0.1 M) at 0 °C
were added trichloroacetonitrile (1.5 equiv) and then DBU (0.2
equiv) dropwise. The reaction mixture was stirred at 0 °C for 1 h.
The reaction was quenched by the addition of a saturated aqueous
solution of sodium bicarbonate. The organic and aqueous fractions
were separated, and the aqueous phase was extracted twice with
CH2Cl2. The combined organic extracts were dried (sodium sulfate)
and concentrated by rotary evaporation in vacuo. Further purifica-
tion of the crude material using flash column chromatography on
silica gel was typically necessary.
1-(1-Imino-2,2,2-trichloroethoxy)-2(E)-butene (3a). Crotyl al-
cohol (1.10 g, 15.3 mmol) was processed as outlined in the general
procedure. Purification using column chromatography (5% ethyl
acetate:95% hexanes) gave 2.85 g (86%) of a colorless oil. The
spectroscopic data for the title compound were identical to the
literature.26
1-(1-Imino-2,2,2-trichloroethoxy)-2(E)-hexene (3b). (E)-2-
Hexen-1-ol (1.14 g, 11.3 mmol) was processed as outlined in the
general procedure. Purification using column chromatography (5%
ethyl acetate:95% hexanes) gave 2.05 g (74%) of a colorless oil.
The spectroscopic data for the title compound were identical to
the literature.27
2,2,2-Trichloro-N-(1-heptylallyl)acetamide (4c). 3c (143 mg,
0.47 mmol) and 2b (12 mg, 0.024 mmol) were processed as outlined
in the general procedure. Purification using column chromatography
(1% ethyl acetate:99% hexanes) gave 103 mg (72%) of a colorless
oil.
1H NMR (300 MHz, CDCl3): δ 6.55-6.45 (br s, 1H), 5.79 (ddd,
3
3
3JHH ) 17 Hz, JHH ) 11 Hz, JHH ) 6 Hz, 1H), 5.28-5.22 (m,
2H), 4.45-4.35 (m, 1H), 1.69-1.56 (m, 2H), 1.40-1.20 (m, 10H),
0.88 (t, JHH ) 7 Hz, 3H). 13C{1H} NMR (75 MHz, CDCl3): δ
3
161.1, 136.7, 116.0, 92.9, 53.5, 34.5, 31.7, 29.2, 29.1, 25.5, 22.6,
14.0. IR (neat, NaCl): 3423, 1694, 1519 cm-1. MS (EI): m/z [%]
301 [8, M+], 299 [9, M+], 266 [15, M+ - Cl], 264 [23, M+ - Cl],
202 [70, M+ - C7H15], 200 [100, M+ - C7H15]. Anal. Calcd For
C12H20Cl3NO: C, 47.94; H, 6.71; N, 4.66. Found: C, 47.63; H,
6.50; N, 5.05.
2,2,2-Trichloro-N-(1-(2-phenylethyl)-allyl)acetamide (4d). 3d
(160 mg, 0.52 mmol) and 2b (13 mg, 0.027 mmol) were processed
as outlined in the general procedure. Purification using column
chromatography (2% ethyl acetate:98% hexanes) gave 76 mg (48%)
of the title compound as a colorless oil. The spectral data for the
title compound matched the literature data.33
1-(1-Imino-2,2,2-trichloroethoxy)-2(E)-decene (3c). (E)-2-De-
cen-1-ol28 (2.67 g, 17.1 mmol) was processed as outlined in the
general procedure. Purification using column chromatography (2%
ethyl acetate:98% hexanes) gave 3.84 g (75%) of a colorless oil.
1H NMR (300 MHz, CDCl3): δ 8.32-8.20 (br s, 1H), 5.87 (dt,
3JHH ) 15 Hz, 3JHH ) 7 Hz, 1H), 5.66 (dtt, 3JHH ) 15 Hz, 3JHH
)
6 Hz, 4JHH ) 1 Hz, 1H), 4.72 (dd, 3JHH ) 6 Hz, 4JHH ) 1 Hz, 2H),
3
3
2.05 (q, JHH ) 7 Hz, 2H), 1.4-1.2 (m, 10H), 0.86 (t, JHH ) 7
Hz, 3H). 13C{1H} NMR (75 MHz, CDCl3): δ 162.5, 137.0, 122.9,
91.5, 69.9, 32.2, 31.8, 29.1, 29.0, 28.8, 22.6, 14.0. IR (neat,
NaCl): 3347, 1663, 1290 cm-1. MS (EI): m/z [%] 301 [33, M+],
299 [36, M+], 266 [48, M+ - Cl], 264 [71, M+ - Cl], 216 [85,
M+ - C6H13], 214 [84, M+ - C6H13], 202 [96, M+ - C7H15], 200
[100, M+ - C7H15].
2,2,2-Trichloro-N-(1-isopropylallyl)acetamide (4e). 3e (196
mg, 0.80 mmol) and 2b (20 mg, 0.04 mmol) were processed as
outlined in the general procedure. Purification using column
chromatography (2% ethyl acetate:98% hexanes) gave 65 mg (33%)
of the title compound as a white solid, mp ) 42-43 °C.
1H NMR (400 MHz, CDCl3): δ 6.73-6.51 (br s, 1H), 5.80 (ddd,
1-(1-Imino-2,2,2-trichloroethoxy)-2(E)-5-phenyl-pentene (3d).
(E)-5-Phenyl-2-penten-1-ol29 (1.43 g, 8.8 mmol) was processed as
outlined in the general procedure. Purification using column
3
3
3JHH ) 17 Hz, JHH ) 10 Hz, JHH ) 6 Hz, 1H), 5.25-5.19 (m,
(26) Overman, L. E. J. Am. Chem. Soc. 1976, 98, 2901.
(27) Bongini, A.; Cardillo, G.; Orena, M.; Sandri, S.; Tomasini, C. J.
Org. Chem. 1986, 51, 4905.
(28) Federici, C.; Righi, G.; Rossi, L.; Bonini, C.; Chiummiento, L.;
Funicello, M. Tetrahedron Lett. 1994, 35, 797.
(29) Charette, A. B.; Molinaro, C.; Brochu, C. J. Am. Chem. Soc. 2001,
123, 12168.
(30) Anderson, C. E.; Overman, L. E. J. Am. Chem. Soc. 2003, 125,
12412.
(31) Wardrop, D. J.; Bowen, E. G. Chem. Commun. 2005, 5106.
(32) Cramer, F.; Hennrich, N. Chem. Ber. 1961, 94, 976.
(33) Kirsch, S. F.; Overman, L. E.; Watson, M. P. J. Org. Chem. 2004,
69, 8101.

6486 Organometallics, Vol. 26, No. 25, 2007
Dugal-Tessier et al.
3
2H), 4.31-4.28 (m, 1H), 1.93 (sept, JHH ) 7 Hz, 1H), 0.97 (d,
Compound 2b crystallizes with two disordered molecules of
dichloromethane in the asymmetric unit. Additional crystal data
and details of the data collection and structure refinement are given
in Table 1. Further details are included in the Supporting Informa-
tion.
3JHH ) 7 Hz, 3H), 0.95 (d, 3JHH ) 7 Hz, 3H). 13C{1H} NMR (100
MHz, CDCl3): δ 161.4, 135.3, 116.9, 93.1, 58.9, 32.2, 18.9, 18.0.
IR (neat, NaCl): 3301, 1690, 1530 cm-1. MS (EI): m/z [%] 245
[16, M+], 243 [17, M+], 202 [97, M+ - C3H7], 200 [100, M+
-
C3H7].
X-ray Crystallography. All single crystals were immersed in
oil and mounted on a glass fiber. Data were collected on a Rigaku/
ADSC CCD diffractometer 2a or a Bruker X8 APEX diffractometer
2b with graphite-monochromated Mo KR radiation. All structures
were solved by direct methods and subsequent Fourier difference
techniques. All non-hydrogen atoms were refined anisotropically
with hydrogen atoms being included in calculated positions but not
refined. All data sets were corrected for absorption effects (Twin-
Solve for 2a, SADABS for 2b), Lorentz, and polarization effects.
All calculations on crystal 2a were performed using SHELXL-97,34
whereas all refinement of 2b was performed using the SHELXTL35
crystallographic software package from Bruker-AXS. Compound
2a crystallizes with one disordered half molecule of dichlo-
romethane residing on an inversion center in the asymmetric unit.
Acknowledgment. This work was supported by the Natural
Sciences and Engineering Research Council (NSERC) of
Canada, the Canada Foundation for Innovation (CFI), and the
British Columbia Knowledge Development Fund (BCKDF).
J.D.-T. is grateful for Laird and University Graduate Scholar-
ships. We thank Dr. Brian O. Patrick for determining the crystal
structures.
Note added in proof: Since this manuscript was accepted
an article detailing the use of ligands of type H (Chart 1) in
catalyzed conjugate addition reactions. See: Hayashi, A.;
Okazaki, M.; Okawa, F. Organometallics 2007, 26, 5246.
Supporting Information Available: Full details of the crystal
structure investigation (CIF). This material is available free of
charge via the Internet at http://pubs.acs.org.
(34) Sheldrick, G. M. SHELXL-97. Programs for Crystal Structure
Analysis (Release 97-2); University of Go¨ttingen: Germany, 1997.
(35) SHELXTL Version 5.1; Bruker, ZSX Inc.: Madison, WI, 1997.
OM700784X