Insertion of sulfur dioxide into metal-carbon bonds of chloro(methyl)palladium complexes

Article abstract of DOI:10.1016/S0277-5387(02)01377-3

Five chloro(methyl)palladium complexes (L-L)Pd(Me)Cl have been shown to react with SO₂ in solution to form S-sulfinato complexes of the formula (L-L)Pd(SO₂Me)Cl (L-L = dippf = 1, 1′-bis(diisopropylphosphino)ferrocene (2), dppf = bis(

Full text of DOI:10.1016/S0277-5387(02)01377-3

Polyhedron 22 (2003) 805ꢁ810
/
www.elsevier.com/locate/poly
Insertion of sulfur dioxide into metalÃ
/
carbon bonds of
chloro(methyl)palladium complexes
Kelin Li a, Ilia A. Guzei b, James Darkwa a,*
a Department of Chemistry, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa
b Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
Received 7 October 2002; accepted 21 November 2002
Abstract
Five chloro(methyl)palladium complexes (LÃ
complexes of the formula (LÃL)Pd(SO2Me)Cl (LÃ
phosphino)ferrocene (3), dppeꢀ
1,1?-bis(diphenylphosphino)ethane (4), COD (5) and (3,5-dit Bupz)2 (6)). Compounds 5 and 6 are
/
L)Pd(Me)Cl have been shown to react with SO2 in solution to form S-sulfinato
/
/
Lꢀdippfꢀ1,1?-bis(diisopropylphosphino)ferrocene (2), dppfꢀbis(diphenyl-
/
/
/
/
unstable in solution and slowly decompose. Representative crystal structures of (dippf)Pd(Me)Cl (1) and (dppf)Pd(SO2Me)Cl (3) are
reported.
# 2002 Published by Elsevier Science Ltd.
Keywords: Palladium complexes; Insertion; Sulfur dioxide; Crystal structures
1. Introduction
reveal the instability of their insertion products.
Whereas the reaction of SO2 with chloro(methyl)iridium
complex led to several unidentified insertion compounds
[8], the chloro(methyl)platinum complex did not form
the expected product, (dcpe)Pt(SO2Me)Cl, and instead
(dcpe)Pt(SO2Me)Me and (dcpe)PtCl2 were formed [9].
The lack of a single insertion product for Cp*Ir(PMe3)-
(Me)Cl is attributed to the instability of Cp*Ir(PMe3)-
(Me)Cl, which disproportionates to Cp*Ir(PMe3)(Me)2
and Cp*Ir(PMe3)Cl2 [8]. On the other hand, (dcpe)Pt-
(Me)Cl does not disproportionate but the expected SO2
insertion product, (dcpe)Pt(SO2Me)Cl, is believed to be
unstable; leading to the disproportionation products,
(dcpe)Pt(SO2Me)Me and (dcpe)PtCl2 [9].
There are three main reaction types between metal
complexes and sulfur dioxide. The first type involves
sulfur dioxide binding to the metal center [1]. The
second type is sulfur dioxide binding to a ligand in the
metal complex [2] and the third is insertion of sulfur
dioxide into a metalÃ
/
hydrogen [1b], metalÃ
/
carbon [3] or
metalÃ
/
metal bonds [4]. Insertion into a metalÃ
/carbon
bond is observed predominantly for the late transition
metals, notably Group 8 metals. The first report on the
SO2 insertion into a metalÃ
and Wojcicki for the FeÃ
(CO)2(R) to form the S-sulfinato products (h5-
CH3, CH2CH3) [5]. Since
/
carbon bond was by Bibler
/
C bond in (h5-C5H5)Fe-
We have investigated the stability of SO2 insertion
products of five chloro(methyl)palladium complexes
with different ligands, to test how ancillary ligands
affect the stability of insertion products. The results of
this study are reported in this paper.
C5H5)Fe(CO)2(SO2R) (RÄ
/
then a number of S-sulfinato metal complexes have
been prepared by this route [3,6]. Insertion of SO2 into a
PdÃ
produces
C5H5)Pd(PPh3)(SO2R) (RÄ
reports by Jones and coworkers on reactions between
Cp*Ir(PMe3)(Me)Cl (Cp*ꢀ
h5-C5(CH3)5) [8] and
(dcpe)Pt(Me)Cl (dcpeꢀCy2PC2H4PCy2) [9] and SO2
/
C bond reported by Turner and Felkin in 1976
similar S-sulfinato products
(h5-
Me, Ph) [7]. The most recent
/
2. Experimental
/
/
All manipulations were performed under a dry
nitrogen atmosphere using standard Schlenk techniques.
NMR spectra were recorded on a Gemini 2000 instru-
* Corresponding author
0277-5387/02/$ - see front matter # 2002 Published by Elsevier Science Ltd.
doi:10.1016/S0277-5387(02)01377-3

806
K. Li et al. / Polyhedron 22 (200£) 805ꢁ810
/
ment (1H at 200 MHz, 13C{1H} at 50.3 MHz). The
chemical shifts are reported in d (ppm) referenced to
residual protons and 13C signals of deuterated CHCl3 as
internal standard. (COD)Pd(Me)Cl [10], (3,5-dit-
Bupz)2Pd(Me)Cl [11], (dppf)Pd(Me)Cl [12], (dppe)Pd-
(Me)Cl [12] were prepared by literature methods. Sulfur
2.4. (dppe)Pd(SO2Me)Cl (4)
Yield: 60%. Anal. Calc. for C27H27ClO2P2PdS: C,
1
52.36; H, 4.39. Found: C, 52.10; H, 4.50%. H NMR
(CDCl3): d 7.80 (m, 8H, Ph); 7.53 (m, 12H, Ph); 2.74 (s,
3H, Ã
/
SO2Me); 2.61 (s, br, 2H, CH2); 2.10 (s, br, 2H,
CH2). 13C{1H} NMR (CDCl3): d 133.7, 133.4, 132.9,
129.6, 129.3, 127.0, 125.9, 40.2, 28.6, 28.3, 27.5, 27.3.
dioxide (99.9ꢂ
/
%) was obtained from Aldrich and used
as received. Elemental analyses were performed in-house
at the Department of Chemistry, University of the
Western Cape.
2.5. (3,5-ditBupz)2Pd(SO2Me)Cl (5)
Yield: 55%. Anal. Calc. for C23H43ClN4O2P2PdS: C,
47.50; H, 7.45; N, 9.63. Found: C, 47.20; H, 7.10; N,
2.1. (dippf)Pd(Me)Cl (1)
1
10.05%. H NMR (CDCl3): d 6.06 (s, 2H, pz); 3.12 (s,
3H, Ã
/
SO2Me); 1.37 (s, 36H, tBu). 13C{1H} NMR
(CDCl3): d 146.8, 132.5, 122.5, 43.8, 40.6, 16.8, 14.9.
This compound was prepared by a similar procedure
as reported for (dppf)Pd(Me)Cl [11]. Yield: 51%. Anal.
Calc. for C23H39ClFeP2Pd: C, 48.03; H, 6.83. Found: C,
1
2.6. (COD)Pd(SO2Me)Cl (6)
47.90; H, 6.55%. H NMR (CDCl3): d 4.37 (s, br, 8H,
C5H4); 2.67 (m, 2H, iPr); 2.41 (m, 2H, iPr); 1.48 (dd, 6H,
iPr, 2JHH
(dd, 3H, PdÃ
ꢀ
/
15.9, 3JPH
ꢀ
ꢀ
/
7.3 Hz); 1.20 (m, 18H, iPr); 0.90
A slow stream of SO2 was bubbled through a CH2Cl2
(15 ml) solution of (COD)Pd(Me)Cl (0.30 g, 1.15 mmol)
for 15 min. The colourless solution turned yellow and
the reaction mixture was kept under SO2 pressure and
stirred for 18 h. Upon addition of SO2 saturated C6H14,
the solution gradually deposited yellow microcrystalline
(COD)Pd(SO2Me)Cl. Yield: 0.26 g, 70%. Anal. Calc. for
C9H15ClO2PdS: C, 32.80; H, 4.59. Found: 33.25; H,
4.41%. 1H NMR (CDCl3): d 6.18 (s, br, 2H, COD); 5.97
(s, br, 2H, COD); 3.22 (s, 3H, SO2Me); 2.89 (m, 4H,
COD); 2.71 (m, 4H, COD). 13C{1H} NMR (CDCl3): d
126.3, 118.7, 30.6, 28.5, 26.0.
3
Me, JPH
3
6.9, JPH
/
/
ꢀ
2.9 Hz). 13C{1H}
/
NMR (CDCl3): d 73.3, 73.2, 72.9, 72.8, 71.0, 70.9, 70.6,
70.5, 26.0, 25.5, 25.4, 25.2, 20.9, 20.7, 19.6, 19.5, 19.4,
19.3, 8.5, 8.4, 6.5, 6.4.
2.2. (dippf)Pd(SO2Me)Cl (2)
Sulfur dioxide was bubbled through a CH2Cl2 (15 ml)
solution of (dippf)Pd(Me)Cl (0.20 g, mmol) for 15 min.
The yellow solution turned red. Addition of C6H14,
saturated with SO2, gave analytically pure crystalline
(dippf)Pd(SO2Me)Cl. Yield: 0.14 g, 65%. Anal. Calc. for
C23H39ClFeO2P2PdS: C, 43.21; H, 6.15. Found: C,
2.7. X-ray structural determination for 1 and 3
Crystal evaluation and data collection were per-
formed on a Bruker CCD-1000 diffractometer with
˚
1
42.85; H, 6.20%. H NMR (CDCl3): d 4.55 (s, br, 8H,
C5H4); 3.52 (m, 2H, iPr); 3.13 (s, 3H, Ã
/
SO2Me); 2.95 (m,
i
Mo Ka (lꢀ
/
0.71073 A) radiation and the diffractometer
i
i
2H, Pr); 1.64 (m, 2H, Pr); 1.05ꢁ1.25 (m, 2H, Pr).
/
to crystal distance of 4.9 cm (Table 1). The initial cell
constants were obtained from three series of v scans at
different starting angles. The reflections were success-
fully indexed by an automated indexing routine built in
the SMART program. The absorption correction was
based on fitting a function to the empirical transmission
surface as sampled by multiple equivalent measurements
[13]. The structures were solved by direct methods and
refined by least-squares techniques using SHELXTL
program [14]. All non-hydrogen atoms were refined
with anisotropic displacement coefficients. All hydrogen
atoms were included in the structure factor calculation
at idealized positions and were allowed to ride on the
neighbouring atoms with relative isotropic displacement
coefficients. Complex 1 occupies a crystallographic
twofold axis; consequently, the chloride and methyl
groups are equally disordered over the twofold axis.
There was also one severely disordered molecule of
CH2Cl2 present in the asymmetric unit of 3. A sig-
13C{1H} NMR (CDCl3): d 73.5, 73.3, 73.0, 72.9, 71.2,
71.0, 70.8, 70.6, 31.0, 26.2, 25.7, 25.4, 25.2, 20.9, 20.7,
19.6, 19.5, 19.3, 8.5, 8.4, 6.5, 6.4.
A similar procedure as used for complex 2 was
followed to prepare complexes 3, 4 and 5.
2.3. (dppf)Pd(SO2Me)Cl (3)
Single crystals suitable for X-ray analysis were
obtained by layering a CH2Cl2 solution of 3 with SO2
saturated C6H14 at ꢃ
/
15 8C. Yield: 69%. Anal. Calc. for
C35H31ClFeO2P2PdS×
/
CH2Cl2: C, 50.26; H, 3.87. Found:
1
C, 50.40; H, 3.54%. H NMR (CDCl3): d 7.82 (m, 4H,
Ph); 7.39 (m, 6H, Ph); 4.70 (s, br, 2H, C5H4); 4.51 (s, br,
2H, C5H4); 4.25 (s, br, 2H, C5H4); 3.56 (s, br, 2H,
C5H4); 2.98 (s, 3H, Ã
/
SO2Me). 13C{1H} NMR (CDCl3):
d 134.7, 131.5, 131.0, 75.3, 74.1, 73.3, 71.6, 31.7.

K. Li et al. / Polyhedron 22 (200£) 805ꢁ
/
810
807
Table 1
Crystal data and structure refinement for complexes 1 and 3
Empirical formula
Formula weight
Temperature (K)
C
23H39ClFeP2Pd
C35H31ClFeO2P2PdS×CH2Cl2
/
575.18
100(2)
0.71073
orthorhombic
Pnna
860.22
173(2)
0.71073
monoclinic
P21/c
˚
Wavelength (A)
Crystal system
Space group
˚
a (A)
15.8149(7)
17.0533(8)
8.9562(4)
90
9.5395(10)
20.568(2)
18.9395(17)
90
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
Volume (A )
Z
Dcalc (Mg mꢃ3
90
90
92.590(2)
90
3
˚
2415.45(19)
4
1.582
3712.3(6)
4
1.539
)
Absorption coefficient (mmꢃ1
F(000)
)
1.596
1184
1.264
1736
Crystal size (mm)
u Range (8)
Index ranges
0.40ꢄ
2.57ꢁ26.38
195h 5
17 546
/
0.20ꢄ
/
0.20
19, ꢃ215
0.0299]
0.40ꢄ
1.46ꢁ26.37
115h 5
23 917
/
0.31ꢄ
/
0.15
11, 05
0.0388]
/
/
ꢃ/
/
/
/
/
k 5
/
21, ꢃ
/
115
/
l 5
/
11
ꢃ/
/
/
/
k 5
/
25, 05
/
l 523
/
Reflections collected
Independent reflections
2463 [Rint
99.6%
ꢀ
/
7408 [Rint
97.8%
ꢀ
/
Completeness to uꢀ
/26.378
Absorption correction
Max./min. transmission
Refinement method
empirical with SADABS
0.7408, 0.5677
full-matrix least-squares on F2
2463/2/137
empirical with SADABS
0.8330, 0.6317
full-matrix least-squares on F2
7408/0/393
Data/restraints/parameters
Final R indices [I ꢀ
R indices (all data)
Goodness-of-fit on F2
Largest difference peak and hole (e A
/
2s(I)]
R1ꢀ
R1ꢀ
1.005
0.678 and ꢃ
/
0.0325, wR2ꢀ
/
0.0960
R1ꢀ
R1ꢀ
1.049
1.306 and ꢃ0.498
/
0.0361, wR2ꢀ
/
0.0900
0.0953
/0.0357, wR2ꢀ
/
0.0988
/
0.0528, wR2ꢀ
/
ꢃ3
˚
)
/0.438
/
nificant amount of time was invested in refining the
disordered molecule. Bond length restraints were ap-
plied to model that molecule but the resulting isotropic
displacement coefficients suggested the molecules were
mobile. In addition, the refinement was computationally
unstable. Option SQUEEZE of programme PLATON [15]
was used to correct the diffraction data for diffuse
scattering effects and to identify the solvate molecule.
the Pd and Fe atoms. This results in an 50:50 occupancy
of the methyl and Cl groups. The Pd is at the centre of a
distorted square-planar geometry. The largest deviation
from square-planarity is found in the PÃ
/
PdÃ
/
P bite angle
of 104.74(3)8, which is larger than bite angles in other
(dippf)Pd complexes ((dippf)Pd(SC6H5)2 (101.09(2)8)
[16],
(dippf)Pd(SC6H4S-o)
(102.44(3)8),
3. Results and discussions
3.1. Synthesis of (dippf)PdMeCl (1)
The reaction of (COD)PdMeCl with 1 equiv. of 1,1?-
bis(diisopropylphosphino)ferrocene (dippf) in CH2Cl2
at room temperature for 8 h afforded (dippf)PdMeCl as
a yellow solid in only moderate yield. Complex 1 is very
stable in both solution and solid-state. The methyl
protons in 1 appear as doublet of a doublet at 0.90
ppm, the result of coupling with the two phosphorus
atoms. The solid-state structure of 1 was determined by
X-ray crystallography and shown in Fig. 1 with selected
bond distances and angles in Table 2. The structure of 1
has a twofold crystallographic axis that passes through
Fig. 1. ORTEP diagram of (dippf)Pd(Me)Cl.

808
K. Li et al. / Polyhedron 22 (200£) 805ꢁ810
/
Table 2
˚
Selected bond lengths (A) and angles (8) for complex 1
Bond lengths
PdÃ
PdÃ
/
P(1)
Cl(1)
2.3339(7)
PdÃ
/
C(12)
C(1)
2.051(2)
1.813(3)
/
2.3398(11) P(1)Ã
/
Bond angles
P(1)ÃPdÃCl(1)
C(12)#1ÃPdÃP(1)
P(1)ÃPdÃCl(1)#1
/
/
87.28(8)
167.9(5)
167.53(9)
P(1)Ã
C(12)Ã
C(12)Ã
/
PdÃ
PdÃ
PdÃ
/
P(1)#1
104.74(3)
82.7(4)
85.7(5)
/
/
/
/Cl(1)#1
/
/
/
/P(1)
(dippf)Pd(SC6H3MeS-o) (101.88(3)8) [17]). Similar to
the PdÃP distances in (dippf)Pd(SC6H5)2 (2.3303(6) and
2.3463(7) A) [16], (dippf)Pd(SC6H4S-o) (2.3364(10) and
/
˚
˚
2.3433(8) A) and (dippf)Pd(SC6H3MeS-o) (2.3291(9)
˚
and 2.3329(8) A) [17], the PdÃ
/
P
distance in
1
P
˚
(2.3339(7) A) is slightly longer than ‘normal’ PdÃ
/
˚
bond (2.29(5) A) in average PdÃ
/P bond distances in
Fig. 2. ORTEP diagram of (dppf)Pd(SO2Me)Cl.
2422 such distances in complexes in the Cambridge
Structural Database (CSD) [18]. There is no trans effect
insertion. The changes in chemical shifts of the CO
insertion products, (dppf)Pd(C(O)Me)Cl and (dppe)Pd-
(C(O)Me)Cl, are 1.20 and 1.41 ppm, respectively. These
chemical shift changes are smaller than those found in
the SO2 insertion products (dppf)Pd(SO2)Me)Cl (2.19
ppm) and (dppe)Pd(SO2)Me)Cl (1.98 ppm). Neverthe-
less, both CO and SO2 insertion products represent
electron-withdrawal from the methyl group after inser-
on the PdÃ
/
P distances from the Cl and Me groups
˚
bonded to Pd in 1. The PdÃ
/
Cl (2.3338(11) A) and PdÃ
/C
˚
(2.051(2) A) in 1 are similar in length to those found in
˚
Cl (2.324(3) A and
(s2-N,N?-iPrÃ
/
DIP)Pd(Me)Cl (PdÃ
/
(2.01(1) A) and [(terpy)Pd(Me)]ꢂ [PdÃ
/C
˚
PdÃ
/
C
(2.041(12) A] [10b].
˚
tion. A confirmation of SO2 insertion into the PdÃ
/C
3.2. Reactions with sulfur dioxide
bond is provided by the X-ray structure of
(dppf)Pd(SO2Me)Cl (Fig. 2). The differences in chemical
shifts of the methyl protons of the diphosphino com-
All the chloro(methyl)palladium complexes readily
reacted with SO2 (Eq. (1)).
plexes prior to SO2 insertion and after (d2ꢃ
3) can be seen as a measure of the extent of back
bonding. For example (d2ꢃd1) for the dippf complex is
2.23 ppm whilst the dppf and dppe complexes have (d2ꢃ
/
d1 in Table
ð1Þ
/
/
d1) values of 2.19 and 1.98 ppm, respectively. Thus the
back bonding in the dippf complex is more extensive.
When a slow stream of nitrogen was bubble through a
The complexes with phosphorous and nitrogen ligands
changed from yellow to red, whilst the COD complex
changed from colourless to yellow. Thus colour changes
were a clear indication of reaction. From the H NMR
spectra, it was easy to establish insertion of SO2 into the
1
1
CDCl3 solution of 5, the H NMR spectrum showed
that the solution was nearly 1:1 mixture of (3,5-
ditBupz)2Pd(Me)Cl and (3,5-ditBupz)2Pd(SO2Me)Cl
and a small amount of an unidentified product; indicat-
ing some reversibility of the SO2 insertion.
PdÃ
/
C bond. This involved downfield chemical shifts
C bonds
(Table 3). Insertion of small molecules into PdÃ
/
as in (dppf)Pd(C(O)Me)Cl and (dppe)Pd(C(O)Me)Cl
[12] shifts methyl proton resonance downfield by more
than 1.0 ppm from the peaks of the complexes prior to
The solid-state structure of complex 3 is shown in Fig.
2 and depicts the insertion of SO2 into the PdÃ
/
C bond.
Table 3
1H NMR of methyl chemical shifts of pre-insertion compounds and insertion products
Complex
d1 (ppm)
Insertion product
d2 (ppm)
D(d2ꢃd1) (ppm)
/
(dppf)PdMeCl
(dippf)PdMeCl
(dppe)PdMeCl
(3,5-dit Bupz)2PdMeCl
(COD)PdMeCl
0.79
0.90
0.76
(dppf)Pd(SO2Me)Cl
(dippf)Pd(SO2Me)Cl
(dppe)Pd(SO2Me)Cl
(3,5-dit Bupz)2Pd(SO2Me)Cl
(COD)Pd(SO2Me)Cl
2.98
3.13
2.74
3.12
3.22
2.19
2.23
1.98
3.26
2.05
ꢃ
/
0.14
1.17

K. Li et al. / Polyhedron 22 (200£) 805ꢁ
/
810
809
Table 4
in the solid-state at 80 8C, without the de-insertion of
SO2, to unidentified products. However, both (3,5-
ditBupz)2Pd(SO2Me)Cl (5) and (COD)Pd(SO2Me)Cl
(6) were unstable in solution over long periods.
˚
Selected bond lengths (A) and angles (8) for complex 3
Bond lengths
PdÃ
PdÃ
SÃ
P(1)Ã
SÃO(2)
/
P(1)
2.3104(7)
2.3528(7)
1.789(3)
1.800(3)
1.458(3)
PdÃ
PdÃ
SÃ
P(2)Ã
/
S
2.3262(9)
2.3767(8)
1.484(3)
1.809(3)
Wojcicki observed several years ago that SO2 inser-
carbon bond is electrophilic in nature
/
Cl
/P(2)
/C(35)
/
O(1)
tion into metalÃ
/
/C(1)
/
C(6)
[3a]. It is therefore conceivable that the stability of (PÃ
/
/
P)Pd(SO2Me)Cl compared to (3,5-ditBupz)2Pd(SO2-
Me)Cl and (COD)Pd(SO2Me)Cl could be due to the
presence of the more electron-donating diphosphino
ligands. Both (3,5-ditBupz)2Pd(SO2Me)Cl and (COD)-
Pd(SO2Me)Cl slowly decomposed in solution over
Bond angles
P(1)ÃPdÃ
SÃPdÃCl
SÃPdÃP(2)
C(35)ÃSÃPd
O(2)ÃSÃPd
/
/
S
89.34(3)
89.91(3)
P(1)Ã
P(1)Ã
ClÃPdÃ
O(1)ÃSÃ
O(2)ÃSÃ
/
PdÃ
PdÃ
/
Cl
176.59(3)
96.90(3)
83.82(3)
110.44(2)
115.47(8)
/
/
/
/P(2)
/
/
173.71(3)
113.04(14)
110.71(13)
/
/P(2)
/
/
/
/
Pd
1
/
/
/
/
O(1)
several days. By monitoring the SO2 reaction with H
NMR spectroscopy (Table 5), three new sets of peaks
were found at 6.18, 5.96ꢁ5.97 and 3.22 ppm after 15 min
/
Table 4 contains selected bond distances and angles. The
geometry around the Pd in 3 is distorted square-planar,
with the cis angle ranging between 83.82(3)8 and
96.90(3)8. The bite angle of the bidentate ligand is
similar to that in (dppf)Pd(SC6H4S-o) (97.248) [17], but
slightly larger than the corresponding angle observed in
in addition to (COD)Pd(Me)Cl peaks. The peaks of
(COD)Pd(Me)Cl disappeared completely after 18 h,
leaving only peaks of (COD)Pd(SO2Me)Cl. After 3
days, a completely new set of peaks appeared at 6.03ꢁ
/
6.10, 5.58ꢁ5.63, 2.89 ppm, in addition to reduced
/
intensity peaks of (COD)Pd(SO2Me)Cl. After 11 days,
all the (COD)Pd(SO2Me)Cl peaks had disappeared
completely, a clear indication that (COD)Pd(SO2Me)Cl
is unstable in solution over a long period. The final
decomposition product is a mixture of unidentifiable
(dppf)PdCl2 (99.078) [19]. Similarly, the average PdÃ
/
P
˚
˚
S (2.326 A) distances in 3 are only
(2.310 A) and PdÃ
/
slightly longer than the average PdÃ
/
P distance (2.29(5)
˚
S distance (2.30(3) A) obtained
˚
A) and the average PdÃ
/
1
by averaging 2422 and 340 corresponding distances,
respectively reported to the CSD [18]. Hence, the
compounds, based on the H NMR, but the decom-
position does not lead to SO2 desorption; hence the SO2
insertion reaction is not reversible.
insertion of SO2 into the PdÃ
/
C bond does not seem to
affect the PdÃP and PdÃS distances considerably.
/
/
The reaction of (COD)Pd(Me)Cl with SO2 was much
slower than those of the phosphine and pyrazole
complexes. Complete conversion of (COD)Pd(Me)Cl
4. Conclusions
to (COD)Pd(SO2Me)Cl took 18 h (Table 5). The (PÃ
/
Insertion of SO2 into PdÃ
/
C bond produces S-sulfi-
P)Pd(SO2Me)Cl products (2ꢁ4) were stable in solution
/
nato palladium complexes in moderate yields. The SO2
insertion with the complexes bearing diphosphino
ancillary ligands appears to be more facile, which is in
accord with the electrophilic nature of SO2 insertion
mechanism. The insertion products 5 and 6 showed
signs of decomposition upon storage in solution, which
was more pronounced for 6. Decomposition of 5 was
mainly due to SO2 de-insertion, indicating reversibility
of the insertion process in the absence of the reaction
condition necessary to shift the equilibrium toward the
insertion product.
for indefinite periods as evidenced by the slow crystal-
lization of 2 from 1:1 mixture of CH2Cl2/hexane over
several days. Complexes 2ꢁ4 decomposed when heated
/
Table 5
Effect of time on the SO2 insertion reaction and product stability of
(COD)Pd(SO2Me)Cl
Time
0
1H NMR (CDCl3) (ppm)
5.90 (m, 2H, COD); 5.15 (m, 2H, COD); 2.62 (m, 4H, COD);
2.46 (m, 4H, COD); 1.17 (s, 3H, PdÃMe)
/
15 min 6.17 (m, 2H, COD); 5.96 (m, 2H, COD); 5.90 (m, 2H, COD);
5.15 (m, 2H, COD); 3.22 (s, 3H, SO2Me); 2.75 (m, 4H, COD);
5. Supplementary material
2.62 (m, 4H, COD); 2.46 (m, 4H, COD); 1.17 (s, 3H, PdÃMe)
/
18 h
6.18 (s, br, 2H, COD); 5.97 (s, br, 2H, COD);
3.22 (s, 3H, SO2Me); 2.89 (m, 4H, COD);
2.71 (m, 4H, COD)
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC Nos. 185331 and 158332. Copies of
this information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge, CB2
3 days 6.18 (s, br, 2H, COD); 6.06 (m, 2H, COD);
5.97 (s, br, 2H, COD); 5.60 (m, 2H, COD);
3.22 (s, 3H, Ã/SO2Me); 2.90 (m, 4H, COD);
2.88 (s, 3H, SO2Me); 2.70 (m, 4H, COD)
6.06 (m, 2H, COD); 5.60 (m, 2H, COD); 2.90 (m, 4H, COD);
2.88 (s, 3H, SO2Me); 2.70 (m, 4H, COD)
1EZ,
UK
(fax:
ꢂ
/
44-1223-336033;
e-mail:
11
days
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk).

810
K. Li et al. / Polyhedron 22 (200£) 805ꢁ810
/
[8] L. Lefort, R.J. Lachicotte, W.D. Jones, Organometallics 17 (1998)
1420.
Acknowledgements
[9] M.S. Morton, R.J. Lachicotte, D.A. Vicic, W.D. Jones, Organo-
metallics 18 (1999) 227.
This work was supported by the National Research
Foundation (South Africa) and in part by the Interna-
tional Foundation for Science (IFS) (Sweden).
[10] (a) P.W.N.M. van Leeuwen, C.F. Roobeek, Eur. Pat. Appl., 1990,
380,162.;
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Leeuwen, C.F. Roobeek, M.C. Zoutberg, Y.F. Wang, C.H. Stam,
Inorg. Chim. Acta 169 (1990) 5.
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