Insertion of alkenyl sulfides into a palladium-aryl bond. 1. Synthesis and evolution of a three-membered thiopalladacycle. X-ray crystal structure of a new tetrameric palladium derivative with bridging (phenylthio)alkyl ligands

Article abstract of DOI:10.1021/om960406d

A three-membered dimeric (phenylthio)alkylpalladacycle (mixture of diastereoisomers) has been synthesized by Pd-C₆F₅ addition to the double bond of phenyl vinyl sulfide. The coordination mode of the organic moiety changes slowly in s

Full text of DOI:10.1021/om960406d

Organometallics 1996, 15, 5003-5009
5003
In ser tion of Alk en yl Su lfid es in to a P a lla d iu m -Ar yl
Bon d . 1. Syn th esis a n d Evolu tion of a Th r ee-Mem ber ed
Th iop a lla d a cycle. X-r a y Cr ysta l Str u ctu r e of a New
Tetr a m er ic P a lla d iu m Der iva tive w ith Br id gin g
(P h en ylth io)a lk yl Liga n d s
Ana C. Albe´niz,† Pablo Espinet,*,† Yong-Shou Lin,† A. Guy Orpen,‡ and
Antonio Mart´ın‡
Departamento de Quı´mica Inorga´nica, Facultad de Ciencias, Universidad de Valladolid,
E-47005 Valladolid, Spain, and School of Chemistry, University of Bristol,
Bristol BS8 1TS, United Kingdom
Received May 24, 1996X
A three-membered dimeric (phenylthio)alkylpalladacycle (mixture of diastereoisomers) has
been synthesized by Pd-C6F5 addition to the double bond of phenyl vinyl sulfide. The
coordination mode of the organic moiety changes slowly in solution from a chelating σ-κS-yl
to a bridging µ(σ-κS-yl), and the palladacyclopropane isomerizes to an unusual tetrameric
palladium complex; the X-ray crystal structure of this latter derivative has been determined,
and it shows that each pair of palladium atoms are linked by either two bridging chlorine
atoms or two bridging (phenylthio)alkyl moieties. The tetramer has four chiral carbon atoms
and has S4 symmetry (meso form), showing that the crystals are formed stereospecifically
from the diastereomeric mixture of dimers. The decomposition pathways of the palladacy-
clopropane complex have been analyzed. Two main routes have been observed, i.e., (a) 1,2-
hydrogen shift and Pd-SR â-elimination, which occurs in refluxing toluene, and (b) hydrolysis
of the C-S bond to give an aldehyde and a palladium thiolate, predominant at room
temperature in the presence of ligands such as tetrahydrothiophene.
Ch a r t 1
In tr od u ction
Three-membered organometallic metallacycles involv-
ing a donor atom bearing a lone pair are not very
common in transition metal organometallic chemistry.1
Among this type of complexes a few examples of sulfur-
containing metallacyclopropane structures can be found,
such as thioaldehyde metallacycles (A, Chart 1),2 (me-
thylthio)methyl derivatives (B, Chart 1),3 and other
related (methylthio)metallacyclopropanes.4 A resonant
metallathiocyclopropane structure also contributes to
explain the bonding of unsaturated substrates, such as
CS2, to low-valent metal complexes (C, Chart 1).5a
Three-membered metallacycles are also present in the
complexes obtained by coordination of other dithio
derivatives, which usually act as bridging ligands in a
variety of modes.5b In this paper, we describe the
preparation of a new three-membered (phenylthio)alkyl
palladacycle, synthesized by Pd-aryl addition to the
double bond of a vinyl sulfide. Several decomposition
routes found for this complex are also analyzed.
The (methylthio)methyl moiety has been shown to
adopt different coordination modes: monodentate σ-yl;
chelating σ-κS-yl (B, Chart 1); or bridging µ-(σ-κS-yl).
All these arrangements have been found in palladium
chemistry,3,6-8 and no interconversion between these
coordination modes has been reported. Here an un-
precedented isomerization of a palladacycle with a
chelating σ-κS-yl (phenylthio)alkyl ligand to an oligomer
with bridging µ-(σ-κS-yl) ligands is reported.
* To whom correspondence should be addressed. E-mail: espinet@
cpd.uva.es.
† Universidad de Valladolid.
‡ University of Bristol. E-mail (Prof. Orpen): Guy.Orpen@bris.ac.uk.
X Abstract published in Advance ACS Abstracts, September 15, 1996.
(1) Omahe, I. Organometallic Intramolecular-coordination Com-
pounds; Elsevier: Amsterdam, 1986.
(2) Nelson, J . E.; Parkin, G.; Bercaw, J . E. Organometallics 1992,
11, 2181 and references therein.
(3) (a) Miki, K.; Kai, Y.; Yasuoka, N.; Kasai, N. Bull. Chem. Soc.
J pn. 1981, 54, 3639. (b) Chong, K. S.; Rettig, S. J .; Storr, A.; Trotter,
J . Can. J . Chem. 1980, 58, 1080. (c) Collins, T. J .; Roper, W. R. J .
Organomet. Chem. 1978, 159 (1), 73. (d) Miki, K.; Kai, Y.; Yasuoka,
N.; Kasai, N. J . Organomet. Chem. 1977, 135, 53. (e) Yoshida, G.;
Kurosawa, H.; Okawara, R. J . Organomet. Chem. 1976, 113, 85. (f) de
Gil, E. R.; Dahl, L. F. J . Am. Chem. Soc. 1969, 91, 3751. (g) King, R.
B.; Bisnette, M. B. Inorg. Chem. 1965, 4, 486.
Resu lts
Syn th esis a n d Ch a r a cter iza tion of th e P a lla d a -
cycles. The reaction of equimolar amounts of [Pd-
(4) (a) Doyle, R. A.; Angelici, R. J . J . Am. Chem. Soc. 1990, 112,
194. (b) Glavee, G. N.; Angelici, R. J . J . Am. Chem. Soc. 1989, 111,
3589.
(5) (a) Maitlis, P. M.; Espinet, P.; Russell, M., J . H. in Comprehensive
Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W.,
Eds.; Pergamon Press: Oxford, 1982; Vol. 6, Sections 38.2 and 39.7.7.
(b) Miguel, D.; Riera, V.; Miguel, J . A.; Go´mez, M.; Sola´ns, X.
Organometallics 1991, 10, 1683 and references therein.
(6) Miki, K.; Kai, Y.; Yasuoka, N.; Kasai, N. J . Organomet. Chem.
1979, 165, 79.
(7) Miki, K.; Yoshida, G.; Kai, Y.; Yasuoka, N.; Kasai, N. J .
Organomet. Chem. 1978, 149, 195.
(8) Basato, M.; Grassi, A.; Valle, G. Organometallics 1995, 14, 4439.
S0276-7333(96)00406-2 CCC: $12.00 © 1996 American Chemical Society

5004 Organometallics, Vol. 15, No. 23, 1996
Albe´niz et al.
(C6F5)Br(NCMe)2] (1a ) and phenyl vinyl sulfide in
CH2Cl2 at room temperature gave complex 2a (eq 1) as
could produce the two isomers observed. The chemical
shift difference between the 19F signals of both isomers
(around 0.5 ppm) favors the second possibility, which
provides a more different chemical environment for the
pentafluorophenyl groups in both isomers. The pres-
ence of CD3CN easily promotes a bridge-splitting pro-
cess and interconverts the diastereoisomers. The in-
terconversion is more difficult in the poorly coordinating
toluene. It seems, then, that the lone pair of the S-atom
exhibits little activity as a bridge-splitting promoter. For
steric reasons, it is unlikely that the S-atom can act as
the promoter of cleavage of the halo bridges of a second
dimer unless it decoordinates first. Thus, this “inter-
molecular” bridge-splitting is associated to a compara-
tively high energy S-decoordination of the chelate and
must be slow (see below, rearrangement to a tetramer).
A yellow solid can be obtained when 2a is reacted with
2 mol of PPh3 in CH2Cl2 solution (Scheme 1). Its 19F
a yellowish orange solid in high yield (83%). When the
reaction was carried out in an NMR tube, in CDCl3, a
small amount of the organic derivative, vinylpentafluo-
robenzene, was also detected (2% based on the integra-
tion of the 19F NMR signals of the C6F5 group). The
reaction was also performed using [Pd(C6F5)Cl(NCMe)2]
(1b) as starting material, and an analogous complex,
2b, was obtained (eq 1). 2a ,b were identified by 1H,
19F, 13C NMR and C, H elemental analysis; the corre-
sponding data can be found in the Experimental Section.
Since 2a and 2b bear the same organometallic ligand
and show the same behavior, only the identification and
reactions of 2a will be discussed.
1
and H NMR spectra indicate that the solid is a mixture
of two monomeric isomers, 3a and 3b, in a 7.7:1 ratio,
1
which could not be separated. The H NMR spectrum
of the mixture shows two ABX systems with a pattern
similar to that found for 2a , and its assignment was
1
made by comparison with the H NMR spectrum of 2a .
The major isomer 3a was assigned a cis P-Pd-C
2
arrangement on the basis of the small value J PC found
(2J PC ) 5.6 Hz).10
The 19F NMR spectrum of complex 2a clearly shows
that it is a mixture of two isomers in CDCl3 at room
temperature (ratio 2.5:1), each showing an ABX system
in the 1H NMR spectrum, which indicates that a CHCH2
moiety is present in both 2a isomers. Each isomer
exhibits two singlets in the aliphatic region of the 13C-
{1H} spectrum that can be assigned to PfCH2 (δ 27.1
and 24.5 ppm for each isomer) and PdCHS (δ 65.0 and
58.8 ppm for each isomer) in good agreement with the
chemical shifts observed for other pentafluorophenyl-
substituted alkyl sulfide palladacycles.9 Thus, after
insertion of the double bond into the Pd-C6F5 bond,
coordination of the S atom gives an unusual three-
membered palladacycle. As far as we know, only one
other example of this type of palladium complex has
been reported.3a,d,e
Br om in a tion of 2a . Bromination of 2a was carried
out by adding bromine to a CH2Cl2 solution of 2a at
room temperature (Scheme 1). A brown precipitate
formed immediately. After 4 h, the brown solid, PdBr2
mixed with a small amount of [PhSPdBr]n and Pd(0),
was separated from a colorless filtrate. After evapora-
tion of the solvent, the oily residue was analyzed by 1H,
19F NMR, and GC-MS. A mixture of organic deriva-
tives was found: phenyl 1-bromo-2-(pentafluorophenyl)-
ethyl sulfide (4, 79%), 2-(pentafluorophenyl)acetalde-
hyde (5, 12%), (E)-phenyl 2-(pentafluorophenyl)vinyl
sulfide (6, 7%), and (Z)-phenyl 2-(pentafluorophenyl)-
vinyl sulfide (7, 2%). The ratios in parentheses are
based on integration of the 19F NMR signals of the C6F5
1
group. The structure of 4 was confirmed by a H{19F}
decoupling experiment. The 1H NMR spectrum of 4
shows an ABX pattern, and each signal of the AB
system is further split into triplets with a small coupling
Both the S atom and the C atom in the palladacycle
are chiral. This should give rise in the dimeric complex
to up to eight diastereoisomers (with their corresponding
enantiomers). Besides, the palladacycles can adopt
either a trans or a cis arrangement in the dimer, which
doubles the number of possible isomers. However, only
4
constant, corresponding to J HF involving the Fortho of
the C6F5 group; this coupling disappears in the 1H{19F}-
decoupled spectrum. The reaction of 2a with Br2 to form
4 gives support to the structure of 2a as a three-
membered palladacycle arising from coordination of a
sulfur atom and a σ-bonded C to palladium. Attempts
at separation of the mixture by preparative TLC (silica
sheet) eluting with n-hexane gave four pure compounds
corresponding to 6 (Rf ) 0.60), 7 (Rf ) 0.45), 5 (Rf ) 0),
and a new derivative, 1,1-bis(phenylthio)-2-(pentafluo-
rophenyl)ethane (8, Rf ) 0.30). No 4 was found. 8 was
two distinct diastereoisomers are observed by 19F NMR
19
as two separate sets of signals. The two
F
reso-
para
nances that appear for 2a in toluene at room temper-
ature (internal capillary with DMSO-d6 as lock solvent)
convert into one at 70 °C. The 19F NMR of 2a in CD3-
CN at room temperature shows only one isomer. The
inversion of the coordinated sulfur atom was found to
be fast in the other three-membered palladacycle de-
scribed, as this inversion process occurs without cleav-
age of the Pd-S bond.3e Thus, if the S-atom racemizes
in the NMR time scale, it seems that the two diastere-
oisomers observed are due to the dimeric nature of the
complex. Either the chirality of the carbon or the cis
or trans arrangement of the palladacycles in the dimer
1
identified by H, 19F NMR and GC-MS, and its appear-
ance can be attributed to decomposition of 4 to form 8
in the course of operation.
Decom p osition Rea ction s of 2a . Complex 2a is
fairly stable both in the solid state and in chloroform
solution. However, decomposition occurs in refluxing
toluene. After 16 h, a mixture of organic compounds
(9) Albe´niz, A. C.; Espinet, P.; Lin, Y.-S. Organometallics 1996, 15,
5010.
(10) Nakazawa, H.; Ozawa, F.; Yamamoto, A. Organometallics 1983,
2, 241.

Insertion of Alkenyl Sulfides into a Pd-Aryl Bond
Organometallics, Vol. 15, No. 23, 1996 5005
Sch em e 1
Ta ble 1. Decom p osition of 2a in th e P r esen ce of
th t
are also found. The addition of base slows down the
decomposition process (Table 1, entry 3). Thus, acid
attack must play an important role in the hydrolysis
(see Discussion).
Ch a r a cter iza tion of [P d (µ-Cl){µ-(σ-K-P h SCHCH2-
C6F 5)}]4 (11). Careful crystallizations of complexes 2
and 3 were attempted in order to obtain suitable
crystals for structural determination by X-ray diffraction
analysis. The crystallization was successful only for the
chloro-bridged complex 2b. After 2 months in a mixture
of CH2Cl2/Et2O at -20 °C, orange crystals were obtained
that correspond to the tetrameric complex [Pd(µ-Cl){µ-
(σ-κ-PhSCHCH2C6F5)}]4 (11).
amount
time
(days)
organic products
(ratio)a
decomposeda
(%)
entry
1
additive
1
7
1
7
1
7
5
28
89
87
91
11
18
5 (31), 6 (1)
2
3
HClO4-H2Ob
KOH-H2Ob
5 (6), 6 (1), 10 (3.5)
5 (7.4), 6 (1), 10 (4.5)
5 (2.7), 6 (1)
5 (3.1), 6 (1)
a
The ratios are based on the integration of 19F NMR signals.
b
One drop of 70% aqueous HClO4 or 1 M aqueous KOH was added
in entries 2 and 3, respectively.
The 19F NMR spectrum of 11 in CDCl3 at room
temperature shows the presence of only one type of C6F5
group, and the 1H NMR spectrum shows one ABX
pattern (δ: H1 ) 4.62, H2 ) 3.30, and H2′ ) 2.19), which
must be the result of the molecular symmetry.
had formed: 9, 5, 6, 7, and phenyl 2-(pentafluorophe-
nyl)ethyl sulfide (10), plus a dark brown solid containing
[PhSPdBr]n, PdBr2, and Pd metal (Scheme 1). The
molar ratios of these organic compounds are 3.7:2.2:1.9:
1.3:1 on the basis of integration of 19F NMR signals in
toluene (acetone-d6 was used as external lock solvent).
9 was identified by comparison with a commercial
sample. The other C6F5-substituted compounds were
An X-ray diffraction study of 11 was undertaken.
Figure 1 shows the molecular structure of the tetrameric
complex. Selected bond lengths and bond angles along
with their estimated standard derivations are given in
Table 2. The complex is tetranuclear with exact crys-
tallographic S4 symmetry. The four palladium atoms
are located at the corners of a tetrahedron. The
environment of each palladium atom is square planar
with the palladium coordinated by two chlorine, sulfur,
and C(1) atoms. The remarkable feature of the molec-
ular structure is that each of the four (phenylthio)-
methyl groups acts as a bidentate ligand bridging two
Pd2(µ-Cl)2 units. The S4 molecular symmetry explains
the equivalence observed for the chiral moieties in the
tetramer (while they produce diastereoisomers in the
dimer), since the molecule is a meso form.
1
identified by analyses of H and 19F NMR spectra and
GC-MS after evaporation of the toluene.
With the aim of understanding the mechanism of
formation of aldehyde 5 from 2a and how the cleavage
of the C-S bond occurs, the decomposition of 2a in
CDCl3 was carried out in the presence of different
additives. The addition of a 4-fold amount of tetrahy-
drothiophene (tht) accelerates the decomposition mod-
erately. Only one isomer is observed on addition of this
ligand as a result of cleavage of the bromine bridges by
tht. The decomposition reaction was also monitored by
19F NMR spectroscopy in the presence of acid or base
at room temperature. The results are given in Table 1.
The addition of acid produces a dramatic acceleration
in the decomposition of 2a (Table 1, entry 2). The major
complex is the aldehyde 5; the products of Pd-H elimi-
nation (6) and acid attack on the starting complex (10)
The Pd-C bond length in the present complex (2.036
Å) is similar to the distances found for other related
structures: [PdCl(σ-κ-CH2SCH3)(PPh3)],3d [PdCl(σ-CH2-
SCH3)(PPh3)2],6 [Pd{µ-(σ-κ-CH2SCH3)}2]4,7 and [Pd3(µ-

5006 Organometallics, Vol. 15, No. 23, 1996
Albe´niz et al.
Cl trans to coordinated sulfur atom. The distance
between each pair of palladium atoms in Pd2(µ-Cl)2
units is 2.917 Å, which is shorter than twice the covalent
radius of Pd (viz. 2.98 Å),13 but longer than that found
in elemental palladium (2.751 Å).14 Thus, direct inter-
action between the palladium atoms is unlikely. Similar
Pd-Pd distances (2.864-2.946 Å) have been observed
in multinuclear palladium complexes containing bridg-
ing acetate groups.15 The shorter Pd-Pd distance in
complex 11 is a result of considerable folding of the Pd2-
(µ-Cl)2 rings; that is, the chlorine bridge is bent, which
is a reflection of ligand interactions and steric require-
ments.
Discu ssion
Addition of Pd-C6F5 to the double bond of phenyl
vinyl sulfide produces a three-membered thiometalla-
cycle of high stability, 2. A resonance hybrid CdS T
CsS has been suggested to play a role in stabilizing this
type of three-membered ring palladium complexes.16 We
could not determine the value of the S-C distance in
our palladacycles, but a S-C bond length (1.756 Å)
slightly shorter than the estimated S-C single bond
length (1.82 Å) has been found in the structural deter-
mination of the other palladium thiometallacyclopro-
pane complex reported in the literature, thus supporting
the above-mentioned proposal.3a,d
The µ-(σ-κ) coordination mode for the alkylthio moiety,
less strained, seems to give complexes thermodynami-
cally more stable than those bearing the chelating form
of the ligand as shown by the slow interconversion of
complex 2b to the tetranuclear complex 11. The inver-
sion of the coordinated S atom is known to be fast and
does not need decoordination. This leaves the carbon
atom as the only chiral center to be considered. Its
chirality, however, is enough to allow us to recognize
two different mechanisms in the rearrangement of
complex 2b, which are shown in Scheme 2.
F igu r e 1. ORTEP plot of complex [Pd(µ-Cl){µ-(σ-κ-
PhSCHCH2C6F5)}]4 (11).
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 11a
Pd-C(1B)
Pd-Cl(A)
Cl-Pd(A)
C(1)-Pd(C)
2.036(8)
2.392(2)
2.392(2)
2.036(8)
Pd-S
2.308(2)
2.469(2)
1.849(9)
2.917(2)
Pd-Cl
S-C(1)
Pd-Pd(A)
C(1B)-Pd-S
S-Pd-Cl(A)
Pd-S-Cl
88.0(3)
175.17(8) C(1B)-Pd-Cl
98.66(8) Cl(A)-Pd-Cl
C(1B)-Pd-Cl(A)
90.2(3)
173.1(3)
83.28(10)
123.62(7)
51.92(6)
103.9(3)
C(1B)-Pd-Pd(A) 125.2(2)
S-Pd-Pd(A)
Cl(A)-Pd-Pd(A)
Pd(A)-Cl-Pd
S-C(1)-Pd(C)
54.36(6) Cl-Pd-Pd(A)
73.73(7) C(1)-S-Pd
106.4(4)
a
Symmetry transformations used to generate equivalent at-
oms: (A) -x + 1 + 1, -y + 1/2, z + 1 - 1; (B) y + 3/4, -x + 5/4,
-z + 1/4; (C) -y + 5/4, x - 3/4, -z + 1/4.
O2CMe)3{µ-(σ-κ-MeSCHR)}3],8 and it is consistent with
the expected Pd(II)-C(sp3) single bond length11 and that
reported for alkylpalladium(II) complexes (2.083 Å).12
The Pd-S distance found for 11 (2.308 Å) is slightly
shorter than those found for the three-membered ring
palladacycle present in [PdCl(σ-κ-CH2SCH3)(PPh3)] or
for tetrameric complex [Pd{µ-(σ-κ-CH2SCH3)}2]4, prob-
ably due to the lower trans influence of the Cl atom
compared to PPh3 or CH2SPh groups, but it is similar
to the Pd-S bond lengths in [Pd3(µ-O2CMe)3{µ-(σ-κ-
MeSCHR)}3] and dialkyl thioethers (2.283 Å).12 The
S-C(1) bond length (1.849 Å) corresponds to the esti-
mated single bond value of the S-C(sp3) link (1.82 Å)
and is similar to that found in the complex [Pd{µ-(σ-κ-
CH2SCH3)}2]4; however, it is longer than the corre-
sponding distance in [PdCl(σ-κ-CH2SCH3)(PPh3)] and
[Pd3(µ-O2CMe)3{µ-(σ-κ-MeSCHR)}3]. The S-Pd-C angle
in complex 11 is in the normal value range found for a
palladium square-planar structure. The existence of
two distinct Pd-Cl bond lengths can be attributed to
the different trans influence of the ligands, the longer
(2.469 Å) being found for the Cl trans to the σ-bonded
carbon and the shorter (2.392 Å) corresponding to the
The first one concerns the interconversion of the
dimers, which are formed in a nonstereoselective fashion
and give rise to diastereoisomers. For their intercon-
version bridge splitting to give monomers is enough.
This splitting is a very fast process when it is assisted
by coordinating solvents (such as CD3CN) and much
slower when the solvent is only poorly coordinating
(toluene, CDCl3). Whether the process becomes dis-
sociative in the latter has not been investigated.
The second process, formation of the tetramer from
the dimers, occurs, and only the meso form is obtained
stereoselectively; the process is extremely slow. This
process involves necessarily the following steps: (i)
S-decoordination, since the C-S chelating ligand has
to change to C-S bridging (we believe that the low rate
of the process is associated to the high activation energy
of this step) and (ii) splitting of the chloro bridges, since
a direct dimerization of the dimers should produce
diastereomeric tetramers and this is not observed.
(13) Andrianov, V. G.; Biryukov, B. P.; Struchkov, J . T. J . Struct.
Chem. 1969, 10, 1129.
(14) Donohue, J . The Structure of Elements; Wiley: New York, 1974;
p 216.
(11) Horike, M.; Kai, Y.; Yasuoka, N.; Kasai, N. J . Organomet. Chem.
1975, 86, 269.
(12) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G.; Taylor, R. J . Chem. Soc., Dalton Trans. 1989, S1.
(15) Cabri, W.; Candlani, I. Acc. Chem. Res. 1995, 11, 2 and
references therein.
(16) Yoshida, G.; Kurosawa, H.; Okawara, R. J . Organomet. Chem.
1977, 131, 309.

Insertion of Alkenyl Sulfides into a Pd-Aryl Bond
Organometallics, Vol. 15, No. 23, 1996 5007
Sch em e 2
Sch em e 3
since terminal olefins give ketones as the only product.18
In the presence of tht the decomposition of 2a to
aldehyde is dramatically accelerated by acid, which
suggests that the protonation of the sulfur atom occurs
in the first step.19 The hydrolytic mechanism is outlined
in Scheme 3 and it is consistent with our results.
Protonation of the S-atom and opening of the three-
membered ring through C-S bond cleavage generates
an intermediate palladium alkylidene that undergoes
nucleophilic attack by OH-.4,19-21 Pd-H elimination at
this point produces the aldehyde. At the same time,
Pd-H elimination in complex 2a with no C-S cleavage
also occurs to generate C6F5-substituted alkenyl sulfide
6 as a minor product (path a, Scheme 3). Another
possible and perhaps competitive decomposition path-
way of the intermediate Pd alkylidene is the direct
oxidation by oxygen, which is a process known for other
transition metal carbene complexes.22 In fact, the
reaction slows down noticeably in the absence of oxygen
but still occurs. The addition of tht promotes the
aldehyde formation, but its role is unclear. Coordina-
tion of this ligand to the metal by bridge cleavage could
reduce the amount of donation of the (phenylthio)alkyl
sulfur to the metal; this would make the sulfur atom
more prone to acid attack, which would trigger the
In order to stress the need for both processes, and for
the sake of conciseness, monomeric bridge-split and
S-decoordinated species are drawn in Scheme 2. Obvi-
ously they are statistically and thermodymamically very
unlikely. It seems more reasonable that dimeric species
with chloro bridges and only one decoordinated S atom
use this atom to attack a second dimeric species and
promote its bridge splitting and so on.
The extreme slowness of the process makes the
stereoselection possible, in spite of the fact that the
difference in energy between the meso form and other
possible tetramers is likely to be small. Probably for
steric reasons, the meso form is the thermodynamic
product of the reaction.
Although complex 2a is quite stable, its decomposition
occurs when refluxed in toluene or slowly at room
temperature in the presence of ligands such as tht. The
main decomposition pathway for this complex in reflux-
ing toluene gives vinylpentafluorobenzene (9) by a one-
step Pd-migration to the C6F5-substituted carbon and
â-SR elimination.17 However, at room temperature in
the presence of tht the main decomposition pathway is
different and, although it also involves cleavage of C-S
bond in the three-membered palladium complex, gives
aldehyde 5 as the main product (Scheme 3). Interest-
ingly, 5 is not a product of the Wacker oxidation of 9
(18) Heck, R. F. Palladium Reagents in Organic Syntheses; Academic
Press: Suffolk, 1995; p 59.
(19) McPherson, H. D.; Wardell, J . L. Inorg. Chim. Acta 1979, 35,
L353.
(20) Steinborn, D. Angew. Chem., Int. Ed. Engl. 1992, 31, 401.
(21) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.
Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987; p 119.
(22) (a) Casey, C. P.; Burkhardt, T. J .; Bunnell, C. A.; Calabrese, J .
C. J . Am. Chem. Soc. 1977, 99, 2127. (b) Fischer, E. O.; Riedmu¨ller, S.
Chem. Ber. 1974, 107, 915.
(17) (a) Osakada, K.; Ozawa, Y.; Yamamoto, A. J . Chem. Soc., Dalton
Trans. 1991, 759. (b) Osakada, K.; Matsumoto, K.; Yamamoto, T.;
Yamamoto, A. Organometallics 1985, 4, 857.

5008 Organometallics, Vol. 15, No. 23, 1996
Albe´niz et al.
3a : 19F (CDCl3, δ, 282 MHz) -161.6 (m, Fmeta), -155.9 (t,
process. Attempts at producing the aldehyde catalyti-
cally by reaction of the Pd hydride formed with phenyl
vinyl sulfide have proved unsuccessful up to now.
1
F
para), -142.9 (m, Fortho); H NMR (CDCl3, δ, 300 MHz),7.7-
7.3 (m, 20H, Ph), 3.96 (dd, 1H, J ) 11.6, 3.3 Hz, CH), 2.68
(dd, 1H, J ) 14.5, 11.6 Hz, CH2Pf), 2.17 (bd, 1H, J ) 14.5 Hz,
1
CH2Pf); 13C{1H} NMR (CDCl3, δ, 75.4 MHz) 144.3 (bd, J CF
)
)
Exp er im en ta l Section
246 Hz, C6F5), 140 (bd, 1J CF ) 242 Hz, C6F5), 137.3 (bd, 1J CF
253 Hz, C6F5), 128-134 (4Ph), 113.7 (t, 2J CF ) 18.8 Hz, C6F5),
71.1 (d, 2J PC ) 5.6 Hz, C1), 25.8 (d, 3J PC ) 4.0 Hz, C2); 31P{1H}
NMR (CDCl3, δ, 121.4 MHz), 31.9 (s).
Gen er a l Com m en ts. 19F, 1H, 13C, and 31P NMR spectra
were recorded on Bruker AC-300 and ARX-300 instruments.
Chemical shifts are reported in δ units (parts per million, ppm)
downfield from Me4Si for 1H and 13C, CFCl3 for 19F, and H3-
PO4 (85% in aqueous solution, external reference) for 31P.
Carbon and hydrogen analyses were carried out on a Perkin-
Elmer 2400 CHN elemental analyzer.
All solvents were dried and distilled before use by standard
methods. Phenyl vinyl sulfide was purchased from Aldrich.
[Pd(C6F5)Br(NCMe)2] was prepared as previously reported.23
P r ep a r a tion of [P d (C6F 5)Cl(NCMe)2] (1b). Freshly pre-
pared, wet AgCl (1 g, 6.9 mmol) was added to a solution of 1a
(1 g, 2.3 mmol) in acetonitrile (10 mL). The suspension was
stirred for 72 h in the dark. The yellow precipitate that had
formed was filtered through Celite, and the yellow-orange
solution was evaporated to dryness. The residue was dissolved
in CH2Cl2 and filtered through MgSO4. MeCN (0.5 mL) was
added to the filtrate, and the solution was evaporated to ca. 2
mL; Et2O (5 mL) was added, and a yellow solid was obtained
that was filtered, washed with Et2O, and air dried (0.54 g, 60%
yield). A second batch can be obtained by adding Et2O (2 mL)
to the mother liquors and cooling (0.1 g, 11% yield).
1b: 19F (CD3CN, δ, 282 MHz) -161.1 (m, Fmeta), -157.2 (t,
J ) 19.5 Hz, Fpara), -117.5 (m, Fortho); 1H NMR (CD3CN, δ,
300 MHz) 2.15 (s); IR (Nujol mull, cm-1) 2336 (w, ν CN), 2323
(s, ν CN), 2309 (w, ν CN), 2296 (s, ν CN), 344 (s, ν PdCl). Anal.
Calcd for C10H6ClF5N2Pd: C, 30.71; H, 1.53; N, 7.16. Found:
C, 30.90; H, 1.50; N, 6.92.
P r ep a r a tion of 2a . Phenyl vinyl sulfide (0.060 mL, 0.459
mmol) was added to a solution of [Pd(C6F5)Br(NCMe)2] (0.200
g, 0.459 mmol) in CH2Cl2 (5 mL). After 2 h of stirring,
activated carbon was added to the dark yellow solution, and
the solution was filtered. The filtrate was concentrated to 2
mL, and n-hexane (1 mL) was added. A yellowish orange solid
2a was isolated (0.186 g, 83% yield).
3b: 19F (CDCl3, δ, 282 MHz) -162.7 (m, Fmeta), -156.6 (t,
1
F
para), -142.1 (m, Fortho); H NMR (CDCl3, δ, 300 MHz) 7.7-
7.3 (m, 20H, Ph), 4.17 (bd, 1H, CH), 2.50 (bt, 1H, CH2Pf), 1.99
(bd, 1H, CH2Pf); 31P{1H} NMR (CDCl3, δ, 121.4 MHz) 30.7 (s).
Decom p osition of 2a . A solution of 2a (0.060 g, 0.061
mmol) in toluene (15 mL) was refluxed for 16 h. Analysis of
the 1H and 19F NMR spectra and GC-MS showed that the
decomposition took place to generate a mixture of organic
compounds 9, 5, 6, 7, and 10 in a ratio of 3.7:2.2:1.9:1.3:1 plus
a red brown solid, mainly [PhSPdBr]n.
5: 19F NMR (CDCl3, δ, 282 MHz) -162.3 (m, Fmeta), -154.9
(t, Fpara), -142.4 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz) 9.77
(b, 1H, CHO), 3.88 (b, 2H, PfCH2); MS (El) m/ z (relative
intensity) 210 (M+, 31), 181 (100), 161 (24), 132 (19), 93 (17).
6: 19F NMR (CDCl3, δ, 282 MHz) -163.3 (m, Fmeta), -157.5
(t, Fpara), -144.2 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz) 7.3-
7.5 (m, 5H, Ph), 7.35 (d, J ) 15.9 Hz, 1H, PfCHdCH), 6.42 (d,
J ) 15.9 Hz, 1H, PfCHdCH); MS (El) m/ z (relative intensity)
302 (M+, 79), 301 (31), 181 (41), 135 (47), 123 (30), 110 (32),
109 (36), 91 (44), 77 (77), 69 (42), 65 (43), 51 (100), 50 (39).
7: 19F NMR (CDCl3, δ, 282 MHz) -163.0 (m, Fmeta), -155.7
(t, Fpara), -138.6 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz) 7.3-
7.55 (m, 5H, Ph), 6.87 (d, J ) 9.0 Hz, 1H, PfCHdCH), 6.35
(bd, J ) 9.0 Hz, 1H, PfCHdCH); MS (El) m/ z (relative
intensity) 302 (M+, 72), 301 (29), 181 (34), 135 (49), 123 (33),
110 (34), 91 (48), 77 (72), 69 (45), 65 (47), 51 (100), 50 (37).
10: 19F NMR (CDCl3, δ, 282 MHz) -162.9 (m, Fmeta), -157.0
(t, Fpara), -143.8 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz) 7.3-
7.5 (m, 5H, Ph), 3.13 (m, J ) 7.3 Hz, 2H, PfCH2CH2), 3.01 (t,
J ) 7.3 Hz, 2H, PfCH2CH2); MS (El) m/ z (relative intensity)
304 (M+, 40), 181 (13), 123 (100), 109 (14), 77 (20), 69 (14), 65
(18), 51 (21), 45 (23).
2a : 19F (CDCl3, δ, 282 MHz) -162.0/-162.7* (b, Fmeta),
-156.0/-156.5* (b, Fpara), -142.7/-142.4* (b, Fortho); 1H NMR
(CDCl3, δ, 300 MHz) 8.0-7.4 (m, 5H, Ph), 4.1 (b, 1H, CH), 3.21/
2.69* (b, 1H, J ) 14.7 Hz, CH2Pf), 2.99/2.38* (b, 1H, J ) 14.7
Hz, CH2Pf); 13C{1H} NMR (CDCl3, δ, 75.4 MHz), 144.7 (bd,
Decom p osition of 2a in th e P r esen ce of th t a n d Oth er
Ad d itives. Three NMR tubes were charged with 2a (0.020
g, 0.0204 mmol), tht (0.0072 mL, 0.0816 mmol), and CDCl3
(0.6 mL). HClO4 (1 drop 70% aqueous solution) and KOH (1
drop, 1 M aqueous solution) were added to the second and third
tubes, respectively. The reactions were monitored by 19F NMR
for 2 weeks.
1
1J CF ) 244 Hz, C6F5), 140.0 (bd, J CF ) 240 Hz, C6F5), 137.2
(db, 1J CF ) 252 Hz, C6F5), 132.4 (Ph), 131.2 (C1-Ph), 130.4 (Ph),
129.7 (Ph), 112.0 (b, C6F5), 65.0/58.8* (C1), 27.1/24.3* (C2).
Rea ction of 2a w ith Br 2. To a solution of 2a (0.040 g,
0.0408 mmol) in CH2Cl2 (5 mL) was added Br2 (0.0042 mL,
0.0816 mmol). A brown precipitate formed immediately
(PdBr2). One h later the suspension was filtered and the
filtrate was evaporated to dryness. A light yellow oily residue
was obtained, which was a mixture of 4 (79%), 5 (12%), 6 (7%),
Anal. Calcd for
C28H16Br2F10Pd2S2: C, 34.35; H, 1.65.
Found: C, 34.06; H, 1.69.
2b was prepared in a similar way but using the chloro
derivative 1b as starting material.
2b: 19F (CDCl3, δ, 282 MHz), -162.1/-162.7* (b, Fmeta),
-156.0/-156.5* (b, Fpara), -142.7/-142.5* (b, Fortho); 1H NMR
(CDCl3, δ, 300 MHz) 8.0/7.8* (m, 2H, Ph), 7.5/7.4* (m, 3H, Ph),
4.03 (b, 1H, CH), 3.12/2.60* (b, 1H, CH2Pf), 2.95/2.30* (b, 1H,
CH2Pf). Anal. Calcd for C28H16Cl2F10Pd2S2: C, 37.77; H, 1.81.
Found: C, 37.33; H, 1.80.
1
and 7 (2%) by analysis of H and 19F NMR spectra and GC-
MS. The rates in parentheses are based on the integration of
19F NMR signals. Separation of these compounds by silica gel
preparative TLC was performed using n-hexane as eluent; four
batches corresponding to compounds 6 (Rf ) 0.60), 7 (Rf )
0.45), 5 (Rf ) 0), and a new derivative 8 (Rf ) 0.30) were
obtained. 4 was not found after the chromatographic separa-
tion.
*: value for the minor diastereoisomer.
P r ep a r a tion of 3. Complex 2a (0.300 g, 0.306 mmol)
dissolved in CH2Cl2 (10 mL) was mixed with PPh3 (0.161 g,
0.612 mmol). After 30 min the yellow solution was evaporated
to 0.5 mL, and ether (5 mL) was added. A yellow solid formed
4: 19F NMR (CDCl3, δ, 282 MHz) -162.2 (m, Fmeta), -155.0
(t, Fpara), -142.0 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz) 7.5
(m, 2H, Ph), 7.4 (m, 3H, Ph), 5.45 (dd, J ) 8.9, 6.4 Hz, 1H,
PfCH2CH), 3.60 (dd, J ) 14.6, 6.4 Hz, 1H, PfCHH′CH), 3.56
(dd, J ) 14.6, 8.9 Hz, 1H, PfCHH′CH); MS (El) m/ z (relative
intensity) 382 [M+(Br81) - 2, 12], 380 [M+(Br79) - 2, 12], 301
(7), 237 (10), 192 (47), 142 (18), 122 (22), 109 (87), 77 (85), 69
(44), 65 (63), 51 (100).
1
(0.419 g, 91% yield). Analysis of H, 13C, 19F, and 31P NMR
spectra indicated that the yellow solid was a mixture of two
isomers 3a and 3b in a ratio of 7.7 to 1.
3a and 3b. Anal. Calcd for C32H23BrF5PPdS: C, 51.12; H,
3.08. Found: C, 50.74; H, 3.08.
8: 19F NMR (CDCl3, δ, 282 MHz) -162.9 (m, Fmeta), -156.1
(t, Fpara), -142.2 (m, Fortho); 1H NMR (CDCl3, δ, 300 MHz) 7.4
(23) Albe´niz, A. C.; Espinet, P.; Foces-Foces, C; Cano, F. H. Orga-
nometallics 1990, 9, 1079.

Insertion of Alkenyl Sulfides into a Pd-Aryl Bond
Organometallics, Vol. 15, No. 23, 1996 5009
Ta ble 3. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for 11
(m, 4H, Ph), 7.3 (m, 6H, Ph), 4.64 (t, J ) 7.8 Hz, 1H,
PfCH2CH), 3.25 (bd, J ) 7.8 Hz, 2H, PfCH2CH); MS (El) m/ z
(relative intensity) 412 (M+, 2), 303 (20), 181 (10), 135 (39),
109 (100), 77 (11), 69 (10), 65 (27), 51 (12).
emp formula
formula wt
T (K)
C56H32Cl4F20Pd4S4
1780.46
293
Cr ysta l Str u ctu r e Deter m in a tion of 11. Crystals of 11
suitable for X-ray diffraction analysis were obtained by
maintaining a solution of 2b in a mixture of CH2Cl2 and Et2O
(1/2) at low temperature for 2 months. The appropriate crystal
of 11 was glued at the end of a glass fiber with epoxy adhesive.
All diffraction measurements were made at room temperature
on a Siemens R3m diffractometer using graphite-monochro-
mated Mo KR X-radiation. Unit cell dimensions were deter-
mined from 28 centered reflections in the range 15.0 < 2θ <
30.0°. Diffracted intensities were measured in a unique octant
of reciprocal space for 3.0 < 2θ < 50.0° by ω Wyckoff scans.
Three check reflections (8 3 1, -3 8 -1, and 2 4 10) remeasured
after every 100 ordinary data showed no decomposition of the
crystal and a variation of ca. (2% over the period of data
collection. Of the 3052 intensity data (other than checks)
collected, 2674 unique observations remained after averaging
of duplicate and equivalent measurements and deletion of
systematic absences (Rint 0.036); of these, 1705 had I > 2σ(I).
An absorption correction was applied based on 272 azimuthal
scan data (maximum and minimum transmission coefficients
were 0.264 and 0.229). Lorentz and polarization corrections
were applied.
wavelength (Å)
cryst syst
space grp
0.71073
tetragonal
I41/a
unit cell dimens
a ) 16.849(3) Å, R ) 90°
b ) 16.849(3) Å, â ) 90°
c ) 21.400(3) Å, γ ) 90°
volume (Å3)
6068(2)
8
1.949
1.580
Z
density (calcd) (Mg/m3)
absorp coeff (mm-1
F(000)
)
3456
cryst size (mm)
θ range for data collectn
(deg)
0.30 × 0.15 × 0.15 mm
1.54-24.98
index ranges
0 e h e 20, 0 e k e 20,
0 e 1 e 25
2874
2674 [R(int) ) 0.0355]
full-matrix least-squares on F2
2673/0/200
reflns collected
indept reflns
refinement method
data/restraints/parameters
goodness-of-fit on F2
final R indices [I > 2σ(I)]
1.517
R1 ) 0.0612, wR2 ) 0.1142
(1705 data)
0.985 and -0.929
largest diff peak and hole
The structure was solved by Patterson and Fourier methods
and refined using the SHELXL-93 program.24 All non-
hydrogen atoms were assigned anisotropic displacement pa-
rameters. All hydrogen atoms were constrained to idealized
geometries and their positions refined riding on their parent
carbon atoms with a common thermal isotropic parameter.
Full-matrix least-squares refinement on F2 of this model (200
parameters) converged to final residual indices R1 ) 0.061,
(e Å-3
)
7.7 (m, 5H, Ph), 4.62 (dd, J ) 11.5, 3.8 Hz, 1H, SCH), 3.31
(dd, J ) 13.9, 11.5 Hz, 1H, PfCHH′), 2.20 (dd, J ) 13.9, 3.8
Hz, 1H, PfCHH′).
Ack n ow led gm en t. We are grateful to the Direccio´n
General de Investigacio´n Cient´ıfica y Te´cnica (Project
PB93-0222) and the Commission of the European Com-
munities (Network “Selective Processes and Catalysis
Involving Small Molecules” CHRX-CT93-0147) for fi-
nancial support. We also thank the Ministerio de
Educacio´n y Ciencia and the AECI/Universidad de
Valladolid for fellowships to Y.-S.L.
wR2 ) 0.114, [for the reflections I > 4s(F)], S ) 1.52 [R1
)
2
∑||Fo| - |Fc||/∑|Fo|; wR2 ) [∑[w(Fo - Fc2)2/∑[w(Fo2)2]1/2; S )
2
[∑w(Fo - Fc2)2/(no. ref - no. par.)]1/2]. Weights, w, were set
equal to [σc2(Fo2) + (gP)2]-1, where P ) [max(Fo2,0) + 2Fc2]/3
and g ) 0.03. Final difference electron density maps showed
no features outside the range +0.98 to -0.93 e Å-3, the biggest
being close to the Pd atom (<1 Å). Crystal data and structure
refinement for 11 are collected in Table 3.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates and isotropic displacement parameters, complete
bond lengths and angles, and anisotropic displacement pa-
rameters (5 pages). Ordering information is given on any
current masthead page.
11: 19F NMR (CDCl3, δ, 282 MHz) -162.0 (m, Fmeta), -155.5
(t, Fpara), -142.4 (b, Fortho); 1H NMR (CDCl3, δ, 300 MHz) 7.4-
(24) SHELXTL version 5.03, Siemens Analytical Xray, Madison, WI,
1994.
OM960406D