Synthesis of Ni(II), Pd(II) and Pt(II) complexes containing chiral phosphino-thiol and -thioether ligands

Article abstract of DOI:10.1039/b209142a

The chiral P,S ligand 1-(diphenylphosphino)butane-2-thioI, L¹H, and its thioether methyl derivative L¹Me have been synthesized. L¹H reacts with divalent Ni, Pd and Pt salts to form phosphinothiolato complexes of general formula [M(L¹)Cl]₂ (1, M = Ni), (2, M = Pd), M(L¹)₂ (3, M = Ni), (4, M = Pd), (5, M = Pt) and M(L¹)(PR₃)X, (6, M = Pd, R = Ph, X = Cl), (7, M = Pd, R = ⁿBu, X = Cl), (8, M = Pt, R = Ph, X = H). Single crystal X-ray crystallography reveals a 'butterfly' shape for the dimeric structures of nickel and palladium complexes, 1 and 2 respectively. The P,S chelate ring, according to solid state structural data and NMR analysis, adopts a preferred δ skew-conformation for the S isomer and a λ conformation for the R isomer. Complex 6 dissociates in chloroform solutions to form the dimeric species 2 and free PPh₃. Thermodynamic parameters for this process have been calculated. The Royal Society of Chemistry 2003.

Full text of DOI:10.1039/b209142a

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Synthesis of Ni(II), Pd(II) and Pt(II) complexes containing chiral
phosphino-thiol and -thioether ligands
Athanasia Dervisi,*a Robert L. Jenkins,a K. M. Abdul Malik,a Michael B. Hursthouseb and
Simon Colesb
a Department of Chemistry, Cardiff University, PO Box 912, Cardiff, UK CF10 3TB.
E-mail: dervisia@cf.ac.uk.
b University of Southampton, Chemistry Department,
EPSRC National Crystallography Service, Southampton, UK
Received 18th September 2002, Accepted 24th January 2003
First published as an Advance Article on the web 10th February 2003
The chiral P,S ligand 1-(diphenylphosphino)butane-2-thiol, L1H, and its thioether methyl derivative L1Me have been
synthesized. L1H reacts with divalent Ni, Pd and Pt salts to form phosphinothiolato complexes of general formula
[M(L1)Cl]2 (1, M = Ni), (2, M = Pd), M(L1)2 (3, M = Ni), (4, M = Pd), (5, M = Pt) and M(L1)(PR3)X, (6, M = Pd,
R = Ph, X = Cl), (7, M = Pd, R = nBu, X = Cl), (8, M = Pt, R = Ph, X = H). Single crystal X-ray crystallography reveals
a ‘butterfly’ shape for the dimeric structures of nickel and palladium complexes, 1 and 2 respectively. The P,S chelate
ring, according to solid state structural data and NMR analysis, adopts a preferred δ skew-conformation for the S
isomer and a λ conformation for the R isomer. Complex 6 dissociates in chloroform solutions to form the dimeric
species 2 and free PPh3. Thermodynamic parameters for this process have been calculated.
thiocyanate, this reaction proceeds with inversion of the
stereogenic centre. The enantiomeric purity of the thiirane was
Introduction
In recent years there has been great interest in developing chiral
bidentate systems as suitable candidates for catalytic precursors
determined by chiral GC to be ≥99%. Subsequent reaction with
diphenylphosphide followed by hydrolysis afforded (S)-L1H.
where only one of the donor atoms is phosphorus. For example,
Attack of the lithiophosphide is regioselective and ring opening
mixed P,O-1 and P,N-donor2 ligands have been extensively
occurs at the least hindered carbon. The corresponding phos-
applied in catalysis and there is a growing interest with respect
phinothioether ligand L1Me was formed by deprotonation of
to potential applications of chiral P,S-ligands.3 Thioether-
L1H by butyllithium and subsequent reaction with methylio-
phosphite and -phosphine ligands have been used in a number
of asymmetric reactions such as hydroformylations, hydro-
dide. Hauptman et al. have previously reported the syntheses
of analogous substituted 2-phosphinoethane thioethers by
genations, allylic alkylations and aminations.4–6 In addition,
following similar procedures.4b
achiral phosphinothiolate ligands have been reported previ-
The main features in the 1H NMR of L1H and L1Me are the
ously to show good regioselectivities in the catalytic formation
methinic proton resonances of the α-protons with respect to
sulfur, which appear at δ 2.69 and 2.65, respectively, as broad
of branched carboxylic esters from styrene.7
P,S ligands consist of two soft donors but break the steric
unresolved signals due to vicinal coupling with the dia-
symmetry of more classical chiral P,P ligands such BINAP and
stereotopic protons at the 2 and 4 positions (Fig. 1) as well as
DIOP. Hence, P,S systems may prove useful in reactions where
1H–31P coupling. Resonances for the methylene protons at the 4
the large steric difference of the two coordination sites of the
position appear as doublets of doublets (dd) and those at the
chelate could influence reaction selectivities by accommodating
2 position as unresolved multiplets in the δ 2.3–2.6 and 1.5–1.9
the more bulky side of the participating ligand adjacent to the
regions, respectively. The thiol proton of L1H resonates at
thiolate. Additionally, the electronic differences of the P and S
δ 1.80, overlapping with one of the H2 protons. In the 13C
donors of the chelate ligand might control reaction selectivities
spectra of LH1 resonances for the diastereotopic axial and
via operation of the trans effect.
In the present study our objectives were to develop efficient
equatorial phenyl groups appear as pairs. The upfield 13C
resonances are assigned to the axial phenyl groups as the
routes for the formation of late transition metal complexes with
JPC couplings are consistently smaller on these signals.10,11
the P,S ligands 1-(diphenylphosphino)butane-2-thiol (L1) and
its methyl thioether derivative L1Me. Such complexes at a later
stage of the project could be tested as catalyst precursors in
selected reactions.
Herein, we report on the synthesis, characterisation and
properties of chiral phosphino-thiol and -thioether bidentate
ligands and their corresponding late transition metal
complexes.
Results and discussion
Fig. 1 Adopted numbering for ligands L1H, L1Me and their respective
complexes.
Ligand synthesis
Both the racemic and S-isomer of L1H were prepared as repre-
sentative examples for this class of ligands, the reaction
sequence for their synthesis is shown in Scheme 1.8 The source
of chirality in this example is based on the hydrolytic kinetic
resolution of epoxides according to Jacobsen and coworkers.9
Conversion of the resolved (R)-1,2-epoxybutane to the corre-
sponding thiirane is achieved by the action of potassium
Synthesis of metal complexes
In order to gain some insight of the coordination properties of
ligands L1H and L1Me we prepared a number of transition
metal complexes with Ni, Pd and Pt. The types of thiolato
complexes obtained from L1H are sulfur-bridged dimeric
species (1, 2), bis-chelating (3, 4, 5) and mixed phosphine
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
D a l t o n T r a n s . , 2 0 0 3 , 1 1 3 3 – 1 1 4 2
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Scheme 1 Reagents and conditions: (i) KSCN, H2O, 3 days; (ii) Ph2PLi, Et2O, H2O, (iii) BuLi, MeI, thf.
Scheme 2 Reagents and conditions: (i) 2 equiv. L1H, CH2Cl2; (ii) Pd(CH3CN)2Cl2, toluene, 110 ЊC, 1 day; (iii) 2 equiv. PR3, CH2Cl2, 2 h, (iv) 2 equiv.
L1H, CH2Cl2.
Scheme 3 Reagents and conditions for the synthesis of the platinum complexes 5 and 8.
species (6, 7, 8) as shown in Schemes 2 and 3. The same com-
plexes were prepared with the resolved ligand, (S)-L1H, in
order to assign spectroscopically the meso and rac dia-
stereomeric isomers formed with the racemic ligand, L1H. The
thiolato complexes of L1H were prepared by the simple
addition of the phosphinothiol ligand L1H to a solution of
the metal precursor. Formation of HCl from elimination of the
acidic thiol hydrogen did not appear to affect adversely the
reaction. Alternatively the palladium complexes 2 and 6 may be
prepared from complex 4, as illustrated in Scheme 2. The ligand
L1Me affords the neutral phosphinothioether complex 9.
equimolar amounts. Alternatively, 2 may be obtained from
[Pd(L1)]2 4, and an equimolar amount of a palladium
dichloride source, for example Pd(CH3CN)2Cl2 (Scheme 2). As
it was previously observed with the corresponding nickel
complex only one singlet appears in its 31P spectrum at δ 40.9.
Crystallographic data were obtained for both complexes
confirming their dimeric structures as shown in Figs. 2 and 3,
respectively, where the five-membered chelates adopt an S(δ)
[M(L1)Cl]2 complexes
Thiolato ligands are well known in forming sulfur-bridged
species in the absence of other suitable ligands. Several methods
have been used for preparing sulfur-bridged dimers of d8 transi-
tion metals. The palladium and platinum sulfur-bridged dimers
of a ferrocenyl phosphinothiolato ligand were prepared by
reacting the free thiol ligand with M(CH3CN)2Cl2 (M = Pd,
Pt).5a The complex [Pd(dpppt)Cl]2, dppptH = Ph2P(CH3)2SH,
was prepared by reacting Pd(PPh3)2Cl2 and dppptH without
formation of the expected triphenylphosphine complex Pd-
(dpppt)(PPh3)Cl.7 Sulfur-bridged dimers have also been
obtained by cleavage of the S–C thioether bond, the complex
[Pd{PCy2CH2CH(CH3)S}Cl]2 was obtained according to this
method.4b
Fig.
2
ORTEP drawing of [Ni(L1)Cl]2 (1) with 40% thermal
probability ellipsoids. Hydrogen atoms and water molecule are omitted
for clarity.
The nickel dimer [Ni{Ph2PCH2CH(Et)S}Cl]2 (1) was isolated
as a deep red solid after reacting equimolar amounts of NiCl2ؒ
6H2O and L1H in a dichloromethane solution. Starting from
racemic L1H the dimer obtained reveals only one singlet in its
31P{1H} spectrum at δ 37.2 instead of the expected two singlets
due to the diastereomeric meso and rac isomers of 1. The exist-
ence of two different stereoisomers was also not observed in
1
both H and 13C NMR spectra of 1. This behaviour may be
attributed to the long distance between the two stereogenic
centres. However, it is possible that only one diastereomer exists
in solution, although the large distance between stereogenic
centres precludes a rigorous assignment.
The analogous sulfur-bridged dimer [Pd(L1)Cl]2 (2) was
isolated after the reaction of L1H with Pd(PhCN)2Cl2 in
Fig.
3
ORTEP drawing of [Pd(L1)Cl]2 (2) with 40% thermal
probability ellipsoids. Hydrogen atoms are omitted for clarity.
D a l t o n T r a n s . , 2 0 0 3 , 1 1 3 3 – 1 1 4 2
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Table 1 Crystallographic data for 1, 2, 4, 5, 6 and 9
Compound
1
2
4
cis-5
trans-6
9
Empirical formula
Formula weight
C32H36.4Cl2Ni2O0.20P2S2
738.59
C32H36Cl2P2Pd2S2
830.37
C32H36P2PdS2
653.07
C32H36P2PtS2
741.76
C34H33Cl P2PdS
677.45
C17H21Cl2PPdS
465.67
Temperature/K
Crystal system
Space group
120(2)
120(2)
Monoclinic
P21/c
150(2)
150(2)
Monoclinic
C2/c
293(2)
Monoclinic
P21/n
150(2)
Monoclinic
P21/n
Triclinic
Triclinic
¯
¯
P1
P1
a/Å
b/Å
c/Å
α/Њ
11.523(2)
12.031(2)
13.325(3)
76.37(3)
79.93(3)
65.29(3)
1624.9(6)
2
14.955(3)
14.401(3)
15.281(3)
90
92.33(3)
90
3288.3(11)
4
1.677
9.0549(18)
10.873(2)
15.972(3)
109.06(3)
90.56(3)
101.02(3)
1454.4(5)
2
20.104(4)
9.885(2)
15.240(3)
90
103.69(3)
90
2942.7(10)
4
1.674
8.509(2)
10.5654(13)
17.553(2)
90
99.021(14)
90
1558.5(4)
2
1.444
8.8678(18)
15.492(3)
13.085(3)
90
95.49(3)
90
1789.4(6)
4
1.729
β/Њ
γ/Њ
V/Å3
Z
Dc/g cmϪ3
Crystal shape;
colour
1.510
Prism; dark red
1.491
Plate; orange
Plate; yellow
Needle; colourless
Prism; orange
Block; yellow
GoF on F 2
R
1.114
0.0299
0.0701
1.001
0.0441
0.0875
1.010
1.026
0.0393
0.0990
1.060
0.0311
0.0650
1.031
0.0331
0.0882
0.0682
0.1645
0.00(4)
Rw
Absolute structure
parameter
Table 2 Selected bond lengths (Å) and angles (Њ) in complexes 1 and 2
[Ni(dppet)Cl]2 (10), dppetH = Ph2P(CH2)2SH, where the corre-
sponding Ni–S distances were 2.230(3) and 2.164(3) Å, respect-
ively.14 The Ni–Ni distance of 2.7583(12) Å is somewhat longer
than that of 10 at 2.679(1) Å.
1 (M = Ni)
3 (M = Pd)
P(1)–M(1)
P(2)–M(2)
S(1)–M(1)
S(1)–M(2)
S(2)–M(2)
S(2)–M(1)
M(1)–Cl(1)
M(2)–Cl(2)
M(1)–M(2)
2.1460(7)
2.1591(9)
2.1583(9)
2.2378(9)
2.1713(7)
2.2303(7)
2.1835(9)
2.1853(7)
2.7583(12)
2.2469(11)
2.2570(12)
2.2732(10)
2.3918(12)
2.2746(11)
2.3616(11)
2.3326(11)
2.3562(11)
3.0266(9)
The hinged structure of the palladium dimer 2 brings the two
metal atoms in close proximity (3.0266(9) Å) but no bonding
interactions are observed. The S–Pd–S angles, 80.56(4)
and 79.88(4)Њ, are at the lower end of the literature range of
80–88Њ.4b,5a,7 The Pd–S–Pd angles of 80.86(4) and 81.48(4)Њ,
respectively, are in good agreement with those reported for the
7
related complexes [Pd(dpppt)Cl]2 and [Pd(Cy2PCH2CH(Me)-
S)Cl]2.4b As was the case for the nickel dimer 1 two different sets
of M–S distances are observed one trans to the phosphorus
atom and one trans to the chlorine atom. The average Pd–S
bond length trans to phosphorus is 2.3767 Å compared with
2.2739 Å trans to the chloride ligands.
M(1)–S(1)–M(2)
P(1)–M(1)–S(1)
S(1)–M(1)–S(2)
P(2)–M(2)–Cl(2)
M(2)–S(2)–M(1)
S(2)–M(2)–Cl(2)
S(2)–M(2)–S(1)
Cl(2)–M(2)–S(1)
77.70(4)
88.52(4)
80.06(4)
94.76(3)
77.59(3)
176.412(19)
79.61(4)
96.93(4)
80.86(4)
87.10(4)
80.56(4)
97.78(4)
81.48(4)
175.08(4)
79.88(4)
96.51(4)
M(L1)2 complexes
The most common type of coordination compounds formed
between phosphinothiolate ligands and the group 10 metals are
bis-chelating complexes of the type M(P–S)2. Most of the bis-
chelating complexes reported so far adopt a trans arrangement
around the metal centre due to the bulky nature of the PPh2
part of the chelate. However, there are a few examples even with
nickel, the smallest metal of the triad, that a cis geometry is
preferred. The unsubstituted analogue of L1, dppet, forms trans
complexes with nickel and palladium although a cis arrange-
ment is adopted in the bridging thiolato complex [Ni(dppet)2-
Mo(CO)4].7,12,15,16 The platinum analogue, Pt(dppet)2, has been
reported to adopt a cis geometry.16 The nickel and palladium
complexes of the ligand 2-(dimethylphosphino)ethane-1-thiol-
ato (dmsp) are known as the trans isomers, in contrast, the
platinum complex has a cis geometry.16 Bis-chelating com-
plexes of the nickel triad have also been obtained with the
o-(diphenylphosphino)benzenethiolate ligand. The palladium
complex has been found to exist in solution as an equilibrium
cis–trans mixture.17,18
The bis-chelating complex [Ni{Ph2PCH2CH(Et)S}2] (3) was
isolated as a green solid from the reaction of Ni(acac)2 and two
equivalents of L1H in toluene using acacϪ as a base. The
diastereomeric mixture obtained contained only trans-3 in
approximately equal quantities of meso and rac isomers. The
31P{1H} NMR spectrum of 3 in CDCl3 consisted of two distinct
singlets, one at δ 53.1 for the meso isomer and one at δ 54.2 for
the rac isomer. Assignment of these signals was made after
comparison with the spectrum of the same complex obtained
skew conformation. Collection data and refinement parameters
are listed in Table 1 and selected bond lengths and angles are
presented in Table 2. In both complexes the geometry around
the two metal atoms is distorted square planar and the molecule
is bent about the S–S axis adopting a ‘butterfly’ core structure
with a syn orientation of the sulfur substituents. For µ-SRϪ
complexes both syn and anti orientations of the sulfur substi-
tuents have been observed.5a The preference in a syn orientation
of the µ-SRϪ substituents in complexes 1 and 2 is likely to arise
from the prevailing skew conformation that places the ethyl
substituents of the metallacycle in the sterically favoured
pseudo-equatorial position. The dihedral angle defined by the
two MS2 planes is 110.88(3)Њ for complex 1, one of the smallest
reported so far, and 116.02(4)Њ for complex 2.
For the nickel dimer the S–Ni–S angles are 80.06(4) and
79.61(4)Њ, respectively, and are at the lower end of the literature
range of 80–86Њ.12 For similar complexes the rather small S–Ni–
S angles and syn orientation of the sulfur substituents have
been attributed to the repulsive interaction between the lone
pairs on the sulfur atom and metal d-electrons.12 The Ni–S
bond lengths trans to phosphorus are 2.2378(9) and 2.2303(7)
Å, respectively, and compare well with other reported Ni–S
distances for bridging thiolates.13 However, the Ni–S distances
trans to the chloride, 2.1583(9) and 2.1713(7) Å, are much
shorter due to the lower trans influence of the chloride. A simi-
lar trend was observed for the analogous thiolate complex
D a l t o n T r a n s . , 2 0 0 3 , 1 1 3 3 – 1 1 4 2
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Table 3 Selected bond lengths (Å) and angles (Њ) in 4
Molecule A
Molecule B
P(1)–Pd(1)
P(2)–Pd(1)
S(1)–Pd(1)
S(2)–Pd(1)
S(1)–C(14)
S(2)–C(17)
2.298(3)
2.297(2)
2.326(2)
2.319(2)
1.843(8)
1.846(8)
P(1)–C(1)
P(1)–C(7)
P(1)–C(13)
P(2)–C(20)
P(2)–C(21)
P(2)–C(27)
1.810(9)
1.824(8)
1.820(8)
1.815(7)
1.810(8)
1.830(9)
P(3)–Pd(2)
P(4)–Pd(2)
S(3)–Pd(2)
S(4)–Pd(2)
S(3)–C(46)
S(4)–C(62)
2.299(3)
2.295(2)
2.327(2)
2.324(2)
1.854(8)
1.830(8)
P(3)–C(33)
P(3)–C(39)
P(3)–C(45)
P(4)–C(49)
P(4)–C(55)
P(4)–C(61)
1.825(8)
1.819(10)
1.830(8)
1.826(8)
1.828(9)
1.814(7)
P(2)–Pd(1)–P(1)
P(2)–Pd(1)–S(2)
P(1)–Pd(1)–S(2)
177.31(11)
85.86(9)
93.36(9)
P(2)–Pd(1)–S(1)
P(1)–Pd(1)–S(1)
S(2)–Pd(1)–S(1)
94.85(9)
85.99(9)
178.45(14)
P(4)–Pd(2)–P(3)
P(4)–Pd(2)–S(4)
P(3)–Pd(2)–S(4)
177.13(10)
85.84(9)
93.45(9)
P(4)–Pd(2)–P(3)
P(4)–Pd(2)–S(4)
P(3)–Pd(2)–S(4)
177.13(10)
85.84(9)
93.45(9)
from the S isomer of L1H, which should be identical with that
from the rac isomer. After crystallisation from slow diffusion of
petroleum ether into a CH2Cl2 solution of 3 the rac isomer
crystallises out preferentially, in this way it is possible to separ-
ate the two diastereomers. The trans arrangement of the ligands
around the metal centre in CDCl3 solutions was confirmed
from their 13C NMR spectrum, which revealed apparent triplets
for the C2–C4 carbons of the chelate ring and aromatic carbons.
Reaction of two equivalents of L1H with Pd(PhCN)2Cl2 or
Pd(OAc)2 in dichloromethane affords the bis-chelating, thiolato
complex [Pd(L1)]2 4. In agreement with previous observations
for complex 3 the diastereomeric mixture of 4 contains only the
trans isomer in approximately equal quantities of meso and rac
isomers. The 31P{1H} NMR spectrum of 4 in CDCl3 consisted
of two distinct singlets, one at δ 47.4 for the meso isomer and
one at δ 45.3 for the rac isomer, as assigned after comparison
with spectra of (S)-4. The 13C{1H} NMR spectrum of 4
confirms the trans arrangement of the ligands around the
metal centre in CDCl3 solutions since apparent triplets for the
α- and β-carbons of the chelate ring and aromatic carbons are
observed. However, 31P{1H} NMR spectra recorded in polar
solvents such as deuterated acetonitrile and methanol revealed
the existence of cis/trans geometrical isomers, not observed in
CH2Cl2 solutions, in ca. 1 : 2 and 1 : 1 ratios, respectively. Form-
ation of cis isomers despite the unfavourable steric interaction
of the phosphine groups is attributed to the higher trans influ-
ence of the phosphorus versus the sulfur donor which dis-
favours the two phosphine groups being placed trans to each
other. Attempts to isolate the cis isomer after crystallization
were unsuccessful, implying that the kinetics of cis/trans isom-
erisation are more rapid than those of crystallisation.17
Fig. 4 ORTEP drawing of molecule B of [Pd(L1)2] (4) with 40%
thermal probability ellipsoids. Molecule A is omitted for clarity.
by crystallisation. In the 31P{1H} NMR spectrum of 5 two sets
of singlets in a 2 : 3 ratio were observed at δ 47.6 (rac, JPtP
=
2758.6 Hz), 50.5 (meso, JPtP = 2630 Hz) for the trans isomers
and δ 38.2 (rac, JPtP = 2818.23 Hz), 42.3 (meso, JPtP = 2824.18
Hz) for the cis isomers. Assignment of the rac and meso isomers
was made after comparison with spectra of (S)-5. Cis and trans
isomers were identified from their 13C NMR spectra, which for
the trans-rac isomer reveal apparent triplets in the aromatic
region. In addition, for the cis-rac complex all six aromatic
resonances are observed in the 1H NMR spectrum.
Slow crystallisation from CH2Cl2–petroleum ether afforded
the less soluble cis-rac isomer, as later confirmed by X-ray dif-
fraction. The trans-rac isomer was isolated by crystallisation
from CH3CN–Et2O. In this case the deprotonation of the thiol
ligand was somewhat surprising since it has been found that for
the formation of platinum–thiolato complexes the presence of a
base is necessary.20
Complex 5 was also obtained from the reaction of Pt(PPh3)4
and two equivalents of L1H in CH2Cl2 (Scheme 3). The reaction
is thought to proceed via initial formation of the Pt–H complex
8 and subsequent molecular hydrogen elimination. The high cis/
trans ratio (4 : 1) obtained under these reaction conditions is
surprising since CH2Cl2 is a solvent of low polarity and thus
trans complexes are expected to be more stable. This predomin-
ance of the cis isomer may be associated with the reaction
mechanism leading to the formation of the thiolate complex.
Colourless crystals of the cis-rac isomer suitable for X-ray
diffraction were obtained after fractional crystallisation from
a diastereomeric mixture of 5. Cis-5 crystallises in the C2/c
centrosymmetric space group and in the unit cell 5 is ordered in
layers of S(δ) and R(λ) enantiomers. Selected bond lengths and
Complex 4 was also isolated by the reaction of Pd(PPh3)4
with two equivalents of L1H. The reaction is thought to pro-
ceed via the oxidative addition of L1H to palladium(0) to form
an unstable intermediate hydride complex which reacts further
with free L1H to form 4. The same reactivity has been previ-
ously observed with the phosphinothiol ligands dppet and
dpppt.7 As we shall see in the discussion for the platinum com-
plexes an analogous platinum–hydride intermediate has been
characterised spectroscopically.
From the reaction of Pd(OAc)2 with (S)-L1H, orange crystals
of (S)-4 suitable for X-ray crystallographic analysis were
obtained after slow diffusion of petroleum ether into a di-
chloromethane solution. The unit cell comprises two independ-
ent molecules (A and B) which show no anomalies in their
structural data summarised in Table 3. An ORTEP view of
molecule B is presented in Fig. 4 showing the trans arrangement
and δ skew conformation of the two ligand fragments around
the metal centre. The Pd–P bonds at 2.298(3) and 2.297(2) Å are
close to those reported for the analogous complex with the
2-(diphenylphosphino)thiophenolato ligand, Ph2P(C6H4S)19
and the Pd–S bonds at 2.326(2) and 2.319(2) Å are within the
expected range.
The platinum complex Pt(L1)2 5 was prepared from the reac-
tion of PtCl2 and L1H in hot acetonitrile. This method affords
both cis and trans geometric isomers which were then separated
D a l t o n T r a n s . , 2 0 0 3 , 1 1 3 3 – 1 1 4 2
1136

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Table 4 Selected bond lengths (Å) and angles (Њ) in cis-5a
(1)
P(1)–Pt(1)
S(1)–Pt(1)
C(1)–P(1)
2.2560(12)
2.3284(11)
1.815(4)
C(13)–P(1)
C(7)–P(1)
C(14)–S(1)
1.838(4)
1.811(4)
1.848(4)
P(1)–Pt(1)–P(1i)
P(1)–Pt(1)–S(1i)
99.98(6)
172.77(4)
P(1)–Pt(1)–S(1)
S(1i)–Pt(1)–S(1)
86.53(4)
87.16(5)
a Symmetry transformations used to generate equivalent atoms:
(i) Ϫxϩ1, y, Ϫzϩ1/2.
which suggests that the entropy dependence of this process is
rather small. The thermodynamic parameters determined show
a rather small dissociation constant for the dimer formation
with a value of K298 = 5.6 × 10Ϫ4 M. Dimer formation has also a
small but negative value for the free Gibbs energy (∆GЊ) at
Ϫ18.5 kJ molϪ1 and a large negative value for the entropy
change (∆SЊ = Ϫ153.44 kJ molϪ1 KϪ1). This behaviour contrasts
with that reported for the related complex Pd(dppet)(PPh3)Cl
where dissociation to a palladium dimer was not observed.7 In
the same study it was reported that under similar conditions the
ligand dpppt does not form the expected triphenylphosphine
complex Pd(dpppt)(PPh3)Cl, instead the dimer [Pd(dpppt)Cl]2
forms quantitatively. These differences were attributed by the
authors to the greater chelate size of dpppt complexes. How-
ever, when comparing complexes of dppet and L1 where the
chelate size is the same such differences in the ability to form
sulfur bridged complexes may be attributed to the higher
trans influence of L1.
angles for 5 are shown in Table 4. In Fig. 5 an ORTEP view of 5
shows the interfering phenyl groups in near parallel positions.
The cis orientation of the two bulky phosphine groups results in
the opening up of the P–Pt–P angle to 99.98(6)Њ and compres-
sion of the S–Pt–S and P–Pt–S angles to 87.16(5) and 86.53(4)Њ,
respectively. The Pt–P and Pt–S bonds at 2.2560(12) and
2.3284(11) Å, respectively, are amongst the shortest ones
reported for platinum complexes bearing a phosphine ligand
trans to a thiolate.21
The above observations prompted us to explore the lability of
L1 complexes in the presence of other phosphorus containing
ligands. Under similar conditions that afford 6, n-tributyl-
phosphine and triethylphospite were tested. In the case of
P(nBu3) trans-[Pd{Ph2PCH2CH(Et)S}(PnBu3)Cl], 7, together
with ∼6% of the cis isomer was obtained without formation
of the palladium dimer 2. However, with P(OEt)3 the only
product isolated was pure dimer 2. 31P{1H} NMR spectra
recorded during this reaction reveal that a transient complex
analogous to 6 is also formed with P(OEt)3, this assignment was
made on the basis of the characteristic JP–P values for trans
phosphines.
Although we have not carried out kinetic experiments, com-
plex 11 is a likely intermediate in the dissociation of complex 6
Fig. 5 ORTEP drawing of [Pt(L1)2] (5) with 40% thermal probability
ellipsoids.
M(L1)(PR3)X complexes
Thephosphinothiolatocomplex[Pd{Ph2PCH2CH(Et)S}(PPh3)-
Cl] 6 has been prepared by the reaction of equimolar amounts
of L1H, Pd(PhCN)2Cl2 and PPh3. Alternatively, 6 can be pre-
pared from the reaction of complex 2 with two equivalents of
PPh3 (Scheme 2). According to the room-temperature 31P{1H}
NMR data in CDCl3, the equilibrium mixture of 6 contains the
trans isomer as the major product with ca. 6% of the cis isomer
present in solution. The 31P{1H} NMR spectrum of 6 reveals
two doublets at δ 50.3 (L1) and δ 24.0 (PPh3) with a large coup-
in agreement with five-coordinate species usually suggested for
substitution reactions in d8 transition metal complexes.22 The
reactions with P(nBu3) and P(OEt)3 also agree with such an
intermediate formed. The ligands S, P and Cl retain their
relationship in both the tbp intermediate 11 and the initial
complex (e.g. trans-6) leaving the ligands L, P and incoming
thiolate in the trigonal plane of 11. In the case of 7 the trans
effect of the ligands in the equatorial plane increases in the
order: P(nBu3) > PPh2R > ϪSR and as a result the leaving
group is the thiolate and intermediate 11 reverts to complex 7.
When L = P(OEt)3, triethylphospite becomes the leaving
group as it has the lower trans-effect of the three equatorial
ligands. PPh3 falls in between these two situations and an equi-
librium of monomer 6 and dimer 2 is observed. Thus it may be
suggested that formation of monomeric complexes depends on
the trans-effect of the monodentate neutral ligand (L), which
must be greater than that of the thiolate in order to prevent
sulfur-bridged dimers formed.
2
ling constant, JPP = 460 Hz, characteristic of a trans arrange-
ment of the two phosphorus atoms. The cis isomer of 6 displays
two doublets in the 31P{1H} NMR spectrum positioned at
δ 57.5 (L1) and δ 23.0 (PPh3), respectively, with a significantly
smaller coupling constant, 2JPP = 13.4 Hz.
Complex 6 dissociates in CDCl3 solutions to the palladium
dimer 2 and free PPh3, this dissociation process is shown in
eqn. (1).
In order to obtain thermodynamic parameters for this dis-
1
sociation process variable temperature 31P{1H} and H NMR
spectra were recorded in the temperature range Ϫ40 to ϩ60 ЊC.
At Ϫ40 ЊC signals only due to cis- and trans-6 are detected, but
as the temperature was raised signals due to free PPh3 and
dimer 2 appear that steadily increase with temperature. The cis/
trans ratio did not appear to change in that temperature range
D a l t o n T r a n s . , 2 0 0 3 , 1 1 3 3 – 1 1 4 2
1137

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Table 5 Selected bond lengths (Å) and angles (Њ) in trans-6
Table 6 Selected bond lengths (Å) and angles (Њ) for 9
Pd(1)–S(1)
Pd(1)–P(1)
Pd(1)–P(2)
Pd(1)–Cl(1)
S(1)–C(2)
P(1)–C(5)
2.278(2)
2.283(2)
2.344(2)
2.345(2)
1.847(6)
1.816(3)
P(1)–C(1)
P(1)–C(11)
P(2)–C(17)
P(2)–C(23)
P(2)–C(29)
1.816(6)
1.825(3)
1.822(3)
1.825(4)
1.829(3)
P(1)–Pd(1)
S(1)–Pd(1)
Cl(1)–Pd(1)
Cl(2)–Pd(1)
C(1)–C(4)
C(1)–S(1)
2.2441(7)
2.2688(7)
2.3713(7)
2.3037(7)
1.512(4)
1.846(3)
C(4)–P(1)
C(5)–P(1)
C(5)–P(1)
C(11)–P(1)
C(17)–S(1)
1.840(3)
1.819(2)
1.819(2)
1.809(2)
1.810(3)
S(1)–Pd(1)–P(1)
S(1)–Pd(1)–P(2)
P(1)–Pd(1)–P(2)
85.57(6)
88.07(6)
173.61(6)
S(1)–Pd(1)–Cl(1)
P(1)–Pd(1)–Cl(1)
P(2)–Pd(1)–Cl(1)
176.98(8)
93.15(6)
93.17(6)
P(1)–Pd(1)–S(1)
P(1)–Pd(1)–Cl(2)
S(1)–Pd(1)–Cl(2)
P(1)–Pd(1)–Cl(1)
S(1)–Pd(1)–Cl(1)
86.98(3)
93.89(3)
177.75(2)
174.37(2)
88.18(3)
C(11)–P(1)–Pd(1)
C(5)–P(1)–Pd(1)
C(4)–P(1)–Pd(1)
C(17)–S(1)–C(1)
C(17)–S(1)–Pd(1)
118.88(8)
114.30(8)
105.64(9)
98.90(15)
106.66(12)
Orange crystals of trans-6 were isolated from the slow diffu-
sion of petroleum ether into a dichloromethane solution of 6.
Selected bond lengths and angles are collected in Table 5. The
structure of trans-6 is illustrated in Fig. 6 showing the S isomer
adopting the δ skew conformation. The Pd–P, Pd–S and Pd–Cl
bonds around the coordination plane are close to the values
reported for the analogues complex [Pd(dppet)(PPh3)Cl].7
δ 25.38 (JPP = 10 Hz, JPtP = 3036.2 Hz) for PPh3 and δ 52.26
(JPP = 10 Hz, JPtP = 1880.1 Hz) for L1. Accordingly, in 1H NMR
a doublet of doublets appears for the hydridic proton at δ Ϫ3.4
(JHP = 192.1 Hz, JHP = 24.2 Hz, JHPt = 986.4 Hz). The
difference in the exchange rates of PPh3 in the trans and cis
isomers of 8 may be attributed to the higher trans-effect of the
PPh2 than the thiolate entity in L1. In the trans isomer of 8 the
PPh3 is trans to the phosphine ligand and as a result becomes
more labile than in cis-8 where it is trans to the thiolate. The
same fluxional behaviour of coordinated PPh3 was observed
previously in the dissociation of the complex Pd(L1)(PPh3)Cl to
the palladium dimer 2 and free PPh3.
trans
cis
Pd(L1Me)Cl2
Reaction of L1Me with Pd(PhCN)2Cl2 afforded the palladium
dichloride complex [Pd(L1Me)Cl2] 9, with the phosphino-
thioether ligand bonded in a chelating fashion as illustrated
in the crystal structure shown in Fig. 7. Upon complexation,
a shift of the 31P{1H} NMR signal of L1Me from δ Ϫ20.3 to
δ ϩ52.1 is observed. The phosphinothioether complex 9 is spar-
ingly soluble in common organic solvents thus making it dif-
1
ficult to obtain good quality NMR spectra, a noisy H NMR
spectrum was obtained from acetonitrile-d3.
Fig. 6 ORTEP drawing of [Pd(L1)(PPh3)Cl] (6) with 40% thermal
probability ellipsoids. Hydrogen atoms are omitted for clarity.
As we saw earlier from the reaction of L1H with Pd(PPh3)4
a palladium–hydride intermediate was not detected and only
the bis-chelating complex 4 was isolated. However, under the
same conditions the platinum–hydride complex 8 was formed
from the oxidative addition of L1H to Pt(PPh3)4. The reaction is
best carried out in aromatic solvents (benzene or toluene) since
in dichloromethane solutions the bis-chelating complex 5 is
quantitatively formed, as illustrated in Scheme 3. The hydride
complex is stable in aromatic solutions even with excess of
L1H (1.5 equivalents) present and it is only after several
days that complex 5 is observed in solution. Trans-8 is the
major isomer with ∼10% of the cis isomer present in toluene
solutions.
The main drawback of this synthetic approach is the difficult
separation of 8 from free PPh3 since they display comparable
solubilities in hydrocarbon solutions. However, the 1H and
31P{1H} NMR data collected show unambiguously the form-
ation of 8. Due to the large excess of PPh3 present (threefold
excess with respect to 8) rapid exchange is observed between
coordinated and free PPh3. As a result, signals for trans-8 in the
31P{1H} NMR spectrum are broad (w1/2 = 19 Hz for L1) and no
coupling is observed between the coordinated L1 and PPh3 lig-
ands. The 31P{1H} NMR resonance for L1 is observed at δ 54.15
(JPtP = 2921.6 Hz) as a singlet whereas the PPh3 resonance is
coalescing with that of the free ligand at δ 7. This fluxional
process can be observed in the 1H NMR spectrum of trans-8 as
well, where the hydride resonance appears as a broad singlet at
δ Ϫ6.70 (JPtH = 950 Hz). In contrast, the cis isomer does not
show the same fluxional behaviour, both 31P{1H} and 1H NMR
spectra show the expected coupled signals. In 31P{1H} NMR
two doublets appear with their respective platinum satellites at
Fig. 7 ORTEP drawing of [Pd(L1Me)Cl2] (9) with 40% thermal
probability ellipsoids.
The structure of complex 9 was verified by X-ray structural
determination from yellow crystals grown by diethyl ether dif-
fusion in a dichloromethane solution. Selected bond lengths
and angles are given in Table 6. In the solid state 9 adopts the
more sterically favoured conformation which places the syn Ph
and Et groups in a pseudo-equatorial position and the Me sub-
stituent of sulfur pseudo-axial (Fig. 7). The same orientation of
the sulfur substituent has been previously observed in similar
complexes of P,S ligands, however in solution slow inversion of
the sulfur has been observed.4b,5b,23
D a l t o n T r a n s . , 2 0 0 3 , 1 1 3 3 – 1 1 4 2
1138

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3
Conformational solution NMR studies
3J(H3,H4ax) and J(H3,H4eq) at 13.8 and 3.8 Hz, respectively,
have again values which agree with an axial and equatorial
arrangement of the H4ax and H4eq protons with respect to H3. In
the aromatic region signals for the pseudo-axial and pseudo-
equatorial protons are overlapping, however, in the 13C NMR
spectrum separate sets of aromatic resonances are observed for
the pseudo-axial and pseudo-equatorial aryl rings.
A full assignment of the proton resonances of the complexes
was made on the basis of a combination of H1H,31P1H and
1
195Pt1H (for 5 and 8) long-range correlations, together with two-
dimensional COSY experiments. The P,S chelate conformation
in solution was determined by taking into consideration the
dihedral angle dependence of the vicinal coupling constants
The P,S chelate conformation in solution for the platinum
complex 5, was determined for the cis-rac isomer only from the
3
3J(H,H) and J(Pt,H) of the chelate ring protons H3 and H4,
according to the Karplus relation. As shown in Scheme 4 signifi-
cantly different vicinal couplings are expected between an S(δ)
1
four possible isomers. In the H NMR spectrum of 5 coupling
to platinum is observed only for the methylene proton, H4
,
and an S(λ) conformation. In the former case J(H3,H4ax) ӷ
3
eq
which resonates at δ 2.72 with a 3J(Pt,H) value of 66.4 Hz. This
is in accordance with an adopted S(δ)/R(λ) conformation where
the pseudo-equatorial proton is trans to the platinum atom,
3J(H3,H4eq), due to the trans arrangement of the H3 and H4
ax
protons. Whereas in an S(λ) conformation both H4 protons are
gauche with respect to H3 and consequently 3J(H3,H4ax) ≈
3J(H3,H4eq).
whereas H4 and H3 protons are nearly at right angles with it
ax
and thus close to the expected minimum in the Karplus
relation. In accordance with our previous observations there is
a large difference in the values for the vicinal couplings of H4
ax
and H4 protons to H3, at 12.1 and 2.4 Hz, respectively. The
eq
NOEdiff spectrum shows an interaction between H4 and H10
ax
(Fig. 1), the ortho proton of the pseudo-equatorial phenyl ring,
but no interaction between the ethyl group with the aromatic
rings again in agreement with an adopted S(δ)/R(λ) conform-
ation. In the aromatic region six separate, well-defined signals
are visible assigned to the six different types of protons of the
pseudo-axial and pseudo-equatorial phenyls.
Scheme 4 Newman projection down the C3–C4 bond of the fragment
3
3
ML1, showing the dihedral angle relation for J(H3, H4ax), J(H3, H4
)
eq
The 1H NMR spectrum of 6 reveals two separate ddd for the
axial and equatorial H4 protons at δ 2.44 and 2.84, respectively.
The vicinal coupling constants of H4 and H4 to H3 are 11.6
and 3J(Pt, H4eq). Although only the S(δ) and S(λ) conformers are
pictured here, the relation between R(λ) and R(δ) is identical.
ax
eq
Due to the lack of C2 symmetry in the L1 ligand if the chelate
ring is interconverting between a λ and δ conformation two
different magnetic environments should be observed (two dia-
stereomers). NMR data though show only one set of reson-
ances (axial and equatorial) for the diastereotopic Ph and
methylene protons, which suggests that only one skew conform-
ation is adopted in solution for each optical isomer of L1. For
the discussion that is following it will be useful to note the
nomenclature shown in Fig. 1.
and 3.5 Hz, respectively.
Conclusions
A new chiral P,S ligand and its coordination chemistry have
been described. L1 reacts with group 10 metals to form analo-
gous complexes with that of the homologue ligand dppet.
However, substitution at the ethylene backbone of L1 makes the
λ and δ conformers no longer thermodynamically equivalent.
Spectroscopic evidence and crystallographic data show that the
chelate ring in these complexes adopts the preferred S(λ)/R(δ)
conformations both in the solid state and in solution. This pre-
organisation of the P,S ligand around the metal centre might
prove useful in asymmetric transformations. Unlike dppet, both
cis and trans isomers were observed for the palladium and plat-
inum complexes of L1 in solution,7 with the relative cis/trans
ratio depending on the polarity of the solvent. The complex
Pd(L1)(PPh3)Cl dissociates in solution to form the dinuclear
complex [Pd(L1)Cl]2. In contrast, dissociation of triphenyl-
phosphine was not observed in the analogous complex of dppet
demonstrating the better σ-donor ability of L1 when compared
to dppet. Oxidative addition of the S–H bond to a Pt(0) or a
Pd(0) complex was observed in the synthesis of the complexes
Pt(L1)(PPh3)H (8) and Pd(L1)2; where an unstable Pd–H inter-
mediate complex analogous to 8 was postulated for the form-
ation of Pd(L1)2. Addition of the S–H bond to zerovalent plat-
inum complexes has been previously reported by Real et al. for
cysteine derivatives.24 We are currently exploring applications
of L1 and other derivatives in asymmetric catalysis.
The 1H NMR spectrum of 1 reveals well-resolved signals for
the diastereotopic H2 and H4 methylene protons. H4ax resonates
at δ 2.30 and its signal splits into an apparent triplet of doub-
lets. The triplet splitting is due to the similar values for geminal
and vicinal coupling to protons H4 and H3 respectively, at
eq
13.5 Hz, whereas the doublet arises from geminal coupling to
phosphorus, 6.6 Hz, as determined from its 1H{31P} NMR
spectrum. The methylene proton, H4eq, gives a doublet of doub-
lets of doublets (ddd) at δ 2.72, which collapses into a dd in the
phosphorus decoupled spectrum, with a geminal coupling value
2
for J(P,H) at 11.2 Hz. In contrast to H4ax, the equatorial pro-
ton, H4eq, couples only weakly to the methinic proton H3,
3J(H3,H4eq) = 4.5 Hz. This large difference in size of the vicinal
couplings of the H4 diastereotopic protons suggests that the
equilibrium shown in Scheme 4 lies largely on the left. The
existence of only one chelate conformation in solution is fur-
ther demonstrated by the appearance of just one set of signals
for the aromatic ortho protons at δ 7.93 (pseudo-axial) and
δ 8.19 (pseudo-equatorial). Similarly, in the 13C NMR spectrum
one set of aromatic resonances is observed for each of the
diastereotopic phenyl rings. The lower chemical shift of the
pseudo-axial ortho protons has been attributed to the shielding
effect of the metal d-electrons. Previously, Tóth and Hanson
have attributed the shielding of the pseudo-axial ortho protons
in chelating diphosphine complexes to substituent effects of the
ligand backbone.10 In our complexes, however, the ethyl substi-
tuent is pointing away from the phenyl ring on the phosphorus
thus an electronic interaction of the pseudo-axial ortho protons,
which point directly above the coordination plane, with the
metal d-electrons seems more likely.
Experimental
Materials and methods
All manipulations were performed using standard Schlenk
techniques under an argon atmosphere, except where other-
wise noted. All metal complexes were prepared under an
inert atmosphere but after their formation they are air-stable,
with the exception of complex 8, and thus manipulated under
aerobic conditions. All other reagents were used as received.
Petroleum ether had a bp range of 40–60 ЊC. Solvents were
The corresponding palladium dimer 2 reveals an analogous
1
pattern to 1 in its H NMR spectrum. The vicinal couplings
D a l t o n T r a n s . , 2 0 0 3 , 1 1 3 3 – 1 1 4 2
1139

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purified by standard literature methods.25 Microanalyses were
obtained within the department using a Perkin-Elmer 2400
CHN elemental analyser and electronic spectra in dichloro-
methane solution using a Perkin-Elmer Lambda 20. NMR
spectra were obtained on Bruker Avance AMX 400 or
JEOL Eclipse 300 sprectrometers and referenced to external
TMS; J values are in Hz. The nomeclature adopted for assign-
ment of 1H and 13C resonances is shown in Fig. 1. Mass spectra
were obtained in APCI (Atmospheric Pressure Chemical Ionis-
ation) mode unless otherwise reported on a VG Platform II
Fisons Instruments spectrometer. Racemic 2-butylenesulfide
and its S-isomer were prepared by following a literature
procedure.26 (R)-2-butyleneoxide, required for the synthesis of
(S)-2-butylenesulfide, was prepared by following a procedure
reported by Jacobsen and coworkers for the asymmetric
resolution of epoxides.9
3.10 (1H, br m, H3), 7.30–7.60 (6H, m, ArH), 7.93 (2H, t, 3JHH
≅
3JHP = 6.4, H6), 8.19 (2H, t, 3JHH ≅ 3JHP = 7.0, H10); δC (CDCl3,
100 MHz): 14.29 (1C, s, C1), 28.62 (1C, t, JCP = 8.7, C2), 41.3
(1C, m, C4), 43.53 (1C, m, C3), 127.76 (2C, t, JCP = 5.1), 127.91
(2C, t, JCP = 5.1), 128.9 (1C, dd, 1JCP = 26.2, 5JCP = 2.9, C9), 129.4
(1C, dd, 1JCP = 25.3, 5JCP = 2.9, C5), 130.05 (1C, s), 130.17 (1C,
s), 132.25 (2C, t, JCP = 4.9, C6), 132.44 (2C, t, JCP = 5.3, C10); δP
(CDCl3, 121 MHz): 37.2; m/z 734 (Mϩ, 1%).
[Pd(L1)Cl]2 2
Method A. To a solution of Pd(PhCN)2Cl2 (0.192 g,
0.5 mmol) in CH2Cl2 (20 mL) L1H (0.138 g, 0.5 mmol) was
added. The resulted bright orange solution was left stirring
overnight; subsequently volatiles were evaporated in vacuo. The
resulting bright orange solid was washed twice with diethyl
ether (20 mL) and dried (0.187 g, 90%). The pure compound
was obtained after slow diffusion of diethyl ether into an
acetonitrile solution of 2 (Found: C, 46.03; H, 4.29. C32H36Cl2-
Pd2P2S2 requires C, 46.28; H, 4.37%); δH (CDCl3, 400 MHz):
1.05 (3H, t, 3JHH = 7.3, H1), 1.84 (1H, m, 2JHH ≅ 3JHH = 7.3, H2),
L1H
Diphenylphosphine (4.9 mL, 27.9 mmol) was syringed into
diethyl ether (30 mL) at Ϫ40 ЊC and subsequently 11.2 mL of
n-BuLi (2.5 M, 28 mmol) were added. After 30 min 2-butylene-
sulfide was added dropwise and the yellow solution was left
to reach ambient temperature and stirred further for another
30 min. Water (15 mL) was then added and the diethyl ether
layer collected, subsequently the water layer was washed with
diethyl ether (2 × 20 mL) and the ethereal extracts collected.
Evaporation of diethyl ether under vacuum afforded L1H as a
clear colourless liquid (6.84 g, 90%). The ligand was used with-
out further purification. δH (CDCl3, 400 MHz): 0.92 (3H,
2
2
2.10 (1H, m, JHH
≅
3JHH = 7.3, H2), 2.62 (1H, td, JHH
≅
3JHH = 13.8, JHP = 6.6, H4ax), 2.91 (1H, ddd, JHH = 13.8,
2
2
2JHP = 11.4, JHH = 3.8, H4eq), 3.71 (1H, br m, H3), 7.20–7.75
3
(6H, m, ArH), 7.93 (4H, m, ArH); δC (CDCl3, 100 MHz): 12.76
(1C, s, C1), 30.35 (1C, m, C2), 43.65 (1C, m), 46.29 (1C, s),
129.41 (4C, m, C11, C7), 130.0 (1C, m), 130.5 (1C, m), 131.90
(1C, s), 132.00 (1C, s), 133.63 (2C, t, JCP = 5.1, C6), 133.80 (2C,
t, JCP = 5.7, C10); δP (CDCl3, 121 MHz): 40.9.
Method B. Complex 2 may also be obtained from Pd(L1)2. To
a solution of Pd(L1)2 (0.123 g, 0.19 mmol) in toluene (10 mL),
Pd(CH3CN)2Cl2 (0.49 g, 0.19 mmol) was added. The orange
solution was stirred for 1 day at 110 ЊC. Subsequently the
volume of the toluene solution was reduced to ca. 1 mL and
diethyl ether (10 mL) was added to afford complex 2 as
an orange solid (0.12 g, 80%). This material had identical
properties to that prepared by method A.
3
2
t, JHH = 7.3, H1), 1.53 (1H, m, JHH = 6.9, H2), 1.80 (2H, m,
2JHH = 6.9, H2, SH), 2.27 (1H, dd, 2JHH = 6.3, 2JHP = 13.8, H4),
2.39 (1H, dd, 2JHH = 6.3, 2JHP = 13.0, H4), 2.69 (1H, br m, H3),
7.26 (6H, m, ArH), 7.35 (4H, m, ArH); δC (CDCl3, 100
MHz): 10.27 (1C, s, C1), 31.42 (1C, d, 3JCP = 8.2, C2), 38.11 (1C,
d, 1JCP = 13.3, C4), 38.91 (1C, d, 2JCP = 16.6, C3), 127.47 (2C, d,
3
3JCP = 4.8, C7), 127.53 (2C, d, JCP = 4.9, C11), 127.60 (1C, s),
2
127.85 (1C, s), 131.57 (2C, d, JCP = 18.6, C6), 131.94 (2C, d,
2JCP = 19.3, C10), 136.90 (1C, d, 1JCP = 13.2, C9), 137.29 (1C, d,
1JCP = 12.8, C5); δP (CDCl3, 121 MHz): Ϫ19.4.
Ni(L1)2 3
Ligand L1H (0.274 g, 1 mmol) was added to a slurry of
Ni(acac)2 (0.128 g, 0.5 mmol) in toluene (15 mL). The resulting
green mixture was stirred overnight at room temperature, after
which the solvent was reduced to ca. 4 mL volume. Petroleum
ether was subsequently added to complete precipitation of 3 as
a green solid (0.26 g, 86%). The complex was further purified by
crystallisation from CH2Cl2–petroleum ether (Found: C, 63.29;
H, 5.94. C32H36S2P2Ni requires C, 63.49; H, 5.99%); λmax/nm
(CH2Cl2) 590.7 (ε/dm3 molϪ1 cmϪ1 95). rac-isomer: δH (CDCl3,
400 MHz): 0.79 (3H, m, H1), 1.44 (1H, m, H2), 1.59 (1H, m,
H2), 2.34 (1H, br m, H4ax), 2.56 (1H, br m, H3), 2.76 (1H,
m, H4eq), 7.20–7.50 (6H, m, ArH), 7.58 (2H, m, H10), 7.93 (2H,
m, H6); δC (CDCl3, 100 MHz): 15.27 (1C, s, C1), 34.35 (1C, t,
L1Me
L1H (0.69 g, 2.5 mmol) was dissolved in thf (20 mL) and
subsequently 1 mL of BuLi (2.5 M, 2.5 mmol) was syringed
into the flask. After 30 min MeI (0.16 mL, 2.5 mmol) was
introduced and the reaction was left to stir for another hour.
Similar workup as for L1H followed to yield L1Me (0.5 g, 70%).
The ligand was used without further purification. δH (CDCl3,
300 MHz): 1.03 (3H, t, 3JHH = 7.3, H1), 1.72 (1H, m, 3JHH = 7.3,
H2), 1.89 (1H, m, 3JHH = 7.3, H2), 2.00 (3H, s, SMe), 2.30–2.65
(3H, overlapping m, H3 and H4), 7.34 (6H, m, ArH), 7.50 (4H,
m, ArH); δP (CDCl3, 121 MHz): Ϫ20.3.
JCP = 6.8, C2), 44.92 (1C, t, JCP = 13.7, C3), 45.27 (1C, t, JCP
=
18.3, C4), 129.77 (2C, m), 130.04 (2C, m), 131.67 (1C, s), 132.10
(1C, s), 134.29 (2C, t, JCP = 5.7, C6), 135.49 (2C, t, JCP = 5.9,
C10); δP (CDCl3, 121 MHz): 54.2; meso-isomer: δH (CDCl3, 400
MHz): 0.79 (3H, m, H1), 1.66 (1H, m, H2), 2.16 (1H, m, H4ax),
2.43 (1H, br m, H3), 7.20–7.50 (6H, m, ArH), 7.43 (2H, m, H10),
8.0 (2H, m, H6); δC (CDCl3, 100 MHz): 15.53 (1C, s, C1), 33.83
(1C, t, JCP = 7.0, C2), 43.91 (1C, t, JCP = 13.6, C3), 44.27 (1C, t,
JCP = 18.5, C4), 129.77 (2C, m), 130.04 (2C, m), 131.55 (1C, s),
132.23 (1C, s), 133.85 (2C, t, JCP = 5.5, C6), 135.89 (2C, t,
1JCP = 6.1, C10); δP (CDCl3, 121 MHz): 53.1.
[Ni(L1)Cl]2 1
To a suspension of anhydrous NiCl2 (0.065 g, 0.5 mmol)
in CH2Cl2 (10 mL) L1H (0.137 g, 0.5 mmol) was added. The
yellow slurry within a few minutes turned lime green and
subsequently changed into a deep maroon solution. After stir-
ring the solution overnight at room temperature volatiles were
evaporated in vacuo. The resulting red solid was washed twice
with diethyl ether (20 mL) and dried (0.142 g, 77%). The sample
was further purified by the slow diffusion of diethyl ether in a
CH2Cl2 or thf solution of the complex, which afforded deep red
coloured crystals (Found: C, 52.38; H, 5.18. C32H36Cl2Ni2P2S2
requires C, 52.29; H, 4.94%); λmax/nm (CH2Cl2): 495 (ε/dm3
molϪ1 cmϪ1 3010), 386.3 (sh, 3600). δH (CDCl3, 300 MHz): 0.91
Pd(L1)2ؒ1/2CH2Cl2 4
Method A. To a solution of Pd(OAc)2 (0.11 g, 0.5 mmol) in
methanol (10 mL) L1H (0.28 g, 1.0 mmol) was added. After a
few minutes a heavy orange precipitate was formed. The super-
natant solution was decanted and the remaining solid washed
3
2
(3H, t, JHH = 7.3, H1), 1.59 (1H, m, JHH = 6.9, H2), 1.71 (1H,
m, 2JHH = 6.9, H2), 2.30 (1H, td, 2JHH ≅ 3JHH = 13.5, 2JHP = 6.6,
H4ax), 2.72 (1H, ddd, 2JHH = 13.5, 3JHH = 4.5, 2JHP = 11.2, H4eq),
D a l t o n T r a n s . , 2 0 0 3 , 1 1 3 3 – 1 1 4 2
1140

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with diethyl ether (2 × 10 mL) and dried in vacuo (0.29 g, 90%).
Good quality crystals were obtained from CH2Cl2–petroleum
ether (Found: C, 56.70; H, 5.39. C32.5H37ClS2P2Pd requires C,
56.16; H, 5.29%). trans-rac-isomer: δH (CDCl3, 400 MHz): 0.89
(0.295 g, 87%). Crystallisation from CH2Cl2–petroleum ether
afforded good quality orange crystals (Found: C, 59.68; H,
4.82. C34H33ClP2PdS requires C, 60.27; H, 4.91%); trans-isomer:
3
δH (CDCl3, 400 MHz): 0.76 (3H, t, JHH = 7.3, H1), 1.52 (2H,
(3H, t, JHH = 7.4, H1), 1.64 (1H, m, JHH = 7.4, H2), 1.72 (1H,
m, 3JHH = 7.4, H2), 2.32 (1H, td, 2JHH ≅ 3JHP = 12.4, 3JHH = 3.0,
H4), 2.73 (1H, br m, H3), 2.89 (1H, m, H4), 7.35 (6H, m, ArH),
7.56 (2H, m, ArH), 7.87 (2H, m, ArH); δC (CDCl3, 100 MHz):
14.61 (1C, s, C1), 32.70 (1C, t, JCP = 10.3, C2), 43.28 (1C, t,
JCP = 9.8, C3), 43.68 (1C, t, JCP = 17.5, C4), 128.90 (2C, t,
JCP = 4.9, C7), 129.06 (2C, t, JCP = 5.1, C11), 130.78 (1C, s),
131.23 (1C, s), 132.73 (2C, t, JCP = 6.2, C6), 134.64 (2C, t,
JCP = 7.1, C10); δP (CDCl3, 121 MHz): 48.6; trans-meso-isomer:
δH (CDCl3, 400 MHz): 2.46 (1H, m, H4), 7.64 (2H, m, ArH),
m, JHH = 7.3, H2), 2.44 (1H, ddd, JHH = 13.1, JHH = 11.6,
3
3
3
2
3
2JHP = 6.9, H4ax), 2.69 (1H, br m, H3), 2.84 (1H, ddd,
2JHH = 13.1, JHP = 11.5, JHH = 3.5, H4eq), 7.1–7.5 (17H, m,
ArH), 7.6–7.8 (6H, m, ArH), 7.8–8.0 (2H, m, ArH); δC (CDCl3,
100 MHz): 14.18 (1C, s, C1), 31.89 (1C, m, C3), 44.34 (1C, s, C2),
44.70 (1C, m, C4), 128.47 (6C, d, JCP = 10.1, PPh3), 128.84 (2C,
d, JCP = 10.5, C7), 129.17 (2C, d, JCP = 10.5, C11), 130.80 (3C, d,
JCP = 2.3, PPh3), 131.11 (1C, d, JCP = 1.8, C8), 131.61 (1C,
d, JCP = 1.8, C12), 133.47 (2C, d, JCP = 11.0, C6), 134.54 (2C, d,
JCP = 12.0, C10), 135.34 (6C, d, JCP = 11.4, PPh3); δP (CDCl3, 121
2
3
1
2
2
7.81 (2H, m, ArH); all other H resonances coincide with that
MHz): 50.3 (d, JPP = 460), 24.0 (d, JPP = 460); cis-isomer:
δP (CDCl3, 121 MHz): 57.5 (2JPP = 13.4), 23.0 (2JPP = 13.4);
m/z 678 (MHϩ, 5%), 641 (MϪCl, 1).
of the trans-rac-isomer; δP (CDCl3, 121 MHz): 51.1, cis-rac-
isomer: δH (CDCl3, 400 MHz): 2.46 (1H, m, H4), 6.84 (2H, m,
ArH), 6.96 (2H, m, ArH), 7.11 (1H, m, ArH), 7.19 (2H, m,
ArH), 7.46 (2H, m, ArH); all other 1H resonances coincide with
that of the trans-rac-isomer; δP (CDCl3, 121 MHz): 44.5; m/z
652 (Mϩ, 100%).
Method B. Complex 4 was also obtained by the following
procedure: Pd(PPh3)4 (0.30 g, 0.26 mmol) was dissolved in tolu-
ene (30 mL), subsequently L1H (0.14 g, 0.52 mmol) was added
and the resulting red solution was stirred overnight. Then the
volume was reduced to ca. 5mL and petroleum ether (20 mL)
was added to complete precipitation of 4 (0.16 g, 92%). The
compound isolated had identical spectroscopic properties with
that prepared by method A.
Method B. Complex 6 may also be obtained from dimer 2
and PPh3 according to the following procedure: [Pd(L1)Cl]2 (22
mg, 0.027 mmol) and triphenylphosphine (0.014 g, 0.054 mmol)
were dissolved in CH2Cl2 (10 mL). The orange solution formed
was stirred for two hours at room temperature. The 31P{1H}
NMR spectrum of a sample taken from the reaction solution
showed that reaction was complete. An orange solid (34 mg,
95%) was obtained after standard workup procedures that had
identical spectroscopic properties with the compound obtained
by method A.
Pd(L1)(PBu3)Cl 7
Pt(L1)2 5
The tributulphosphine analogue was obtained by following
the same protocols described in methods A and B for complex
6, typical yields were 79–85% (Found: C, 54.68; H, 7.32.
C28H45ClP2PdS requires C, 54.46; H, 7.34%); trans-isomer:
To a suspension of PtCl2 (0.133 g, 0.5 mmol) in 20 mL of
acetonitrile L1H (0.275 g, 1.0 mmol) was added at 50 ЊC.
Immediately a pale yellow solution formed that was stirred
overnight at room temperature. After reducing the solution to
ca. 8 mL in volume and placing it in the fridge for 1 day pale
yellow crystals were obtained. These were later identified as the
trans isomer of 5 containing ca. 5% of the cis-isomer. The cis
isomer crystallises preferentially from a mixture of CH2Cl2 and
petroleum ether. Yield 0.32 g (86%) (Found: C, 51.55; H, 4.74.
C32H36S2P2Pt requires C, 51.81; H, 4.89%). trans-rac-isomer:
3
δH (CDCl3, 400 MHz): 0.84 (9H, t, JHH = 7.3, P(CH2)3CH3);
3
3
0.90 (3H, t, JHH = 7.3, H1), 1.36 (6H, m, JHH = 7.3, P(CH2)3-
CH3), 1.48 (6H, m, P(CH2)3CH3), 1.61 (2H, m, H2), 1.81 (6H,
m, P(CH2)3CH3), 2.18 (1H, m, H4), 2.74 (2H, m, H3 and H4),
7.2–7.4 (4H, m, ArH), 7.52 (2H, m, ArH), 7.67 (2H, m, ArH),
7.84 (2H, m, ArH); δP (CDCl3, 121 MHz): 46.0 (d, 2JPP = 466),
2
12.0 (d, JPP = 466), cis-isomer: δP (CDCl3, 121 MHz): 54.2 (d,
2JPP = 11), 8.9 (d, 2JPP = 11).
δH (CDCl3, 300 MHz): 0.97 (3H, t, JHH = 7.3, H1), 1.77 (2H,
3
overlapping m, H2), 2.20 (1H, m, H3), 2.80 (2H, m, H4), 7.4 (6H,
m, ArH), 7.68 (2H, m, H6), 7.97 (2H, m, H10); δC (CDCl3, 100
MHz): 14.40 (1C, s, C1), 31.12 (1C, m, C2), 40.92 (1C, m, C3),
48.02 (1C, m, C4), 128.23 (2C, t, JCP = 4.9, C7), 128.44 (2C, t,
JCP = 5.1, C11), 130.62 (2C, s), 131.40 (2C, s), 132.32 (2C, t,
JCP = 5.2, C6), 135.05 (2C, t, JCP = 6.1, C10); δP (CDCl3, 121
MHz): 47.6 (JPtP = 2758.6). cis-rac-isomer: δH (CDCl3, 400
MHz): 0.89 (3H, t, 3JHH = 7.3, H1), 1.73 (2H, m, H2, 3JHH = 7.3,
Pt(L1)(PPh3)(H), 8
Ligand L1H (0.121 g, 0.44 mmol) was added to a slurry of
Pt(PPh3)4 (0.543 g, 0.44 mmol) in benzene (15 mL). The result-
ing pale yellow solution was stirred overnight at room temper-
ature, after which the solvent was evaporated to afford a pale
yellow oil. trans-isomer: δH (CDCl3, 400 MHz): Ϫ6.70 (1H, br s,
1JPtH = 950, PtH), 1.05 (3H, t, 3JHH = 7.3, H1), 1.95 (2H, br, H2),
2.25 (1H, br, H4), 2.85 (1H, br, H3), 3.16 (1H, br, H4), 6.9–7.2
(17H, m, ArH), 7.3–7.6 (6H, m, ArH), 7.87 (2H, m, ArH);
2
3
2
3JHH = 2.4), 2.44 (1H, td, JHH ≅ JHH = 12.1, JHP = 6.8, H4ax),
3
2
3
2.51 (1H, m, JHH = 2.4, H3), 2.72 (1H, td, JHH ≅ JHP ≅ 12.1,
δP (CDCl3, 121 MHz): 54.15 (br s, JPtP = 2921.6, L1), 7.0
1
3JHH = 2.6, JPtH = 66.4, H4eq), 6.88 (2H, t, JHP ≅ JHH = 7.2,
3
3
3
H6), 6.96 (2H, t, JHH = 7.2, H7), 7.07 (1H, t, JHH = 7.2, H8),
3
3
(br, PPh3); cis-isomer: δH (CDCl3, 400 MHz): Ϫ3.4 (1H, dd,
2
J
= 192.1, 2J
= 24.2 1JHPt = 986.4, PtH); δP (CDCl3, 121
HPcis
2 1 2
7.18 (2H, t, JHH = 7.4, H11), 7.30 (1H, t, JHH = 7.4, H12), 7.53
HPtrans
3
3
(2H, t, JHP ≅ JHH = 7.4, H10); δP (CDCl3, 121 MHz): 38.2
(1JPtP = 2818.23); cis-meso-isomer: δH (CDCl3, 400 MHz): 0.83
(3H, t, 3JHH = 7.3, H1), 1.52 (2H, m, H2, 3JHH = 7.3), all other 1H
resonances coincide with that of the cis-rac-isomer; δP (CDCl3,
121 MHz): 42.3 (1JPtP = 2824.18); trans-meso-isomer: δP (CDCl3,
121 MHz): 50.5 (1JPtP = 2630); m/z 741 (Mϩ, 100%).
3
3
MHz): 25.38 (d, JPP = 10, JPtP = 3036.2), 52.26 (d, JPP = 10,
1JPtP = 1880.1).
Pd(L1Me)Cl2 9
To a solution of Pd(PhCN)2Cl2 (0.24 g, 0.62 mmol) in CH2Cl2
(20 mL) L1Me (0.18 g, 0.62 mmol) was added. The yellow solu-
tion formed was stirred for 2 h, subsequently it was condensed
to ca. 5 mL volume and diethyl ether (30 mL) was added to
complete precipitation of a bright yellow solid (0.25 g, 88%).
Crystallisation from CH2Cl2–diethyl ether afforded good qual-
ity yellow coloured crystals (Found: C, 42.23; H, 4.10. C17H21-
ClPPdS requires C, 43.84; H, 4.55%); δH (CD3CN, 400 MHz):
0.94 (3H, br, H1), 1.70 (1H, br, H2), 2.59 (1H, br, H4), 2.68 (3H,
br s, SMe), 2.84 (1H, br, H3), 2.96 (1H, br, H4), 7.3–7.7 (8H, m,
Pd(L1)(PPh3)Cl 6
Method A. Pd(PhCN)2Cl2 (0.192 g, 0.5 mmol) and L1H
(0.137 g, 0.5 mmol) were dissolved in CH2Cl2 (40 mL), next
triphenylphosphine (0.134 g, 0.5 mmol) was added and the
resulting orange solution was left to stir overnight. The solution
was condensed to ca. 5 mL volume and diethyl ether (30 mL)
was added to complete precipitation of 6 as an orange solid
D a l t o n T r a n s . , 2 0 0 3 , 1 1 3 3 – 1 1 4 2
1141

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Eur. J. Inorg. Chem., 2002, 629; (d ) E. Cerrada, L. R. Falvello,
M. B. Hursthouse, M. Laguna, A. Luquin and C. Pozo-Gonzalo,
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Organometallics, 2000, 19, 1488; (b) E. Hauptman, P. J. Fagan and
W. Marshall, Organometallics, 1999, 18, 2061.
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1997, 264, 33; (b) A. Albinati, J. Eckert, P. S. Pregosin, H. Rüegger,
R. Salzmann and C. Stössel, Organometallics, 1997, 16, 579.
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Deerfield Beach, FL, 1987, p. 391.
ArH), 8.02 (2H, m, ArH); δP (CDCl3, 121 MHz): 52.1; ES-MS:
m/z 467 (MHϩ, 100%). We were unable to record the 13C{1H}
NMR spectrum of 9 due to its poor solubility in organic
solvents.
For the preparation of metal complexes with the resolved
ligand, (S)-L1H, the same experimental procedures were
followed as for the racemic ligand, L1H.
X-Ray crystallography
Data for the complexes 1, 2, 4, 5 and 9 were collected on a
Nonius Kappa CCD area detector diffractometer located at the
window of a Nonius FR591 rotating anode X-ray generator
equipped with a molybdenum target (λ(Mo-Kα) = 0.71073 Å).
Data were corrected for absorption effects by means of com-
parison of equivalent reflections using the program SORTAV.27
Compound 4 contained two molecules in the asymmetric unit,
which showed a pseudo-symmetry centre. Refinement of the
¯
structure in the centrosymmetric space group (P1) resulted in
non-convergence of the model and a structure that contained
almost entirely ‘non positive definite’ atoms. Data for complex
6 were collected on an Enraf Nonius CAD4 diffractometer
(ω-scan mode) using monochromated Mo-Kα radiation
(λ = 0.71071 Å). Empirical absorption corrections were applied
by the x-scan method.28 Structures were solved and refined
using the SHELX29 suite of programs. Molecular structures
were drawn using ORTEP-III30 Non-hydrogen atoms were
refined anisotropically with the exception of the oxygen atom in
the water molecule of structure 1 which was isotropically
refined. Hydrogen atoms were included in calculated positions
(riding model). Pertinent data collection and refinement
parameters are collated in Table 1.
12 S. S. Choinacki, Y.-M. Hsiao, M. Y. Darensbourg and J. H.
Reibenspies, Inorg. Chem., 1993, 32, 3573.
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16 M. Kita, T. Yamamoto, K. Kaswiwabara and J. Fujita, Bull. Chem.
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17 J. Real, E. Prat, A. Polo, A. Alvarez-Larena and J. F. Piniella,
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19 A. Benefiel, D. M. Roundhill, W. C. Fultz and A. L. Rheingold,
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20 R. D. Lai and A. Shaver, Inorg. Chem., 1981, 20, 477.
21 (a) I. J. B. Lin, H. W. Chen and J. P. Fackler Jr, Inorg. Chem., 1978,
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(c) S. A. Bryan and D. M. Roundhill, Acta Crystallogr., Sect. C,
1983, 39, 184; (d ) M. Capdevila, W. Clegg, P. Gonzalez-Duarte,
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CCDC reference numbers 194251–194256.
See http://www.rsc.org/suppdata/dt/b2/b209142a/ for crystal-
lographic data in CIF or other electronic format.
Acknowledgements
A. D. thanks Synetix for funding her lectureship and Cardiff
University for partial financial support. A. D. would also like to
thank Drs I. A. Fallis and M. P. Coogan (Cardiff ) for valuable
discussions and Dr R. R. Strevens (Cardiff ) for providing the
Co(salen) complex.
22 G. K. Anderson and R. Cross, Chem. Soc. Rev., 1980, 185.
23 L-F Zhang, J. Yang, D-J. Huang and G-N. Li, Sci. China Ser. B
(Engl. Transl.), 1993, 36, 513.
24 J. Real, A. Polo and J. Duran, Inorg. Chem. Commun., 1998, 1, 457.
25 D. D. Perrin and W. F. A. Amarego, Purification of Laboratory
Chemicals, Pergamon, Oxford, 1988.
References and comments
26 H. R. Snyder, J. M. Stewart and J. B. Ziegler, J. Am. Chem. Soc.,
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1 As a representative example, see: S. Kudis and G. Helmcken,
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27 R. H. Blessing, J. Appl. Crystallogr., 1997, 30, 421–426.
28 L. J. Farrugia, WinGX program, University of Glasgow, 1997.
29 G. M. Sheldrick, SHELX97: Programs for structure solution and
refinement, University of Göttingen, Germany, 1997.
30 M. N. Burnett and C. K. Johnson, ORTEP-III: Oak Ridge Thermal
Ellipsoid Plot Program for Crystal Structure Illustrations, Report
ORNL-6895, Oak Ridge National Laboratory, Oak Ridge, TN,
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2 As a representative example, see: K. Yonehara, T. Hashizume,
K. Mori, K. Ohe and S. Uemura, Chem. Commun., 1999, 415.
3 (a) H.-S. Lee, J.-Y. Bae, D.-H. Kim, H. S. Kim, S.-J. Kim, S. Cho,
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Williams, Organometallics, 2002, 21, 770; (c) R. Romeo, L. M.
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D a l t o n T r a n s . , 2 0 0 3 , 1 1 3 3 – 1 1 4 2
1142