Syntheses and structural characterisation of the compounds [Pd(dba)L2] (where L=PBz3 and PPh2Np) and the novel dimer [Pd2(μ-dba)(μ-SO2)(PBz3) 2]1

Article abstract of DOI:10.1016/S0022-328X(98)00877-8

In this paper we report the synthesis and structural characterisation (when L=PBz₃ and PPh₂Np) of the compounds [Pd(dba)L₂] (where L, PPh₂Np 1, PPh₂An 2, PPhNp₂ 3 and PBz₃ 4; Np,

Full text of DOI:10.1016/S0022-328X(98)00877-8

Journal of Organometallic Chemistry 573 (1999) 313–322
Syntheses and structural characterisation of the compounds
[Pd(dba)L2] (where L=PBz3 and PPh2Np) and the novel dimer
[Pd2(v-dba)(v-SO2)(PBz3)2]1
Andrew D. Burrows b, Nick Choi c, Mary McPartlin c, D. Michael P. Mingos a,*,
Stephen V. Tarlton a, Ramo´n Vilar a
a Department of Chemistry, Imperial College of Science, Technology and Medicine, South Kensington, London SW7 2AY, UK
b Department of Chemistry, Uni6ersity of Bath, Cla6erton Down, Bath BA2 7AY, UK
c School of Applied Chemistry, Uni6ersity of North London, London N7 8DB, UK
Received 10 June 1998; accepted 5 July 1998
Abstract
In this paper we report the synthesis and structural characterisation (when L=PBz3 and PPh2Np) of the compounds
[Pd(dba)L2] (where L, PPh2Np 1, PPh2An 2, PPhNp2 3 and PBz3 4; Np, 1-naphthyl; An, anthracenyl; Bz, benzyl; and dba,
dibenzylideneacetone) from [Pd2(dba)3] and the corresponding phosphine. All these complexes with the exception of 4 retain their
structures in solution. The 31P-NMR spectrum of 4 is both solvent and temperature dependent. Under an SO2 atmosphere the
reaction between [Pd2(dba)3] and PBz3 gave the novel dimer [Pd2(v-dba)(v-SO2)(PBz3)2], 5, which has been structurally
characterised. In this dimer both the dba and SO2 ligands bridge the two metal centres. © 1999 Elsevier Science S.A. All rights
reserved.
Keywords: Palladium; Dibenzylideneacetone; Phosphine complexes; Sulphur dioxide complexes
initially thought. The reaction products seem to be
highly dependent on the steric and electronic properties
of the phosphine. For example, Ibers and his co-work-
ers showed that [Pd(dba)2] and [Pd2(dba)3] reacted with
an excess of triphenylphosphine to give [Pd(PPh3)4] [1].
More recent studies have shown that the reaction is
more complex and a number of species are present in
Ref. [4]. On the other hand, Herrmann and his co-
workers have shown that on reacting two equivalents of
a phosphine with [Pd(dba)2], it is possible to isolate
complexes in which both the phosphine and the dba are
retained [5]. They reported the only structurally charac-
terised example of this type of complex, i.e.
[Pd(dba)(dppe)2] (where dppe=Ph2P(CH2)2PPh2), and
31P-NMR studies of analogous compounds with other
phosphines. Similar results have been obtained by
Braunstein and co-workers when using phosphines con-
taining a keto or amido function (e.g. Ph2PCH2C(O)Ph
1. Introduction
Palladium complexes of dibenzylideneacetone (dba)
[1] have been extensively used as reagents for many
organometallic syntheses [2]. They are stable in air and
easy to prepare but remain sufficiently labile to func-
tion as convenient sources of palladium(0) fragments.
With palladium, the following complexes have been
prepared and characterised: [Pd(dba)2], [Pd(dba)3] and
[Pd2(dba)3].Solvent [3]. The substitution of dba by phos-
phines is an important synthetic route to palladium(0)–
phosphine complexes. However, the products obtained
are not always the simple [PdLn] complexes as was
* Corresponding author. Fax: +44 171 5945804; e-mail:
d.mingos@ic.ac.uk
1
Dedicated to Professor Brian Johnson on the occasion of his 60th
birthday.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00877-8

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A.D. Burrows et al. / Journal of Organometallic Chemistry 573 (1999) 313–322
and Ph2PCH2C(O)NPh2) [6]. More recently, Hartwig
has reported the formation of the complexes [PdL2]
(L=P(o-Tol)3, P{2,4-(Me)2C6H3}3, P(2-Me-4-FC6H3)3,
PBut3) when reacting [Pd(dba)2] with the corresponding
phosphine [7]. Presumably, the steric bulk of the phos-
phines is inconsistent with the simultaneous coordina-
tion of the dba molecule and results in the formation of
the homoleptic phosphine complexes.
[Pd(dba)(PCy3)2] [5]. The inequivalent phosphine envi-
ronments are a direct consequence of the in-plane coor-
dination of the dba ligand in the resulting trigonal
complex and restricted rotation about the Pd-alkene
bond:
[Pd2(dba)3].CHCl3 has also been used extensively as
starting material for the synthesis of palladium cluster
compounds [8,9]. The reactions between [Pd2(dba)3].
CHCl3 and tertiary phosphines in the presence of small
molecules such as CO or SO2 give rise to cluster
compounds whose nuclearity and geometry generally
depend on the electronic and steric properties of the
phosphine.
In this paper we report the syntheses and characteri-
sation of [Pd(dba)L2] (where L=PPh2Np, PPh2An,
PPhNp2, PBz3) from [Pd2(dba)3] and the corresponding
phosphine. The products in which the phosphines are
PPh2Np and PBz3 have been structurally characterised.
When the reaction with PBz3 was carried out in an SO2
atmosphere, the novel dimer [Pd2(v-dba)(v-SO2)-
(PBz3)2] was isolated and structurally characterised.
The formulation of the complex as [Pd(dba)(PPh2
Np)2] was confirmed by a single crystal X-ray crystallo-
graphic study. The molecular structure of this complex
is shown in Fig. 2 and selected bond lengths and angles
are summarised in Table 1.
The palladium atom is three coordinate with a trigo-
nal planar geometry, two of the donors being the
˚
phosphorus atoms (mean PdꢀP 2.348 A), and the third
site is occupied by one p-olefin of the dba ligand (mean
˚
PdꢀC 2.22 A) the second olefin group remaining unco-
ordinated. The closest approach to the metal centre at
the axial position is from a naphthalene hydrogen atom
˚
(Pd(1)···H(47) 2.87 A) suggesting a weak metal-hydro-
2. Results and discussion
gen agostic interaction.
Similar reactions were carried out using the phosphi-
nes PPh2An and PPhNp2. After 4 h, in both cases,
orange products were isolated. These were formulated
as [Pd(dba)(PPh2An)2] (2) and [Pd(dba)(PPhNp2)2] (3)
on the basis of 31P-{1H}-NMR, IR, FAB-MS and
elemental analyses. The 31P-{1H}-NMR spectra of both
products showed the same pattern observed for
[Pd(dba)(PPh2Np)2]: two doublets in a 1:1 ratio. The
2.1. Reaction of [Pd2(dba)3] with bulky aromatic
phosphines
The coordination of polyaromatic phosphines to
gold(I) and platinum(II) has been recently studied in
these laboratories [10,11]. By altering the number of
aromatic rings in closely related phosphines, it is possi-
ble to fine-tune the electronic and steric properties of
these ligands. In order to extend this study to palla-
dium(0) compounds, the polyaromatic phosphines
PPh2Np, PPh2An, PPhNp2 and PNp3 (Fig. 1) were
reacted with [Pd2(dba)3].CHCl3.
When a dichloromethane solution containing four
equivalents of PPh2Np was added to a dichloromethane
solution of [Pd2(dba)3].CHCl3, a rapid colour change to
dark orange occurred. After 4 h some of the solvent
was removed under reduced pressure and ether added.
The mixture was kept at 4°C and after a few hours
orange crystals separated. The product obtained was
formulated as [Pd(dba)(PPh2Np)2] (1) on the basis of
31P-{1H}-NMR, IR, FAB-MS and elemental analyses.
The presence of the dba was confirmed from the w(CO)
stretching mode in the IR at 1644 cm−1. In the 31P-
{1H}-NMR two doublets in a 1:1 ratio were observed
at 17.6 and 22.2 ppm. This suggested the presence of
two coupled but inequivalent phosphines in the com-
plex. Similar spectroscopic properties have been ob-
served by Herrmann and co-workers for the compound
Fig. 1. Polyaromatic phosphines used in this work.

A.D. Burrows et al. / Journal of Organometallic Chemistry 573 (1999) 313–322
315
Fig. 2. Molecular structure of 1.
chemical shifts and coupling constants for these three
compounds are summarised in Table 2. The IR spectra
of these complexes showed strong bands in the ketonic
CO region revealing the presence of dba (Table 2).
The three complexes showed similar FAB mass spec-
tral fragmentation patterns. The highest intensity peak
in each case was assigned to the fragment [Pd(PR3)2]
indicating that under FAB conditions, the dba is
rapidly lost from the complex. In Table 3 the major
peak assignments for [Pd(dba)(PNpPh2)2] are given.
Interestingly, for all three complexes, higher molecular
weight peaks were observed in the FAB mass spectra
than for M+. These were assigned to the aggregation
products [Pd2L2] and [Pd2L3] (where L=polyaromatic
phosphine).
spectrum showed only a singlet at −32.5 ppm that
corresponded to the PNp3. Presumably, the large steric
demands of this phosphine prevents it from coordinat-
ing to the palladium.
Similar results have been obtained previously for
analogous reactions with platinum compounds [11].
For the reaction between [PtCl2(COD)] or
[Pt(CH3CN)4](BF4)2 with the polyaromatic phosphines
the following reactivity trend is observed: PPh2Np\
PPh2An\PPhNp2\PNp3. In the case of the reaction
between these phosphines and [Pd2(dba)3] no large dif-
ference in reactivity was observed for PPh2Np, PPh2An
and PPhNp2. However, the lack of reactivity of PNp3
suggests that steric factors probably prevent its coordi-
nation. The Tolman cone angles for these phosphines
have been previously calculated and reported [12]. The
calculated cone angles of the polyaromatic phosphines
are much larger than that for PPh3 and increase in the
order: PPh2AnBPPh2NpBPPhNp2BPNp3.
It has been previously observed that, in some cases, if
an excess of phosphine is added to the [Pd(dba)L2]
compound, dba is displaced giving the complexes
[PdL3] or [PdL4] [1]. In order to study this possibility
for the polyaromatic phosphines, an excess of the phos-
phine was added to a solution of the compound
[Pd(dba)L2] in toluene. On monitoring the reaction by
From the results discussed above, the general reac-
tion between [Pd2(dba)3] and the polyaromatic phosphi-
nes can be summarised as follows:
[Pd2(dba)3]+4L“2[Pd(dba)L2]+dba
L=PPh2Np, PPh2An, PPhNp2
An analogous reaction was carried out using the
more sterically demanding phosphine PNp3. However,
even after 24 h no complex formation was observed in
the 31P-{1H}-NMR. Even on reflux the 31P-{1H}-NMR

316
A.D. Burrows et al. / Journal of Organometallic Chemistry 573 (1999) 313–322
Table 1
There are two independent molecules in the unit cell
which are almost identical and both have planar three
coordinate geometries if the centre of the olefinic bond
is defined as a coordination site. The structure resem-
bles that observed for 1 with bond lengths to the
palladium atom being slightly shorter (mean PdꢀP
2.325 A, mean PdꢀC 2.19 A), though the differences are
on the edge of being statistically significant. In both 1
and 4 the phosphorus and the olefin atoms are nearly
coplanar with the metal (maximum deviation −0.058
˚
Selected bond lengths (A) and angles (°) for 1
˚
Bond lengths (A)
Pd(1)–P(1)
Pd(1)–C(21)
P(1)–C(31)
P(1)–C(61)
P(2)–C(71)
C(1)–O(1)
C(1)–C(11)
C(12)–C(13)
C(22)–C(23)
2.338(6)
2.23(2)
1.873(12)
1.815(12)
1.805(12)
1.22(2)
1.51(3)
1.48(3)
1.50(2)
Pd(1)–P(2)
Pd(1)–C(22)
P(1)–C(51)
P(2)–C(41)
P(2)–C(81)
C(1)–C(21)
C(11)–C(12)
C(21)–C(22)
2.357(6)
2.21(2)
1.835(12)
1.861(11)
1.812(12)
1.45(3)
˚
˚
1.32(3)
1.44(3)
˚
˚
A for C(21) in 1, and 0.097 and 0.068 A for C(12) and
C(32), respectively in the two molecules of 4). The
closest approaches to the metal centres in 4 at the axial
positions are from the phenyl hydrogen atoms
Bond angles (°)
P(1)–Pd(1)–P(2)
C(21)–Pd(1)–P(1)
C(21)–Pd(1)–P(2)
C(31)–P(1)–Pd(1)
C(61)–P(1)–Pd(1)
C(71)–P(2)–Pd(1)
C(22)–C(21)–Pd(1)
C(21)–C(22)–Pd(1)
O(1)–C(1)–C(21)
112.6(2)
138.2(6)
109.1(6)
115.4(4)
119.8(6)
110.7(5)
70.3(12)
72.0(11)
126.0(2)
C(21)–Pd(1)–C(22)
C(22)–Pd(1)–P(1)
C(22)–Pd(1)–P(2)
C(51)–P(1)–Pd(1)
C(41)–P(2)–Pd(1)
C(81)–P(2)–Pd(1)
C(1)–C(21)–Pd(1)
C(23)–C(22)–Pd(1) 109.2(12)
O(1)–C(1)–C(11)
C(21)–C(1)–C(11)
37.7(7)
100.7(6)
146.7(6)
111.6(5)
114.3(4)
120.5(6)
98.0(12)
˚
˚
(Pd(1)···H(13a) 2.83 A, Pd(2)···H(43a) 2.72 A). In the
crystals of both 1 and 4, methanol molecules have been
found to be hydrogen bonded to the ketone oxygen
atoms of the dba ligands (O(1m)···O(1) 2.769 A in 1
and O(1m)···O(1) 2.921 A).
˚
˚
119.0(2)
115.0(2)
Even though in the solid state 4 has a trigonal planar
structure (analogous to that described for the polyaro-
matic phosphine complexes) in solution its behaviour is
more complex. The 31P-{1H}-NMR spectrum of 4 in
CH2Cl2 shows the expected AX pattern (like the NMR
spectra of 1–3). However, in toluene or benzene at r.t.,
the 31P-{1H}-NMR spectrum of this compound consists
of a broad singlet at around 9.4 and two small and
broad signals at 11.0 and 8.2 ppm, which is inconsistent
with the proposed formulation. A variable temperature
31P-{1H}-NMR study was carried out but it did not
yield any further information concerning the solution
structure. A complex process seems to be occurring in
solution. We believe that, besides a fluxional process
involving the coordinated phosphines, there may be an
equilibrium which involves the formation of dimeric
species such as [Pd2(v-dba)2(PBz3)2]. We are currently
exploring this and other species that might be responsi-
ble for the unexpected behaviour of this system in
solution.
C(12)–C(11)–C(13) 128.0(2)
C(22)–C(21)–C(1) 119.0(2)
31P{1H}-NMR during a period of 24 h no change in the
spectrum was observed, indicating that in these cases
dba is not displaced from [Pd(dba)L2] by excess L.
2.2. Reaction of [Pd2(dba)3] with PBz3
When PBz3 was reacted with [Pd2(dba)3].C6H6 in
CH2Cl2 at r.t. for 4 h, an orange product characterised
as [Pd(dba)(PBz3)2] 4, was obtained. The formulation of
this complex was confirmed by an X-ray structural
characterisation (Fig. 3, Table 4). Crystals of 4 were
grown by layering a toluene solution with methanol.
Table 2
31P-{1H}-NMR data for the compounds [Pd(dba)L2] (L=PPh2Np,
PPh2An, PPhNp2 and PBz3)
2.3. Reaction between [Pd2(dba)3] and PBz3 in the
presence of SO2
L
l (ppm)
2J(Pab) (Hz)
wCO (cm−1
)
PPh2Np
PPh2An
PPhNp2
PBz3
22.2 (d) 17.6 (d)
7.9 (d) 2.0 (d)
28.5 (d) 26.1 (d)
8.1 (d) 7.6 (d)
9.4
17.0
23.8
8.4
1644
1647
1644
1643
The reactions between [Pd2(dba)3].CHCl3 and PR3 in
the presence of SO2 have been previously reported for a
wide range of phosphines. The majority of the phosphi-
nes studied give the pentanuclear clusters [Pd5(v3-
SO2)2(v-SO2)2(L)5] where L=PPh3, PMePh2, PMe2Ph,
P(C6H4OMe-p)3, P(C6H4OMe-m)3, or AsPh3 [8]. When
L=PMe3, the tetranuclear cluster [Pd4(SO2)3(PMe3)5],
which is based on a butterfly structure, is obtained.
PCy3, which has a larger Tolman cone angle, gives
[Pd4(SO2)3(PCy3)4], which has a tetrahedral metal clus-
ter geometry [8].
Table 3
Details for the positive ion FAB mass spectrum of M=
[Pd(dba)(PPh2Np)2]
m/z
Intensity (%)
Fragment
730
418
341
214
100
10
5
[M-dba]+
[M-dba-PPh2Np]+
[M-dba-PPh2Np-Ph]+
[M-dba-PPh2Np-Ph-Np]+
A SO2-saturated toluene solution of PBz3 was added
5
to a toluene solution of [Pd2(dba)3].C6H6 and SO2 was

A.D. Burrows et al. / Journal of Organometallic Chemistry 573 (1999) 313–322
317
Fig. 3. Molecular structure of 4.
bubbled through the solution for an additional 10 min
leading to a change in colour to dark red. After re-
moval of the solvent under reduced pressure, followed
by washing with several portions of ethanol to remove
the free dba, and recrystallisation from toluene/diethyl
ether, yellow crystals were obtained. A (CD3)2CO solu-
tion of the crystals gave rise to a sharp singlet in the
31P{1H}-NMR spectrum with a chemical shift of 2.8
ppm relative to H3PO4, indicating that all the phospho-
rus atoms in the product are chemically equivalent.
In general the reaction of [Pd2(dba)3] with a phos-
phine under an atmosphere of sulfur dioxide gas results
in the formation of SO2-containing cluster compounds
which do not contain any dba coordinated to the
metals. However, in this reaction, the product, after
several washings with ethanol followed by recrystallisa-
tion, contained a peak at 1606 cm−1 in the IR spec-
trum, that corresponds to the carbonyl stretching
vibration in the dba ligand. Peaks at 1195 and 1054
cm−1 in the IR spectrum confirmed the presence of
sulfur dioxide. A high carbon content (63%) was found
in the microanalysis of the compound, also indicating
that the dba ligand was present in the product of this
reaction. On the basis of the spectroscopic and analyti-
cal data alone it was not possible to propose an unam-
biguous structure for this compound. Fortunately,
crystals of sufficiently good quality were obtained so
that a single crystal X-ray analysis could be carried out.
The molecular structure of 5 is shown in Fig. 4; selected
bond lengths and angles are given in Table 5.
The molecular structure of 5 consists of a palladium
dimer with the palladium atoms bridged by one SO2
and one dba ligand; each palladium atom is also
bonded to one tribenzylphosphine ligand. The triangu-
lar coordination geometry observed in 1 and 4 is
slightly distorted in 5 by the presence of the PdꢀPd
˚
interaction (2.885(2) A). Similar PdꢀPd bond lengths
have been reported in related SO2-bridged palladium
˚
clusters, and range from 2.7720(7) to 2.956(5) A [8]. In
5 the bridging mode adopted by the dba ligand results
from the coordination of the two olefin groups to the
two palladium atoms. The conformation of the dba in

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A.D. Burrows et al. / Journal of Organometallic Chemistry 573 (1999) 313–322
5 is clearly cis, cis while in the dimeric structure
[Pd2(dba)3].CHCl3 the dba adopts a different confor-
mation: cis, trans.
particular cluster sizes does not depend only on the
ligand cone angle and must represent a subtle com-
promise between steric and electronic effects. In this
system, PBz3 shows anomalous behaviour as a result
of these factors, affording a novel Pd(0) dimer which
It is interesting to note that the labile dba ligand
remains in the dimer, without aggregation of the
‘[Pd2(SO2)(PBz3)2]’ fragment into a higher nuclearity
cluster. The recent work of Amatore and co-workers
has established that the dba ligand is indeed not as
labile as was previously thought [13]. These findings
are consistent with the reactivity when L=PBz3 in
the system [Pd2(dba)3]+SO2+L. The [Pd5(SO2)4(L)5]
structure is adopted by a large range of phosphines
with differing sizes and electronic properties, from
PMe3 with a cone angle of 118° to PPh3 with a cone
angle of 145°. In the case of the analogous reaction
with PCy3 (cone angle 170°), the tetranuclear cluster
[Pd4(SO2)3(PCy3)4] is obtained. However PBz3, with its
smaller cone angle of 165° gives only a Pd2 species
and retains a dba ligand. Clearly the formation of
may act as
a
convenient source for the
‘[Pd2(SO2)(PBz3)2]’ fragment. We are currently study-
ing the reactivity of this dimer and some preliminary
results are summarised in Scheme 1. This will be re-
ported in full at a later time.
3. Conclusion
The reactions between [Pd2(dba)3] and series of
sterically demanding phosphines have been studied.
The products obtained have been formulated as
[Pd(dba)L2] (where L=PPh2An, PPh2Np, PPhNp2
and PBz3) and single crystal X-ray structural analyses
of [Pd(dba)(PPh2Np)2] and [Pd(dba)(PBz3)2] have
confirmed that these complexes adopt a trigonal pla-
nar structure with the dba ligand coordinated by a
simple double bond. The 31P{1H}-NMR spectra of
these compounds in CH2Cl2 solutions show a clear
AX pattern. However, this is not the case when the
31P{1H}-NMR spectrum of [Pd(dba)(PBz3)2] is studied
in benzene or toluene solution. An equilibrium in-
volving a dimeric species might be responsible for the
anomalous behaviour. When the reaction between
[Pd2(dba)3] and PBz3 was carried out under an SO2
Table 4
˚
Selected bond lengths (A) and angles (°) for 4
˚
Bond lengths (A)
Pd(1)–P(1)
Pd(1)–P(2)
Pd(1)–C(11)
Pd(1)–C(12)
P(1)–C(11a)
P(1)–C(11b)
P(1)–C(11c)
P(3)–C(31a)
P(3)–C(31b)
P(3)–C(31c)
O(1)–C(1)
C(1)–C(11)
C(1)–C(21)
C(11)–C(12)
C(12)–C(13)
C(21)–C(22)
C(22)–C(23)
2.313(8)
2.343(8)
2.22(2)
2.18(3)
1.86(3)
1.79(3)
1.78(3)
1.85(3)
1.81(3)
1.83(3)
1.32(4)
1.27(5)
1.55(4)
1.45(4)
1.35(4)
1.32(4)
1.55(3)
Pd(2)–P(3)
Pd(2)–P(4)
Pd(2)–C(31)
Pd(2)–C(32)
P(2)–C(21a)
P(2)–C(21b)
P(2)–C(21c)
P(4)–C(41a)
P(4)–C(41b)
P(4)–C(41c)
O(2)–C(2)
C(2)–C(41)
C(2)–C(31)
C(31)–C(32)
C(32)–C(33)
C(41)–C(42)
C(42)–C(43)
2.364(9)
2.328(9)
2.10(3)
2.25(3)
1.86(3)
1.85(3)
1.93(3)
1.87(3)
1.93(3)
1.81(3)
1.29(3)
1.42(4)
1.61(4)
1.38(4)
1.56(3)
1.31(5)
1.41(3)
atmosphere
the
novel
dimer
[Pd2(v-dba)(v-
SO2)(PBz3)2] was formed. This formulation has been
confirmed by a single crystal X-ray structural analy-
sis.
4. Experimental
4.1. General procedures and instrumentation
Bond angles (°)
All the reactions were routinely carried out using
standard Schlenk line techniques under an atmosphere
of pure nitrogen. The solvents used were dry and free
of oxygen. [Pd2(dba)3] · CHCl3 and [Pd2(dba)3] · C6H6
were synthesised according to previously reported
methods [1]. IR spectra were recorded in a Perkin-
Elmer 1720 IR Fourier transform spectrometer be-
tween 4000 and 250 cm−1 as KBr pellets. 31P-{1H}-
NMR spectra were recorded on a JEOL JNM-EX270
Fourier transform NMR spectrometer operating at a
frequency of 290 MHz with chemical shifts reported
relative to TMS and H3PO4, respectively. Mass spec-
tra were recorded by J. Barton at Imperial College on
a VG AutoSpec-Q as FAB using 3-NBA as matrix.
Microanalyses (C, H, N) were carried out by H.
O’Callaghan at Imperial College.
P(1)–Pd(1)–P(2)
C(11)–Pd(1)–C(12)
C(11)–Pd(1)–P(1)
C(12)–Pd(1)–P(1)
C(11)–Pd(1)–P(2)
C(12)–Pd(1)–P(2)
C(1)–C(11)–Pd(1)
C(12)–C(11)–Pd(1)
C(11)–C(12)–Pd(1)
107.2(3)
38.6(9)
P(3)–Pd(2)–P(4)
107.2(3)
36.8(11)
136.3(9)
99.8(8)
116.4(9)
152.9(7)
102.0(2)
66.0(2)
C(31)–Pd(2)–C(32)
C(31)–Pd(2)–P(4)
C(32)–Pd(2)–P(4)
C(31)–Pd(2)–P(3)
C(32)–Pd(2)–P(3)
C(2)–C(31)–Pd(2)
C(31)–C(32)–Pd(2)
C(32)–C(31)–Pd(2)
139.6(7)
101.2(7)
113.2(7)
151.0(7)
98.0(2)
69.4(14)
72.0(2)
77.0(2)
C(13)–C(12)–Pd(1) 125.0(2)
C(33)–C(32)–Pd(2) 112.0(2)
O(1)–C(1)–C(11)
O(1)–C(1)–C(21)
C(11)–C(1)–C(21)
C(1)–C(11)–C(12)
C(1)–C(21)–C(22)
135.0(3)
108.0(3)
116.0(3)
125.0(3)
121.0(3)
O(2)–C(2)–C(41)
O(2)–C(2)–C(31)
C(41)–C(2)–C(31)
C(32)–C(31)–C(2)
C(42)–C(41)–C(2)
122.0(3)
115.0(2)
123.0(2)
116.0(2)
130.0(3)
C(11)–C(12)–C(13) 132.0(3)
C(21)–C(22)–C(23) 128.0(2)
C(31)–C(32)–C(33) 116.0(2)
C(41)–C(42)–C(43) 128.0(3)

A.D. Burrows et al. / Journal of Organometallic Chemistry 573 (1999) 313–322
319
Fig. 4. Molecular structure of 5.
4.2. Preparations
tion (d8-toluene) l at 7.9 ppm (1P, d) and 2.0 ppm
2
(1P,d), J(PaPb)=17 Hz. IR w(CO) 1647 cm−1
.
4.2.1. [Pd(dba)(PPh2Np)2] 1
[Pd2(dba)3].CHCl3 (0.11 g, 0.1 mmol) was dissolved in
toluene (20 ml) and a solution of PPh2Np (0.13 g, 0.4
mmol) in toluene (20 ml) added. The reaction mixture
was stirred at r.t. for 4 h. The solvent was removed
under reduced pressure and a dark brown solid was
obtained. This solid was washed with ether giving an
orange solution from which [Pd(dba)(PPh2Np)2] was
obtained as a pure yellow-orange solid by addition of
hexane (0.099 g, 51%). Anal. Calc.: found C 75.9%, H
5.0%; C61H44OP2Pd requires: C 75.9%, H 5.0%. 31P-
{1H}-NMR: Solution (d8-toluene) l at 22.2 ppm (1P, d)
4.2.3. [Pd(dba)(PPhNp2)2] 3
The same method as for [Pd(dba)(PPh2Np)2] was
carried out using: [Pd2(dba)3].CHCl3 (0.10 g, 0.1 mmol)
and PPhNp2 (0.15 g, 0.4 mmol). [Pd(dba)(PPh2Np)2]
was obtained as a pure yellow-orange solid that precip-
itated with the addition of hexane to the ether solution
(0.09 g, 42.2%) Anal. Calc.: C 77.6%, H, 4.6%.
C69H52OP2Pd requires C 77.8%, H 4.9%. 31P-{1H}-
NMR: Solution (d8-toluene) l at 28.5 ppm (1P, d) and
2
26.1 ppm (1P,d), J(PaPb)=23.8 Hz. IR w(CO) 1644
cm−1
.
2
and 17.6 ppm (1P,d), J(PaPb)=9.4 Hz. IR w(CO) 1644
cm−1. FAB mass spectrum: see text.
4.2.4. [Pd(dba)(PBz3)2] 4
The same method as for [Pd(dba)(PPh2Np)2] was
carried out using: [Pd2(dba)3].C6H6 (0.20 g, 0.2 mmol)
and PBz3 (0.25 g, 0.81 mmol). The reaction mixture was
stirred at r.t. for 4 h. After filtration the orange solution
was reduced to 5 ml followed by the addition of a layer
of MeOH. The mixture was kept at 4°C for 2 days.
Orange crystals of [Pd(dba)(PBz3)2] were obtained (0.12
g, 61%). Some of these crystals were suitable for an
4.2.2. [Pd(dba)(PPh2An)2] 2
This compound was synthesised by the same method
as for [Pd(dba)(PPh2Np)2] using: [Pd2(dba)3].CHCl3
(0.10 g, 0.1 mmol) and PPh2An (0.15 g, 0.4 mmol). The
reaction mixture was stirred at r.t. for 4 h. The solvent
was removed under reduced pressure and a dark brown
solid was obtained. This solid was washed with ether
obtaining
an
orange
solution
from
which
X-ray analysis. Anal. Calc.: C 73.1%, H 5.6%.
[Pd(dba)(PPh2An)2] crystallised as an orange solid (0.08
g, 37%). Anal. Calc.: C 75.8%, H 4.6%; required for
C69H52OP2Pd C 77.8%, H 4.9%. 31P-{1H}-NMR: Solu-
C59H57OP2Pd.CH3OH requires C 73.4%, H 6.1%. 31P-
{1H}-NMR: Solution (CD2Cl2) l at 8.1 ppm (1P, d)
2
and 7.6 ppm (1P,d), J(PaPb)=8.4. Hz. IR w(CO) 1643

320
A.D. Burrows et al. / Journal of Organometallic Chemistry 573 (1999) 313–322
cm−1
.
FAB-MS+: m/6=949 {[M]+}, 822 {[Pd2
maining yellow powder was recrystallized from a
toluene/diethyl ether mixture and cooled slowly to
4°C (0.302 g, 89%). Some of these crystals were suit-
able for a single-crystal X-ray analysis. Anal. Calc.:
C, 63.0%; H, 5.3% (C59H56O3P2Pd2S requires: C,
63.2%; H, 5.0%). wmax/cm−1 1606 (CꢁO), 1195 (SO2),
1054 (SO2). lP ((CD3)2CO) 2.8 (s). FAB-MS+: m/6=
1120 {[M]+}, 822 {[Pd2(PBz3)2]+}, 731 {[Pd2(PBz3)
(PBz2)]+}.
(PBz3)2]+}, 731 {[Pd2(PBz3)(PBz2)]+}.
4.2.5. [Pd2(v-dba)(v-SO2)(PBz3)2] 5
PBz3 (184 mg, 0.60 mmol) was dissolved in toluene
(15 ml) and SO2 gas was bubbled through for 1 min.
This solution was then added to a solution of
[Pd2(dba)3].C6H6 (300 mg, 0.30 mmol) in toluene (25
ml), and SO2 gas bubbled through the solution for 10
min whereupon the colour of the solution had
changed from deep purple to red. The mixture was
stirred under an atmosphere of SO2 for a further 30
min to ensure completion of the reaction. The solvent
was removed under reduced pressure and the yellow-
red residue was washed with two successive 30 ml
portions of ethanol to remove the free dba. The re-
4.3. Crystallography
X-ray intensity data for compounds 1, 4 and 5
were collected on
a
Siemens P4 diffractometer
equipped with a Siemens LT2 low temperature device,
using graphite Mo–Kh radiation and a ꢀ−2q scan.
The crystal data, data collection and refinement are
summarised in Table 6. In all cases, three standard
reflections measured after every 97 reflections showed
no significant variation in intensity throughout data
collection. The data were corrected for Lorentz and
polarisation factors and absorption effects.
Table 5
˚
Selected bond lengths (A) and angles (°) for 5
˚
Bond lengths (A)
Pd(1)–Pd(2)
Pd(1)–P(1)
Pd(1)–C(11)
Pd(1)–C(12)
Pd(1)–S(1)
2.885(2)
2.325(4) Pd(2)–P(2)
2.232(13) Pd(2)–C(21)
2.334(13) Pd(2)–C(22)
2.246(4) Pd(2)–S(1)
1.458(11) S(1)–O(1)
1.84(2) P(2)–C(21A)
1.856(14) P(2)–C(21B)
1.82(2) P(2)–C(21C)
1.26(2) C(1)–C(11)
1.49(2) C(11)–C(12)
1.49(2) C(13)–C(14)
1.43(2) C(14)–C(15)
1.39(2) C(16)–C(17)
1.35(2) C(21)–C(22)
1.47(2)
2.335(4)
2.242(12)
2.35(2)
2.252(4)
1.473(10)
1.806(14)
1.838(14)
1.874(14)
1.42(2)
1.41(2)
1.38(2)
1.36(2)
1.45(2)
4.3.1. Structure solution and refinement [14]
The structures of compounds 1, 4 and 5 were
solved by direct methods which revealed nearly all the
non-hydrogen atoms and, in each case, the remaining
non-hydrogen atoms were located from subsequent
difference-Fourier syntheses. In the asymmetric unit
of 4, two molecular units were observed. In 1 and 5,
all the phenyl rings were constrained to refine as reg-
ular hexagons. In both cases, the phenyl hydrogen
atoms were placed in idealised position with displace-
ment parameters equal to 1.2 Ueq of the parent car-
bon atom of the phenyl groups. In 4, the methylene
hydrogen atoms were also placed in idealised geome-
try but their assigned displacement parameters were
equal to 1.5 Ueq of the parent carbon atom. For all
three compounds 1, 4 and 5, empirical absorption
corrections were applied to the data after initial refin-
ement with isotropic displacement parameters for all
atoms [15]. In 1, a total of 12 residual peaks, each ca.
S(1)–O(2)
P(1)–C(11A)
P(1)–C(11B)
P(1)–C(11C)
C(1)–O(11)
C(1)–C(21)
C(12)–C(13)
C(13)–C(18)
C(15)–C(16)
C(17)–C(18)
C(22)–C(23)
1.40(2)
Bond angles (°)
Pd(1)–S(1)–Pd(2)
O(2)–S(1)–Pd(1)
O(2)–S(1)–Pd(2)
P(1)–Pd(1)–Pd(2) 139.10(11) P(2)–Pd(2)–Pd(1)
S(1)–Pd(1)–Pd(2) 50.19(10) S(1)–Pd(2)–Pd(1)
C(11)–Pd(1)–Pd(2) 84.0(3)
C(12)–Pd(1)–Pd(2) 118.9(4)
C(11)–Pd(1)–S(1) 132.2(3)
79.80(12) O(2)–S(1)–O(1)
112.7(5)
117.4(4)
113.9(6)
O(1)–S(1)–Pd(1)
O(1)–S(1)–Pd(2)
116.9(4)
112.1(5)
140.25(11)
50.01(9)
83.7(4)
113.4(3)
133.5(4)
91.21(14)
159.4(4)
135.3(4)
101.8(4)
35.4(5)
C(21)–Pd(2)–Pd(1)
C(22)–Pd(2)–Pd(1)
C(21)–Pd(2)–S(1)
1 e A−3, in a planar disposition, were assigned as a
˚
severely disordered benzene ring, one of the solvent
molecules used in the reaction, this disorder accounts
for the poor diffraction by the crystal. In all cases, all
non-hydrogen atoms were assigned anisotropic dis-
placement parameters in the final cycles of full-matrix
least-squares refinement, based on F2.
S(1)–Pd(1)–P(1)
S(1)–Pd(1)–C(12) 168.0(4)
C(11)–Pd(1)–P(1) 134.1(3)
93.64(14) S(1)–Pd(2)–P(2)
S(1)–Pd(2)–C(22)
C(21)–Pd(2)–P(2)
P(2)–Pd(2)–C(22)
C(21)–Pd(2)–C(22)
C(22)–C(21)–Pd(2)
C(1)–C(21)–Pd(2)
C(21)–C(22)–Pd(2)
P(1)–Pd(1)–C(12)
98.3(3)
C(11)–Pd(1)–C(12) 35.9(5)
C(12)–C(11)–Pd(1) 76.0(8)
C(1)–C(11)–Pd(1) 89.8(9)
C(11)–C(12)–Pd(1) 68.1(7)
76.6(8)
96.1(8)
67.9(8)
C(23)–C(22)–Pd(2) 121.9(10) C(13)–C(12)–Pd(1)
C(11)–C(1)–C(21) 113.6(14) O(11)–C(1)–C(21)
O(11)–C(1)–C(11) 125.6(14) C(22)–C(21)–C(1)
C(12)–C(11)–C(1) 123.0(14) C(21)–C(22)–C(23)
C(11)–C(12)–C(13) 121.8(14)
115.1(9)
121(2)
125(2)
Acknowledgements
121.7(14)
We thank EPSRC for financial support and BP plc
for endowing D.M.P.M.’s chair.

A.D. Burrows et al. / Journal of Organometallic Chemistry 573 (1999) 313–322
321
Scheme 1. Preliminary results on the reactivity of 5.
Table 6
Crystal data and structure refinement for 1, 4 and 5
1
4
5
Empirical formula
Formula weight
Temperature (K)
Crystal system
C68H56O2P2Pd
1073.47
223(2)
Monoclinic
P21/c
C
60H60O2P2Pd
C59H56O3P2Pd2S
1119.84
293(2)
Monoclinic
C2/c
1962. 84
223(2)
Monoclinic
Cc
Space group
Unit cell dimension
˚
a (A)
9.704(3)
24.360(6)
23.978(9)
20.115(4)
11.652(2)
42.481(6)
40.256(8)
16.992(3)
14.896(3)
˚
b (A)
˚
c (A)
i (°)
V (A )
94.19(4)
5653(3)
92.080(12)
9950(3)
98.86(3)
10068(4)
3
˚
Z
4
8
8
Dcalc (g cm−3
)
1.261
0.429
2224
0.20×0.38×0.40
1.19–19
1.310
0.480
4096
0.30×0.38×0.40
2.02–25.00
1.478
0.865
4576
0.04×0.35×0.46
1.30–25.00
v(Mo–Kh) (mm−1
F(000)
)
Crystal size (mm−1
q-range (°)
)
Limiting hkl
−1 to 11, −1 to 28, −28 to 28
12 796
4538 [Rint=0.1457]
3719/132/531
−1 to 23, −1 to 13, −50 to 50
10 594
9550 [Rint=0.1227]
9525/44/979
−47 to 47, 0 to 20, 0 to 17
10 295
8848 [Rint=0.1130]
8847/0/604
Reflections collected
Independent reflections
Data/restraints/parameters
S on F2
1.077
1.023
1.016
Final R indices[I\2|(I)]
R indices (all data)
Largest diff. peak and hole/ e A
R1=0.0997, wR2=0.2062
R1=0.2279, wR2=0.2979
0.875 and −0.526
R1=0.0884, wR2=0.2016
R1=0.1477, wR2=0.2601
1.488 and −1.093
R1=0.0932, wR2=0.1757
R1=0.2116, wR2=0.2347
1.034 and −1.133
−3
˚
Data in common: Mo–Kh (u=0.71073); Refinement method full-matrix least-squares on F2; S=[Sw(Fo2−F2c)2/(n−p)]1/2, where n=number of
reflection and p=total number of parameters; R1=SꢀFoꢁ−ꢁFcꢀ/SꢁFoꢁ, wR2=S[w(F2o−Fc2)2]/S[w(F2o)2]1/2, w−1=[|2(Fo2)+(tP)2+(uP)] where
P=[max(F2o,0)+2(F2c)]/3 and for 1 t=0.0987 and u=0.00, for 4 t=0.0642 and u=0.00 and for 5 t=0.0584 and u=276.623.
[6] J. Andrieu, P. Braunstein, A.D. Burrows, J. Chem. Res (S)
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