The influence of steric bulk on the geometry of triarylphosphite-based palladacycles and their tricyclohexylphosphine adducts

Article abstract of DOI:10.1016/j.poly.2005.11.014

A range of complexes of the formula [PdCl₂{P(OAr) ₃}₂] have been synthesized in order to determine the effect of steric bulk on stereochemistry, one example [PdCl ₂{P(OC₆H₄-2-^tBu)₃} ₂] has been structurally characterized. Three palladacyclic complexes [{Pd(μ-Cl)(κ²-P,C-P(OC₆H₃R)(OC ₆H₄R)₂)}₂] have been synthesized (R = H, 2-ⁱPr, 2-^tBu) and two have been characterized by crystallography (R = H and ^tBu). The latter adopts the expected trans geometry while the former is cis. In this case, the driving force for the cis geometry seems to be intermolecular interactions in the crystal structure which are disrupted on substitution. We also report an unusual solvolysis reaction.

Full text of DOI:10.1016/j.poly.2005.11.014

Polyhedron 25 (2006) 1003–1010
www.elsevier.com/locate/poly
The influence of steric bulk on the geometry of triarylphosphite-based
palladacycles and their tricyclohexylphosphine adducts
a,
a
b
Robin B. Bedford *, Michael Betham , Simon J. Coles ,
b
c
´
´
´
´
Peter N. Horton , Marıa-Jose Lopez-Saez
a
Department of Inorganic and Materials Chemistry, School of Chemistry, University of Bristol, CantockÕs Close, Bristol BS8 1TS, UK
EPSRC National Crystallography Service, Department of Chemistry, University of Southampton, Highfield Road, Southampton SO17 1BJ, UK
Grupo de Quı´mica Organometa´lica, Departamento de Quı´mica Inorga´nica, Facultad de Quı´mica, Universidad de Murcia, Apdo. 4021, 30071-Murcia, Spain
b
c
Received 12 September 2005; accepted 10 November 2005
Available online 20 January 2006
Dedicated to Professor Michael Hursthouse on the occasion of his 65th birthday.
Abstract
A range of complexes of the formula [PdCl2{P(OAr)3}2] have been synthesized in order to determine the effect of steric bulk on stereo-
chemistry, one example [PdCl2{P(OC6H4-2-tBu)3}2] has been structurally characterized. Three palladacyclic complexes [{Pd(l-Cl)-(j2-P,C-
P(OC6H3R)(OC6H4R)2)}2] have been synthesized (R = H, 2-iPr, 2-tBu) and two have been characterized by crystallography (R = H and
tBu). The latter adopts the expected trans geometry while the former is cis. In this case, the driving force for the cis geometry seems to be
intermolecular interactions in the crystal structure which are disrupted on substitution. We also report an unusual solvolysis reaction.
ꢀ 2005 Elsevier Ltd. All rights reserved.
Keywords: Palladium; Phosphite; Palladacycle; Orthometallation
1. Introduction
Most of the studies we have so far performed have been
based on the bulky triarylphosphite ligand, tris(2,4-di-tert-
butylphenyl)phosphite. We were interested to see what
effect varying the bulk of the phosphite ligand would have
on the structures and reactivity of the resultant palladium
complexes. The results of this study are presented below.
Orthopalladated triarylphosphite complexes of the gen-
eral structure 1 have proved to be very active catalysts for
Suzuki, Stille and Heck coupling reactions of aryl bromides
[1,2]. While they are not particularly useful for the coupling
of aryl chlorides, mononuclear adducts with alkyl phos-
phine ligands, complexes 2, can show extremely high activ-
ity in Suzuki biaryl coupling reactions [3,4]. The complexes
2 also prove useful in the Stille coupling and amination of
aryl chlorides and have been tested in the coupling of alkyl
halides with arylboronic acids [5–7].
2. Results and discussion
2.1. Monomeric bis-phosphite adducts
The triarylphosphite ligands 3 react cleanly with half an
equivalent of bis(acetonitrile) dichloropalladium to yield
the complexes 4 (Scheme 1). Albinati et al. have previously
shown that the geometry of the bis-triphenylphosphite
adduct 4a is cis [8], while we have shown that the bulky
analogue 4b exists solely as the trans-isomer [9].
O
P(OAr)2
O
P(OAr)2
Pd PR1R2R3
Cl
Pd Cl
Rn
Rn
2
2
1
The 31P NMR spectrum of complex 4c shows a singlet at
85.2 ppm, similar to that of complex 4b (84.5 ppm). The
presence of only one peak implies that only one isomer is
*
Corresponding author.
E-mail address: r.bedford@bristol.ac.uk (R.B. Bedford).
0277-5387/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2005.11.014

1004
R.B. Bedford et al. / Polyhedron 25 (2006) 1003–1010
CH2Cl2
P(OAr)3 + [PdCl2(NCMe)2]
cis and/or trans-[PdCl2{P(OAr)3}2]
r.t., 1.5h
3a: Ar = Ph
cis/trans-4a: Ar = Ph
b: Ar = C6H3-2,4-tBu2
c: Ar = C6H4-2-tBu
d: Ar = C6H4-2-iPr
e: Ar = C6H3-3,5-tBu2
f: Ar = C6H3-3,5-OMe2
g: Ar = C6H3-3,5-Me2
trans-4b: Ar = C6H3-2,4-tBu2
trans-4c: Ar = C6H4-2-tBu
cis/trans-4d: Ar = C6H4-2-iPr
e: Ar = C6H3-3,5-tBu2
f: Ar = C6H3-3,5-OMe2
g: Ar = C6H3-3,5-Me2
Scheme 1.
present. The IR spectrum of complex 4c shows a single
m(Pd–Cl) at 382 cmÀ1 indicating that the chloride ligands
are trans to one another. This value is close to that reported
for the complex 4b [9]. The trans-geometry was confirmed by
X-ray analysis, the results of which are presented in Fig. 1.
Presumably the high steric profile of ligand 3c in complex
4c over-rides the electronic advantages associated with the
cis arrangement, in which the p-acidic triarylphosphite
ligands would be trans to the p-basic chlorides. Indeed when
the 2-tert-butyl group is replaced with the smaller 2-isopro-
pyl function to give complex 4d, then a mixture of isomers is
obtained. The 31P NMR spectrum of complex 4d shows two
singlets at 84.4 (major) and 80.5 (minor) ppm (approximate
ratio 9:1). Comparison with the 31P NMR spectroscopic
data for the complexes 4a–c suggests that the major, higher
field signal is due to the trans isomer. The IR spectrum indi-
cates that in the solid state the major isomer is the trans
2.2. Orthometallated dimeric complexes
We have previously shown that the bulky phosphite 3b
readily reacts with palladium dichloride to produce the
dimeric palladacycle 1a (Scheme 2, method A) [9]. By con-
trast, we find this method cannot be used with the much
smaller ligand, triphenylphosphite, 3a. In this case the
desired complex 1b has been synthesised previously by Albi-
nati et al. by the reaction of the pre-formed bis-phosphite
complex 4a with one equivalent of palladium dichloride in
toluene at reflux temperature (Scheme 2 method B) [8].
Tris(2-tert-butylphenyl)phosphite (3c) is sufficiently
bulky that it is not necessary to employ method B (Scheme
1) for the synthesis of the orthopalladated dimer 1c, rather
it can be prepared directly by the reaction of the ligand
with palladium dichloride (method A). Interestingly, from
a synthetic perspective, tris(2-isopropyl)phosphite (3d) rep-
resents the cross-over point between the two methods. 31P
NMR spectroscopic analysis of a crude sample of the prod-
uct mixture from the reaction performed using method A
(Scheme 2) indicates that whilst the desired dimeric product
1d is obtained, several other phosphorus containing species
are also present. However, clean 1d can be readily prepared
by employing the method B.
complex with a single m(Pd–Cl) at 375 cmÀ1
.
We were interested to see what the effect of steric bulk in
the meta-positions of triarylphosphite ligands would have
on the geometry of the resultant bis(phosphite) dichloro-
palladium complexes. To this end we synthesized the com-
plexes 4e–g. The 31P NMR spectra indicate the presence of
only one isomer in all cases with singlets observed at d
76.6, 83.5 and 79.7 ppm for 4e, f, g, respectively. In all cases
the IR spectra are indicative of cis disposition of the chloride
ligands.
The previously reported 31P NMR spectra of complexes
1a and b show them to be a mixture of cis and trans isomers
in solution [9,8]. Complex 1d is also obtained as a mixture
of cis and trans isomers as evidenced by 31P NMR spectros-
copy which shows two peaks at 122.1 and 120.3 ppm, in
close agreement with the value obtained for 1a and 1b.
By contrast, the presence of only one isomer of complex
1c in CDCl3 solution is indicated by a singlet at
121.0 ppm in the 31P NMR spectrum and by the lack of sig-
nals for a second isomer in the 1H NMR spectrum. The sin-
gle crystal X-ray structure of complex 1c was determined
and the molecule and selected data are presented in Fig. 2.
As can be seen, the molecule adopts a trans configura-
tion, in line with previously reported orthopalladated triar-
ylphosphite dimers and the related phosphinite complex 5.
The structure is grossly similar to those of complexes 1a
and 6, with little or no significant difference between the
bonds lengths about palladium [1,9]. Comparing the struc-
ture with that of the non-orthometallated complex 4c, it can
be seen that there is a slight decrease in the Pd–P bond
˚
length on orthometallation (ꢀ0.15 A) and a slight increase
Fig. 1. The single crystal X-ray structure of trans-[PdCl2{P(OC6H4-
˚
t
˚
in the Pd–Cl bond lengths (0.14 and 0.12 A for the chlorides
2- Bu)3}2] (4c). Selected bond lengths (A) and bond angles (ꢁ): Pd1–P1,
2.2895(6); Pd1–Cl1, 2.2826(5) and P1–Pd1–Cl1, 89.38(2).
trans to the carbon and phosphorus donors, respectively).

R.B. Bedford et al. / Polyhedron 25 (2006) 1003–1010
1005
Method A
P(OAr)3
(i)
3b: Ar = Ar = C6H3-2,4-tBu2
c: Ar = C6H4-2-tBu
R1
O
P(OAr)2
1a: R1 = R2 = tBu; Ar = C6H3-2,4-tBu2
b: R1 = R2 = H; Ar = Ph
Pd Cl
c: R1 = tBu; R2 = H; Ar = C6H4-2-tBu
d: R1 = iPr; R2 = H; Ar = C6H4-2-iPr
Method B
2
(ii)
R2
cis/trans-[PdCl2{P(OAr)3}2]
4a: Ar = Ph
d:Ar = C6H4-2-iPr
Scheme 2. Conditions: (i) 1 equiv. PdCl2, 2-methoxyethanol, n, 2 h and (ii) 1 equiv. PdCl2, toluene, n, 5 h.
2
t
t
˚
Fig. 2. The single crystal X-ray structure of trans-[{Pd(l-Cl)(j -P,C-P(OC6H3-2- Bu)(OC6H4-2- Bu)2)}2] (1c). Selected bond lengths (A) and bond angles
(ꢁ): Pd1–P1, 2.1425(6); Pd1–C2, 2.015(2); Pd1–Cl1, 2.4079(5); Pd1–Cl2, 2.4239(6) and P1–Pd1–C2, 80.85(6); P1–Pd1–Cl1, 172.22(2); P1–Pd1–Cl2, 95.86(2);
C2–Pd–Cl1, 96.87(6); C2–Pd–Cl2, 175.32(6); Cl1–Pd–Cl2, 86.827(19).
complex 1b shows that it adopts a cis configuration. The
results of the structural analysis are presented in Fig. 3.
The driving force for the formation of the cis isomer in
this case is revealed by investigating the dominant intermo-
lecular interactions in the crystal structure, as shown in
Fig. 4. From this it can be seen that adjacent molecules
are arranged as head-to-tail supramolecular dimers, such
that the aromatic rings are stacked in a face to face
arrangement. Moreover, these supramolecular dimers are
further ÔlockedÕ in position by an interaction of the ring
hydrogen para to the oxy moiety with the orthometallated
ring in a neighbouring molecule. These electrostatic inter-
actions involving p electrons are enabled by the lack of ste-
ric bulk around the aromatic rings. The slightly offset
disposition of the aromatic rings with respect to each other
and the centroid–centroid separations (pÁ Á Áp = 4.368 and
But
O
But
But
O
PiPr2
Pd Cl
But
But
O
P
2
O
tBu
Pd Cl
5
2
6
To the best of our knowledge, the crystal structures of
all orthopalladated triarylphosphite dimers – as well as
the related phosphinite complex 5 – indicate that, in the
solid state, the trans isomer crystallizes preferentially
[1,9,10], although a cis-aryldialkylphosphite-based pallada-
cycle has been structurally characterized [11]. Therefore, it
came as a surprise that a single crystal X-ray analysis of
˚
˚
4.443 A and C–HÁ Á Áp = 2.597 and 2.717 A) are in accor-
dance with literature values that describe the nature of this

1006
R.B. Bedford et al. / Polyhedron 25 (2006) 1003–1010
the p orbitals [13]. Due to the bidirectional configuration
of the pendant aromatic groups in the molecule the crystal
structure is composed of discrete tapes or ribbons. The
ribbons associate with those in layers above and below
˚
through a further pÁ Á Áp interaction (4.034 A).
It is easy to see that the introduction of steric bulk into
both the orthometallated and non-orthometallated aryl
residues would lead to a disruption in these intermolecular
interactions. Presumably the preferred trans configuration
obtained with bulky ligands results from an overall reduc-
tion of unfavourable steric interactions.
2.3. Phosphine adducts of phosphite-based palladacycles
We have previously shown that the reaction of tricy-
clohexylphosphine with the bulky dimeric complex 1a in
acetonitrile leads to the formation of the mononuclear
adduct 2a in which the phosphorus donors adopt a cis dis-
position (Scheme 3) [7]. By contrast, the N-heterocyclic car-
bene adducts of both the bulky complex 1a and the smaller
analogue 1b – complexes 7 – adopt a geometry in which the
carbene ligand is invariably trans to the phosphite ligand,
regardless of the bulk of the triarylphosphite [14].
Fig. 3. The single crystal X-ray structure of trans-[{Pd(l-Cl)(j2-P,C-
P(OC6H4)(OPh)2)}2] (1b). Selected bond lengths (A) and bond angles (ꢁ):
˚
Pd1–P1, 2.1499(5); Pd1–C6, 2.0105(19); Pd1–Cl1, 2.4098(5); Pd1–Cl2,
2.4099(5); Pd2–P2, 2.1516(5); Pd2–C24, 2.0096(18); Pd2–Cl1, 2.4189(5);
Pd2–Cl2, 2.4179(5) and P1–Pd1–C6, 81.47(6); P1–Pd1–Cl1, 179.331(19);
P1–Pd1–Cl2, 93.105(19); C6–Pd1–Cl1, 98.10(6); C6–Pd1–Cl2, 174.53(6);
Cl1–Pd1–Cl2, 87.326(18); P2–Pd2–C24, 81.01(6); P2–Pd2–Cl1,
178.320(18); P2–Pd2–Cl2, 94.494(19); C24–Pd2–Cl1, 97.59(6); C24–Pd2–
Cl2, 174.96(5); Cl1–Pd2–Cl2, 86.941(18).
R
O
P(OAr)2
Pd Cl
NAr
interaction [12]. If the aromatic rings were stacked directly
above each other and at a shorter separation (ca. 3.4 A) the
ArN
R
˚
two p regions would repel each other, however, when they
7a: R = tBu; Ar = Mes
b: R = tBu; Ar = C6H3-2,4-iPr
c: R = H; Ar = C6H3-2,4-iPr
are offset and slightly further apart (in the region of ca. 4.2–
˚
4.6 A) then the r electrons may interact attractively with
Fig. 4. Packing of complex 1c showing major intermolecular interactions.

R.B. Bedford et al. / Polyhedron 25 (2006) 1003–1010
1007
R1
O
P(OAr)2
R1
O
P(OAr)2
Pd PCy3
Cl
Pd Cl
2
R2
R2
2a: R1 = R2 = tBu; Ar = C6H3-2,4-tBu2
b: R1 = tBu; R2 = H; Ar = C6H4-2-tBu
c: R1 = iPr; R2 = H; Ar = C6H4-2-iPr
d: R1 = R2 = H; Ar = Ph
Scheme 3. Conditions: 3 equiv. PCy3, MeCN, r.t., 5 h.
and P(OMe)3 along with several other minor species.
Treatment of complex 4g with methanol under the same
conditions gives a number of phosphorus-containing spe-
cies as adjudged by 31P NMR spectroscopy, which shows
a range of peaks between 90 and 95 ppm only. While there
does not appear to be any peaks corresponding to complex
8, the lack of any signal for the starting complex 4g and the
chemical shift values for the products obtained,2 imply that
complete conversion of the starting material to partially
methanolysed complexes of the form [PdCl2{P(OMe)n-
(OAr)3Àn}{P(OMe)m(OAr)3Àm}] has occurred.
While we have observed a similar alcoholysis reaction
previously with a palladium–phosphinite complex [15], the
facile nature of this particular reaction appears to be ligand
specific; none of the other complexes 4a–f appear to be sus-
ceptible to methanolysis under the same conditions.
We were interested of see whether changing the bulk of
the orthometallated ligand would have any bearing on the
geometry of the tricyclohexylphosphine adducts. There-
fore, the complexes 2b–d were prepared in an analogous
fashion to 2a. In all cases the only product obtained is that
in which the two P-donors are cis as evidenced by 31P
2
NMR spectroscopy. The mutual Jpp couplings in com-
plexes 2c and 2d (ꢀ41 Hz) are identical to that reported
for complex 2a [7], suggesting that steric bulk has very little
effect on the coordination environment. By contrast com-
plex 2b shows a lower coupling of 36.45 Hz. We previously
showed that the tri-tert-butylphosphine is too bulky to pro-
duce an adduct of complex 1a [7]. Attempts to produce
such adducts with the smaller complexes 1c and 1d gave
only starting materials as adjudged by 31P NMR analysis
of the crude product mixtures. While the triphenylphosph-
ite-based analogue 1b does appear to react with PtBu3, this
leads to a complex mixture of phosphorus-containing
species.
3. Summary
In summary, we have shown that the stereochemistry of
complexes of the type [PdCl2{P(OAr)3}2] is dependent on
the size of ortho-substituents with bulky groups forcing
the complexes to adopt the electronically less preferable
trans configuration. In contrast, variation in the bulk of
the meta-groups does not appear to have any significant
influence on geometry. The bulk of the phosphite ligand
also has implications in the choice of synthetic methodol-
ogy adopted for the formation of orthopalladated dimers
and their geometry in the solid state.
2.4. An unusual solvolysis reaction
During the course of the synthetic studies we noticed
that while complex 4g can be prepared in the same manner
as complexes 4a–f, it is necessary to avoid the addition of
methanol during work-up otherwise the isolated compound
is quite obviously not the desired product. The 31P NMR
spectrum of the white powder precipitated over several
hours in this instance shows a singlet d 98.1 ppm, quite dis-
tinct from those of complexes of the general formula 4
which fall in the range 76.6–85.2 ppm. Furthermore, the
1H NMR spectrum shows no aromatic signals; rather the
only peak observed is a non-first-order multiplet at d
3.83 ppm. Elemental analysis1 is consistent with the forma-
tion of the known complex cis-[PdCl2{P(OMe)3}2] (8).
Accordingly, we synthesized a genuine sample of complex
4. Experimental
4.1. General
All reactions were performed under nitrogen using stan-
dard schlenk techniques. All solvents were distilled from
appropriate drying reagents prior to use. Ligand 3c was
prepared according to the literature method [16], while
the known ligands 3d and 3e were prepared in a similar
manner. Complexes 4a and 8 were prepared according to
the literature methods [8,17]. All other materials were
obtained commercially and used as received.
1
8 and found its H and 31P NMR spectroscopic data to
be identical with those obtained above. This implies that
either the complex 4g undergoes facile methanolysis, or
that the triarylphosphite ligands are labile and undergo
methanolysis away from the palladium centre. The 31P
NMR spectrum of a CDCl3/MeOH solution of ligand 3g
shows that partial methanolysis occurs within 20 h at room
temperature to give an approximately 4:1 mixture of 3g
2
Palladium aryldiethylphosphite complexes of the type [PdCl2{P(OEt)2-
(OAr)}2] show chemical shifts of ꢀ 90 ppm in their 31P NMR spectra. See
1
[PdCl2{P(OMe)3}2] requires C, 16.9; H, 4.25. Found: C, 16.9; H, 4.3%.
Refs. [8,11].

1008
R.B. Bedford et al. / Polyhedron 25 (2006) 1003–1010
4.2. Synthesis of P(OC6H3-3,5-OMe2)3 (3d)
76.60. IR (Nujol mull, polythene film) m(Pd–Cl): 322 and
340 cmÀ1
.
PCl3 (0.87 ml, 10 mmol) was added to a solution of 3,5-
dimethoxyphenol (4.625 g, 30 mmol) and N,N-dimethyl-p-
toluidine (0.144 ml, 1.0 mmol) in 10 ml of xylene. The mix-
ture was then heated at reflux, while N2 was passed through
to expel the HCl formed. After 2 h, the xylene was removed
under reduced pressure and the residue was kept at 180 ꢁC
overnight in vacuo to yield the product as an orange oil
that was not purified further (87% yield). Anal. Calc. for
C27H33O3P: C, 74.3; H, 7.6. Found: C, 73.7; H, 7.85%.
NMR (CDCl3): dH (300 MHz) 6.18 (s, 6H, aryl H2 and
H6); 6.06 (s, 3H, aryl H4); 3.49 (s, 18H, Me). dP
(121.5 MHz) 130.6.
4.7. cis-[PdCl2{P(OC6H4-3,5-OMe2)3}2] (4f)
Pale yellow solid (26% yield). Anal. Calc. for
C48H54Cl2O18P2Pd: C, 49.8; H, 4.7. Found: C, 48.5; H,
4.4%. NMR (CDCl3): dH (300 MHz) 6.35 (s, 12H, H2
and H6), 6.16 (s, 6H, H4), 3.59 (s, 36H, Me). dP
(121.5 MHz) 83.49 ppm. IR (Nujol mull, polythene film)
m(Pd–Cl): 315 and 339 cmÀ1
.
4.8. cis-[PdCl2{P(OC6H4-3,5-Me2)3}2] (4g)
Diethyl ether was used in place of methanol to induce
precipitation. Pale yellow solid (75% yield). NMR
(CDCl3): dH (400 MHz) 6.74 (s, 12H, H2 and H6), 6.70
(s, 6H, H4), 2.10 (s, 36H, Me). dP (121.5 MHz, CDCl3)
79.70 ppm. IR (Nujol mull, polythene film) m(Pd–Cl): 305
4.3. General method for the synthesis of the complexes
cis/trans-[PdCl2{P(OAr)3}2] (4)
A solution of [PdCl2(NCMe)2] (0.5 mmol) and the
appropriate triarylphosphite 3 (1.0 mmol) in dichlorometh-
ane (15 ml) was stirred at room temperature for 1.5 h.
Methanol (20 ml) was then added and the mixture concen-
trated under reduced pressure to induce precipitation of the
product.
and 334 cmÀ1
.
4.9. Synthesis of trans-[{Pd(l-Cl)(j2-P,C-P(OC6H3-
2-tBu)(OC6H4-2-tBu)2)}2] (1c)
4.4. trans-[PdCl2{P(OC6H4-2-tBu)3}2] (4c)
A mixture of palladium dichloride (0.0745 g, 0.42 mmol)
and ligand 3c (0.200 g, 0.42 mmol) in 2-methoxyethanol
(10 ml) was heated at reflux temperature for 2 h. The resul-
tant solution was filtered through celite, ethanol (15 ml)
was added and the solution concentrated in vacuo to give
the product as a white solid (62% yield). Anal. Calc. for
C60H78Cl2O6P2Pd2: C, 58.2; H, 6.2. Found: C, 57.6; H,
6.1%. NMR (CDCl3): dH (300 MHz) 7.47 (s, 2H, orthomet-
allated ring), 7.33 (s, 2H, orthometallated ring), 7.25 (d,
Yellow solid (72% yield). Anal. Calc. for
C60H78Cl2O6P2Pd: C, 63.5; H, 6.9. Found: C, 63.0; H,
7.1%. NMR (CDCl3): dH (300 MHz) 7.27 (d, 6H,
3
3JHH = 9 Hz), 7.22 (d, 6H, JHH = 6 Hz), 6.92 (t, 6H,
3
3JHH = 6 Hz), 6.81 (t, 6H, JHH = 9 Hz). dP (121.5 MHz)
85.20. IR (Nujol mull, polythene film): m(Pd–Cl) 382 cmÀ1
4.5. cis/trans-[PdCl2{P(OC6H4-2-iPr)3}2] (4d)
.
3
4H, free ring, JHH = 6 Hz), 7.02 (d, 4H, free ring,
3JHH = 6 Hz), 6.97–6.87 (m, 8H, free ring), 6.80 (s, 2H,
orthometallated ring), 1.32 (s, 36H; free ring), 1.07
(s, 18H; orthometallated ring). dP (121.5 MHz) 120.96.
Yellow solid (63% yield). Anal. Calc. for C54H66Cl2-
O6P2Pd: C, 61.75; H, 6.3. Found: C, 61.25; H, 6.2%. NMR
(CDCl3): dH (300 MHz) (most of the minor isomer peaks
are coincident with or obscured by the major isomer): 7.29
4.10. Synthesis of cis/trans-[{Pd(l-Cl)(j2-P,C-P(OC6H3-
2-iPr)(OC6H4-2-iPr)2)}2] (1d)
3
3
(d, 6H, JHH = 9 Hz), 7.10 (d, 6H, JHH = 9 Hz), 7.01 (t,
6H, 3JHH = 9 Hz), 6.93 (td, 6H, 3JHH = 9 Hz, 4JHH = 3 Hz),
3
3.22 (m, 6H), 1.00 (d, 36H, major, JHH = 6 Hz), 0.93 (d,
A mixture of complex 4d (0.244 g, 0.23 mmol) and
PdCl2 (0.043 g, 0.24 mmol) in toluene (10 ml) was heated
at reflux temperature for 5 h. The resultant solution was fil-
tered through celite and the solvent was removed under
reduced pressure. The residue was then recrystallised from
CH2Cl2/MeOH to give the product as a white powder (98%
yield). Anal. Calc. for C54H64Cl2O6P2Pd2: C, 56.2; H, 5.6.
Found: C, 55.35; H, 5.5%. NMR (CDCl3): dH (300 MHz)
(most of the minor isomer peaks are coincident with or
obscured by the broad major isomer peaks): 7.38 (d,
3JHH = 9 Hz), 7.2 (br s) 7.13 (br m), 7.03–6.91 (br m)
6.78–6.76 (br m), 3.31 (br m, 2H, major isomer CH(CH3)2),
3.04 (br m, 2H, minor isomer, CH(CH3)2), 1.07 (Br d,
CH(CH3)2). dP (121.5 MHz) 122.07 (major isomer),
120.29 (minor isomer).
36H, minor, 3JHH = 6 Hz). dP (121.5 MHz) 84.42 (s, major
isomer) and 80.46 (minor isomer). IR (Nujol mull, polythene
film) m(Pd–Cl): 375 (trans isomer).
4.6. cis-[PdCl2{P(OC6H4-3,5-tBu2)3}2] (4e)
Attempts to precipitate the product from dichlorometh-
ane solution by addition of methanol, ethanol, pentane,
hexane or diethyl ether proved unsuccessful in this instance
due to the high solubility of the product. Therefore, the sol-
vent was removed in vacuo and the product was not puri-
fied further.
NMR (CDCl3): dH (300 MHz) 7.06 (s, 6H, H4), 6.92 (s,
t
12H, H2 and H6), 1.06 (s, 108H, Bu). dP (121.5 MHz)

R.B. Bedford et al. / Polyhedron 25 (2006) 1003–1010
1009
4.11. General method for the synthesis of PCy3 adducts of
phosphite-based palladacycles (2)
determined). NMR (CDCl3): dH (300 MHz) 8.20 (br dd,
2 · JHH = 6 Hz), 7.30 (d, 2H, JHH = 9 Hz), 2.20 (d, 2H,
JHH = 6 Hz), 7.08–6.95 (2 · m, 4H), 6.88 (m, 1H), 6.79
(m, 1H), 3.29 (m, 3H), 2.49 (m, 4H), 1.94 (m, 6H), 1.6,
1.2, 1.05 (3 · m, 32H), 0.85 (m, 3H) and 0.67 (d,
JHH = 9 Hz). dP (121.5 MHz) 131.43 (d, phosphite,
A mixture of the appropriate complex 1 (0.1 mmol) and
PCy3 (0.3 mmol) in acetonitrile (10 ml) was stirred at room
temperature for 5 h. The resultant solution was concen-
trated in vacuo and the product was precipitated by addi-
tion of an appropriate co-solvent.
2
2JPP = 41.3 Hz), 28.08 (d, PCy3, JPP = 40.1 Hz).
4.14. [Pd(Cl){j2-P,C-P(OC6H4)(OPh)2}PCy3] (2d)
4.12. [Pd(Cl){j2-P,C-P(OC6H3-2-tBu)-
(OC6H4-2-tBu)2}PCy3] (2b)
Product precipitated as a white solid on addition of eth-
anol and cooling at À20 ꢁC overnight (60% yield). Anal.
Calc. for C36H47ClO3P2Pd: C, 59.1; H, 6.55. Found: C,
57.2; H, 6.4%. NMR (CDCl3): dH (300 MHz) d 8.42 (br
d, 1H, JHH = 6 Hz), 7.24 (m, 5H), 7.12 (m, 5H), 7.01 (m
2H), 6.72 (br s, 1H), 2.39 (br m, 3H, Cy), 1.86 (br s, 6H,
Cy), 1.65 (br s, 9H) 1.49 (br m, 6H), 1.17 (br s, 9H). dP
Product precipitated as a white solid on addition of hex-
ane (24% yield). Anal. Calc. for C48H71ClO3P2Pd: C, 64.1;
H, 7.95. Found: C, 62.9; H, 8.3%. NMR (CDCl3): dH
3
(300 MHz) 8.42 (br m, 1H), 7.81 (br d, 2H, JHH = 6 Hz),
3
7.285 (br d, 2H, JHH = 9 Hz), 6.91 (m, 6H), 2.34 (br, 3H,
2
Cy), 1.80 (br d, 9H, Cy), 1.49 (s, 18H, tBu), 1.4, 1.1 and 0.8
(121.5 MHz) 131.00 (d, phosphite, JPP = 41.3 Hz), 29.00
t
2
(3 · m, 21H, Cy), 0.86 (s, 9H, Bu). dP (121.5 MHz) 136.6
(d, PCy3, JPP = 42.5 Hz).
(d, phosphite, 2JPP = 36.5 Hz), 28.4 (d, PCy3,
2JPP = 36.5 Hz).
5. Crystallography
4.13. [Pd(Cl){j2-P,C-P(OC6H3-2-iPr)-
(OC6H4-2-iPr)2}PCy3] (2c)
Suitable single crystals were selected and data collected
on a Bruker Nonius KappaCCD Area Detector at the win-
dow of
a Bruker Nonius FR591 rotating anode
˚
This complex could not be obtained as a pure solid but
as an impure oil (yield and elemental analysis were not
(kMo Ka = 0.71073 A) driven by COLLECT [18] and DENZO
[19] software at 120 K. The structure was determined in
Table 1
Crystallographic data for complexes 1 b, 1c and 4c
Compound
1b
1c
4c
Empirical formula
Formula weight (g molÀ1
Temperature (K)
Crystal system
C
36H28Cl2O6P2Pd2
C60H76Cl2O6P2Pd2
1238.85
120(2)
C60H78Cl2O6P2Pd2
1134.46
120(2)
)
902.22
120(2)
monoclinic
P21/c
triclinic
triclinic
ꢀ
ꢀ
Space group
P1
P1
Unit cell dimensions
˚
a (A)
12.7620(10)
15.5240(15)
17.571(2)
8.5336(6)
13.3097(6)
13.5367(8)
10.0734(17)
11.1457(11)
13.869(2)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
97.513(5)
104.904(5)
92.610(6)
1467.98(15)
80.124(8)
74.007(10)
86.778(9)
1474.6(4)
94.053(5)
3
˚
Volume (A )
3472.5(6)
Z
4
1
1
Density (calculated) (Mg mÀ3
Absorption coefficient (mmÀ1
F(000)
)
)
1.726
1.327
1792
1.401
0.806
640
1.278
0.507
596
Crystal
block; colourless
0.60 · 0.25 · 0.25
3.03–27.50
blade; colourless
0.52 · 0.24 · 0.07
2.98–27.48
shard; colourless
0.19 · 0.13 · 0.07
2.93–27.48
Crystal size (mm3)
h Range for data collection (ꢁ)
Reflections collected
39834
32539
34770
Independent reflections [Rint
]
7945 [0.0274]
99.6
semi-empirical from equivalents
1.032
R1 = 0.0242, wR2 = 0.0611
R1 = 0.0319, wR2 = 0.0654
0.665 and À0.683
6701 [0.0423]
99.8
6731 [0.0559]
99.8
Completeness to h = 27.48ꢁ (%)
Absorption correction
semi-empirical from equivalents
1.047
R1 = 0.0299, wR2 = 0.0637
R1 = 0.0409, wR2 = 0.0679
0.552 and À0.637
semi-empirical from equivalents
1.040
R1 = 0.0346, wR2 = 0.0751
R1 = 0.0457, wR2 = 0.0802
0.373 and À0.698
Goodness-of-fit on F2
Final R indices [F2 > 2r(F2)]
R indices (all data)
À3
˚
Largest difference in peak and hole (e A
)

1010
R.B. Bedford et al. / Polyhedron 25 (2006) 1003–1010
SHELXS-97 [20] and refined using SHELXL-97 [21]. Crystallo-
graphic data for complexes 1b, 1c and 4c are presented in
Table 1.3
[9] R.B. Bedford, S.L. Hazelwood, M.E. Limmert, D.A. Albisson, S.M.
Draper, P.N. Scully, S.J. Coles, M.B. Hursthouse, Chem. Eur. J. 9
(2003) 3216.
[10] R.B. Bedford, S.L. Hazelwood, P.N. Horton, M.B. Hursthouse,
Dalton Trans. (2003) 4164.
[11] Sokolov and co-workers found that a palladacycle based on O-
diethoxyphosphino-(+)-estrone gives a separable mixture of stereo-
isomers. More typically the isomers of chloro-bridged phosphite-
based palladacycles are in equilibrium (see for example Refs. [8,9]).
See: V.I. Sokolov, L.A. Bulygina, O.Y. Borbulevych, O.V. Shishkin,
J. Organometal. Chem. 582 (1999) 246.
Acknowledgements
We thank the EPSRC (PDRA for M.B., Advanced Re-
search Fellowship for RBB) and the Ministerio de Edu-
´
cacion, Cultura y Deporte (MJLS) for support and
[12] M.L. Waters, Curr. Opin. Chem. Biol. 6 (2002) 736, and references
therein.
Johnson Matthey for the loan of palladium salts.
[13] C.A. Hunter, J.K.M. Sanders, J. Am. Chem. Soc. 112 (1990) 5525.
[14] R.B. Bedford, M. Betham, M.E. Blake, R.M. Frost, P.N. Horton,
References
´
´
M.B. Hursthouse, R.-M. Lopez-Nicolas, Dalton Trans. (2005) 2774.
[15] R.B. Bedford, S.L. Hazelwood, M.E. Limmert, J.M. Brown, S.
Ramdeehul, A.R. Cowley, S.J. Coles, M.B. Hursthouse, Organomet-
allics 22 (2003) 1364.
[16] P.W.N.M. Van Leeuwen, C.F. Roobeek, J. Organometal. Chem. 258
(1983) 343.
[17] S.M. Aucott, A.M.Z. Slawin, J.D. Woollins, Dalton Trans. (2000)
2559.
[18] R. Hooft, COLLECT: Data Collection Software, Nonius B.V., Delft,
The Netherlands, 1998.
[19] Z. Otwinowski, W. Minor, Methods in enzymology, in: C.W. Carter
Jr., R.M. Sweet (Eds.), Macromolecular Crystallography, Part A,
vol. 276, Academic Press, New York, 1997, pp. 307–326.
[20] G.M. Sheldrick, Acta Crystallogr., Sect. A. 46 (1990) 467.
[21] G.M. Sheldrick, University of Go¨ttingen, Germany, 1997.
[1] D.A. Albisson, R.B. Bedford, S.E. Lawrence, P.N. Scully, Chem.
Commun. (1998) 2095.
[2] D.A. Albisson, R.B. Bedford, P.N. Scully, Tetrahedron Lett. 39
(1998) 9793.
[3] R.B. Bedford, C.S.J. Cazin, S.L. Hazelwood, Angew. Chem., Int. Ed.
41 (2002) 4120.
[4] R.B. Bedford, S.L. Hazelwood, M.E. Limmert, Chem. Commun.
(2002) 2610.
[5] R.B. Bedford, C.S.J. Cazin, S.L. Hazelwood, Chem. Commun.
(2002) 2608.
[6] R.B. Bedford, M.E. Blake, Adv. Synth. Catal. 345 (2003) 1107.
[7] R.B. Bedford, M. Betham, S.J. Coles, R.M. Frost, M.B. Hursthouse,
Tetrahedron 61 (2005) 9663.
[8] A. Albinati, S. Affolter, P.S. Pregosin, Organometallics 9 (1990) 379.
3
Crystallographic data (excluding structure factors) for the structures in
this paper, has been deposited with the Cambridge Crystallographic Data
Centre as Supplementary Publication Nos. CCDC 283108–283110. Copies
of the data can be obtained, free of charge, on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (fax: +44 0 1223 336033 or
e-mail: deposit@ccdc.cam.ac.uk).