Palladium complexes of 8-(di-tert-butylphosphinooxy) quinoline

Article abstract of DOI:10.1016/j.jorganchem.2008.10.001

The preparation of the new ligand 8-(di-tert-butylphosphinooxy)quinoline (1) and the palladium derivatives [PdCl₂(1)] (2), [Pd(η³-all)(1)]⁺ [all = C₃H₅ (3a), 1-PhC₃H₄ (3b) and 1,3-Ph₂C₃H₃ (3c)] and [Pd(η²-ol)(1)] [ol = dimethyl fumarate (4a) and fumaronitrile (4b)] is reported. The cationic species 3a-3c have been isolated as BF₄^- salts. The complex 3a(BF₄) is obtained either from the reaction of 1 with [Pd(μ-Cl)(η³-C₃H₅)]₂ or from the reaction of ClP(CMe₃)₂ with [Pd(η³-C₃H₅)(8-oxyquinoline)], followed in both cases by chloride abstraction with NaBF₄. In the complexes, the ligand 1 is P,N chelated to the central metal, as shown by the X-ray structural analysis of 3a(BF₄). At 25 °C in solution, 3a(BF₄) and 3b(BF₄) undergo a fast η³-η¹-η³ dynamic process which brings about a syn-anti exchange only for the allylic protons cis to phosphorus, while for 4a and 4b a slow rotation of the olefin around its bond axis to palladium takes place. The complexes 2 and 3a(BF₄) are efficient catalyst precursors in the coupling of the phenylboronic acid with aryl bromides and chlorides.

Full text of DOI:10.1016/j.jorganchem.2008.10.001

Journal of Organometallic Chemistry 693 (2008) 3932–3938
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Palladium complexes of 8-(di-tert-butylphosphinooxy) quinoline
a
a
b
Bruno Crociani a, , Simonetta Antonaroli , Marcello Burattini , Franco Benetollo ,
*
Alberto Scrivanti c, Matteo Bertoldini c
a Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy
b ICS-CNR, Padua, Italy
c Dipartimento di Chimica, Università di Venezia, Venice, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 21 July 2008
Received in revised form 1 October 2008
Accepted 2 October 2008
Available online 8 October 2008
The preparation of the new ligand 8-(di-tert-butylphosphinooxy)quinoline (1) and the palladium deriv-
atives [PdCl2(1)] (2), [Pd(g -
3-all)(1)]+ [all = C3H5 (3a), 1-PhC3H4 (3b) and 1,3-Ph2C3H3 (3c)] and [Pd(g2
ol)(1)] [ol = dimethyl fumarate (4a) and fumaronitrile (4b)] is reported. The cationic species 3a–3c have
been isolated as BFꢀ4 salts. The complex 3a(BF4) is obtained either from the reaction of 1 with
[Pd(l-Cl)(g g
3-C3H5)]2 or from the reaction of ClP(CMe3)2 with [Pd( 3-C3H5)(8-oxyquinoline)], followed
in both cases by chloride abstraction with NaBF4. In the complexes, the ligand 1 is P,N chelated to the
Keywords:
central metal, as shown by the X-ray structural analysis of 3a(BF4). At 25 °C in solution, 3a(BF4) and
Palladium organometallic complexes
Phosphinito–quinoline ligands
Solution and solid state structure
Suzuki–Miyaura reaction
3b(BF4) undergo a fast g3
the allylic protons cis to phosphorus, while for 4a and 4b a slow rotation of the olefin around its bond
axis to palladium takes place. The complexes 2 and 3a(BF4) are efficient catalyst precursors in the cou-
pling of the phenylboronic acid with aryl bromides and chlorides.
ꢀ
g1 g3 dynamic process which brings about a syn–anti exchange only for
ꢀ
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
rically hindered phosphine [5]. These findings prompted us to
synthesize new P,N bidentate ligands which would combined both
As a new generation of exceedingly active catalysts has become
available in the last decade, the palladium- or nickel-catalyzed
coupling of aryl halides with arylboronic acids (Suzuki–Miyaura
reaction) has gained an enormous importance as synthetic tool in
organic chemistry [1]. Despite the increasing number of reports
dealing with catalytic systems able to promote various couplings
such as Heck, Stille, Suzuki–Miyaura and Sonogashira reactions
there is a continuing interest in the design of new catalysts for
these reactions. In particular, the use of P,O, P,N or P,S chelating li-
gands is a very attractive approach because during the catalytic cy-
cle the metal centre needs to house in its coordination sphere a
certain number of species which differ in their coordination ability.
The use of bidentate ligands in Suzuki-Miyaura has been recently
reviewed [2]. Accordingly, our work has been focused on the study
of the synthetic utility of palladium species containing P,N ligands.
We have recently shown that iminophosphine–palladium(0) com-
plexes are very efficient catalysts for the Suzuki–Miyaura reaction
between arylboronic acid and aryl bromides [3]. However, they
were unable to catalyzed the same reaction with aryl chlorides.
On the other hand, the coupling of aryl chlorides with arylboronic
acid, was reported to be catalyzed by palladium phosphinite com-
plexes [4] and, more efficiently, by palladium complexes with ste-
the presence of bulky substituents on the phosphorus atom and
the chelating ability towards palladium through a nitrogen-donor
moiety. Herein, we report the preparation of a ligand of this type,
namely the 8-(di-tert-butylphosphinooxy)quinoline, and of some
palladium(II) and palladium(0) complexes as possible candidates
for catalytic application in the Suzuki–Miyaura coupling.
2. Results and discussion
2.1. Preparation of the ligand and palladium complexes
The 8-(di-tert-butylphosphinooxy)quinoline 1 and the palla-
dium derivatives 2–4 have been prepared according to reactions
(1)–(5) of Scheme 1.
The ligand 1 contains a phosphinito group and, like other phos-
phinites [6], is rather unstable as it decomposes quickly even when
stored at –20 °C under N2 atmosphere. This prevented any further
purification and characterization by elemental analysis. Neverthe-
less, as shown by 1H and 31P{H1} NMR spectroscopy, the raw prod-
uct is sufficiently pure to be used as such in the reactions (2) and
(3). On the other hand, 1 is stabilized upon coordination so that
the complexes 2, 3 and 4 appear thermally stable and no decompo-
sition was observed after prolonged time at ambient temperature
both in the solid state and in solution. P,N ligands with an 8-oxy-
quinoline group have already been studied [7], but, to the best of
* Corresponding author. Tel.: +39 06 72594389; fax: +39 06 72594328.
E-mail address: crociani@stc.uniroma2.it (B. Crociani).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.10.001

B. Crociani et al. / Journal of Organometallic Chemistry 693 (2008) 3932–3938
3933
NaH
ClP(CMe3)2
(1)
N
N
O
OH
P(CMe3)2
1
N
Pd
[PdCl2(N
CMe)2]
(2)
Cl
Cl
O
P
Me3C
CMe3
2
1
+
1/2[Pd(μ-Cl)(η3-C3H3R1R2)]2
R2
N
H
NaBF4
−
O
BF4
(3)
Pd
H
P
H
Me3C
CMe3
R1
R1 = R2= H :
R1 = H; R2= Ph :
R1 = R2= Ph :
3a
3b
3c
+
1/2[Pd (μ-Cl)(η3-C3H5)]2
ClP(CMe3)2
NaBF4
H
H
N
N
H
N
H
−
O
H
O
NEt3
(4)
BF4
Pd
Pd
O
H
P
H
H
H
Me3C
CMe3
H
H
3a
NHEt2
ol
N
3a (BF4)
(5)
O
(η2-ol)
Pd
P
Me3C
CMe3
ol = dimethyl fumarate :
ol = fumaronitrile
4a
4b
:
Scheme 1.
our knowledge, this is the first example of a phosphinito–quinoline
compound.
rupture of the P–Cl bond and insertion of the phosphorus atom into
the Pd–O bond. The complexes 3a–3c are isolated as BFꢀ4 salt, and
their ionic nature is confirmed by conductivity measurements in
CH2Cl2 solution. In line with a similar reaction previously reported
The cationic complex 3a may also be prepared according to the
reaction sequence (4). In the first step, the reaction of 8-hydroxy-
quinoline with [Pd(
l-Cl)(g
3-C3H5)]2 in the presence of NEt3 (in
for cationic g
3-allylpalladium(II) complexes [8], 3a reacts with
the 1:0.5:2 molar ratio) yields the neutral product [Pd(g3
-
NHEt2 in the presence of activated olefins to give the palladium(0)
C3H5)(8-oxyquinoline)], isolated and characterized by elemental
analysis and 1H NMR spectroscopy. In the second step, upon addi-
tion of ClP(CMe3)2 (Pd/chlorophosphine 1:1 molar ratio) the com-
plex 3a is readily formed through a reaction which involves
derivatives 4a and 4b [reaction (4) of Scheme 1].
The IR spectrum of 2 in the solid state shows two m(Pd–Cl) bands
at 339 and 277 cmꢀ1, respectively, in accord with the presence of
two cis chloride ligands. As suggested by the downfield shifts of

3934
B. Crociani et al. / Journal of Organometallic Chemistry 693 (2008) 3932–3938
the 1H NMR signal of the H(2) quinoline proton and of the 31P NMR
signal upon coordination (Table 1), the 8-(di-tert-butylphosphino-
oxy)quinoline acts as a P,N-bidentate ligand in its complexes. The
chelating nature of 1 is clearly indicated by the X-ray structural
analysis of 3a(BF4) (vide infra). For 4a and 4b a planar structure
is proposed with the olefin carbons lying in the P–Pd–N coordina-
groups appear as a doublet. These spectral features can be rational-
ized by a fast g3 3 rearrangement of the allyl ligand through
ꢀ
g1
g
ꢀ
initial rupture of the Pd–Call bond trans to phosphorus [10,11],
which brings about the interconversion of the syn and anti protons
of the allylic CH2 unit and the formation of a time-averaged plane
of symmetry on the P–Pd–N coordination plane when the g3
-
tion plane, as found for [Pd(
g
2-ol)(PꢀN)] (ol = fumaronitrile,
bound allyl complex is reformed (Scheme 2).
PꢀN = iminophosphine) [9].
For 3a in CD2Cl2, such a dynamic process cannot be frozen even
at –35 °C, the lowest temperature explored. At this temperature,
however, the anti proton of the allylic CH2 group cis to phosphorus
appears as a slightly broad doublet at 2.70 ppm and the syn proton
as a slightly broad singlet at 3.97 ppm, while the CH3 protons of the
tert-butyl groups resonate as two doublets at 1.41 and 1.36 ppm,
2.2. Solution behaviour
From the coupling constant values of the allylic protons in the
1H NMR spectra (Table 1) it appears that in solution the allyl li-
gands of 3b and 3c assume a configuration with the phenyl substit-
uents in syn position [10]. For the 1-phenylallyl complex 3b, two
geometrical isomers are possible depending on the position of
the phenyl group relative to the P,N donor atoms of the ligand 1.
In CDCl3 solution, only the isomer with the phenyl group trans to
the phosphorus atom is present. The structural assignment is based
on the J(PH) value of 10.1 Hz for the allylic anti proton trans to
phosphorus [10] and on the marked shielding of the H(2), H(3)
and H(4) quinoline protons (as compared to the resonances of
the corresponding protons in 3a) caused by the aromatic ring cur-
rents of the phenyl substituent in close proximity. Consistently,
comparable shielding are observed for the 1,3-diphenylallyl com-
plex 3c, where the syn phenyl group (trans to phosphorus) is close
to the H(2), H(3) and H(4) quinoline protons.
respectively. For 3c, the g3
if it occurs, and in this case the CH3 resonances of the tert-butyl
groups are detected as two distinct doublets in the 1H NMR spec-
trum at 25 °C.
ꢀ
g1 3 rearrangement is much slower,
g
ꢀ
As far as the solution behaviour of the palladium(0) derivatives
4a and 4b is concerned, it is well known that the related complexes
[Pd(g
2-ol)(PꢀN)] (ol = activated olefin, PꢀN = P,N chelating ligand)
undergo various dynamic process, such as olefin dissociation–asso-
ciation or olefin rotation or P,N ligand site exchange through initial
breaking of the Pd–N bond [8,12]. The 1H NMR spectra of 4a and 4b
in toluene-d8 solution show a progressive broadening and loss of
fine structure for the olefin protons signals on raising the temper-
ature from 25 to 100 °C. However, no appreciable broadening is ob-
served for the P(CMe3)2 signals which remain a sharp doublet of
doublets throughout the temperature range (Fig. 1).
In the 1H NMR spectra of 3a and 3b at 25 °C, the Hsyn and Hanti
signals of the allylic CH2 terminus cis to phosphorus coalesce into a
broad singlet, while the CH3 signals of the diastereotopic tert-butyl
These spectral changes are clearly due to interconversion of
the olefin protons, and can be accounted for only by a rotation
Table 1
Selected 1H and 31P{1H} NMR data.a
Compound
Ligand 1 protons
Allyl protons
Hsyn
Olefin protons
Hb
31P resonances
H(2)
H(3)
H(4)
CH3
Hanti
Hc
1
8.95 dd
7.5–7.3d
7.8–7.6d
7.7–7.5d
8.11 dd
1.30d
J(PH) = 11.9
1.65 d
J(PH) = 16.3
1.40 d
J(PH) = 15.6
161.2 s
169.7 s
191.4 s
2
10.35 dd
9.68 dd
8.53 dd
8.55 dd
b
b
3a
5.24 dd
4.43 dd
J(HH)e = 6.5
J(PH) = 7.7
3.35 s(br)c,f
J(HH)e = 14.4
J(PH) = 9.8
3.35 s(br)c,f
5.94 ddb
3b
3c
8.55 dd
8.87 dd
6.85 dd
6.77 dd
8.27 dd
8.11 dd
1.45 d
J(PH) = 15.7
192.0 s
185.4 s
J(HH)e = 13.7
J(PH) = 10.1
3.51 (br)c,f
6.01 ddb
3.51 s(br)c,f
1.43 d
J(PH) = 15.5
J(HH)e = 12.8
J(PH) = 9.9
0.95 d
J(PH) = 15.5
5.05 dc
J(HH)e = 11.0
4a
4b
9.50 dd
9.49 dd
7.6–7.4d
7.7–7.5d
8.30 dd
8.41 dd
1.40 d
J(PH) = 14.2
3.59 dd
J(HH) = 9.9
J(PH) = 9.9
4.31 dd
J(HH) = 9.9
J(PH) = 3.0
196.4 s
195.7 s
1.24 d
J(PH) = 14.1
1.40 d
2.54 dd
3.44 dd
J(PH) = 14.4
J(HH) = 9.6
J(PH) = 9.6
J(HH) = 9.6
J(PH) = 3.4
1.38 d
J(PH) = 14.6
a
In CDCl3 at 25 °C; satisfactory integration values were obtained; coupling constants in Hz; the numbering H(2), H(3) and H(4) refers to the hydrogen atoms in position 1, 2
and 3, respectively, on the 8-quinolyl group.
trans to phosphorus.
cis to phosphorus.
Overlapping multiplets.
Coupling constant with the central allyl proton.
Coalescing signals.
b
c
d
e
f

B. Crociani et al. / Journal of Organometallic Chemistry 693 (2008) 3932–3938
3935
H
H
N
N
H
N
R
1
R
O
R
O
Pd
Pd
O
Pd
P
P
P
2
H
Me3C
Me3C
H
Me3C
Me3C
Me3C
Me3C
1
1
2
H
2
Scheme 2.
Fig. 1. 1H NMR spectra of complex 4a in toluene-d8 at different temperatures: (a) 300 K; (b) 330 K and (c) 350 K.
of the
g
2-olefin around its bond axis to the central metal. The
other dynamic processes, if they occur, would cause a progres-
sive broadening of the P(CMe3)2 signals and, eventually, their
coalescence into one doublet either by formation of a time-aver-
aged plane of symmetry on the P–Pd–N coordination plane
(olefin dissociation–association) or by interconversion of the
tert-butyl groups (P,N ligand site exchange). The lack of dissoci-
ation processes implies the presence of rather strong Pd–N and
Pd–olefin bonds in 4a and 4b.
2.3. X-ray structure of 3a(BF4)
The solid-state structure of the
g
3-allyl complex 3a(BF4) has
been determined by X-ray diffraction analysis in order to complete
the characterization of the labile ligand 1 and to gain a better in-
sight into its coordination properties. On the other hand, there
are only a few literature reports on the structure of palladium(II)
complexes with similar ligands, such as phosphinito–oxazolines
[13] and phosphinito–pyridines [14]. The molecular structure of
3a and atom labelling scheme are shown in Fig. 2.
Some selected bond lengths and angles are reported in Table 2.
The orientation around the central metal is distorted square-
planar with the allylic carbons and the P and N donor atoms
comprising the immediate coordination sphere. The bite angle P–
Pd–N of 92.8(2)° is close to the idealized value of 90° and in line
with the presence of a flexible six-membered chelate ring. The
Fig. 2. An ORTEP drawing of complex 3a(BF4) showing the atom labelling scheme
and thermal ellipsoids at 40% probability level. Hydrogen atoms and the BFꢀ4 anion
are omitted for clarity.
quinoline plane N–C(4)–C(5)–C(6)–C(7)–C(8)–C(9)–C(10)–C(11)–
C(12) makes a dihedral angle of 30.2(1)° with the P–Pd–N plane,
the oxygen atom being at a distance of 0.152(4) Å from this plane.

3936
B. Crociani et al. / Journal of Organometallic Chemistry 693 (2008) 3932–3938
Table 2
Table 3
Selected bond distances (Å) and angles (°) of 3a.
Suzuki–Miyaura couplings using complexes 2 and 3a(BF4) as the precatalysts.a
Pd–N
2.137(5)
2.111(6)
2.208(12)
1.632(4)
1.39(2)
Pd–P
Pd–C(2)
Pd–C(3)
O–C(9)
C(3)–C(2)
C(3)–C(2)0
C(1)–Pd–C(3)
C(1)–Pd–P
C(2)–Pd–P
C(3)–Pd–P
C(9)–O–P
C(1)–C(2)0ꢀC(3)
2.255(1)
2.188(11)
2.288(9)
1.392(6)
1.26(3)
Entry
Complex
ArX
ArX/Cat.
Conv.b (%)
TONc
TOFd
Pd–C(1)
Pd–C(2)0
P–O
C(1)–C(2)
C(1)–C(2)0
N–Pd–P
C(1)–Pd–N
C(2)–Pd–N
C(3)–Pd–N
O–P–Pd
1
2
3
4
5
6
7
8
2
2
2
2
4-CH3COC6H4Br
C6H5Br
4-CH3COC6H4Cl
C6H4Cl
4-CH3COC6H4Br
C6H5Br
4-CH3COC6H4Cl
C6H4Cl
100000
100000
200
100
100
100
85
100000
100000
200
50000
50000
100
200
170
85
1.36(2)
92.8(2)
1.34(2)
66.9(3)
3a(BF4)
3a(BF4)
3a(BF4)
3a(BF4)
100000
100000
200
90
90000
100000
200
45000
50000
100
100
100
100
167.1(2)
130.4(6)
100.3(3)
108.4(1)
133(2)
100.0(2)
135.4(6)
166.9(2)
129.5(3)
128(1)
200
200
100
a
Reaction conditions. Solvent: toluene (12 mL); t = 2 h; T: 110 °C; aryl halide:
4.0 mmol; phenylboronic acid: 6.0 mmol; base: K2CO3 (8.0 mmol).
By GLC with n-undecane as internal standard.
TON: mol of substrate converted/mol of catalyst.
TOF: mol of substrate converted/mol of catalyst per hour.
C(1)–C(2)–C(3)
b
c
d
The central carbon of the allyl ligand is disordered in two positions
with an occupancy factor of 0.60 for C(2) and 0.40 for C(2)0. Such
structural disorder seems to be a common feature for cationic com-
3-C3H5)(PꢀN)]+ (PꢀN = iminophosphine or
acid proceeds to completion in two hours (entry 3 of Table 3) and
also the less activated chlorobenzene is coupled with phenylbo-
ronic in high yield. Further experiments showed that also the cat-
ionic allyl complex 3a is active in promoting the Suzuki coupling of
phenylboronic acid with the same aryl halides (entries 5–8 of Table
3); not surprisingly the catalytic activity of 2 and 3a turned out to
be almost identical.
Considering that the reaction conditions were not optimized,
the catalytic potential of complexes 2 and 3a appears of particular
interest. As a matter of fact, the coupling of aryl chlorides with
boronic acids is usually carried out using 1–3 mol% of catalyst
[2,16,17] and only a small number of catalysts [16,18] are able to
activate aryl chloride substrates at loading lower than 1 mol% in
short reaction time. More detailed studies on catalytic activity of
2, 3a(BF4), 4a and 4b are currently in progress.
plexes of the type [Pd(
g
phosphino–oxazoline) [9,15], although it was not found for the
complex where PꢀN is a phosphinito–oxazoline [13a]. In both ori-
entations, the three allylic carbon atoms are bonded to palladium.
In the C(1)–C(2)0ꢀC(3) unit the C–C bond distances are of compa-
rable values [1.36(2) and 1.34(2) Å], whereas in the C(1)–C(2)–
C(3) unit the C–C bond lengths are significantly different [1.39(2)
and 1.26(3) Å]. The longer Pd–C(3) bond trans to phosphorus
[2.208(9) Å], compared to Pd–C(1) trans to nitrogen [2.111(6) Å],
reflects the greater trans influence of the P donor atom. The dihe-
dral angles between the allyl planes C(1)–C(2)–C(3), C(1)–
C(2)0ꢀC(3) and the PꢀPd–N plane are 128(2)° and 121(2)°,
respectively.
2.4. Preliminary catalytic studies
3. Conclusion
As stated in the introduction, our studies are focused on the de-
sign of new well defined palladium species to be valuably em-
ployed as precatalysts in reactions leading to C–C bond formation
such as the Suzuki–Miyaura reaction. For a preliminary assess-
ment, we have tested the catalytic activity of complexes 2 and
3a(BF4) in the coupling of phenylboronic acid with aryl bromides
and chlorides (Scheme 3).
The initial experiments were carried out with complex 2 in tol-
uene using an aryl bromide/palladium ratio of 100000:1 in the
presence of K2CO3 as the base (Table 3).
While at temperatures lower than 90 °C the reaction with
p-bromoacetophenone proceeds at modest rates, above 100 °C
the catalyst activity becomes impressive (entry 1 of Table 3) so that
a complete substrate conversion is achieved in two hours. Very
favourably, such high reaction rates are observed even in the cou-
pling of phenylboronic acid with bromobenzene which is a sub-
strate lacking an activating EWG (entry 2 of Table 3). Encouraged
by these results, we extended our investigations to the more chal-
lenging coupling of phenylboronic acid with aryl chlorides. Under
the same reaction conditions and with a substrate/catalyst ratio
of 200:1, the coupling of p-chlorocetophenone with phenylboronic
The labile 8-(di-tert-butylphosphinooxy)quinoline 1 can be sta-
bilized by coordination to a palladium centre. This allows the prep-
aration of a series of palladium complexes and the study of their
solution behaviour also at high temperatures. The P,N chelating
mode of 1 in the complexes is confirmed by an X-ray diffraction
analysis of the cationic derivative [Pd(g
3-C3H5)(1)]+ (3a). Prelimin-
ary data show that the PdCl2 adduct 2 and the allyl complex 3a are
efficient catalysts (or catalyst precursors) in the coupling of the
arylboronic acid with aryl bromides and chlorides.
4. Experimental
4.1. General procedures
The preparations were carried out under N2 atmosphere using
standard Schlenk techniques, unless otherwise stated. The sol-
vents, tetrahydrofuran, diethyl ether and toluene, were distilled
over sodium/benzophenone, dichloromethane over calcium hy-
dride, under N2 and immediately used [19]. Chlorobenzene and
HO
2 or 3a(BF4)
R
+
B
R
X
K2CO3
HO
R = H, COCH3
X = Cl, Br
Scheme 3.

B. Crociani et al. / Journal of Organometallic Chemistry 693 (2008) 3932–3938
3937
bromobenzene wer distilled before the use. 8-Hydroxyquinoline,
di-tert-butylchlorophosphine, NaH, diethylamine, dimethyl fuma-
rate, fumaronitrile, bromobenzene, 4-bromoacetophenone, 4-chlo-
roacetophenone, phenylboronic acid and anhydrous potassium
carbonate were obtained commercially and used without further
3c(BF4) (1.83 g, 90%). Anal. Calc. for C32H37BF4NOPPd: C, 56.87;
H, 5.52; N, 2.07. Found: C, 56.45; H, 5.30; N, 1.98%. IR (Nujol): m(B–
F) at 1052 cmꢀ1. Molar conductivity: 66.0 ohmꢀ1 cm2 molꢀ1 for a
1.0 ꢁ 10ꢀ3mol/l CH2Cl2 solution.
purification. The complexes [PdCl2(N„CMe)2], [Pd(
l
-Cl)(g3
3-1,3-
-
4.5. Preparation of [Pd(g
3-C3H5)(8-oxyquinoline)]
C3H5)]2, [Pd( -Cl)( and [Pd( -Cl)(g
l
g
3-1-PhC3H4)2]
l
Ph2C3H3)2] were prepared by literature methods [3c,20–22]. 1H,
31P{1H} and 13C{1H} NMR spectra were recorded on a Bruker
Avance 300 spectrometer operating at 300.13, 121.49 and
65.47 MHz and, respectively. Chemical shifts are reported in ppm
downfield from SiMe4 for 1H and 13C, and from H3PO4 as external
standard for 31P. The spectra were run at 25 °C except when noted.
IR spectra were recorded on a Perkin–Elmer 983G spectrophotom-
eter. Mass spectra were recorded on a HP 5890 series II gas chro-
matograph interfaced to a HP 5971 quadrupole mass detector.
The catalytic reactions were monitored by GLC on a 6850 Agilent
Technologies gas chromatograph.
8-Hydroxyquinoline (0.290 g, 2 mmol) was added to a solution
of [Pd( -Cl)(
3-C3H5)]2 (0.366 g, 1 mmol) and NEt3 (0.405 g,
l
g
4 mmol) in CHCl3 (20 ml). After stirring for 1 h, the solvent was
evaporated to dryness. The solid residue was washed with water
(3 ꢁ 10 ml) and dried in vacuo. Precipitation from a CHCl3/Et2O sol-
vent mixture afforded the product as a yellow microcrystalline so-
lid (0.52 g, 89%). Anal. Calc. for C12H11NOPd: C, 49.42; H, 3.80; N,
4.80. Found: C, 49.10; H, 3.63; N, 4.65%. 1H NMR (CDCl3, 25 °C):
8-oxyquinoline ligand, d = 8.57 [dd, J(HH) = 4.6 Hz, J(HH) = 1.3 Hz,
1H, H(2)], 8.24 [dd, J(HH) = 8.3 Hz, J(HH) = 1.3 Hz, 1H, H(4)], 7.48
[t, J(HH) = 7.9 Hz, 1H, H(6)], 7.34 [dd, J(HH) = 8.3 Hz, J(HH) = 4.6 Hz,
1H, H(3)], 7.10 [d, J(HH) = 7.9 Hz, 1H, H(5)], 6.97 [d, J(HH) = 7.9 Hz,
1H, H(7)]; allyl ligand, d = 5.63 [m, 1H, central proton], 4.20 [d,
J(HH) = 6.2 Hz, 1H, syn proton], 3.82 [d, J(HH) = 6.7 Hz, 1H, syn pro-
ton], 3.16 [d, J(HH) = 11.1 Hz, 1H, anti proton], 3.12 [d,
J(HH) = 11.0 Hz, 1H, anti proton].
4.2. Synthesis of ligand 1
8-Hydroxyquinoline (0.726 g, 5 mmol) was added to a suspen-
sion of NaH (0.18 g, 6 mmol, 80% in mineral oil) in THF (40 ml)
and the mixture was refluxed for 1 h. After cooling at room tem-
perature, di-tert-butylchlorophosphine (0.10 g, 5.5 mmol) was
added dropwise under stirring. The suspension was refluxed for
18 h and filtered over neutral aluminium oxide. The resulting solu-
tion was evaporated to dryness to give 1 as white solid (0.75 g, 52%
yield, based on 8-hydroxyquinoline). The product was used imme-
diately without further purification.
4.6. Reaction of [Pd(g
3-C3H5)(8-oxyquinoline)] with ClP(CMe3)2
The di-tert-butylchlorophosphine (0.092 g, 0.51 mmol) was
added to a solution of [Pd(
3-C3H5)(8-oxyquinoline)] (0.146 g,
g
0.5 mmol) in 20 ml of THF. After 4 h at room temperature, a sample
(ca. 1 ml) of the solution was evaporated to dryness and the resi-
due was dissolved in CDCl3. The 31P NMR spectrum showed the
presence of a strong singlet at 186.8 ppm and the disappearance
of the singlet of free ClP(CMe3)2 at 146.6 ppm. Upon addition of so-
lid NaBF4 (0.11 g, 1 mmol), the mixture was stirred overnight and
then worked up as described above for the preparation of the cat-
4.3. Preparation of complex 2
The freshly prepared ligand 1 (1.146 g, 3.96 mmol), dissolved in
CH2Cl2 (20 ml), was added to a solution of [PdCl2(N„CMe)2]
(0.934 g, 3.6 mmol) in 20 ml of CH2Cl2. After stirring for 0.5 h, the
resulting solution was concentrated to small volume and diluted
with diethyl ether to precipitate, the product as an orange powder
(1.38 g, 82% yield). The complex was purified by crystallization
from hot acetonitrile. Anal. Calc. for C17H24Cl2NOPPd: C, 43.75; H,
5.18; N, 3.00. Found: C, 43.86; H, 5.16; N, 2.96%. 13C{1H} NMR
(CDCl3, 25 °C): 8-oxyquinoline carbons, d = 159.5 s, 149.2 s, 141.3
s, 133.1 s, 130.9 s, 128.1 s, 124.9 s, 122.4 s, 120.8 s; tert-butyl car-
bons, d = 44.5 d [J(PC) = 22 Hz], 28.8 s.
ionic
g
3-allyl complexes, yielding 3a(BF4) (0.17 g, 65%).
4.7. Preparation of complexes 4a and 4b
A moderate excess of NHEt2 (0.183 g, 2.5 mmol) was added to a
solution of 3a(BF4) (0.262 g, 0.5 mmol) and the appropriate olefin
(0.6 mmol) in CH2Cl2 (50 ml). After standing for 1 h at room tem-
perature, the solvent was evaporated to dryness. The solid residue
was repeatedly washed with water and dried in vacuo. The prod-
ucts were crystallized from a CH2Cl2 solution upon slow addition
of a n-hexane/Et2O mixture (1:1 v/v).
4.4. Preparation of complexes 3a(BF4), 3b(BF4) and 3c(BF4)
4a (0.19 g, 70%). Anal. Calc. for C23H32NO5PPd: C, 51.17; H, 5.97;
The complexes were prepared from the reaction of [Pd(
l
-
N, 2.60. Found: C, 51.16, H, 6.10; N, 2.50%. IR (Nujol):
1691 and 1678 cmꢀ1
4b (018 g, 76%). Anal. Calc. for C21H26N3OPPd: C, 53.23; H, 5.53;
N, 8.87. Found: C, 53.05, H, 5.41; N, 8.57%; IR (Nujol): (C„N) at
2201 cmꢀ1
m(C@O) at
Cl)(g
3-all)]2 (1.5 mmol, all = C3H5, 1-PhC3H4, 1,3-Ph2C3H3) with
.
the ligand 1 (0.897 g, 3.1 mmol) in CH2Cl2 (25 ml) followed by
addition of NaBF4 (0.66 g, 6 mmol) dissolved in 15 ml of MeOH.
After stirring for 1 h, the solvents were evaporated to dryness at re-
duced pressure. The solid residue was extracted with CH2Cl2
(20 ml) in the presence of activated charcoal. After filtration on cel-
ite, the solution was concentrated to small volume (ca. 3 ml) and
diluted with diethyl ether to precipitate the products as yellow-or-
ange solids. The complexes were purified by a further precipitation
from a CH2Cl2/Et2O solvent mixture.
m
.
4.8. X-ray measurements and structure determination of 3a(BF4)
Crystal data for 3a(BF4), C20H29PNOBF4Pd: M = 523.62, mono-
clinic, space group P21/c, a = 11.308(2) Å, b = 18.493(3) Å,
c = 12.149(3) Å, b = 114.21(4)°, V = 2317.1(8) Å3, Z = 4, Dcalc
=
3a(BF4) (1.32 g, 84%). Anal. Calc. for C20H29BF4NOPPd: C, 45.87;
1.501 g cmꢀ3
, k(Mo Ka) = 0.71073 Å, l(Mo Ka ,
) = 0.912 mmꢀ1
H, 5.58; N, 2.67. Found: C, 46.09; H, 5.40; N, 2.67%. IR (Nujol): m(B–
F(000) = 1064.
F) at 1054 cmꢀ1. Molar conductivity: 61.5 ohmꢀ1 cm2 molꢀ1 for a
1.0 ꢁ 10ꢀ3 mol/l CH2Cl2 solution at 25 °C.
A yellow crystal was lodged in Lindemann glass capillary and
centered on a four circle Philips PW1100 diffractometer using
graphite monochromated Mo Ka radiation (0.71073 Å), following
3b(BF4) (1.29 g, 72%). Anal. Calc. for C26H33BF4NOPPd: C, 52.07;
H, 5.55; N, 2.34%. Found: C, 52.06; H 5.45; N, 2.36%. IR (Nujol):
m(B–
the standard procedures at room temperature. All intensities were
corrected for Lorentz polarization and absorption [23]. The struc-
tures were solved by standard direct methods [24]. Refinement
F) at 1053 cmꢀ1. Molar conductivity: 69.2 ohmꢀ1 cm2 molꢀ1 for a
1.0 ꢁ 10ꢀ3mol/l CH2Cl2 solution.

3938
B. Crociani et al. / Journal of Organometallic Chemistry 693 (2008) 3932–3938
[7] G. Delapierre, J.M. Brunel, T. Constantieux, G. Buono, Tetrahedron: Asymmetr.
12 (2001) 1345.
[8] S. Antonaroli, B. Crociani, J. Organomet. Chem. 560 (1998) 137.
[9] G. Bandoli, A. Dolmella, L. Crociani, S. Antonaroli, B. Crociani, Transition Met.
Chem. 25 (2000) 17.
was carried out by full-matrix least-squares procedures (based on
F2o) using anisotropic temperature factors for all non-hydrogen
atoms. Hydrogen atoms were introduced in calculated positions
in their described geometries and during refinement were allowed
to ride on the attached carbon atoms with fixed isotropic thermal
parameters (1.2Uequiv) of the parent carbon atom. For a total of 278
[10] B. Crociani, S. Antonaroli, L. Canovese, F. Visentin, P. Uguagliati, Inorg. Chim.
Acta 315 (2001) 172.
[11] B. Crociani, S. Antonaroli, G. Bandoli, L. Canovese, F. Visentin, P. Uguagliati,
Organometallics 18 (1999) 1137. and references therein.
[12] B. Jedlicka, R.E. Rülke, W. Weissensteiner, R. Fernández-Galán, F.A. Jalón, B.R.
Manzano, J. Rodríguez-de la Fuente, N. Valdman, H. Kooijman, A.L. Spek, J.
Organomet. Chem. 516 (1996) 97;
parameters, wR0 = [
and conventional R = 0.055, based on the F values of 4093 reflec-
tions having I P 2 (I). Structure refinement and final geometrical
R R
w(F2o–F2c)2/ w(F2o)2]1/2 = 0.163, S = 1.152,
r
calculations were carried out with SHELXL-97 [25] program, imple-
mented in the WinGX package [26].
R. Fernández-Galán, F.A. Jalón, B.R. Manzano, J. Rodríguez-de la Fuente, M.
Vrahani, B. Jedlicka, W. Weissensteiner, Organometallics 16 (1997) 3758;
K. Selvakumar, M. Valentini, M. Wörle, P.S. Pregosin, A. Albinati,
Organometallics 18 (1999) 1207;
F.A. Jalón, B.R. Manzano, F. Gómez-de la Torre, A.M. López-Agenjo, A.M.
Rodríguez, W. Weissensteiner, T. Sturm, J. Mahía, M. Maestro, J. Chem. Soc.,
Dalton Trans. (2001) 2417;
M. Zehnder, M. Neuburger, S. Schaffner, M. Jufer, D.A. Plattner, Eur. J. Inorg.
Chem. (2002) 1511;
B. Crociani, S. Antonaroli, L. Canovese, P. Uguagliati, F. Visentin, Eur. J. Inorg.
Chem. (2004) 732.
4.9. General procedure for catalysis
The reactions were carried out under an inert atmosphere (ar-
gon). The coupling products were identified by their GC–MS and
1H NMR spectra. In a typical experiment (entry 1 of Table 3), a
50 ml glass reactor was charged with 4-bromoacetophenone
(0.80 g, 4.0 mmol), phenylboronic acid (0.73 g, 6.0 mmol), K2CO3
(1.10 g, 8.0 mmol), n-undecane (0.16 g, 1.0 mmol, as the gas chro-
matographic internal standard) and 12 ml of freshly distilled tolu-
[13] (a) P. Braunstein, J. Zhang, R. Welter, Dalton Trans. (2003) 507;
(b) M. Agostinho, P. Braunstein, R. Welter, Dalton Trans. (2007) 759.
[14] M. Agostinho, A. Banu, P. Braunstein, R. Welter, X. Morise, Acta Crystallogr. C62
(2006) m81.
[15] J. Sprinz, M. Kiefer, G. Helmchem, M. Reggelin, G. Huttner, O. Walter, L. Zsolnai,
Tetrahedron Lett. 35 (1994) 1523;
ene. To the resulting suspension 100
l
l of a 4.0 ꢁ 10ꢀ4 mol/l
solution of complex 2, in toluene were added, and the mixture
was heated under magnetic stirring at 110 °C for 2 h. After cooling
to room temperature and filtration on celite, the raw reaction mix-
ture was analyzed by GLC.
N. Baltzer, L. Macko, S. Schaffner, M. Zehnder, Helv. Chim. Acta 79 (1996) 803;
S. Schaffner, L. Macko, M. Neuburger, M. Zehnder, Helv. Chim. Acta 80 (1997)
463.
[16] R.B. Bedford, C.S.J. Cazin, D. Holder, Coord. Chem. Rev. 248 (2004) 2283. and
references therein.
[17] (a) M.-T. Chen, C.-A. Huang, C.-T. Chen, Eur. J. Inorg. Chem. (2008) 3142;
(b) J.V. Kingston, J.G. Verkade, J. Org. Chem. 72 (2007) 2816;
(c) S.K. Schneider, P. Roembke, G.R. Julius, H.G. Raubenheimer, W.A.
Herrmann, Adv. Synth. Catal. 348 (2006) 1862;
5. Supplementary material
(d) C.J. O’Brien, E.A.B. Kantchev, C. Valente, N. Hadei, G.A. Chass, A. Lough, A.C.
Hopkinson, M.G. Organ, Chem. Eur. J. 12 (2006) 4743;
(e) G.R. Rosa, C.H. Rosa, F. Rominger, J. Dupont, A.L. Monteiro, Inorg. Chim.
Acta 359 (2006) 1947;
(f) C. Song, Y. Ma, Q. Chai, C. Ma, W. Jang, M.B. Andrus, Tetrahedron 61 (2005)
7438.
CCDC 688238 contains the supplementary crystallographic
data for compound 3a(BF4). These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
[18] (a) M. Cui, J. Li, A. Yu, J. Zhang, Y. Wu, J. Mol. Catal. A: Chem. 290 (2008) 67;
(b) S.-B. Yu, X.-P. Hu, J. Deng, J.-D. Huang, D.-Y. Wang, Z.-C. Duan, Z. Zheng,
Tetrahedron Lett. 49 (2008) 1253;
References
(c) C. Xu, J.-F. Gong, T. Guo, Y.-H. Zhang, Y.-J. Wu, J. Mol. Catal. A: Chem. 279
(2008) 69;
(d) C.A. Fleckestein, H. Plenio, Organometallics 26 (2007) 2758;
(e) T.E. Barder, J. Am. Chem. Soc. 128 (2006) 898;
(f) N. Marion, O. Navarro, J. Mei, E.D. Stevens, N.M. Scott, S.P. Nolan, J. Am.
Chem. Soc. 128 (2006) 4101.
[1] N. Miyaura, in: F. Diederich, A. de Mejere (Eds.), Metal-Catalyzed Cross-
Coupling Reactions, second ed., Wiley-VCH, Weinheim, 2004 (Chapter 2);
A. Suzuki, in: E. Negishi, A. de Mejere (Eds.), Handbook of Organopalladium
Chemistry for Organic Synthesis, Wiley Interscience, New York, 2002 (Chapter
III);
J.-P. Corbet, G. Mignani, Chem. Rev. 107 (2007) 874;
L. Yin, J. Liebscher, Chem. Rev. 107 (2007) 133.
[19] D.D. Perrin, W.L. Armarego, Purification of Laboratory Chemicals, third ed.,
Pergamon, Oxford, 1988.
[20] R. Hartley, S.R. Jones, J. Orgamomet. Chem. 66 (1974) 465.
[21] M.C. Ashraf, T.G. Burrowes, W.R. Jackson, Aust. J. Chem. 29 (1976) 2643.
[22] P. Barbaro, P.S. Pregosin, R. Salzmann, A. Albinati, R.W. Kunz, Organometallics
14 (1995) 5160.
[23] A.T.C. North, D.C. Philips, F.S. Mathews, Acta Crystallogr. A24 (1968) 351.
[24] A. Altomare, M.C. Burla, M. Camalli, G.L. Cascarano, C. Giacovazzo, A.
Guagliardi, A.G.G. Moliterni, G. Polidori, R. Spagna, ‘‘SIR–97” J. Appl.
Crystallogr. 32 (1999) 115.
[25] G.M. Sheldrick, ‘‘SHELXL-97” Program for the Refinement of Crystal Structures,
University of Göttingen, Germany, 1997.
[2] Z. Weng, S. Teo, T.S.A. Hor, Acc. Chem. Res. (2007) 676.
[3] (a) A. Scrivanti, V. Beghetto, U. Matteoli, S. Antonaroli, A. Marini, F. Mandoj, R.
Paolesse, B. Crociani, Tetrahedron Lett. 45 (2004) 5861;
(b) A. Scrivanti, V. Beghetto, U. Matteoli, S. Antonaroli, A. Marini, B. Crociani,
Tetrahedron 61 (2005) 9752;
(c) B. Crociani, S. Antonaroli, A. Marini, A. Scrivanti, U. Matteoli, Dalton Trans.
(2006) 2698.
[4] R.B. Bedford, S.L. Hazelwood (née Welch), P.N. Horton, M.B. Hursthouse, Chem.
Commun. (2003) 4164.
[5] R.B. Bedford, C.S.J. Cazin, S.L. Hazelwood (née Welch), Angew. Chem., Int. Ed. 41
(2002) 4120. and references therein.
[6] K.K. Klausmeyer, R.P. Feazell, J.H. Reibenspies, Inorg. Chem. 43 (2004) 1130.
[26] L.J. Farrugia, J. Appl. Crystallogr. 32 (1999) 837.