Novel unsymmetrical PCP′ pincer ligands and their palladium(II) complexes

Article abstract of DOI:10.1016/j.jorganchem.2003.08.017

Synthetic routes towards novel PCP′ pincer ligands were devised. Ligand 1-(Pr₂ⁱPOCH₂) -3-(Bu₂^tPCH₂) (C₆H₄) is prepared in a three step synthesis from 1,3-benzenedimethanol and 1-(Pr₂ⁱPO)-3- (Bu₂^tPCH₂)(C₆H₄) is accessible in three steps from 3-hydroxybenzylalcohol. Both their palladium(II) complexes are prepared in good yields but are distinctly different since [PdCl{(C₆H₃) (OPPr₂ⁱ)-2-(CH₂PBu₂ ^t)-6}] possesses two five-membered palladacycles, whereas [PdCl{(C₆H₃)(CH₂PBu₂ ^t)-2-(CH₂OPPr₂ⁱ)-6}] is unusual for a pincer complex in that it contains both five- and six-membered palladacycles. Both compounds also represent the first examples of pincer complexes where one donor is a phosphinite and the other is a phosphine. The X-ray structures of these complexes were solved and are discussed. The data reveal that an increase in the metallacycle ring-size leads to changes in bond lengths, but more importantly to significant increases in the bond angles.

Full text of DOI:10.1016/j.jorganchem.2003.08.017

Journal of Organometallic Chemistry 687 (2003) 185Á189
/
www.elsevier.com/locate/jorganchem
Novel unsymmetrical PCP? pincer ligands and their palladium(II)
complexes
a,
Michael R. Eberhard *, Shiro Matsukawa , Yohsuke Yamamoto ,
b
b,1
a
Craig M. Jensen
a
Department of Chemistry, University of Hawaii, 2545 The Mall, Honolulu, HI 96822-2275, USA
b
Department of Chemistry, Graduate School of Science, Hiroshima University 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
Received 2 July 2003; received in revised form 15 August 2003; accepted 18 August 2003
Abstract
Synthetic routes towards novel PCP? pincer ligands were devised. Ligand 1-(Pr POCH )-3-(Bu PCH )(C H ) is prepared in a
three step synthesis from 1,3-benzenedimethanol and 1-(Pr PO)-3-(Bu PCH )(C H ) is accessible in three steps from 3-
i
t
2
2
2
2
6
4
i
t
2
2
2
6
4
hydroxybenzylalcohol. Both their palladium(II) complexes are prepared in good yields but are distinctly different since
i
t
2
[
PdClf(C H )(OPPr )-2-(CH PBu )-6g]
possesses
two
five-membered
palladacycles,
whereas
6
3
2
2
t
2
i
2
[
PdClf(C H )(CH PBu )-2-(CH OPPr )-6g] is unusual for a pincer complex in that it contains both five- and six-membered
6
3
2
2
palladacycles. Both compounds also represent the first examples of pincer complexes where one donor is a phosphinite and the other
is a phosphine. The X-ray structures of these complexes were solved and are discussed. The data reveal that an increase in the
metallacycle ring-size leads to changes in bond lengths, but more importantly to significant increases in the bond angles.
#
2003 Elsevier B.V. All rights reserved.
Keywords: Pincer; Phosphorus; Palladium; Unsymmetrical; Complexes
1
2
1
. Introduction
and phosphites [4] (Xꢀ
/
Yꢀ
/
O, R ꢀ
/
R ꢀ
/
O-alkyl or O-
H [5], have been
3
aryl), as well as ligands where R "
/
A wide variety of PCP pincer ligands have been
synthesised. However, to the best of our knowledge
there are no synthetic procedures available for PCP?
prepared in the last 30 years and are based on the
generic structure shown in Fig. 1. Several reviews on
pincer complexes and their chemistry have been pub-
lished [1].
1
2
pincer ligands where R "
/R
and/or X"Y. Such
/
ligands are however of great interest since this would
allow greater control over steric and electronic proper-
ties and may, for example, influence the activity of
complexes in homogeneous catalysis. Many unsymme-
trical diphosphines are known [6] and some of their
complexes have proven to be valuable in homogeneous
catalysis [6g,6h].
Steric and electronic properties of PCP pincer ligands
can be modified by varying the substituents on the
1
2
phosphorus (R and R ), the atom-linkage X and Y
between phosphorus and aryl-ring carbon, and the ring-
3
substituent R . Consequently, many examples of phos-
1
2
1
2
We have now developed such ligands where R "
and X"Y and prepared their palladium(II) complexes.
In this article we would like to describe the synthesis of
/R
phines [2] (Xꢀ
phosphinites [3] (Xꢀ
/
Yꢀ
/
CH , R ꢀ
/
R ꢀalkyl or aryl),
/
2
1
2
/
/
Yꢀ
/
O, R ꢀ
/
R ꢀalkyl or aryl)
/
i
2
i
t
2
1
1
[
-(Pr POCH )-3-(Bu PCH )(C H )
t
and
as
and
2
2
6
4
-(Pr PO)-3-(Bu PCH )(C H );
t
as
well
2
2
2
6
4
* Corresponding authors. Tel.:
438182.
ꢁ
/
1-808-5347064; fax: ꢁ
/
1-808-
i
PdClf(C H )(CH PBu )-2-(CH OPPr )-6g]
6
3
2
2
2
2
5
i
t
[
PdClf(C H )(OPPr )-2-(CH PBu )-6g]: The X-ray
6
3
2
2
2
E-mail address: chmre@gold.chem.hawaii.edu (M.R. Eberhard).
1
To whom correspondence pertaining to crystallographic studies
should be addressed. yyama@sci.hiroshima-u.ac.jp (Y. Yamamoto).
crystallographic structures for both complexes are
described and compared.
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.08.017

186
M.R. Eberhard et al. / Journal of Organometallic Chemistry 687 (2003) 185Á189
/
Fig. 1. Design of PCP pincer ligands.
2
. Results and discussion
.1. Ligand and complex synthesis
Mixed phosphinoÁphosphinito pincer ligand 3 was
2
/
synthesised via a three step synthesis from 3-hydroxy-
benzylalcohol 1 (Scheme 1). Reaction of 1 with PBr3
gives 3-hydroxybenzylbromide according to a published
t
Fig. 2. Displacement ellipsoid plot (50% probability level) of 4.
Hydrogen atoms have been omitted for clarity. Pertinent bond lengths
procedure [7], which after reaction with HPBu in
acetone leads to compound 2 in quantitative yield.
2
˚
(
A) and angles (8): Pd(1)Ã
/
Cl(1) 2.3938(6); Pd(1)Ã
P(2) 2.2495(7); Pd(1)ÃC(1) 2.008(2); Cl(1)Ã
01.17(2); Cl(1)ÃPd(1)ÃP(2) 95.16(2); Cl(1)ÃPd(1)ÃC(1) 175.82(7);
P(1)ÃPd(1)ÃP(2) 163.03(2); P(1)ÃPd(1)ÃC(1) 82.60(7); P(2)ÃPd(1)Ã
C(1) 80.95(7).
/
P(1) 2.3198(6);
i
Addition of ClPPr in THF in the presence of DMAP
yields the air-sensitive pincer ligand 3 in 81% yield.
Pd(1)Ã
/
/
/
Pd(1)ÃP(1)
/
2
1
/
/
/
/
/
/
/
/
/
/
Refluxing a suspension of [PdCl (cod)] and ligand 3 in
2
toluene furnishes complex 4 in 44% yield as a pale
1
3
1
yellow solid. The P{ H} spectrum of 4 is characterised
by a large trans-coupling between the inequivalent
Compound 8 is unusual in that it contains both five-
and six-membered metallacycles. ‘Classical’ pincer com-
plexes such as 4 possess two five-membered metalla-
cycles. We recently reported on the synthesis of
2
phosphorus nuclei with J(P,P?) 429 Hz.
Complex 4 formed suitable crystals for X-ray diffrac-
tion by slow diffusion of pentane into a saturated
solution of 4 in CH Cl . The molecular structure is
i
i
[
cer complex containing both five- and six-membered
PdClf(C H )(OPPr )-2-(CH OPPr )-6g]; the first pin-
6
3
2
2
2
2
2
shown in Fig. 2.
The bond lengths are within the typical range. Note
that Pd(1)ÃP(1) is slightly longer than Pd(1)ÃP(2)
2.3198(6) A vs. 2.2495(7) A]. The structure is distorted
metallacycles [8]. Venanzi et al. synthesised
[
MBr{(C H )((CH ) PPh ) -2,6}] (MꢀPd, Pt), the
/
6
3
2 2
2 2
/
/
˚
˚
only example of a PCP pincer complex with two six-
membered metallacycles [9]. Complexes 4 and 8 are both
stable to heat, air and moisture in the solid state, as well
as in solution. No ligand dissociation is observed in
solution at room temperature, as well as up to 180 8C.
The crystal structure of complex 8 is shown in Fig. 3.
[
square-planar with the five-membered palladacycles
showing two envelope conformations.
1
,3-Benzenedimethanol 5 is a suitable starting mate-
rial for the synthesis of unsymmetrical ligand 7 and
complex 8 (Scheme 2). Reaction of 5 with one equivalent
of SOCl in the presence of one equivalent pyridine gives
All bond lengths are within the typical range. Pd(1)Ã
P(1) is slightly longer than Pd(1)ÃP(2) (2.3123(9) vs.
.282(1) A). Increasing the ring-size of one of the
palladacycles in 8, compared to 4, leads to a lengthening
/
2
/
1
this compound is unreactive towards HPBu in acetone
-(HOCH )-3-(ClCH )(C H ) in 44% yield. However,
2 2 6 4
t
2
˚
2
under reflux. Addition of NaI facilitates nucleophilic
attack of the secondary phosphine furnishing 6 (89%
˚
P(2) with 2.282(1) A for 8 and 2.2495(7) for 4,
of Pd(1)Ã
/
i
whilst Pd(1)Ã
/
P(1) does not change in both complexes
yield) after addition of NEt . Reaction of ClPPr in
3
2
˚
THF in the presence of DMAP yields the air- and
moisture-sensitive unsymmetrical pincer ligand 7 in 56%
yield. Complex 8 is formed from the reaction of
(2.3198(6) for 4 and 2.3123(9) A for 8). The distorted
square-planar structure shows the five-membered me-
tallacycle in the expected distorted envelope conforma-
tion, whereas the six-membered metallacycle reveals a
boat-conformation.
[
Again, two doublets with a typical large coupling of
PdCl (cod)] with 7 in refluxing toluene (72% yield).
2
2
J(P,P?) 388 Hz are observed for trans-co-ordinated
phosphorus atoms.
Most notably, when comparing the data of complex 4
with complex 8, increasing the ring-size of one of the
t
2
i
2
Scheme 1. Reagents and conditions: (i) PBr
toluene, reflux.
3
, CHCl ; (ii) HPBu ; acetone, reflux, then NEt
3
3
, Et
2
O; (iii) ClPPr ; DMAP, THF, rt; (iv) [PdCl (cod)],
2

M.R. Eberhard et al. / Journal of Organometallic Chemistry 687 (2003) 185Á
/
189
187
t
Scheme 2. Reagents and conditions: (i) one equivalent SOCl , one equivalent pyridine, CH
2
2
2 2 3 2
Cl ; (ii) HPBu ; NaI, acetone, reflux, then NEt , Et O;
i
(
iii) ClPPr ; DMAP, THF, rt; (iv) [PdCl (cod)], toluene, reflux.
2
2
benzylalcohol, 1,3-benzenedimethanol, 4-dimethylami-
nopyridine DMAP, chlorodiisopropylphosphine, di-
tert-butylphosphine and Py were purchased from Al-
drich and used without further purification. Silica gel
(
100Á200 mesh), alumina, celite and magnesium sulfate
/
were purchased from Fisher Scientific. [PdCl (cod)] was
2
prepared according to a previously published method
[
10].
1
13
1
31
1
H-, C{ H}- and P{ H}-NMR spectra were re-
corded on a Varian Unity Inova 300 Spectrometer at
ambient temperature of the probe using the deuterated
solvent to provide the field/frequency lock. Chemical
shifts are reported in ppm relative to high frequency of
Fig. 3. Displacement ellipsoid plot (50% probability level) of 8.
Hydrogen atoms have been omitted for clarity. Pertinent bond lengths
˚
(
A) and angles (8): Pd(1)Ã
P(2) 2.282(1); Pd(1)Ã
/
Cl(1) 2.396(1); Pd(1)Ã
C(1) 2.043(4); Cl(1)ÃPd(1)Ã
P(2) 89.83(4); Cl(1)ÃPd(1)ÃC(1) 177.7(1); P(1)Ã
71.04(4); P(1)ÃPd(1)ÃC(1) 82.5(1); P(2)ÃPd(1)ÃC(1) 90.1(1).
/
P(1) 2.3123(9); Pd(1)Ã
P(1) 97.40(4); Cl(1)Ã
Pd(1)ÃP(2)
/
/
/
/
/
Pd(1)Ã
/
/
/
/
/
1
13
1
Me Si for H and
4
C{ H} and relative to high
31
1
/
/
/
/
1
frequency of 85% H PO for
3
P{ H}*Elemental
/
4
analysis were performed by Oneida Research Services.
metallacycles of these two related pincer complexes
leads to a ‘relaxation’ of the structure. For example,
the P(1)Ã
63.03(2)8 in 4 to 171.04(4)8 in 8; the Cl(1)Ã
angle decreases from 95.16(2)8 in 4 to 89.83(4)8 in 8, and
the P(2)ÃPd(1)ÃC(1) angle of 4 increases from 80.95(7)
to 90.1(1)8 in 8 (Table 1).
/
Pd(1)Ã
/
P(2) angle increases significantly from
1
/
Pd(1)ÃP(2)
/
/
/
Table 1
Crystallographic data
Compound
4
8
Empirical formula
M
C
21
H
37ClOP
2
Pd
C
22 2
H39ClOP Pd
3
. Conclusion
509.32
200
523.35
200
yellow
T (K)
Colour
In conclusion, we have prepared the first examples of
Yellow
Monoclinic
mixed phosphinoÁphosphinito pincer ligands. A series
/
Crystal system
a
Orthorhombic
P2
of palladium(II) complexes derived from these ligands
were prepared. Both structures are related by virtue of
one additional methylene-group in 8 compared to 4.
This has important structural consequences, leading to a
significant increase in bond angles in 8 compared to 4.
The synthetic methodologies described in this article will
be useful in expanding the family of pincer complexes.
For example, one can envisage structures with only one
chiral side-arm.
Space group
˚
P2
1
/n
1 1 1
2 2
a (A)
˚
15.1500(1)
10.8770(2)
15.9130(3)
90
11.2560(2)
14.0230(2)
16.1210(3)
90
b (A)
˚
c (A)
aꢀ
/
g (8)
b (8)
112.587(1)
2421.11(7)
4
90
3
U (A )
˚
2544.59(7)
4
0.970
Z
m MoÁ
/
K
a
(cmꢂ1
Crystal dimensions (mm)
)
1.017
0.400ꢃ
.250
12.6Á
/
0.350ꢃ
/
0.350ꢃ
0.250
12.6Á
/
0.300ꢃ
/
0
u Range (8)
/27.9
/27.9
Data/restraints/parameters 3862/0/235
3361/0/244
3399
Reflections observed
Final R and wR indices
Conventional R index
3977
0.0297, 0.0723
0.0297
4
. Experimental
b
2
2
0.0321, 0.0656
0.0321
2
2
b
4
.1. General procedure
[F ꢀ
/
3s(F )]
2
Reflections with F ꢀ
/
3862
3361
2
s(F )
3
Goodness-of-fit
All manipulations were carried out using standard
Schlenk procedures under nitrogen. Solvents (CH Cl ,
1.056
1.063
2
2
a
toluene, THF, Et O) were freshly distilled from either
2
A chirality test of the crystal of compound 8 was not performed.
2
b
2
1/[s (F
CaH or K/benzophenone under nitrogen. 3-Hydroxy-
2
wꢀ
/
o
/
o
)ꢁ0.0856(F ) ].

188
M.R. Eberhard et al. / Journal of Organometallic Chemistry 687 (2003) 185Á189
/
4
4
.1.1. Ligand and complex synthesis
30.5, 34.0, 34.3, 35.43, 35.6, 109.6 (d, Jꢀ
d, Jꢀ19.8 Hz), 126.7, 144.0, 152.1 (d, Jꢀ
166.4 (d, Jꢀ
CD Cl ): dꢀ73.6 (d, Jꢀ
/
15.5 Hz), 118.7
(
/
/
18.4 Hz),
t
2
t
2
31
1
.1.1.1.
/
1-(HO)-3-(Bu PCH )(C H ) (2).
/
HPBu (0.749
/
13.1 Hz).
P{ H}-NMR (121 MHz,
388 Hz, P Bu ), 187.1 (d,
2
6
4
t
g, 0.95 ml, 5.12 mmol) was added dropwise to a stirred
/
/
2
2
2
i
solution of 1-(HO)-3-(BrCH )(C H ) [7] (0.953 g, 5.12
2
Jꢀ388 Hz, OP Pr ). C H ClOP Pd (509.34): Anal.
/
6
4
2 21 37 2
mmol) in degassed acetone (40 ml). The mixture was
heated to reflux for 6 h and then cooled to room
temperature (r.t.); the solvent was removed, the colorless
Calc. C, 49.52; H, 7.32. Found: C, 49.36; H, 7.02%.
4.1.1.4. 1-(HOCH )-3-(ClCH )(C H ). Thionyl chlo-
4
2
2
6
residue washed with Et O and dried in vacuum. It was
2
ride (4.82 g, 2.96 ml, 40.5 mmol) was added dropwise to
a stirred solution of 1,3-benzenedimethanol 5 (5.52 g, 40
mmol) and Py (3.19 g, 3.27 ml, 40.3 mmol) in CH Cl
then suspended in Et O and NEt (0.758 g, 1.05 ml, 7.5
2
3
mmol) was added dropwise. After stirring for 30 min the
suspension was filtered through alumina and the filtrate
was concentrated in vacuum to give 2 (1.35 g, 5.07
2
2
(40 ml) at 0 8C. The mixture was stirred overnight at r.t.
and then poured into ice-water (100 ml), extracted with
CH Cl , washed with a saturated NaHCO solution and
1
mmol, 99%) as a clear oil. H-NMR (300 MHz,
2
2
3
CD Cl ): dꢀ
/
1.15 (d, Jꢀ
/
10.8 Hz, 18H, C(CH3)3),
7.16 (m, 4H, ArH).
C{ H}-NMR (75 MHz, CD Cl ): dꢀ28.5 (d, Jꢀ23
21 Hz), 112.7, 116.8
8 Hz), 129.2, 143.6 (d, Jꢀ13
Hz), 156.1. P{ H}-NMR (121 MHz, CD Cl ): dꢀ
water, dried over MgSO and concentrated in vacuum.
4
2
2
2
.82 (s, 2H, CH P), 6.59Á
/
The crude product was purified via column chromato-
graphy on silica. The impurities are first eluted with
hexanes and the product with CH Cl to give 1-
2
1
3
1
/
/
2
2
Hz), 29.6 (d, Jꢀ
/
13 Hz), 31.7 (d, Jꢀ
/
2
2
(
d, Jꢀ9 Hz), 121.6 (d, Jꢀ
/
/
/
(HOCH )-3-(ClCH )(C H ) (2.76 g, 17.6 mmol, 44%)
2 2 6 4
3
1
1
1
/
as a colorless liquid. H-NMR (300 MHz, CD Cl ): dꢀ
/
2
2
2
2
3
5.4.
2.25 (s, 1H, OH), 4.62 (s, 2H, CH Cl), 4.66 (s, 2H,
2
1
3
1
7.28 (m, 4H, ArH). C{ H}-NMR (75
CH O), 7.41Á
/
2
i
2
t
2
i
2
4
.1.1.2.
/
1-(Pr PO)-3-(Bu PCH )(C H ) (3).
/
ClPPr
MHz, CD Cl ): dꢀ46.6, 64.8, 127.1, 127.3, 127.9,
/
2
6
4
2
2
(
0.153 g, 0.160 ml, 1 mmol) was added dropwise to a
stirred solution of 2 (0.252 g, 1 mmol) and DMAP
0.122 g, 1 mmol) in THF (10 ml) at r.t. A precipitate
129.1, 138.1, 142.1.
t
2
t
4.1.1.5. 1-(HOCH )-3-(Bu PCH )(C H ) (6). HPBu2
(
/
/
2
2
6
4
formed immediately and the mixture was stirred over-
night. The solvent was removed in vacuum and the
residue extracted repeatedly with toluene. The toluene
extracts were filtered over celite and the filtrate was
(1.75 g, 2.22 ml, 12 mmol) was added dropwise to a
stirred solution of 1-(HOCH )-3-(ClCH )(C H ) (1.879
g, 12 mmol) and NaI (2.25 g, 15 mmol) in degassed
acetone at r.t. The mixture was heated to reflux for 5 h
and then cooled to r.t., the solvent was removed and the
2
2
6
4
concentrated in vacuum to give 3 (0.275 g, 0.81 mmol,
1
8
1%) as an oil. H-NMR (300 MHz, CD Cl ): dꢀ
/
1.02
1.83 (m, 2H,
2.7 Hz, 2H, CH P), 6.77Á7.15
m, 4H, ArH). C{ H}-NMR (75 MHz, CD Cl ): dꢀ
residue washed three times with Et O (15 ml each). It
2
2
2
(
d, Jꢀ
/
10.8 Hz, 18H, C(CH ) ), 1.78Á
/
was then suspended in Et O (30 ml) and NEt (1.82 g,
2
3
3
3
CH(CH ) ), 2.71 (d, Jꢀ
/
/
2.51 ml, 18 mmol) was added dropwise. After stirring
for 30 min the suspension was filtered through alumina
and the filtrate was concentrated in vacuum to give pure
3
2
2
1
3
1
(
/
2
2
1
2
1
7.0 (d, Jꢀ
8.6, 28.8, 29.7 (d, Jꢀ
15.7 (d, Jꢀ10.1 Hz), 119.95, 120.08, 120.19, 123.1 (d,
8.1 Hz), 129.0, 143.7 (d, Jꢀ12.6 Hz), 159.5 (d, Jꢀ
/
8.2 Hz), 17.8 (d, Jꢀ
/
19.8 Hz), 28.4, 28.5,
1
/
13.5 Hz), 31.8 (d, Jꢀ
/
22.7 Hz),
6 (2.83 g, 10.6 mmol, 89%) as a clear oil. H-NMR (300
/
MHz, CD Cl ): dꢀ
/
1.14 (d, 18H, Jꢀ/10.8 Hz,
2
2
Jꢀ
/
/
/
C(CH ) ), 2.86 (d, 2H, Jꢀ2.7 Hz, CH P), 4.63 (s, 2H,
/
3
3
2
3
1
1
13
1
8
(
.7 Hz). P{ H}-NMR (121 MHz, CD Cl ): dꢀ
/
35.7
CH OH), 7.09Á
/
7.39 (m, 4H, ArH). C{ H}-NMR (75
MHz, CD Cl ): dꢀ28.4 (d, Jꢀ24 Hz), 29.6 (d, Jꢀ13
23 Hz), 65.0, 123.9, 128.1, 128.2, 128.7
2
2
2
t
P Bu ), 150.0 (OP Pr ).
i
/
/
/
2
2
2
2
Hz), 31.7 (d, Jꢀ
(d, Jꢀ8 Hz), 141.2, 142.4 (d, Jꢀ
NMR (120 MHz): dꢀ36.2.
/
i
2
t
2
31
1
4
.1.1.3.
solution of 3 (0.275 g, 0.81 mmol) in toluene (10 ml) was
/
[PdClf(C H )-2-(OPPr )-6-(CH PBu )g] (4). A
/
/
13 Hz). P{ H}-
6
3
2
/
added dropwise to a stirred suspension of [PdCl (cod)]
2
i
2
t
2
i
ClPPr2
(
0.231 g, 0.81 mmol) in toluene (10 ml). The suspension
4.1.1.6.
/
1-(Pr POCH )-3-(Bu PCH )(C H ) (7).
/
2
2
6
4
was refluxed for 4 h during which time a clear yellow
solution formed. The solvent was removed in vacuum
and the solid was dissolved in CH Cl and filtered over a
(1.62 g, 1.69 ml, 10.6 mmol) was added dropwise to a
stirred solution of 6 (2.83 g, 10.6 mmol) and DMAP
(1.30 g, 10.6 mmol) in THF at r.t. A precipitate formed
immediately and the mixture was stirred overnight. The
solvent was removed in vacuum and the residue
extracted repeatedly with toluene. The toluene extracts
were filtered over celite and the filtrate was concentrated
2
2
short silica pad to give 4 (2.76 g, 17.6 mmol, 44%) as a
yellow solid. Single crystals were grown from CH Cl Á
/
2
2
1
pentane. H-NMR (300 MHz, CDCl ): dꢀ
/
1.20Á
2.43 (m, 2H,
9.3 Hz, 2H, CH P), 6.60Á7.00
/
1.60
3
(
m, 30H, C(CH ) and CH(CH ) ), 2.21Á
/
3
3
3 2
CH(CH ) ), 3.23 (d, Jꢀ
/
/
in vacuum to give 7 (2.27 g, 6.0 mmol, 56%) as an oil.
1
3
2
2
1
3
1
(
m, 3H, ArH). C{ H}-NMR (75 MHz, CDCl ): dꢀ
/
H-NMR (300 MHz, CDCl ): dꢀ
/
0.96Á1.16 (dd and d,
/
3
3
1
7.0, 17.7, 17.8, 28.6, 28.6, 28.8, 28.9, 29.4, 29.5, 29.9,
30H, CH(CH3)2 and C(CH ) , overlapping signals),
3 3

M.R. Eberhard et al. / Journal of Organometallic Chemistry 687 (2003) 185Á
/
189
189
1
.78 (m, 2H, CH(CH ) ), 2.82 (d, Jꢀ
/
2.7 Hz, 2H,
22.2 Hz, 2H, CH O), 7.10Á7.31
1
5. Supplementary material
3
2
CH P), 4.75 (d, Jꢀ
/
/
2
2
1
3
(
m, 4H, ArH). C{ H}-NMR (75 MHz, CDCl ): dꢀ
/
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 210823 and 210824 for
compounds 4 and 8. Copies of this information may
be obtained free of charge from The Director, CCDC,
3
1
7.3 (d, Jꢀ
8.8, 30.0 (d, Jꢀ
20.8 Hz), 124.7, 128.4, 128.9, 129.0, 129.1, 139.6 (d,
/
8.2 Hz), 18.2 (d, Jꢀ
/
20.3 Hz), 28.2, 28.4,
2
/
13.0 Hz), 32.0 (d, Jꢀ21.7 Hz), 74.5 (d,
/
Jꢀ
Jꢀ
MHz, CDCl ): dꢀ
/
3
1
1
/
6.8 Hz), 141.9 (d, Jꢀ12.1 Hz). P{ H}-NMR (121
/
t
36.0 (P Bu ), 155.6 (OP Pr ).
i
12 Union Road, Cambridge CB2 1EZ, UK (Fax: ꢁ
/44-
/
3
2 2
1223-336033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
i
2
t
2
4
(
.1.1.7.
8). A solution of 7 (0.382 g, 1 mmol) in toluene (10 ml)
/
[PdClf(C H )-2-(CH OPPr )-6-(CH PBu )]
6
3
2
2
Acknowledgements
was added dropwise to a suspension of [PdCl (cod)]
2
(
0.285 g, 1 mmol) in toluene (10 ml). The suspension was
This work was supported by the U.S. Department of
Energy Hydrogen Program.
refluxed for 4 h during which time a clear yellow
solution formed. The solvent was removed in vacuum
and the solid was dissolved in CH Cl and the solution
2
2
filtered over a short silica pad to give 8 (0.378 g, 0.72
mmol, 72%) as a yellow solid. Single crystals were grown
References
1
pentane. H-NMR (300 MHz, CD Cl ):
from CH Cl Á
/
[1] (a) M. Albrecht, G. van Koten, Angew. Chemie Int. Ed. 40 (2001)
2
2
2
2
1
2
3
750;
b) J.T. Singleton, Tetrahedron 59 (2003) 1837;
dꢀ
.30Á
overlapping signals), 2.42Á
.26 (d, 2H, Jꢀ8.7 Hz, CH P), 4.74 (d, 2H, Jꢀ
CH O), 6.82Á7.22 (m, 3H, ArH). C{ H}-NMR (75
MHz, CD Cl ): dꢀ16.9, 18.0 (d, Jꢀ6.3 Hz), 26.6 (d,
4.4 Hz), 26.9 (d, Jꢀ4.8 Hz), 29.5 (d, Jꢀ3.4 Hz),
3.8 (d, Jꢀ20.3 Hz), 35.39, 35.45, 35.54, 35.61, 79.3 (d,
Jꢀ5 Hz, CH O), 124.5 (d, Jꢀ18 Hz), 125.0 (d, Jꢀ20
Hz), 138.8 (d, Jꢀ12 Hz), 150.3, 152.1 (d, Jꢀ21 Hz).
P{ H}-NMR (121 MHz, CD Cl ): dꢀ82.2 (d, Jꢀ405
/
1.02 (dd, 6H, Jꢀ
/
14.1 Hz, Jꢀ
/
7.2 Hz, CH(CH ) ),
3 2
(
(
1
/1.44 (dd and d, 24H, CH(CH ) and C(CH ) ,
3
2
3 3
c) M.E. van der Boom, D. Milstein, Chem. Rev. 103 (2003) 1759.
/
2.62 (m, 2H, CH(CH ) ),
3 2
[2] C.J. Moulton, B.L. Shaw, J. Chem. Soc. Dalton Trans. (1976)
1020.
3
/
/
19.5 Hz,
2
1
3
1
[
3] (a) D. Morales-Morales, C. Grause, K. Kasaoka, R. Redon, R.E.
Cremer, C.M. Jensen, Inorg. Chim. Acta 300Á302 (2000) 958;
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Chem. 24 (2000) 745.
/
2
/
/
/
2
2
(
Jꢀ
/
/
/
3
/
[4] F. Miyazaki, K. Yamaguchi, M. Shibasaki, Tetrahedron Lett. 40
(1999) 7378.
/
/
/
2
[
5] (a) H.A.Y. Mohammed, J.C. Grimm, K. Eichele, H.-G. Mack, B.
Speiser, F. Novak, M.G. Quintanilla, W.C. Kaska, H.A. Mayer,
Organometallics 21 (2002) 5775;
/
/
3
1
1
/
/
2
2
t
i
Hz, P Bu ), 150.9 (d, Jꢀ405 Hz, OP Pr ).
/
2
2
(b) T. Karlen, P. Dani, D.M. Grove, P. Steenwinkel, G. van
Koten, Organometallics 15 (1996) 5687;
C H ClOP Pd (523.36): Anal. Calc. C, 50.49; H,
2
2
39
2
(
c) I.P. Beletskaya, A.V. Chuchurjukin, H.P. Dijkstra, G.P.M.
van Klink, G. van Koten, Tetrahedron Lett. 41 (2000) 1075;
d) P. Dani, G.P.M. van Klink, G. van Koten, Eur. J. Inorg.
7
.51. Found: C, 50.51; H, 7.06%.
(
Chem. (2000) 1465.
6] (a) D.K. Johnson, A.J. Carty, Chem. Commun. (1977) 903;
[
4.2. X-ray data collection and structure determination for
complexes 4 and 8
(
b) W.E. Hill, M.Q. Islam, T.R. Webb, C.A. McAuliffe, Inorg.
Chim. Acta 146 (1988) 111;
c) J.C. Briggs, C.A. McAuliffe, W.E. Hill, D.M.A. Minahan,
J.G. Taylor, G. Dyer, Inorg. Chem. 21 (1982) 4204;
d) S.M. Aucott, A.M.Z. Slawin, J.D. Woollins, J. Chem. Soc.
Dalton Trans. (2001) 2279;
(
Crystals of 4 suitable for X-ray analysis were obtained
from slow diffusion of pentane into a saturated solution
of 4 in CH Cl . Crystals of 8 suitable for X-ray analysis
(
2
2
(
(
e) S. Shue, C.-H. Tsao, S.C. Hung, J. Organomet. Chem. 312
1986) 53;
were obtained from slow diffusion of pentane into a
saturated solution of 8 in CH Cl . Intensity data were
2
2
(f) S.M. Aucott, A.M.Z. Slawin, J.D. Woollins, J. Organomet.
Chem. 582 (1999) 83;
collected at 200 K on a Mac Science DIP2030 imaging
plate equipped with graphite-monochromated MoÁ
(
g) C.P. Casey, E.L. Paulsen, E.W. Beuttenmueller, B.R. Proft,
B.A. Matter, D.R. Powell, J. Am. Chem. Soc. 121 (1999) 63;
h) C.-A. Carraz, E.J. Ditzel, A.G. Orpen, D.D. Ellis, P.G.
Pringle, G.J. Sunley, Chem. Commun. (2000) 1277.
[7] K.J. Przybilla, F. Voegtle, Chem. Ber. 122 (1989) 347.
/K
a
˚
radiation (lꢀ0.71073 A). Unit cell parameters were
/
(
determined by autoindexing several images in each data
set separately with program DENZO. For each data set,
rotation images were collected in 38 increments with a
total rotation of 1808 about f. Data were processed by
using SCALEPACK. The structure was solved using the
TEXSAN system and refined by full-matrix least-squares.
[8] Z. Wang, M.R. Eberhard, C.M. Jensen, S. Matsukawa, Y.
Yamamoto, J. Organomet. Chem. 681 (2003) 189.
[9] Q.-N. Lu, S. Chaloupka, L.M. Venanzi, Wuji Huaxue 17 (2001)
2
27.
[10] D. Drew, J.R. Doyle, Inorg. Synth. 28 (1990) 348.