Coordination behavior of phosphino-phosphaferrocenes: Monodentate versus bidentate coordination to divalent palladium

Article abstract of DOI:10.1016/j.ica.2004.05.019

Two novel phosphino-phosphaferrocenes [η⁵-C ₅H₄(CH₂)_nPPh₂] Fe(η⁵-PC₄H₂-2,5-Cy₂) (PP1: n=1; PP2: n=2) have been designed and prepared in order to clarify weak chelate effect in the previously reported (η⁵-C₅H ₄CH₂PPh₂)Fe[η⁵-PC ₄H₂-2,5-((-)-menthyl)₂] (1). ³¹P NMR studies of reactions of PP1 with PdCl₂(cod) (6) revealed that PP1 showed stronger tendency to coordinate to the Pd^II center in bidentate fashion compared to 1. On the other hand, chelate effect in PP2 was negligibly weak and a reaction of PP2 with 6 in a PP2/6 = 2/1 molar ratio gave a complex PdCl₂(PP2)₂ (10) cleanly in which PP2 coordinated to the palladium center at the PPh₂ moiety as a monodentate ligand. X-ray crystal structure studies of chelate complexes PdCl₂(PP1) (7) and PdCl₂(PP2) (9) showed that 9 had deviations from an idealized geometry in the square planar complex which could be attributed to a larger chelate ring of PP2, while PP1 in 7 constructed nearly ideal geometry for the square planar complex. From comparison of the coordination behavior between 1, PP1, and PP2, it is concluded that steric bulk of (-)-menthyl groups in 1 is the main factor of the weak chelate coordination of 1.

Full text of DOI:10.1016/j.ica.2004.05.019

Inorganica Chimica Acta 357 (2004) 3943–3949
www.elsevier.com/locate/ica
Coordination behavior of phosphino-phosphaferrocenes:
monodentate versus bidentate coordination to divalent palladium q
a,
a
b
Masamichi Ogasawara *, Yonghui Ge , Kiyohiko Nakajima ,
a,
*
Tamotsu Takahashi
a
Catalysis Research Center and Graduate School of Pharmaceutical Sciences, Hokkaido University, and SORST,
Japan Science and Technology Corporation (JST), Kita-ku, Sapporo 001-0021, Japan
b
Department of Chemistry, Aichi University of Education, Igaya, Kariya, Aichi, 448-8542, Japan
Received 9 April 2004; accepted 1 May 2004
Available online 8 June 2004
Dedicated to Professor Tobin J. Marks on the occasion of his 60th birthday
Abstract
Two novel phosphino-phosphaferrocenes [g5-C5H4(CH2)nPPh2]Fe(g5-PC4H2-2,5-Cy2) (PP1: n ¼ 1; PP2: n ¼ 2) have been de-
signed and prepared in order to clarify weak chelate effect in the previously reported (g5-C5H4CH2PPh2)Fe[g5-PC4H2-2,5-((–)-
menthyl)2] (1). 31P NMR studies of reactions of PP1 with PdCl2(cod) (6) revealed that PP1 showed stronger tendency to coordinate
to the PdII center in bidentate fashion compared to 1. On the other hand, chelate effect in PP2 was negligibly weak and a reaction of
PP2 with 6 in a PP2/6 ¼ 2/1 molar ratio gave a complex PdCl2(PP2)2 (10) cleanly in which PP2 coordinated to the palladium center
at the PPh2 moiety as a monodentate ligand. X-ray crystal structure studies of chelate complexes PdCl2(PP1) (7) and PdCl2(PP2) (9)
showed that 9 had deviations from an idealized geometry in the square planar complex which could be attributed to a larger chelate
ring of PP2, while PP1 in 7 constructed nearly ideal geometry for the square planar complex.
From comparison of the coordination behavior between 1, PP1, and PP2, it is concluded that steric bulk of (–)-menthyl groups
in 1 is the main factor of the weak chelate coordination of 1.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Phosphaferrocene; Phosphine; Palladium(II); Chelate effect
1. Introduction
ligand was especially important for achieving the high-
level of enantioselectivity. The ligand 1 shows two dis-
tinctive coordination modes depending on stoichiometry
between 1 and PdII. While the ligand 1 forms a chelate
complex in the presence of more than 1 equiv of a PdCl2
precursor ([1]/[PdII] < 1), it has the tendency to dissoci-
ate its chiral phosphaferrocene moiety from the divalent
palladium acting as a monodentate ligand in the pres-
ence of less than 1 equiv of PdCl2 ([1]/[PdII] > 1). The
two coordination modes are reversible and conversion
between the two is spontaneous and clean. With a molar
ratio of 1/PdII ¼ 2/1, cis- and trans-PdCl2(1)2, where 1
was coordinating to the palladium center in the
monodentate fashion at the PPh2 group, are only ob-
servable species and no complex with chelating 1 and no
free ligand 1 were detected. These observations suggest
Recently, we have reported preparation of a novel
chiral phosphino-phosphaferrocene 1 and its application
to palladium-catalyzed asymmetric allylic alkylation [1].
The ligand 1 showed excellent performance in the
asymmetric reaction (up to 99% ee with nearly quanti-
tative yield) under carefully controlled reaction condi-
tions; appropriate molar ratio between Pd and the chiral
q
Supplementary data associated with this article can be found, in the
online version, at doi:10.1016/j.ica.2004.05.019.
* Corresponding authors. Tel.: +81-11-706-9154; fax: +81-11-706-
9150 (M. Ogasawara), Tel.: +81-11-706-9149; fax: +81-11-706-9150 (T.
Takahashi).
0020-1693/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.05.019

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M. Ogasawara et al. / Inorganica Chimica Acta 357 (2004) 3943–3949
that coordination ability between the two donors in 1 is
very different, and thus virtually no chelate effect was
seen in 1.
nyl) [5], [(g6-mesitylene)Fe(g5-C5H4CH2PPh2)]PF6 (4)
[1], 2,5-dicyclohexyl-1-phenylphosphole [6], and
PdCl2(cod) [7] were prepared as reported. All the other
reagents were obtained from commercial sources and
used as received. NMR spectra were recorded on a JEOL
JNM-AL300 spectrometer (1H, 300 MHz; 13C, 75 MHz;
31P, 121 MHz). 1H and 13C chemical shifts are reported in
ppm downfield of internal tetramethylsilane. 31P NMR
chemical shifts are externally referenced to 85% H3PO4.
On the other hand, the coordination behavior of
other known phosphino-phosphaferrocenes, such as 2
[2] and 3 [3] reported by Ganter and Fu, respectively, is
different from that of 1. Although phosphaferrocenes
are known to be weaker r-donors than classical tertiary
phosphines [4], the a-(diphenylphosphinomethyl)phos-
phaferrocenes 2 and 3 showed persistent bidentate
coordination to transition metals. Chelate effect over-
comes the electronic inferiority of the phosphaferrocene
moieties in 2 and 3, however, a similar chelate effect
seems not to be a dominant factor regulating the co-
ordination modes of 1 as described above [1]. The latter
fact may be the limitation of 1 on its application to
metal-catalyzed asymmetric reactions as a chiral ligand.
Because in the monodentate coordination of 1, the
chiral groups are far apart from the Pd center, and thus
the ability of 1 as an asymmetric chiral ligand is
diminished.
2.2. [2-(Diphenylphosphino)ethyl]ferrocene
To a solution of FcCH2CH2MgBr, which was pre-
pared from FcCH2CH2Br (8.14 g, 27.8 mmol) and Mg
(730 mg, 30.0 mmol) in THF (50 mL), was added a THF
(20 mL) solution of Ph2PCl (6.34 g, 28.7 mmol) drop-
wise at 0 °C. After stirring the mixture for 3 h at room
temperature, all the volatiles were evaporated to dryness
under reduced pressure. The residue was extracted with
benzene, then the evaporated extract was purified by
column chromatography over silica gel (elution with
hexane/benzene ¼ 3/1) under nitrogen. Yield: 7.86 g
(19.7 mmol, 71%). This material was >95% pure (by 1H
and 31P NMR analyses) and used for the following step
Based on this background, we have intended to
clarify the origin of the distinctive coordination behav-
ior of 1. Here are the results to this goal.
2. Experimental
without further purification. 1H NMR (CDCl3): d 2.26–
2.30 (m, 2H), 2.42–2.47 (m, 2H), 4.03–4.05 (m, 2H), 4.04
(s, 5H), 4.06–4.07 (m, 2H), 7.32–7.36 (m, 6H), 7.43–7.46
(m, 4H). 13C{1H} NMR (CDCl3): d 25.92 (d, JPC ¼ 19:1
Hz), 29.31 (d, JPC ¼ 11:4 Hz), 67.24 (s), 67.80 (s), 68.49
(s), 89.51 (d, JPC ¼ 15:5 Hz), 128.50 (d, JPC ¼ 6:7
Hz),128.66 (s), 132.74 (d, JPC ¼ 18:1 Hz), 138.54 (d,
JPC ¼ 12:4 Hz). 31P{1H} NMR (CDCl3): d )15.0 (s).
2.1. General procedures
All anaerobic and/or moisture sensitive manipulations
were carried out with standard Schlenk techniques under
predried nitrogen or with glovebox techniques under
prepurified argon. Tetrahydrofuran, Et2O, and 1,4-di-
oxane were distilled from benzophenone-ketyl under ni-
trogen prior to use. Dichloromethane was distilled from
CaH2 under nitrogen prior to use. EtOH was dried over
magnesium ethoxide, distilled, and stored in a glass flask
with a Teflon stopcock under nitrogen. CDCl3 was dried
over P2O5, degased by three freeze–pump–thaw cycles,
and vacuum-transferred. FcCH2CH2Br (Fc ¼ ferroce-
2.3. (g6-Mesitylene) [g5-(2-(diphenylphosphino)ethyl)
cyclopentadienyl]iron(II) hexafluorophosphate (5)
Aluminum chloride (6.40 g, 48.0 mmol), aluminum
powder (324 mg, 12.0 mmol), FcCH2CH2PPh2 (4.23 g,
11.0 mmol), mesitylene (6.30 mL, 45.0 mmol), and water

M. Ogasawara et al. / Inorganica Chimica Acta 357 (2004) 3943–3949
3945
(0.22 mL, 12 mmol) were refluxed in cyclohexane (35 mL)
for 5 h. The mixture was cooled to 0 °C and quenched
with cold water (40 mL). The aqueous layer was sepa-
rated, filtered, and washed with ether. Excess NH4PF6
solution was added and the resulting yellow solid was
collected on a filter and washed with cold water. The solid
was dried, washed with ether, and recrystallized from
CH2Cl2/ether to give the title compound with ca. 33% of
inseparable [(g6-mesitylene)FeCp]PF6. Yield: 4.53 g (ca.
2H), 2.37–2.45 (m, 2H), 3.85 (m, 2H), 4.15 (m, 2H), 4.69
(d, JPH ¼ 4:6 Hz, 2H), 7.26–7.42 (m, 10H). 31P{1H}
NMR (CDCl3): d )75.4 (s), )16.7 (s). Anal. Calc. for
C35H42FeP2: C, 72.42; H, 7.29. Found: C, 72.36; H,
7.27%.
2.6. Dichloro[10-(diphenylphosphinomethyl)-2,5-dicyclo-
hexyl-1-phosphaferrocene]palladium(II) (7)
1
48% of 7 and 24% of [(C6H3Me3)FeCp]PF6). H NMR
An equimolar mixture of PdCl2(cod) and PP1 in di-
chloromethane was stirred for 30 min at room temper-
ature and then all the volatiles were removed under
reduced pressure. The yellow residue was dissolved in a
minimum amount of CH2Cl2. Recrystallization by slow
diffusion of pentane into the CH2Cl2 solution at room
temperature gave the title complex quantitatively as
orange crystals. 1H NMR (CDCl3): d 0.97–1.80 (m,
20H), 2.07 (br d, JPH ¼ 12.1 Hz, 2H), 3.03 (dd, JPH ¼ 9.9
and 5.9 Hz, 2H), 3.31 (br, 2H), 4.38 (br, 2H), 4.85 (d,
JPH ¼ 20.9 Hz, 2H), 7.50–7.55 (m, 6H), 7.83–7.90 (m,
4H). 31P{1H} NMR (CDCl3): d 32.4 (d, JPP ¼ 9.9 Hz,
1P), 66.9 (d, JPP ¼ 9.9 Hz, 1P). Anal. Calc. for
C34H40Cl2FeP2Pd: C, 54.90; H, 5.42. Found: C, 54.69;
H, 5.67%.
(acetone-d6): d 2.32 (br, 13H), 4.83–4.86 (m, 4H), 5.96 (s,
3H), 7.17–7.52 (m, 10H). 31P{1H} NMR (acetone-d6;
)25 °C): d )6.5 (br), 69.7 (m).
2.4.
phosphaferrocene (PP1)
10-(Diphenylphosphinomethyl)-2,5-dicyclohexyl-1-
Lithium metal (230 mg, 33.1 mmol) was added to a
solution of 2,5-dicyclohexyl-1-phenylphosphole (900
mg, 2.77 mmol) in dioxane (40 mL) at room tempera-
ture. The mixture was stirred at 40 °C until disappear-
ance of the phosphole (checked by TLC). The mixture
was added to a solution of 4 (3.10 g, ca. 92% purity, ca.
4.88 mmol) in 1,4-dioxane (75 mL) at 100 °C. The re-
sulting mixture was stirred for 2 h at this temperature.
After cooling, ca. 60 mL of benzene was added and the
solution was filtered through a pad of Celite. The mix-
ture was evaporated to dryness under reduced pressure
and the crude product was chromatographed on silica
gel twice (first elution with hexane/toluene ¼ 4/1, second
elution with hexane/CH2Cl2 ¼ 10/1) under nitrogen.
Yield: 164 mg (0.289 mmol, 10%). 1H NMR (CDCl3): d
1.01–1.27 (m, 10H), 1.63–2.02 (m, 12H), 3.19 (s, 2H),
3.76 (m, 2H), 4.14 (m, 2H), 4.84 (d, JPH ¼ 5:0 Hz, 2H),
7.31–7.42 (m, 10H). 31P{1H} NMR (CDCl3): d )74.7
(s), )12.8 (s). Anal. Calc. for C34H42FeP2: C, 72.09; H,
7.12. Found: C, 72.46; H, 7.41%.
2.7. Dichloro[10-[2-(diphenylphosphino)ethyl]-2,5-dicylo-
hexyl-1-phosphaferrocene]palladium(II) (9)
This complex was prepared in quantitative yield by
1
the analogous method used for the synthesis of 7. H
NMR (CDCl3): d 1.18–1.30 (m, 6H), 1.44–2.13 (m,
16H), 2.71–2.80 (m, 2H), 2.91–3.00 (m, 2H), 3.92 (br,
2H), 4.45 (m, 2H), 5.05 (d, JPH ¼ 19:4 Hz, 2H), 7.47–
7.58 (m, 6H), 7.97 (br, 4H). 31P{1H} NMR (CDCl3): d
20.1 (d, JPP ¼ 12:2 Hz, 1P), 20.8 (d, JPP ¼ 12:2 Hz, 1P).
Anal. Calc. for C35H42Cl2FeP2Pd: C, 55.47; H, 5.59.
Found: C, 55.31; H, 5.68%.
2.5. 10-[2-(Diphenylphosphino)ethyl]-2,5-dicyclohexyl-
1-phosphaferrocene (PP2)
3. Results and discussion
Lithium metal (210 mg, 30.3 mmol) was added to a
solution of 2,5-dicyclohexyl-1-phenylphosphole (800
mg, 2.46 mmol) in dioxane (40 mL) at room tempera-
ture. The mixture was stirred at 40 °C until disappear-
ance of the phosphole (checked by TLC). The mixture
was added to a solution of 5 (2.60 g, ca. 67% purity, ca.
3.28 mmol) in 1,4-dioxane (50 mL) at 100 °C. The re-
sulting mixture was stirred for 2 h at this temperature.
After cooling, ca. 60 mL of benzene was added and the
solution was filtered through a pad of Celite. The mix-
ture was evaporated to dryness under reduced pressure
and the crude product was chromatographed on silica
gel (elution with hexane/toluene ¼ 4/1) under nitrogen.
3.1. Design and preparation of novel phosphino-phospha-
ferrocenes
Two steric factors, which might restrict chelate co-
ordination of 1, were examined; one is steric congestion
at the phosphorus atom in the phosphaferrocene moiety,
the other is strain in the chelate ring. For this purpose,
two novel phosphino-phosphaferrocene ligands PP1
and PP2 were designed and prepared (Scheme 1). The
ligand PP1 has two cyclohexyl groups at the a- and a0-
positions of the phospholyl in place of two (–)-menthyl
groups in 1. The smaller cyclohexyl substituents would
reduce steric congestion at the phospholyl moiety in 1
without changing the electronic properties of it. The
compound PP2 has an additional CH2 unit between the
1
Yield: 791 mg (1.36 mmol, 55%). H NMR (CDCl3): d
0.92–1.21 (m, 10H), 1.55–1.90 (m, 12H), 2.23–2.29 (m,

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M. Ogasawara et al. / Inorganica Chimica Acta 357 (2004) 3943–3949
+
Cy
Fe
P
–
PF6
Fe
n = 1
Cy
Ph2P
Ph2P
n
AlCl3, Al, H2O,
mesitylene
4 (n = 1); 5 (n = 2)
· Li+
Cy
PP1 (10%)
–
P
Fe
+
Cy
Ph2P
Cy
P
+
n
n = 2
n = 1 or 2
–
PF6
Fe
Cy
Fe
Ph2P
PP2 (55%)
Scheme 1.
phosphaferrocenyl and diphenylphosphino groups
compared to 1 as well as PP1, which allow more flexible
coordination of PP2 and may reduce the strain of the
chelate if it existed.
The phosphino-phosphaferrocenes PP1 and PP2
were prepared by an analogous method used for the
synthesis of 1 as outlined in Scheme 1 [8]. Reaction of
lithium 2,5-dicyclohexylphospholide with a cationic
(g6-mesitylene)Fe(II) complex 4 or 5 [9], which were
prepared from the corresponding [x-(diphenylphosph-
ino)alkyl]ferrocene as an inseparable mixture with
[(g6-mesitylene)FeCp]PF6, and subsequent purification
by column chromatography over silica gel gave the
phosphino-phosphaferrocene PP1 (10%) or PP2 (55%).
In the 31P NMR spectra of PP1 or PP2, signals for the
phosphaferrocene moieties are detected in the high field
region (d )74.7 for PP1; d )75.4 for PP2 in CDCl3),
while those of the –PPh2 are seen in the relatively lower
field region (d )12.8 for PP1; d )16.7 for PP2 in
CDCl3). No coupling is detected between the two 31P
signals in PP1 or PP2.
Fig. 1. 31P{1H} NMR spectra of reaction mixture of PP1 and 6 with
varied molar ratios (from bottom to top, PP1/6 ¼ 1/0, 1/1, 2/1, 3/1)
recorded at 121 MHz in CDCl3.
Cl
Cy
3.2. Coordination behavior of the phosphino-phosphafer-
rocene
PP1 (1 eq)
Cl
Pd
P
PdCl2(cod)
– cod
Fe
6
Cy
Ph2P
PP1 (2 eq)
7
Reactions of PP1 with PdCl2(cod) (6) in CDCl3 were
examined in various PP1/6 molar ratios. The coordina-
tion behavior of PP1 was monitored by 31P{1H} NMR
(Fig. 1). Treatment of PP1 with an equimolar of 6 com-
pletely consumed the phosphino-phosphaferrocene to
give a new Pd complex PdCl2(PP1) (7) cleanly, in which
PP1 coordinated in a chelating fashion (Scheme 2). The
two 31P NMR resonances of 7, detected at d 32.4 (–PPh2)
and 66.9 (phosphaferrocene), coupled to each other with
a small coupling constant (2JPP ¼ 9:9 Hz). This indicates
the coordination of PP1 in a cis fashion as expected.
With a molar ratio of PP1/6 ¼ 2/1, a new species,
which was assigned to cis-8, was detected in the
31P NMR spectrum in addition to the complex 7
(Scheme 2). The existence of the chelate complex 7 with
the PP1/6 ¼ 2/1 molar ratio indicated that certain che-
late effects were operative between PP1 and the PdIICl2
– cod
Cl
Cy
Fe
Cy
P
P
Cl
Pd
+
+ free PP1
PdCl2
Fe
Cy
Cy
P
Ph2P
Ph2
2
7
cis- & trans-8
Scheme 2.
fragment, which was different from the coordination
behavior of 1 (vide supra) [1]. The effective chelate effect
of PP1 could be ascribed to the sterically less crowded
phospholyl in PP1 than that in 1. Signals for the free
PP1 were not clearly recognized for this sample at room
temperature, however, very broad resonances were seen
at ca. d 20 and d )75. This could be explained as a rapid

M. Ogasawara et al. / Inorganica Chimica Acta 357 (2004) 3943–3949
3947
phosphine exchange between trans-8 and PP1. The Pd-
PPh2 bond in trans-8 is relatively weaker than that in
cis-8 because of the stronger trans effect of the PPh2
group compared to that of Cl [10]. And thus, the re-
maining free PP1 preferentially exchanges with the co-
ordinating PP1 in trans-8.
With a large excess of PP1 (ca. 3 equiv to 6), cis-8 and
broad signals at d )12.7 and d )74.5 (assignable to the
exchanging free PP1 and trans-8) were observed, but no
7 was detected. All these processes are reversible and
addition of 6 to the mixture of cis- and trans-8 regen-
erates 7 quantitatively.
The reactions between PP2 and 6 are much simple
(Fig. 2 and Scheme 3). The phosphino-phosphaferrocene
PP2 forms a chelate complex 9 with molar ratios of PP2/
6 6 1. In the presence of more than equimolar of PP2 to
6, the phosphaferrocene moiety in 9 cleanly replaced with
Fig. 3. ORTEP of PdCl2(PP1) ꢀ CH2Cl2 (7 ꢀ CH2Cl2) with 50% thermal
ellipsoids. All hydrogen atoms and co-crystallized CH2Cl2 are omitted
for clarity.
the Ph2P-part of the extra PP2 to form a bis(phosphino-
phosphaferrocene) complex 10 in which PP2 coordinates
as a monodentate ligand. While the chelate complex 9
was an only species detected in the 31P NMR spectrum
with a PP2/6 ¼ 1/1 molar ratio, the complex 10 with the
monodentate PP2 was a sole detectable product from the
reaction of PP2 and 6 with a 2:1 molar ratio. When PP2
coordinates to a PdCl2 fragment, chelate effect is negli-
gibly weak. This is in clear contrast to the coordination
behavior of PP1 mentioned above. Note that the com-
1
plex 10 was yielded as a single isomer.
Fig. 2. 31P{1H} NMR spectra of reaction mixture of PP2 and 6 with
varied molar ratios (from bottom to top, PP2/6 ¼ 1/0, 1/1, 2/1, 3/1)
recorded at 121 MHz in CDCl3.
3.3. X-ray crystal structures of dichloropalladium com-
plexes
The complex 7 was readily and quantitatively obtained
from an equimolar mixture of 6 and PP1 in dichlorom-
ethane. Recrystallization from CH2Cl2–pentane gave
prismatic crystals and the structure was clarified by X-ray
single-crystal structure determination (Fig. 3). Selected
crystallographic data are summarized in Table 1 and
selected bond lengths and angles are listed in Table 2. It
reveals that the crystal contains a solvent molecule
(CH2Cl2) per formula unit (the co-crystallized dichlo-
romethane molecule is omitted from the ORTEP drawing
for clarity), though no interaction is observed between
the complex and the co-crystallized dichloromethane. A
Cl
Cy
PP2 (1 eq)
Cl
Pd
P
PdCl (cod)
2
– cod
Fe
6
Cy
Ph P
2
PP2 (2 eq)
9
– cod
6
PP2 (1 eq)
– cod – cod
Cy
P
Ph
2
P
Fe
Cy
PdCl
2
2
1
Although a structure of the complex 10 was uncertain, it is
tentatively assigned as a cis-complex which is electronically more stable
than the trans-counterpart.
10
Scheme 3.

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M. Ogasawara et al. / Inorganica Chimica Acta 357 (2004) 3943–3949
Table 1
Crystallographic data for complexes 7 and 9
7
9
Formula
C
34H40Cl2FeP2Pd ꢀ
C35H42Cl2FeP2Pd
CH2Cl2
828.72
Formula weight
Color, habit
757.82
orange, prismatic
0.25 ꢁ 0.20 ꢁ 0.10
monoclinic
P1=a (#14)
14.0246(7)
18.7392(9)
14.2839(9)
105.668(2)
3614.5(3)
4
brown, prismatic
0.40 ꢁ 0.13 ꢁ 0.13
monoclinic
P1=a (#14)
14.4360(4)
12.9326(4)
19.0257(5)
110.382(1)
3329.6(2)
4
Crystal size (mm)
Crystal system
Space group
ꢀ
a (A)
ꢀ
b (A)
ꢀ
c (A)
b (°)
V (A )
3
ꢀ
Z
Dcalc (g cmꢂ3
)
1.523
1.306
1.512
1.256
l (cmꢂ1
Radiation type
)
Mo Ka
0.7107
Mo Ka
0.7107
ꢀ
Wavelength (A)
T (K)
298.2
55
8099
298.2
55
7626
2hmax (°)
Number of reflections
collected
Unique
Parameters
4971
388
F 2
0.0440
0.0547
1.249
5799
406
F 2
0.0416
0.0578
1.577
Fig. 4. ORTEP of PdCl2(PP2) (9) with 50% thermal ellipsoids. All
hydrogen atoms are omitted for clarity.
Refinements on
R½F 2 > 2:0rðF 2Þꢃ
Rw½F 2 > 2:0rðF 2Þꢃ
(Fig. 4, Tables 1 and 3). Unlike the complex 7, the
crystals of 9 have no co-crystallized solvent. Some dis-
orders are detected in both of the cyclohexyl groups.
Although small distortion of the bond angles around the
palladium center is observed in 9, Pd(1), P(1), P(2),
Cl(1), and Cl(2) are located on the same plane and sum
of the angles between the adjacent coordination sites is
360.1(2)°. The P(1)–Pd(1)–P(2) bite angle in the complex
9 is significantly larger than that in 7, being 96.59(4)°.
The weak chelate effect of PP2 could be attributed to the
large bite angle of the chelating ligand.
Goodness-of-fitꢂ3
ꢀ
Residual q (e A
)
+0.91, )0.67
+0.69, )0.70
Table 2
ꢀ
Selected bond distances (A) and angles (°) for 7
Bond distances
Pd(1)–Cl(1)
Pd(1)–Cl(2)
Pd(1)–P(1)
Pd(1)–P(2)
2.358(2)
2.322(2)
2.226(2)
2.269(1)
C(1)–C(10)
P(2)–C(10)
Fe(1)–P(1)
Fe(1)–C(1)
1.502(7)
1.843(5)
2.214(2)
2.048(5)
Bond angles
Cl(1)–Pd(1)–Cl(2) 91.83(6)
P(1)–Fe(1)–C(1)
Pd(1)–P(1)–Fe(1)
Fe(1)–C(1)–C(10)
P(2)–C(10)–C(1)
Pd(1)–P(2)–C(10)
100.9(2)
132.82(7)
130.6(4)
121.7(3)
119.2(2)
3.4. Comparison between 1, PP1, and PP2
Cl(1)–Pd(1)–P(1)
Cl(1)–Pd(1)–P(2)
Cl(2)–Pd(1)–P(1)
Cl(2)–Pd(1)–P(2)
P(1)–Pd(1)–P(2)
85.48(6)
176.44(6)
176.45(6)
89.20(5)
93.35(5)
Comparison of the overall coordination behavior of
PP1 and PP2 indicates that elongation of the bridging
unit between C5H4 and PPh2 in the phosphino-phos-
solvent-free sample was obtained by prolonged evacua-
tion under high-vacuum at 50 °C. The angle of P(1)–
Pd(1)–P(2) is 93.35(5)°, while that of Cl(1)–Pd(1)–Cl(2) is
91.83(6)°. The bite angle of the coordinating PP1 in 7 was
unremarkable: it is in the typical range for dichloropal-
ladium(II) complexes bearing chelating bisphosphine li-
gands [11]. The geometry around the Pd center is slightly
distorted square planar, the sum of four angles at Pd(1)
involving Cl(1), Cl(2), P(1), and P(2) being 359.9(2)°. The
Pd–P distances and the Pd–Cl distances are in the typical
range for PdCl2(P–P) complexes.
Table 3
ꢀ
Selected bond distances (A) and angles (°) for 9
Bond distances
Pd(1)–Cl(1)
Pd(1)–Cl(2)
Pd(1)–P(1)
Pd(1)–P(2)
P(2)–C(11)
2.369(1)
2.328(1)
2.223(1)
2.261(1)
1.833(4)
C(1)–C(10)
C(10)–C(11)
Fe(1)–P(1)
Fe(1)–C(1)
1.496(7)
1.556(6)
2.215(1)
2.036(4)
Bond angles
Cl(1)–Pd(1)–Cl(2) 92.83(5)
P(1)–Fe(1)–C(1)
Pd(1)–P(1)–Fe(1)
106.4(1)
148.95(5)
Cl(1)–Pd(1)–P(1)
Cl(1)–Pd(1)–P(2)
Cl(2)–Pd(1)–P(1)
Cl(2)–Pd(1)–P(2)
P(1)–Pd(1)–P(2)
83.02(4)
176.58(4)
175.09(5)
87.70(5)
96.59(4)
Fe(1)–C(1)–C(10) 125.6(3)
C(1)–C(10)–C(11) 115.0(4)
P(2)–C(11)–C(10) 117.8(3)
An analogous complex with PP2, PdCl2(PP2) (9) was
prepared from 6 in a similar manner and its solid state
structure was determined by X-ray crystallography
Pd(1)–P(2)–C(11)
118.8(1)

M. Ogasawara et al. / Inorganica Chimica Acta 357 (2004) 3943–3949
3949
phaferrocenes diminishes their chelation ability. As
shown in the crystal structures, the size of the chelate
ring (i.e., the P–Pd–P angle) in 7 is nearly ideal for the
square planar PdII center, while the ethylene unit
bridging the PPh2 and the phosphaferrocene in PP2
causes certain deviations from an idealized geometry in
the square planar complex 9. The latter may be the
main reason for the weaker chelation ability of PP2.
Because of the structural similarity between 1 and PP1,
a possible chelate ring strain in 1 could be excluded as
a main factor for the weak chelate effect in 1.
Difference of the coordination behavior between 1
and PP1 is distinctive, although their structural differ-
ences are very minor. Because the electronic effects from
(–)-menthyl groups in 1 and from cyclohexyl groups in
PP1 are assumed to be nearly identical, the difference of
their complexation behavior to PdII could be ascribed to
the difference of their steric characteristics. In other
words, the bulky (–)-menthyl groups in 1 cause steric
congestion at the phosphorus atom in the phospholyl
group. This weakens the coordination ability of the
phosphaferrocene moiety in 1, and thus chelate effect in
the ligand 1 becomes weaker.
‘‘Reaction Control of Dynamic Complexes’’) from the
Ministry of Education, Culture, Sports, Science and
Technology, Japan.
References
[1] (a) M. Ogasawara, K. Yoshida, T. Hayashi, Organometallics 20
(2001) 3913;
(b) M. Ogasawara, K. Yoshida, T. Hayashi, Organometallics 20
(2001) 1014.
[2] (a) C. Ganter, L. Brassat, B. Ganter, Chem. Ber./Recueil 130
(1997) 1771;
(b) L. Brassa, B. Ganter, C. Ganter, Chem. Eur. J. 4 (1998)
1163.
[3] (a) S. Qiao, G.C. Fu, J. Org. Chem. 63 (1998) 4168;
(b) K. Tanaka, S. Qiao, M. Tobisu, M.M.-C. Lo, G.C. Fu, J. Am.
Chem. Soc. 122 (2000) 9870;
(c) K. Tanaka, G.C. Fu, J. Org. Chem. 66 (2001) 8177.
[4] (a) J. Fischer, A. Mitschler, L. Ricard, F. Mathey, J. Chem. Soc.,
Dalton Trans. (1980) 2522;
(b) F. Mathey, J. Fischer, J.H. Nelson, Struct. Bonding 55 (1983)
153;
(c) F. Mathey, J. Organomet. Chem. 400 (1990) 149;
(d) F. Mathey, Coord. Chem. Rev. 137 (1994) 1.
[5] C.-F. Shu, F.C. Anson, J. Phys. Chem. 94 (1990) 8345.
[6] M. Ogasawara, T. Nagano, K. Yoshida, T. Hayashi, Organomet-
allics 21 (2002) 3062.
From this study, it is concluded that steric bulk of (–)-
menthyl groups in 1 is the main factor of the weak
chelate coordination of 1.
[7] D. Drew, J.R. Doyle, Inorg. Synth. 13 (1972) 52.
[8] R.M.G. Robert, A.S. Wells, Inorg. Chim. Acta 112 (1986)
171.
[9] D. Astruc, Tetrahedron 39 (1983) 4027.
[10] J.P. Collman, L.S. Hegedus, J.R. Norton, R.G. Finke, Principles
and Applications of Organotransition Metal Chemistry, Univer-
sity Science Books, Mill Valley, CA, 1987.
4. Supplementary material
Complete crystallographic data for 7 and 9 in CIF
format.
[11] (a) W.L. Steffen, G.J. Palenik, Inorg. Chem. 15 (1976) 2432;
(b) V.D. Makhaev, Z.M. Dzhabieva, S.V. Konovalikhin, O.A.
D’yachenko, G.P. Belov, Russ. J. Coord. Chem. 22 (1996) 563;
(c) T. Hayashi, M. Konishi, Y. Kobori, M. Kumada, T. Higuchi,
K. Hirotsu, J. Am. Chem. Soc. 106 (1984) 158;
(d) F. Ozawa, A. Kubo, Y. Matsumoto, T. Hayashi, Organomet-
allics 12 (1993) 4188;
Acknowledgements
This work was partially supported by a Grant-in-Aid
for Scientific Research on Priority Areas (No. 15036202,
(e) M. Ogasawara, K. Yoshida, T. Hayashi, Organometallics 19
(2000) 1567.