Stereoselective synthesis and coordination behavior of phosphorus-bridged [1.1]ferrocenophanes

Article abstract of DOI:10.1021/om050809q

Chlorination with HCl of a mixture of syn- and anti-P(NEt ₂)-bridged [1.1]ferrocenophane 3 derived from [Fe{(η⁵- C₅H₄)PCl(NEt₂)}₂] 2 accompanied facile anti-to-syn conversion to give the syn isomer of PCl-bridged [1.1]ferrocenophane syn-4 selectively in 90% yield, and treatment of syn-4 with PhLi, Me₃-SiCH₂Li, or p-TolMgBr afforded the corresponding diarylated or dialkylated compounds syn-5 to syn-7. Reactions of syn-5 with [PdCl₂(COD)], [PdMe₂(TMEDA)], and NiCl₂ gave respectively four-coordinate [PdCl₂(syn-5)], [PdMe ₂(syn-5)], and [NiCl₂(syn-5)] complexes, the former two of which had a distorted square-planar structure with the latter adopting a tetrahedral geometry. In addition, syn-5 acted as a bridging ligand toward piano-stool Mn carbonyl complex fragments to give a novel dinuclear complex, [{Cp′Mn-(CO)₂(μ-syn-5)] (Cp′ = C₅H ₄CH₃).

Full text of DOI:10.1021/om050809q

882
Organometallics 2006, 25, 882-886
Stereoselective Synthesis and Coordination Behavior of
Phosphorus-Bridged [1.1]Ferrocenophanes
Yuki Imamura, Tsutomu Mizuta,* and Katsuhiko Miyoshi
Department of Chemistry, Graduate School of Science, Hiroshima UniVersity,
Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526, Japan
ReceiVed September 19, 2005
Chlorination with HCl of a mixture of syn- and anti-P(NEt2)-bridged [1.1]ferrocenophane 3 derived
from [Fe{(η5-C5H4)PCl(NEt2)}2] 2 accompanied facile anti-to-syn conversion to give the syn isomer of
PCl-bridged [1.1]ferrocenophane syn-4 selectively in 90% yield, and treatment of syn-4 with PhLi, Me3-
SiCH2Li, or p-TolMgBr afforded the corresponding diarylated or dialkylated compounds syn-5 to syn-7.
Reactions of syn-5 with [PdCl2(COD)], [PdMe2(TMEDA)], and NiCl2 gave respectively four-coordinate
[PdCl2(syn-5)], [PdMe2(syn-5)], and [NiCl2(syn-5)] complexes, the former two of which had a distorted
square-planar structure with the latter adopting a tetrahedral geometry. In addition, syn-5 acted as a bridging
ligand toward piano-stool Mn carbonyl complex fragments to give a novel dinuclear complex, [{Cp′Mn-
(CO)2}2(µ-syn-5)] (Cp′ ) C5H4CH3).
Introduction
Diphosphines have been widely used as a common chelate
ligand in transition-metal complexes. Most of them reported so
far are those whose two P atoms are linked with a single chain.
On the other hand, such double-chained diphosphines as shown
in Figure 1 are considerably limited in number,1-3 although they
are expected to have some significant structural effects on the
metal complex formation. For example, they may coordinate
to a transition metal more tightly through the double chelate
effect. In addition, each P atom has one substituent R forced to
reside at the front side of the metal center (Figure 1), and
therefore, elaborate structural modulations are possible around
the metal center with various R groups. Furthermore, the chelate
chains, if they carry bulky substituent(s), will act as protecting
groups against the axial coordination to the metal.
Figure 1. Schematic representation of a double-chained diphos-
phine and its metal complex fragment.
Chart 1
Several metal complexes with double-chained diphosphines
have been synthesized so far and characterized by X-ray
analysis.1,4 However, such diphosphines are usually obtained
as a mixture of two stereoisomers (syn- and anti-forms, see Chart
1). It is noteworthy in this respect that stereoselective synthetic
methods have been developed for 1,n-diphosphacycloalkanes
by Alder et al.3 and for 1,5,3,7-diazadiphosphacyclooctane
derivatives by Karasik et al.1a-c
We reported previously that P-bridged [1.1]ferrocenophane,
one of the double-chained diphosphines, was obtained as a
byproduct in photoinduced oligomerization of P-bridged [1]-
ferrocenophane.5 It has two P atoms linked doubly with two
1,1′-ferrocenediyl moieties, and its anti isomer isomerizes upon
heating to the syn isomer, useful as a bidentate chelate. In this
paper, we report an alternative and stereoselective synthetic route
designed rationally to the double-chained P-bridged [1.1]-
ferrocenophanes having various substituents on the P atoms,
and their coordination behavior to metal fragments is also
reported.
* To whom correspondence should be addressed. Fax: +81-82-424-
0729. E-mail: mizuta@sci.hiroshima-u.ac.jp.
(1) (a) Karasik, A. A.; Bobrov, S. V.; Nikonov, G. N.; Pisarevskii, A.
P.; Litvinov, I. A.; Dokuchaev, A. S.; Struchkov, Y. S.; Enikeev, K. M.
Russ. J. Coord. Chem. 1995, 21, 551-561. (b) Karasik, A. A.; Krashilina,
A. V.; Gubaidullin, A. T.; Litvinov, I. A.; Cherkasov, V. K.; Sinyashin, O.
G.; Abakumov, G. A. Russ. Chem. Bull. 2000, 49, 1782-1788. (c) Karasik,
A. A.; Naumov, R. N.; Sinyashin, O. G.; Belov, G. P.; Novikova, H. V.;
Lo¨nnecke, P.; Hay-Hawkins, E. J. Chem. Soc., Dalton Trans. 2003, 2209-
2214. (d) Kane, J. C.; Wong, E. H.; Yap, G. P.; Rheingold, A. L. Polyhedron
1999, 18, 1183-1188.
(2) (a) Brooks, P. J.; Gallagher, M. J.; Sarroff, A.; Bowyer, M.
Phosphorus, Sulfur Silicon 1989, 44, 235-247. (b) Toto, S. D.; Arbuckle,
B. W.; Bharadwaj, P. K.; Doi, J. T.; Musker, W. K. Phosphorus, Sulfur
Silicon 1991, 56, 27-38.
(3) Alder, R. W.; Ganter, C.; Gil, M.; Gleiter, R.; Harris, C. J.; Harris,
S. E.; Lange, H.; Orpen, A. G.; Taylor, P. N. J. Chem. Soc., Perkin Trans.
1 1998, 1643-1655.
(4) (a) Cucciolito, M. E.; Felice, V. D.; Orabona, I.; Panunzi, A.; Ruffo,
F. Inorg. Chim. Acta 2003, 343, 209-216. (b) Arbuckle, B. W.; Musker,
W. K. Polyhedron 1991, 10, 415-419.
Results and Discussion
Synthesis and Characterization of P(NEt2)-Bridged [1.1]-
Ferrocenophane, anti- and syn-3. The synthetic route to
P-bridged [1.1]ferrocenophanes is shown in Schemes 1 and 2.
It is sensible to introduce an NEt2 group on each P atom in
advance, since the P-NEt2 group is readily converted to the
(5) (a) Mizuta, T.; Imamura, Y.; Miyoshi, K.; Yorimitsu, H.; Oshima,
K. Organometallics 2005, 24, 990-996. (b) Mizuta, T.; Onishi, M.; Miyoshi,
K. Organometallics 2000, 19, 5005-5009. (c) Mizuta, T.; Imamura, Y.;
Miyoshi, K. J. Am. Chem. Soc. 2003, 125, 2068-2069.
10.1021/om050809q CCC: $33.50 © 2006 American Chemical Society
Publication on Web 01/07/2006

Phosphorus-Bridged [1.1]Ferrocenophanes
Organometallics, Vol. 25, No. 4, 2006 883
Scheme 1
Crystal Structure of anti-3. The molecular structure of anti-3
is shown in Figure 2, where two ferrocenediyl units are linked
through two P(NEt2) bridging groups to form a [1.1]ferro-
cenophane framework with an anti conformation. Each half of
the molecule is related by an inversion center. The twist angle,
i.e., the dihedral angle between the two C5H4 planes connected
to the same P atom, is 2.43(10)°, and so the two C5H4 planes
are nearly coplanar. Similar small twist angles are observed for
most of the anti isomers of heteroatom-bridged [1.1]ferro-
cenophanes known to date,7 indicating that coplanarity of the
two C5H4 rings is an inherent property of the anti isomers. The
bridge angle of the two ferrocene units, i.e., the angle of C(1)-
P(1)-C(6*), is 106.04(9)°, close to a tetrahedral angle. The
P‚‚‚P distance of 4.88 Å is too large for the through-space P-P
coupling to emerge.
Scheme 2
Synthesis and Characterization of PR-Bridged [1.1]Fer-
rocenophane. The reaction of a mixture of anti-3 and syn-3
with HCl in THF gave PCl-bridged [1.1]ferrocenophane 4 in
P-Cl group, with which various R groups are in turn introduced
on the P atoms. The starting material chosen is thus the ferrocene
derivative 1, having a P(NEt2)2 group on each C5H4 ring. The
reaction of 1 with PCl3 yielded the dichlorinated compound 2
as a mixture of diastereomers. Compound 2 thus obtained was
then allowed to react with NaCp to connect each P atom with
a ferrocenediyl fragment, followed by deprotonation with
n-BuLi, and then complexation with FeCl2 was performed to
obtain 3. In the 31P{1H} NMR spectrum of 3, two signals were
observed at 43.6 and 41.9 ppm in an intensity ratio of ca. 5:4,
indicating the presence of two types of phosphorus compounds.
Repeated recrystallization yielded a small amount of the pure
major product, X-ray analysis of which revealed it to be P(NEt2)-
bridged [1.1]ferrocenophane with an anti conformation, anti-3
(Figure 2). Comparison of the NMR data indicates that the minor
product is a syn isomer of 3 (syn-3). Since isolation of syn-3
from the mixture was unsuccessful, it was characterized finally
on the basis of spectroscopic data of pure syn-3 prepared
separately from syn-4 in Scheme 2 (vide infra). A 13C{1H} NMR
spectrum of syn-3 showed a characteristic virtual coupling due
to a through-space coupling of the two P centers in close
proximity;3,6 four of the five C5H4-carbon signals each appeared
as a virtual triplet and the remaining one a singlet, whereas
anti-3 showed three doublets, one singlet, and one triplet due
to its five C5H4 carbons.
1
90% yield (Scheme 2). The H NMR spectrum of 4 showed
only four signals assignable to the C5H4 ring protons. In the
13C{1H} NMR spectrum, the signal of the ipso-C5H4 carbon
atoms appeared as a virtual triplet with J ) 17 Hz, indicating
that the syn isomer of 4 (syn-4) was obtained selectively with
accompanying anti-to-syn conversion. In the case of 5 (Scheme
2) reported previously, the anti isomer was also converted upon
heating to the more stable syn isomer,5a while the anti-to-syn
conversion of 4 took place readily at room temperature. Humbel
et al. reported that the presence of a catalytic amount of HCl
brings about a facile inversion of R1R2PCl at room temperature.8
Therefore, it is highly plausible that HCl not only substitutes
the NEt2 group with the Cl atom but also catalyzes the anti-
to-syn conversion, to give syn-4 exclusively.
The chloride derivative syn-4 is a useful precursor of
P-bridged [1.1]ferrocenophanes bearing various substituents on
the P atoms. For example, reactions of syn-4 with HNEt2, PhLi,
Me3SiCH2Li, or p-TolMgBr yielded the expected diphosphines
syn-3, syn-5, syn-6, and syn-7, respectively (Scheme 2). Their
characterization was achieved by multinuclear NMR spectros-
copy. In particular, their conformations were readily determined
by 13C{1H} NMR spectroscopy. For syn-6, for example, the
signal of the ipso-C5H4 carbon atoms was observed as a virtual
triplet with J ) 7 Hz, confirming its syn conformation. Both
syn-55a and syn-7 behaved similarly; so did syn-3 and syn-4 as
mentioned earlier.
Coordination Behavior of Phosphorus-Bridged [1.1]Fer-
rocenophane. The syn isomer of P-bridged [1.1]ferrocenophane
is a double-chained diphosphine that has substituents R forced
to reside in the coordination plane in Figure 1, when it binds as
a bidentate ligand to a metal M. This structural characteristic is
expected to bring about a peculiar steric effect on the metal
complex formation with it. Then, reactions of some metal
complexes were examined with PPh-bridged [1.1]ferrocenophane
syn-5 as a prototype, whose molecular structure has been already
established.5a
Pd Complexes. The reaction of syn-5 with [PdCl2(COD)]9
or [PdMe2(TMEDA)]9 at room temperature gave [PdCl2(syn-
5)] (8) or [PdMe2(syn-5)] (9) (Scheme 3), both of which were
characterized by X-ray analysis as shown in Figure 3. The
selected bond distances and angles are listed in Table 1.
Figure 2. ORTEP drawing of anti-3 with 50% thermal ellipsoids.
Hydrogen atoms are omitted for clarity. Selected bond distances
(Å) and angles (deg): P-N 1.694(2), P-C(1) 1.814(2), P-C(6*)
1.831(2), N-P-C(1) 100.75(10), N-P-C(6*) 101.53(9), C(1)-
P-C(6*) 106.04(9). Symmetry transformation used to generate
equivalent (asterisked) atoms: (-x + 1.5, -y + 0.5, -z).
(6) (a) Kilian, P.; Slawin, A. M. Z.; Woollins, J. D. Chem. Eur. J. 2003,
9, 215-222. (b) Karac¸ar, A.; Freytag, M.; Jones, P. G.; Bartsch, R.;
Schmutzler, R. Z. Anorg. Allg. Chem. 2001, 627, 1571-1581.
(7) Ref 5a and references therein.
(8) Humbel, S.; Bertrand, C.; Darcel, C.; Bauduin, C.; Juge´, S. Inorg.
Chem. 2003, 42, 420-427.

884 Organometallics, Vol. 25, No. 4, 2006
Imamura et al.
Table 1. Selected Bond Distances (Å) and Angles (deg) for
8, 9, and 10
8
9a
10 Ni(1)
10b Ni(2)
M-P(1)
M-P(2)
M-X(1)
M-X(2)
2.2886(9)
2.3016(9)
2.331(1)
2.328(1)
2.3518(5)
2.3222(5)
2.185(2)
2.115(2)
2.3133(13)
2.3126(13)
2.2315(14)
2.2098(15)
2.2782(13)
2.3016(13)
2.2087(16)
2.2167(14)
P(1)-M-P(2)
X(1)-M-X(2)
P(1)-M-X(1)
P(1)-M-X(2)
P(2)-M-X(1)
P(2)-M-X(2)
92.29(3)
88.73(5)
88.25(4)
170.28(5)
173.19(5)
91.80(4)
91.77(2)
83.66(9)
91.91(5)
175.46(7)
166.61(5)
92.76(7)
93.85(4)
93.20(5)
119.52(6)
103.15(5)
115.12(5)
119.47(6)
103.26(5)
119.55(6)
106.28(6)
111.39(6)
116.56(6)
106.73(6)
twist angle
27.2(2)
25.9(2)
22.0(1)
23.2(1)
9.23(16)
9.61(16)
18.89(21)
20.19(22)
a X(1) ) C(33), X(2) ) C(34). b P(1) ) P(3), P(2) ) P(4), X(1) ) Cl(3),
X(2) ) Cl(4).
Figure 4. ORTEP drawings of two independent molecules of 10
with 50% thermal ellipsoids. Hydrogen atoms are omitted for clarity.
Figure 3. ORTEP drawings of 8 (top) and 9 (bottom) with 50%
thermal ellipsoids. Hydrogen atoms are omitted for clarity.
less bulky dppp9 complex is square-planar with the suitable
P-Ni-P angle of 91.77(4)°.11 Thus, it is of interest which
geometry is adopted by the present double-chained diphosphine
ligand upon coordination to a nickel(II) fragment.
Scheme 3
The reaction of syn-5 with NiCl2 gave the green paramagnetic
complex 10, which was characterized by X-ray analysis as
shown in Figure 4, where two independent molecules are
depicted. The selected bond distances and angles are listed in
Table 1. Both molecules have a considerably distorted tetra-
hedral geometry with P-Ni-P bite angles of 93.85(4)° and
93.20(5)°, which are comparable to those of the square-planar
complexes 8 and 9 (vide supra), but are substantially smaller
than an ideal tetrahedral angle. The Cl-Ni-Cl bite angles of
119.52(6)° and 119.55(6)° are on the contrary fairly larger than
a tetrahedral angle. It has been established that [Ni(P-P)X2]
complexes having a relatively short single-chained diphosphine,
such as dppm,9 dppe,9 and dppp, adopt a square-planar geometry
with P-Ni-P bite angles close to or smaller than 90°,11 whereas
those having a longer single-chained diphosphine, such as dppb9
and dppf, adopt a tetrahedral geometry with larger bite angles.10
Taking the small P-Ni-P bite angle of 10 into account, some
additional but opposing effect must be in action to make
complex 10 exceptionally tetrahedral. If 10 adopted a square-
planar geometry as expected from its narrow P-Ni-P bite
angle, the two Ph groups would have to be located in the
Complexes 8 and 9 both have a distorted square-planar structure
around a Pd center; 8 has a dihedral angle of 11.3° between the
PdP2 and PdCl2 planes, and 9 has one of the Me groups deviating
by 0.49 Å from a least-squares plane of PdP2C, leading to the
corresponding dihedral angle of 13.0°. In addition, the distance
(2.185(2) Å) from the Pd center to the deviating Me group (C33)
is considerably larger than that (2.115(2) Å) to the other Me
group (C34) in 9. These distortions are no doubt ascribed to
the steric repulsion between the Ph groups and Cl or Me ligands.
Ni Complex. Dichlorodiphosphine nickel(II) complexes are
known to adopt both tetrahedral and square-planar geometries.
For example, the dppf9 complex adopts a tetrahedral structure
with the suitable P-Ni-P angle of 105.0(1)°,10 whereas the
(9) Ligand abbreviations: COD ) cycloocta-1,5-diene, TMEDA )
N,N,N′,N′-tetramethylethylenediamine, dppf ) 1,1′-bis(diphenylphosphino)-
ferrocene, dppp ) 1,3-bis(diphenylphosphino)propane, dppm ) 1,1-bis-
(diphenylphosphino)methane, dppe ) 1,2-bis(diphenylphosphino)ethane, and
dppb ) 1,4-bis(diphenylphosphino)butane.
(10) Casellato, U.; Ajo´, D.; Valle, G.; Corain, B.; Longato, B.; Graziani,
R. J. Cryst. Spectrosc. Res. 1988, 18, 583-590.
(11) Bomfim, J. A. S.; de Souza, F. P.; Filgueiras, C. A. L.; de Sousa,
A. G.; Gambardella, M. T. P. Polyhedron 2003, 22, 1567-1573.

Phosphorus-Bridged [1.1]Ferrocenophanes
Organometallics, Vol. 25, No. 4, 2006 885
sphere. The compounds [Fe{(η5-C5H4)P(NEt2)2}2] 1,15 syn-5,5a and
CpNa16 were prepared by literature procedures.
NMR spectra were recorded on a JEOL LA-300 spectrometer.
1H and 13C data were referenced to SiMe4, and 31P NMR data to
85% H3PO4. Photolysis was carried out with Pyrex-glass-filtered
emission from a 400 W mercury arc lamp (Riko-Kagaku Sangyo
UVL-400P). The emission lines in nm used and their relative
intensities (in parentheses) were as follows: 577.0 (69), 546.1 (82),
435.8 (69), 404.7 (42), 365.0 (100), 334.1 (7), 312.6 (38), and 302.2
(9).
Characterization data for the new compounds prepared in this
paper are given in the Supporting Information, and only 31P{1H}
NMR data are provided below. Standard procedures17-20 were
applied to synthesize 8-11; complete experimental details are also
given in the Supporting Information.
Synthesis of 1,1′-Bis(diethylaminochlorophosphino)ferrocene,
2. To a solution of 1 (20.31 g, 38.0 mmol) in hexane (100 mL)
was added PCl3 (6.7 mL, 76.8 mmol) dropwise. After the solution
was stirred overnight, the solvent was removed and the slurry was
washed with cold hexane to remove phosphorus byproducts. The
residue was extracted with hot hexane and dried in vacuo to give
2 as a yellow powder (12.57 g, 72%). 31P{1H} NMR (121.5 MHz,
C6D6): δ 136.5 (s), 136.8 (s).
Figure 5. ORTEP drawing of 11 with 50% thermal ellipsoids.
Hydrogen atoms are omitted for clarity. Selected bond distances
(Å) and angles (deg): Mn(1)-P(1) 2.2298(5), Mn(2)-P(2)
2.2328(5), P(1)-C(1) 1.812(2), P(1)-C(11) 1.819(2), P(2)-C(6)
1.817(2), P(2)-C(16) 1.830(2), P(1)-Mn(1)-C(39) 89.95(6),
P(1)-Mn(1)-C(40) 95.47(7), P(2)-Mn(2)-C(47) 92.36(6), P(2)-
Mn(2)-C(48) 92.07(7), Mn(1)-P(1)-C(1) 118.85(6), Mn(1)-
P(1)-C(11) 108.18(6), C(1)-P(1)-C(11) 109.54(8), Mn(2)-P(2)-
C(6) 108.22(6), Mn(2)-P(2)-C(16) 118.08(6), C(6)-P(2)-C(16)
111.14(8), twist angle 72.44(9), 70.41(9).
Synthesis of exo,exo-1,12-Bis(diethylamino)-1,12-diphospha-
[1.1]ferrocenophane, anti-3 and syn-3. To a suspension of 2 (8.32
g, 18.0 mmol) in THF (40 mL) was added dropwise 40 mL of a
THF solution of CpNa (3.19 g, 36.2 mmol) at -50 °C. After stirring
for 30 min, the solution became homogeneous, and then n-BuLi
(2.71 M hexane solution, 13.3 mL, 36.0 mmol) was added dropwise.
The mixture was stirred for 30 min and then added dropwise to a
suspension of FeCl2 (2.40 g, 18.9 mmol) in THF (80 mL) at -50
°C. After stirring overnight, the solvent was removed in vacuo and
the residue was then extracted with hot hexane. The solvent was
removed in vacuo and then washed with cold hexane to give 3
(anti/syn ) 5/4) (4.95 g, 48%) as a yellow powder. Recrystallization
from hexane repeated several times gave a small amount of pure
anti-3. 31P{1H} NMR (121.5 MHz, C6D6): δ 43.8 (s).
Isolation of pure syn-3 was achieved by the reaction of syn-4
prepared as below with 4 equiv of HNEt2 in a MeCN/THF mixture
as follows. To a solution of syn-4 (573 mg, 1.14 mmol) in a mixture
of THF (15 mL) and MeCN (10 mL) was added HNEt2 (0.50 mL,
4.83 mmol) at room temperature. After the reaction mixture was
stirred for 1 h, all volatile components were removed. Then, the
residue was extracted with hexane and dried in vacuo to give syn-3
as a yellow powder (461 mg, 70%). 31P{1H} NMR (121.5 MHz,
C6D6): δ 41.7 (s).
Synthesis of exo,exo,syn-1,12-Dichloro-1,12-diphospha[1.1]-
ferrocenophane, syn-4. To a solution of 3 (45 mg, 0.078 mmol)
in ether (5 mL) was added HCl (1.0 M ether solution, 0.35 mL,
0.35 mmol) at -78 °C. The mixture was stirred for 30 min, and
then the solvent was removed. The residue was extracted with
toluene and dried in vacuo to give syn-4 as a yellow powder (35
mg, 90%). 31P{1H} NMR (121.5 MHz, C6D6): δ 87.3 (s).
Synthesis of exo,exo,syn-1,12-Bis(trimethylsilylmethyl)-1,12-
diphospha[1.1]ferrocenophane, syn-6. To a suspension of syn-4
(1.06 g, 2.12 mmol) in THF was added Me3SiCH2Li (1.0 M solution
of pentane, 4.6 mL, 4.6 mmol) at -78 °C. After stirring for 2.5 h
coordination plane of the Ni center because syn-5 is double-
chained, and thus they should exert a severe steric repulsion on
the two Cl atoms like in 8. The repulsion is, we suppose, a
major reason complex 10 adopts a tetrahedral geometry, in
which no such steric repulsion is anticipated, as seen in Figure
4. In contrast, the low-spin d8 Pd complexes 8 and 9 adopt a
square-planar structure in defiance of the inevitable steric
repulsion mentioned above.
Mn Complex. The photochemical reaction of [Cp′Mn(CO)3]
(Cp′ ) C5H4CH3) with syn-5 yielded the novel cyclic dinuclear
Mn complex 11, [{Cp′Mn(CO)2}2(µ-syn-5)], the molecular
structure of which was determined by X-ray analysis as shown
in Figure 5, where syn-5 is acting as a bridging ligand. The
twist angles of 70.41° and 72.44° are extraordinarily large
compared with those of some structurally characterized [1.1]-
ferrocenophanes7,12 including anti-3 (2.43°), syn-5 itself (24.8°),5a
and complexes 8-10 (9.2-27.2°). It has been confirmed that
CH2-bridged [1.1]ferrocenophane is a very flexible compound
with respect to twisting of the two ferrocene units, and it readily
undergoes anti-to-syn interconversion.13,14 Therefore it is natural
that the two P centers recede readily from each other by the
twisting, so that the bulky Mn fragment may be accommodated
on each P center, giving rise to a very large twist angle in 11
so as to avoid the steric repulsion otherwise anticipated between
1
the two bulky Cp′Mn(CO)2 moieties. H and 13C{1H} NMR
spectra of 11 in CDCl3 were consistent with its X-ray structure.
Experimental Section
General Remarks. All reactions were carried out under an
atmosphere of dry nitrogen using standard Schlenk tube techniques.
Solvents were dried and distilled from sodium (hexane), sodium/
benzophenone (ether, THF, and toluene), or P2O5 (CH2Cl2 and
MeCN). These solvents were stored under a dry nitrogen atmo-
(15) Nifant’ev, I. E.; Boricenko, A. A.; Manzhukova, L. F.; Nifant’ev,
E. E. Phosphorus, Sulfur Silicon 1992, 68, 99-106.
(16) Panda, T. K.; Gamer, M. T.; Roesky, P. W. Organometallics 2003,
22, 877-878.
(12) (a) Schachner, J. A.; Lund, C. L.; Quail, J. W.; Muller, J. Acta
Crystallogr. Sect. E 2005, E61, m682-m684. (b) Braunschweig, H.;
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Imamura et al.
at room temperature, a few drops of water was added to quench
the remaining Li compound and dried in vacuo. The residue was
extracted with hexane and dried in vacuo to give syn-6 as a yellow
powder (708 mg, 55%). 31P{1H} NMR (121.5 MHz, CDCl3): δ
-41.7 (s).
Synthesis of exo,exo,syn-1,12-Bis(p-tolyl)-1,12-diphospha[1.1]-
ferrocenophane, syn-7. To a solution of syn-4 (259 mg, 0.517
mmol) in THF was added p-tolylmagnesium bromide (1.0 M THF
solution, 1.3 mL, 1.3 mmol) at 0 °C. The mixture was stirred for
1 h at room temperature, and then one drop of water was added.
After the solvent was removed in vacuo, the residue was dissolved
in CH2Cl2 and then loaded on a silica gel column. A yellow band
eluted with CH2Cl2 was collected and dried in vacuo to give syn-7
as a red powder (80 mg, 25%). 31P{1H} NMR (121.5 MHz,
CDCl3): δ -31.8 (s).
Acknowledgment. This work was supported by Grants-in-
Aid for Scientific Research (Nos. 15350035, 16033245, 17036045,
and 17550061) from the Ministry of Education, Culture, Sports,
Science, and Technology, Japan.
Supporting Information Available: Text giving complete
experimental details and X-ray crystallographic data for anti-3, 8,
9, 10, and 11; X-ray data are also given in CIF format. This material
is available free of charge via the Internet at http://pubs.acs.org.
OM050809Q