Diastereoselective ortho-metalation of stereogenic ferrocenylphosphine oxides. Asymmetric synthesis of the first enantiopure phosphorus-chiral 2,2′-bis(diarylphosphino)-1,1′-biferrocenyls

Article abstract of DOI:10.1021/om991013s

Two novel phosphorus-chiral ligands, 2,2′-bis(arylphenylphosphino)-1,1′-biferrocenyls 1a (aryl = 1-naphthyl) and 1b (aryl = 2-biphenylyl), have been prepared in enantiopure form by stereoselective multistep synthesis. While asymmetry on phosphorus was established via nucleophilic substitution reactions at borane-protected phosphorus centers, ortho-iodination of the derived optically pure ferrocenylphosphine oxides served as the key step for the introduction of planar chirality. Utilizing biphenylylphenylphosphinoxyferrocene, 5b, the latter reaction was found to proceed in a highly diastereoselective manner, resulting in a product distribution of 97:3. The absolute configuration of the predominantly formed diastereomer was confirmed by crystal structure analysis of the Ullmann-coupled bis-(arylphenylphosphinoxy)biferrocenyl 6b (aryl = biphenylyl). Reduction of dioxides 6a (aryl = 1-naphthyl) and 6b gave rise to the enantiopure C₂-symmetrical title compounds comprising four adjacent stereocenters. The coordination behavior of 1a was investigated by a crystal structure determination of its Pt(II) dichloride complex 8a and compared with the structure of complex 8c, bearing the related 1,1′-bis(1-naphthylphenylphosphino)ferrocene ligand 1c.

Full text of DOI:10.1021/om991013s

Organometallics 2000, 19, 2299-2309
2299
Dia ster eoselective Or th o-Meta la tion of Ster eogen ic
F er r ocen ylp h osp h in e Oxid es. Asym m etr ic Syn th esis of
th e F ir st En a n tiop u r e P h osp h or u s-Ch ir a l
2,2′-Bis(d ia r ylp h osp h in o)-1,1′-bifer r ocen yls
Ulrike Nettekoven,† Michael Widhalm,*,‡ Paul C. J . Kamer,†
Piet W. N. M. van Leeuwen,*,† Kurt Mereiter,§ Martin Lutz,# and
Anthony L. Spek#
Institute of Molecular Chemistry, University of Amsterdam, Nieuwe Achtergracht 166,
1018 WV Amsterdam, The Netherlands, Institute of Organic Chemistry, University of Vienna,
Wa¨hringer Strasse 38, 1090 Vienna, Austria, Institute of Mineralogy, Crystallography and
Structural Chemistry, Technical University of Vienna, Getreidemarkt 9, 1040 Vienna, Austria,
and Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8,
3584 CH Utrecht, The Netherlands
Received December 20, 1999
Two novel phosphorus-chiral ligands, 2,2′-bis(arylphenylphosphino)-1,1′-biferrocenyls 1a
(aryl ) 1-naphthyl) and 1b (aryl ) 2-biphenylyl), have been prepared in enantiopure form
by stereoselective multistep synthesis. While asymmetry on phosphorus was established
via nucleophilic substitution reactions at borane-protected phosphorus centers, ortho-
iodination of the derived optically pure ferrocenylphosphine oxides served as the key step
for the introduction of planar chirality. Utilizing biphenylylphenylphosphinoxyferrocene, 5b,
the latter reaction was found to proceed in a highly diastereoselective manner, resulting in
a product distribution of 97:3. The absolute configuration of the predominantly formed
diastereomer was confirmed by crystal structure analysis of the Ullmann-coupled bis-
(arylphenylphosphinoxy)biferrocenyl 6b (aryl ) biphenylyl). Reduction of dioxides 6a (aryl
) 1-naphthyl) and 6b gave rise to the enantiopure C2-symmetrical title compounds
comprising four adjacent stereocenters. The coordination behavior of 1a was investigated
by a crystal structure determination of its Pt(II) dichloride complex 8a and compared with
the structure of complex 8c, bearing the related 1,1′-bis(1-naphthylphenylphosphino)ferrocene
ligand 1c.
In tr od u ction
variety of different ligand structures, other related
asymmetric building blocks, for instance biferrocenyls,
gained little attention. Although rotational barriers
around the bond linking the two cyclopentadienyl rings
in binaphthyl-analogous 2,2′-functionalized biferrocenyl
compounds are usually too low to promote axial chiral-
ity,3 the combination of two planar chiral elements
renders these structures attractive as C2-symmetrical
auxiliaries. The synthesis of enantiopure derivatives is
not straightforward, however, which might account for
the rather limited number of biferrocenyl-based ligands
reported to date.4 A practicable and stereoselective
access to the 2,2′-substituted biferrocenyl skeleton was
previously used by Ito and co-workers in the course of
their synthesis of trans-coordinating 2,2′-bis[1-(diaryl-
During recent years the development of new efficient
transition metal-catalyzed reactions and asymmetric
variants thereof resulted in a growing demand for novel,
highly active, and selective donor ligands. While chiral
synthons such as atropisomeric biphenyls, binaphthyls,
and their derivatives1 or planar chiral ferrocenyl moi-
eties2 have been successfully incorporated in a vast
* To whom correspondence should be addressed. E-mail: (M.W.)
miwi@felix.orc.univie.ac.at; (P.W.N.M.v.L.) pwnm@anorg.chem.uva.nl.
† University of Amsterdam.
‡ University of Vienna.
§ Technical University of Vienna; crystal structure analyses of 1a ,
6a , and 6b.
#
Utrecht University; crystal structure analyses of 8a and 8c.
(1) See for example: (a) Noyori, R.; Takaya, H. Acc. Chem. Res. 1990,
23, 345. (b) Schmid, R.; Broger, E. A.; Cereghetti, M.; Crameri, Y.;
Foricher, J .; Lalonde, M.; Mu¨ller, R. K.; Scalone, M.; Schoettel, G.;
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H. J . Am. Chem. Soc. 1997, 119, 4413. (e) Doucet, H.; Brown, J . M.
Tetrahedron: Asymmetry 1997, 8, 3775, and references therein.
(2) See for example: (a) Ferrocenes; Togni, A., Hayashi, T., Eds.;
VCH Publishers: Weinheim, Germany, 1995; Chapters 2-4. (b)
Richards, C. J .; Locke, A. J . Tetrahedron: Asymmetry 1998, 9, 2377.
(c) Kagan, H. B.; Diter, P.; Gref, A.; Guillaneux, D.; Masson-Szymczak,
A.; Rebiere, F.; Riant, O.; Samuel, O.; Taudien, S. Pure Appl. Chem.
1996, 68, 29.
(3) (a) Schlo¨gl, K.; Walser, M. Monatsh. Chem. 1969, 100, 1515. (b)
Marr, G.; Moore, R. E.; Rockett, B. W. Tetrahedron 1969, 25, 3477. (c)
Krajnik, P.; Kratky, C.; Schlo¨gl, K.; Widhalm, M. Monatsh. Chem. 1990,
121, 945.
(4) (a) Sawamura, M.; Hamashima, H.; Ito, Y. Tetrahedron: Asym-
metry 1991, 2, 593. (b) Sawamura M.; Yamauchi, A.; Takegawa T.;
Ito, Y. J . Chem. Soc., Chem. Commun. 1991, 874. (c) Sawamura, M.;
Hamashima, H.; Sugawara, M.; Kuwano, R.; Ito, Y. Organometallics
1995, 14, 4549. (d) Kuwano, R.; Sawamura, M.; Okuda, S.; Asai, T.;
Ito, Y.; Redon, M.; Krief, A. Bull. Chem. Soc. J pn. 1997, 70, 2807, and
references therein. (e) Kim, S.-G.; Cho, C.-W.; Ahn, K. H. Tetrahedron
1999, 55, 10079. (f) Kuwano, R.; Uemura, T.; Saitoh, M.; Ito, Y.
Tetrahedron Lett. 1999, 40, 1327.
10.1021/om991013s CCC: $19.00 © 2000 American Chemical Society
Publication on Web 05/12/2000

2300 Organometallics, Vol. 19, No. 12, 2000
Nettekoven et al.
Sch em e 1
or dialkylphosphino)ethyl]-1,1′-biferrocenyls (TRAP
ligands).4a,c,d The key features of that reaction sequence
are the diastereoselective ortho-iodination of optically
pure N,N-dimethyl-1-ferrocenylethylamine, followed by
stereospecific replacement of the amine moiety by
phosphine oxides, herewith determining centro-chirality
as well as metallocene chirality before the subsequent
establishment of the biferrocenyl backbone via Ullmann-
type coupling.
Within our current research directed toward the
synthesis and application of novel ligands incorporating
stereogenic phosphorus moieties, we wanted to explore
the catalytic properties of biferrocenyl-based aryldiphos-
phine structures. In addition, we became interested in
the stereodifferentiating potential of optically active
ferrocenylphosphine oxides. During recent years, several
new methods for the generation of planar chiral enantio-
enriched ferrocene derivatives were disclosed,5 among
which the lithium-sparteine-mediated ortho-metalation
of diisopropylamidoferrocene was considered especially
useful.6 Concerning dissymmetric ortho-directing groups,
various oxazoline,7 sulfoxide,8 and acetal moieties9 were
previously found to give the desired 1,2-substituted
derivatives with the same or even higher selectivities
than that stated for the well-known Ugi-amine (92%
de).10 In contrast, stereoselective ortho-metalation ef-
fected by optically pure ferrocenylphosphine oxides has
not been reported to date. In this paper we describe the
results of a study on the diastereoselective ortho-
magnesiation of two different diarylphosphinoxyfer-
rocenes. The thus obtained ortho-iodoferrocenylphos-
phine oxides were employed in the asymmetric synthesis
of the first P-chiral enantiopure biferrocenyldiphosphine
ligands 1a and 1b.
Resu lts a n d Discu ssion
Dia ster eoselective Or th o-Meta la tion of En a n -
tiop u r e F er r ocen ylp h osp h in e Oxid es. As a part of
our ongoing project concerned with the development and
exploration of new asymmetrically substituted phos-
phorus donors, we recently prepared a series of P-chiral
1,1′-bis(diphenylphosphino)ferrocene (dppf) analogues.11
Expanding a synthetic pathway described by J uge´ et
al.,12 we succeeded in the stereoselective coupling of
different methyl arylphenylphosphinite boranes with
dilithioferrocene. After decomplexation of the bis-
(borane) adducts using diethylamine, five novel enan-
tiopure ferrocenyldiphosphine ligands were obtained.
In a similar manner, this methodology was applied
to the synthesis of the desired P-chiral ferrocenylphos-
phine oxides. Monolithioferrocene, prepared according
to Kagan’s protocol,13 was made to react with 1 equiv
of (R)- or (S)-phosphinite borane 2a ,b, after deprotection
yielding configurationally inversed ferrocenylmonophos-
phines 3a ,b. These were stereoselectively oxidized in the
presence of H2O2, giving the optically pure phosphine
oxides 4a ,b (Scheme 1).
On extrapolating our findings during the synthesis
of the related diphosphines, where nucleophilic attack
of dilithioferrocene proceeded with high degrees of
stereoselectivity,12 we expected a similar outcome for
the analogous monosubstitution step. The enantiomeric
purity of the monophosphine oxides was checked by
applying the chiral NMR solvating reagent (S)-N-(3,5-
dinitrobenzoyl)-1-phenylethylamine.14 Within the NMR
integration errors of (2%, indeed, no traces of the other
(8) (a) Rebie`re, F.; Riant, O.; Ricard, L.; Kagan, H. B. Angew. Chem.,
Int. Ed. Engl. 1993, 32, 568. (b) Riant, O.; Argouarch, G.; Guillaneux,
D.; Samuel, O.; Kagan, H. B. J . Org. Chem. 1998, 63, 3511.
(9) (a) Riant, O.; Samuel, O.; Kagan, H. B. J . Am. Chem. Soc. 1993,
115, 5835. (b) Riant, O.; Samuel, O.; Flessner, T.; Taudien, S.; Kagan,
H. B. J . Org. Chem. 1997, 62, 6733.
(10) (a) Marquarding, D.; Klusacek, H.; Gokel, G.; Hoffmann, P.;
Ugi, I. J . Am. Chem. Soc. 1970, 92, 5389. (b) Marquarding, D.;
Klusacek, H.; Gokel, G.; Hoffmann, P.; Ugi, I. Angew. Chem., Int. Ed.
Engl. 1970, 9, 371.
(11) (a) Nettekoven, U.; Widhalm, M.; Kamer, P. C. J .; van Leeuwen,
P. W. N. M. Tetrahedron: Asymmetry 1997, 8, 3185. (b) Nettekoven,
U.; Kamer, P. C. J .; van Leeuwen, P. W. N. M.; Widhalm, M.; Spek, A.
L.; Lutz, M. J . Org. Chem. 1999, 64, 3996.
(12) (a) J uge´, S.; Stephan, M.; Laffitte, J . A., Geneˆt, J . P. Tetrahe-
dron Lett. 1990, 31, 6357. (b) J uge´, S.; Stephan, M.; Merde`s, R.; Geneˆt,
J . P.; Halut-Desportes, S. J . Chem Soc., Chem. Commun. 1993, 531.
(5) For recent reviews see: (a) Togni, A. Angew. Chem., Int. Ed.
Engl. 1996, 35, 1475. (b) Kagan, H. B.; Riant, O. Advances in
Asymmetric Synthesis; Hassner, A., Ed.; J AI Press Inc.: Greenwich,
CT, 1997; Vol. 2, pp 189-235. (c) Reference 2b.
(6) Tsukazaki, M.; Tinkl, M.; Roglans, A.; Chapell, B. J .; Taylor, N.
J .; Snieckus, V. J . Am. Chem. Soc., 1996, 118, 685.
(7) (a) Sammakia, T.; Latham, H. A.; Schaad, D. R. J . Org. Chem.
1995, 60, 10. (b) Richards, C. J .; Damalidis, T.; Hibbs, D. E.;
Hursthouse, M. B. Synlett 1995, 74. (c) Nishibayashi, Y.; Uemura, S.
Synlett 1995, 79. (d) Sammakia, T.; Latham, H. A. J . Org. Chem. 1995,
60, 6002.

Diastereoselective Ortho-Metalation
Organometallics, Vol. 19, No. 12, 2000 2301
Sch em e 2
F igu r e 1. Displacement ellipsoid plot of (RP,Rm,Rm,RP)-
6b, drawn at the 50% probability level.
differentiation proved to be considerably higher, with
the two isomers being formed in a 97:3 ratio. Change
of solvent (Et2O) or reaction temperature (magnesiation
at -40 °C) affected neither the yield nor the stereose-
lectivity. The thus obtained diastereomeric excess of
94% de ranks among the highest values for induction
of planar chirality reported to date and constitutes the
first example of an efficient, stereoselective phosphine
oxide-functionalized directing metalation group on fer-
rocene.
enantiomer were detected in recrystallized samples of
phosphine oxides 4a ,b, respectively.
Preliminary ortho-lithiation experiments were carried
out using phosphine oxide 4a and n-butyllithium as
metalating agent. Quenching reactions with D2O, I2, or
1,2-diiodoethane yielded only small quantities (10-20%)
of regioisomeric product mixtures, indicating unspecific
and ineffective lithiation behavior. Variation of reaction
temperature (-78 °C, 0 °C, room temperature), reagent
(tert-BuLi), and solvent (diethyl ether, THF, and mix-
tures thereof) gave no improvement. These findings
contrasted with the reports of successful ortho-lithiation
reactions on (substituted) benzenes, directed by related
bis(dimethylamino)phosphinoxy,15 diphenylphosphi-
noxy,16 and, especially, di-tert-butylphosphinoxy17 groups.
Considering the longer PdO‚‚‚ortho-H distance in the
five-membered ferrocene skeleton, nonselective depro-
tonation might be due to insufficient lithium-oxygen
orbital overlap, suggesting that the use of a different
metal might improve selectivity. To this aim, employ-
ment of diisopropylamidomagnesium bromide18 was
attempted, and this reagent proved to effect quantitative
ortho-magnesiation of 4a after 3 h at room temperature.
Subsequent quenching of the reaction with iodine/THF
solution at -30 °C afforded a mixture of the two ortho
iodo products in good yields (Scheme 2). After column
chromatographic separation the ratio of diastereomers
was found to be 75:25, which was in agreement with
NMR measurements of the crude product mixture.
When biphenylylphenylphosphinoxyferrocene 4b was
subjected to the above-mentioned protocol, diastereo-
Syn th esis of En a n tiop u r e 1,1′-Bifer r ocen yl-2,2′-
diph osph in es. Optically pure ortho-iodoferrocenylphos-
phine oxides, obtained stereoselectively (5b) or by
column chromatographic separation (5a ), were subjected
to Ullmann coupling at 130 °C using activated copper
powder (Scheme 3). After 2 days the desired biferroce-
nyldiphosphine dioxides were isolated, together with
some amounts of starting material, thus making the
yields in products range from 58% (6a ) to 70% (6b).
To determine the relative configuration of the pre-
dominantly formed ortho-iodination product 5b, a crys-
tal structure analysis of the derived Ullmann-coupled
biferrocenyl diphosphine dioxide 6b was performed.
Having employed (R)-methyl phosphinite borane 2b as
electrophile in the reaction with monolithioferrocene,
(S)-configurated phosphine 3b and, subsequently, phos-
phine oxide (R)-4b were expected to be formed (vide
supra). Since (partial) racemization of planar chiral
compounds is rather unlikely to occur under Ullmann
conditions, conservation of metallocene chirality can be
assumed. As depicted in Figure 1, the crystals of
enantiopure 6b possess the (RP,Rm,Rm,RP) configuration
at the four stereogenic elements. Consequently, the (RP)-
configurated phosphine oxide gave rise to the (Rm)-
magnesiated intermediate and, finally, lead to the (Sm)-
iodo product. Considering the schematic model structures
displayed below, the preferred site of metalation corre-
sponds to a conformation in which the bulky biphenyl
group occupies a position above the ferrocene moiety in
order to minimize steric interactions with the unsub-
stituted cyclopentadienyl ring (Scheme 4). This sort of
mechanistic rationale has also been invoked for other
stereodiscriminating directing ortho-metalation groups
on ferrocene,19 including the structurally similar ferro-
cenyl-tert-butylsulfoxide.8 In our case, it is further sub-
(13) (a) Rebiere, F.; Samuel, O.; Kagan, H. B. Tetrahedron Lett.
1990, 31, 3121. (b) Guillaneux, D.; Kagan, H. B. J . Org. Chem. 1995,
60, 2502.
(14) Dunach, E.; Kagan, H. B. Tetrahedron Lett. 1985, 26, 2649.
(15) Stuckwisch, C. G. J . Org. Chem. 1976, 41, 1173.
(16) Schaub, B.; J enny, T., Schlosser, M. Tetrahedron Lett. 1984,
25, 4097.
(17) Gray, M., Chapell, B. J .; Felding, J ., Taylor, N. J .; Snieckus, V.
Synlett 1998, 422.
(18) Eaton, P. E.; Lee, C.-H.; Xiong, Y. J . Am. Chem. Soc. 1989, 111,
8016.

2302 Organometallics, Vol. 19, No. 12, 2000
Nettekoven et al.
Sch em e 3
Sch em e 4
stantiated by the lower diastereomeric ratio obtained
for phosphine oxide 4a , which seems less prone to
exhibit intramolecular repulsive interaction, due to its
smaller degree of sterical encumbrance.
F igu r e 2. Displacement ellipsoid plot of (RP,Rm,Sm,SP)-
6b, drawn at the 50% probability level (symmetry operation
′: 1-x, -y, 1-z).
Diphosphine dioxide 6b was found to crystallize as a
dichloromethane solvate in the chiral space group
P212121 with four biferrocenyl molecules in the unit cell.
The absolute configuration was determined via anoma-
lous dispersion; the Flack parameter x ) 0.019(12)
indicated enantiomeric integrity.20 The biferrocenyl
molecule is approximately C2 symmetrical in the crystal
(Figure 1). In view of the considerable conformational
freedom of this compound, this finding seems surprising,
but may in part result from favorable intramolecular
π‚‚‚π interactions between the inner phenyl rings of the
two biphenyl groups (e.g., C18‚‚‚C46 ) 3.45 Å) and
between the terminal phenyl rings of the biphenyl units
and the P-bonded phenyl rings (e.g., C11‚‚‚C23 ) 3.14
Å, C39‚‚‚C51 ) 3.09 Å). The torsional angle of the
biferrocenyl moiety is Fe1-C6-C34-Fe2 ) -69.9(3)°.
The biphenyl groups adopt the usual twisted conforma-
tions, with plane angles of 69.4(2)° and 67.0(2)°. Their
orientations relative to ferrocene are defined by the
dihedral angles Fe1-C7-P1-C17 ) 160.3(2)°, C7-P1-
C17-C18 ) 21.7(3)°, Fe2-C35-P2-C45 ) 158.4(2)°,
and C35-P2-C45-C46 ) 15.0(3)°.
If racemic or nonenantiopure ortho-iodophosphinoxy-
ferrocene 5 was employed in the Ullmann reaction, not
only homocoupling of identically configurated isomers
but also heterodimerization between the two enantio-
mers with opposite configuration took place. For starting
material (()-5a , the presumably formed (Rm,Sm)-con-
figurated meso products were unstable and could not
be isolated. In contrast, using racemic 1-iodo-2-biphe-
nylylphenylphosphinoxyferrocene 5b, we were able to
obtain the meso product (RP,Rm,Sm,SP)-6b. Formation
of the Ci-symmetrical isomer seemed, indeed, to be
preferred for steric reasons, resulting in a meso:rac
product distribution of 2.3:1. The crystal structure of
the meso-diphosphine dioxide is shown in Figure 2.
Compound meso-6b crystallizes in the centrosymmet-
ric space group P1h with the inversion center located on
(19) Wagner, G.; Herrmann, R. In Ferrocenes; Togni, A., Hayashi,
T., Eds.; VCH Publishers: Weinheim, Germany, 1995; Chapter 4, and
references therein.
(20) Flack, H. D. Acta Crystallogr. 1983, A39, 876.

Diastereoselective Ortho-Metalation
Organometallics, Vol. 19, No. 12, 2000 2303
F igu r e 3. Displacement ellipsoid plot of (RP,Rm,Rm,RP)-
6a , drawn at the 50% probability level.
the midpoint of the ferrocenyl-ferrocenyl bond (Ci
symmetry). The inversion center implies that the Cp
planes of the ferrocene units are coplanar and that Fe-
C6-C6′-Fe′ ) 180°. In contrast to ortho-substituted
biphenyls, no steric interactions of ortho protons are
detected in the biferrocenyl entity, rendering the copla-
nar arrangement not unfavorable. The orientations of
the biphenyl goups differ with dihedral angles of Fe1-
C7-P1-C17 ) 177.1(2)° and C7-P1-C17-C18 )
-16.8(4)° from (RP,Rm,Rm,RP)-6b and do not permit the
intramolecular π‚‚‚π interactions mentioned above. The
biphenyl substituents adopt a typical angle of 65.1(2)°.
For reasons of comparison, and in order to define the
relative metallocene configuration of the ortho-iodo
product formed in excess, we also performed a crystal
structure analysis on a racemic sample of 1-naphthyl-
substituted biferrocenyldiphosphine dioxide 6a (Figure
3). The observed (RP,Rm,Rm,RP) configuration of the four
stereocenters is in agreement with the stereochemical
model discussed above, assuming the 1-naphthyl sub-
stituent displays the larger steric bulk with respect to
the phenyl group.
Dioxide rac-6a was found to crystallize in the cen-
trosymmetric space group P21/c with four molecules in
the unit cell. The molecules display approximately C2
symmetry in the crystal. The biferrocenyl unit shows a
twist angle of Fe1-C6-C32-Fe2 ) -67.7(2)°, similar
to (RP,Rm,Rm,RP)-6b. The orientations of the naphthyl
groups relative to ferrocene are defined by dihedral
angles of Fe1-C7-P1-C17 ) 171.4(1)°, C7-P1-C17-
C18 ) -2.6(2)°, Fe2-C33-P2-C43 ) 170.5(1)°, and
C33-P2-C43-C44 ) -0.2(2)°. This conformation re-
sults in an almost parallel arrangement of the naphthyl
groups with a distance between them of about 3.3 Å,
indicating favorable intramolecular π‚‚‚π interactions.
With enantiopure biferrocenyl derivatives 6a and 6b
in hand, the reduction of the phosphine oxides remained
to be accomplished. Mild reducing agents, however, such
as polymethylhydrosiloxane/Ti(O-iPr)4,21 left the start-
ing material unchanged, as did the combination HSiCl3/
benzene/triethylamine. Only when rather harsh reaction
F igu r e 4. Displacement ellipsoid plot of (SP,Rm,Rm,SP)-
1a , drawn at the 50% probability level (symmetry operation
′: 1-x, y, 1.5-z).
conditions were applied, namely, HSiCl3/toluene/tri-
ethylamine at 130 °C for 72 h, were the sterically
hindered dioxides completely reduced to the correspond-
ing diphosphines 1a and 1b. As a consequence of the
prolonged treatment, partial epimerization of the ste-
reogenic phosphorus centers was observed, resulting in
a mixture of stereoisomers. For diphosphine 1a , the
product average composition was found to be 60% of the
desired (SP,Rm,Rm,SP)-configurated isomer, 35% of the
monoepimerized C1-symmetrical (RP,Rm,Rm,SP)-diaste-
reomer, and 5% of the doubly isomerized (RP,Rm,Rm,RP)-
product. In the case of diphosphine 1b, the extent of
epimerization was somewhat smaller, resulting in a 65:
30:5 distribution of diastereomers, configurated as
mentioned above. Isolation and purification of the C2-
symmetrical (SP,Rm,Rm,SP)-products was achieved by
column chromatographic separation of their bis(borane)
adducts.22 Finally, stereospecific deprotection of the
borane complexes using diethylamine23 or trifluo-
romethanesulfonic acid/KOH24 gave rise to enantiomeri-
cally pure P-chiral biferrocenyldiphosphines 1a and 1b,
respectively.
Crystals of ligand (()-1a , prepared in an analogous
manner from racemic starting material, were grown
from CH2Cl2/hexane and found to crystallize in the
centrosymmetric space group Pbcn (Figure 4). The
molecules exhibit an exact, crystallographic C2 sym-
metry. In the solid state, channels in the direction of
the c-axis are present, which are filled with disordered
solvent molecules. The twist angle of the biferrocenyl
unit is, with Fe-C6-C6′-Fe′ ) 37.6(4)°, distinctly
smaller than in the previously discussed compounds.
(22) For a review on the use of borane complexes as intermediates
in chiral phosphine ligand synthesis, see: Ohff, M.; Holz, J .; Quirm-
bach, M.; Bo¨rner, A. Synthesis 1998, 1391.
(23) Imamoto, T.; Oshiki, T.; Onozawa, T.; Kusumoto, T.; Sato, K.
J . Am. Chem. Soc. 1990, 112, 5244.
(24) McKinstry, L.; Livinghouse, T. Tetrahedron Lett. 1994, 35, 9319.
(21) Coumbe, T.; Lawrence, N. J .; Muhammad, F. Tetrahedron Lett.
1994, 35, 625.

2304 Organometallics, Vol. 19, No. 12, 2000
Nettekoven et al.
Ta ble 1. Selected In ter a tom ic Dista n ces (Å) a n d
An gles (d eg) in Com p lexes 8a ,c
8a
8c
P1-Pt
2.2558(14)
2.2415(16)
2.3726(16)
2.3660(14)
1.824(6)
2.2555(13)
2.2521(14)
2.3487(13)
2.3552(11)
1.807(5)
P1A-Pt
Pt-Cl1
Pt-Cl1A
P1-C1
P1A-C1A
P1‚‚‚P1A
1.816(6)
3.243(2)
1.807(5)
3.5269(19)
P1-Pt-P1A
Cl1-Pt-Cl1A
Pt-P1-C1
Pt-P1A-C1A
Pt-P1-C11
Pt-P1A-C11A
Pt-P1-C6
Pt-P1A-C6A
Pt-P1-C21
Pt-P1A-C21A
Pt-P1-C16
Pt-P1A-C16A
92.30(5)
88.87(6)
116.59(19)
115.06(19)
116.0(2)
102.97(5)
88.28(5)
123.96(17)
123.80(17)
117.85(19)
111.82(15)
111.23(18)
105.4(2)
106.0(2)
F igu r e 5. Displacement ellipsoid plot of [(SP,Rm,Rm,SP)-
1a ]PtCl2, 8a , drawn at the 50% probability level.
111.46(17)
111.82(18)
Pt-P1-C1-C2
-72.8(6)
-74.4(5)
129.19(17)
135.3(2)
103.6(5)
102.2(5)
Pt-P1A-C1A-C2A
Pt-P1-C11-C12
Pt-P1A-C11A-C12A
Pt-P1-C6-C7
116.1(4)
121.9(4)
Pt-P1A-C6A-C7A
Pt-P1-C21-C22
Pt-P1A-C21A-C22A
Pt-P1-C16-C17
Pt-P1A-C16A-C17A
-30.6(5)
-34.7(6)
6.9(5)
4.0(5)
complex of the related ferrocene-based ligand 1c,11
which is depicted below.
F igu r e 6. Displacement ellipsoid plot of [(SP,SP)-1c]PtCl2,
8c, drawn at the 50% probability level.
The orientations of the naphthyl groups relative to
ferrocene, Fe-C7-P-C17 ) 177.1(1)° and C7-P-C17-
C18 ) 1.7(2)°, however, compare well with those of rac-
6a . The structure is devoid of intramolecular π‚‚‚π
interactions. The phosphino groups occupy trans posi-
tions with respect to each other, resulting in a P‚‚‚P′
distance of 5.995(3) Å.
Cr ysta l Str u ctu r es of [2,2′-Bis(1-n a p h th ylp h e-
n ylp h osp h in o)-1,1′-b ifer r ocen yl]P t Cl2 a n d [1,1′-
B i s (1-n a p h t h y lp h e n y lp h o s p h i n o )fe r r o c e n e ]-
P tCl2. With regard to their unique structure and
intended application in catalysis, we were intrigued to
investigate the complexation behavior of the new P-
chiral biferrocenyldiphosphines. In contrast to the TRAP
ligands, which, due to their intrinsic conformational
flexibility and large natural bite angles,25 were found
to form trans-coordinated nine-membered-ring square-
planar Pd(II) and Rh(I) complexes,5c we expected the
formation of cis-fashioned seven-membered chelates.
Yet, the question arose, what influence might the
biferrocenyl moiety have on complex ring strain, phos-
phorus-metal-phosphorus bite angle, and structural
features in general? Such data seemed especially inter-
esting when compared to those of a platinum dichloride
Because ligands 1a and 1c bear identical substitution
patterns on the chiral phosphorus donors, their elec-
tronic properties were assumed to be similar, whereas
major differences in their platinum complex structures
were expected to arise from backbone constitution.
Platinum complexes 8a ,c were prepared by reaction of
bis(benzonitrile)dichloroplatinum(II) with the respective
ligands (SP,Rm,Rm,SP)-1a and (SP,SP)-1c. The crystal
structures are depicted in Figures 5 and 6; comparative
interatomic distances and angles are summarized in
Table 1.
Interestingly, the platinum and phosphorus geom-
etries observed for 8a and 8c display few similarities.
Complex 8c, bearing the (SP,SP)-configurated diphos-
phine, crystallizes in the chiral space group P212121, and
a determination of the Flack x parameter20 confirmed
the absolute configuration. The C2 symmetry of the
complex is only approximately fulfilled in the solid state.
The large deflection from the ideal 90 ° phosphorus-
platinum-phosphorus angle of an undistorted square-
planar cis-coordinated complex may be rationalized by
simple modeling considerations. Assuming an ideal
(25) (a) Casey, C. P.; Whiteker, G. T. Isr. J . Chem. 1990, 30, 299.
(b) Casey, C. P.; Whiteker, G. T.; Melville, M. G.; Petrovich, L. M.;
Gavney, J . A. J r.; Powell, D. R. J . Am. Chem. Soc. 1992, 114, 5535.

Diastereoselective Ortho-Metalation
Organometallics, Vol. 19, No. 12, 2000 2305
platinum-phosphorus distance of 2.29 Å (mean value
of 5404 bond lengths extracted from the Cambridge
Structural Database26), the optimum P1‚‚‚P1A distance
attainable by any bidentate ligand is 3.24 Å. This value
is similar to the Cp‚‚‚Cp distance in ferrocene, 3.26 Å.
Rotation of the cyclopentadienyl rings of a 1,1′-ferroce-
nyldiphosphine against each other results in enlarge-
ment of the P1‚‚‚P1A distance of up to 6.8 Å (trans-
arrangement of the phosphine moieties). In an eclipsed
conformation of the latter, the platinum geometry is
prevailingly undistorted, whereas the Pt-P1-C1 angles
of about 135° are unfavorably high, herewith strongly
deviating from the ideal value of 114-115°.26 Thus, for
complex 8c, distortion of the platinum geometry toward
a wider P1-Pt-P1A angle and/or the phosphorus
geometries toward smaller Pt-P1-C1 angles was ex-
pected. The crystal structure, indeed, revealed a highly
strained system with a bite angle of 102.97(5)° as well
as Pt-P1-C1 and Pt-P1A-C1A angles of 124.0(2)° and
123.8(2)°, respectively. This compromise between the
distortion of the platinum and phosphorus geometries
is achieved by a small rotation of the cyclopentadienyl
rings toward a staggered arrangement (torsion angle
P1-C1-C1A-P1A ) 5.3(3)°) and a distortion at the
atoms C1 and C1A (C2-C1-P1 and C2A-C1A-P1A
angles: 129.4(4)° and 127.7(4)°), both together resulting
in a P1‚‚‚P1A distance of 3.527(2) Å. Similar values for
that distance were found in the platinum(II) dichloride
complex of dppf27 and its palladium(II) analogue,28
which exhibit bite angles of 99.3(1)° and 99.07(5)°,
respectively. Yet, in these cases distortion is mainly due
to a truly staggered conformation of the cyclopentadi-
enyl rings. For compound 8c, release of steric strain via
such an arrangement might be impeded by the bulki-
ness of the 1-naphthyl substituents, herewith enforcing
the widest bite angle reported for comparable dppf-type
complexes so far.
served for related complexes.29 Due to the similarity of
the backbone skeletons, these features compare well
with the structural data reported for a Binap palladium-
(II) dichloride complex.30 The almost in-plane arrange-
ment of Pt, P1, P1A, Cl1, and Cl1A atoms with an angle
sum of 359.9(9)° around platinum suggested, however,
the steric repulsion between the chlorine atoms and
equatorial phosphine substituents in 8a to be less
pronounced than in the mentioned Binap derivative
(angle sum: 367.3(2)°).
The dissimilar modeling of the platinum coordination
sphere by the two diphosphines was also evidenced by
the solution structures of the respective complexes 8a
and 8c. The 31P-resonance signals for the free ligands
were found at chemical shift values of δ ) -30.60 ppm
11b
(1a ) and δ ) -30.39 ppm (1c).
Upon complexation,
however, the coordination chemical shift ∆δ31 observed
for 8c of 43.88 ppm to δ ) +13.49 ppm was larger than
the shift value for 8a (δ ) -6.21 ppm; ∆δ ) 24.39 ppm).
These findings reflect the stronger bending32 of phos-
phine metal bonds in five-membered platinum(II) ring
chelates as compared to their seven-membered ana-
logues, since the occurrence of endo- and exocyclic
metal-phosphorus-carbon angles close to the tetrahe-
dral value will result in a deshielding contribution to
the isotropic shift tensor (Table 1).33
Steric effects imposed by the phenyl and naphthyl
substituents on chiral phosphorus appeared less pro-
nounced; only for complex 8c was broadening of signals
due to hindered rotation around phosphorus carbon
bonds observed to a small extent. At room temperature,
the signals at δ ) 8.61 ppm and δ ) 8.41 ppm, assigned
to the protons in positions 2 and 8 of the naphthyl
moieties by 2D NMR experiments, showed slight broad-
ening. Cooling the sample resulted in gradual broaden-
ing of all signals; however, no defined decoalescence
could be reached at the lowest available temperature
of 163 K.34
In complex 8a , representing the first crystallographi-
cally characterized example of ligation by a 2,2′-diphos-
phino-1,1′-biferrocenyl, the P1‚‚‚P1A distance may be
tuned by rotation around the C-C bond linking the two
ferrocenyl groups. Consequently, the accessible dis-
tances range between 2.0 and 6.0 Å, allowing for easy
accommodation of the optimum value of 3.24 Å, calcu-
lated for a square-planar cis-chelated platinum complex
(vide supra). Additionally, the Pt-P1-C1 angle was
assumed to be less strained in comparison to complex
8c. The actual structure of 8a was found to be in good
agreement with these expectations; neither the plati-
num nor the phosphorus geometries are severely dis-
torted. The space group of complex 8a was identified
as P212121, and, again, determination of the Flack x
parameter confirmed the absolute configuration. The C2
symmetry of compound 8a is not completely met in the
crystal. The naphthyl groups occupy pseudoequatorial
positions with respect to the P1-Pt-P1A plane, whereas
the phenyl rings are oriented in an axial fashion. The
P1-Pt-P1A bite angle is 92.30(5)°, and Pt-P and
Pt-Cl bond lengths are within the typical range ob-
Con clu sion s
Utilizing a multistep approach, we succeeded in the
stereoselective synthesis of the first enantiopure
P-chiral 2,2′-bis(diarylphosphino)-1,1′-biferrocenyls. An
asymmetrically substituted phosphorus moiety, intro-
duced by stereoselective nucleophilic attack of mono-
lithioferrocene on optically pure methyl phosphinite
boranes, served as a key structural motif of the se-
quence. Subsequently, chirality on phosphorus allowed
for separation of the derived ortho-iodoferrocenylphos-
phine oxides. Depending on the nature of residues at
the phosphorus atom, the ortho-iodination reaction was
found to proceed stereoselectively (up to 94% de under
optimized reaction conditions). This represents the first
(29) Orpen, G. A.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G.; Taylor, R. International Tables for Crystallography, Volume C;
Kluwer Academic Publishers: Dordrecht, The Netherlands, 1995; p
707.
(30) Ozawa, F.; Kubo, A.; Matsumoto, Y.; Hayashi, T.; Nishioka, E.;
Yanagi, K.; Moriguchi, K. Organometallics 1993, 12, 4188.
(31) Mann, B. E.; Masters, C.; Shaw, B. L.; Slade, R. M.; Stainbank,
R. E. Inorg. Nucl. Chem. Lett. 1971, 7, 881.
(32) Powell, J . J . Chem. Soc., Chem. Commun. 1989, 200.
(33) Lindner, E.; Fawzi, R.; Mayer, H. A.; Eichele, K.; Hiller, W.
Organometallics 1992, 11, 1033.
(34) An analogous NMR investigation of complex 8a was prevented
due to its insufficient solubility at lower temperatures.
(26) Allen, F. H.; Kennard, O. Chem. Des. Autom. News 1993, 8,
31.
(27) Clemente, D. A.; Pilloni, G.; Corain, B.; Longato, B.; Titipicchio-
Camellini, M. Inorg. Chim. Acta 1986, 115, L9.
(28) Hayashi, T.; Konishi, M.; Kobori, Y.; Kumada, M.; Higuchi, T.;
Hirotsu, K. J . Am. Chem. Soc. 1984, 106, 158.

2306 Organometallics, Vol. 19, No. 12, 2000
Nettekoven et al.
to -40 °C, and the monolithioferrocene suspension was slowly
added via Teflon cannula. The reaction mixture was allowed
to warm to ambient temperature over a period of 12 h and
then quenched with H2O. THF was evaporated, and the
residue was extracted with CH2Cl2. The combined organic
layers were washed with H2O, dried over MgSO4, and filtrated,
and the solvent was evaporated. For deboronation, the residue
was dissolved in 50 mL of degassed diethylamine and stirred
overnight at room temperature. After removal of solvent, the
crude product was purified by column chromatography (SiO2;
hexane/CH2Cl2 ) 4:1) to remove excess ferrocene and small
quantities (<3%) of diphosphine byproduct. The desired fer-
rocenylmonophosphines were obtained as orange-yellow solids,
which were recrystallized from CH2Cl2/hexane.
example of a P-chiral phosphinoxy substituent effecting
a highly diastereoselective ortho-metalation on fer-
rocene. The stereospecific reduction of (bulky) chiral
biferrocenyldiphosphine dioxides, however, remained
troublesome. Nevertheless, metallocene chirality was
not affected during reduction and permitted the separa-
tion of partially epimerized products. The C2-sym-
metrical structure of the first enantiopure biferrocenyl
ligand 1a comprising four adjacent stereocenters was
substantiated by a crystal structure analysis, showing
a trans arrangement of the phosphine moieties.
The coordination behavior of diphosphine 1a was
investigated by means of a crystal structure determi-
nation of its platinum(II) dichloride complex. The cis-
chelated compound exhibits a P-Pt-P bite angle of
92.30(5)°, in agreement with less distorted phosphorus
and platinum geometries than observed for a structur-
ally similar Binap palladium(II) compound and the
corresponding complex of the C2-symmetrical ferrocene-
based ligand 1c (bite angle: 102.97(5)°). As to what
extent these solid-state structural features may influ-
ence efficient encumbering of the metal center by the
bulky 1-naphthyl substituents is unclear. Yet, the
higher flexibility of ligand 1a might still allow for
selective shielding of reagent trajectories, although the
latter is more commonly associated with the presence
of ligands enforcing large bite angles.35 Application of
the new chiral auxiliaries in several catalytic transfor-
mations is currently in progress, and we intend to report
on results and comparison with related ferrocene-based
P-chiral diphosphines11b in due course.
(S)-(+)-1-Na p h t h ylp h en ylp h osp h in ofer r ocen e,
3a .
1
Yield: 66%. Mp: 172 °C. H NMR (400.13 MHz): δ 3.88 (m,
1H); 4.08 (s, 5H); 4.29 (m, 1H); 4.37 (m, 1H); 4.42 (m, 1H);
7.19 (m, 1H); 7.27-7.50 (m, 8H); 7.77-7.82 (m, 2H); 8.42 (m,
1H) ppm. 13C NMR (100.62 MHz): δ 69.16 (5CH, d, J CP ) 0.9
Hz); 70.55 (d, CH, J CP ) 1.5 Hz); 71.15 (d, CH, J CP ) 6.1 Hz);
72.26 (d, CH, J CP ) 3.1 Hz); 74.08 (d, CH, J CP ) 26.0 Hz); 75.64
(d, C, J CP ) 4.6 Hz); 125.28 (d, CH, J CP ) 1.4 Hz); 125.75 (d,
CH, J CP ) 1.4 Hz); 125.96 (d, CH, J CP ) 2.3 Hz); 126.05 (d,
CH, J CP ) 26.0 Hz); 128.15 (d, CH, J CP ) 7.6 Hz); 128.51 (d,
CH, J CP ) 1.5 Hz); 128.74 (CH); 129.06 (CH); 131.53 (d, CH,
J CP ) 1.4 Hz); 133.35 (d, C, J CP ) 3.8 Hz); 133.93 (d, CH, J CP
) 19.9 Hz); 134.78 (d, C, J CP ) 20.6 Hz); 136.91 (d, C, J CP
)
14.5 Hz); 137.42 (d, C, J CP ) 7.6 Hz) ppm. 31P NMR (161.98
20
MHz): δ -24.66 (s) ppm. [R]D ) +127.8 (c 0.51; CH2Cl2).
HRMS (EI+): m/z calcd 420.0730; obsd 420.0728. Anal. Calcd
for C26H21FeP: C, 74.31; H, 5.04. Found: C, 74.14; H, 5.20.
(S)-(+)-2-Bip h en ylylp h en ylp h osp h in ofer r ocen e, 3b .
1
Yield: 66%. Mp: 102-104 °C. H NMR (400.13 MHz): δ 3.80
(m, 1H); 3.94 (s, 5H); 4.27 (m, 1H), 4.31 (m, 1H); 4.37 (m, 1H);
7.05-7.08 (m, 2H); 7.11-7.15 (m, 2H); 7.16-7.33 (m, 10H)
ppm. 13C NMR (100.62 MHz): δ 68.99 (5CH); 70.49 (CH); 71.01
(d, CH, J CP ) 6.9 Hz); 71.83 (CH); 74.71 (d, CH, J CP ) 30.6
Hz); 76.50 (d, C, J CP ) 7.6 Hz); 126.84 (CH); 127.51 (2CH);
127.76 (d, CH, J CP ) 7.6 Hz); 128.02 (CH); 128.43 (d, CH, J CP
Exp er im en ta l Section
Gen er a l Com m en ts. If not otherwise stated, reactions
were carried out under an atmosphere of argon using standard
Schlenk techniques. THF and diethyl ether were distilled from
sodium benzophenone ketyl, CH2Cl2 and acetonitrile were
distilled from CaH2, and toluene and methanol from sodium
wire under nitrogen. 1D and 2D (1H-1H COSY) NMR spectra
were recorded on 250, 300, and 400 MHz instruments; CDCl3
was used as solvent, if not further specified. Phosphorus-
carbon coupling constants (J CP) were identified by comparison
of J -modulated 13C spectra measured at different magnetic
field strengths. Elemental analyses were obtained using an
Elementar Vario EL apparatus. Mass spectra were recorded
on a J EOL J MS SX/SX102A four sector mass spectrometer;
for FAB-MS 3-nitrobenzyl alcohol was used as matrix. Melting
points are uncorrected. Optical rotations were measured in a
thermostated polarimeter with l ) 1 dm. With exception of
the compounds given below, all reagents were purchased from
commercial suppliers and used without further purification.
Diethylamine was distilled from KOH under argon. (R)-(-)-
Methyl (1-naphthyl)phenylphosphinite borane (2a ) and (R)-
(-)-methyl (2-biphenylyl)phenylphosphinite borane (2b) were
prepared as previously described.11 Diisopropylamidomagne-
sium bromide was synthesized according to a literature
protocol.18
) 0.9 Hz); 129.60 (d, CH, J CP ) 3.8 Hz); 129.76 (d, CH, J CP
)
3.8 Hz); 132.75 (CH); 134.27 (d, CH, J CP ) 20.6 Hz); 138.20
(d, C, J CP ) 8.4 Hz); 138.93 (d, C, J CP ) 14.5 Hz); 141.73 (d, C,
J CP ) 5.4 Hz); 146.72 (d, C, J CP ) 24.5 Hz) ppm. 31P NMR
20
(161.98 MHz): δ -21.36 (s) ppm. [R]D ) +71.7 (c 0.45; CH2-
Cl2). HRMS (EI+): m/z calcd 446.0887; obsd 446.0875. Anal.
Calcd for C28H23FeP: C, 75.35; H, 5.19. Found: C, 75.36; H,
5.47.
Syn th esis of F er r ocen ylp h osp h in e Oxid es 4 (Typ ica l
P r oced u r e). The respective phosphinoferrocene 3 (20 mmol)
was suspended in 200 mL of acetone and cooled on an ice bath.
H2O2 (8.3 mL of a 30% solution in H2O) was added dropwise,
and the reaction mixture was stirred for 30 min while warming
to room temperature. Then it was quenched with saturated
Na2S2O3 solution, followed by extraction with CH2Cl2. The
combined organic phases were washed with H2O, dried over
MgSO4, and filtrated, and the solvent was removed in vacuo.
The crude product was purified by filtration over a short
column of alumina, using 4:1 ethyl acetate/hexane as eluent.
(R)-(+)-1-Na p h t h ylp h en ylp h osp h in oxyfer r ocen e, 4a .
1
Yield: 98%. Mp: 152 °C. H NMR (400.13 MHz): δ 4.08 (m,
1H); 4.22 (s, 5H); 4.44 (m, 1H); 4.54 (m, 1H); 4.69 (m, 1H);
7.34-7.50 (m, 6H); 7.55 (ddd, 1H, J ) 1.0, 7.0, 16.0 Hz); 7.71-
7.76 (m, 2H); 7.81 (d, 1H, J ) 8.0 Hz); 7.93 (d, 1H, J ) 8.0
Hz); 8.55 (d, 1H, J ) 8.6 Hz) ppm. 13C NMR (100.62 MHz): δ
69.75 (5CH); 71.31 (d, CH, J CP ) 10.7 Hz); 71.92 (d, CH, J CP
Syn th esis of F er r ocen ylp h osp h in es 3 (Typ ica l P r oce-
d u r e). Ferrocene (75 mmol) was dissolved in 70 mL of THF
and degassed by three freeze-pump-thaw cycles. After cooling
to 0 °C, tert-BuLi (60 mmol of a 1.7 M solution in pentane)
was added dropwise via syringe, and the reaction was kept
stirring for 15 min. A degassed solution of the respective
phosphinite borane 2 (30 mmol) in 60 mL of THF was cooled
) 10.7 Hz); 72.28 (d, CH, J CP ) 11.5 Hz); 72.83 (d, CH, J CP
13.8 Hz); 73.60 (d, C, J CP ) 120.1 Hz); 124.08 (d, CH, J CP
)
)
14.5 Hz); 126.17 (CH); 126.90 (CH); 127.40 (d, CH, J CP ) 5.4
Hz); 128.21 (d, CH, J CP ) 12.2 Hz); 128.56 (d, CH, J CP ) 1.4
Hz); 130.86 (d, C, J CP ) 103.9 Hz); 131.06 (d, CH, J CP ) 10.7
Hz); 131.40 (d, CH, J CP ) 2.3 Hz); 132.72 (d, CH, J CP ) 4.0
(35) Dierkes, P.; van Leeuwen, P. W. N. M. J . Chem. Soc., Dalton
Trans. 1999, 1519.

Diastereoselective Ortho-Metalation
Organometallics, Vol. 19, No. 12, 2000 2307
Hz); 133.18 (C), 133.24 (d, CH, J CP ) 10.7 Hz); 133.75 (d, C,
J CP ) 9.2 Hz); 134.49 (d, C, J CP ) 104.8 Hz) ppm. 31P NMR
Hz); 133.77 (d, CH, J CP ) 11.5 Hz); 140.23 (d, C, J CP ) 3.8
Hz); 147.18 (d, C, J CP ) 9.2 Hz) ppm. 31P NMR (121.50 MHz):
20
20
(121.50 MHz): δ 32.29 (s) ppm. [R]D ) +110.3 (c 0.23; CH2-
δ 29.41 (s) ppm. [R]D ) +33.8 (c 0.32; CH2Cl2). HRMS (EI+):
Cl2). HRMS (EI+): m/z calcd 436.0679; obsd 436.0681. Anal.
Calcd for C26H21FeOP: C, 71.58; H, 4.85. Found: C, 71.28; H,
5.16.
m/z calcd 587.9802; obsd 587.9814. Anal. Calcd for C28H22-
FeIOP: C, 57.18; H, 3.77. Found: C, 57.17; H, 3.93.
Syn t h esis of Bis(d ia r ylp h osp h in oxy)bifer r ocen yls 6
(Typ ica l P r oced u r e). In a Schlenk tube, ortho-iodophosphine
oxide 5 (2 mmol) was dissolved in CH2Cl2, and copper powder
(R)-(+)-2-Bip h en ylylp h en ylp h osp h in oxyfer r ocen e, 4b.
1
Yield: 98%. Mp: 169-170 °C. H NMR (400.13 MHz): δ 3.92
36
(m, 1H); 3.97 (s, 5H); 4.35 (m, 1H); 4.49 (m, 1H); 4.79 (m, 1H);
(10 mmol, activated with HCl/I2 was added under stirring.
7.01-7.12 (m, 5H); 7.16-7.27 (m, 4H); 7.31-7.45 (m, 5H) ppm.
The solvent was evaporated and the residue was heated to 135
°C for 48 h. After this treatment, the caked product was
agitated with CH2Cl2, filtrated, and concentrated. Column
chromatography (SiO2; 4:1 CH2Cl2/ethyl acetate for 6a ; 5:3:2
CH2Cl2/hexane/ethyl acetate for 6b) eluted unreacted starting
material or meso-configurated (by)product first, followed by
the desired diphosphine dioxides 6a or 6b.
13C NMR (100.62 MHz): δ 69.53 (5CH); 71.37 (d, CH, J CP
)
9.9 Hz); 71.52 (d, CH, J CP ) 1.5 Hz); 71.64 (d, CH, J CP ) 1.5
Hz); 72.86 (d, CH, J CP ) 9.9 Hz); 73.24 (d, C, J CP ) 119.3 Hz);
126.18 (d, CH, J CP ) 12.2 Hz); 126.83 (CH); 126.92 (CH);
127.51 (d, CH, J CP ) 12.2 Hz); 130.13 (CH); 130.43 (d, CH,
J CP ) 9.9 Hz); 130.56 (d, CH, J CP ) 2.3 Hz); 131.08 (d, CH,
J CP ) 3.0 Hz); 131.41 (d, CH, J CP ) 9.9 Hz); 133.34 (d, CH,
J CP ) 12.2 Hz); 133.65 (d, C, J CP ) 14.5 Hz); 134.70 (d, C, J CP
(RP ,Rm ,Rm ,RP )-(-)-2,2′-Bis(1-n a p h t h ylp h en ylp h osp h i-
n oxy)-1,1′-bifer r ocen yl, 6a . Yield: 58%. Mp: 230 °C (dec).
1H NMR (400.13 MHz): δ 3.85 (m, 2H), 4.19 (s, 10H); 4.53 (m,
2H); 5.37 (m, 2H); 5.83 (dt, 2H, J ) 2.5, 7.8 Hz); 6.85 (dd, 2H,
J ) 7.0, 16.1 Hz); 7.18-7.26 (m, 4H); 7.31-7.41 (m, 8H); 7.56-
7.63 (m, 6H); 8.42 (d, 2H, J ) 8.6 Hz) ppm. 13C NMR (100.62
MHz): δ 70.47 (5CH); 70.51 (d, CH, J CP ) 11.1 Hz); 72.75 (d,
C, J CP ) 119.3 Hz); 72.77 (d, CH, J CP ) 13.8 Hz); 81.11 (d,
CH, J CP ) 9.2 Hz); 88.17 (d, C, J CP ) 9.2 Hz); 123.74 (d, CH,
J CP ) 14.5 Hz); 125.70 (CH); 126.43 (CH); 127.56 (d, CH, J CP
) 6.1 Hz); 127.94 (d, CH, J CP ) 11.5 Hz); 128.00 (d, CH, J CP
) 10.7 Hz); 140.40 (d, C, J CP ) 4.6 Hz); 146.95 (d, C, J CP ) 9.2
Hz) ppm. 31P NMR (121.50 MHz): δ 30.52 (s) ppm. [R]D
)
20
+106.4 (c 0.64; CH2Cl2). HRMS (EI+): m/z calcd 462.0836; obsd
462.0832. Anal. Calcd for C28H23FeOP: C, 72.75; H, 5.01.
Found: C, 72.87; H, 5.11.
Syn th esis of or th o-Iod ofer r ocen ylp h osp h in e Oxid es 5
(Typ ica l P r oced u r e). Phosphine oxide 4a or 4b (15 mmol)
was dissolved in 180 mL of THF, degassed, and cooled to 0
°C. Diisopropylamidomagnesium bromide (60 mmol) was
added slowly via syringe, and the reaction mixture was allowed
to reach room temperature. After 3 h, the solution was cooled
to -30 °C, and a degassed iodine solution (45 mmol of I2 in 60
mL of THF) was added via a cannula. After warming to
ambient temperature overnight, the reaction mixture was
quenched with H2O and THF was evaporated. The residue was
extracted with CH2Cl2, and the combined organic layers were
washed with saturated sodium bisulfite solution and water,
dried over MgSO4, and concentrated. The crude product was
purified by column chromatography (SiO2; 5:1CH2Cl2/ethyl
acetate), upon which the predominantly formed diastereomers
of 5a and 5b, respectively, were eluted first, followed by a
second diastereomer and starting material.
) 1.3 Hz); 130.03 (d, C, J CP ) 104.8 Hz); 130.94 (d, CH, J CP
11.8 Hz); 130.96 (d, CH, J CP ) 3.8 Hz); 131.70 (d, CH, J CP
)
)
2.3 Hz); 132.75 (d, C, J CP ) 8.4 Hz); 133.20 (d, C, J CP ) 9.2
Hz); 133.86 (d, CH, J CP ) 11.5 Hz); 136.01 (d, C, J CP ) 104.0
20
Hz) ppm. 31P NMR (161.98 MHz): δ 32.64 (s) ppm. [R]D
)
-295.4 (c 0.54; CH2Cl2). MS (FD): m/z obsd 870.3 (M+). Anal.
Calcd for C52H40Fe2O2P2: C, 71.75; H, 4.63. Found: C, 71.97;
H, 4.99.
(RP ,Rm ,Rm ,RP )-(-)-2,2′-Bis(2-bip h en ylylp h en ylp h osp h i-
n oxy)-1,1′-bifer r ocen yl, 6b. Yield: 70%. Mp: 175-177 °C
(dec). 1H NMR (400.13 MHz): δ 3.92 (m, 2H); 3.96 (s, 10H);
4.53 (m, 2H); 5.18 (m, 2H); 6.51 (m, 2H); 6.93 (m, 4H); 6.98-
7.02 (m, 6H); 7.10-7.19 (m, 8H); 7.24-7.31 (m, 8H) ppm. 13C
NMR (100.62 MHz): δ 70.13 (5CH); 70.62 (d, CH, J CP ) 10.7
Hz); 71.81 (d, CH, J CP ) 13.8 Hz); 73.98 (d, C, J CP ) 119.3
Hz); 80.82 (d, CH, J CP ) 9.2 Hz); 89.12 (d, C, J CP ) 9.2 Hz);
125.72 (d, CH, J CP ) 12.2 Hz); 126.53 (CH); 126.91 (CH);
127.28 (d, CH, J CP ) 11.7 Hz);130.27 (d, CH, J CP ) 11.5 Hz);
130.28 (d, CH, J CP ) 8.4 Hz); 130.33 (CH); 130.56 (d, CH, J CP
(RP ,Sm )-(+)-1-Iod o-2-(1-n a p h th ylp h en ylp h osp h in oxy)-
fer r ocen e, 5a (Ma in P r od u ct). Yield: 62%. Mp: 196-197
°C. 1H NMR (400.13 MHz): δ 3.77 (m, 1H); 4.37 (m, 1H); 4.41
(s, 5H); 4.83 (m, 1H); 7.36-7.52 (m, 7H); 7.70-7.77 (m, 2H);
7.83 (d, br, 1H, J ) 8.0 Hz); 7.96 (d, br, 1H, J ) 7.5 Hz); 8.66
(d, br, 1H, J ) 8.0 Hz) ppm. 13C NMR (100.62 MHz): δ 41.79
(d, C, J CP ) 10.1 Hz); 71.76 (d, CH, J CP ) 9.9 Hz); 72.82 (5CH);
74.60 (d, CH, J CP ) 15.3 Hz); 75.92 (d, C, J CP ) 120.0 Hz);
80.00 (d, CH, J CP ) 8.4 Hz); 124.07 (d, CH, J CP ) 13.8 Hz);
126.25 (CH); 127.10 (CH); 127.65 (d, CH, J CP ) 5.4 Hz); 128.15
(d, CH, J CP ) 11.5 Hz); 128.52 (d, CH, J CP ) 1.6 Hz); 129.19
(d, C, J CP ) 105.7 Hz); 131.46 (d, CH, J CP ) 9.9 Hz); 131.57
(d, CH, J CP ) 3.1 Hz); 132.84 (d, CH, J CP ) 3.1 Hz); 133.35 (d,
CH, J CP ) 10.7 Hz); 133.55 (d, C, J CP ) 8.4 Hz); 133.72 (d, C,
J CP ) 105.5 Hz); 133.91 (d, C, J CP ) 9.2 Hz) ppm. 31P NMR
) 2.8 Hz); 130.58 (d, CH, J CP ) 9.2 Hz); 133.55 (d, C, J CP
103.3 Hz); 135.53 (d, C, J CP ) 105.6 Hz); 136.02 (d, CH, J CP
)
)
12.2 Hz); 140.71 (d, C, J CP ) 4.6 Hz); 146.38 (d, C, J CP ) 9.2
20
Hz) ppm. 31P NMR (161.98 MHz): δ 31.88 (s) ppm. [R]D
-134.6 (c 0.69; CH2Cl2). HRMS (FAB+): m/z calcd for C56H45
Fe2O2P2 (MH+): 923.1594; obsd 923.1573. Anal. Calcd for
)
-
C
56H44Fe2O2P2: C, 72.90; H, 4.81. Found: C, 72.51; H, 4.99.
Syn th esis of Bis(diar ylph osph in o)bifer r ocen yls 1 (Typi-
ca l P r oced u r e). In a glass tube, diphosphine dioxide 6a or
6b (0.6 mmol) was suspended in 9 mL of toluene. Trichlorosi-
lane (30 mmol) and triethylamine (45 mmol) were added
consecutively, and the tube was sealed under vacuum. Then
it was placed into an autoclave and heated at 140 °C for 72 h.
After cooling in liquid nitrogen, the tube was opened and the
reaction mixture was treated with 15 N NaOH solution. The
crude product was extracted with CH2Cl2; the combined
organic layers were washed with H2O, dried, and filtered, and
the solvent was evaporated. The residue was dissolved in 15
mL of THF, and BH3‚THF (1 mL, 1M in THF) was added via
syringe. Complexation was followed by TLC, and after comple-
tion, THF was removed in vacuo. The residual diphosphine
diborane was chromatographed over SiO2, using 1:1 CH2Cl2/
20
(121.50 MHz): δ 32.07 (s) ppm. [R]D ) +49.6 (c 0.52; CH2-
Cl2). HRMS (EI+): m/z calcd 561.9646; obsd 561.9652. Anal.
Calcd for C26H20FeIOP: C, 55.55; H, 3.59. Found: C, 55.28;
H, 3.52.
(RP ,Sm )-(+)-1-Iodo-2-(2-biph en ylylph en ylph osph in oxy)-
fer r ocen e, 5b. Yield: 86%. Mp: 160 °C (dec). 1H NMR (400.13
MHz): δ 3.75 (m, 1H); 4.15 (s, 5H); 4.29 (m, 1H); 4.78 (m, 1H);
6.98-7.11 (m, 5H); 7.18-7.26 (m, 3H); 7.29-7.36 (m, 4H);
7.42-7.52 (m, 2H) ppm. 13C NMR (100.62 MHz): δ 42.36 (d,
C, J CP ) 9.9 Hz); 72.05 (d, CH, J CP ) 9.9 Hz); 72.66 (5CH);
73.57 (d, CH, J CP ) 14.5 Hz); 74.72 (d, C, J CP ) 118.6 Hz);
79.89 (d, CH, J CP ) 9.2 Hz); 126.37 (d, CH, J CP ) 12.2 Hz);
126.80 (CH); 126.84 (CH); 127.48 (d, CH, J CP ) 12.2 Hz);
130.32 (CH); 130.78 (d, CH, J CP ) 2.3 Hz); 131.01 (d, CH, J CP
) 9.9 Hz); 131.23 (d, CH, J CP ) 2.3 Hz); 131.64 (d, CH, J CP
)
9.9 Hz), 132.87 (d, C, J CP ) 105.5 Hz); 133.58 (d, C, J CP ) 107.9
(36) Kleiderer, E. C.; Adams, R. J . Am. Chem. Soc. 1933, 55, 4225.

2308 Organometallics, Vol. 19, No. 12, 2000
Nettekoven et al.
Ta ble 2. Deta ils of Cr ysta l Str u ctu r e Deter m in a tion s for Com p ou n d s 6b, m eso-6b, a n d 6a
6b
meso-6b
6a
a
formula
fw
C
56H44Fe2O2P2‚2CH2Cl2
C56H44Fe2O2P2
922.55
Bruker SMART
0.71073
296(2)
triclinic
P1h
8.289(4)
9.607(5)
14.485(7)
108.55(1)
90.84(1)
96.99(1)
1083.7(9)
1
C52H40Fe2O2P2
870.48
Bruker SMART
0.71073
299(2)
monoclinic
P21/c
14.861(3)
16.076(4)
17.451(5)
90
90.170(10)
90
4169.1(18)
4
1.387
0.814
0.70 × 0.14 × 0.14
SADABS
0.75-0.96
0.00025(8)
0.59
0.0312
0.0684
0.0468
0.0771
1092.40
Bruker SMART
0.71073
213(2)
orthorhombic
P212121
9.620(4)
12.430(5)
43.31(2)
90
90
90
5179(4)
4
1.401
diffractometer
wavelength (Å)
temperature (K)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
density (g cm-3
)
1.414
0.788
µ (mm-1
)
0.871
crystal size (mm3)
abs corr
0.70 × 0.65 × 0.45
SADABS
0.63-0.75
0.00047(9)
0.64
0.0414
0.0846
0.0434
0.0854
0.22 × 0.10 × 0.07
XABS2
transmission
extinction coeff
0.78-1.37
(sin θ/λ)max (Å-1
R1 (I > 2σ(I))
wR2 (I > 2σ(I))
R1 (all data)
wR2 (all data)
GooF
)
0.59
0.0499
0.0906
0.0889
0.1077
1.092
1.185
1.058
Flack x
0.019(12)
a
Structure 6b contains partly disordered CH2Cl2 molecules. Solvent content idealized in chemical formula, formula weight, density,
and absorption coefficient.
Ta ble 3. Deta ils of Cr ysta l Str u ctu r e Deter m in a tion s for Com p ou n d s 1a , 8c, a n d 8a
1a
8c
8a
a
formula
fw
C
52H40Fe2P2‚2CH2Cl2
C42H32Cl2FeP2Pt‚CH2Cl2
C52H40Cl2Fe2P2Ptb
1104.47b
Nonius KappaCCD
0.71073
150(2)
orthorhombic
P212121
11.8381(3)
19.7931(5)
20.8439(5)
90
90
90
1004.30
Bruker SMART
0.71073
213(2)
orthorhombic
Pbcn
16.392(8)
17.161(8)
16.522(8)
90
90
90
4648(4)
4
1.435
1005.38
Enraf-Nonius CAD4T
0.71073
150(2)
diffractometer
wavelength (Å)
temperature (K)
cryst syst
space group
a (Å)
orthorhombic
P212121
11.6781(12)
17.166(2)
18.737(2)
90
b (Å)
c (Å)
R (deg)
â (deg)
90
90
γ (deg)
V (Å3)
3756.1(7)
4
1.778
4884.0(2)
4
Z
density (g cm-3
)
1.502a
µ (mm-1
)
0.960
4.509
3.651a
cryst size (mm3)
abs corr
0.30 × 0.20 × 0.20
SADABS
0.69-0.86
0.00049(8)
0.64
0.0363
0.0813
0.0429
0.0847
0.41 × 0.20 × 0.18
DELABS
0.47-0.83
0.45 × 0.45 × 0.10
MULABS
0.53-0.70
transmission
extinction coeff
(sin θ/λ)max (Å-1
R1 (I > 2σ(I))
wR2 (I > 2σ(I))
R1 (all data)
wR2 (all data)
GooF
)
0.65
0.65
0.0320
0.0598
0.0406
0.0623
1.026
0.0413
0.1031
0.0476
0.1063
1.041
1.121
Flack x
-0.017(5)
-0.020(5)
a
Structure 1a contains partly disordered CH2Cl2 molecules. Solvent content idealized in chemical formula, formula weight, density,
b
and absorption coefficient. Structure 8a contains disordered CH2Cl2 molecules. Their contribution to the calculated structure factors
was calculated with the routine CALC SQUEEZE of the program PLATON (339 electrons/unit cell).39 The solvent is not included in
formula weight, density, and absorption coefficient.
hexane as eluent. The desired C2-symmetrical product was
eluted first, followed by unseparated isomerized byproducts.
(SP ,Rm,Rm,SP )-(-)-2,2′-Bis(1-n aph th ylph en ylph osph in o)-
1,1′-bifer r ocen yl, 1a . Deprotection was performed by stirring
the diborane complex of 1a in degassed Et2NH (15 mL) at room
temperature. After 5 h, TLC showed complete conversion. The
reaction mixture was concentrated, and the crude diphosphine
was chromatographed (SiO2, 1:1 CH2Cl2/hexane), to afford the
enantiopure ligand as orange crystals. Yield: 40%. Mp: 236-
1
238 °C (dec). H NMR (400.13 MHz; CD2Cl2): δ 3.90 (m, 2H);
4.12 (s, 10H); 4.52 (dt, 2H, J ) 0.6, 2.6 Hz); 5.01 (m, 2H); 5.88
(m, 2H); 6.41 (m, 2H); 7.10 (d, br, 2H, J ) 8.2 Hz); 7.22-7.36
(m, 10H); 7.43-7.48 (m, 4H); 7.65 (dd, br, 2H, J ) 0.6, 8.0
Hz); 8.03 (ddd, br, 2H, J ) 1.0, 3.5, 8.6 Hz) ppm. 13C NMR

Diastereoselective Ortho-Metalation
Organometallics, Vol. 19, No. 12, 2000 2309
(100.62 MHz; CD2Cl2): δ 70.10 (CH); 70.14 (5CH); 72.22 (d,
CH, J CP ) 4.6 Hz); 77.00 (d, CH, J CP ) 11.5 Hz); 77.93 (d, C,
J CP ) 9.2 Hz); 91.05 (dd, C, J CP ) 2.2, 29.1 Hz); 124.66 (CH);
125.02 (CH); 125.10 (d, CH, J CP ) 2.3 Hz); 126.15 (d, CH, J CP
) 24.5 Hz); 127.94 (CH); 127.98 (d, CH, J CP ) 7.9 Hz); 128.17
(d, CH, J CP ) 1.4 Hz); 128.84 (CH); 130.87 (CH); 133.03 (d, C,
J CP ) 3.8 Hz); 133.61 (d, C, J CP ) 19.9 Hz); 134.69 (d, CH, J CP
was filtrated, washed with hexane, and dried under vacuum.
Recrystallization from CH2Cl2/hexane gave crystals suitable
for crystal structure determination.
[(SP ,Rm ,Rm ,SP )-2,2′-Bis(1-n a p h t h ylp h en ylp h osp h in o)-
1,1′-bifer r ocen yl]d ich lor op la tin u m (II), 8a . Yield: 63%. 1H
NMR (400.13 MHz; CD2Cl2): δ 3.31 (m, 2H); 4.02 (s, 10H);
4.15 (m, 2H); 4.99 (m, 2H); 7.18-8.00 (m, 18H); 8.70 (dd, 4H,
J ) 0.9; 2.0 Hz); 8.84 (d, 2H, J ) 2.2 Hz) ppm. 31P NMR (161.98
MHz; CD2Cl2): δ -6.21 (t, J PPt ) 1758 Hz) ppm. Anal. Calcd
for C52H40Cl2Fe2P2Pt: C, 56.55; H, 3.65. Found: C, 56.34; H,
3.82.
[(SP ,SP )-(1,1′)-Bis(1-n a p h t h ylp h en ylp h osp h in o)fer r o-
cen e]d ich lor op la tin u m (II), 8c. Yield: 72%. 1H NMR (400.13
MHz; CD2Cl2): δ 4.19 (m, 4H, fc); 4.32 (m, 2H, fc); 4.53 (m,
2H, fc); 7.28 (ddd, 2H, J ) 1.2; 6.8; 8.3 Hz, naphthyl-H7); 7.37-
7.43 (m, 4H, phenyl-H3,5); 7.47-7.58 (m, 6H, phenyl-H4,
naphthyl-H3, naphthyl-H6); 7.90 (m, 4H, phenyl-H2,6); 7.96
(d, 2H, J ) 8.3 Hz, naphthyl-H5); 8.09 (d, 2H, J ) 8.2 Hz,
naphthyl-H4); 8.41 (d, br, 2H, J ) 8.4 Hz, naphthyl-H8); 8.61
(dd, br, 2H, J ) 7.6; 16.7 Hz, naphthyl-H2) ppm. 31P NMR
(161.98 MHz; CD2Cl2): δ 13.49 (t, J PPt ) 1926 Hz) ppm. Anal.
Calcd for C42H32Cl2FeP2Pt: C, 54.80; H, 3.50. Found: C, 54.44;
H, 3.56.
) 21.4 Hz); 135.79 (d, C, J CP ) 13.8 Hz); 138.13 (d, C, J CP
)
7.7 Hz) ppm. 31P NMR (161.98 MHz; CD2Cl2): δ -30.60 (s)
ppm. [R]D20 ) -175.7 (c 0.44; CH2Cl2). MS (FD): m/z obsd 838.5
(M+). Anal. Calcd. for C52H40Fe2P2: C, 74.48; H, 4.81. Found:
C, 74.20; H, 4.92.
(SP ,Rm ,Rm ,SP )-(+)-2,2′-Bis(2-bip h en ylylp h en ylp h osp h i-
n o)-1,1′-bifer r ocen yl, 1b. Since in the case of 1b‚(BH3)2 the
decomplexation procedure with Et2NH resulted in up to 15%
epimerization of chiral phosphorus, an acidic deprotection
method was employed, which proved to proceed without any
observable degree of isomerization. A solution of the diborane
complex (1 mmol) in 8 mL of toluene was degassed and cooled
in an ice bath, and trifluoromethanesulfonic acid (5 mmol) was
added slowly via syringe. After 30 min, stirring was continued
at room temperature until TLC indicated complete protona-
tion. The solvent was removed, and the residue was treated
with a solution of 10 mmol of KOH in 3 mL of degassed 10:1
EtOH/H2O. The suspension was stirred for 30 min at ambient
temperature, after which degassed Et2O (7 mL) was added.
The upper layer was transferred in a second Schlenk tube by
Teflon cannula, and this extraction was repeated twice. The
combined ether layers were dried over Na2SO4, concentrated,
and subjected to column chromatography (alumina; 1:1 CH2-
Cl2/hexane). Evaporation of the eluent left enantiopure ligand
Cr ysta l Str u ctu r e Deter m in a tion s. Structures 6b, meso-
6b, 6a , and 1a were solved using direct methods (SHELXS-
97).37 Structures 8a and 8c were solved with Patterson
methods (DIRDIF-97).38 All structures were refined with
SHELXL-97 against F2 of all reflections. Further details of the
structure determinations are included in Tables2 and 3.
Ack n ow led gm en t. We are grateful to the IOP
Katalyse program of the Netherlands Ministry of Eco-
nomic Affairs (Project IKA 94081) for financial support
and a special grant to U.N. Part of this work (M.L. and
A.L.S.) was financially supported by the Council for
Chemical Sciences of The Netherlands Organization for
Scientific Research (CW-NWO).
1
1b as yellow powder. Yield: 44%. Mp: 150-151 °C. H NMR
(400.13 MHz): δ 3.90 (m, 2H); 3.99 (s, 10H); 4.37 (m, 2H); 4.58
(m, 2H); 6.75 (m, 2H); 6.83 (m, 2H); 7.00-7.04 (m, 8H); 7.16-
7.29 (m, 16H) ppm. 13C NMR (100.62 MHz): δ 69.28 (CH);
70.57 (d, 5CH, J CP ) 1.5 Hz); 71.96 (d, CH, J CP ) 4.6 Hz); 76.71
(dd, CH, J CP ) 4.6, 8.4 Hz); 77.28 (d, C, J CP ) 15.0 Hz); 91.10
(dd, C, J CP ) 2.0, 28.5 Hz); 126.56 (d, CH, J CP ) 3.1 Hz); 127.33
(CH); 127.38 (d, CH, J CP ) 10.7 Hz); 127.46 (CH); 127.49 (d,
CH, J CP ) 8.4 Hz); 128.29 (CH); 129.19 (d, CH, J CP ) 3.8 Hz);
129.54 (d, CH, J CP ) 3.8 Hz); 132.52 (CH); 134.95 (d, CH, J CP
Su p p or tin g In for m a tion Ava ila ble: NMR and MS data
of the minor isomer of 5a and meso-6b, crystal structure
refinement data for compounds 6a , 6b, meso-6b, 1a , 8a , and
8c, including atomic coordinates, isotropic and anisotropic
displacement parameters, and a complete listing of bond
angles and bond distances. This material is available free of
charge via the Internet at http://pubs.acs.org.
) 22.2 Hz); 138.77 (d, C, J CP ) 10.7 Hz); 138.80 (d, C, J CP
)
17.6 Hz); 142.08 (d, C, J CP ) 4.6 Hz); 145.77 (d, C, J CP ) 23.7
Hz) ppm. 31P NMR (161.98 MHz): δ -28.36 (s) ppm. [R]D
)
20
+6.3 (c 0.25; CH2Cl2). HRMS (FAB+): m/z calcd for C56H45Fe2P2
(MH+): 891.1695; obsd 891.1686. Anal. Calcd for C56H44
Fe2P2: C, 75.52; H, 4.98. Found: C, 75.37; H, 5.36.
-
OM991013S
Syn th esis of P la tin u m Com p lexes 8 (Typ ica l P r oce-
d u r e). Bis(benzonitrile)dichloroplatinum(II) (0.1 mmol) was
dissolved in 15 mL of degassed benzene and heated to 70 °C.
A solution of diphosphine 1 (0.11 mmol) in 10 mL of benzene
was slowly added via a Teflon cannula, and the resulting
mixture was kept at reflux temperature for 1 h. Upon cooling
and, eventually, concentrating, a red precipitate formed, which
(37) Sheldrick, G. M. SHELXL-97. Program for Crystal Structure
Refinement; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(38) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIF Program System, Technical Report of the Crystallography
Laboratory; University of Nijmegen, Nijmegen, The Netherlands, 1997.
(39) Spek, A. L. PLATON. A multipurpose crystallographic tool;
Utrecht University: The Netherlands, 1999.