Optically active asymmetric di(tertiary phosphines). Crystal and molecular structure of [SP-4-3-(Sp,S)]-{1-[(2-chlorophenyl)-methylphosphino]-2- (dimethylphosphino)benzene-P,P′}{1-[1-(dimethylamino)ethyl]naphthyl-C 2,N}palladium(II)

Article abstract of DOI:10.1039/b101182k

Mono-deprotonation of the bis(secondary phosphine) (R_p*,R_p*)- and (R_p*,S_p*)-1,2-phenylenebis(methylphosphine) has been achieved using potassium in liquid ammonia to give a ca. 4 : 1 mixture of (±)-1-(dimethylpho

Full text of DOI:10.1039/b101182k

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Optically active asymmetric di(tertiary phosphines). Crystal and
molecular structure of [SP-4-3-(SP,S)]-{1-[(2-chlorophenyl)-
methylphosphino]-2-(dimethylphosphino)benzene-P,PЈ}{1-[1-
(dimethylamino)ethyl]naphthyl-C2,N}palladium(II)
hexafluorophosphate
Swarup Chatterjee,a Mark D. George,a Geoffrey Salem*a and Anthony C. Willisb
a Chemistry Department, The Faculties, Australian National University, Canberra,
A. C. T. 0200, Australia. E-mail: Geoff.Salem@anu.edu.au
b Research School of Chemistry, Australian National University, Canberra, A. C. T. 0200,
Australia
Received 6th February 2001, Accepted 17th April 2001
First published as an Advance Article on the web 23rd May 2001
Mono-deprotonation of the bis(secondary phosphine) (RP*,RP*)- and (RP*,SP*)-1,2-phenylenebis(methylphosphine)
has been achieved using potassium in liquid ammonia to give a ca. 4 : 1 mixture of ( )-1-(dimethylphosphino)-2-
(methylphosphino)benzene and 1,2-phenylenebis(dimethylphosphine) upon addition of a solution of methyl
iodide in the same solvent. This mixture has been further treated with sodium in THF followed by the addition
of 1,2-dichlorobenzene to give ( )-(2-chlorophenyl)(2-dimethylphosphinophenyl)methylphosphine and unchanged
1,2-phenylenebis(dimethylphosphine). The two di(tertiary phosphines) are readily separated by fractional distillation.
Asymmetric di(tertiary phosphine) ( )-(2-chlorophenyl)(2-dimethylphosphinophenyl)methylphosphine has been
resolved by separation via fractional crystallisation of internally diastereomeric palladium() complexes containing
the racemic ligand and orthometallated (S)-dimethyl[1-(1-naphthyl)ethyl]amine. The absolute configuration of the R
enantiomer of the ligand has been assigned by a crystal structure determination of the least soluble diastereomeric
palladium() complex [SP-4-3-(SP,S)]{1-[(2-chlorophenyl)methylphosphino]-2-(dimethylphosphino)benzene-
P,PЈ}{1-[1-(dimethylamino)ethyl]naphthyl-C2,N}palladium() hexafluorophosphate.
Resolution via the method of metal complexation has
arguably proven to be the most successful route to optically
active bidentate ligands containing stereogenic arsenic or phos-
phorus donor atoms. The method involves the separation by
fractional crystallisation of a pair of internally diastereomeric
palladium() complexes containing the racemic ligand and
an orthometallated optically active amine, typically (S)- or
(R)-dimethyl(1-phenylethyl)amine or (S)- or (R)-dimethyl-
[1-(1-naphthyl)ethyl]amine.1 The potency of the method is no
better illustrated than in the resolution of the dissymmetric
di(tertiary phosphine) (RP*,RP*)-1,2-phenylenebis(methyl-
phenylphosphine).2 Reaction of the racemic ligand with the
chloro-bridged dimer bis(µ-chloro)bis{(S)-2-[1-(dimethyl-
amino)ethyl]phenyl-C1,N}dipalladium() in methanol followed
by the addition of one equivalent of aqueous ammonium
hexafluorophosphate gave a single diastereomeric complex.
Subsequent treatment of both the isolated diastereomerically
pure solid and the diastereomerically enriched filtrate with con-
centrated hydrochloric acid in methanol followed by cyanolysis
gave the optically pure antipodes in ca. 90% yield upon
chiral bidentate ligands ( )-2,2Ј-diphenylphosphino-1,1Ј-
binaphthyl and ( )-[(1-isoquinolyl)naphthyl]diphenylphos-
phine;7 and more recently the quadridentate ligand (RP*,RP*)-
1,2-bis{(diphenylphosphinoethyl)phenylphosphino}ethane.8
We have also shown that the method of complexation provides
a viable method of resolution for the asymmetric di(tertiary
phosphines) ( )-1-(diphenylphosphino)-2-(methylphenylphos-
phino)benzeneand( )-1-(diphenylphosphino)-2-(methylphenyl-
phosphino)ethane.9,10
In this paper we describe the preparation and resolution of
the related asymmetric di(tertiary phosphine) ( )-(2-chloro-
phenyl)(2-dimethylphosphinophenyl)methylphosphine.
The
presence of the 2-chlorophenyl group allows for further deriv-
atisation of the ligand. For example, the related bidentate
ligand (RP)-(2-aminophenyl)(2-chlorophenyl)methylphosphine
was previously shown to react with sodium (2-dimethyl-
arsinophenyl)methylarsenide to form the optically active
quadridentate
ligand
(SAs,RP)-1-[(2-aminophenyl)methyl-
phosphino]-2-[(2-dimethylarsinophenyl)methylarsino]benzene
and the optically active pentadentate ligands (SAs,SAs,RP)- and
(SAs,RAs,RP)-5-amino-1,4,11,14-tetraarsino-2,3,6,7,9,10,12,13-
tetrahydrotetrabenzo-1,1,4,8,11,14,14-heptamethyl-8-phos-
phinotetradecine.11 We have published some preliminary details
on the synthesis of ( )-(2-chlorophenyl)(2-dimethylphosphino-
phenyl)methylphosphine in a recent communication.12
recrystallisation from methanol, α
89Њ (589 nm, dichloro-
methane). The methodology was subsequently extended to
include the analogous dissymmetric di(tertiary arsine)
(RAs*,RAs*)-1,2-phenylenebis(methylphenylarsine)3 and a range
of asymmetric bidentate ligands containing a single stereogenic
arsenic or phosphorus donor atom and a nitrogen or sulfur
donor atom.4 The versatility of the approach was further
demonstrated by the successful resolution of the asymmetric
bidentate ligands ( )-1-(dimethylarsino)-2-(methylphenylphos-
phino)benzene,5 and (RAs*,RP*)- and (RAs*,SP*)-1-(methyl-
phenylarsino)-2-(methylphenylphosphino)benzene;6 the axially
Results and discussion
Synthesis of ( )-1
Asymmetric di(tertiary phosphine) ( )-(2-chlorophenyl)-
1890
J. Chem. Soc., Dalton Trans., 2001, 1890–1896
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b101182k

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Scheme 1 (i) Na in THF; MeI; (ii) 2 Na in THF; MeI; (iii) 2 Na in THF; MeI; (iv) 1.2 equivalent K in NH3(l); MeI; (v) Na in THF; 1,2-C6H4Cl2.
(2-dimethylphosphinophenyl)methylphosphine, ( )-1, was pre-
pared in three steps from 1,2-phenylenebis(phosphine), 213
(Scheme 1). Deprotonation of the bis(primary phosphine) 2 by
reaction with two equivalents of n-butyllithium in THF fol-
lowed by the addition of a solution of methyl iodide in the same
solvent gave (RP*,RP*)- and (RP*,SP*)-1,2-phenylenebis-
(methylphosphine), 3, in high yield.13 The product, however,
typically contained up to ca. 20% of ( )-(2-methylphos-
phinophenyl)phosphine, 4. The latter could be minimised
(<5%) by reaction of 2 with two equivalents of sodium in THF
followed by the addition of a solution of methyl iodide in the
same solvent to give 3. Whereas this reaction is highly regio-
selective, mono-deprotonation of bis(secondary phosphine) 3 is
not. For example, reaction of 3 with one equivalent of sodium
or n-butyllithium in THF followed by the addition of a solution
of methyl iodide in the same solvent gave a mixture of three
species: unchanged 3, ( )-(2-dimethylphosphinophenyl)-
methylphosphine, 5 and 1,2-phenylenebis(dimethylphosphine),
6. The latter can be synthesized in high yield by reaction of
3 with two equivalents of sodium in THF followed by the
addition of two equivalents of methyl iodide. Alternative pre-
parative routes to 6 have been reported.14,15 The coordination
chemistry of 6 has also been investigated by Bennett and
Warren.15
Mono-deprotonation of 3 has been investigated using several
metallating agents in varying quantities ranging from ca. 0.8
to 1.5 equivalents and under variable reaction conditions. The
reactions were monitored using a combination of 31P-{1H}
NMR spectroscopy and GC-MS. The optimum conditions for
the conversion of 3 into 5 were deemed to be reaction of 3 with
ca. 1.2 equivalents of potassium in liquid ammonia followed by
the addition of methyl iodide. Under these conditions a ca. 4 : 1
mixture of 5 and 6 was isolated that contained minimal quan-
tities of 3 (<5%). Subsequent reaction of this mixture with
sodium in THF followed by the addition of 1,2-dichloro-
benzene gave the asymmetric di(tertiary phosphine) ( )-1,
unchanged 6 and small quantities (<5%) of the phosphorus
heterocycle 5,10-dimethyl-5,10-dihydrophosphanthren (9,10-
dimethyl-9,10-dihydrodiphosphanthracene) 7. The latter was
presumably formed from the coupling of doubly deprotonated
3 with 1,2-dichlorobenzene. Separation of ( )-1 and 6 was
achieved by fractional distillation. The isolation of ( )-1 in this
manner gave a product that contained small quantities of 6 and
the phosphorus heterocycle 7. The latter crystallised from solu-
tion upon dissolution of the distilled product in hot methanol.
Trace quantities of 6 were removed by reaction with hexa-
aquanickel() chloride in ethanol followed by the addition of
aqueous ammonium hexafluorophosphate. A mixture of
diastereomeric nickel() complexes containing ( )-1 was
isolated upon fractional crystallisation from dichloromethane–
diethyl ether. Pure ( )-1 was isolated from the diastereomeric
mixture of nickel() complexes by treatment with aqueous
potassium cyanide followed by distillation, in an overall yield of
1
ca. 40%. Selected H and 31P-{1H} NMR data for ( )-1–7 are
given in Table 1.
Resolution of ( )-1
The resolution of ( )-1 has been achieved via the separation
by fractional crystallisation of internally diastereomeric pal-
ladium() complexes containing the racemic ligand and an
orthometallated optically active amine, namely (S)-dimeth-
yl[1-(1-naphthyl)ethyl]amine. Reaction of ( )-1 with the
chloro-bridged dimer bis(µ-chloro)bis{(S)-1-[1-(dimethyl-
amino)ethyl]naphthyl-C2,N}dipalladium(), (S)-8, in methanol
followed by the addition of an excess of aqueous ammonium
hexafluorophosphate gave a mixture of four diastereomeric
palladium() complexes, viz. (RP,S)-9a, (SP,S)-9a, (RP,S)-9b
and (SP,S)-9b (Scheme 2). The same mixture of four
diastereomeric hexafluorophosphate salts was isolated upon the
addition of one equivalent of aqueous ammonium hexafluoro-
phosphate. Fractional crystallisation of the diastereomeric mix-
ture from chloroform–propan-2-ol resulted in the isolation of a
ca. 1 : 1 mixture of (RP,S)-9a and (SP,S)-9a. Two recrystallis-
ations of the ca. 1 : 1 mixture of (RP,S)-9a and (SP,S)-9a from
acetone–propan-2-ol gave pure (SP,S)-9a, α ϩ74Њ (589 nm,
J. Chem. Soc., Dalton Trans., 2001, 1890–1896
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Table 1 Selected 1H and 31P-{1H} NMR data for compounds ( )-1–7 in C6D6
1H
Compound
31P-{1H}, δ(P)a
δ(PH)
δ(PMe)
δ(PMe2)
( )-1
Ϫ53.6d(154)
Ϫ36.4d(154)
Ϫ124.8s
—
1.47d(5)b
1.15d(4),b 1.22d(4)b
2
3
3.84dm(207)c
—
—
—
—
—
Ϫ74.7s
Ϫ73.6s
4.23dq(216)c(7)d
1.13dt(7)d(4)e
4.37dq(213)c(7)d
1.16dt(7)d(3)e
f
f
4
5
Ϫ126.3d(71)f
Ϫ72.5d(123)
Ϫ54.4d(123)
Ϫ54.8s
4.45ddq(209)c(11)g(7)d
1.27ddd(7)d(4)b(0.6)h
1.08d(4),b 1.14d(4)b
6
7
—
—
—
1.22t(2)e
Ϫ38.2s
1.92d(4)b
a Values of 3JPP given in Hz in parentheses. b Values of 2JPH given in Hz in parentheses. c Values of 1JPH given in Hz in parentheses. d Values of 3JHH
4
given in Hz in parentheses. e Values of |2JPH ϩ 5JPЈH| given in Hz in parentheses. f Obscured by other resonances. g Value of JPЈH given in Hz in
parentheses. h Value of 5JPЈH given in Hz in parentheses.
Scheme 2 (i) MeOH; (ii) NH4[PF6] in water.
dichloromethane). The mother liquor, which was enriched in
(RP,S)-9a, was taken to dryness and the residue recrystallised
from dichloromethane–propan-2ol to give pure (RP,S)-9a, α
ϩ225Њ (589 nm, dichloromethane), albeit in low yield. Liber-
ation of the resolved asymmetric di(tertiary phosphine) from
(SP,S)-9a was accomplished as shown in Scheme 3. Diastereo-
merically pure (SP,S)-9a was dissolved in concentrated sulfuric
acid, the mixture poured onto ice and anhydrous lithium chlor-
ide added to give the dichloropalladium() compound (SP)-10,
α ϩ52Њ (589 nm, dichloromethane). Further reaction of (SP)-10
with aqueous potassium cyanide gave optically pure (RP)-1, α
ϩ33Њ (589 nm, dichloromethane). Similar treatment of the ca.
1 : 1 mixture of (RP,S)-9a and (SP,S)-9a gave ( )-1, confirm-
ation that the two diastereomeric palladium() complexes con-
tained different enantiomeric forms of the di(tertiary
phosphine).
structure determination of (SP,S)-9a. The stereochemistry of
the cation is depicted in Fig. 1. Selected bond lengths and
angles are given in Table 2. The structural data clearly show that
the absolute configurations of the stereogenic phosphorus and
carbon atoms are both S. Furthermore, the phosphorus stereo-
centre of the asymmetric di(tertiary phosphine) was found to be
coordinated trans to the NMe2 group of the orthometallated
amine. A similar arrangement has been observed in the solid
state structures of several related internally diastereomeric pal-
ladium() complexes containing an orthometallated, optically
active amine and an asymmetric bidentate ligand containing a
single phosphorus (or arsenic) stereocentre.4a,5,9–11 In most of
these cases the coordination of the bidentate ligand occurred in
a completely regioselective manner. The current ligand ( )-1
and the related di(tertiary phosphine) ( )-1-(diphenylphos-
phino)-2-(methylphenylphosphino)ethane10 are two examples
of asymmetric bidentate ligands that do not coordinate in a
completely regioselective fashion to the palladium() centre in
such complexes.
Crystal structure determination of (SP,S)-9a
The absolute configuration of (RP)-1 was assigned by a crystal
The bond lengths and angles around the palladium() centre
1892
J. Chem. Soc., Dalton Trans., 2001, 1890–1896

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Table 2 Selected non-hydrogen interatomic distances (Å) and inter-
atomic angles (Њ) for (SP,S)-9a
Pd(1)–P(1)
Pd(1)–N(1)
2.343(1)
2.146(5)
Pd(1)–P(2)
Pd(1)–C(16)
2.226(2)
2.061(4)
P(1)–Pd(1)–P(2)
P(1)–Pd(1)–C(16)
P(2)–Pd(1)–C(16)
Pd(1)–P(1)–C(1)
Pd(1)–P(1)–C(3)
Pd(1)–P(2)–C(9)
Pd(1)–N(1)–C(28)
Pd(1)–N(1)–C(29)
Pd(1)–C(16)–C(25)
85.36(7)
177.5(2)
94.4(2)
117.9(3)
107.9(3)
112.8(2)
118.5(4)
105.4(4)
112.5(5)
P(1)–Pd(1)–N(1)
P(2)–Pd(1)–N(1)
N(1)–Pd(1)–C(16)
Pd(1)–P(1)–C(2)
Pd(1)–P(2)–C(8)
Pd(1)–P(2)–C(10)
Pd(1)–N(1)–C(26)
Pd(1)–C(16)–C(17)
99.5(1)
175.1(1)
80.8(3)
117.5(2)
110.5(2)
119.3(2)
104.7(3)
129.5(6)
a single diastereomer in solution. Similarly the 1H NMR spec-
trum contained a single set of resonances including four doub-
lets for the CMe moiety and the three non-equivalent PMe
groups. Selected 1H and 31P-{1H} NMR data for (SP,S)-9a [and
for the related diastereomeric complexes (RP,S)-9a, (RP,S)-9b
and (SP,S)-9b] are given in Table 3.
Fig. 1 Molecular structure of the cation of complex (SP,S)-9a. (The
thermal ellipsoids show 30% probability levels.)
1
The presence of a doublet of doublets at δ 6.85 in the H
NMR spectrum of (SP,S)-9a provided evidence that the com-
plex retained the same regiochemistry in solution. The reson-
ance is assigned to γ-H of the naphthyl ring (i.e. the H atom
attached to C17 in Fig. 1) and occurred upfield of the other
aromatic resonances due to shielding by the 2-chlorophenyl
group of the adjacent stereogenic phosphorus atom. A similar
finding has previously been reported for related diastereomeric
palladium() complexes containing orthometallated (R)- or
(S)-dimethyl[1-(1-naphthyl)ethyl]amine and a range of asym-
metric bidentate ligands possessing a phosphorus (or arsenic)
stereocentre bearing a methyl and an aryl substituent.4a,c,6,11 In
all cases, including (SP,S)-9a, an upfield shift of γ-H was only
1
observed in the respective H NMR spectra when the methyl
groups of the stereogenic carbon atom and the trans disposed
phosphorus (or arsenic) stereocentre were in a syn arrangement
with respect to the coordination plane of the palladium()
centre. The observation of an upfield shift of the γ-H resonance
clearly provides a means of assigning absolute configurations to
complexes of this type by 1H NMR spectroscopy.1 It should be
noted that the magnitude of the upfield shift is smaller, and
hence the method of assignment is much less reliable, when the
moiety linking the donor atoms of the bidentate ligand is a 1,2-
ethylene group.4b,d,10 The γ-H resonance was also found to be
coupled to the adjacent stereogenic phosphorus atom of these
complexes in the respective 1H NMR spectra, via what is
believed to be a through-space rather than through-bond effect.
In the case of (SP,S)-9a, a value of 14 Hz for 4JPH was observed
for the γ-H resonance.
Scheme 3 (i) Concentrated H2SO4; ice, LiCl; (ii) CH2Cl2; KCN in
water.
The 1H and 31P-{1H} NMR spectra of (RP,S)-9a in
(CD3)2CO were similarly consistent with the presence of a
single diastereomer. Not unexpectedly they were very similar to
those recorded for (SP,S)-9a, the only major difference being
of (SP,S)-9a are in very close agreement with those reported
for related diastereomerically pure palladium() complexes
containing the asymmetric di(tertiary phosphines) (SP)-1-
(diphenylphosphino)-2-(methylphenylphosphino)ethane
or
1
the absence of an upfield shift for the γ-H resonance in the H
(SP)-1-(diphenylphosphino)-2-(methylphenylphosphino)-
NMR spectrum of (RP,S)-9a. Indeed, the two complexes were
assigned the same regiochemistry on the basis of the similarities
between their respective 31P-{1H} NMR spectra. The pair of
doublet phosphorus resonances had very similar chemical shifts
in the two spectra. A similar approach has previously been used
to identify the four internally diastereomeric palladium()
complexes formed in the resolution of ( )-1-(diphenyl-
phosphino)-2-(methylphenylphosphino)ethane by reaction of
the racemic ligand with (R)-8 in methanol followed by the
addition of aqueous ammonium hexafluorophosphate.10 Two
diastereomeric palladium() complexes containing the S form
of the di(tertiary phosphine) were isolated and unambiguously
characterised. The remaining pair of diastereomers had differ-
ent regiochemistries and was identified by comparison of their
31P-{1H} NMR spectra with those recorded for their counter-
benzene and orthometallated (R)-dimethyl[1-(1-naphthyl)-
ethyl]amine or (S)-dimethyl(1-phenylethyl)amine, respec-
tively.9,10 In all three complexes the Pd–P bond trans to the
metallated carbon atom was longer than that trans to the
dimethylamino group (2.34–2.38, cf. 2.22–2.25 Å). The greater
trans influence associated with the metallated carbon atom is
presumably responsible for the weakening of the trans disposed
Pd–P bond.
NMR Spectra
1
The H and 31P-{1H} NMR spectra of (SP,S)-9a in (CD3)2CO
can be rationalised in terms of its solid state structure. The
31P-{1H} NMR spectrum of the complex contained a pair of
doublet phosphorus resonances consistent with the presence of
J. Chem. Soc., Dalton Trans., 2001, 1890–1896
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Table 3 Selected 1H and 31P-{1H} NMR data for complexes (RP,S)-9a, (SP,S)-9a, (RP,S)-9b and (SP,S)-9b in (CD3)2CO
1H
Compound
31P-{1H),a δ(P)
δ(CMe)
δ(PMe2)
δ(PMe)
δ(NMe2)
δ(γH)
b
(RP,S)-9a
(SP,S)-9a
(RP,S)-9b
(SP,S)-9b
21.0(26), 37.6(26)
22.3(26), 38.0(26)
29.5(24), 34.8(24)
28.9(27), 34.6(27)
1.87d
1.93d
1.77d
1.89d
2.13d
2.57d
2.36d
2.39d
2.44d
2.97bs, 3.41m
2.97bs, 3.42m
2.89bs, 3.47bs
2.99bs, 3.48bs
2.11d, 2.13d
2.00d, 2.15d
2.18d, 2.24d
6.85dd
b
b
a Values of 2JPP given in Hz in parentheses. b Obscured by the manifold of aromatic resonances.
parts. In the present work the two remaining diastereomers, viz.
(RP,S)-9b and (SP,S)-9b, had the same regiochemistry and
could not be differentiated by 31P-{1H} NMR spectroscopy.
60 ЊC (0.001 mmHg). 1H NMR (C6D6): δ 1.13 (d of t, 6 H, 3JHH
3
7.14, |2JPH ϩ 5JPЈH| 3.60, PMe), 1.16 (d of t, 6 H, JHH 7.41,
2
3
|2JPH ϩ 5JPЈH| 3.30, PMe), 4.23 (d of q, 2 H, JPH 216.4, JHH
2
3
7.14, PH), 4.37 (d of q, 2 H, JPH 213.4, JHH 7.41 Hz, PH),
6.99–7.28 (m, 8 H, aromatics). 31P-{1H} NMR (C6D6): δ Ϫ73.6
Conclusion
3
(s, 2 P), Ϫ74.7 (s, 2 P), Ϫ126.2 (d, 1 P, JPP 71 Hz, PH2 of 4).
The work detailed herein describes a viable synthetic route to an
optically active asymmetric di(tertiary phosphine), (SP)-(2-
chlorophenyl)(2-dimethylphosphinophenyl)methylphosphine.
The presence of the 2-chlorophenyl group is a key design
feature that should allow further derivatisation of the di-
(tertiary phosphine). Optically active asymmetric di(tertiary
phosphines) are seen as potential chiral auxiliaries in enantio-
selective catalysis. Moreover, 2-chlorophenyl substituted
ligands of this type and its precursor sodium (2-dimethyl-
phosphinophenyl)methylphosphide are seen as important
synthons in the design and synthesis of optically active linear
quadridentate ligands. We have previously shown that the
coupling of appropriately designed bidentate ligands of this
type (and their arsenic counterparts) can provide a highly stereo-
selective route to chiral linear quadridentate ligands containing
stereogenic phosphorus or arsenic donor atoms.11,12
m/z: 170, (M)ϩ; 155, (M Ϫ Me)ϩ; 123, (M Ϫ PHMe)ϩ. m/z
of 4: 156, (M)ϩ; 139, (M Ϫ Me)ϩ; 123, (M Ϫ PH2)ϩ; 109,
(M Ϫ PHMe)ϩ.
( )-(2-Dimethylphosphinophenyl)methylphosphine, 5. Liquid
ammonia (200 cm3) was condensed onto 3 (14.16 g, 0.083 mol)
and an excess amount of potassium metal pieces (4.01 g, 0.102
mol) added. The reaction mixture was stirred for 4 hours.
Methyl iodide (14.54 g, 0.102 mol) in THF (25 cm3) was added
dropwise and the clear solution allowed to warm to room tem-
perature overnight, to allow the ammonia to evaporate. Water
(100 cm3) was added to the residue, which was extracted with
diethyl ether (3 × 100 cm3). The diethyl ether extracts were
dried (MgSO4), filtered and the solvent was distilled off under
argon, leaving a yellow oil. Vacuum distillation of the oil gave
the product as a colourless oil (14.11 g, 92%), bp 67–68 ЊC
(0.005 mmHg). The product contained ca. 4% of 3 and ca. 22%
1
2
of 6. H NMR (C6D6): δ 1.08 (d, 3 H, JPH 4.0, PMeMe), 1.14
Experimental
Procedures and materials
(d, 3 H, 2JPH 3.4, PMeMe), 1.27 (d of d of d, 3 H, 3JHH 7.4, 2JPH
5
1
4
3.6, JPЈH 0.6, PHMe), 4.45 (d of d of q, 1 H, JPH 209, JPЈH
3
11.0, JHH 7.4 Hz, PHMe), 6.98–7.36 (m, 4 H, aromatics).
Reactions involving air-sensitive reagents were performed
under argon using Schlenk techniques. Solvents were dried
and purified by distillation under argon. NMR spectra were
recorded on a Varian Gemini II spectrometer operating at 300
(1H) or 121 MHz (31P-{1H}). Chemical shifts are reported as
δ values relative to SiMe4 (1H) or 85% H3PO4 (31P-{1H}).
Optical rotations were measured with an Optical Activity AA-
10 or a Perkin-Elmer Model 241 polarimeter on the specified
solutions in 1 dm cells at 20 ЊC. Elemental analyses were per-
formed by staff within the Research School of Chemistry.
The compounds 1,2-phenylenebis(phosphine), 2,13 and bis-
(µ-chloro)bis{(S)-2-[1-(dimethylamino)ethyl]naphthyl-C2,N}-
dipalladium(), (S)-8,4 were prepared by literature procedures.
31P-{1H} NMR (C6D6): δ Ϫ72.5 (d, 1 P, 3JPP 123, PHMe), Ϫ54.4
(d, 1 P, 3JPP 123 Hz, PMe2). m/z 184, (M)ϩ; 169, (M Ϫ Me)ϩ; 123,
(M Ϫ PMe2)ϩ.
1,2-Phenylenebis(dimethylphosphine), 6. Excess of sodium
foil (3.04 g, 0.132 mol) was added to (RP*,RP*)- and (RP*,SP*)-
1,2-phenylenebis(methylphosphine), (RP*,RP*)- and (RP*,SP*)-
3, (7.56 g, 0.044 mol) in THF (120 cm3), and the solution stirred
overnight. The excess of sodium was removed, and the orange
solution cooled to Ϫ78 ЊC. A solution of methyl iodide (12.61
g, 0.089 mol) in THF (30 cm3) was added dropwise. The solu-
tion was allowed to come to room temperature and stirred
overnight. The solvent was removed, water (80 cm3) added to
the residue, and the aqueous phase extracted with diethyl ether
(3 × 80 cm3). The combined ether extracts were dried (MgSO4),
filtered, and the solvent was removed to leave a yellow oil.
Vacuum distillation of the crude oil gave the product as a
colourless oil (7.10 g, 81%), bp 78 ЊC (0.001 mmHg) [lit.13 139–
Preparations
(R*P,R*P)- and (R*P,S*P)-1,2-phenylenebis(methylphosphine),
3. Sodium foil (4.30 g, 0.187 mol) was added piecewise to a
solution of 1,2-phenylenebis(phosphine), 2 (14.12 g, 0.099
mol), in THF (200 cm3), and the reaction mixture allowed to
stir for 48 h. Any excess of sodium was removed, and the
orange solution cooled to Ϫ78 ЊC. Methyl iodide (11.64 g, 0.187
mol) in THF (20 cm3) was added dropwise, and the solution
stirred overnight. The solvent was distilled off under argon.
Water (100 cm3) was added to the residue, and the aqueous
phase extracted with diethyl ether (3 × 100 cm3). The combined
diethyl ether extracts were dried (MgSO4), filtered and the
solvent was distilled off under argon, leaving a yellow oil. The
product was obtained as a colourless oil by vacuum distillation.
The product was isolated as a ca. 1 : 1 mixture of racemic
and meso diastereomers and also contained ca. 5% of ( )-(2-
methylphosphinophenyl)phosphine, 4 (14.16 g, 84%), bp 58–
1
141 ЊC (0.4–0.5 mmHg)]. H NMR (C6D6): δ 1.22 (t, 12 H,
|2JPH ϩ 5JPЈH| 1.73 Hz, PMe2), 7.1–7.35 (m, 4 H, aromatics).
31P-{1H} NMR (C6D6): δ Ϫ54.8 (s, 2 P, PMe2). m/z: 198, (M)ϩ;
183, (M Ϫ Me)ϩ.
( )-1-[(2-Chlorophenyl)methylphosphino]-2-(dimethyl-
phosphino)benzene, ( )-1. Sodium foil (0.92 g, 0.04 mol) was
added piecewise to a solution of 5 (7.38 g, 0.04 mol) in THF
(100 cm3) and the solution stirred overnight. The resulting
phosphide solution was added dropwise to a solution of 1,2-
dichlorobenzene (5.89 g, 0.04 mol) in THF (40 cm3). The reac-
tion mixture was stirred for 4 days. Water (20 cm3) was added,
and the solvent removed. Further water (100 cm3) was added,
1894
J. Chem. Soc., Dalton Trans., 2001, 1890–1896

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and the solution extracted with dichloromethane (3 × 90 cm3).
The organic extracts were dried (MgSO4), filtered and the
solvent was removed to give a yellow oil. The residue was dis-
tilled under reduced pressure. Fraction 1: 1,2-phenylene-
bis(dimethylphosphine), 6 (3.14 g), bp 78 ЊC (0.01 mmHg).
Fraction 2: ( )-1-[(2-chlorophenyl)methylphosphino]-2-(di-
methylphosphino)benzene, ( )-1 (4.75 g, 65% based on the
amount of 6 recovered), bp 135 ЊC (0.01 mmHg). The latter
also contained small quantities of 6 and 7.
of ( )-(2-chlorophenyl)(2-dimethylphosphinophenyl)methyl-
phosphine, ( )-1 (2.18 g, 7.38 mmol), in methanol (90 cm3). The
mixture was stirred at room temperature for 2.5 h, and then
filtered through Celite. Excess of ammonium hexafluorophos-
phate (1.51 g, 9.26 mmol) in water (10 cm3) was added dropwise
to the pale yellow filtrate. Water (70 cm3) was added dropwise,
and the white precipitate that formed was left to stir overnight.
The precipitate was isolated by filtration, washed with water
(25 cm3), diethyl ether–methanol (4 : 1, 15 cm3) and diethyl
ether (20 cm3) and dried in vacuo (4.62 g, 84%). α ϩ70Њ (589 nm,
c 1.0 g per 100 cm3, CH2Cl2).
Ligand ( )-1 (4.75 g, 15.7 mmol) was dissolved in hot
methanol (20 cm3), the solution allowed to cool slowly to room
temperature and then further cooled in ice. The resulting
The diastereomeric mixture of palladium() salts was dis-
solved in chloroform (30 cm3) and propan-2-ol (20 cm3) added
dropwise to give a 1 : 1 diastereomeric mixture of (RP,S)-9a and
(SP,S)-9a as fine white needles, which were isolated by filtration,
washed with diethyl ether (20 cm3) and dried in vacuo (2.01 g,
87%), α ϩ93Њ (589 nm, c 1.0 g per 100 cm3, CH2Cl2). The mother
liquor consisted of a ca. 1 : 1 : 9 : 9 mixture of (RP,S)-9a,
(SP,S)-9a, (RP,S)-9b and (SP,S)-9b which could not be further
separated by fractional crystallisation.
1
colourless prisms of 7 were collected and dried in vacuo. H
NMR (C6D6): δ 1.92 (d, 6 H, 2JPH 4.1 Hz, PMe), 6.78–7.34 (m,
8 H, aromatics). 31P-{1H} NMR (C6D6): δ Ϫ38.2 (s, 2 P). m/z
244, (M)ϩ; 229, (M Ϫ Me)ϩ; 214, (229 Ϫ Me)ϩ; 183, (214 Ϫ P)ϩ.
Ligand ( )-1 (4.86 g, 16.2 mmol) was dissolved in deoxygen-
ated ethanol (90 cm3) and added dropwise to a solution of
nickel() chloride hexahydrate (2.00 g, 8.41 mmol) in ethanol
(20 cm3). The red solution was stirred for 2 h. Excess of
ammonium hexafluorophosphate (2.06 g, 12.62 mmol) in water
(10 cm3) was added and the yellow-orange reaction mixture
stirred overnight. The product, which precipitated, was isolated
by filtration and washed with water (15 cm3), diethyl ether–
methanol (10 cm3) and diethyl ether (20 cm3), and dried in
vacuo. Further ammonium hexafluorophosphate (1.00 g, 6.13
mmol) in water (2 cm3) was added to the filtrate to afford
an additional crop of crystals. The combined product was
recrystallised from dichloromethane–diethyl ether to give pure
[Ni{( )-1}2][PF6]2 (3.70 g, 68%), mp 218–222 ЊC (Found: C,
38.7; H, 3.8. Calc. for C28H30Cl2F12NiP6: C, 38.4; H, 3.6%).
The complex [Ni{( )-1}2][PF6]2 (5.31 g, 5.97 mmol) was sus-
pended in deoxygenated dichloromethane (50 cm3) and water
(60 cm3). Potassium cyanide (17.63 g, 0.271 mol) was added and
the solution stirred vigorously for 15 h. The layers were separ-
ated and the aqueous layer was extracted with dichloromethane
(2 × 50 cm3). The organic layers were combined, dried
(MgSO4), filtered and the solvent was removed to give ( )-1
(2.92 g, 83%). 1H NMR (C6D6): δ 1.15 (d, 3 H, 2JPH 4.11, PMe),
The 1 : 1 mixture of (RP,S)-9a and (SP,S)-9a was dissolved in
acetone (10 cm3) and propan-2-ol (8 cm3) added dropwise to
give white blocks of diastereomerically pure (SP,S)-9a (0.79 g,
79%), mp 217–220 ЊC, α ϩ74Њ (589 nm, c 0.30 g per 100 cm3,
CH2Cl2) (Found: C, 46.8; H, 4.4; N, 1.9. Calc. for C29H33ClF6-
NP3Pd: C, 46.8; H, 4.5; N, 1.9%). 1H NMR [(CD3)2CO]: δ 1.93
(d, 3 H, 3JHH 6.4, CMe), 2.11 (d, 3 H, 2JPH 8.43, PMeMe), 2.13
(d, 3 H, 2JPH 8.04, PMeMe), 2.36 (d, 3H, 2JPH 10.26, PMe), 2.97
(br s, 3 H, NMe), 3.42 (m, 3 H, NMe), 4.79 (m, 1 H, CHMe),
3
4
6.85 (d of d, 1 H, JHH 6.4, JPH 13.98 Hz, γH), 7.28–8.44 (m,
13 H, aromatics). 31P-{1H} NMR [(CD3)2CO]: δ Ϫ143.7 (septet,
1
2
1 P, JPF 710, PF6), 22.3 (d, 1 P, JPP 25.5, PMe2), 38.0 (d, 1 P,
2JPP 25.5 Hz, PMe(C6H4Cl-2)).
The mother liquor, which was enriched in (RP,S)-9a, was
taken to dryness and the residue dissolved in dichloro-
methane (5 cm3). Propan-2-ol (5 cm3) was added dropwise to
give white plates of diastereomerically pure (RP,S)-9a (0.34 g,
34%), mp 205 ЊC (decomp.), α ϩ225Њ (589 nm, c 0.30 g per
100 cm3, CH2Cl2) (Found: C, 43.8; H, 4.5; N, 1.7. Calc. for
C29H33ClF6NP3PdؒCH2Cl2: C, 43.4; H, 4.2; N, 1.7%). 1H
2
2
1.22 (d, 3 H, JPH 3.36, PMe), 1.47 (d, 3 H, JPH 5.28 Hz,
PMeC6H4Cl-2), 6.78–7.34 (m, 8 H, aromatics). 31P-{1H}
NMR [(CD3)2CO]: δ 1.87 (d, 3 H, JHH 6.30, CMe), 2.13 (d,
3
3
NMR (C6D6): δ Ϫ53.6 (d, 1 P, JPP 153.6, PMe2); Ϫ36.4
6 H, 2JPH 8.25, PMe2), 2.57 (d, 3 H, 2JPH 9.57, PMe), 2.97 (br s,
(d, 1 P, JPP 153.6 Hz, PMeC6H4Cl-2). m/z: 294, (Mϩ); 279,
3 H, NMe), 3.41 (t, 3 H, JPH 3.60 Hz, NMe), 4.78 (m, 1 H,
3
4
(M Ϫ Me)ϩ; 259, (M Ϫ Cl)ϩ.
CHMe), 7.33–8.50 (m, 14 H, aromatics). 31P-{1H} NMR
1
[(CD3)2CO]: δ Ϫ143.7 (septet, 1 P, JPF 710, PF6), 21.0 (d,
2
2
[SP-4-1]-Bis{(1,2-phenylenebis(dimethylphosphine)-P,PЈ}-
nickel(II) hexafluorophosphate, [Ni(6)2][PF6]2. The ligand 6
(0.544 g, 2.74 mmol) was dissolved in ethanol (10 cm3) and
hexaaquanickel() chloride (0.399 g, 1.37 mmol) added. The
solution was stirred for 2 h, filtered, and taken to dryness.
The residue was redissolved in methanol, and ammonium
hexafluorophosphate (0.224 g, 1.37 mmol) in water (2 cm3)
added dropwise. Water (15 cm3) was added and the reaction
mixture stirred overnight. The product was isolated by filtra-
tion, washed with water (10 cm3), diethyl ether–methanol (4 : 1,
10 cm3) and diethyl ether (15 cm3), and dried in vacuo (0.542 g,
66%), mp 314–317 ЊC (Found: C, 32.1; H, 4.4. Calc. for
C20H32F12NiP6: C, 32.2; H, 4.3%). 1H NMR [(CD3)2CO]: δ 2.19
(s, 24 H, PMe2), 7.93–8.28 (d of m, 8 H, aromatics). 31P-{1H}
NMR [(CD3)2CO]: δ 41.2 (s, 4 P, PMe2).
1P, JPP 25.5, PMe2), 37.6 (d, 1P, JPP 25.5 Hz, PMe-
(C6H4Cl-2)).
[SP-4-2-(SP)]-Dichloro[(2-chlorophenyl)(2-dimethylphosphino-
phenyl)methylphosphine-P,PЈ]palladium(II), (SP)-10. Diastereo-
merically pure (SP,S)-9a (0.75 g, 1.01 mmol) was dissolved in
concentrated sulfuric acid (4 cm3) and the yellow solution
poured onto ice (10 g). Lithium chloride (0.5 g, 11.78 mmol),
dichloromethane (30 cm3) and water (30 cm3) were added, and
the two layers separated. The aqueous layer was further
extracted with dichloromethane (2 × 30 cm3), and the com-
bined organic layers were dried (MgSO4), filtered, and the
solvent was removed under reduced pressure. The residue was
recrystallised from dichloromethane–methanol to give enantio-
merically pure (SP)-10 (0.40 g, 85%), mp 180–185 ЊC, α ϩ52Њ
(589 nm, c 0.25 g per 100 cm3, CH2Cl2). 1H NMR [(CD3)2SO]:
2
2
Resolution of ( )-1: formation and separation of the internally
diastereomeric complexes [SP-4-3-(RP,S)]-, [SP-4-3-(SP,S)]-,
δ 2.08 (d, 6 H, JPH 13.9, PMe2), 2.40 (d, 3 H, JPH 13.9 Hz,
PMe2), 7.51–8.23 (m, 8 H, aromatics). 31P-{1H} NMR
[(CD3)2SO]: δ 53.5 (d, 1P, 3JPP 17 Hz, PMe2), 59.2 (d, 1P, 3JPP 17
Hz, PMe(C6H4Cl-2)).
[SP-4-4-(RP,S)]-
and
[SP-4-4-(SP,S)]-[(2-chlorophenyl)(2-
dimethylphosphinophenyl)methylphosphine-P,PЈ]{[1-(1-dimethyl-
amino)ethyl]naphthyl-C2,N}palladium(II) hexafluorophosphate,
(RP,S)-9a, (SP,S)-9a, (RP,S)-9b and (SP,S)-9b. To a suspension
of the resolving agent, di-µ-chloro-bis{(S)-1-[1-(dimethyl-
amino)ethyl]naphthyl-C2,N}dipalladium(), (S)-8 (2.51 g, 3.69
mmol), in methanol (30 cm3), was slowly added a solution
(RP)-1-[(2-Chlorophenyl)methylphosphino]-2-(dimethyl-
phosphino)benzene, (RP)-1. Enantiomerically pure (SP)-10 (0.40
g, 0.86 mmol) was suspended in light petroleum (bp 60–80 ЊC)
(20 cm3) and methanol (20 cm3). Potassium cyanide (2.24 g,
J. Chem. Soc., Dalton Trans., 2001, 1890–1896
1895

View Article Online
4 For example: (a) D. G. Allen, G. M. McLaughlin, G. B. Robertson,
34.39 mmol) was added, and the mixture shaken vigorously.
Water (20 cm3) was added and the layers were separated. The
aqueous layer was extracted with light petroleum (2 × 30 cm3).
The organic layers were combined, dried, filtered and the
solvent was removed under vacuum to give (RP)-1 (0.22 g, 88%),
α ϩ33Њ (589 nm, c 0.25 g per 100 cm3, CH2Cl2). 1H and 31P-{1H}
NMR (C6D6): identical with those recorded for the racemic
compound ( )-1.
W. L. Steffen, G. Salem and S. B. Wild, Inorg. Chem., 1982, 21, 1007;
(b) J. W. L. Martin, J. A. L. Palmer and S. B. Wild, Inorg. Chem.,
1984, 23, 2664; (c) C. E. Barclay, G. Deeble, R. J. Doyle, S. A. Elix,
T. L. Jones, G. Salem, S. B. Wild and A. C. Willis, J. Chem. Soc.,
Dalton Trans., 1995, 57; (d) P. H. Leung, G. M. McLaughlin, J. W. L.
Martin and S. B. Wild, Inorg. Chem., 1986, 25, 3392.
5 R. J. Doyle, G. Salem and A. C. Willis, J. Chem. Soc., Dalton Trans.,
1995, 1867.
6 G. Salem and S. B. Wild, Inorg. Chem., 1983, 22, 4049.
7 A. Miyashita, A. Yasuda, H. Takaya, K. Toriumi, T. Ito, T. Souchi
and R. Noyori, J. Am. Chem. Soc., 1980, 102, 7932; J. M. Brown,
D. I. Hulmes and T. P. Layzell, J. Chem. Soc., Chem. Commun.,
1993, 1673.
8 A. L. Airey, G. F. Swiegers, A. C. Willis and S. B. Wild, Inorg.
Chem., 1997, 36, 1588.
9 N. Gabbitas, G. Salem, M. Sterns and A. C. Willis, J. Chem. Soc.,
Dalton Trans., 1993, 3271.
10 J. Leitch, G. Salem and D. C. R. Hockless, J. Chem. Soc., Dalton
Trans., 1995, 649.
11 R. J. Doyle, G. Salem and A. C. Willis, J. Chem. Soc., Dalton Trans.,
1997, 2713.
X-Ray crystallography
Crystal data for complex (SP,S)-9a. C29H33ClF6NP3Pd,
M = 744.35, monoclinic, space group P21 (no. 4), a = 8.982(2),
b = 13.436(2), c = 13.797(2) Å, β = 102.87(1)Њ, U = 1623.2(5) Å3,
T = 296 K, Z = 2, µ(Mo-Kα) = 8.45 cmϪ1, 5016 reflections
measured, 3899 unique (Rint = 0.017) which were used in all
calculations. The final R and RЈ values were 0.0324 and 0.0277.
The structure was solved by direct methods and expanded
using Fourier techniques.16,17 The non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were included at geo-
metrically determined positions that were periodically
recalculated but not refined. All calculations were performed
using the TEXSAN crystallographic software package.18
CCDC reference number 158059.
12 S. Chatterjee, R. J. Doyle, D. C. R. Hockless, G. Salem and A. C.
Willis, J. Chem. Soc., Dalton Trans., 2000, 1829.
13 E. P. Kyba, M. C. Kerby and S. P. Rines, Organometallics, 1983, 2,
1877.
14 W. Levason, K. G. Smith, C. A. McAuliffe, F. P. McCullough, R. D.
Sedgwick and S. G. Murray, J. Chem. Soc., Dalton Trans., 1979,
1718.
15 M. A. Bennett and L. F. Warren, Inorg. Chem., 1976, 15, 3126.
16 SIR 92, A. Altomare, M. Cascarano, C. Giacovazzo, A. Guagliardi,
M. C. Burla, G. Polidori and M. Camalli, J. Appl. Crystallogr., 1994,
27, 435.
17 DIRDIF 94, P. T. Beurskens, G. Admiraal, G. Beurskens, W. P.
Bosman, R. de Gelder, R. Israel and J. M. M. Smits, the DIRDIF
program system, Technical Report of the Crystallography
Laboratory, University of Nijmegen, 1994.
See http://www.rsc.org/suppdata/dt/b1/b101182k/ for crystal-
lographic data in CIF or other electronic format.
References
1 S. B. Wild, Coord. Chem. Rev., 1997, 166, 291.
2 N. K. Roberts and S. B. Wild, J. Am. Chem. Soc., 1979, 101,
6254.
3 N. K. Roberts and S. B. Wild, J. Chem. Soc., Dalton Trans., 1979,
2015.
18 TEXSAN, Crystal Structure Analysis Software, Version 1.8,
Molecular Structure Corporation, Houston, TX, 1997.
1896
J. Chem. Soc., Dalton Trans., 2001, 1890–1896