Formation of imino-phosphine bidentate chelates by an unprecedented organopalladium complex promoted oxidative coupling reaction between diphenylvinylphosphine and imines

Article abstract of DOI:10.1021/om000416l

Oxidative coupling reaction between Ph₂P-CH=CH₂ and a series of imines PhC(R)=N(R′) [where R = H, D; R′ = H, Ph, p-Me(C₆H₄), p-Cl(C₆H₄), p-Cl(C₆H₄)] in the presence of (S)-ortho-palladated[1-(dimethylamino)ethyl]naphthylene as the reaction template produced the unexpected imino-phosphine ligands (R′)N=C-C(=CPhR)PPh₂ where the P,N-bidentate chelates to the chiral palladium template. The coupling reactions initially adopted a [2+2] cycloaddition mechanism followed by the ring-opening pathway to generate the acyclic ligands. The rate of these coupling reactions was affected by the electronic properties of the R' group on the imines. No coupling reaction was observed between Ph₂P-CH=CH₂ and p-CF₃(C₆H₄)N=CPh(H), which contains a strong electronic withdrawing group at the p-position. In all the product complexes the nitrogen donors from the imine and from the naphthylamine chelates are coordinated regiospecifically in the cis positions. Similarly the R substituent and the PPh₂ moiety are invariably located in the cis positions on the newly generated C=C bonds. The imino-phosphine chelates are stable in strong sulfuric acid, while the naphthylamine moiety in the template complexes is removed chemoselectively in the presence of this acid. Upon the removal of the naphthylamine chelate, the imino-phosphines could be liberated from palladium by the treatment with aqueous cyanide. Except for HN=C-C(=CPhH)PPh₂, which decomposed readily in aqueous solution, all the other liberated imino-phosphines were obtained as air-stable low-melting solids.

Full text of DOI:10.1021/om000416l

3722
Organometallics 2000, 19, 3722-3729
F or m a tion of Im in o-P h osp h in e Bid en ta te Ch ela tes by
a n Un p r eced en ted Or ga n op a lla d iu m Com p lex P r om oted
Oxid a tive Cou p lin g Rea ction betw een
Dip h en ylvin ylp h osp h in e a n d Im in es
Xueming Liu, K. F. Mok, J agadese J . Vittal, and Pak-Hing Leung*
Department of Chemistry, National University of Singapore, Kent Ridge, Singapore 119260
Received May 16, 2000
Oxidative coupling reaction between Ph2P-CHdCH2 and a series of imines PhC(R)dN(R′)
[where R ) H, D; R′ ) H, Ph, p-Me(C6H4), p-Cl(C6H4), p-MeO(C6H4)] in the presence of (S)-
ortho-palladated[1-(dimethylamino)ethyl]naphthylene as the reaction template produced the
unexpected imino-phosphine ligands (R′)NdC-C(dCPhR)PPh2 where the P,N-bidentate
chelates to the chiral palladium template. The coupling reactions initially adopted a [2+2]
cycloaddition mechanism followed by the ring-opening pathway to generate the acyclic
ligands. The rate of these coupling reactions was affected by the electronic properties of the
R′ group on the imines. No coupling reaction was observed between Ph2P-CHdCH2 and
p-CF3(C6H4)NdCPh(H), which contains a strong electronic withdrawing group at the
p-position. In all the product complexes the nitrogen donors from the imine and from the
naphthylamine chelates are coordinated regiospecifically in the cis positions. Similarly the
R substituent and the PPh2 moiety are invariably located in the cis positions on the newly
generated CdC bonds. The imino-phosphine chelates are stable in strong sulfuric acid, while
the naphthylamine moiety in the template complexes is removed chemoselectively in the
presence of this acid. Upon the removal of the naphthylamine chelate, the imino-phosphines
could be liberated from palladium by the treatment with aqueous cyanide. Except for
HNdC-C(dCPhH)PPh2, which decomposed readily in aqueous solution, all the other
liberated imino-phosphines were obtained as air-stable low-melting solids.
In tr od u ction
Diels-Alder reactions. Thus an interesting range of
P-chiral diphosphines, P-As, and functionalized mono-
dentate phosphines with the rigid phosphanorbornene
skeleton have been produced efficiently. In continuing
our interest in this class of ligand transformation
reactions, we herein report the coupling reaction be-
tween a series of benzylic imines and the coordinated
vinylphosphine Ph2PCHdCH2. It has been reported that
in the presence of indium trichloride benzylic imines
react as heterodienes toward dienophiles via their
CdN and neighboring aromatic CdC bonds.6 As imines
are known to coordinate to palladium(II) ions,7 it is thus
anticipated that in the presence of the organopalla-
dium-amine template, benzylic imines and vinyl phos-
phines could undergo the analogous [4+2] cycloaddition
reaction.
The importance of metals and metal ions in synthetic
organic chemistry has been well established.1 In numer-
ous synthetic processes, the utilization of these classic
inorganic materials provides dramatic activation and
product selectivity. Recently we have applied a chiral
organopalladium-amine template complex as well as
its platinum analogue for the activation of Ph2As-
CHdCH2,2 a variety of vinylphosphines,3 and cyclic
phospholes as dienophiles4 or dienes5 in asymmetric
(1) Noels, A. F.; Graziani, M.; Hubert, A. J . Metal Promoted
Selectivity in Organic Synthesis; Kluwer: Dordecht, The Netherlands,
1991. Bosnich, B. Asymmetric Catalysis; Martinus Nijhoff: Boston, MA,
1986.
(2) Aw, B. H.; Leung, P. H.; White, A. J . P.; Williams, D. J .
Organometallics 1996, 15, 3640.
(3) Aw, B. H.; Hor, T. S. A.; Selvaratnam, S.; Mok, K. F.; White, A.
J . P.; Williams, D. J .; Rees, N. H.; McFarlane, W.; Leung, P. H. Inorg.
Chem. 1997, 36, 2138. Selvaratnam, S.; Mok, K. F.; Leung, P. H.;
White, A. J . P.; Williams, D. J . Inorg. Chem. 1996, 35, 4798. Liu, A.
M.; Mok, K. F.; Leung, P. H. J . Chem. Soc., Chem. Commun. 1997,
2397. Leung, P. H.; Liu, A. M.; Mok, K. F. Tetrahedron Asymmetry
1999, 10, 1309.
(4) Leung, P. H.; Loh, S. K.; Vittal, J . J .; White, A. J . P.; Williams,
D. J . J . Chem. Soc., Chem. Commun. 1997, 1987. Leung, P. H.; Siah,
S. Y.; White, A. J . P.; Williams, D. J . J . Chem. Soc., Dalton Trans.
1998, 893. He, G. S.; Loh, S. K.; Vittal, J . J .; Mok, K. F.; Leung, P. H.
Organometallics 1998, 17, 3931. Song, Y. C.; Vittal, J . J .; Chan, S. H.;
Leung, P. H. Organometallics 1999, 18, 650. Leung, P. H.; He, G.; Lang,
H.; Liu, A.; Loh, S. K.; Selvaratnam, S.; Mok, K. F.; White, A. J . P.;
Williams, D. J . Tetrahedron 2000, 56, 7.
Resu lts a n d Discu ssion
It has been well established that the Pd-Cl bond in
the chiral complex (S)-1 is thermodynamically and
(6) Babu, G.; Perumal, P. Tetrahedron Lett. 1997, 38, 5025. Babu,
G.; Perumal, P. Tetrahedron Lett. 1998, 39, 3225. Babu, G.; Perumal,
P. Tetrahedron 1998, 54, 1627.
(7) Crociani, L.; Bandoli, G.; Dolmella, A.; Basato, M.; Corain, B.
Eur. J . Inorg. Chem. 1998, 1811. Diederen, J . J . H.; Fruhauf, H. W.;
Hiemstra, H.; Vrieze, K. Tetrahedron Lett. 1998, 39, 4111. Pelagatti,
P.; Bacchi, A.; Carcelli, M.; Costa, M.; Fochi, A.; Ghidini, P.; Leporati,
E.; Masi, M.; Pelizzi, C.; Pelizzi, G. J . Organomet. Chem. 1999, 583,
94. Reddy, K. R.; Chen, C. L.; Liu, Y. H.; Peng, S. M.; Chen, J . T.; Liu,
S. T. Organometallics 1999, 18, 2574.
(5) He, G.; Qin, Y.; Mok, K. F.; Leung, P. H. J . Chem. Soc., Chem.
Commun. 2000, 167.
10.1021/om000416l CCC: $19.00 © 2000 American Chemical Society
Publication on Web 08/11/2000

Imino-Phosphine Bidentate Chelates
Organometallics, Vol. 19, No. 18, 2000 3723
Sch em e 1
Sch em e 2
kinetically stable (Scheme 1).8 In general, the anionic
ligand is inert to ligand exchange reactions, even in the
presence of strong ligands such as monodentate phos-
phines and arsines. In contrast, the perchlorato ligand
in (S)-2 is labile and readily replaced by most donor
atoms.9 By utilizing this readily available coordination
site, we have previously used (S)-2 as the chiral
template for the asymmetric cycloaddition reaction
between the diphenylvinylphosphine ligand in (S)-2 and
dimethylphenylphosphole. This reaction adopts an in-
tramolecular mechanism in which both the phosphole
and vinylphosphine ligand are coordinated simulta-
neously on the chiral palladium template during the
course of cycloaddition reaction.3-5 This crucial inter-
mediate could not be achieved with the stable chloro
complex. By using a similar methodology, a series of
stereochemically demanding P-chiral diphosphines were
produced from dimethylphenylphosphole and selected
substituted vinylphosphines. It is important to note
that, without metal complexation, vinylphosphines are
not reactive dienophiles. Thus no intermolecular cy-
cloaddition reaction has been observed between free
vinylphosphines and cyclic phospholes.
As intimated above, benzylic imines are potential
dienes and may show reactivities toward dienophiles.6
We were therefore interested in the coupling reaction
between these potential heterodienes and vinylphos-
phines. As expected, no reaction occurred between the
uncoordinated N-benzylideneaniline and free diphe-
nylvinylphosphine, or (S)-1, despite the strong reaction
conditions used. Apparently, it is necessary to activate
imines and vinylphosphines simultaneously via the
metal complexation. Hence the stable chloro ligand in
(S)-1 was removed quantitatively by our standard
treatment with silver perchlorate to generate the reac-
tive template (S)-2. As illustrated in Scheme 1, this
perchlorato complex reacted smoothly with excess N-
benzylideneaniline at 100 °C in toluene. The reaction
was monitored by 31P NMR spectroscopy and found to
be complete in 48 h. The 31P NMR spectrum exhibited
a sharp singlet at δ 52.2. This relatively lower field shift
indicated that the phosphorus donor is involved in a
five-membered bidentate metal chelate.10 The resulting
template complex (S)-3a was crystallized from dichlo-
romethane-diethyl ether as stable yellow needles in
33% yield with [R]D +212.5 (CH2Cl2). Unfortunately,
single crystals of the complex suitable for structural
investigation could not be produced, despite numerous
attempts with many solvent systems. Thus (S)-3a was
converted quantitatively to the highly crystalline dichlo-
ro complex 4a (Scheme 2). The conversion process
involved first the chemoselective removal of the naph-
thylamine moiety from (S)-3a using concentrated sul-
furic acid, followed by the addition of excess lithium
chloride to the acidic solution to generate the dichloro
complex 4a . Similar to (S)-3a , the 31P NMR spectrum
of 4a exhibits a sharp singlet at δ 51.7. The X-ray
structure of 4a , however, revealed that the ligand
transformation process produced an unexpected imino-
phosphine chelate, rather than the expected [4+2]
(8) Chooi, S. Y. M.; Leung. P. H.; Lim, C. C.; Mok, K. F.; Quek, G.
H.; Sim, K. Y.; Tan, M. K. Tetrahedron: Asymmetry 1992, 3, 529.
Dunina, V. V.; Golovan, E. B.; Gulyukina, N. S.; Buyevich, A. V.
Tetrahedron: Asymmetry 1995, 6, 2371. Albert, J .; Cadena, J . M.;
Granell, J . Tetrahedron: Asymmetry 1997, 8, 991. Dunina, V. V.;
Kuzmina, L. G.; Kazakova, M. Y.; Grishin, Y. K.; Veits, Y. A.;
Kazakova, E. I. Tetrahedron: Asymmetry 1997, 8, 2537.
(9) Loh, S. K.; Mok, K. F.; Leung, P. H.; White, A. J . P.; Williams,
D. J . Tetrahedron: Asymmetry 1996, 7, 45.
(10) Garrou, P. E. Chem. Rev. 1981, 81, 229.

3724 Organometallics, Vol. 19, No. 18, 2000
Liu et al.
oxidative coupling reaction between the vinylphosphine
ligand and N-benzylideneaniline.
To investigate the origins of the eliminated hydrogen
atoms, the coupling reaction was repeated with labeled
imine ligand PhC(D)dNPh and (S)-2. Unfortunately,
single crystals of the deuterium-labeled complex (S)-3b
also could not be obtained, although it is readily
crystallized from dichloromethane-diethyl ether as pale
yellow opaique prisms. These opaique crystals were
treated with sulfuric acid and lithium chloride to give
the dichloro complex 4b. The 31P NMR spectrum of 4b
exhibited a singlet signal identical with that recorded
1
1
for 4a . A detailed spectroscopic study of the H and H-
ROESY NMR spectra of both complexes confirmed that
the deuterium atom is retained within the PhC(D) group
in complex 4b. This spectroscopic study thus indirectly
suggested that the R- and the â-vinylic carbons of the
reacting phosphine ligand had each eliminated a hy-
drogen during the course of ligand transformation
reaction.
F igu r e 1. Molecular structure of complex 4a .
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for th e Dich lor o Com p lexes 4a , 4c, a n d 4f
4c
From a mechanistic standpoint, it is important to note
that some imino complexes are sensitive to minerial
acids and may undergo ligand rearrangement reactions
in acidic solutions.10 Since complexes 4a and 4b were
obtained from complexes (S)-3a and (S)-3b, respectively,
via strong acid treatment, it is therefore necessary to
confirm that these precursor complexes indeed contain
the same P-N chelates. Thus the analogous complexes
(S)-3c and (S)-3d were prepared by treating (S)-2 with
imine ligand p-Me(C6H4)NdCPh(H) and p-Cl(C6H4)-
NdCPh(H), respectively. Interestingly, p-Me(C6H4)-
NdCPh(H) seems to be more reactive than p-Cl(C6H4)-
NdCPh(H), as (S)-3c was obtained within 24 h, but the
formation (S)-3d required 48 h under similar reaction
conditions. In CDCl3 the 31P NMR spectra of (S)-3c and
(S)-3d each exhibits one sharp singlet, at δ 52.6 and
51.5, respectively. In contrast to their unsubstituted
analogues, both the p-substituted complexes were ob-
tained as highly crystalline yellow prisms. The molec-
ular structure of these complexes was determined by
X-ray structural analyses. Both complexes crystallized
as two independent molecules in their unit cells (labeled
A and B). In each complex, the pair of independent
molecules have the same molecular connectivity and
differ slightly only in the bond distances and the
rotational angles of the phenyl rings with respect to the
coordination plane. For clarity, only molecules A of (S)-
3c and (S)-3d are depicted in Figures 2 and 3, respec-
tively. Selected bond distances and angles of the com-
plexes are given in Table 2. The X-ray analyses of both
complexes confirm that the analogous p-substituted
imino-phosphine chelates have indeed been generated
on the palladium template. In both complexes, the
phosphorus donor atoms are coordinated regiospecifi-
cally in the position trans to the naphthylamine-N donor
atom. Such regiopecificity has been invariably observed
with heterobidentate complexes containing this cyclo-
palladated naphthylamine unit and has been attributed
to the trans electronic influences originating from the
σ-donating nitrogen and the π-accepting aromatic car-
bon atoms of the organometallic ring. The N(2)-C(15)
bond distances in (S)-3c [1.294(6) and 1.265(6) Å for
molecules A and B, respectively] and (S)-3d [1.289 (10)
Å for both molecules] are consistent with the imino
4a
molecule A molecule B
4f
Pd(1)-Cl(1)
Pd(1)-Cl(2)
Pd(1)-P(1)
Pd(1)-N(4)
C(3)-N(4)
C(2)-C(5)
2.371(1)
2.286(1)
2.206(1)
2.071(2)
1.301(4)
1.352(4)
2.372(1)
2.286(1)
2.199(1)
2.060(2)
1.299(3)
1.354(3)
169.5(1)
90.0(1)
82.6(1)
2.355(1)
2.293(1)
2.203(1)
2.074(1)
1.289(3)
1.345(4)
177.5(1)
89.2(1)
82.7(1)
2.356(1)
2.285(1)
2.211(1)
1.998(2)
1.277(3)
1.347(3)
173.3(1)
93.0(1)
82.7(1)
P(1)-Pd(1)-Cl(1) 171.1(1)
P(1)-Pd(1)-Cl(2)
P(1)-Pd(1)-N(4)
89.6(1)
83.1(1)
Cl(1)-Pd(1)-N(4) 95.3(1)
Cl(2)-Pd(1)-N(4) 170.5(1)
94.6(1)
95.6(1)
90.9(1)
170.9(1)
109.8(2)
123.6(2)
119.8(2)
126.2(2)
170.8(1)
109.7(2)
124.2(2)
121.4(2)
126.1(2)
175.1(1)
110.3(2)
124.3(2)
119.5(3)
125.3(2)
P(1)-C(2)-C(3)
P(1)-C(2)-C(5)
C(2)-C(3)-N(4)
C(3)-C(2)-C(5)
110.3(2)
123.5(2)
120.3(3)
126.2(3)
cycloadduct (Figure 1). Clearly, the aromatic CdC bonds
in the dN-Ph function were not involved in the ligand
transformation reaction. Selected bond distances and
angles of the imino-phosphine complex are given in
Table 1. In this new P-N chelate, the short C(2)-C(5)
[1.352(4) Å] and the C(3)-N(4) [1.301(4) Å] bond dis-
tances clearly indicated that they are CdC and CdN
double bonds, as illustrated diagrammetrically in Scheme
2. Hence, despite the fact that the phosphorus and the
nitrogen donor atoms have been connected by a carbon-
carbon linkage, a new imino CdN bond and a new
P-vinylic function have been regenerated within the
product ligand. Another interesting feature of this
molecule is the new location of the PhC(H)d moiety. The
C-phenyl group originally in the imine precursor is now
located on the new CdC function, which is trans to the
PPh2 moiety. We believe that the C-Ph bond is intact
throughout the reaction, as it is perhaps one of the most
stable C-C bondings in classic organic chemistry. Thus,
the migration of this PhC(H)d group must have in-
volved the cleavage of the CdN bond in the original
PhC(H)dNPh precursor. From the product structure, a
new CdN bond must also be formed between nitrogen
and the â-carbon of the originally vinylic P-CdC
function. Yet another interesting and important feature
of this coupling reaction is the elimination of two
hydrogen atoms from the precursors. Hence, the forma-
tion of this new P-N chelate can be regarded as an

Imino-Phosphine Bidentate Chelates
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles (d eg) for th e Ca tion ic Com p lexes (S)-3c, (S)-3d , a n d (S)-3f
(S)-3c (S)-3d (S)-3f
Organometallics, Vol. 19, No. 18, 2000 3725
molecule A
molecule B
molecule A
molecule B
molecule A
molecule B
Pd(1)-C(1)
2.017(5)
2.169(4)
2.223(1)
2.167(4)
1.344(7)
1.294(6)
81.0(2)
176.3(2)
98.4(1)
101.0(2)
177.6(1)
79.7(1)
2.012(6)
2.144(4)
2.232(1)
2.201(5)
1.339(7)
1.265(6)
80.3(2)
170.4(2)
100.0(2)
102.9(2)
166.9(1)
79.0(1)
1.984(9)
2.152(6)
2.225(2)
2.193(7)
1.345(12)
1.281(11)
81.6(3)
175.7(3)
97.9(2)
101.0(2)
177.1(2)
79.7(2)
2.034(8)
2.134(6)
2.233(2)
2.173(8)
1.351(11)
1.289(10)
79.7(3)
170.3(2)
100.4(2)
103.2(3)
166.0(2)
79.1(2)
2.031(6)
2.123(5)
2.246(2)
2.117(6)
1.331(8)
1.280(9)
80.3(2)
176.3(3)
101.5(2)
97.0(2)
178.1(2)
81.2(2)
110.5(4)
124.2(5)
125.2(6)
119.8(6)
2.017(6)
2.120(5)
2.231(2)
2.119(6)
1.352(8)
1.275(8)
80.9(2)
176.9(3)
99.6(2)
99.1(2)
173.2(2)
80.8(2)
110.4(4)
123.8(5)
125.8(6)
120.1(6)
Pd(1)-N(1)
Pd(1)-P(1)
Pd(1)-N(2)
C(16)-C(17)
C(15)-N(2)
C(1)-Pd(1)-N(1)
C(1)-Pd(1)-N(2)
C(1)-Pd(1)-P(1)
N(1)-Pd(1)-N(2)
N(1)-Pd(1)-P(1)
N(2)-Pd(1)-P(1)
P(1)-C(16)-C(15)
P(1)-C(16)-C(17)
C(15)-C(16)-C(17)
N(2)-C(15)-C(16)
108.8(3)
124.7(4)
125.8(5)
120.8(5)
109.2(4)
125.1(4)
124.9(5)
121.0(5)
109.5(6)
126.0(7)
123.8(9)
120.7(8)
109.2(5)
124.0(7)
126.0(8)
120.3(8)
F igu r e 4. Molecular structure of complex 4c.
F igu r e 2. Molecular structure and absolute stereochem-
istry of complex (S)-3c.
complex (S)-3c is faster (24 h) than that observed for
complexes (S)-3a ,b,d (48 h). The difference in the
reaction rates seems to indicate that the reaction can
be accelerated by introducing an electronic donating
group into the p-position of the dN-Ph phenyl ring. To
confirm this possible electronic effect, the p-substituted
imines p-MeO(C6H4)NdCPh(H) and p-CF3(C6H4)-
NdCPh(H) were treated individually with (S)-2. No
coupling was observed in the reaction involving p-CF3-
(C6H4)NdCPh(H). However, with p-MeO(C6H4)NdC-
Ph(H), the corresponding imino-phosphine complex (S)-
3e was obtained within 24 h. These observations thus
confirmed that the electronic properties of the p-sub-
stituents on the N-Ph ring affected the rate of the
ligand transformation reaction. The acid treatment of
the cationic complexes (S)-3c-e gave the corresonding
dichloro complexes 4c-e. The dichloro complex 4c was
selected for the single-crystal X-ray crystallographic
characterization. The structural analysis of the two
crystallographically independent molecules in 4c re-
vealed that they have the same molecular architecture
but differ in the absolute orientation of the P-Ph rings
(Figure 4). The bond distances and angles of the imino-
phosphine ring are similar to those observed in com-
plexes (S)-3c,d and 4a (Table 1).
F igu r e 3. Molecular structure and absolute stereochem-
istry of complex (S)-3d .
CdN linkage. Similarly their C(16)-C(17) bond dis-
tances [1.344(7), 1.339(7), 1.345(12), and 1.351(11) Å for
(S)-3cA, (S)-3cB, (S)-3d A, and (S)-3d B, respectively]
clearly indicated that they are CdC bonds. Thus the
structural analyses of complexes (S)-3c and (S)-3d
confirmed that the imino-phosphine chelates were
indeed produced directly from the treatment of the
coordinated vinylphosphine with imines. It is notewor-
thy that, as previously described, the formation of
Evidently, the imino-phosphine chelates in this
series of compounds are stable in strong acidic condition,
as heating complexes (S)-3a -e in concentrated sulfuric
acid only removed the ortho-metalated naphthylamine
ligand chemoselectively (Scheme 2). This is in contrast
to many reports that coordinated imines are reactive
in acidic conditions. It was not clear if the CdN bond

3726 Organometallics, Vol. 19, No. 18, 2000
Liu et al.
F igu r e 5. Molecular structure and absolute stereochem-
istry of complex (S)-3f.
in the new P-N chelates was stabilized by the dN-Ph
aromatic ring or by metal complexation. Thus the
reaction involving the imine HNdCPh(H) was carried
out. The primary imine showed reactivities similar to
p-Me(C6H4)NdCPh(H) and p-MeO(C6H4)NdCPh(H) to-
ward (S)-2. The imino-phosphine complex (S)-3f was
obtained in 24 h as highly crystalline pale yellow prisms.
The complex was analyzed by X-ray crystallography.
Interestingly, like (S)-3c and (S)-3d , complex (S)-3f also
crystallized as two crystallographically independent
molecules in the asymmetric unit cell due to the slightly
different rotations of the phenyl rings with respect to
the coordination plane. The cationic molecule (S)-3fA
is depicted in Figure 5. The N(2)-C(15) distances of the
imino CdN bonds in the two molecules are 1.280(9) and
1.275(8) Å, repectively, for molecules A and B. The
corresponding C(16)-C(17) distances for these two
molecules are 1.331(1) and 352(8) Å (Table 2). It is
noteworthy that the N(1)-Pd-N(2) angles observed in
both molecules of (S)-3f are slightly smaller than those
observed in the complexes (S)-3c and (S)-3d . Clearly
there is no significant interchelate repulsion interaction
between the N-substituents in complex (S)-3f.
The stability of the imino-phosphine chelate in (S)-
3f was examined by heating the complex with concen-
trated sulfuric acid. It was found that the CdN bond
remained intact, and the corresponding dichloro com-
plex 4f was obtained quantitatively after LiCl was
added to the acidic solution. The complex was obtained
as pale yellow needles in 86% isolated yield. In CDCl3
the 31P NMR spectrum of 4f exhibited a sharp singlet,
at δ 55.6. The X-ray structural analysis of 4f confirmed
that the imino-phosphine remains coordinated to pal-
ladium as the P-N bidentate (Figure 6). The N(1)-C(2)
and C(3)-C(4) distances are 1.277(3) and 1.347(3) Å,
respectively (Table 1). Evidently, the imino-phosphine
chelates in the present series of palladium complexes
are stabilized by the strong metal complexation. The
free imino-phosphine ligands 5a -f could be liberated
from the corresponding dichloro complexes 4a -f by
treatment with cyanide. Ligands 5a -e are stable in
inert atmosphere, but ligand 5f decomposed rapidly in
aqueous medium. It is noteworthy that similar cyanide
treatments could not liberate the imino-phosphine
ligands directly from complexes 3a -f.
F igu r e 6. Molecular structure of complex 4f.
R-vinylic carbon atom of diphenylvinylphosphine, it is
likely that a [2+2] cycloaddition reaction mechanism
has taken place.12 Analysis of all the product complexes
also showed that the R- and one â-vinylic protons had
been eleminated from the vinylphosphine. Thus the
formation of these chelating imino-phosphine com-
plexes suggest two possible reaction pathways in the
ligand transformation process. The first possible path-
way involves the elimination of two vinylic protons from
vinylphosphine to form an alkyne function, which then
undergoes the [2+2] cycloaddition process with the
neighboring coordinated imine to generate an unstable
four-membered cyclic intermediate. The subsequent
ring-opening reaction gave the corresponding imino-
phosphine chelate. However, the proposed alkyne spe-
cies in this pathway could not be detected in the entire
ligand transformation reaction. Similarly, in the absence
of imine, we failed to oberve any alkyne formation when
(S)-2 alone was heated under similar or stronger reac-
tion conditions. In a confirmation experiment, the
diphenylvinylphosphine ligand in (S)-2 was replaced
with the analogous diphenylacetylenephosphine and
used in the coupling reaction with all the six selected
imines. However, complexes 3a -f were not produced in
these processes. The second possible reaction pathway
initially involves a [2+2] cycloaddition between vi-
nylphosphine and the neighboring CdN function, as
illustrated in Figure 7. The subsequent oxidative ring-
opening process generates the product complex as well
as the elimination of a hydrogen molecule. It is noted
that the formation of the four-membered cyclic inter-
mediate on the palladium template is a sterically
demanding step, and model studies suggest that the
(11) Martin, J . W. L.; Organ, G. J .; Wainwright, K. P.; Weerasuria,
K. D. V.; Willis, A. C.; Wild, S. B. Inorg. Chem. 1987, 26, 2963.
Duckworth, P. A.; Stephens, F. S.; Wainwright, K. P.; Weerasuria, K.
D. V.; Wild, S. B. Inorg. Chem. 1989, 28, 4531. Martin, J . W. L.;
Stephens, F. S.; Wainwright, K. P.; Weerasuria, K. D. V.; Wild, S. B.
J . Am. Chem. Soc. 1988, 110, 4346. Gomez, M.; Granell, J .; Martinez,
M. Organometallics 1997, 16, 2539. Crociani, B.; Antonaroli, S.;
Bandoli, G.; Canovese, L.; Visentin, F.; Uguagliati, P. Organometallics
1999, 18, 1137.
(12) For examples of [2+2] cycloaddition reactions invoving imines,
see: Palomo, C.; Ganboa, I.; Kot, A.; Dembkowski, L. J . Org. Chem.
1998, 63, 6398. Burwood, M.; Davies, B.; Diaz, I.; Grigg, R.; Molina,
P.; Sridharan, V.; Hughes, M. Tetrahedron Lett. 1995, 36, 9053.
Tanaka, H.; Abdul Hai, A. K. M.; Sadakane, M.; Okumoto, H.; Torii,
S. J . Org. Chem. 1994, 59, 3040.
The formation of the imino-phosphine chelates in the
present series of studies clearly does not involve the
[4+2] cycloaddition reaction. In view of the regioselec-
tive migration of the C-Ph group from imines to the

Imino-Phosphine Bidentate Chelates
Organometallics, Vol. 19, No. 18, 2000 3727
4
3
) 8.4 Hz, J PH ) 6.0 Hz, Hγ), 7.07 (d, 1H, J HH ) 8.4 Hz, Hδ),
3
7.26-7.73 (m, 23H, CdCH + aromatics), 8.25 (ddd, 2H, J HH
4
3
) 7.6 Hz, J HH ) 1.8 Hz, J PH ) 12.1 Hz, o-PPh), 8.55 (d, 1H,
3J PH ) 22.5 Hz, NdCH).
The following compounds were prepared similarly.
{(S)-1-[1-(Dim et h yla m in o)et h yl]n a p h t h yl-C2,N}{1,4-
d ip h en yl-3-d ip h en ylp h osp h in o-4-d eu t er iu m -1-a za -1,3-
bu ta d ien e-N1,P 3′}p a lla d iu m (II) p er ch lor a te, [(S)-3b]: yel-
low needles, mp 196-198 °C (dec); [R]D +212.5 (c 0.3, CH2Cl2);
33% yield. Anal. Calcd for C41H37ClDN2O4PPd: C, 61.8; H, 4.7;
N, 3.5. Found: C, 62.1; H, 5.1; N, 3.6. 31P NMR (CDCl3): δ
F igu r e 7. Proposed [2+2] cycloaddition reaction mecha-
nism for the template synthesis of the P-N chelates in
complexes (S)-3a -f.
C-Ph group must be located in a direction away from
the palladium center. Perhaps this steric requirement
accounts for the regioselectivity observed in the product
complexes: the C-Ph group is always located in the
position trans to the PPh2 moiety. It should be noted
that, however, such hetero four-membered rings are
generally stable and can be isolated. Thus, if the second
proposed pathway was indeed adopted, the palladium
center must have played an important role in the
oxidative ring-opening process. The mechanistic aspects
of this ligand transformation process will be investi-
gated further. In subsequent work, it will be shown that
the coupling reaction can be modified for the asymmetric
synthesis of optically active imino-phosphines.
3
52.2 (s). 1H NMR (CDCl3): δ 1.99 (d, 3H, J HH ) 6.0 Hz,
4
CHMe), 2.18 (d, 3H, J PH(trans) ) 3.6 Hz, NMe), 2.60 (d, 3H,
3
4J PH(trans) ) 1.6 Hz, NMe), 4.27 (qn, 1H, J HH ) 4J PH ) 6.0 Hz,
3
4
CHMe), 6.88 (dd, 1H, J HH ) 8.4 Hz, J PH ) 6.0 Hz, Hγ), 7.07
(d, 1H, 3J HH ) 8.4 Hz, Hδ), 7.32-7.73 (m, 22H, aromatics), 8.25
(dd, 2H, J HH ) 7.6 Hz, J PH ) 12.1 Hz, o-PPh), 8.56 (d, 1H,
3J PH ) 22.9 Hz, NdCH).
3
3
{(S)-1-[1-(Dim et h yla m in o)et h yl]n a p h t h yl-C2,N}{1-(p -
m eth ylp h en yl)-3-d ip h en ylp h osp h in o-4-p h en yl-1-a za -1,3-
bu ta d ien e-N1,P 3′}p a lla d iu m (II) p er ch lor a te, [(S)-3c]: yel-
low needles, mp 181-183 °C (dec); [R]D +182.9 (c 0.3, CH2Cl2);
36% yield. Anal. Calcd for C42H40ClN2O4PPd: C, 62.3; H, 5.0;
N, 3.5. Found: C, 62.0; H, 5.0; N, 3.5. 31P NMR (CDCl3): δ
3
52.6 (s). 1H NMR (CDCl3): δ 1.97 (d, 3H, J HH ) 6.4 Hz,
4
CHMe), 2.19 (d, 3H, J PH(trans) ) 3.6 Hz, NMe), 2.37 (s, 3H,
Exp er im en ta l Section
C6H4-Me), 2.62 (d, 3H, 4J PH(trans) ) 1.6 Hz, NMe), 4.30 (qn, 1H,
4
3
3J HH ) J PH ) 6.0 Hz, CHMe), 6.90 (dd, 1H, J HH ) 8.4 Hz,
Reactions involving air-sensitive compounds were performed
under a positive pressure of purified nitrogen. NMRs were
recorded at 25 °C on Bruker ACF 300 and AMX 500 spectrom-
eters. The phase-sensitive ROESY experiments were acquired
into a 1024 × 512 matrix with a 250 ms spin locking time and
a spin lock field strength such that γB1/2π ) 5000 Hz and
then transformed into 1024 × 1024 points using a sine bell
weighting function in both dimensions. Optical rotations were
measured on the specified solution in a 1 dm cell at 25 °C with
a Perkin-Elmer Model 341 polarimeter. Elemental analyses
were performed by the Elemental Analysis Laboratory of the
Department of Chemistry at the National University of
Singapore.
4J PH ) 6.0 Hz, Hγ), 7.07 (d, 1H, J HH ) 8.4 Hz, Hδ), 7.27-7.75
3
3
(m, 22H, CdCH + aromatics), 8.25 (ddd, 2H, J HH ) 7.2 Hz,
4J HH ) 2.6 Hz, J PH ) 12.1 Hz, o-PPh), 8.52 (d, 1H, J PH
)
3
3
22.5 Hz, NdCH).
{(S)-1-[1-(Dim et h yla m in o)et h yl]n a p h t h yl-C2,N}{1-(p -
ch lor op h en yl)-3-d ip h en ylp h osp h in o-4-p h en yl-1-a za -1,3-
bu ta d ien e-N1,P 3′}p a lla d iu m (II) p er ch lor a te, [(S)-3d ]: yel-
low needles, mp >210 °C (dec); [R]D +214.3 (c 0.3, CH2Cl2);
21% yield. Anal. Calcd for C41H37Cl2N2O4PPd: C, 59.3; H, 4.5;
N, 3.4. Found: C, 58.9; H, 4.4; N, 3.5.31P NMR (CDCl3): δ 51.9
3
(s). 1H NMR (CDCl3): δ 1.97 (d, 3H, J HH ) 6.4 Hz, CHMe),
4
4
2.24 (d, 3H, J PH(trans) ) 3.6 Hz, NMe), 2.60 (d, 3H, J PH(trans)
)
3
1.2 Hz, NMe), 4.27 (qn, 1H, J HH
)
4J PH ) 6.0 Hz, CHMe),
Imines were prepared according to standard literature
methods.13 The enantiomerically pure form of [SP-4-4-(S)-
chloro[1-[1-(dimethylamino)ethyl]-2-naphthalenyl-C,N][diphe-
nylvinylphosphine-P]palladium(II), (S)-1, was prepared as
previously described.3-5
3
4
6.87 (dd, 1H, J HH ) 8.4 Hz, J PH ) 6.0 Hz, Hγ), 7.07 (d, 1H,
3J HH ) 8.4 Hz, Hδ), 7.29-7.78 (m, 22H, CdCH + aromatics),
3
4
3
8.24 (ddd, 2H, J HH ) 7.2 Hz, J HH ) 1.6 Hz, J PH ) 12.1 Hz,
o-PPh), 8.52 (d, 1H, J PH ) 22.5 Hz, NdCH).
3
{(S)-1-[1-(Dim et h yla m in o)et h yl]n a p h t h yl-C2,N}{1-(p -
m et h oxyp h en yl)-3-d ip h en ylp h osp h in o-4-p h en yl-1-a za -
1,3-bu ta d ien e-N1,P 3′}p a lla d iu m (II) p er ch lor a te, [(S)-3e]:
yellow needles, mp 200-202 °C (dec); [R]D +118.4 (c 0.3,
CH2Cl2); 36% yield. Anal. Calcd for C42H40ClN2O5PPd: C, 61.1;
H, 4.9; N, 3.4. Found: C, 59.7; H, 5.1; N, 3.5. 31P NMR
Liga n d Cou p lin g Rea ction s. Syn th esis of {(S)-1-[1-
(Dim et h yla m in o)et h yl]n a p h t h yl-C2,N}{1,4-d ip h en yl-3-
diph en ylph osph in o-1-aza-1,3-bu tadien e-N1,P 3′}palladiu m -
(II) P er ch lor a te, [(S)-3a ]. A solution of the chloro complex
(S)-1 (1.0 g) in dichloromethane (40 mL) was subjected to
chloride abstraction using silver perchlorate (0.8 g) in water
(5 mL). The mixture was filtered, dried (MgSO4), and evapo-
rated to dryness, leaving a colorless glassy perchlorato species
(S)-2. The complex was then redissolved in toluene (100 mL)
and treated with N-benzylideneaniline (1.6 g) at 100 °C. The
reaction was monitored by 31P NMR spectroscopy and found
to be complete in 48 h. The solvent was removed under reduced
pressure to give a black residue. This material was chromato-
graphed on a silica column giving (S)-3a as a yellow powder.
The compound was subsequently crystallized from dichlo-
romethane-diethyl ether as yellow needles, mp 197-199 °C
(dec); [R]D +212.5 (c 0.3, CH2Cl2); 0.47 g (33% yield). Anal.
Calcd for C41H38ClN2O4PPd: C, 61.9; H, 4.8; N, 3.5. Found C,
62.1; H, 5.1; N, 3.6. 31P NMR (CDCl3): δ 52.2 (s). 1H NMR
1
3
(CDCl3): δ 52.9 (s). H NMR (CDCl3): δ 1.99 (d, 3H, J HH
)
6.4 Hz, CHMe), 2.22 (d, 3H, 4J PH(trans) ) 3.6 Hz, NMe), 2.62 (d,
4
3H, J PH(trans) ) 1.6 Hz, NMe), 3.83 (s, 3H, C6H4-OMe), 4.29
3
4
3
(qn, 1H, J HH ) J PH ) 6.0 Hz, CHMe), 6.88 (dd, 1H, J HH
)
4
8.4 Hz, J PH ) 6.0 Hz, Hγ), 7.00-7.73 (m, 20H, CdCH +
3
aromatics), 7.02 (d, 2H, J HH ) 8.9 Hz, 2xHCC-OMe), 7.07
3
3
4
(d, 1H, J HH ) 8.4 Hz, Hδ), 8.24 (ddd, 2H, J HH ) 7.0 Hz, J HH
) 1.2 Hz, 3J PH ) 12.0 Hz, o-PPh), 8.53 (d, 1H, 3J PH ) 22.5 Hz,
NdCH).
{(S)-1-[1-(Dim eth ylam in o)eth yl]n aph th yl-C2,N}{3-diph e-
n y lp h o s p h in o -4-p h e n y l-1-a za -1,3-b u t a d ie n e -N 1,P 3′}-
p a lla d iu m (II) p er ch lor a te, [(S)-3f]. The imine HNdCPh(H)
was generated in situ by heating PhCH{NdCPh(H)}2 in
toluene at 100 °C. The complex (S)-3f was isolated as yellow
needles, mp 140-141 °C (dec); [R]D +65.8 (c 0.3, CH2Cl2); 39%
yield. Anal. Calcd for C35H34ClN2O4PPd: C, 58.4; H, 4.8; N,
3.9. Found: C, 58.0; H, 5.0; N, 4.0. 31P NMR (CDCl3): δ 48.6
3
(CDCl3): δ 1.99 (d, 3H, J HH ) 6.0 Hz, CHMe), 2.18 (d, 3H,
4J PH(trans) ) 3.6 Hz, NMe), 2.60 (d, 3H, 4J PH(trans) ) 1.6 Hz, NMe),
4.27 (qn, 1H, 3J HH ) 4J PH ) 6.0 Hz, CHMe), 6.88 (dd, 1H, 3J HH
3
(s). 1H NMR (CDCl3): δ 1.87 (d, 3H, J HH ) 6.0 Hz, CHMe),
(13) Roe, A.; Montgomery, J . A. J . Am. Chem. Soc. 1953, 75, 910.
Katogiri, N.; Miura, Y.; Niwa, R.; Kato, T. Bull. Chem. Pharm. 1983,
31, 538.
4
2.94 (s, 3H, NMe), 3.17 (d, 3H, J PH(trans) ) 3.2 Hz, NMe), 4.49
3
4
3
(qn, 1H, J HH ) J PH ) 7.0 Hz, CHMe), 6.72 (dd, 1H, J HH
)

3728 Organometallics, Vol. 19, No. 18, 2000
Ta ble 3. Cr ysta llogr a p h ic Da ta for Com p lexes (S)-3c, (S)-3d , (S)-3f, 4a , 4c, a n d 4f
Liu et al.
(S)-3c
(S)-3d
(S)-3f
4a
4c
4f
formula
C
42H40ClN2O4PPd
C41H37Cl2N2O4PPd
C35H35ClN2O4PPd‚
0.5H2O
728.47
P21
monoclinic
8.379(1)
19.288(1)
22.074(1)
90
98.48(1)
90
3528.4(2)
4
C27H22Cl2NPPd‚
0.5H2O‚0.5CHCl3
637.42
C28H24Cl2NPPd
C21H18Cl2NPPd
fw
809.58
P21
830.00
P21
582.75
P(-1)
492.63
P2(1)/c
monoclinic
9.403(1)
20.901(1)
10.430(1)
90
96.96(1)
90
2034.7(1)
4
space group
cryst syst
a/Å
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
P(-1)
monoclinic
12.584(1)
12.041(1)
25.878(1)
90(1)
96.18(1)
90(1)
3889.5(1)
4
monoclinic
12.473(1)
12.014(1)
25.954(1)
90
96.79(1)
90
3861.9(1)
4
triclinic
10.015(1)
10.226(1)
15.213(1)
94.33(1)
95.22(1)
113.51(1)
1412.1(1)
2
triclinic
12.607(1)
14.535(1)
15.131(1)
79.26(1)
79.32(1)
76.34(1)
2617.7(1)
4
Z
T/K
d
293(2)
1.379
293(2)
1.428
293(2)
1.371
293(2)
1.499
223(2)
1.479
293(2)
1.608
(calcd)/g cm-3
λ/Å
0.71073
6.28
1664
0.0423
0.1139
0.71073
7.03
1696
0.0472
0.1191
0.71073
6.87
1492
0.0389
0.1120
0.71073
10.64
640
0.0335
0.1005
0.71073
9.91
1176
0.0264
0.0595
0.71073
12.58
984
0.0292
0.0603
µ/cm-1
F(000)
R1 (obs data)a
wR2 (obs data)b
2
R1 ) ∑||Fo| - |Fc||/∑|Fo|. bwR2
)
{∑[w(F 2-Fc2)2]/∑[w(Fo )2]}, w-1 ) σ2(Fo2) + (aP)2 + bP.
a
x
o
4
8.4 Hz, J PH ) 5.2 Hz, Hγ), 7.00-7.73 (m, 20H, CdCH +
aromatics), 7.14 (d, 1H, 3J HH ) 8.4 Hz, Hδ), 8.24 (ddd, 2H, 3J HH
) 7.2 Hz, 4J HH ) 1.9 Hz, 3J PH ) 12.0 Hz, o-PPh), 9.26 (dd, 1H,
4H, 3J HH ) 7.2 Hz, 3J PH ) 13.2 Hz, o-PPh), 8.42 (d, 1H, 3J PH
33.7 Hz, NdCH).
)
Dich lor o{1-(p-m eth oxyp h en yl)-3-d ip h en ylp h osp h in o-
4-ph en yl-1-aza-1,3-bu tadien e-N1,P 3′}palladiu m (II), 4e: pale
yellow prisms, mp >260 °C (dec); 90% yield. Anal. Calcd for
3
3
3J HH ) 11.6 Hz, J PH ) 25.9 Hz, NdCH), 11.0 (d, 1H, J HH
)
3
11.6 Hz, NH). The J HH coupling between the two protons in
the NHdCH function could be suppressed upon treatment of
the NMR sample with D2O.
C
28H24Cl2NOPPd: C, 56.2; H, 4.0; N, 2.3. Found: C, 55.5; H,
3.7; N, 2.6. 31P NMR (CDCl3): δ 52.1 (s). 1H NMR (CDCl3):
3.79 (s, 3H, C6H4-OMe), 7.28-7.67 (m, 16H, CdCH + aromat-
Dich lor o{1,4-d ip h en yl-3-d ip h en ylp h osp h in o-1-a za -1,3-
bu ta d ien e-N1,P 3′}p a lla d iu m (II), 4a . The naphthylamine
auxiliary in (S)-3a was removed chemoselectively by treating
the cationic complex (0.2 g) with concentrated sulfuric acid
(70%, 3 mL) for 0.5 h. The acidic solution was then poured
onto ice (ca. 15 g), and lithium chloride (0.5 g) was added. The
mixture was stirred for 1 h. Addition of dichloromethane (50
mL) gave a clear yellow organic layer, which was subsequently
separated, and the aqueous layer was extracted with dichlo-
romethane. The combined organic layer was washed with
water and then dried over anhydrous MgSO4. Removal of
solvent and recrystallization from dichloromethane-diethyl
ether gave the dichloro complex (S)-4a as pale yellow prisms:
3
ics), 6.87 (d, 2H, J HH ) 9.2 Hz, 2×HCC-OMe), 7.93 (dd, 4H,
3
3
3J HH ) 8.4 Hz, J PH ) 12.8 Hz, o-PPh), 8.40 (d, 1H, J PH
)
33.7 Hz, NdCH).
Dich lor o{3-diph en ylph osph in o-4-ph en yl-1-aza-1,3-bu ta-
d ien e-N1,P 3′}p a lla d iu m (II), 4f: pale yellow prisms, mp >250
°C (dec); 86% yield. Anal. Calcd for C21H18Cl2NPPd: C, 51.2;
H, 3.7; N, 2.8. Found: C, 50.9; H, 3.2; N, 3.1. 31P NMR
(CDCl3): δ 55.6 (s). 1H NMR (CDCl3): 7.40-7.65 (m, 12H, Cd
CH + aromatics), 7.88 (dd, 4H, 3J HH ) 9.6 Hz, 3J PH ) 13.2 Hz,
o-PPh), 8.87 (dd, 1H, 3J HH ) 10.0 Hz, 3J PH ) 38.5 Hz, NdCH),
3
11.2 (d, 1H, J HH ) 10.0 Hz, NH).
Liber a tion of Im in o-P h osp h in e Liga n d . Isola tion of
1,4-Dip h e n yl-3-d ip h e n ylp h osp h in o-1-a za -1,3-b u t a d i-
en e, 5a . A solution of 4a (0.5 g) in dichloromethane (100 mL)
was stirred vigorously with a saturated aqueous solution of
potassium cyanide (0.5 g) for 30 min. The resulting colorless
organic layer was separated, washed with water, and then
dried (MgSO4). Upon the removal of solvent, an air-stable low-
melting solid was obtained, 0.22 g (80% yield). 31P NMR
mp >210 °C (dec); 0.13 g (91% yield). Anal. Calcd for C27H22
-
Cl2NPPd: C, 57.0; H, 3.9; N, 2.5. Found: C, 57.0; H, 4.1; N,
2.7. 31P NMR (CDCl3): δ 51.7 (s). 1H NMR (CDCl3): 7.30-
3
7.67 (m, 17H, CdCH + aromatics), 7.94 (dd, 4H, J HH ) 7.6
3
3
Hz, J PH ) 12.8 Hz, o-PPh), 8.43 (d, 1H, J PH ) 33.7 Hz, Nd
CH).
The following compounds were prepared similarly.
Dich lor o{1,4-d ip h en yl-3-d ip h en ylp h osp h in o-4-d eu te-
r iu m -1-a za -1,3-bu ta d ien e-N1,P 3′}p a lla d iu m (II), 4b: pale
yellow prisms, mp >210 °C (dec); 91% yield. Anal. Calcd for
1
3
(CDCl3): δ -5.4 (s). H NMR (CDCl3): 6.77 (d, 1H, J PH ) 4.8
3
Hz, CdCH), 6.87 (d, 2H, J HH ) 8.4 Hz, m-NPh), 7.08-7.50
4
3
(m, 18H, aromatics), 8.56 (dd, 1H, J HH ) 0.8 Hz, J PH ) 8.4
Hz, NdCH).
C
27H21Cl2DNPPd: C, 56.9; H, 3.7; N, 2.5. Found: C, 56.9; H,
4.1; N, 2.7.31P NMR (CDCl3): δ 51.6 (s). 1H NMR (CDCl3):
The following compounds were prepared similarly.
3
7.30-7.67 (m, 16H, aromatics), 7.94 (dd, 4H, J HH ) 7.6 Hz,
3J PH ) 12.8 Hz, o-PPh), 8.45 (d, 1H, J PH ) 33.7 Hz, NdCH).
3
1,4-Dip h en yl-3-d ip h en ylp h osp h in o-4-d eu ter iu m -1-a za -
1,3-bu ta d ien e, 5b: pale yellow solid, 80% yield. 31P NMR
Dich lor o{1-(p-m eth ylp h en yl)-3-d ip h en ylp h osp h in o-4-
p h en yl-1-a za -1,3-bu ta d ien e-N1,P 3′}p a lla d iu m (II), 4c: pale
yellow prisms, mp >220 °C (dec); 91% yield. Anal. Calcd for
1
3
(CDCl3): δ -5.4 (s). H NMR (CDCl3): 6.80 (d, 2H, J HH ) 8.2
Hz, m-NPh), 7.08-7.56 (m, 18H, aromatics), 8.56 (dd, 1H, 4J HH
) 0.8 Hz, J PH ) 8.4 Hz, NdCH).
3
C
28H24Cl2NPPd: C, 57.7; H, 4.2; N, 2.4. Found: C, 57.5; H,
4.0; N, 2.5. 31P NMR (CDCl3): δ 51.9 (s). 1H NMR (CDCl3):
2.34 (s, 3H, C6H4-Me), 7.14-7.63 (m, 16H, CdCH + aromatics),
1-(p-Meth ylp h en yl)-3-d ip h en ylp h osp h in o-4-p h en yl-1-
a za -1,3-bu ta d ien e, 5c: pale yellow solid, 80% yield. δ -5.4
1
3
3
3
(s). H NMR (CDCl3): 2.28 (s, 3H, C6H4-Me), 6.74 (d, 1H, J PH
7.95 (dd, 4H, J HH ) 7.6 Hz, J PH ) 13.3 Hz, o-PPh), 8.40 (d,
1H, J PH ) 34.1 Hz, NdCH).
3
3
) 4.4 Hz, CdCH), 6.81 (d, 2H, J HH ) 8.2 Hz, m-NAr), 7.05
(d, 2H, 3J HH ) 8.2 Hz, o-NAr), 7.24-7.50 (m, 15H, aromatics),
Dich lor o{1-(p-ch lor op h en yl)-3-d ip h en ylp h osp h in o-4-
p h en yl-1-a za -1,3-bu ta d ien e-N1,P 3′}p a lla d iu m (II), 4d: pale
yellow prisms, mp >250 °C (dec); 89% yield. Anal. Calcd for
4
3
8.58 (dd, 1H, J HH ) 0.8 Hz, J PH ) 8.0 Hz, NdCH).
(p-Ch lor oph en yl)-3-diph en ylph osph in o-4-ph en yl-1-aza-
C
27H21Cl3NPPd‚0.5CH2Cl2: C, 51.2; H, 3.4; N, 2.2. Found: C,
1,3-bu ta d ien e 5d : pale yellow solid; 81% yield. 31P NMR
1
3
51.4; H, 3.5; N, 2.3. 31P NMR (CDCl3) δ 51.2 (s). 1H NMR
(CDCl3): 7.30-7.73 (m, 16H, CdCH + aromatics), 7.93 (dd,
(CDCl3): δ -5.5 (s). H NMR (CDCl3): 6.79 (d, 1H, J PH ) 4.4
3
Hz, CdCH), 6.79 (d, 2H, J HH ) 8.4 Hz, m-NAr), 7.19 (d, 2H,

Imino-Phosphine Bidentate Chelates
Organometallics, Vol. 19, No. 18, 2000 3729
3J HH ) 8.4 Hz, o-NAr), 7.23-7.49 (m, 15H, aromatics), 8.53
anisotropically. Hydrogen atoms were introduced at fixed
distance from carbon and nitrogen atoms and were assigned
fixed thermal parameters. The absolute configurations of all
chiral complexes were determined unambiguously using the
Flack parameter and by internal reference to the known
naphthylamine center.
3
(d, 1H, J PH ) 8.0 Hz, NdCH).
1-(p-Meth oxyp h en yl)-3-d ip h en ylp h osp h in o-4-p h en yl-
1-a za -1,3-bu ta d ien e 5e: pale yellow solid, 79% yield. 31P
NMR (CDCl3): δ -5.6 (s). 1H NMR (CDCl3): 3.75 (s, 3H, C6H4-
3
3
OMe), 6.71 (d, 1H, J PH ) 4.4 Hz, CdCH), 6.78 (d, 2H, J HH
)
3
9.2 Hz, m-NAr), 6.91 (d, 2H, J HH ) 9.2 Hz, o-NAr), 7.30-
7.49 (m, 15H, aromatics), 8.60 (dd, 1H, J HH ) 0.8 Hz, J PH
8.4 Hz, NdCH).
4
3
)
Ack n ow led gm en t. We are grateful to the National
University of Singapore for support of this research
(Grant No. RP 979905) and a research scholarship to
L.X.
Cr ysta l Str u ctu r e Deter m in a tion of (S)-3c, (S)-3d , (S)-
3f, 4a , 4c, a n d 4f. Crystal data for all six complexes and a
summary of the crystallographic analyses are given in Table
3. Diffraction data were collected on a Siemens SMART CCD
diffractometer with Mo KR radiation (graphite monochroma-
tor) using ω-scans. SADABS absorption corrections were
applied, and refinements by full-matrix least-squares were
based on SHELXL 93.14 All non-hydrogen atoms were refined
Su p p or tin g In for m a tion Ava ila ble: For (S)-3c, (S)-3d ,
(S)-3f, 4a , 4c, and 4f tables of crystal data, data collection,
solution and refinement, final positional parameters, bond
distances and angles, thermal parameters of non-hydrogen
atoms, and calculated hydrogen parameters. This material is
available free of charge via the Internet at http://pubs.acs.org.
(14) Sheldrick, G. M. SHELXL 93, Program for Crystal Structure
Refinement; University of Gottingen: Germany 1993.
OM000416L