[Pd(N,N-chelate)(olefin)] complexes containing chiral nitrogen chelates based on carbohydrates - Enantioselectivity of olefin coordination

Article abstract of DOI:10.1002/(SICI)1099-0682(199911)1999:11<1939::AID-EJIC1939>3.0.CO;2-2

Chiral N,N-chelates of formula 6-Me-pyridine-2-CH=N-R (1) and R-N=CH- CH=N-R (2) (R = 6-deoxy-α-D-glucoside or 6-deoxy-α-D-mannoside residue) and their palladium(0) complexes [Pd(N,N-chelate)(olefin)] (I) were prepared. Symmetrical type 2 ligands induced higher enantioselectivity in the coordination of prochiral olefins. The ability of a type 1 chelate to promote a stereoselective process was also assessed, i.e. dimethylfumarate inserted into the Pd-Me bond formed upon methylation of a type I complex with 50% ee. Finally, a water-soluble Pd⁰ complex was also prepared by deprotecting the alcoholic functions on the sugar residue, and its molecular structure- determined through X-ray diffractometry.

Full text of DOI:10.1002/(SICI)1099-0682(199911)1999:11<1939::AID-EJIC1939>3.0.CO;2-2

FULL PAPER
[Pd(N,N-chelate)(olefin)] Complexes Containing Chiral Nitrogen Chelates
Based on Carbohydrates – Enantioselectivity of Olefin Coordination
Maria L. Ferrara,[a] Federico Giordano,[a] Ida Orabona,[a] Achille Panunzi,[b]
and Francesco Ruffo*[a]
Dedicated to Prof. Fausto Calderazzo on the occasion of his 70th birthday
Keywords: Palladium / Bidentate nitrogen ligands / Carbohydrates / Alkenes / Enantioselectivity
Chiral N,N-chelates of formula 6-Me-pyridine–2-CH=N–R (1)
and R–N=CH–CH=N–R (2) (R = 6-deoxy-α- -glucoside or 6-
deoxy-α-
complexes [Pd(N,N-chelate)(olefin)] (I) were prepared. by deprotecting the alcoholic functions on the sugar residue,
assessed, i.e. dimethylfumarate inserted into the Pd–Me
D
bond formed upon methylation of a type I complex with 50%
D
-mannoside residue) and their palladium(0) ee. Finally, a water-soluble Pd0 complex was also prepared
Symmetrical type 2 ligands induced higher enantioselectivity
in the coordination of prochiral olefins. The ability of a type
1 chelate to promote a stereoselective process was also
and its molecular structure determined through X-ray
diffractometry.
paper we describe the synthesis of the ligands, and the prep-
aration and the solution behaviour of the complexes. The
Introduction
An important challenge that chemical sciences must meet ability of the chelates to induce enantioselective coordi-
in the forthcoming third millenium is that of making avail- nation of prochiral olefins is also discussed. Furthermore,
able chiral products by means of environmentally friendly the ability of one chelate to promote a stereoselective stoi-
processes. Organometallic chemistry may be able to fulfill chiometric process is assessed, i.e. insertion of dimethylfum-
this demand,[1] since metal-assisted enantioselective synth- arate into the PdϪMe bond formed upon oxidative ad-
eses can often reduce the consumption of resources. To dition of Me3OBF4 to a complex of type I. Finally, prep-
date, the best results have been achieved by using phos- aration of a water-soluble compound of type I by deprotect-
phanes as chiral auxiliaries of active transition metals.[2] ing the alcoholic functions on the sugar residue is reported,
However, nitrogen ligands are attracting increasing inter- along with its structure as determined through X-ray crys-
est.[3] Aiming to contribute to this growing field of research, tallography.
we investigated the feasibility of using new chiral ,-che-
lates based on carbohydrates[4] (Figure 1), with the assump-
tions that (i) these natural products can be a convenient
source of chiral auxiliaries, and (ii) both a lypophylic and a
hydrophilic form of the ligands can be available depending
on whether or not the alcoholic functions are protected. In
the latter case the environmental and economic benefits of
using the ligands in aqueos media would be added.
In a previous report[5] we described type 1 and 2 ligands
derived from α--mannose, and their alkeneϪPt0 com-
plexes. A preliminarly investigation of the ability of the li-
gands to induce stereoselective coordination of prochiral
olefins yielded encouraging results. Therefore, our studies
have been extended to the synthesis of related chelates
based on α--glucose. OlefinϪPd0 species containing nitro-
gen ligands are currently receiving a lot of attention,[6] so
[Pd(,-chelate)(olefin)] complexes I were prepared. In this
[a]
Figure 1. General formula of type 1 and 2 ligands
`
Dipartimento di Chimica, Universita di Napoli “Federico II”
Via Mezzocannone 4, I-80134 Napoli, Italia
Fax: (internat.) ϩ 39-081/5527771
E-mail: ruffo@chemna.dichi.unina.it
Facolta di Agraria and Dipartimento di Chimica, Universita di
[b]
`
`
[Pd(,-chelate)(olefin)]
Napoli “Federico II”
Via Mezzocannone 4, I-80134 Napoli, Italia
I
Eur. J. Inorg. Chem. 1999, 1939Ϫ1947
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
1434Ϫ1948/99/1111Ϫ1939 $ 17.50ϩ.50/0
1939

M. L. Ferrara, F. Giordano, I. Orabona, A. Panunzi, F. Ruffo
FULL PAPER
The latter contribution plays a prominent role in Pd0- and
Pt0-olefin complexes, and, for this reason, their stability in-
creases as the electron-acceptor properties of the alkene
grow.[6a,6d,6e]
Results and Discussion
Synthesis and Characterization of the Ligands
The synthesis of the ,-chelates is depicted in Scheme
1. The compounds are identified by a number followed by
In the presence of good donor ligands,[6e,12] such as type
a capital letter, which indicates the sugar (M ϭ mannose or 1 or 2 diimines, a satisfactory electronic balance within the
G ϭ glucose), and by the specification of the R substituent complex is met only if the alkene is able to withdraw effec-
(Me or Ph). The symmetry of ligands of type 1 and 2 is C1 tively electron density from the metal centre through π back
and C2, respectively. For both types three different deriva- donation. Hence, stable type I complexes could be obtained
tives were obtained. Among derivatives of type 1, 1G-Ph only with olefins bearing good electron-acceptor substitu-
and 1M-Ph differ by the nature of the carbohydrate (respec- ents. Dimethylfumarate (dmf), fumarodinitrile (fdn), and
tively glucose and mannose), substituents being equal. 1G- maleic anhydride (ma) were effectively used. The synthesis
Me and 1G-Ph are both based on glucose, while the R sub- of the complexes was performed by reacting [Pd(dba)2][13]
stituent in position 4 is different. Analogous considerations (dba ϭ dibenzylideneacetone) with the chelate and the ole-
hold true for ligands of type 2.
fin in dry toluene (Equation 1). The products were obtained
Scheme 1
Known procedures allowed the synthesis of methyl-2,3,4- in pure form after column chromatography as yellow to or-
tri-O-acetyl-6-azido-6-deoxy-α--glucoside
(3G-Me),[7] ange microcrystalline powders.
methyl-2,3-di-O-acetyl-4-O-benzoyl-6-azido-6-deoxy-α--
glucoside (3G-Ph),[8][9] methyl-2,3-di-O-acetyl-4-O-benzoyl-
6-azido-6-deoxy-α--mannoside (3M-Ph)[9] by starting
from the corresponding commercial methyl-α--piranos-
ides. Reaction of these azides with PMePh2 afforded the
iminophosphoranes 4,[10] which were converted in situ into
type 1 or type 2 ligands by condensation with, respectively,
6-methyl-2-pyridinecarboxaldehyde or glyoxal. The ligands
were obtained in pure form as white powders by column
chromatography. Their characterization was performed
through NMR spectroscopy, elemental analysis and optical
activity measurements (see Experimental Section).
[Pd(dba)2] ϩ ,-chelate ϩ olefin Ǟ I ϩ 2 dba
(1)
Alternatively, fdn or ma derivatives could be synthetized
by substituting dmf in I according to Equation 2.
[Pd(,-chelate)(dmf)] ϩ ma Ǟ [Pd(,-chelate)(ma)] ϩ dmf (2)
Only with ligands 1 was it possible to obtain dmf com-
plexes of type I in acceptable yields, while in the presence
of chelates 2 dmf complexes displayed little stability. These
results probably reflect the electronic features of both the
alkenes and the ,-chelates. Actually, fdn and ma show
similar electron-withdrawing abilities, both more pro-
nounced than that displayed by dmf.[6d,14] Furthermore, ac-
cording to previous studies,[12] ligands 2 are expected to be
better σ donors than ligands 1 where one nitrogen atom
belongs to a pyridine ring. Therefore, it seems reasonable
that the above-mentioned good electronic balance within
Synthesis of [Pd(N,N-chelate)(olefin)] Complexes (I)
It is known[11] that the metalϪalkene bond can be de- the complex can be achieved only in the presence of fdn
scribed in terms of a σ donation from the filled alkene π or- or ma.
bital to an empty metal orbital, and a π back donation from
Type I complexes can be handled in air and were stored
a filled metal orbital to the empty π* orbital of the alkene. for long time at 233 K without appreciable decomposition.
1940
Eur. J. Inorg. Chem. 1999, 1939Ϫ1947

[Pd(N,N-chelate)(olefin)] Complexes Containing Chiral Nitrogen Chelates
FULL PAPER
They were fairly soluble in chlorinated solvents or toluene, sociation (with the opposite enantioface) to Pd. Spectra re-
but were poorly soluble in ether and insoluble in hexane. corded at 298 K displayed separated signals for the dia-
Complexes of type 1 ligands were stable in solution, while stereomers, which indicates that their interconversion, and
a slow decomposition process (days to completion) leading hence olefin dissociation, is slow[16] at room temperature.
to Pd, ,-chelate and free olefin was monitored for type I At 328 K the spectra showed little difference with respect
complexes containing ligands 2.
to those recorded at room temperature, but for variation of
the olefin patterns due to the increased rate of alkene ro-
tation. However, when an excess of olefin was added, the
signals broadened even at room temperature. Two excep-
tions were [Pd(2G-Me)(fdn)], for which it was necessary to
raise the temperature in order to observe broad olefin sig-
nals, and [Pd(1G-Me)(dmf)], whose spectrum at 328 K dis-
played averaged signals for the diastereomers even in the
absence of free dmf. This spectral evidence indicates that
the rate of alkene dissociationϪreassociation is increased
by the presence of free unsaturated ligand, according to an
associative mechanism.[6d,6e]
NMR Spectroscopy
Large high-field shift [∆δ(1H) у 3 ppm, ∆δ(13C) у
90 ppm] of both olefin protons and carbons was observed
in the NMR spectra (Tables 1 and 2) according to a re-
markable π back donation contribution to the PdϪalkene
bond. As expected, the shift[15] was more pronounced for
maleic anhydride and fumarodinitrile, which display the
better electron-acceptor properties.
The two halves of dmf or fdn in each one of the dia-
stereomers containing either 1M-Ph or 1G-Me appeared
not to be equivalent at 298 K, i.e. olefin protons gave rise to
doublets or AB quartets and/or the corresponding carbons
resonated separately. This result indicates that at room tem-
perature olefin rotation is also slow, since a fast rotation
would exchange the two halves of the unsaturated ligand.
As expected, olefin resonances broadened in the spectra at
328 K, due to a fastened olefin rotation.
NMR spectra also allowed information to be gained on
the solution behaviour of species of type I. Previous stud-
ies[6d,6e] disclosed that [Pd(,-chelate)(olefin)] complexes
can be involved in dynamic processes in solution, i.e. olefin
dissociation/association and olefin rotation around the met-
alϪalkene axis. The rate of both processes decreases as the
bulkiness of the ,-ligand and/or the electron-accepting
properties of the alkene grow.
For a given complex of type I the number of possible
isomers and their symmetry depend on the geometry of
On the other hand, the room-temperature NMR spectra
both the alkene and the ,-chelate. Prochiral olefins (dmf of [Pd(1G-Ph)(fdn)] showed a symmetrical olefin in one of
or fdn, C2h symmetry) can afford two diastereomers de- the two diastereomers. This suggests that olefin rotation
pending on whether the alkene coordinates re or si. They may or may not be hindered, according to which enanti-
can interconvert by dissociation of the alkene and its reas- oface is coordinated. At 328 K olefin rotation also becomes
1
Table 1. Selected H-NMR data[a] for [Pd(N,N-chelate)(olefin)] complexes
Complex
NϭCH
HCϭCH
6-Me-py
MeCO2
[Pd(1M-Ph)(dmf)] isomer, 55%
[Pd(1M-Ph)(dmf)] isomer, 45%
[Pd(1M-Ph)(ma)] isomer, 60%
[Pd(1M-Ph)(ma)] isomer, 40%
[Pd(1M-Ph)(fdn)] isomer, 55%
[Pd(1M-Ph)(fdn)] isomer, 45%
[Pd(1G-Ph)(dmf)] isomer, 55%
[Pd(1G-Ph)(dmf)] isomer, 45%
[Pd(1G-Ph)(fdn)] isomer, 55%
[Pd(1G-Ph)(fdn)] isomer, 45%
[Pd(1G-Me)(dmf)] isomer, 55%
[Pd(1G-Me)(dmf)] isomer, 45%
[Pd(1G-Me)(fdn)] isomer, 85%
[Pd(1G-Me)(fdn)] isomer, 15%
[Pd(2M-Ph)(fdn)] isomer, 70%
[Pd(2M-Ph)(fdn)] isomer, 30%
[Pd(2M-Ph)(ma)]
8.32 (1 H)
8.40 (1 H)
8.29 (1 H)
8.34 (1 H)
8.42 (1 H)
8.30 (1 H)
8.29 (1 H)
8.32 (1 H)
8.38 (1 H)
8.29 (1 H)
8.32 (1 H)
8.27 (1 H)
8.38 (1 H)
8.33 (1 H)
8.06 (2 H)
8.03 (2 H)
7.92 (2 H)
3.84 (ABq, 2 H)
3.84 (ABq, 2 H)
4.1Ϫ3.8 (m, 2 H)
2.71 (3 H)
2.73 (3 H)
2.66 (3 H)
2.68 (3 H)
2.87 (3 H)
2.67 (3 H)
2.71 (3 H)
2.72 (3 H)
2.85 (3 H)
2.63 (3 H)
2.79 (3 H)
2.82 (3 H)
2.90 (3 H)
2.90 (3 H)
2.18 (3 H), 1.88 (3 H)
2.18 (3 H), 1.88 (3 H)
2.18 (3 H), 1.88 (3 H)
4.1Ϫ3.8 (m, 2 H)
2.18 (3 H), 1.89 (3 H)
[b,c]
2.18 (3 H), 1.90 (3 H)
[b,c]
[d]
2.18 (3 H), 1.87 (3 H)
2.07 (3 H), 1.90 (3 H)
[d]
2.09 (3 H), 1.90 (3 H)
[e,c]
[e,c]
[f,c]
[f,c]
2.09 (3 H), 1.91 (3 H)
2.09 (3 H), 1.88 (3 H)
2.14 (3 H), 2.06 (3 H), 2.02 (3 H)
2.14 (3 H), 2.05 (3 H), 2.03 (3 H)
2.16 (3 H), 2.07 (3 H), 2.02 (3 H)
2.05 (3 H), 2.02 (3 H), 1.99 (3 H)
2.16 (6 H), 1.90 (6 H)
2.91 (2 H)
[d]
2.93 (2 H)
2.86 (2 H)
2.15 (6 H), 1.86 (6 H)
3.93 (d, 1 H), 3.78 (d, 1 H)
2.93 (2 H)
2.18 (6 H), 1.90 (6 H)
[Pd(2G-Ph)(fdn)] isomer, 75%
[Pd(2G-Ph)(fdn)] isomer, 25%
[Pd(2G-Me)(fdn)] isomer, 97%
[Pd(1M*)(fdn)] isomer, 55%[g]
[Pd(1M*)(fdn)] isomer, 45%[g]
8.05 (2 H)
2.08 (6 H), 1.90 (6 H)
[d]
2.86 (2 H)
2.08 (6 H), 1.87 (6 H)
8.10 (2 H)
8.74 (1 H)
8.71 (1 H)
2.89 (2 H)
2.11 (6 H), 2.05 (6 H), 2.01 (6 H)
[h]
2.88 (3 H)
2.91 (3 H)
[h]
[a]
At 298 K and 250 MHz. In CDCl3, CHCl3 (δ ϭ 7.26) as internal standard. The following abbreviations are used for describing NMR
[b]
multiplicities: app, apparent; no attribute, singlet; d, doublet; ABq, AB quartet; m, multiplet. Ϫ
The olefin protons resonate at δ ϭ
[c]
2.91 (ABq, 2 H) and 2.89 (app d, 2 H). Ϫ
Due to the similar abundance of the diastereomers the signals cannot be attributed
[d]
[e]
[f]
unequivocally. Ϫ
Hidden by other signals. Ϫ The olefin protons resonate at δ ϭ 2.87 (2 H) and 2.91 (ABq, 2 H). Ϫ The olefin
[g] [h]
protons resonate at δ ϭ 3.82 (2 H) and 3.63 (m, 2 H). Ϫ
resonate at δ ϭ 3.24 (app d, 2 H) and 3.18 (ABq, 2 H).
In D2O, HDO (δ ϭ 4.80) as internal standard. Ϫ
The olefin protons
Eur. J. Inorg. Chem. 1999, 1939Ϫ1947
1941

M. L. Ferrara, F. Giordano, I. Orabona, A. Panunzi, F. Ruffo
FULL PAPER
Table 2. Selected 13C-NMR data[a] for [Pd(N,N-chelate)(olefin)] complexes
Complex
NϭCH
OCH(OMe)
NCH2
HCϭCH
[Pd(1M-Ph)(dmf)] isomer, 55%
[Pd(1M-Ph)(dmf)] isomer, 45%
[Pd(1M-Ph)(ma)] isomer, 60%
[Pd(1M-Ph)(ma)] isomer, 40%
[Pd(1M-Ph)(fdn)] isomer, 55%
[Pd(1M-Ph)(fdn)] isomer, 45%
[Pd(1G-Ph)(dmf)] isomer, 55%
[Pd(1G-Ph)(dmf)] isomer, 45%
[Pd(1G-Ph)(fdn)] isomer, 55%
[Pd(1G-Ph)(fdn)] isomer, 45%
[Pd(1G-Me)(dmf)] isomer, 55%
[Pd(1G-Me)(dmf)] isomer, 45%
[Pd(1G-Me)(fdn)] isomer, 85%
[Pd(2M-Ph)(fdn)] isomer, 70%
[Pd(2M-Ph)(fdn)] isomer, 30%
[Pd(2M-Ph)(ma)]
165.2 (1 C)
165.4 (1 C)
165.4 (1 C)
165.6 (1 C)
165.7 (1 C)
165.3 (1 C)
170.4 (1 C)
170.4 (1 C)
165.8 (1 C)
165.4 (1 C)
162.3 (1 C)
165.4 (1 C)
165.5 (1 C)
161.5 (2 C)
160.4 (2 C)
161.3 (2 C)
161.7 (2 C)
160.5 (2 C)
161.6 (2 C)
161.5 (1 C)
161.5 (1 C)
98.3 (1 C)
98.5 (1 C)
98.5 (1 C)
98.6 (1 C)
98.5 (1 C)
98.8 (1 C)
96.3 (1 C)
96.3 (1 C)
96.8 (1 C)
96.7 (1 C)
96.4 (1 C)
96.0 (1 C)
96.5 (1 C)
98.7 (2 C)
98.5 (2 C)
98.6 (1 C), 98.4 (1 C)
96.8 (2 C)
96.7 (2 C)
96.6 (2 C)
101.1 (1 C)
100.7 (1 C)
64.9 (1 C)
63.9 (1 C)
64.9 (1 C)
64.1 (1 C)
63.4 (1 C)
65.1 (1 C)
64.8 (1 C)
63.9 (1 C)
63.2 (1 C)
65.0 (1 C)
63.0 (1 C)
64.4 (1 C)
62.9 (1 C)
63.3 (2 C)
64.7 (2 C)
65.0 (1 C), 63.9 (1 C)
63.4 (2 C)
64.6 (2 C)
63.4 (2 C)
63.3 (1 C)
64.7 (1 C)
41.6 (1 C), 41.3 (1 C)
42.1 (1 C), 41.2 (1 C)
[b,c]
[b,c]
[d,c]
[d,c]
[e,c]
[e,c]
[f,c]
[f,c]
42.0 (1 C), 41.5 (1 C)
42.4 (1 C), 41.2 (1 C)
18.4 (1 C), 18.2 (1 C)
19.4 (2 C)
19.1 (2 C)
42.4 (1 C), 42.0 (1 C)
19.5 (2 C)
[Pd(2G-Ph)(fdn)] isomer, 75%
[Pd(2G-Ph)(fdn)] isomer, 25%
[Pd(2G-Me)(fdn)] isomer, 97%
[Pd(1M*)(fdn)] isomer, 55%
[Pd(1M*)(fdn)] isomer, 45%
19.2 (2 C)
19.4 (2 C)
[g,c]
[g,c]
[a]
[b]
At 298 K and 62.9 MHz. In CDCl3, 13CDCl3 (δ ϭ 77.0) as internal standard. Ϫ The olefin carbon atoms resonate at δ ϭ 41.4 (1
[c]
[d]
C), 41.0 (2 C), 40.7 (1 C). Ϫ Due to the similar abundance of the diastereomers the signals cannot be attributed unequivocally. Ϫ
[e]
The olefin carbon atoms resonate at δ ϭ 18.3 (3 C), 17.7 (1 C). Ϫ The olefin carbon atoms resonate at δ ϭ 42.1 (1 C), 41.6 (1 C),
[f]
[g]
41.2 (2 C). Ϫ The olefin carbon atoms resonate at δ ϭ 18.3 (2 C), 18.1 (1 C), 17.6 (1 C). Ϫ The olefin carbon atoms resonate at
δ ϭ 17.4 (3 C), 17.1 (1 C).
fast in the more stereochemically rigid isomer. A similar could be measured by integrating suitable peaks (Table 3).
situation holds true for [Pd(1G-Ph)(dmf)].
The ratio was neither affected by prolonged standing in
No information concerning olefin rotation was available solution nor by the presence of free olefin, which merely
from NMR spectra of dmf or fdn derivatives containing increased the rate of interconversion of the diastereomers
ligands of type 2. Actually, since the complexes display C2 (see above). These observations indicate that equilibrium is
symmetry, all the nuclei related by the twofold axis are ex- reached within a few seconds from dissolution of the
pected to be equivalent.
samples. Analogous platinum compounds[5] require several
Maleic anhydride (C2v symmetry) affords complex minutes before equilibrium is attained.
[Pd(1M-Ph)(ma)] in two isomeric forms, which can in-
Table 3. Diastereomeric equilibrium composition[a] for complexes
terconvert by either olefin rotation or dissociation/reassoci-
ation of the alkene. Since the isomers are separately ob-
served in both spectra, it can be inferred that both motions
are hindered at room temperature. At 328 K the proton
spectrum consists of a unique broad pattern due to fast
interconversion of the diastereomers. Conversely, complex
of type I with prochiral olefins
Complex
Composition
[Pd(1M-Ph)(dmf)]
[Pd(1M-Ph)(fdn)]
[Pd(1G-Ph)(dmf)]
[Pd(1G-Ph)(fdn)]
[Pd(1G-Me)(dmf)]
[Pd(1G-Me)(fdn)]
[Pd(2M-Ph)(fdn)]
[Pd(2G-Ph)(fdn)]
[Pd(2G-Me)(fdn)]
[Pd(1M*)(fdn)][b]
55:45
55:45
55:45
55:45
55:45
85:15
70:30
75:25
97:3
1
[Pd(2M-Ph)(ma)] exists as a unique isomer. Both H- and
13C-NMR spectra show an unsymmetrical olefin, thus dem-
onstrating that dissociation/reassociation of the alkene is
slow at 298 K. Also the rotation of the alkene is hindered
at room temperature, as suggested by the nonequivalence
of the two halves of the N,N-ligand in the carbon spectrum.
On raising the temperature to 328 K olefin rotation be-
comes fast, as suggested by the presence of a symmetric and
sharp proton pattern for the N,N-chelate.
55:45
[a]
[b]
In CDCl3 at 298 K. Ϫ In D2O at 298 K.
An inspection of Table 3 reveals that the most relevant
result concerning enantioselectivity was obtained in the case
of [Pd(2G-Me)(fdn)]. The ratio between the diastereomers
was estimated to be 97:3, indicating a strong preference for
the coordination of one enantioface. Discrimination was
Enantioselectivity of Olefin Coordination
As mentioned above, the coordination of prochiral olef- also observed for the same olefin in the presence of either
ins to the [Pd(N,N-chelate)] moiety gives rise to two dia- 2G-Ph or 2M-Ph, although to a lesser extent, affording dia-
stereomers according to which enanantioface is bound to stereomeric ratios of 75:25 and 70:30, respectively. These
the metal centre. Fresh solutions of complexes of type I results reveal that changing the 4-substituent on the gluco-
displayed the presence of both diastereomers, whose ratio side residue (2G-Me vs 2G-Ph) plays a more important role
1942
Eur. J. Inorg. Chem. 1999, 1939Ϫ1947

[Pd(N,N-chelate)(olefin)] Complexes Containing Chiral Nitrogen Chelates
FULL PAPER
than variation of the carbohydrate residue itself (2G-Ph vs media.[19] During this work we successfully attempted the
2M-Ph). Among ligands 1, only 1G-Me competes with the synthesis of a water-soluble type I complex by deprotecting
symmetrical chelates, giving rise to a diastereomeric ratio the alcoholic functions in the sugar residue of the ligand.
of 85:15 in the presence of fdn. Conversely, the other li- Treatment of [Pd(1M-Ph)(fdn)] with a catalytic amount of
gands of type 1 induce little preference for one enantioface sodium methoxide in methanol resulted in quantitative hy-
of dmf or fdn. It is also noteworthy that the values of dia- drolysis of the ester groups of the carbohydrate residue
stereomeric excesses reported in Table 3 are very close to (Scheme 2).
those measured for corresponding Pt0 complexes containing
the same ligands,[5][17] as observed for other related M0
compounds.[6e,18]
These findings indicate that type 2 ligands prompt more
effectively enantioselective coordination of trans-olefins. It
is also observed that 1G-Me and 2G-Me, both based on a
glucoside having acetyl groups as substituents, display the
Scheme 2
better discriminating properties within the corresponding
class. However, the complexity of the ligands in terms of
both steric and electronic features does not allow an easy
rationalization of the factors which determine these results.
The corresponding product [Pd(1M*)(fdn)] could be iso-
lated in high yield by adding diethyl ether to the reaction
mixture. The most prominent feature of the complex is its
solubility in both lypophilic (e.g. chloroform) and hydro-
phylic (e.g. water or methanol) solvents. Analogous to its
parent derivative, the complex exists in solution as an equi-
librium mixture of two diastereomers in 55:45 ratio.
Synthesis and X-ray Structure of the Water-Soluble
Complex [Pd(1M*)(fdn)]
Water-soluble Pd0 complexes have recently attracted at-
The X-ray solid-state structure of the complex was deter-
tention due to their possible use as catalysts in aqueous mined. Crystallization from methanol/diethyl ether yielded
Figure 2. ORTEP view of [Pd(1M*)fdn] showing the atom labelling scheme
Eur. J. Inorg. Chem. 1999, 1939Ϫ1947
1943

M. L. Ferrara, F. Giordano, I. Orabona, A. Panunzi, F. Ruffo
FULL PAPER
single crystals only for one of the two diastereomers. An the metal in a regular arrangement. The two PdϪC bond
ORTEP drawing of this molecule with the atom labelling lengths are equal, within the experimental error [average
˚
scheme is shown in Figure 2. Relevant geometric param- value 2.045(20) A], and compare well with the values found
eters are given in Table 4.
in Pd complexes of α-diimines with electron-poor
olefins.[6c,6e] The lengthening of the olefinic bond
˚
Table 4. Selected geometrical parameters for [Pd(1M*)-
(fdn)]·MeOH[a]
[C(15)ϪC(16) 1.46(3) A], and the large out-of-plane dis-
placements of the cyano groups [the torsion angle
C(17)ϪC(15)ϪC(16)ϪC(18) being 145(2)°] compared with
˚
Bond lengths [A]
˚
the value of 1.34 A for the free alkene provide clear evi-
PdϪN(2)
2.11(1)
2.17(1)
2.05(2)
2.04(2)
1.38(3)
1.46(3)
1.43(2)
1.19(3)
1.40(3)
1.37(2)
1.17(3)
1.27(2)
1.34(2)
1.53(2)
1.46(2)
dence of a rehybridization towards sp3 of the olefinic car-
bon atoms upon coordination, in keeping with the substan-
tial π back donation from the metal (see above).
PdϪN(1)
PdϪC(15)
PdϪC(16)
C(15)ϪC(17)
C(15)ϪC(16)
C(1)ϪC(2)
C(17)ϪN(3)
C(16)ϪC(18)
N(1)ϪC(2)
C(18)ϪN(4)
N(2)ϪC(1)
N(1)ϪC(6)
C(8)ϪC(9)
N(2)ϪC(8)
Addition of Me3OBF4 to [Pd(1G-Ph)(dmf)]
Use in catalysis of type I complexes seems plausible.[6f]
As organic processes promoted by Pd0 species often involve
oxidative addition to PdII and/or (stereoselective) insertion
of unsaturated substrates into PdIIϪalkyl bonds, a prelimin-
arly investigation of the feasibility of stoichiometric reac-
tions of this kind in the coordination environment provided
by a chelate of type 1 was made.
Bond angles [°]
N(1)ϪPdϪN(2)
77.5(5)
41.8(7)
122.3(6)
118.3(6)
69(1)
We previously reported[20] that [Pd(1,10-phen)(dmf)] re-
acts with Me3OBF4 affording the cyclometallated PdII
product [Pd{CH(CO2Me)CHMe(COaOMe)}(1,10-phen)-
(PdϪOa)]BF4. The process proceeds in two steps, i.e. (i) oxi-
dative addition of the oxonium salt to the Pd0 complex af-
fording the PdIIϪMe bond, and (ii) olefin insertion with
attainment of a stereogenic carbon atom bound to Pd.
The analogous reaction was performed on [Pd(1G-
Ph)(dmf)] (Scheme 3). The process was monitored through
NMR spectroscopy and was complete within 24 hours at
room temperature affording 5. The trans arrangement of
the carbonyl group with respect to the N-imino atom was
assigned, taking into account the well-established geometry
of a closely related PtII species.[5] The presence of two dia-
stereomers in 75:25 ratio indicates that the reaction had oc-
curred with significant stereoselectivity.
C(15)ϪPdϪC(16)
N(1)ϪPdϪC(15)
N(2)ϪPdϪC(16)
PdϪC(15)ϪC(16)
PdϪC(16)ϪC(15)
C(16)ϪC(15)ϪC(17)
C(15)ϪC(16)ϪC(18)
N(3)ϪC(17)ϪC(15)
N(4)ϪC(18)ϪC(16)
PdϪN(1)ϪC(2)
69(1)
113(2)
114(2)
173(3)
179(2)
112(1)
114(1)
122(1)
126(1)
120(1)
110(1)
PdϪN(2)ϪC(1)
N(2)ϪC(1)ϪC(2)
PdϪN(2)ϪC(8)
C(1)ϪN(2)ϪC(8)
N(2)ϪC(8)ϪC(9)
Torsional angles [°]
PdϪC(16)ϪC(15)ϪC(17)
PdϪC(15)ϪC(16)ϪC(18)
PdϪN(2)ϪC(8)ϪC(9)
N(2)ϪC(8)ϪC(9)ϪO(1)
C(17)ϪC(15)ϪC(16)ϪC(18)
110(1)
105(1)
56(2)
62(1)
Ϫ145(2)
[a]
ESDs in parentheses.
As expected[6e] for zerovalent [Pd(N,N-chelate)(olefin)]
complexes the coordination geometry at Pd is trigonal
planar. The coordination plane includes the pyridine ring.
In fact, the atoms Pd, N(1), N(2), C(15), C(16), C(1), C(2),
C(3), C(4), C(5), C(6), C(7), C(8) are coplanar within
Scheme 3
˚
0.06(2) A. The sugar residue adopts the expected chair con-
formation and its mean plane is almost orthogonal to the
coordination plane. As a consequence of the chemical non-
˚
equivalence, the bond lengths PdϪN(1) [2.17(1) A] and
Conclusion
˚
PdϪN(2) [2.11(1) A] are slightly, but significantly, different,
and lie at the extremes of the range commonly found in Pd/
This work demonstrated the reasonable feasibility of syn-
α-diimine complexes,[6a,6c,6e] the shorter bond being adjac- thesising chiral diimino ligands based on carbohydrates. Re-
ent to the double bond C(1)ϪN(2). The bite angle sults of preliminary investigations into their ability in in-
N(1)ϪPdϪN(2) [77.5(5)°] is very close to that found for ducing enantioselective processes were promising results,
most bidentate nitrogen ligands.[6c,6e] The olefin is bound to with Pd0 complexes with prochiral olefins being prepared
1944
Eur. J. Inorg. Chem. 1999, 1939Ϫ1947

[Pd(N,N-chelate)(olefin)] Complexes Containing Chiral Nitrogen Chelates
FULL PAPER
Ph and 1G-Me the solvent was removed under vacuum and the
residue was dissolved in 5 mL of dry toluene containing 4-A molec-
stereoselectively and achievement of a stoichiometric asym-
metric insertion process. A rare example of a chiral Pd0
water-soluble complex was also provided by deprotecting
the alcoholic groups of the carbohydrate residue in one li-
gand, and its structure determined through X-ray dif-
fractomety.
˚
ular sieves. To the solution was added 6-methyl-2-pyridinecarboxal-
dehyde (0.12 g, 1.0 mmol), and after 1 h of stirring at 363 K the
solvent was removed under vacuum. In the case of 2G-Ph and 2G-
Me, after formation of 4 was complete, glyoxal (40% w/w in water,
0.5 mmol) was added to the dichloromethane solution, followed by
sodium sulphate. After 15 minutes the reaction mixture was filtered
and the solvent removed under vacuum. In all cases, the crude reac-
tion products were filtered through a column of Florisil (15 ϫ
1.5 cm) with ethyl acetate/petroleum ether, 1:1 to give the products
as white glassy solids (yield: 60Ϫ70%). Ϫ Selected 1H-NMR reson-
ances (in CDCl3, at 250 MHz): 1G-Ph: δ ϭ 8.32 (1 H, CHϭN),
5.75 (t, 1 H), 5.35 (t, 1 H), 5.00 (m, 1 H), 4.93 (1 H), 4.29 (m, 1
H), 3.90 (d, 1 H), 3.75 (dd, 1 H), 3.36 (3 H, OMe), 2.55 (3 H, Me-
py), 2.07 (3 H, MeCO2), 1.90 (3 H, MeCO2); 1G-Me: δ ϭ 8.32 (1
H, CHϭN), 5.50 (m, 1 H), 5.10 (t, 1 H), 4.88 (m, 2 H), 4.15 (m, 1
H), 3.84 (d, 1 H), 3.66 (dd, 1 H), 3.33 (3 H, OMe), 2.56 (3 H, Me-
py), 2.05 (3 H, MeCO2), 2.02 (3 H, MeCO2), 2.00 (3 H, MeCO2);
2G-Ph: δ ϭ 7.78 (2 H, CHϭN), 5.70 (t, 2 H), 5.27 (t, 2 H), 4.95
(m, 4 H), 4.23 (m, 2 H), 3.77 (dd, 2 H), 3.59 (dd, 2 H), 3.40 (6 H,
OMe), 2.08 (6 H, MeCO2), 1.89 (6 H, MeCO2); 2G-Me: δ ϭ 7.88
(2 H, CHϭN), 5.47 (t, 2 H), 5.05 (t, 2 H), 4.87 (m, 4 H), 4.08 (m,
2 H), 3.75 (dd, 2 H), 3.57 (dd, 2 H), 3.35 (6 H, OMe), 2.05 (6 H,
MeCO2), 2.01 (6 H, MeCO2), 1.98 (6 H, MeCO2). Ϫ Selected 13C-
NMR resonances (in CDCl3, at 62.9 MHz): 1G-Ph: δ ϭ 164.8 (1
C, CHϭN), 96.4 (1 C, C1 of glucoside), 71.1, 71.0, 70.0 and 68.4
(4 C, C2-C5 of glucoside), 61.2 (1 C, NCH2), 55.1 (1 C, OMe), 24.2
(1 C, Me-py), 20.7 (1 C, MeCO2), 20.6 (1 C, MeCO2); 1G-Me: δ ϭ
164.9 (1 C, CHϭN), 96.4 (1 C, C1 of glucoside), 71.0, 70.4 and
68.1 (4 C, C2-C5 of glucoside), 60.9 (1 C, NCH2), 55.1 (1 C, OMe),
24.1 (1 C, Me-py), 20.7 (3 C, MeCO2); 2G-Ph: δ ϭ 164.2 (2 C,
CHϭN), 96.6 (2 C, C1 of glucosides), 71.1, 70.9, 69.9, 68.3 (8C,
C2-C5 of glucosides), 61.2 (2 C, NCH2), 55.3 (2 C, OMe), 20.8 (2
C, MeCO2), 20.6 (2 C, MeCO2); 2G-Me: δ ϭ 164.3 (2 C, CHϭN),
96.5 (2 C, C1 of glucosides), 70.9, 70.3, 67.9 (8C, C2-C5 of gluco-
sides), 60.8 (2 C, NCH2), 55.2 (2 C, OMe), 20.7 (6 C, MeCO2). Ϫ
Experimental Section
General: NMR spectra were recorded with a 250-MHz spec-
trometer (Bruker Model AC-250). The solvents were CDCl3
[CHCl3 (δ ϭ 7.26) and CDCl3 (δ ϭ 77.0) as standards for 1H and
13C spectra, respectively] and CD3NO2 [CD2HNO2 (δ ϭ 4.33) and
13CD2HNO2 (d ϭ 62.9) as standards for 1H and 13C spectra,
respectively]. Optical activity measurements were performed with a
PerkinϪElmer Polarimeter (Model 141). The following abbrevi-
ations are used for describing NMR multiplicities: d, doublet; dd,
double doublet; dt, double triplet; m, multiplet; no attribute, sing-
let; t, triplet. Ϫ Compounds 3G-Me,[7] methyl-2,3-di-O-acetyl-4-O-
benzoyl-6-bromo-6-deoxy-α--glucoside,[8] 1M-Ph,[5] 2M-Ph[5] and
[Pd(dba)2][13] were prepared according to published methods. Tolu-
ene was distilled from sodium, dichloromethane from calcium hy-
dride, and methanol from magnesium immediately before use. Ϫ
Elemental analysis for the new compounds are collected in Table 5.
3G-Ph: The compound was prepared in 80% yield as described for
3M-Ph[9] by starting from methyl-2,3-di-O-acetyl-4-O-benzoyl-6-
bromo-6-deoxy-α--glucoside.[8]
Ϫ
1H-NMR resonances (in
CDCl3, at 250 MHz): δ ϭ 7.97 (d, 2 H), 7.57 (t, 1 H), 7.45 (t, 2
H), 5.68 (t, 1 H), 5.22 (t, 1 H), 5.02 (d, 1 H), 4.95 (dd, 1 H), 4.08
(m, 1 H), 3.48 (3 H, OMe), 3.40 (m, 2 H), 2.09 (3 H, MeCO2), 1.89
(3 H, MeCO2). Ϫ Selected 13C-NMR resonances (in CDCl3, at
62.9 MHz): δ ϭ 96.7 (1 C, C1 of glucoside), 70.9, 70.2, 69. 4, 68.9
(4 C, C2ϪC5 of glucoside), 55.6 (1 C, OMe), 51.1 (1 C, NCH2),
20.7 (1 C, MeCO2), 20.6 (1 C, MeCO2).
1G-Ph, 1G-Me, 2G-Ph, and 2G-Me: To a stirred solution of
PPhMe2 (0.14 g, 1.0 mmol) in 5 mL of dry dichloromethane kept
in an ice bath was added dropwise a solution of the appropriate
azide 3 (1.0 mmol) in 5 mL of dry dichloromethane. After the ad-
25
[α]D (0.050  in dichloromethane): 1G-Ph: ϩ100; 1G-Me: ϩ100;
2G-Ph: ϩ85; 2G-Me: ϩ110.
[Pd(N,N-chelate)(olefin)]: To a suspension of [Pd(dba)2] (0.58 g,
dition was complete, the ice bath was removed and formation of 1.0 mmol) in 5 mL of dry toluene were added the N,N-chelate
nitrogen was observed. Progression of the reaction was monitored
by TLC analysis on silica of the reacting mixture with ethyl acetate/
petroleum ether, 1:1. The reaction affording the corresponding im-
ino-phosphorane 4 was complete within 3 hours. In the case of 1G-
(1.5 mmol) and the olefin (1.5 mmol). After 1 h of stirring (12 h
when olefin ϭ dmf) the solvent was removed under vacuum from
the resulting mixture. The residue was separated by chromatogra-
phy on silica gel with dichloromethane (to remove dba) and then
Table 5. Elemental analyses for all new compounds
Compound
Formula
C found (calcd.)
H found (calcd.)
N found (calcd.)
1G-Me
C20H26N2O8
56.59 (56.87)
62.21 (61.98)
50.87 (50.91)
57.98 (58.16)
50.85 (50.66)
50.89 (50.56)
51.90 (52.07)
50.62 (50.66)
52.23 (52.07)
46.24 (46.40)
47.63 (47.50)
51.88 (52.05)
50.91 (51.00)
52.28 (52.05)
45.60 (45.48)
6.31 (6.20)
5.89 (5.82)
6.22 (6.10)
5.59 (5.65)
4.87 (4.94)
4.44 (4.39)
4.41 (4.52)
5.05 (4.94)
4.43 (4.52)
5.21 (5.09)
4.60 (4.65)
4.86 (4.78)
4.60 (4.69)
4.66 (4.78)
5.08 (5.01)
6.55 (6.63)
5.93 (5.78)
4.32 (4.24)
3.51 (3.57)
3.93 (3.81)
4.10 (4.07)
8.30 (8.37)
3.65 (3.81)
8.61 (8.37)
4.27 (4.16)
9.04 (9.23)
5.65 (5.78)
2.89 (2.83)
5.86 (5.78)
6.81 (6.63)
1G-Ph
C25H28N2O8
2G-Me
2G-Ph
C28H40N2O16
C38H44N2O16
[Pd(1M-Ph)(dmf)]
[Pd(1M-Ph)(ma)]
[Pd(1M-Ph)(fdn)]
[Pd(1G-Ph)(dmf)]
[Pd(1G-Ph)(fdn)]
[Pd(1G-Me)(dmf)]
[Pd(1G-Me)(fdn)]
[Pd(2M-Ph)(fdn)]
[Pd(2M-Ph)(ma)]
[Pd(2G-Ph)(fdn)]
[Pd(2G-Me)(fdn)]
C31H36N2O12Pd
C29H30N2O11Pd
C29H30N4O8Pd
C31H36N2O12Pd
C29H30N4O8Pd
C26H34N2O12Pd
C24H28N4O8Pd
C42H46N4O16Pd
C42H46N2O19Pd
C42H46N4O16Pd
C32H42N4O16Pd
Eur. J. Inorg. Chem. 1999, 1939Ϫ1947
1945

M. L. Ferrara, F. Giordano, I. Orabona, A. Panunzi, F. Ruffo
with dichloromethane/methanol, 40:1. The solvents were removed squares minimizing the quantity Σw(∆F)2 with wϪ1ϭ [σ2(Fo) ϩ
FULL PAPER
under vacuum from the collected yellow-orange fractions affording
the product as a yellow microcrystalline solid (yield: 75Ϫ85%).
Alternatively, fdn or ma complexes could be prepared by starting
from the corresponding dmf complexes, according to the following
(0.02Fo)2 ϩ 1], where σ is derived from counting statistics. Owing
to the insufficient number of observed reflections of high values of
θ, the final refinement was carried out with anisotropic thermal
parameters for Pd, O and N, and isotropic for C and the non-
example: To a solution of [Pd(1M-Ph)(dmf)] (0.074 g, 0.10 mmol) hydrogen atoms of the solvent molecule MeOH. H atoms at calcu-
in 1 mL of dichloromethane was added fumarodinitrile (0.012 g,
0.15 mmol). The resulting solution was chromatographed as de-
scribed above affording pure [Pd(1M-Ph)(fdn)] (yield 80Ϫ85%).
lated positions were added as riding atoms with isotropic thermal
parameters 1.3 times larger than that of the carrier atoms. The H
atoms of the solvent molecule were neglected. The final Fourier
difference map was within ±0.6 e/A3. All calculations were per-
formed with the EnrafϪNonius (SDP) set of programs.[21] Crystal-
lographic data (excluding structure factors) for the structure re-
ported in this paper have been deposited with the Cambridge Crys-
tallographic Data Centre as supplementary publication no CCDC-
133171. Copies of the data can be obtained free of charge on appli-
cation to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [Fax:
(internat.) ϩ 44-1223/336-033; E-mail: deposit@ccdc.cam.ac.uk].
[Pd(1M*)(fdn)]: To a stirred solution of [Pd(1M-Ph)(fdn)] (0.067 g,
0.10 mmol) in 2.5 mL of dry methanol was added a catalytic
amount of sodium methoxide in the same solvent. After 30 min of
reaction, separation of the yellow product was observed. After a
further 16 h of stirring, the precipitation of the product was en-
hanced by addtion of diethyl ether. The complex was separated,
washed with diethyl ether (3 ϫ 3 mL) and dried under vacuum
(0.040 g, yield: 83%).
Addition of Me3OBF4 to [Pd(1G-Ph)(dmf)] with Formation of 5: A
solution of the complex (0.022 g, 0.030 mmol) in 0.5 mL of deut-
erionitromethane was added to solid Me3OBF4 (0.005 g,
0.033 mmol). The resulting solution was transferred into an NMR
tube and spectra were recorded until no more chemical changes
were detected. Ϫ Selected 1H-NMR resonances (in CD3NO2, at
250 MHz): 5 (diastereomer, 75%): δ ϭ 8.41 (1 H, CHϭN), 4.09 (3
H, OMe), 3.50 (3 H, OMe), 3.40 (3 H, OMe), 2.70 (3 H, Me-py),
1.07 (d, 3 H, CHMe); (diastereomer, 25%): 8.42 (1 H, CHϭN),
4.10 (3 H, OMe), 2.62 (3 H, Me-py), 1.00 (d, 3 H, CHMe).
Acknowledgments
We thank the Consiglio Nazionale delle Ricerche, the MURST and
the Centro Interdipartimentale Ricerhe: Ambiente (CIRAM), Un-
`
iversita di Napoli “Federico II” for financial support, and the Cen-
tro Interdipartimentale di Metodologie Chimico-Fisiche, Univer-
`
sita di Napoli “Federico II” for NMR and X-ray facilities.
[1]
See, for example: S. Otto, G. Boccaletti, J. B. F. N. Engberts, J.
X-ray Crystal-Structure Determination of [Pd(1M*)(fdn)]: Crystals
suitable for X-ray analysis were grown from methanol/diethyl ether.
The crystal, collection, and refinement data are presented in Table
6. Data collection was performed at room temperature with an En-
rafϪNonius MACH3 diffractometer with graphite-monochrom-
ated Mo-Kα radiation using the ω/θ scan technique. The unit-cell
parameters and orientation matrix were obtained from a least-
squares fitting of the setting values of 25 strong reflections in the
range 13° Յ θ Յ 14°. Three monitoring reflections, measured every
500, showed no intensity decrease. Corrections for Lorentz-polariz-
ation effects were applied but not for absorption. The structure was
solved by routinary application of Patterson and Fourier tech-
niques. Refinement on F was carried out by full-matrix least
Am. Chem. Soc. 1998, 120, 4238.
[2]
For examples of organic processes of industrial relevance cata-
[2a]
lyzed by metal/phosphane complexes see:
W. S. Knowles,
Acc. Chem. Res. 1983, 16, 106. Ϫ [2b] S. Akutagawa, Appl. Catal.
[2c]
A 1995, 128, 171. Ϫ
H. Kumobayashi, Recl. Trav. Chim.
Pays-Bas 1996, 115, 201.
[3]
[4]
[3a] A. Togni, L. M. Venanzi, Angew. Chem. Int. Ed. Engl. 1994,
33, 497. Ϫ [3b] H. Brunner, R. Störiko, Eur. J. Inorg. Chem. 1998,
783 and refs. therein.
Other types of ligands based on carbohydrates are known. For
[4a]
recent examples, see:
T. Tanase, Y. Yasuda, T. Onaka, S.
[4b]
Yano, J. Chem. Soc., Dalton Trans. 1998, 345. Ϫ
R. Kady-
rov, D. Heller, R. Selke, Tetrahedron: Asymmetry 1998, 9, 329.
Ϫ [4c] J. Costamagna, N. P. Barroso, B. Matsuhiro, M. Villagran,
`
Inorg. Chim. Acta 1998, 273, 191. Ϫ [4d] M. Stolmar, C. Floriani,
`
G. Gervasio, D. Viterbo, J. Chem. Soc., Dalton Trans. 1997,
[4e]
1119. Ϫ
M. Tschoerner, G. Trabesinger, A. Albinati, P. S.
Pregosin, Organometallics 1997, 16, 347.
Table 6. Crystallographic data for [Pd(1M*)(fdn)] · MeOH
[5]
[6]
M. L. Ferrara, M. Funicello, I. Orabona, A. Panunzi, F. Ruffo,
Organometallics 1998, 17, 3832.
Crystal size [mm]
Empirical formula
Molecular mass
Crystal system
Space group
0.02 ϫ 0.20 ϫ 0.30
[6a] R. A. Klein, P. Witte, R. van Belzen, J. Fraanje, K. Goubitz,
M. Numan, H. Schenk, J. M. Ernsting, C. J. Elsevier, Eur. J.
Inorg. Chem. 1998, 319. Ϫ [6b] B. Milani, A. Anzilutti, L. Vicen-
C18H22N4O5Pd·CH3OH
512.8
orthorhombic
P212121
7.8370 (1)
27.5000 (3)
10.3280 (2)
2225.8
4
tini, A. Sessanta o Santi, E. Zangrando, S. Geremia, G. Mes-
[6c]
troni, Organometallics 1997, 16, 5064. Ϫ
M. Kranenburg, J.
˚
a [A]
G. P. Delis, P. C. J. Kramer, P. W. N. M. van Leewen, K. Vrieze,
˚
b [A]
N. Veldman, A. L. Spek, K. Goubitz, J. Fraanje, J. Chem. Soc.,
[6d]
˚
c [A]
Dalton Trans. 1997, 1839. Ϫ
L. Canovese, F. Visentin, P.
3
˚
V [A ]
Z
Uguagliati, B. Crociani, J. Chem. Soc., Dalton Trans. 1996,
[6e]
1921. Ϫ
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1048
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[7]
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27
`
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R
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2837
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Compounds similar to 4 are known. For a recent example, see:
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2774
` ` ` `
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1946
Eur. J. Inorg. Chem. 1999, 1939Ϫ1947

[Pd(N,N-chelate)(olefin)] Complexes Containing Chiral Nitrogen Chelates
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[21]
Henceforth, a process which is slow (or fast) in the NMR time
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1947