Nickel(II) complexes with Schiff-base ligands derived from epimeric pyranose backbones as 2,3-chelators: modeling the coordination chemistry of chitosan

Article abstract of DOI:10.1016/j.carres.2008.01.039

Two mononuclear nickel(II) complexes with Schiff-base ligands derived from the epimeric sugars glucosamine and mannosamine have been synthesized. The X-ray crystal structure reveals a distorted octahedral geometry at the nickel(II) ions with an N₄

Full text of DOI:10.1016/j.carres.2008.01.039

Available online at www.sciencedirect.com
Carbohydrate Research 343 (2008) 1266–1277
Nickel(II) complexes with Schiff-base ligands derived
from epimeric pyranose backbones as 2,3-chelators:
modeling the coordination chemistry of chitosan
Anja Burkhardt, Helmar G o¨ rls and Winfried Plass*
Lehrstuhl f u¨ r Anorganische Chemie II, Institut f u¨ r Anorganische und Analytische Chemie,
Friedrich-Schiller-Universit a¨ t Jena, Carl-Zeiss-Promenade 10, D-07745 Jena, Germany
Received 7 December 2007; received in revised form 19 January 2008; accepted 28 January 2008
Available online 5 February 2008
Abstract—Two mononuclear nickel(II) complexes with Schiff-base ligands derived from the epimeric sugars glucosamine and
mannosamine have been synthesized. The X-ray crystal structure reveals a distorted octahedral geometry at the nickel(II) ions with
an N
4 2
O donor set and the rare 2,3-chelation of the donor atoms of the carbohydrate backbone. Upon complexation only the
4
O
glucopyranose ring maintains the C
1
5
chair conformation, whereas the mannopyranose ring adopts the S screw-boat conforma-
tion. Dimeric units of complex cations are formed by intermolecular hydrogen bonding which are further assembled by p-stacking
affording one-dimensional chains with a twofold screw symmetry.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Monosaccharides; Schiff bases; Nickel(II) complexes; Coordination chemistry
1
. Introduction
additional donor atoms (see Scheme 1). The Schiff-base
modified derivatives show good catalytic activities con-
cerning cyclopropanation, alkane oxidation, and C–C
Chitosan is the partially deacetylated derivative of
chitin, representing the second-most naturally abundant
polysaccharide after cellulose. The coordination chemis-
try of the b-(1?4)-linked compound is of current inter-
est concerning its application as a supramolecular ligand
for heterogeneous catalysis.
known for its adsorption properties toward metal ions
for several years. Besides its non-toxicity and biocom-
patibility, this biopolymer meets plenty of demands
made on potential heterogeneous catalysts like insolubil-
ity, low chemical reactivity, and a large surface area
because of its swelling properties in protic solvents. In
general, carbohydrates represent enantiomerically pure
compounds isolated from the chiral pool and are there-
fore suitable supports for enantioselective reactions.
Furthermore, chitosan is chemically versatile concerning
its polyfunctionality facilitating the introduction of
9
–12
coupling reactions.
From the coordination chemistry point of view,
carbohydrates are suitable chelate ligands functionalized
1
3
with a set of weakly coordinating donor groups. For
complexes of paramagnetic metal centers X-ray diffrac-
tion methods are the appropriate method of choice to
gain structural information. Unfortunately, carbo-
hydrate–metal complexes show a rather low tendency
to crystallize. In the past two decades intense studies
1
–7
Chitosan has been
8
6
6
HO
HO
HO
5
HO
5
O
O
4
4
3
3
1
O
1
HO
2
2
N
RHN
OBn
R = -Ac, -H
HO
*
Corresponding author. Tel.: +49 3641 948130; fax: +49 3641
48132; e-mail: sekr.plass@uni-jena.de
Scheme 1. 2-Amino-2-deoxy-D-glucose backbone as found in chitosan
(left). Schematic structure of the Schiff-base ligands (right).
9
0
008-6215/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2008.01.039

A. Burkhardt et al. / Carbohydrate Research 343 (2008) 1266–1277
1267
were performed on the functionalization of the sugar
HO
HO
HO
BnOH,
HO
HO
HO
O
O
.
backbone with amides, amines, imines, and carboxylic
groups to accomplish a stronger metal-ion complexa-
BF3 Et O
2
AcHN
AcHN
14–20
tion.
The Schiff-base formation is especially
OH
OBn
explored concerning their common availability via
condensation of amino sugars with aldehyde moie-
ties.
OH
O
KOH,
EtOH
2
1–29
Herein the syntheses and crystal structures of the
mononuclear nickel(II) complexes with Schiff-base
ligands derived from the epimeric sugars glucosamine
HO
HO
HO
HO
HO
HO
O
O
R1
NO2
H
ðH sal GlcÞ and mannosamine (H sal Man) are
2
2
N
H2N
reported. In the course of our investigations on the bind-
HO
OBn
Ac =
OBn
ing properties of chitosan toward transition metal ions,
NO2
the complex ½NiðHsal GlcÞðtptzÞꢀClO
4
was prepared
1
R = -NO , -H
from the Schiff-base ligand derived from 2-amino-2-
deoxy-D-glucose representing the anhydro glucose unit
of this polysaccharide together with 2,4,6-tri-(2-pyrid-
yl)-1,3,5-triazine (tptz) as accompanying co-ligand. The
2
O
Bn =
R1
Me
corresponding 2-amino-2-deoxy-D-mannose-based com-
H
pound [Ni(Hsal Man)(tptz)]ClO was synthesized to
4
Scheme 2. Reaction scheme for the synthesis of the Schiff-base ligands
clarify the influence of the configuration at the chelating
groups on the coordination behavior, in order to allow
for a design of metal-specific coordination pockets on
chitosan derivatives.
NO
H
2
2
2
H sal Glc and H sal Man.
3
doublet with J1,2 = 1.1 Hz consistent with the trans
ee-configuration of the protons H-1 and H-2.
NO2
The mononuclear nickel(II) complexes ½NiðHsal
-
H
2
. Results and discussion
GlcÞðtptzÞꢀClO
4
4
and [Ni(Hsal Man)(tptz)]ClO were
synthesized by addition of an equimolar amount of
nickel(II) perchlorate hexahydrate to a 1:1 mixture of
the appropriate Schiff-base ligand and triethylamine in
methanol. In the presence of 1 equiv of base, the pheno-
lic hydroxy group was deprotonated upon complexa-
tion, and the ligand moiety therefore coordinates as a
monoanionic species. Subsequently a methanolic solu-
tion of 2,4,6-tri-(2-pyridyl)-1,3,5-triazine (tptz) was
added to prevent the coordinative saturation of the me-
tal center via oxo-bridging as it is commonly known
from the formation of relevant polynuclear copper(II)
complexes with related sugar-modified Schiff-base li-
2
.1. Synthesis
The Schiff-base ligands benzyl 2-deoxy-2-(5-nitrosali-
NO2
cylideneamino)-a-D-glucopyranoside ðH sal GlcÞ and
2
benzyl 2-deoxy-2-salicylideneamino-a-D-mannopyran-
H
oside (H sal Man) derived from the epimeric sugars
2
glucosamine and mannosamine, respectively, were
prepared by a three-step synthesis starting from the
corresponding N-acetyl derivatives as represented in
Scheme 2. The protection of the glycosidic hydroxy
groups via a benzyl ether function leads to additional
advantages for the resulting ligands, as this increases
their solubility and facilitates the formation of suitable
crystals. The latter is of particular interest with respect
to potential p-stacking of the resulting complexes in
the crystal packing. The protection of the glycosidic
hydroxy groups was followed by an alkaline hydrolysis
of the amide function at C-2 and subsequently by
condensation of the generated primary amino-function-
alized sugar with the appropriate 2-hydroxy-benzalde-
hyde fragment leading to the corresponding Schiff-base
ligands. The proton H-1 linked to the anomeric carbon
2
7–29
gands.
Moreover, tptz is well known as co-ligand
for octahedral metal centers like nickel(II) and for its
ability to support crystallization by an appropriate crys-
3
0–32
tal packing via p-stacking interactions.
Upon addi-
tion of tptz the color of the reaction mixture turned
from green to brown accompanied by precipitation of
a pale-brown solid which was immediately redissolved
by addition of chloroform and/or acetonitrile. From
these solutions crystals suitable for X-ray diffraction
could be isolated by slow evaporation of the solvent
over a period of several weeks.
NO2
1
atom C-1 of H
NMR spectrum with J = 3.7 Hz. This is indicative
2
sal Glc leads to a doublet in the H
3
2.2. Electronic spectroscopy
1
,2
for the exclusive presence of the a-anomer of the saccha-
ride unit associated with the cis configuration of the
The electronic spectra of the synthesized nickel(II) com-
plexes recorded for solutions in acetonitrile are depicted
in Figure 1. The UV–vis spectrum of the mannosamine
protons attached to C-1 and C-2. On the other hand,
H
the H-1 of the epimeric ligand H sal Man leads to a
2

1268
A. Burkhardt et al. / Carbohydrate Research 343 (2008) 1266–1277
5
4
3
2
1
0000
0000
0000
0000
0000
0
350
2.3. Structure description
3
2
2
1
1
00
50
00
50
00
NO2
3A2g
3T1g(F)
2.3.1. ½ NiðHsal
GlcÞðtptzÞꢀClO . The mononuclear
4
NO2
complex ½NiðHsal GlcÞðtptzÞꢀClO was obtained as
4
3A2g 3T2g
crystals together with co-crystallized acetonitrile and
water solvent molecules, which are located at partially
occupied crystallographic positions (see Section 4).
The complex crystallizes as two crystallographically
independent molecules in the monoclinic space group
5
0
0
5
00 600 700 800 900 10001100
λ / nm
P2 consistent with the exclusive presence of solely one
1
enantiomeric form. In Figure 2 the molecular structure
of one of the two rather similar complex cations
2
50
300
350
400
450
500
550
NO2
þ
½
NiðHsal GlcÞðtptzÞꢀ is depicted. The corresponding
λ / nm
bond lengths and angles are summarized in Table 1.
The nickel(II) ion is embedded in a distorted octa-
hedral coordination environment with an N O donor
NO2
Figure 1. Electronic spectra of ½NiðHsal GlcÞðtptzÞꢀClO
4
(solid line)
H
and [Ni(Hsal Man)(tptz)]ClO
4
(dotted line); the spectra are given for
4
2
solutions in acetonitrile at 20 °C.
set as indicated by the observed cis angles in the range
from 76° to 105° and the trans angles varying from
1
53°NOt2o 175°. The tridentate ligands tptz and
H
ꢁ
containing complex [Ni(Hsal Man)(tptz)]ClO shows a
Hsal Glc are coordinated in a meridional fashion
forming three five- and one six-membered chelate rings
at the metal center with bite angles of 76° to 81° (Nj2–
Nij–Nj5, Nj2–Nij–Nj6, and Oj3–Nij–Nj1; j denotes the
running number of the molecule) and about 92° (Oj6–
Nij–Nj1), respectively. One of the five-membered chelate
rings contains the glucosamine-based Schiff-base ligand
4
weak band at 954 nm and a shoulder at about 530 nm
consistent with the spin-allowed d–d transitions
3
3
3
3
A2g ? T and A ? T (F) typical for a nickel(II)
2g
2g
1g
center placed in an octahedral coordination environ-
ment. Whereas the third d–d transition ( A2g ? T (P))
is expected at higher energy and is masked by intense
3
3
1g
NO2
ꢁ
4
ligand based transitions and charge-transfer bands
Hsal Glc that possesses a C chair conformation
of the glucopyranose ring.
1
3
3–35
appearing below 390 nm.
For the glucosamine-based nickel(II) complex
The coordinative bonds at the nickel(II) ions fall into
two meridional groups which are with values of about
200 and 217 pm found at the lower and upper end of
the respective range. The short distance group consists
of the imino nitrogen atom Nj1 and the phenolic oxygen
atom Oj6 of the Schiff-base ligand and the triazine nitro-
gen atom Nj2 of the tptz co-ligand, whereas the donor
NO2
½
NiðHsal GlcÞðtptzÞꢀClO
4
, the d–d transition bands
are slightly blue-shifted as exemplified by the A
T2g transition occurring at 897 nm. This can be attri-
buted to the presence of the electron-withdrawing nitro
group, which on the other hand also leads to an increase
in intensity for the charge-transfer band at 378 nm.
3
?
2
g
3
NO2
þ
Figure 2. Molecular structure of one of the two independent complex cations ½NiðHsal GlcÞðtptzÞꢀ
in crystals of
NO2
½
NiðHsal GlcÞðtptzÞꢀClO
4
ꢂ0.375CH
3
CNꢂ0.75H
2
O. Thermal ellipsoids are drawn at the 30% probability level. Counterions, solvent molecules
and hydrogen atoms are omitted for clarity.

A. Burkhardt et al. / Carbohydrate Research 343 (2008) 1266–1277
1269
Table 1. Selected bond lengths (pm) and angles (°) for
a hydrogen-bonded dimer as represented in Figure 3.
The observed hydrogen-bonding distances are with
280 pm in the expected range for O–Hꢂ ꢂ ꢂN interac-
NO2
½
NiðHsal GlcÞðtptzÞꢀClO
4
Molecule 1
Molecule 2
3
6,37
Ni1–O13
214.0(6)
198.7(6)
201.3(6)
199.4(6)
212.6(6)
223.5(6)
172.9(2)
81.2(3)
93.9(2)
91.1(2)
91.0(3)
91.8(2)
93.1(2)
91.4(3)
89.8(3)
174.8(3)
101.1(2)
105.6(2)
77.0(2)
76.2(2)
153.3(2)
Ni2–O23
215.8(6)
199.5(6)
198.5(6)
198.5(6)
215.2(6)
217.2(7)
173.6(2)
81.0(3)
92.8(3)
91.7(2)
90.2(3)
92.7(3)
93.5(3)
90.7(2)
90.3(3)
173.8(3)
101.8(2)
104.5(2)
77.4(2)
76.1(2)
153.6(2)
tions.
As a consequence of the hydrogen-bonding
Ni1–O16
Ni1–N11
Ni1–N12
Ni1–N15
Ni2–O26
Ni2–N21
Ni2–N22
Ni2–N25
interaction, the dangling pyridyl ring shows a significant
out-of-plane torsion with respect to the aromatic plane
of the coordinated tptz ligand that results in torsion an-
gles Nj4–Cj27–Cj28–Nj7 of 10.9° and 14.0° (j = 1,2).
Moreover, within the dimeric unit additional p–p inter-
actions at a distance of about 340 pm between the tptz
Ni1–N16
Ni2–N26
O13–Ni1–O16
O13–Ni1–N11
O13–Ni1–N12
O13–Ni1–N15
O13–Ni1–N16
O16–Ni1–N11
O16–Ni1–N12
O16–Ni1–N15
O16–Ni1–N16
N11–Ni1–N12
N11–Ni1–N15
N11–Ni1–N16
N12–Ni1–N15
N12–Ni1–N16
N15–Ni1–N16
O23–Ni2–O26
O23–Ni2–N21
O23–Ni2–N22
O23–Ni2–N25
O23–Ni2–N26
O26–Ni2–N21
O26–Ni2–N22
O26–Ni2–N25
O26–Ni2–N26
N21–Ni2–N22
N21–Ni2–N25
N21–Ni2–N26
N22–Ni2–N25
N22–Ni2–N26
N25–Ni2–N26
NO2
þ
ligands of the two ½NiðHsal GlcÞðtptzÞꢀ cations are
present, enforcing the aggregation of the dimeric units.
3
6–38
This is in the range expected for such interactions.
The angle of 7° between the corresponding mean planes
of the triazine rings is consistent with their near coplan-
arity. Additional hydrogen bonding of the free hydroxy
groups of the carbohydrate backbone is observed with
the perchlorate counterions and the water molecules
present in the crystal structure.
Additional p–p interactions between the tptz co-
ligands of adjacent hydrogen-bonded dimeric units
NO2
þ
f½NiðHsal GlcÞðtptzÞꢀ g lead to a supramolecular
2
assembly as depicted in Figure 4. This p-stacking affords
one-dimensional chains with a twofold screw symmetry
along the crystallographic [010] direction. Whereas
within the dimeric units the whole tptz co-ligand is in-
volved in the p–p interaction, the inter-dimer p-stacking
is essentially established by the central triazine ring
(N22, N23, and N24) of the complex cations containing
Ni2 and the coordinated pyridyl ring (N16) of the Ni1
fragment, at distances ranging between 340 and
atoms with elongated bond lengths are given by the
alcoholic sugar hydroxy group (Oj3) and the pyridyl
nitrogen atoms Nj5 and Nj6.
Intermolecular
hydrogen-bonding
interactions
between the C-3 hydroxy group of the sugar backbone
of the Schiff-base ligand and the nitrogen atom Nj7 of
the dangling pyridyl group of an adjacent complex cat-
ion ½NiðHsal GlcÞðtptzÞꢀþ leads to the formation of
NO2
NO2
þ
Figure 3. Hydrogen-bonded dimer f½NiðHsal GlcÞðtptzÞꢀ g . Perchlorate ions, solvent molecules and hydrogen atoms are omitted for clarity.
2
Pertinent distances: O13ꢂ ꢂ ꢂN27 278.9 and O23ꢂ ꢂ ꢂN17 280.8 pm.

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A. Burkhardt et al. / Carbohydrate Research 343 (2008) 1266–1277
NO2
Figure 4. Supramolecular assembly of the hydrogen-bonded dimers in crystals of complex ½NiðHsal GlcÞðtptzÞꢀClO
4
. Perchlorate ions, solvent
molecules and hydrogen atoms are omitted for clarity. Symmetry operations: A = ꢁx + 2, y + 0.5, ꢁz and B = x, y + 1, z.
3
70 pm with an angle of about 8° between the corre-
sponding mean planes. Additional weaker inter-dimer
p–p interactions are observed between the central tri-
azine ring (N12, N13, and N14) of the complex fragment
Ni1 and the dangling pyridyl ring (N27) of the Ni2 frag-
ment of the adjacent dimeric unit, with relevant dis-
tances ranging from 350 to 390 pm and an angle of
2
4° between the mean planes.
H
.3.2. [Ni(Hsal Man)(tptz)]ClO . Slow evaporation of
2
4
the solvent from the mother liquor afforded crystals of
H
[
Ni(Hsal Man)(tptz)]ClO suitable for X-ray diffrac-
4
tion. These crystals contain additional molecules of
methanol and water located at partially occupied crys-
tallographic positions (see Section 4). The complex crys-
tallizes enantiomerically pure in the orthorhombic space
group P2 2 2 . The molecular structure of one of the
two crystallographically independent complex cations
is represented in Figure 5, and selected bond lengths
and angles for both very similar complex cations are
compared in Table 2.
1
1 1
Figure 5. Molecular structure of one of the two independent complex
H
+
H
cations [Ni(Hsal Man)(tptz)] in crystals of [Ni(Hsal Man)(tptz)]-
ClO O. Thermal ellipsoids are drawn at the 30%
4
ꢂ3.75CH
3
OHꢂ2.375H
2
probability level. Counterions, solvent molecules and hydrogen atoms
are omitted for clarity.
The coordination geometry of the nickel(II) ions
H
in [Ni(Hsal Man)(tptz)]ClO closely resembles that
4
NO2
observed for complex ½NiðHsal GlcÞðtptzÞꢀClO
4
(see
As in the case of the glucosamine-based complex
NO2
Table 1). In particular the distances toward the donor
atoms of the first coordination sphere also fall into
two meridional groups, a short distance group given
by the imino nitrogen atom Nj1 and the phenolic oxygen
atom Oj6 of the Schiff-base ligand and the triazine nitro-
gen atom Nj2 of the tptz co-ligand, as well as the long-
distance group composed of the alcoholic sugar hydroxy
group (Oj3) and the pyridyl nitrogen atoms Nj5 and Nj6
½NiðHsal GlcÞðtptzÞꢀClO
4
, the formation of a hydro-
gen-bonded dimeric structure is observed with
Oj3ꢂ ꢂ ꢂNj7 donor–acceptor distances of about 285 pm
as depicted in Figure 6. The p–p interaction between
the tptz co-ligands of the two adjacent cations within
the dimer is observed at distances of 330–350 pm and
at an angle between the mean planes of the two triazine
rings of 3.5°. In contrast to the glucosamine-based com-
plex system the dangling pyridyl rings are almost copla-
nar with the central triazine rings with torsion angles
Nj4–Cj27–Cj28–Nj7 of 1.9° and 5.5° (j = 1,2). Addi-
tional hydrogen bonding is observed between two meth-
anol molecules and the phenolate oxygen atoms Oj6 of
the dimer (see Fig. 6). For the free hydroxy groups of
the carbohydrate backbone (at C-4 and C-6) of the
(
j denotes the running number of the molecule). In con-
trast to the glucosamine-based complex, for the carbo-
H
+
hydrate backbone of [Ni(Hsal Man)(tptz)] a strong
distortion from the usually observed chair conformation
is observed for the monodeprotonated mannosamine-
derived Schiff-base ligand, leading to a S5 screw-boat
conformation of the sugar backbone.
O

A. Burkhardt et al. / Carbohydrate Research 343 (2008) 1266–1277
1271
Table 2. Selected bond lengths (pm) and angles (°) for
ure 7 this p-stacking leads to one-dimensional chains
with a twofold screw symmetry along the crystallo-
graphic [100] direction. Unlike the p-stacking within
the dimeric units, only part of the tptz co-ligand is
involved in inter-dimer p–p interactions. In contrast to
H
[
Ni(Hsal Man)(tptz)]ClO
4
Molecule 1
Molecule 2
Ni1–O13
214.6(3)
Ni2–O23
216.6(3)
Ni1–O16
198.9(3)
Ni2–O26
198.1(3)
Ni1–N11
197.6(4)
Ni2–N21
198.5(4)
NO2
the glucosamine-based compound ½NiðHsal GlcÞ-
Ni1–N12
198.5(4)
Ni2–N22
200.2(4)
ðtptzÞꢀClO
4
only two of the peripheral pyridyl rings
Ni1–N15
217.4(4)
Ni2–N25
220.2(4)
are involved, leading to pairwise interactions between
the dangling pyridyl rings (Nj7 and Nk7) and one of
the coordinated pyridyl rings (Nj6 and Nk6) of adjacent
dimers at distances of 350–370 and 320–350 pm, respec-
tively, and with deviations from coplanarity of less than
Ni1–N16
216.9(4)
Ni2–N26
219.5(4)
O13–Ni1–O16
O13–Ni1–N11
O13–Ni1–N12
O13–Ni1–N15
O13–Ni1–N16
O16–Ni1–N11
O16–Ni1–N12
O16–Ni1–N15
O16–Ni1–N16
N11–Ni1–N12
N11–Ni1–N15
N11–Ni1–N16
N12–Ni1–N15
N12–Ni1–N16
N15–Ni1–N16
171.42(13)
79.59(15)
90.63(14)
95.51(13)
87.75(13)
92.82(16)
97.18(15)
89.72(15)
90.71(15)
169.55(17)
100.10(15)
107.10(16)
77.01(14)
75.90(14)
152.75(15)
O23–Ni2–O26
O23–Ni2–N21
O23–Ni2–N22
O23–Ni2–N25
O23–Ni2–N26
O26–Ni2–N21
O26–Ni2–N22
O26–Ni2–N25
O26–Ni2–N26
N21–Ni2–N22
N21–Ni2–N25
N21–Ni2–N26
N22–Ni2–N25
N22–Ni2–N26
N25–Ni2–N26
170.37(13)
79.12(13)
91.07(13)
95.73(13)
88.16(13)
91.86(15)
98.00(14)
89.66(15)
90.88(16)
170.12(15)
103.79(15)
104.58(15)
75.88(14)
75.93(14)
151.59(14)
8
°.
2.4. Pyranose ring conformation
In general, carbohydrates exhibiting a trans ee or a cis
configuration of the vicinal donor atoms are ligands
39
suitable for chelation of transition metal ions. Most
of the mononuclear sugar-based nickel(II) complexes
are obtained from either aldohexose moieties with a
1
,2-coordination mode and participation of the glyco-
3
9–42
Schiff-base ligand additional hydrogen bonding is
observed with the perchlorate counterions and disor-
dered water molecules located at partially occupied
crystallographic positions.
sidic group as additional donor function
ketohexoses
or from
4
3,44
exhibiting a 1,2,3-coordination. Conse-
quently, the carbohydrate derivatives of both of these
groups are not suitable ligand systems for chitosan-like
model complexes. In this context, we recently reported
a copper(II) complex as the first example of a transition
metal complex with the 2,3-coordination mode of a
Between the adjacent hydrogen-bonded dimeric units
H
+
{
[Ni(Hsal Man)(tptz)] } additional p–p interactions
2
of the tptz co-ligands are observed. As depicted in Fig-
H
+
Figure 6. Hydrogen-bonded dimer {[Ni(Hsal Man)(tptz)] }
2
and hydrogen-bonded methanol molecules. Perchlorate ions, additional solvent
molecules and hydrogen atoms are omitted for clarity. Pertinent distances: O13ꢂ ꢂ ꢂN27 285.3, O23ꢂ ꢂ ꢂN17 284.2, O16ꢂ ꢂ ꢂO1M 277.3, O26ꢂ ꢂ ꢂO2M
66.8 pm.
2

1272
A. Burkhardt et al. / Carbohydrate Research 343 (2008) 1266–1277
H
Figure 7. Supramolecular assembly of the hydrogen-bonded dimers in crystals of complex [Ni(Hsal Man)(tptz)]ClO
4
. Perchlorate ions, solvent
molecules and hydrogen atoms are omitted for clarity. Symmetry operations: A = x + 0.5, ꢁy + 1.5, ꢁz + 2 and B = x + 1, y, z.
glucosamine required for such chitosan-like model
Cj2–Cj3–Oj3] = 55.1 (j = 1), 51.8° (j = 2)) with d-confor-
NO2
2
8
compounds. Subsequently, recent NMR studies of
platinum(II) group metal complexes with mono- or
disaccharides containing the 2-amino-2-deoxy-D-glucose
unit suggested a trans-2,3-coordination with no evidence
for the participation of the C-6 hydroxy group in the
mation for complex ½NiðHsal GlcÞðtptzÞꢀClO
4
.
Although also uncoordinated 2-amino-2-deoxy-D-
4
mannose prefers a C chair conformation for the pyra-
1
4
7
nose ring, the situation is different for the mannosa-
mine-based complex [Ni(Hsal Man)(tptz)]ClO . In this
H
4
4
5
chelation of the metal ion. We recently communicated
the extension of this concept toward nickel(II) as the
coordinated metal ion for which we reported the first
structurally characterized nickel(II) complex with the
case the required meridional coordination of the
Schiff-base ligand leads to a distortion of the pyranose
O
ring to a S5 screw-boat conformation. Moreover, the
five-membered chelate ring adopts a d-gauche confor-
mation (s[Nj2–Cj2–Cj3–Oj3] = 47.7 (j = 1), 52.1° (j =
3
5
rare trans-2,3-chelation of a glucosamine moiety.
A
similar coordination mode has previously only been
2)), which is similar to what is observed for the glucosa-
4
6
NO2
observed for glucosamine-containing disaccharides.
mine analog ½NiðHsal GlcÞðtptzÞꢀClO
4
. Nevertheless,
The tptz co-ligand utilized for the coordinative satura-
tion of the nickel(II) moieties based on the sugar-derived
this is in contrast to the k-conformation of the chelate
sequence Nj2–Cj2–Cj3–Oj3 as it is observed for the
NO2
H
4
Schiff-base ligands H
2
sal Glc and H sal Man requires
C chair conformation of 2-amino-2-deoxy-D-mannose
2
1
4
7
a meridional coordination at the metal center. As a con-
sequence, also the Schiff-base ligands need to adopt
meridional configuration at the nickel(II) ion. The
resultant different pyranose ring conformations of the
nickel(II) complexes with the Schiff-base ligands of
the epimeric sugars glucosamine and mannosamine are
depicted in Figure 8. For uncoordinated 2-amino-2-
with a relevant torsion angle of ꢁ54.8°. The observed
distortion from the chair conformation for the manno-
H
samine-based complex [Ni(Hsal Man)(tptz)]ClO can
4
be related to a formal flip of the C-2 group interchang-
ing their equatorial and axial positions, which leads to
nearly eclipsed conformations for the neighboring Cj1–
Cj2 and Cj3–Cj4 bonds with torsion angles of about
ꢁ24° and ꢁ14°, respectively. Consequently, it is tempt-
ing to attribute the observed distortion to the steric
requirements of the rigid tptz co-ligand, forcing the
coordinated metal moiety in an equatorial-like position
at the mannosamine backbone.
4
deoxy-D-glucose usually a C1 chair conformation is
1
9,20
observed for the glucopyranose ring.
In case of the
NO2
4
2
glucosamine-based ligand H sal Glc this C1 chair
conformation is retained upon complexation of the nick-
el(II) ions affording a five-membered chelate ring (s[Nj2–

A. Burkhardt et al. / Carbohydrate Research 343 (2008) 1266–1277
1273
OH
HO
HO
HO
O
NsalNO
HO
O
Nsal
OBn
2
OBn
4
HO O
C chair
S screw-boat
1
5
glucopyranose
mannopyranose
Figure 8. Comparison of the pyranose ring conformation of the complex cations ½NiðHsal GlcÞðtptzÞꢀþ and [Ni(Hsal Man)(tptz)] , together with
NO2
H
+
the first coordination sphere of the chelated nickel(II) ions.
H
To the best of our knowledge complex [Ni(Hsal -
bohydrate backbone. The X-ray structures of both com-
plexes reveals a distorted octahedral geometry at the
nickel(II) centers with an N O donor set given by a su-
Man)(tptz)]ClO is the first transition metal complex
4
exhibiting a non-chair conformation of a mannopyran-
ose ring. In transition metal complexes derived from
mannose or the related L-rhamnose, containing more
4
2
gar-modified Schiff-base ligand and a tptz moiety, both
coordinated in a meridional fashion. The complex cat-
ions of both compounds are involved in hydrogen-bond-
ing interactions leading to the formation of dimeric
units. In addition, the tptz co-ligand utilized for coordi-
native saturation of the metal centers gives rise to supra-
4
8–53
flexible co-ligand moieties like (aminoalkyl)amines
instead of the rigid tptz molecule or obtained from less
5
4–57
donor-functionalized sugar moieties,
the pyranose
ring generally adopts the expected chair conformation.
The rare examples of pyranose rings with a screw-boat
conformation have been found for Pt-capped a-cyclo-
molecular aggregation due to its p-stacking ability. In
H
case of Schiff-base ligand H sal Man derived from 2-
2
5
8
dextrins
and ferrocenyl-4,5-(D-glucopyrano)-[2,1-d]-
amino-2-deoxy-D-mannose the meridional coordination
5
9
4
oxazolines. Moreover, the pyranose rings in 1,2-O-eth-
ylidene- or 1,2:3,4-di-O-isopropylidene-a-D-galactopyr-
affords a distortion from the stable C chair conforma-
1
O
tion to the S screw-boat conformation of the pyranose
5
anose derivatives have been generally found to feature
ring. This distortion can be attributed to the steric bulk
of the employed tptz co-ligand and the C-1 benzyl pro-
tecting group.
O
conformations between screw-boat S and twist-boat
5
O
60–66
T , even if not coordinated to any metal ion.
2
The distortion from the chair conformation found for
these compounds is generally attributed for the rigid
acetal or ketal protecting groups.
4. Experimental
3
. Conclusion
4.1. Materials
The starting materials benzyl 2-acetamido-2-deoxy-a-D-
We have synthesized the two nickel(II) complexes
NO2
H
67
½
NiðHsal GlcÞðtptzÞꢀClO
4
and [Ni(Hsal Man)(tptz)]-
glucopyranoside
and benzyl 2-acetamido-2-deoxy-
6
8
ClO with Schiff-base ligands modeling the rare 2,3-che-
D-mannopyranoside
were prepared according to
4
lation of monosaccharides that is assumed to be
characteristic for chitosan. The employed epimeric
monosaccharides 2-amino-2-deoxy-D-glucose and 2-
amino-2-deoxy-D-mannose represent two different basic
conformations of the relevant chelation mode of the car-
published procedures. All other chemicals were pur-
chased from commercial suppliers and used without
further purification. Abbreviations used throughout
NO2
the text: H sal Glc ¼ benzyl 2-deoxy-2-ð5-nitrosali-
2
H
cylideneaminoÞ-a-d-glucopyranoside,
H sal Man =
2

1274
A. Burkhardt et al. / Carbohydrate Research 343 (2008) 1266–1277
benzyl 2-deoxy-2-salicylideneamino-a-D-mannopyrano-
side, tptz = 2,4,6-tri-(2-pyridyl)-1,3,5-triazine.
Caution! Perchlorate salts of metal complexes with
organic ligands are potentially explosive.
4.4. Benzyl 2-deoxy-2-(5-nitrosalicylideneamino)-a-D-
NO2
glucopyranoside ðH sal GlcÞ
2
A solution of p-nitrosalicylaldehyde (464 mg, 2.8 mmol)
in 15 mL of MeOH was added to a solution of H amGlc
2
4
.2. Instrumentation
(748 mg, 2.8 mmol) in 15 mL of MeOH. The reaction
mixture was stirred for 3 h at room temperature. After
complete removal of the solvent, a yellow solid was ob-
tained. The raw product was purified by size-exclusion
chromatography (SEC) with Sephadex LH-20 (MeOH,
Melting points are given uncorrected and were deter-
mined with a B u¨ chi Melting Point B-540 apparatus.
Thermogravimetric analyses (TGA) for powdered sam-
ples were performed on a Netzsch STA409PC Luxx
apparatus under constant flow of nitrogen ranging from
room temperature up to 1000 °C with a heating rate of
flow rate: 10 mL/min). After complete removal of the
NO2
solvent and drying in vacuo, H sal Glc was obtained
2
as a yellow powder. Yield: 940 mg (81%). Selected IR
ꢁ
1
1
°C/min. Infrared spectra were recorded on a Bruker
data (KBr, cm ): ~m ¼ 3412 (mO–H); 3063 and 3032
1
13
IFS 55 Equinox spectrometer. H NMR, C NMR,
(mC–H arom.); 2922 (m CH ); 2880 (m CH ); 1646
as
2
s
2
1
1
1
13
H{ H} COSY, and H{ C} heteronuclear correlation
HMBC and HMQC) NMR experiments were carried
(mCH@N); 1614, 1547, 1519, and 1496 (mC@C, m NO );
as
2
(
1453 (dCH ); 1327 (m NO ); 1135, 1096, 1023, and 943
2 s 2
1
out on a Bruker Avance DRX 400 spectrometer. UV–
vis spectra were recorded with a Varian Cary 5000
UV–vis–NIR-spectrometer. Mass spectra were mea-
sured on a Bruker MAT SSQ 710 spectrometer. Elemen-
tal analyses were determined on a Leco CHNS/932
Analysator and a Vario EL III.
(all mC–O). H NMR (DMSO-d , 400 MHz, 25 °C,
6
ppm): d 3.26–3.29 (m, 1H, H-3), 3.55–3.57 (m, 3H, H-
2, H-4 and H-6a), 3.62–3.65 (m, 1H, H-5), 3.67–3.71
2
(m, 1H, H-6b), 4.53 and 4.75 (2d, each 1H, J
=
a,7b
7
12.1 Hz, H-7a and H-7b), 4.65 (s, 1H, OH-6), 5.09 (d,
3
1H, J = 3.7 Hz, H-1), 5.23 (s, 1H, OH-4), 5.60 (s,
1
,2
1
H, OH-3), 6.68 (d, 1H, J = 9.5 Hz, Ph), 7.26–7.35
d
4
.3. Benzyl 2-deoxy-2-amino-a-D-glucopyranoside
(m, 3H, Ph), 7.41–7.43 (m, 2H, Ph), 8.05 (dd, 1H,
(
H amGlc)
2
J = 2.9 Hz, Ph), 8.48 (d, 1H, J = 2.9 Hz, Ph), 8.72 (s,
d
d
1
3
1
H, H-14), 14.66 (s, 1H, OH-20). C NMR (DMSO-
A solution of benzyl 2-acetamido-2-deoxy-a-D-gluco-
pyranoside (1.00 g, 3.2 mmol) and KOH (7.01 g,
d6, 60 MHz, 25 °C, ppm): d 60.5 (C-6); 66.4 (C-4); 68.2
(C-7); 69.8 (C-3); 71.0 (C-5); 73.5 (C-2); 95.5 (C-1);
113.7, 122.6, 127.6, 128.3, 129.3, 132.3, 134.3, and
137.3 (all Ph); 167.8 (C-14); 177.5 (C-20). ESIMS
1
24.9 mmol) in 25 mL of EtOH (96%) was heated under
reflux overnight. After cooling to room temperature, the
orange mixture was diluted with 50 mL of EtOH and
neutralized with concd HCl. The precipitated KCl was
separated via centrifugation. The volume of the filtrate
was reduced to about 4 mL. The raw product was puri-
fied by size-exclusion chromatography (SEC) with
Sephadex LH-20 (MeOH, flow rate: 15 mL/min). After
complete removal of the solvent and drying in vacuo,
NO2
+
(MeOH): m/z 441 [ðH
2
sal GlcÞ+Na] (100%). Anal.
Calcd for C H N O (418.40): C, 57.41; H, 5.30; N,
2
0
22
2
8
6.70; Found: C, 55.81; H, 5.06; N, 6.48.
4.5. Benzyl 2-deoxy-2-salicylideneamino-a-D-mannopy-
H
ranoside (H sal Man)
2
H amGlc was obtained as a pale-brown oil, still contain-
ing some solvent. Yield: 748 mg (80%). Selected IR data
Benzyl 2-acetamido-2-deoxy-D-mannopyranoside (1.00 g,
3.2 mmol) and KOH (7.01 g, 124.9 mmol) in 25 mL of
EtOH (96%) were heated under reflux overnight. After
cooling to room temperature, the orange mixture was
diluted with 50 mL of EtOH and neutralized with concd
HCl. The precipitated KCl was separated through cen-
trifugation, and the filtrate was reduced to a volume of
2
ꢁ
1
(
(
(
KBr, cm ): ~m ¼ 3378 and 3273 (mO–H, mN–H); 2926
m CH ); 1646 (dN–H); 1559 (mC@C); 1456 and 1413
dCH ); 1128, 1114, 1086, 1051 and 1021 (all mC–O).
as
2
2
1
H NMR (DMSO-d , 400 MHz, 25 °C, ppm): d 2.45
6
3
3
(
dd, 1H, J = 3.7 Hz, J = 9.8 Hz, H-2), 3.08 (dd,
2,1 2,3
3
3
1
H,
J4,3 = J = 9.1 Hz, H-4), 3.26 (dd, 1H,
20 mL. After addition of NaHCO (350 mg, 4.2 mmol)
4,5
3
3
3
J3,2 = J = 9.1 Hz, H-3), 3.42–3.50 (m, 2H, H-5 and
and salicylaldehyde (450 lL, 4.3 mmol), the mixture
was stirred for 2.5 h at room temperature. The solvent
was completely removed under reduced pressure, and
the brownish residue was taken up in a mixture of
3,4
3
2
H-6a), 3.64 (d, 1H, J6b,5 = J
.42 and 4.68 (2d, each 1H, J7a,7b = 12.1 Hz, H-7a
and H-7b), 4.76 (d, 1H, J = 3.7 Hz, H-1), 7.26–7.38
m, 5H, Ph). C NMR (DMSO-d , 100 MHz, 25 °C,
= 10.4 Hz, H-6b),
6b,6a
2
4
3
1
,2
1
3
(
25 mL of CHCl and 15 mL of water. The water layer
6
3
ppm): d 56.2 (C-2); 61.0 (C-6); 67.9 (C-7); 70.4 (C-4);
3.5 (C-5); 74.9 (C-3); 98.2 (C-1); 127.4, 127.6, 128.2,
and 138.0 (all Ph). ESIMS (MeOH): m/z 270
was extracted once with 5 mL of CHCl . The combined
3
7
organic layers were dried over Na SO , filtered, and
2
4
concentrated in vacuo to a volume of 10 mL. The vis-
cous solution was dropped into 300 mL of n-hexane
yielding a yellow precipitate. The product was collected
+
+
[
3
(H amGlc)+H] (26%), 292 [(H amGlc)+Na] (58%),
2 2
+
24 [(H amGlc)+Na+MeOH] (10%).
2

A. Burkhardt et al. / Carbohydrate Research 343 (2008) 1266–1277
1275
by filtration, washed with
a
small amount of
C38.75H35.63ClN8.38NiO12.75 (916.79): C, 50.77; H, 3.92;
N, 12.80; Found: C, 49.32; H, 3.94; N, 12.17.
n-hexane, and finally dried in vacuo affording com-
H
pound H sal Man as a yellow solid. Yield: 683 mg
2
ꢁ
1
H
4.7. [Ni(Hsal Man)(tptz)]ClO
(
57%); mp 75–77 °C. Selected IR data (KBr, cm ):
4
~
m ¼ 3421 (mO–H); 2923 (m CH ); 1633 (mCH@N); 1581
as
2
H
and 1497 (mC@C); 1456 (dCH ); 1130, 1059, 1026, and
To a solution of H sal Man (80 mg, 0.21 mmol) and
2
2
1
9
31 (all mC–O). H NMR (DMSO-d , 400 MHz, 25 °C,
Et N (30 lL, 0.22 mmol) in 3 mL of MeOH was added
6
3
3
3
3
ppm):
d
3.36 (dt, 1H,
J
= 5.9 Hz,
J
J6,5
=
=
under vigorous stirring a solution of Ni(ClO ) ꢂ6H O
4
,OH
4,3
4 2
2
3
3
J4,5 = 9.5 Hz, H-4), 3.50 (q, 1H, J6,OH
=
(79 mg, 0.22 mmol) in 1.5 mL of MeOH. Thereafter a
solution of tptz (67 mg, 0.22 mmol) in 1 mL of MeOH
was added leading to an immediate color change from
pale-green to brown. Within 1 min a pale-brown solid
precipitated that was redissolved immediately by addi-
5
.8 Hz, H-6a), 3.56–3.63 (m, 1H, H-5), 3.63 (dd, 1H,
3
3
J2,1 = 1.1 Hz, J = 4.0 Hz, H-2), 3.74–3.78 (m, 1H,
H-6b), 3.87 (q, 1H, J
and 4.74 (2d, each 1H, J
2,3
3
3
= J = 4.6 Hz, H-3), 4.49
3
,OH
2
3,2
= 11.7 Hz, H-7a and H-
7
a,7b
3
7
b), 4.63 (t, 1H, J
= 5.8 Hz, OH-6), 4.82 (d, 1H,
tion of 1.5 mL of CH CN. Slow evaporation of the sol-
6
,OH
3
3
3
J1,2 = 1.1 Hz, H-1), 4.97 (d, 1H, J
= 5.8 Hz, OH-
vent affords brown prismatic crystals suitable for X-ray
measurements. After filtration the collected crystals
were washed with a small amount of MeOH and
4,OH
3
4
2
1
), 5.06 (d, 1H, J
H, Ph), 7.28–7.38 (m, 6H, Ph), 7.43 (dd, 1H, J =
= 4.8 Hz, OH-3), 6.84–6.90 (m,
,OH
3
d
H
.5 Hz, Ph), 8.48 (s, 1H, H-14), 13.54 (s, 1H, OH-20).
dried in air affording [Ni(Hsal Man)(tptz)]ClO ꢂ
4
1
3
C NMR (DMSO-d , 100 MHz, 25 °C, ppm): d 61.4
1.875CH OHꢂ1.1875H O. The given content of CH CN
6
3
2
3
(
(
C-6); 67.7 and 67.8 (C-4 and C-7); 69.8 (C-3); 71.2
C-2); 74.7 (C-5); 98.6 (C-1); 116.4, 118.4, 118.6, 127.6,
and water molecules of crystallization corresponds to
the values derived from the crystal structure. Yield:
28 mg (15%). Decomposition interval 222–252 °C. Se-
1
2
27.8, 128.3, 131.8, 132.3, and 137.7 (all Ph); 160.8 (C-
ꢁ
1
0); 167.2 (C-14). ESIMS (CHCl /MeOH): m/z 374
lected IR data (KBr, cm ): ~m ¼ 3400 (mO–H); 3066
3
H
+
H
+
[
(H sal Man)+H]
(8%), 396 [(H sal Man)+Na]
2
(mC–H arom.); 2927 (m CH ); 1624 (mCH@N); 1576,
2
as
2
(
100%). Anal. Calcd for C H NO (373.39): C, 64.33;
1560, and 1537 (mC@C); 1467 and 1447 (dCH ); 1152,
2
0
23
6
2
H, 6.21; N, 3.75; Found: C, 63.11; H, 6.16; N, 3.61.
1122, 1109, 1089, 1046, 1027, and 1010 (mC–O,
ꢁ
mClO4 ). UV–vis (CH CN solution, k
in nm (ꢀ in
max
3
NO2
ꢁ1
ꢁ1
4
.6. ½ NiðHsal GlcÞðtptzÞꢀClO
4
L mol cm )): 228 (40,000), 247 (43,000), 289
45,000), 384 (7600), 530 (130), 954 (36). ESIMS
(
H
+
Under vigorous stirring a solution of Ni(ClO ) ꢂ6H O
(CHCl /MeOH): m/z 742 [{Ni(Hsal Man)(tptz)}]
4
2
2
3
(
95 mg, 0.26 mmol) in 1 mL MeOH was added to a
(100%). Anal. Calcd for C39.88H43.88ClN NiO
7
13.06
NO2
solution of H sal Glc (108 mg, 0.26 mmol) and tri-
(924.35): C, 51.82; H, 4.79; N, 10.61; Found: C, 50.47;
H, 4.39; N, 10.96.
2
ethylamine (36 lL, 0.26 mmol) in 3 mL of MeOH. Sub-
sequently, a solution of tptz (81 mg, 0.26 mmol) in 1 mL
MeOH was added, during which a color change from
pale-green to brown was observed. Within 1 min a
pale-brown solid precipitated that was redissolved
immediately by addition of 4 mL CHCl3 and 3 mL
4.8. X-ray structure determinations
NO2
For the compounds ½NiðHsal GlcÞðtptzÞꢀClO
4
and
H
[Ni(Hsal Man)(tptz)]ClO , single crystals were selected
4
CH CN. Slow evaporation of the solvent leads to brown
prismatic crystals suitable for X-ray measurements. The
crystals were collected by filtration, washed with a small
while still covered with mother liquor under a polarizing
microscope and fixed on fine glass fibers. Single-crystal
X-ray measurements were carried out on a Nonius Kap-
pa CCD diffractometer using graphite monochromated
3
amount of MeOH, and dried in air affording
NO2
½
NiðHsal GlcÞðtptzÞꢀClO
4
ꢂ0.375CH CNꢂ0.75H O. The
Mo K radiation (k = 71.073 pm). The crystallographic
3
2
a
given content of CH CN and water molecules of crys-
and structure refinement data for both complexes are
summarized in Table 3. The structures were solved by
direct methods with SHELXS-97 and full-matrix least-
3
tallization corresponds to the values derived from
the crystal structure. Yield: 196 mg (83%). Decomposi-
tion interval 287–300 °C. Selected IR data (KBr,
2
69
squares refined against F using SHELXL-97. Aniso-
tropic thermal parameters were used for all non-hydro-
gen atoms. Hydrogen atoms were calculated and treated
as riding atoms with fixed thermal parameters. For both
compounds additional molecules of crystallization were
found in the crystal structures, some of which are
ꢁ
1
cm ): ~m ¼ 3435 (mO–H); 3064 and 3030 (mC–H arom.);
2
1
924 (m CH ); 2886 (m CH ); 1636 (mCH@N); 1603,
as
2
s
2
576, 1560, 1539, and 1487 (mC@C, m NO ); 1473
as
2
and 1456 (dCH ); 1314 (m NO ); 1145, 1101, 1054,
2
s
2
ꢁ
1
(
030, 1011, 1000, and 949 (mC–O, mClO4 ). UV–vis
CH CN solution, kmax in nm (ꢀ in L mol cm )):
ꢁ
1
ꢁ1
located on partially occupied crystallographic positions.
3
NO2
2
8
½
40 (36,000), 251 (36,000), 290 (41,000), 378 (24,000),
For ½NiðHsal GlcÞðtptzÞꢀClO
4
two positions fraction-
97 (36). ESIMS (CHCl /MeOH): m/z 787
ally occupied with CH CN (0.375 CH CN per Ni) and
3 3
3
fNiðHsal GlcÞðtptzÞgꢀþ (100%). Anal. Calcd for
NO2
five positions fractionally occupied with water

1276
A. Burkhardt et al. / Carbohydrate Research 343 (2008) 1266–1277
Table 3. Summary of the crystal and structure refinement data
NO2
H
½
NiðHsal
GlcÞðtptzÞꢀClO4
[Ni(Hsal Man)(tptz)]ClO
4
Empirical formula
Formula weight [g/mol]
Crystal size [mm]
Crystal system
Space group
a [pm]
C
916.79
38.75
H
35.63ClN8.38NiO12.75
39.88 7
C H43.88ClN NiO13.06
924.35
0.9 ꢃ 0.9 ꢃ 0.9
0.6 ꢃ 0.6 ꢃ 0.5
Monoclinic
Orthorhombic
P2
1
1 1 1
P2 2 2
1569.47(7)
1518.99(8)
1966.79(8)
101.121(3)
4600.8(4)
183(2)
1381.86(2)
2565.16(5)
2646.19(5)
90.00
9379.9(3)
183(2)
b [pm]
c [pm]
b [°]
6
3
V [10 pm ]
T [K]
Z
4
8
3
q [g/cm ]
l(Mo K
1.324
0.547
1.309
0.537
ꢁ1
a
) [mm
]
h Range [°]
Collected data
2.03–27.47
34,002
2.74–27.50
40,550
Unique data (Rint
Observed data [I > 2r(I)]
Parameters
)
18,423 (0.1198)
13,031
1259
20,433 (0.0500)
15,949
1263
Flack parameter
Goodness-of-fit on F
ꢁ0.04(2)
0.003(13)
1.068
2
o
1.049
R
wR
1
[I > 2r(I)]
(all data)
0.0961
0.2739
0.0691
0.1892
2
(
0.75 H O per Ni) were located. In addition also one of
References
2
the perchlorate counterions is found to be disordered.
H
1
2
3
4
. Jin, J.-J.; Chen, G.-C.; Huang, M.-Y.; Jiang, Y.-Y. React.
Polym. 1994, 23, 95–100.
. Quignard, F.; Choplin, A.; Domard, A. Langmuir 2000,
For [Ni(Hsal Man)(tptz)]ClO methanol (1.875 MeOH
4
per Ni) and water molecules (1.1875 H O per Ni) of
2
crystallization were found in the crystal structure. The
hydrogen-bonded MeOH molecules depicted in Figure
1
6, 9106–9108.
. Zhang, J.; Xia, C.-G. J. Mol. Catal. A: Chem. 2003, 206,
59–65.
. Cal o` , V.; Nacci, A.; Monopoli, A.; Fornaro, A.; Sabba-
tini, L.; Cioffi, N.; Ditaranto, N. Organometallics 2004, 23,
6
are located at fully occupied positions, whereas the
remaining MeOH molecules are disordered over four
additional positions. The water molecules are disordered
over nine different crystallographic positions. The crys-
tallographically observed content of solvent molecules
nicely resembles the weight loss determined by TGA
measurements. Moreover, for both complexes an addi-
tional disorder of the phenyl ring of the benzyl protect-
ing group at the Ni1 fragment could be resolved.
5
154–5158.
5
. Adlim, M.; Bakar, M. A.; Liew, K. Y.; Ismail, J. J. Mol.
Catal. A: Chem. 2004, 212, 141–149.
6. Vincent, T.; Guibal, E. Environ. Sci. Technol. 2004, 38,
233–4240.
. Cui, Y.; Zhang, L.; Li, Y. Polym. Adv. Technol. 2005, 16,
33–637.
4
7
6
8
9
. Guibal, E. Sep. Purif. Technol. 2004, 38, 43–74.
. Hardy, J. J. E.; Hubert, S.; Macquarrie, D. J.; Wilson, A.
J. Green Chem. 2004, 6, 53–56.
5
. Supplementary data
1
0. Sun, W.; Xia, C.-G.; Wang, H.-W. New J. Chem. 2002, 26,
55–758.
11. Chang, Y.; Wang, Y.; Su, Z. J. Appl. Polym. Sci. 2002, 83,
188–2194.
2. Tong, J.; Li, Z.; Xia, C. J. Mol. Catal. A: Chem. 2005, 231,
97–203.
3. Gyurcsik, B.; Nagy, L. Coord. Chem. Rev. 2000, 203, 81–
49.
14. Yano, S. Coord. Chem. Rev. 1988, 92, 113–156.
7
CCDC 667961 and 667962 contain the supplementary
crystallographic data for this paper. These data can be
obtained free of charge via http://www.ccdc.cam.
ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or
e-mail: deposit@ccdc.cam.ac.uk.
2
1
1
1
1
1
5. Steinborn, D.; Junicke, H. Chem. Rev. 2000, 100, 4283–
317.
4
1
6. Alexeev, Y. E.; Vasilchenko, I. S.; Kharisov, B. I.; Blanco,
L. M.; Garnovskii, A. D.; Zhdanov, Y. A. J. Coord. Chem.
Acknowledgment
2
004, 57, 1447–1517.
1
1
7. Roth, A.; Koth, D.; Gottschaldt, M.; Plass, W. Cryst.
Growth Des. 2006, 6, 2655–2657.
8. Becher, J.; Seidel, I.; Plass, W.; Klemm, D. Tetrahedron
2006, 62, 5675–5681.
This work was financially supported by the ‘Deutsche
Forschungsgemeinschaft’ (SFB 436 ‘Metal Mediated
Reactions Modeled after Nature’).

A. Burkhardt et al. / Carbohydrate Research 343 (2008) 1266–1277
1277
1
2
2
2
9. Burkhardt, A.; Buchholz, A.; G o¨ rls, H.; Plass, W Acta
44. Yano, S.; Takizawa, S.; Sugita, H.; Takahashi, T.; Shioi,
H.; Tsubomura, T.; Yoshikawa, S. Carbohydr. Res. 1985,
142, 179–193.
45. Johannesen, S. A.; Petersen, B. O.; Duus, J. Ø.; Skrydst-
rup, T. Inorg. Chem. 2007, 46, 4326–4335.
Crystallogr., Sect. E 2007, 63, 2527–2529.
0. Burkhardt, A.; Buchholz, A.; G o¨ rls, H.; Plass, W. Acta
Crystallogr., Sect. E 2007, 63, 2994–2996.
1. Irvine, J. C.; Earl, J. C. J. Chem. Soc. 1922, 121, 2376–
2
381.
46. Herdin, S.; Kettenbach, G.; Kl u¨ fers, P. Z. Naturforsch, B;
Chem. Sci. 2004, 59, 134–139.
2. Fragoso, A.; Kahn, M. L.; Casti n˜ eiras, A.; Sutter, J.-P.;
Kahn, O.; Cao, R. Chem. Commun. (Cambridge) 2000,
47. Neuman, A.; Gillier-Pandraud, H.; Longchambon, F.
Acta Crystallogr., Sect. B 1975, 31, 2628–2631.
48. Yano, S.; Nakagoshi, M.; Teratani, A.; Kato, M.; Onaka,
T.; Iida, M.; Tanase, T.; Yamamoto, Y.; Uekusa, H.;
Ohashi, Y. Inorg. Chem. 1997, 36, 4187–4194.
49. Tanase, T.; Nakagoshi, M.; Teratani, A.; Kato, M.;
Yamamoto, Y.; Yano, S. Inorg. Chem. 1994, 33, 5–6.
50. Tanase, T.; Kurihara, K.; Yano, S.; Kobayashi, K.;
Sakurai, T.; Yoshikawa, S.; Hidai, M. Inorg. Chem.
1987, 26, 3134–3139.
1
547–1548.
2
2
3. Sah, A. K.; Rao, C. P.; Saarenketo, P. K.; Wegelius, E. K.;
Kolehmainen, E.; Rissanen, K. Eur. J. Inorg. Chem. 2001,
2
773–2781.
4. Zhao, J.; Zhou, X.; Santos, A. M.; Herdtweck, E.;
Rom a˜ o, C. C.; K u¨ hn, F. E. Dalton Trans. 2003, 3736–
3
742.
2
2
2
5. Cucciolito, M. E.; Del Litto, R.; Roviello, G.; Ruffo, F. J.
Mol. Catal. A: Chem. 2005, 236, 176–181.
6. Sah, A. K.; Tanase, T.; Mikuriya, M. Inorg. Chem. 2006,
51. Tanase, T.; Kurihara, K.; Yano, S.; Kobayashi, K.;
Sakurai, T.; Yoshikawa, S. J. Chem. Soc., Chem. Commun.
1985, 1562–1563.
4
5, 2083–2092.
7. Roth, A.; Becher, J.; Herrmann, C.; G o¨ rls, H.; Vaughan,
G.; Reiher, M.; Klemm, D.; Plass, W. Inorg. Chem. 2006,
52. Yano, S.; Doi, M.; Tamakoshi, S.; Mori, W.; Mikuriya,
M.; Ichimura, A.; Kinoshita, I.; Yamamoto, Y.; Tanase,
T. Chem. Commun. (Cambridge) 1997, 997–998.
53. Tanase, T.; Tamakoshi, S.; Doi, M.; Mikuriya, M.;
Sakurai, H.; Yano, S. Inorg. Chem. 2000, 39, 692–704.
54. Habermann, N.; Jung, G.; Klaassen, M.; Kl u¨ fers, P.
Chem. Ber. 1992, 125, 809–814.
4
5, 10066–10076.
2
2
3
3
3
8. Burkhardt, A.; Buchholz, A.; G o¨ rls, H.; Plass, W. Eur. J.
Inorg. Chem. 2006, 3400–3406.
9. Burkhardt, A.; Spielberg, E. T.; G o¨ rls, H.; Plass, W. Inorg.
Chem. 2008. doi:10.1021/ic701777t.
0. Ion, A. E.; Spielberg, E. T.; G o¨ rls, H.; Plass, W. Inorg.
Chim. Acta 2007, 360, 3925–3931.
1. Zhou, X.-P.; Li, D.; Wu, T.; Zhang, X. Dalton Trans.
55. Burger, J.; Gack, C.; Kl u¨ fers, P. Angew. Chem. 1995, 107,
2950–2951.
2
006, 2435–2443.
56. Tsubomura, T.; Yano, S.; Kobayashi, K.; Sakurai, T.;
Yoshikawa, S. J. Chem. Soc., Chem. Commun. 1986, 459–
460.
57. Kl u¨ fers, P.; Kunte, T. Z. Anorg. Allg. Chem. 2004, 630,
553–557.
2. Majumder, A.; Gramlich, V.; Rosair, G. M.; Batten, S. R.;
Masuda, J. D.; El Fallah, M. S.; Ribas, J.; Sutter, J.-P.;
Desplanches, C.; Mitra, S. Cryst. Growth Des. 2006, 6,
2
355–2368.
3
3. Lever, A. B. P. Studies in Physical and Theoretical
Chemistry. In Inorganic Electronic Spectroscopy; 2nd ed.
Elsevier: Amsterdam, 1984; Vol. 33.
4. Roth, A.; Buchholz, A.; Rudolph, M.; Sch u¨ tze, E.; Kothe,
E.; Plass, W. Chem. Eur. J. 2008, 14, 1571–1583.
58. Armspach, D.; Matt, D. Inorg. Chem. 2001, 40, 3505–
3509.
59. Hartinger, C. G.; Nazarov, A. A.; Galanski, M.; Reitho-
fer, M.; Keppler, B. K. J. Organomet. Chem. 2005, 690,
3301–3308.
60. Bellot, F.; Hardr e´ , R.; Pelosi, G.; Th e´ risod, M.; Policar, C.
Chem. Commun. (Cambridge) 2005, 5414–5416.
61. Cone, C.; Hough, L. Carbohydr. Res. 1965, 1, 1–9.
62. K o¨ ll, P.; Saak, W.; Pohl, S.; Steiner, B.; Ko o´ sˇ , M.
Carbohydr. Res. 1994, 265, 237–248.
3
3
3
3
5. Burkhardt, A.; Plass, W. Inorg. Chem. Commun. 2008, 11,
3
03–306.
6. Plaul, D.; Buchholz, A.; G o¨ rls, H.; Plass, W. Polyhedron
007, 26, 4581–4590.
2
7. Roth, A.; Buchholz, A.; G a¨ rtner, M.; Malassa, A.; G o¨ rls,
H.; Vaughan, G.; Plass, W. Z. Anorg. Allg. Chem. 2007,
63. Zhou, Y.; Wagner, B.; Polborn, K.; S u¨ nkel, K.; Beck, W.
Z. Naturforsch., B: Chem. Sci. 1994, 49, 1193–1202.
64. Cox, P. J.; Melvin, O. A.; Garden, S. J.; Wardell, J. L. J.
Chem. Crystallogr. 1995, 25, 469–475.
65. Cox, P. J.; Garden, S. J.; Howie, R. A.; Melvin, O. A.;
Wardell, J. L. J. Organomet. Chem. 1996, 516, 213–
224.
66. Weyershausen, B.; Nieger, M.; D o¨ tz, K. H. J. Org. Chem.
1999, 64, 4206–4210.
67. Gy o¨ rgyde a´ k, Z. Liebigs Ann. Chem. 1991, 1291–1300.
68. Yoshimura, J.; Sakai, H.; Oda, N.; Hashimoto, H. Bull.
Chem. Soc. Jpn. 1972, 45, 2027–2032.
6
33, 2009–2018.
3
3
8. Janiak, C. J. Chem. Soc., Dalton Trans. 2000, 3885–3896.
9. Yano, S.; Kato, M.; Shioi, H.; Takahashi, T.; Tsubomura,
T.; Toriumi, K.; Ito, T.; Hidai, M.; Yoshikawa, S. J.
Chem. Soc., Dalton Trans. 1993, 1699–1706.
0. Yano, S.; Sakai, Y.; Toriumi, K.; Ito, T.; Ito, H.;
Yoshikawa, S. Inorg. Chem. 1985, 24, 498–504.
4
4
1. Yano, S.; Takahashi, T.; Sato, Y.; Ishida, K.; Tanase, T.;
Hidai, M.; Kobayashi, K.; Sakurai, T. Chem. Lett. 1987,
1
6, 2153–2156.
4
4
2. Shioi, H.; Yano, S.; Toriumi, K.; Ito, T.; Yoshikawa, S. J.
Chem. Soc., Chem. Commun. 1983, 201–202.
69. Sheldrick, G. M. SHELXS and SHELXL; University of
3. Tsubomura, T.; Yano, S.; Toriumi, K.; Ito, T.; Yoshi-
kawa, S. Inorg. Chem. 1985, 24, 3218–3223.
¨ ¨
Gottingen: Gottingen, Germany, 1997.