Synthesis, reactivity, and structural characterization of dioxovanadium(V) complexes with tridentate schiff base ligand: Vanadium complexes in supramolecular networks

Article abstract of DOI:10.1002/zaac.200390018

The synthesis, characterization and crystal structure analysis of the ammonium salt of the dioxovanadium(V) complex NH₄[VO₂(salhyph)] with the tridentate Schiff base ligand derived from salicylaldehyde and benzoic acid hydrazide (H₂salhyph) is reported. NH₄[VO₂(salhyph)] crystallizes in the monoclinic space group Pn with a = 708.8(2), b = 1444.3(3), c = 717.1(2) pm and β = 101.09(2)°. The vanadium atom of the dioxovanadium(V) moiety has a distorted square-pyramidal coordination geometry. Extensive hydrogen bonding is observed between the ammonium cation and the oxygen atoms coordinated to the vanadium atom yielding to a two-dimensional network, where the complex anions are arranged in a bilayer. Additional crystal packing within the bilayer appears to be controlled mostly by π stacking between the aromatic rings of the ligand. The reactions of NH₄[VO₂(salhyph)] with several proton acidic compounds including water, methanol, and proton acids lead to neutral monooxovanadium(V) and dioxovanadium(V) complexes ([VO₂(Hsalhyph)], [V₂O₃(salhyph)₂] and [VO(OMe)(salhyph)(HOMe)]).

Full text of DOI:10.1002/zaac.200390018

Synthesis, Reactivity, and Structural Characterization of Dioxovanadium(V)
Complexes with Tridentate Schiff Base Ligand:
Vanadium Complexes in Supramolecular Networks
Winfried Plass* and Hakan-Peter Yozgatli
Siegen, Anorganische Chemie der Universität
Received August 5th, 2002.
Abstract. The synthesis, characterization and crystal structure
analysis of the ammonium salt of the dioxovanadium(V) complex
NH4[VO2(salhyph)] with the tridentate Schiff base ligand derived
from salicylaldehyde and benzoic acid hydrazide (H2salhyph) is re-
ported. NH4[VO2(salhyph)] crystallizes in the monoclinic space
group Pn with a ϭ 708.8(2), b ϭ 1444.3(3), c ϭ 717.1(2) pm and
β ϭ 101.09(2)°. The vanadium atom of the dioxovanadium(V)
moiety has a distorted square-pyramidal coordination geometry.
Extensive hydrogen bonding is observed between the ammonium
cation and the oxygen atoms coordinated to the vanadium atom
yielding to a two-dimensional network, where the complex anions
are arranged in a bilayer. Additional crystal packing within the
bilayer appears to be controlled mostly by π stacking between the
aromatic rings of the ligand. The reactions of NH4[VO2(salhyph)]
with several proton acidic compounds including water, methanol,
and proton acids lead to neutral monooxovanadium(V) and di-
oxovanadium(V) complexes ([VO2(Hsalhyph)], [V2O3(salhyph)2]
and [VO(OMe)(salhyph)(HOMe)]).
Keywords: Vanadium; Hydrogen bonding; Salicylidenehydrazides;
Schiff base; Crystal structure
Synthese, Reaktionen und Struktur von Dioxovanadium(V)-Komplexen mit
dreizähniger Schiffscher Base als Ligand:
Vanadiumkomplexe in supramolekularen Netzwerken
Inhaltsübersicht. Für das Ammoniumsalz des Dioxovanadium(V)-
Komplexes NH4[VO2(salhyph)] mit dem aus Salicylaldehyd und
Benzolcarbonsäurehydrazid erhaltenen dreizähnigen Liganden
vom Typ der Schiffschen Basen (H2salhyph) wird die Synthese,
Charakterisierung und Kristallstrukturanalyse beschrieben.
NH4[VO2(salhyph)] kristallisiert in der monoklinen Raumgruppe
Pn mit a ϭ 708.8(2), b ϭ 1444.3(3), c ϭ 717.1(2) pm und β ϭ
101.09(2)°. Das Vanadiumatom der Dioxovanadium(V)-Einheit be-
sitzt eine verzerrte quadratisch planare Koordinationsumgebung.
Zwischen dem Ammoniumkation und den an das Vanadiumatom
gebundenen Sauerstoffatomen besteht ein ausgedehntes zweidi-
mensionales Netzwerk von Wasserstoffbrückenbindungen, welches
in eine durch die komplexen Anionen gebildete Doppelschicht ein-
gebettet ist. Die weitere Kristallpackung innerhalb der Doppel-
schichten scheint hauptsächlich durch π-Stapelung zwischen den
aromatischen Ringen des Liganden kontrolliert zu werden. Die Re-
aktionen von NH4[VO2(salhyph)] mit verschiedenen H-aziden Ver-
bindungen, wie Wasser, Methanol und Protonensäuren, führt zu
neutralen Monooxovanadium(V)- und Dioxovanadium(V)-Kom-
plexen ([VO2(Hsalhyph)], [V2O3(salhyph)2] und [VO(OMe)(sal-
hyph)(HOMe)]).
Introduction
phate [3]. In this context striking similarities are observed
for the active site architecture of vanadium haloperoxidases
(e.g. Curvularia inaequalis [4]) and certain bacterial acid
phosphatases (e.g. Escherichia blattae [5]). A basic feature
of this active site architecture for both enzymatic systems is
the extensive hydrogen bonding of the protein environment
with either the prosthetic group vanadate or the substrate
analog molybdate. The importance of hydrogen bonding in
biological systems has been documented to go beyond its
well established structural relevance [6Ϫ8].
The interest in coordination chemistry of pentavalent va-
nadium from a biological and pharmacological perspective
is due to the discovery of the insulin-like effect of vanadium
compounds and the presence of vanadium in certain halop-
eroxidases [1, 2]. A key point for the understanding of how
vanadium actually functions in biological systems is given
by the chemical similarities between vanadate and phos-
Although various crystal structures of different va-
nadium haloperoxidases have been reported [4, 9Ϫ13], the
protonation and the actual structure of the vanadate moiety
are still unknown. Mechanisms to account for the halop-
eroxidase activity of the enzymes as well as a series of mo-
del compounds have been proposed, which all include pro-
* Prof. Dr. Winfried Plass
Anorganische Chemie
Universität Siegen
D-57068 Siegen (Germany)
Fax: ϩ49 (0)271/740-2555
E-mail: plass@chemie.uni-siegen.de
Z. Anorg. Allg. Chem. 2003, 629, 65Ϫ70  2003 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 0044Ϫ2313/03/629/65Ϫ70 $ 20.00ϩ.50/0
65

W. Plass, H.-P. Yozgatli
Fig. 1 Synthesis and reactions of NH4[VO2(salhyph)]: i) DMF,
∆T; ii) MeOH, ∆T; iii) (t-BuO)2PO(OH), THF; iv) H2O, ∆T; v)
liquid NH3.
um(V) complex NH4[VO2(salhyph)] can be isolated, if the
synthesis is performed in aprotic solvents like DMF or
DMSO. By reacting solutions of NH4[VO2(salhyph)] with
methanol the complex can be converted to the oxovanadi-
um(V) species [VO(OMe)(salhyph)(HOMe)], which has
been described before as an oxidative byproduct in a reac-
tion starting form a vanadium(IV) precursor [20]. With al-
cohols as reaction media for the complex formation starting
from ammonium metavanadate the corresponding oxovan-
adium(V) complexes are directly accessible (see Fig. 1). This
also allows for the synthesis of derivatives with chelating
mono deprotonated diols like ethan-1,2-diol (H2ed), yield-
ing [VO(Hed)(salhyph)] (cf. Ref. [18]). Both oxovanadi-
um(V) complexes, [VO(OMe)(salhyph)(HOMe)] and
[VO(Hed)(salhyph)], are dark red-brown crystalline com-
pounds that are soluble in polar organic solvents like
DMSO or alcohols.
Treatment of the ammonium salt NH4[VO2(salhyph)]
with an excess of water leads to the formation of the neutral
complex [VO2(Hsalhyph)] under release of ammonia.
[VO2(Hsalhyph)] is obtained as yellow solid which is only
poorly soluble in organic solvents and is insoluble in water.
The reconversion to the ammonium salt can be achieved by
deprotonation of the neutral complex in liquid ammonia.
On the other hand the protonation in absence of water
yields the formal anhydrid [V2O3(salhyph)2] as dark brown
crystals. By the same synthetic strategy the anhydrid [V2O3-
(salhyph)2] is also accessible starting from the oxovanadi-
um(V) complex [VO(OMe)(salhyph)(HOMe)] (see Fig. 1).
This anhydride has also been prepared using different syn-
thetic approaches starting from vanadium(IV) precursors
[21, 22]. The neutral complex [VO2(Hsalhyph)], which can
be regarded as the tautomer of the corresponding acid, is
consequently accessible by hydrolysis of the anhydrid
[V2O3(salhyph)2] (see Fig. 1). At this point it has to be
noted that in contrast to the N-salicylidenehydrazide ligand
system described here, a so-called free acid with an oxo-
hydroxo core, viz [VO(OH)]2ϩ, has been reported for a
bis(8-quinolinato)vanadium(V) complex [23].
Scheme 1
ton transfer steps at the vanadate moiety [1,14Ϫ16]. More-
over, all model systems known today are either based on
cis-dioxovanadium(V) complexes or postulate such a spec-
ies as intermediate [1, 16]. As structural models for possible
intermediates of the catalytic cycle for haloperoxidase ac-
tivity various oxovanadium(V) and cis-dioxovanadium(V)
complexes have been reported [17]. Nevertheless, the knowl-
edge about ligand systems capable of supporting both coor-
dination modes is rather scares. Of particular interest in this
context are ligand systems flexible enough to accommodate
both an oxovanadium(V) and a cis-dioxovanadium(V) unit.
In addition, such a ligand system should also support a
variable protonation of the obtained complexes. As we have
shown previously, N-salicylidenehydrazides are versatile li-
gand systems that actually feature these desired character-
istics [18]. Herein we report on the synthesis, structure and
reactivity of the ammonium salt of a cis-dioxovanadium(V)
complex of such a Schiff base type ligand system.
Results and Discussion
Synthesis and Reactions
N-Salicylidenehydrazides are tridentate chelate ligands de-
rived from salicylaldehyd and carbonic acid hydrazides. In
Scheme 1 the synthesis of H2salhyph via the Schiff base
condensation reaction utilizing benzoic acid hydrazide is
depicted. Both tautomers of the ligand system H2salhyph
(see Scheme 1) are capable of coordinating metal ions [19]
yielding complexes with either the mono- or dianionic form
of the ligand.
Starting from ammonium metavanadate as vanadium
source the ammonium salt of the anionic cis-dioxovanadi-
66
Z. Anorg. Allg. Chem. 2003, 629, 65Ϫ70

Vanadium Complexes in Supramolecular Networks
The neutral cis-dioxovanadium(V) complex [VO2(Hsal-
hyph)] can be utilized as a general source to synthesize a
series of different oxovanadium(V) complexes containing
the salhyph2Ϫ ligand. Examples are the oxovanadium(V)
complexes [VO(OMe)(salhyph)(HOMe)] and [VO(Hed)-
(salhyph)] which are obtained by reaction with the appro-
priate alcohol in nearly quantitative yields (cf. Fig. 1 and
Ref. [18]). By hydrolysis with an excess of water both oxo-
vanadium(V) complexes can be reconverted to the neutral
cis-dioxovanadium(V) complex [VO2(Hsalhyph)].
The results described above clearly show that N-salicylid-
enehydrazides are tridentate ligands for vanadium(V) com-
plexes that can form both oxo and dioxo species and, more-
over, also allow for the variation of the protonation state of
the resulting complexes. Consequently for the ammonium
salt NH4[VO2(salhyph)] a varying solution speciation is ob-
served that is strongly dependent on the solvent and reac-
tants present. In contrast additional speciation for the cor-
responding potassium salt K[VO2(salhyph)] is solely ob-
served in the presence of stoichiometric amounts of appro-
priate acids [18].
Fig. 2 Molecular structure of the anionic dioxovanadium complex
[VO2(salhyph)]Ϫ in crystals of NH4[VO2(salhyph)] (thermal ellip-
soids are drawn at the 50 % probability level).
Spectroscopic Characterization
The 1H and 13C NMR data for the ammonium salt
NH4[VO2(salhyph)] summarized in the experimental section
is consistent with the formation of a dioxovanadium(V)
complex. In particular the deprotonation of both acidic
groups of the free ligand H2salhyph (cf. Scheme 1) upon
formation of NH4[VO2(salhyph)] is confirmed by the ab-
Table 1 Selected bond lengths (in pm) and angles (in °) for
NH4[VO2(salhyph)].
VϪO1
VϪO2
VϪO3
VϪO4
VϪN1
162.1(4)
162.7(4)
190.4(4)
196.2(4)
212.0(4)
O4ϪC8
N1ϪN2
N1ϪC7
N2ϪC8
130.9(7)
139.5(6)
128.4(7)
129.7(8)
1
sence of the most downfield H NMR resonances corre-
O1ϪVϪO2
O1ϪVϪO3
O1ϪVϪO4
O2ϪVϪO3
O2ϪVϪO4
109.9(2)
103.0(2)
102.9(2)
94.5(2)
O3ϪVϪO4
O1ϪVϪN1
O2ϪVϪN1
O4ϪVϪN1
O3ϪVϪN1
149.2(2)
109.0(2)
140.7(2)
74.1(2)
sponding to the OϪH and NϪH protons of the phenolate
and the amide groups, respectively. The 51V NMR data for
the ammonium salt of the anionic dioxovanadium(V) com-
plex [VO2(salhyph)]Ϫ is somewhat dependent on the sol-
vent, i.e. for DMSO solutions a down-field shift of 7 ppm
is observed, as compared to a DMF solution (δ ϭ Ϫ540).
On the other hand the 51V NMR resonance of the anionic
dioxovanadium(V) complex [VO2(salhyph)]Ϫ is independent
of the counter ion present, as the same chemical shifts are
observed for the corresponding potassium salt. Unfortu-
nately, for the neutral complex [VO2(Hsalhyph)] no useful
NMR data could be obtained, due to its very poor solu-
bility.
Infrared spectra of the ammonium salt NH4[VO2-
(salhyph)] confirm the deprotonation of the amid func-
tionality in the complex. The free ligand NϪH and CϭO
stretches at 3330 and 1640 cmϪ1, respectively, are not ob-
served in the complex. Instead a strong band is observed at
1610 cmϪ1 which can be attributed to the stretching vi-
bration of the conjugate ϪCϭNϪNϭCϪ grouping [19].
This band is characteristic for the coordination of the enol-
ate form of the N-salicylidenehydrazide ligand to the di-
oxovanadium(V) moiety. For NH4[VO2(salhyph)] two
strong bands are observed at 895 and 918 cmϪ1 assigned to
stretching vibrations of the cis-VO2 moiety of the complex.
Whereas for the protonated neutral complex [VO2-
91.9(2)
82.1(2)
(Hsalhyph)] a broad strong band at 884 cmϪ1 is attributed
to the corresponding stretching vibrations. For the neutral
complex [VO2(Hsalhyph)] an additional band for the NϪH
stretching vibration of the protonated amide functionality
is observed at 2600 cmϪ1. The site of protonation within
the complex is also verified by the synthesis of the corre-
sponding deuterium derivative that shows the expected fre-
quency shift for the relevant band assigned to the NϪD
stretching vibration which appear at 1980 cmϪ1 [24].
Molecular Structure of NH4[VO2(salhyph)]
The molecular structure of the complex anion of the am-
monium salt NH4[VO2(salhyph)] with the atom numbering
scheme is shown in Figure 2 and selected bond lengths and
angles are listed in Table 1. The NO4 coordination sphere
around the vanadium atom is defined by the two cisoid oxo
groups (O1 and O2) as well as the phenolate oxygen atom
(O3), the amide oxygen atom (O4) and the imine nitrogen
Z. Anorg. Allg. Chem. 2003, 629, 65Ϫ70
67

W. Plass, H.-P. Yozgatli
atom of the dibasic tridentate ligand H2salhyph. The bond
lengths N1ϪN2, N1ϪC7, N2ϪC8 and O4ϪC8 of the co-
ordinated ligand system are consistent with the enolate
form of the amide functionality and, moreover, are in good
agreement with the data found for the corresponding pot-
assium salt [18]. The most significant parameter for differ-
entiating between the enolate and the keto form of the am-
ide functionality is the O4ϪC8 bond lengths. For the enol-
ate form of the ammonium and potassium salt a value of
131 and 132 pm, respectively, is found, whereas for the keto
form of the neutral complex [VO2(Hsalhyph)] a O4ϪC8
bond lengths of 127 pm is observed [18]. The ligand forms
a five- and a six-membered chelate ring with bite angles of
74° (O4ϪVϪN1) and 82° (O3ϪVϪN1), respectively. For
the vanadium atom a distorted square pyramidal coordi-
nation is found with one of the doubly bonded oxo groups
(O2), the phenolate (O3) and enolate oxygen atoms (O4) as
well as the imine nitrogen atom (N1) forming the tetragonal
plane. This tetragonal plane is only twisted by an angle of
7° against the mean plane defined by the tridentate ligand
system. With respect to the apical oxo group O1 the va-
nadium atom lies 39 pm above and the oxo group O2 40 pm
below this mean plane of the ligand system. The fact that
only slight distortions towards a trigonal bipyramid are pre-
sent is quantified by a τ parameter of 0.14 (τ ϭ 0 for an
ideal tetragonal pyramid; τ ϭ 1 for an ideal trigonal bipyra-
mid). Nevertheless the observed deviation from the ideal
square-pyramidal geometry is somewhat larger than that
observed for the corresponding potassium salt with a τ par-
ameter of 0.02 [18]. This can be attribute to differences in
the crystal packing between the ammonium and the potas-
sium salt (vide infra).
Fig. 3 Representation of the hydrogen bonding interactions of the
anionic dioxovanadium complex [VO2(salhyph)]Ϫ with the ammo-
nium cations in crystals of NH4[VO2(salhyph)] (broken lines repre-
sent hydrogen bonds); relevant distances (in pm): O1···N3 296,
O1···N3C 321, O2···N3A 281, O2···N3B 279, O3···N3C 318,
O4···N3A 306) (symmetry transformations: (A) x Ϫ 0.5, 2 Ϫ y, 0.5
ϩ z; (B) x, y, 1 ϩ z; (C) 0.5 ϩ x, 2 Ϫ y, 0.5 ϩ z).
Hydrogen Bonding Network of NH4[VO2(salhyph)]
All four oxygen atoms coordinated to the vanadium atom
are involved in hydrogen bonding with the ammonium cat-
ion as depicted in Figure 3. The shortest hydrogen bonding
contacts of the ammonium nitrogen atom are observed
towards the oxo group O2 with 279 and 281 pm, whereas
the largest distances are found for interactions with the phe-
nolate oxygen atom (O3···N3C 318 pm) and the apical oxo
group (O1···N3C 321 pm).
The extensive hydrogen bonding observed leads to the
formation of a two-dimensional network oriented along the
crystallographic (010) plane which is depicted in Figure 4.
The orientation of the oxygen atoms involved in hydrogen
bonding towards the layer established by the ammonium
cations results in the formation of a bilayer with the hydro-
phobic part of the complex anions located on the outside.
Within the hydrophobic part of the bilayer the crystal pack-
ing appears to be controlled mostly by π stacking between
the aromatic rings of the ligand. This arrangement leads to
the observed distortion of the square-pyramidal coordi-
nation around the vanadium atom towards a trigonal
bipyramid in order to allow for a better hydrogen bonding
interaction with in the established bilayer. As compared to
Fig. 4 Representation of the two-dimensional hydrogen bonding
network in crystals of NH4[VO2(salhyph)] (view along the negative
[001] direction; hydrogen atoms at the anionic dioxovanadium com-
plex are omitted; broken lines represent hydrogen bonding interac-
tions).
the ideal square-pyramidal coordination found for the
corresponding potassium salt, this reflects in the decrease
of the O2ϪVϪN1 angle from 148° in the potassium salt
[18] to 141° in the ammonium salt described here.
Conclusions
The synthesis and reactivity of dioxovanadium(V) com-
plexes with N-salicylidenehydrazides presented shows that
68
Z. Anorg. Allg. Chem. 2003, 629, 65Ϫ70

Vanadium Complexes in Supramolecular Networks
Table 2 Crystal and diffraction data for NH4[VO2(salhyph)]
these are versatile tridentate ligands for vanadium(V) com-
plexes. These ligand systems can stabilize both oxo and di-
oxo spezies and, moreover, they also allow for a varying
protonation state of the resulting complexes. These com-
plexes can be regarded as structural models for the active
site in vanadium dependent haloperoxidases. For the am-
monium salt NH4[VO2(salhyph)] an extensive hydrogen
bonding network is observed which leads to the formation
of a bilayered arrangement of the complex anions around
the ammonium counterions. The protonation of the anionic
complex leads to the formation of the neutral compound
[VO2(Hsalhyph)] which contains the amide form of the li-
gand. This indicates that for the N-salicylidenehydrazide li-
gand investigated here the amide nitrogen atom is the more
basic site compared to the oxo groups at the vanadium
atom. As the N-salicylidenehydrazide ligand system can
easily be modified, we are currently investigating the effect
of additional functional groups in the vicinity of a vana-
date moiety.
formula
formula weight
C14H14N3O4V
339.22
crystal size
crystal system
space group
0.50 ϫ 0.20 ϫ 0.05 mm
monoclinic
Pn
a
b
c
β
V
Z
708.8(2) pm
1444.3(3) pm
717.1(2) pm
101.09(2)°
0.7204(2) nm3
2
T
ρcalc
293 K
1.564 g cmϪ3
1594
reflection collected
independent reflections
observed reflections
restraints/parameters
R1 (I > 2σ(I))
wR2 (all refl.)
1540
1285
12/253
0.039
0.091
solution to about 75 ml and cooling to room temperature brown
crystals begin to form. A second batch of crystalline material can
be obtained after further reduction of the volume of the mother
liquor. Total yield: 6.78 g (74 %). C16H17N3O5V (368.26): calcd. C
52.18, H 4.65, N 7.61; found C 52.20, H 4.85, N 7.60 %.
1H NMR (CDCl3): δ ϭ 3.44 (s, 3H, CH3OH), 5.25 (s, 3H, VOCH3),
7.07Ϫ7.16 (m, 2H, ph), 7.42Ϫ7.61 (m, 5H, ph), 8.11Ϫ8.19 (m, 2H, ph), 8.95
(s, 1H, HCϭN). Ϫ 13C NMR (CDCl3): δ ϭ 50.8 (CH3OH), 72.3 (VOCH3),
117.7, 120.2, 121.7, 128.5, 128.7, 130.0, 131.9, 132.3, 135.0, 154.7 (CϭN),
164.5, 173.3 ppm. Ϫ 51V NMR (CDCl3): δ ϭ Ϫ547 ppm. Ϫ Selected IR data
(cmϪ1): ν˜ ϭ 1608 (s, br: CϭNϪNϭC), 969 (s, VϭO). Ϫ UV/Vis (solid state
reflection, νmax in 103 cmϪ1): 24.3, 18.5 (sh). Ϫ UV/Vis (CHCl3 solution,
νmax in 103 cmϪ1 (ε in 106 cm2 molϪ1)): 31.6 (27), 26.2 (13), 19.0 sh (1).
Experimental Section
Materials: The Schiff base precursor salicylaldehyd-benzoyl-hydra-
zone (H2salhyph) was derived form salicylaldehyd and benzole acid
hydrazide. All other chemicals were of reaction grade.
Physical Measurements: Elemental analyses (C, H, N) were carried
out on a Leco CHNS-932 elemental analyzer. Ϫ FT-IR spectra for
KBr pellets and Nujol mulls between CsI plates were measured on
a Bruker IFS66 spectrometer. Ϫ Raman spectra were measured on
a Bruker IFS66/FRA106 spectrometer (λe ϭ 1064 nm). Ϫ Elec-
tronic spectra were recorded on Shimadzu UV-160A (solution
transmission) and Beckman Acta MIV (solid state reflection) spec-
Synthesis of [V2O3(salhyph)2]: To a solution of NH4[VO2(salhyph)]
(1.60 g, 4.7 mmol) in 100 ml THF phosphoric acid dibutylester
(1.95 g, 5.0 mmol) was added. The resulting brown solution was
stirred at room temperature for additional 5 h. After removing the
solvent under reduced pressure the solid residue was washed with
dichloromethane yielding a brown powder. Total yield: 1.15 g
(78 %). C28H20N4O7V2 (626.38): calcd. C 53.69, H 3.22, N 8.94;
found C 53.83, H 3.17, N 8.81 %.
1
trophotometers. Ϫ H and 13C NMR spectra were recorded on a
Bruker AC250 and the 51V NMR spectra on a Bruker DRX500
spectrometer. Chemical shifts in ppm are reported as δ downfield
from the standards, tetramethylsilane (1H and 13C) and VOCl3
(51V).
Synthesis of NH4[VO2(salhyph)]: To a solution of H2salhyph
(9.61 g, 40 mmol) in 50 ml DMF was added NH4VO3 (4.68 g,
40 mmol). The resulting mixture was heated to 90 °C for 4 h. After
cooling to room temperature the mixture was filtrated and the re-
sulting solution reduced in vacuum to about half its original vol-
ume. After standing overnight a crystalline material in form of yel-
low plates can be isolated. Additional material can be obtained
by adding toluene (100 ml) to the DMF solution leading to the
precipitation of a yellow powder which was collected by filtration.
Total yield: 7.70 g (58 %). C14H14N3O4V (339.22): calcd. C 49.57,
H 4.16, N 12.39; found C 49.81, H 4.35, N 12.12 %.
1H NMR ([D7]DMF): δ ϭ 6.79Ϫ6.89 (m, 2H, ph), 7.34Ϫ7.51 (m, 4H, ph),
7.60Ϫ7.64 (m, 1H, ph), 8.11Ϫ8.15 (m, 2H, ph), 9.03 (s, 1H, HCϭN). Ϫ 13C
NMR ([D7]DMF): δ ϭ 117.5, 120.2, 121.0, 128.6, 128.7, 131.0, 133.1, 133.7,
133.9, 156.4 (CϭN), 165.8, 171.1 ppm. Ϫ 51V NMR ([D7]DMF): δ ϭ
Ϫ540 ppm. Ϫ Selected IR data (cmϪ1): ν˜ ϭ 3155 (m, br; NϪH), 1610 (s, br;
CϭNϪNϭC), 918 (s, VO2), 895 (s, VO2). Ϫ UV/Vis (solid state reflection,
νmax in 103 cmϪ1): 35.1, 26.0. Ϫ UV/Vis (DMF solution, νmax in 103 cmϪ1 (ε
in 106 cm2 molϪ1)): 31.2 (14), 24.8 (14).
Selected IR data (cmϪ1): ν˜ ϭ 1605 (s, br; CϭNϪNϭC), 997 (s, VϭO). Ϫ
UV/Vis (solid state reflection, νmax in 103 cmϪ1): 24.6, 16.7 (sh). Ϫ UV/Vis
(CHCl3 solution, νmax in 103 cmϪ1 (ε in 106 cm2 molϪ1)): 31.2 (41), 26.2 (19),
18.5 sh (1).
Synthesis of [VO2(Hsalhyph)] ([VO2(Dsalhyph)]): A suspension of
[V2O3(salhyph)2] (0.21 g) in 15 ml water was heated to reflux for
2 h. The color of the solid changes from brown to yellow. After
cooling to room temperature the insoluble yellow product was iso-
lated by filtration. Total yield: 0.19 g (87 %). The deuterated deriva-
tive [VO2(Dsalhyph)] can be obtained by using D2O as reaction
medium. C14H11N2O4V (322.19): calcd. C 52.19, H 3.44, N 8.69;
found C 51.86, H 3.44, N 8.61 %.
Selected IR data for [VO2(Hsalhyph)] (cmϪ1): ν˜ ϭ 2600 (w, br; NϪH at N2
see Figure 1), 884 (s, br; VO2). Ϫ Selected IR data for [VO2(Dsalhyph)]
(cmϪ1): ν˜ ϭ 1980 (w, br; NϪH at N2 see Figure 2), 901 (s, VO2), 869 (s, VO2).
X-ray Crystallography: The diffraction data of NH4[VO2(salhyph)]
were recorded with ω-scan technique in the 2θ range 5Ϫ52° with a
Siemens R3m/V diffractometer with a graphite monochromator
using molybdenum radiation (λ ϭ 71.073 pm). The crystallographic
data for NH4[VO2(salhyph)] is summarized in Table 2. The final
unit-cell parameters were obtained by least-squares fitting of the
setting angles of 30 reflections with 2θ between 17° and 30°. Lo-
Synthesis of [VO(OMe)(salhyph)(HOMe)]: NH4VO3 (2.92 g,
25 mmol) was added to a solution of H2salhyph (6.01 g, 25 mmol)
in 250 ml methanol. The resulting mixture was heated to reflux for
ca. 2 h until all solid is dissolved. After reducing the volume of the
Z. Anorg. Allg. Chem. 2003, 629, 65Ϫ70
69

W. Plass, H.-P. Yozgatli
rentz and polarization corrections as well as an absorption correc-
tion based on azimuthal ψ scans were applied to the diffraction
data. The structure was solved by direct methods (SHELXTL) and
subsequent full-matrix least square refinement. The refinement af-
forded a Flack parameter [25] of 0.01(4). All non-hydrogen atoms
were refined by using anisotropic thermal parameters. All hydrogen
atoms bound to carbon atoms were located from Fourier-difference
map and refined including their isotropic displacement parameters.
The hydrogen atoms of the ammonium ion were refined with their
isotropic displacement parameters fixed at 1.5 times the value of
the nitrogen atom attached. In addition the NϪH bonds and H···H
interatomic distances within the ammonium ion were restricted in
order to reproduce a tetrahedral geometry.
[5] K. Ishikawa, Y. Mihara, K. Gondoh, E. Suzuki, Y. Asano,
EMBO J. 2000, 19, 2412.
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Structures, Springer-Verlag, Berlin, 1991.
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96, 2239.
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[9] A. Messerschmidt, R. Wever, Proc. Natl. Acad. Sci. USA 1996,
93, 392.
[10] A. Messerschmidt, L. Prade, R. Wever, Biol. Chem. 1997,
378, 309.
[11] A. Messerschmidt, R. Wever, Inorg. Chim. Acta 1998, 273, 160.
[12] M. Weyand, H.-J. Hecht, M. Kieß, M.-F. Liaud, H. Vilter, D.
Schomburg, J. Mol. Biol. 1999, 293, 595.
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be, G. N. Murshudov, J. A. Littlechild, J. Mol. Biol. 2000,
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80, 181.
Crystallographic data for the structure reported in this paper have
been deposited with the Cambridge Crystallographic Data Centre
as supplementary publication no. CCDC-130813. Copies of the
data can be obtained free of charge on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (fax: (ϩ44)1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk).
Acknowledgements. The support of the Deutsche Forschungsge-
meinschaft and the Fonds der Chemischen Industrie is gratefully
acknowledged.
[19] L. El Sayed, M. F. Iskander, J. Inorg. Nucl. Chem. 1971, 33,
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